Molybdenum Imido Alkylidene Metathesis Catalysts that Contain Electron Withdrawing Biphenolates or Binaphtholates

Abstract

We have prepared new Mo(NR)(CHCMe₂Ph)(diolate) complexes (R = 2,6-i-Pr₂C₆H₃, 2,6-Me₂C₆H₃, 1-Adamantyl, or 2-CF₃C₆H₄) that contain relatively electron-withdrawing binaphtholate (3,3′-bis-(9-anthracenyl), 3,3′-bispentafluorophenyl, or 3,3′-bis(3,5-bis(trifluoromethyl)phenyl) or biphenolate (3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-1,1′-biphenyl-2,2′-diolate) ligands. We also have prepared new monomeric Mo(NR)(CHCMe₂Ph)(2,5-dimethylpyrrolide)₂ complexes and have treated them with biphenols or binaphthols in order to prepare several Mo(NR)(CHCMe₂Ph)(diolate) species. In one case the new Mo(NR)(CHCMe₂Ph)(diolate) complexes could be prepared only through reaction of a binaphthol [3,3′-bis(pentafluorophenyl)binaphthol] with a bis(2,5-dimethylpyrrolide) complex. The pyrrolide approach can be employed either to isolate catalysts on a preparative scale or to generate catalysts in situ. Several simple preliminary ring-closing metathesis reactions show that the new complexes are catalytically competent.

INTRODUCTION

Complexes of the type M(NR)(CHR′)(OR″)₂ or M(NR)(CHR′)(diolate) (M = Mo or W) are established well-defined high oxidation state olefin metathesis catalysts¹ whose overall efficiencies depend dramatically upon the electronic and steric characteristics of the NR and OR′ or diolate groups. Operationally the most reactive M(NR)(CHR′)(OR″)₂ catalysts have been those with relatively strong electron withdrawing alkoxides (e.g., hexafluoro-t-butoxide) and sterically protected arylimido ligands (e.g., N-2,6-i -Pr₂C₆H₃). Catalysts that contain an enantiomerically pure diolate have been employed in a variety of asymmetric metathesis reactions in the last several years; examples are shown in Figure 1.^1a Designing new homogeneous metathesis catalysts in the asymmetric family that contain new imido and alkoxide (or diolate) groups is a priority. Therefore, we decided to explore the possibility of preparing M(NR)(CHR′)(diolate) catalysts in which the biphenolate or binaphtholate ligands are more electron withdrawing than those employed so far. In this paper we report several examples of newM(NR)(CHR′)(diolate) complexes of this type. In several cases syntheses involve addition of the biphenol or binaphthol to new, monomeric, bis(2,5-dimethylpyrrolide) complexes. The bis(2,5-dimethylpyrrolide) species should be compared with dimeric bispyrrolide species reported recently.² The use of bispyrrolide species as catalyst precursors avoids complications³ in traditional catalyst syntheses in which triflate ligands are displaced by biphenolates or binaphtholates. In at least one synthesis reported here the bispyrrolide approach was the only one that was successful.

Figure 1.

Examples of asymmetric molybdenum-based olefin metathesis catalysts.

RESULTS AND DISCUSSION

Synthesis of electron withdrawing binaphthols and biphenols

The commercial availability of enantiopure binaphthol (BINOL) makes BINOL derivatives substituted in the 3 and 3′ positions an attractive class of enantiomerically pure diolate ligands.⁴ The first ligand examined was a BINOL derivative with a 9-anthracenyl substituent in the 3 and 3′ positions. The 9-anthracenyl group combines a significant electron-withdrawing ability with significant steric bulk. In addition, we expected the low solubility of the ligand and catalysts that contain the ligand to facilitate isolation of Mo catalysts. Suzuki coupling of the known 3,3′-diiodo-2,2′-dimethoxy-l-binaphthyl⁵ (A) and 9-anthracenyl-boronic acid (B),⁶ followed by deprotection of the crude product using BBr₃ in CH₂Cl₂ afforded (R)-3,3′-bis-9-anthracenyl-BINOL (H₂[Binaph_Anth]) (Scheme 1). (All BINOL derivatives in this paper are enantiomerically pure and have the R configuration.) H₂ [Binaph_Anth] has been claimed in a patent, ⁷ but no experimental details were provided.

Scheme 1.

Synthesis of (R)-3,3′-bis-9-anthracenyl-BINOL (H₂[Binaph_Anth]).

The second ligand examined was a 3,3′-bis(pentafluorophenyl)-BINOL, (H₂[Binaph_C6F5]). Kumada- or Suzuki-type couplings are not applicable for the coupling reaction in this case since ipso-substitution on the electron-deficient aromatic system takes place instead. Therefore, we turned to fluoroborates as coupling partners in similar coupling reactions.⁸ The coupling of potassium trifluoro(pentafluorophenyl)borate (C) with 3,3′-diiodo-2,2′-dimethoxy-binaphthyl catalyzed by palladium acetate in the presence of triphenyl phosphine afforded the desired H₂[Binaph_C6F5] in 52% overall yield (Scheme 2). A report of the synthesis of this species appeared after we had completed our synthesis,⁹ but no experimental details were provided.

Scheme 2.

Synthesis of (R)-3,3′-bis(pentafluorophenyl)-BINOL (H₂[Binaph_C6F5]).

The third BINOL derivative that we chose was 3,3′-bis(3,5-bis(trifluoromethyl)phenyl)-BINOL, H₂[Binaph_CF3].¹⁰ Commercially available bromo-3,5-bis(trifluoromethyl)benzene (E) was treated with 2,2′-dimethoxy-binaphthalene-3,3′-diboronic acid (D) under standard Suzuki conditions and deprotected in situ to give the desired ligand in 56% overall yield (Scheme 3). It was identical to the reported compound, which was prepared using a slightly different procedure.

Scheme 3.

Synthesis of (R)-3,3′-bis(3,5-bis(trifluoromethyl)phenyl)-BINOL (H₂[Binaph_CF3]).

A ligand that has yielded highly successful catalysts in ring-closing metathesis desymmetrizations has been the 3,3′-di-tert-butyl-5,5′,6,6′-tetramethyl-l,1′-biphenyl-2,2′-diolate ([Biphen]²⁻) ligand. The synthesis of a related ligand having a trifluoromethyl group in the 5 and 5′ positions would provide the opportunity to study a significant electronic variation of the [Biphen]²⁻) ligand with minimal change in the steric demands of the ligand. The synthesis of 3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-1,1′-biphenyl-2,2′-diol (H₂[Biphen_CF3]) is depicted in Scheme 4. (The [Biphen_CF3]²⁻ ligand is racemic in all procedures reported here.) The reaction between tert-butyl-m -cresol and di-tert-butyl peroxide afforded 3,3′-bis(tert-butyl)-6,6′-dimethyl-biphenol (G), which was oxidized to the corresponding diquinone (H) using an excess of mCPBA. Treatment of H with Me₃SiCF₃ in DMF following a published procedure¹¹ produced the protected semiquinone (I). Upon treatment of I with amalgamated aluminum in a mixture of THF and water, 3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-l,1′-biphenyl-2,2′-diol (H₂[Biphen_CF3]) was obtained in 70% yield.

Scheme 4.

Synthesis of rac-3,3′-di-tert-butyl-5,5′-bistrifluoromethyl-6,6′-dimethyl-1,1′-biphenyl-2,2′-diol(H₂[Biphen_CF3]).

Synthesis of 2,5-dimethylpyrrolide complexes

We recently reported new [Mo(NR)(CHCMe₂R′)(C₄H₄N)₂]₂ species, and noted that they react readily with various monoalcohols, binaphthols, and biphenols to yield Mo(NR)(CHCMe₂R′)(OR″)₂ or Mo(NR)(CHCMe₂R′)(diolate) complexes.² Preliminary experiments suggested that this method is a mild way to prepare a variety of catalysts from a single precursor through addition of a diol. However, the fact that two equivalents of pyrrole are generated in the process leaves open the possibility that pyrrole may bind to the metal in the catalyst in question (although one might expect that it might be a relatively poor ligand) or otherwise complicate a subsequent metathesis reaction. Therefore, we became curious about the possibility of preparing what we expected would be monomeric 2,5-dimethylpyrrolide analogs and whether they too would serve as precursors to binaphtholate and biphenolate catalysts.

Addition of two equivalents of lithium 2,5-dimethylpyrrolide to a diethyl ether solution of Mo(NR)(CHCMe₂Ph)(OTf)₂(DME) [R = 2,6-i-Pr₂C₆H₃ (Ar), 2,6-Me₂C₆H₃ (Ar′), 1-adamantyl (Ad), or 2-(CF₃)C₆H₄ (Ar_F)] produced Mo(NR)(CHCMe₂Ph)(2,5-Me₂NC₄H₂)₂ complexes in > 80% yield (equation 1). Proton ¹H NMR spectra of 1a – 1d in C₆D₆ contain sharp alkylidene resonances at 13.30 ppm (1a), 13.19 ppm (1b), 12.94 ppm (1c), and 13.19 ppm (1d), but broad pyrrolide resonances at room temperature. At − 80 °C, resonances were observed consistent with a molecule with no symmetry (two different pyrrolides) and a non-rotating diisopropyimido group; only one alkylidene resonance is observed. (See Supporting Information for variable temperature NMR spectra.) We propose that the lowest energy species at this temperature is one in which one of the 2,5-pyrrolide ligands is bound in an η⁵ fashion and the other is bound in an η¹ fashion, as shown in equation 1. The solid state structure of a related tungsten complex, W(NAr)(CHCMe₃)(2,5-Me₂NC₄H₂)₂, ¹² shows it to have this structure. Carbon NMR spectra reveal alkylidene carbon resonances characteristic of syn isomers (J_CH = 120 Hz). We propose that at room temperature mirror symmetric Mo(NAr)(CHCMe₂Ph)(η¹-2,5-Me₂NC₄H₂)₂ is formed, which equilibrates the inequivalent pyrrolide ligands. Complexes 1a – 1d should be compared with the recently reported pseudotetrahedral bis(diphenylamido) species.¹³

(1)

Synthesis of complexes that contain N-2,6-i-Pr₂C₆H₃ (NAr), N-2,6-Me₂C₆H₃ (NAr′), N(1-adamantyl) (NAd), or N-2-(CF₃)C₆H₄ (NAr_F) ligands

Salt metathesis reactions involving the reaction between the dilithium salt of the ligands (generated in situ through deprotonation of the ligands with n-BuLi in THF) and Mo(NR)(CHCMe₂Ph)(OTf)₂(DME) (R = Ar, Ar′, Ad, Ar_F) in THF failed due to ligand decomposition (for H₂[Binaph_Anth]), formation of undesired products (for H₂[Binaph_C6F5]) and poor and inconsistent yields (for H₂[Biphen_CF3]). Therefore a related, but milder route that employs triethylamine as a base was pursued.

Mo(NAr)(CHCMe₂Ph)(Binaph_Anth)(THF) (2a; Ar = 2,6-i-Pr₂C₆H₃) was synthesized in 90% yield through the reaction of Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) with H₂[Binaph_Anth] in the presence often equivalents of triethylamine in THF (equation 2). The ¹H NMR spectrum of 2a in C₆D₆ revealed two broad resonances at δ 13.21 ppm (80%) and 11.70 ppm (20%), which

(2)

are assigned to anti and syn alkylidene isomers, respectively. The resonances are broad as a consequence of THF dissociation from the metal. In the presence of 10 equivalents of THF sharp H_α resonances were observed at δ 13.20 ppm and 12.34 ppm. Binding of THF to the metal is characteristic of binaphtholate compounds of this general type.^1a The ¹H NMR spectrum of 2a in CD₂Cl₂ displayed sharp resonances for both syn (δ 11.95 ppm, J_CH = 117 Hz) and anti (δ12.89 ppm, J_CH = 145 Hz) isomers in the ratio of 85(anti):15(syn). Mo(NR)(CHCMe₂Ph)(Binaph_Anth)(THF) compounds, where R = Ar′ (2b, 84%) or Ad (2c, 92%), were synthesized in a manner analogous to that described for 2a (equation 2). Efforts to synthesize Mo[N-2-(CF₃)C₆H₄](CHCMe₂Ph)(Binaph_Anth)(THF) (2d) in a similar manner resulted in formation of unknown products having multiple alkylidene resonances in their ¹H NMR spectra; apparently, therefore, 2d could not be prepared using the method shown in equation 2.

Attempts to generate THF-free versions of 2a – 2d (2a′ – 2d′) in a reaction between H₂[Binaph_Anth] and 1a – 1d in C₆D₆ resulted in < 20% conversion after 12 h. Likewise, [Mo(NAr)(CHCMe₂Ph)(C₄H₄N)₂]₂ ² did not react readily and cleanly with H₂[Binaph_Anth] in C₆D₆. We ascribed these slow reactions to the sterically demanding characteristics of the [Binaph_Anth]²⁻ ligand.

Single crystals of 2a suitable for X-ray crystallography were obtained by slow diffusion of pentane into a THF solution at − 30 °C (see Figure 2 and Table 1). The overall structure of 2a is a trigonal bipyramid with the THF bound to a CNO face of the tetrahedral Mo(NAr)(CHCMe₃)(Binaph_Anth) core. This is the most often observed geometry of base adducts of this type.¹ The alkylidene displays an anti configuration with respect to the imido ligand, which is consistent with the observed room temperature ¹H NMR spectrum in C₆D₆. The dihedral angle between the anthracenyl and the binaphthyl planes is 68.5°. All bond angles and bond distances observed are similar to bond angles and distances in other five-coordinate complexes of this type (see caption to Figure 2).¹⁴

Figure 2.

POV-ray diagram of Mo(NAr)(CHCMe₂Ph)(Binaph_Anth)(THF) (2a). Thermal ellipsoids are displayed at 50% probability level. Hydrogen atoms and cocrystallized THF molecules are omitted for clarity; Mo(1)-N(1) = 1.736(3), Mo(1)-C(1) = 1.941(4) Å, Mo(1)-O(2) = 1.994(2) Å, Mo(1)-O(1) = 2.025(2) Å, Mo(1)-O(1S) = 2.235(2) Å, N(1)-Mo(1)-C(1) = 96.94(18) °, N(1)-Mo(1)-O(2) = 131.98(12) °, C(1)-Mo(1)-O(2) = 128.22(16) °, N(1)-Mo(1)-O(1) = 102.22(11) °, C(1)-Mo(1)-O(1) = 96.02(14) °, O(2)-Mo(1)-O(1) = 89.74(9) °, N(1)-Mo(1)-O(1S) = 85.39(11) °, C(1)-Mo(1)-O(1S) = 91.30(14) °, O(2)-Mo(1)-O(1S) = 78.95(9) °, O(1)-Mo(1)-O(1S) = 168.68(9) °, C(2)-C(1)-Mo(1) = 125.7(4) °, C(11)-N(1)-Mo(1) = 159.8(2).

Table 1.

Crystal data and structure refinement for (R)-Mo(NAr)(CHCMe₂Ph)(Binaph_Anth)(THF) (06240) and rac-Mo(NAd)(CHCMe₂Ph)(Biphen_CF3)(THF) (06180).

	06240	06180
empirical formula	C88.60H94.18MoNO6.65	C48H61F6MoNO3
formula weight	1375.31	909.92 g/mol
crystal system	Monoclinic	triclinic
space group	P2(1)	P1̄
unit cell dimensions	a = 12.245(3) Å	a =12.7386(14) Å
	b = 15.001(4) Å	b= 12.9783(16) Å
	c = 19.710(5) Å	c= 15.7794(19) Å
	α = 90°	α = 76.012(4)°
	β = 93.793(4)°	β = 80.948(3)°
	γ = 90°	γ = 61.683(3)°
volume	3612.5(15) Å3	2225.7(5) Å3
z	2	2
Density (calculated)	1.264g/cm3	1.358g/cm3
absorption coefficient	0.239mm−1	0.361 mm−1
F(000)	1456	952
crystal size	0.25×0. 15×0. 15 mm3	0.30×0.25×0.05 mm3
Θ range for data collection	1.71 to 29.08°	1.33 to 29.57°
index ranges	−16 ≤ h ≤ l6,	−17 ≤ h ≤ 17,
	−20 ≤ k ≤ 20, −26 ≤ 1 ≤ 26	−17 ≤ k ≤ l8,0 ≤ l ≤ 21
reflections collected	78198	15550
independent reflections	19293 [R(int) = 0.0721]	15550b
completeness to theta = 29.08°	100.0 %	99.8 %
max. and min. transmission	0.965 land 0.9427	0.9822 and 0.8994
data/restraints/parameters	19293/1155/1066	15550/1629/856
goodness-of-fit on F2	1.036	1.026
final R indices [I>2sigma(I)]	R1 = 0.0461	R1 = 0.0403
	wR2 = 0.1203	wR2 = 0.0906
R indices (all data)	R1 = 0.0551	R1 = 0.0505
	wR2 = 0.1263	wR2 = 0.0942
largest diff. peak and hole	0.768 and −0.825 e. Å−3	0.872 and −0.308 e. Å−3

^aIn each case the temperature was 100(2) K, the wavelength was 0.71073 Å, the absorption correction was semi-empirical from equivalents, and the refinement method was full-matrix least-squares on F².

^bNon-merohedral twin.

Efforts to prepare 3a – 3d (equation 3) in a reaction between H₂[Biphen_C6F5] and Mo(NR)(CHCMe₂Ph)(OTf)₂(DME) [R = Ar, Ar′, Ad and Ar_F] in the presence of ten equivalents of triethylamine in THF were not successful. The presence of doublet resonances in the alkylidene region was suggestive of some side reaction that resulted in coupling of an alkylidene proton to fluorine. However, complexes 3a – 3d could be prepared in >84% yield as THF adducts in reactions between the bispyrrolide complexes (1a – 1d) and one equivalent of H₂[BinaphC₆F₅] in THF (equation 3). The ¹H NMR spectra of 3a, 3b, and 3c contain alkylidene resonances only for anti isomers in C₆D₆, which were assigned on the basis of their large J_CH (> 140 Hz) values. The ¹H NMR spectrum of 3d in C₆D₆ depicted two resonances in the alkylidene

(3)

region at 14.08 ppm (anti, 60%) and 13.36 ppm (syn, 40%), which correlate with ¹³C NMR resonances at 320.4 ppm and 307.1 ppm. Compound 3a should be compared with the previously reported anti(R)-Mo(NAr)(CHCMe₂Ph)(Binaph_Ph)(THF) (δ 13.65 ppm in C₆D₆, J_CH = 150 Hz).¹⁴ The ¹⁹F NMR spectra of these complexes reveal ten aryl fluoride resonances, consistent with pentafluorophenyl groups that do not rotate rapidly at room temperature.

Variable-temperature ¹H NMR spectra of 3a in toluene-d₈ from −80 °C to 90 °C are shown in Figure 3. At 20 °C, only the H_α resonance for the anti isomer (J_CH =146 Hz) is observed at 13.81 ppm. Upon cooling the sample to − 40 °C, only minor new alkylidene resonances (< 5% total) are observed at 13.26 ppm and 12.69 ppm, which are proposed to be two diastereomeric syn THF adducts. Warming the sample to 60 °C generates a broad upfield resonance that is the result of equilibration of syn THF-free and syn-THF adducts on the NMR timescale. The resonance for the anti THF adduct is broad for similar reasons, but does not shift upfield since relatively little THF-free anti isomer is present. At 90 °C broadening of the anti and the syn alkylidene resonances may also result from interconversion of anti and syn isomers through rotation about the Mo=C bond. After heating the sample to 90 °C in the variable temperature experiment, some decomposition of 3a was observed.

Figure 3.

Variable temperature ¹H NMR spectra of Mo(NAr)(CHCMe₂Ph)(Binaph_C6F5)(THF) (3a) in toluene-d₈(500 MHz).

Mo(NAr)(CHCMe₂Ph)(Binaph_CF3)(THF) complexes can be prepared by treating the bispyrrolide precursors 1a – 1d with H₂[Binaph_CF3] in THF (equation 4). For example,

(4)

Mo(NAr)(CHCMe₂Ph)(Binaph_CF3)(THF) (4a) was isolated in 37% yield. The ¹H NMR spectrum of 4a in C₆D₆ revealed alkylidene resonances at 13.77 ppm (J_CH = 140 Hz) for the anti isomer and at 12.23 ppm (5%) for the syn isomer. The presence of only two ¹⁹F resonances for each isomer is the consequence of free rotation of the 3,5-bis(trifluoromethyl)phenyl groups on the NMR timescale at room temperature. Compounds 4b, 4c, and 4d also could be observed to form cleanly in the reaction shown in equation 4. However, none could be isolated from solution. In C₆D₆ essentially one alkylidene resonance was found at 13.79 ppm for 4b, 12.42 ppm for 4c, and 13.91 ppm for 4d. Generation of Binaphcps²⁻ containing complexes through alcoholysis of Mo(NR)(CHCMe₂Ph)(OTf)₂(DME) (R = Ar, Ar,′ Ad and Ar_F) with the ligand in presence of ten equivalents of triethylamine resulted in clean conversion only in the case of the complex containing 1-adamantyl imido ligand (δH_α =13.18 ppm).

THF-free versions of 4a – 4d (4a′–4d′)could be prepared in C₆D₆. The reaction between 1a and H₂[Binaph_CF3] proceeds in 15 minutes to yield “syn-Mo(NAr)(CHCMe₂Ph)(Binaph_CF3)” (4a′ δH_α = 10.86 ppm). The 2,5-dimethylpyrrole resonances in the ¹H NMR spectrum are not shifted from where they are in free 2,5-dimethylpyrrole. This method of in situ catalyst generation also can be employed to prepare Mo(NR)(CHCMe₂Ph)(Binaph_CF3) species 4b′ (R = Ar), 4c′ (R = Ad), and 4d′ (R = Ar_F). Conversion was rapid (< 15 min) in the case of 4b′ and 4c′, but formation of 4d′ required one hour for full conversion at 22 °C at a concentration of 23 mM. Compounds 4a′, 4b′, and 4c′ consisted of mostly the syn isomer (δH_α= 10.86 ppm, 10.86 ppm, and 10.62 ppm, respectively), while 4d′ consisted of approximately an equal ratio of syn (δ 10.66 ppm) and anti (δ 13.71 ppm) isomers. Upon addition of THF (50 μL) to samples of 4a′ – 4d′ in C₆D₆, the THF adducts (4a –4d) are formed immediately.

(5)

Addition of H₂[Biphen_CF3] to a THF solution of Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) in the presence of 10 equivalents of triethylamine yielded rac-Mo(NAr)(CHCMe₂Ph)(Biphen_CF3)(THF) (5a) in 50% yield (equation 5). It should be noted that the analogous Mo(NAr)(CHCMe₂Ph)(Biphen) species does not crystallize with one equivalent of THF bound to the metal.¹⁵ In fact, the only other isolated THF adduct of a [Biphen]²⁻ complex is Mo(N-2,6-Cl₂C₆H₃)(CHCMe₂Ph)(Biphen)(THF), since the N-2,6-Cl₂C₆H₃ ligand creates a more electrophilic metal center.¹⁶ Coordination of THF in 5a is also consistent with a more electrophilic metal center than that in Mo(NAr)(CHCMe₂Ph)(Biphen).

Proton, carbon, and fluorine NMR spectra of 5a in C₆D₆ at 20 °C are all consistent with a 70:30 mixture of syn and anti isomers being present. Temperature dependent behavior of proton NMR spectra analogous to that for 3a and a variety of previous biphenolate or binaphtholate complexes explored to date are observed (Figure 4).¹⁷ Interestingly, at −60 °C four alkylidene proton resonances are observed for what we propose are four diastereomeric THF adducts of 5a. During the entire cooling and heating of the sample, no decomposition of 5a was observed.

Figure 4.

Variable temperature ¹H NMR spectra of Mo(NAr)(CHCMe₂Ph)(Biphen_CF3)(THF) (5a) in toluene-d₈ (500 MHz).

Single crystals of 5c suitable for X-ray crystallography were grown from a diethyl ether solution at −30 °C (Table 2 and Figure 5). The overall structure is analogous to that shown in Figure 2 and all bond angles and bond distances observed are typical for five-coordinate complexes of this type (see caption to Figure 5).¹⁶

Figure 5.

POV-ray diagram of Mo(NAd)(CHCMe₂Ph)(Biphen_CF3)(THF) (5c). Thermal ellipsoids are displayed at 50% probability level. Hydrogen atoms are omitted for clarity; Mo-C(1) = 1.8825(19) Å, Mo-N(1) = 1.7280(16) Å, Mo-O(1) = 1.987(2) Å, Mo-O(2) = 2.027(2) Å, Mo-O(1T) = 2.2206(13) Å, Mo-C(1)-C(2) = 146.73(15)°, Mo-N(1)-C(11) = 162.04(13)°, C(1)-Mo-N(1) = 105.19(8)°, C(1)-Mo-O(1) = 109.13(14)°, C(1)-Mo-O(2) = 102.14(17)°, N(1)-Mo-O(1T) = 92.62(6)°, N(1)-Mo-O(1) = 144.54(14)°, N(1)-Mo-O(2) = 95.06(12)°, N(1)-Mo-O(1T) = 92.62(6)°, O(1)-Mo-O(2) = 86.35(14)°, O(1)-Mo-O(1T) = 78.15(12)°, O(2)-Mo-O(1T) = 162.21(17)°.

Mo(NR)(CHCMe₂Ph)(Biphen_CF3)(THF) complexes (R = Ar′ (5b) or R = Ad (5c); equation 5) were prepared in a manner analogous to the synthesis of 5a. The ¹H NMR spectrum of 5b in C₆D₆ showed it to be a mixture of anti (14.10 ppm, J_CH =146 Hz, ~75%) and syn isomers (12.41 ppm, J_CH = 117 Hz, ~ 25 %). The ¹H NMR spectrum of 5c in C₆D₆ revealed only one broad alkylidene resonance at 12.14 ppm.

Reactions between 1a – 1c and H₂[Biphen_CF3] showed <10% conversion at room temperature in 12 h in C₆D₆ at concentrations of ~ 0.25 M. Upon heating the samples to 70 °C complete conversion to compounds having a single alkylidene (5a′ δH_α = 11.33 ppm; 5b′ δH_α = 11.28 ppm; 5c′ δH_α = 11.18 ppm) was achieved in 18 h. (The rates of conversion were similar when the reaction was performed in CD₂Cl₂.) Upon addition of one or more equivalents of THF to samples of 5a′, 5b′, and 5c′, primarily one alkylidene resonance was observed for 5a at 14.24 ppm, 5b at 14.34 ppm, and 5c at 12.26 ppm, respectively. (These chemical shifts depend slightly upon how many equivalents of THF is added.) A reaction between Mo(NAr_F)(CHCMe₂Ph)(OTf)₂(DME) and H₂[Biphen_CF3] in presence of ten equivalents of triethylamine in C₆D₆ showed clean conversion to THF-free “Mo(NAr_F)(CHCMe₂Ph)(Biphen_CF3)” (5d′; δH_α = 12.86 ppm), although attempts to isolate this species as a solid also were not successful.

Preliminary metathesis reactions

Ring-closing metatheses of diallylether were carried out in C₆D₆ with ~ 4% catalyst loading (14 mM) and product yield was determined through ¹H NMR studies. (See experimental section for details.) Of the compounds examined (2a – 2c, 3a – 3d, 4a, 5a – 5c), only Biphen_CF3²⁻ complexes (5) were successful. In 15 min 5a afforded the ring-closed product, dihydrofuran, in essentially 100% yield, while 5b and 5c yielded 80% and 50% ring-closed product, respectively, in the same time period. No BINOL-based catalyst (2, 3, or 4) produced any significant amount of product (< 1% based on ¹H NMR) in 12 h, even though resonances for the first metathesis product (3,3-dimethyl-3-phenyl-1-propene) were observed in ¹H NMR spectra. No product was observed upon heating reactions to 60 °C.

In contrast, diallyltosylamine can be ring-closed with BINOL-based catalysts to yield the product in good yields. Catalysts 2a, 2b and 2c produced 15%, 65%, and 6% product after 15 min, and 90%, 100% and 50%, respectively, at 40 °C in 3 h. Catalyst 3a completely ring-closed diallyltosylamine in 3 h, while 3b – 3d produced 86%, 29% and 25%, respectively, of the ring-closed product after 3 h. Interestingly, “in situ” catalysts 4a′ – 4d′ in C₆D₆ produced 77%, 60%, 43%, and 20%, respectively, of the ring-closed product in 15 min. Therefore we can conclude that 2,5-dimethylpyrrole that is liberated in reactions between 1a – 1d and H₂[Binaph_CF3] does not block metathesis activity.

We ascribe the inability of BINOL-based catalysts to ring-close diallyether to coordination of the oxygen atom of the ring-closed product to the more accessible metal center, thereby slowing metathesis significantly. The ether oxygen can coordinate in either diallylether itself, or in a Mo=CHCH₂OCH₂CHCH₂ intermediate. The biphenolate-based diols provide more steric hinderance at the metal center compared to the BINOL-based diols, which could be the reason for complete ring-closing metathesis of diallylether by 5a. In the case of diallyltosylamine, the nitrogen does not coordinate strongly enough to inhibit metathesis to any significant degree.

In depth evaluations of both isolated and in situ generated new catalysts will be reported in future publications.

CONCLUSIONS

We have shown that new Mo(NR)(CHCMe₂Ph)(diolate) complexes can be prepared that contain relatively electron-withdrawing biphenolate or binaphtholate ligands. New Mo(NR)(CHCMe₂Ph)(2,5-Me₂NC₄H₂)₂ complexes also can be prepared in excellent yields and can serve as precursors to several of the new catalysts upon addition of the diol. In fact, new Mo(NR)(CHCMe₂Ph)[3,3′-bis(pentafluorophenyl)binaphtholate] complexes could be prepared and isolated only through reactions between 3,3′-bis(pentafluorophenyl)binaphthol and bispyrrolide complexes. Several simple preliminary ring-closing metathesis reactions show that the new catalysts are catalytically competent. It has also been demonstrated that the 2,5-dimethylpyrrole that is liberated when [Binaph_CF3]²⁻ catalysts are prepared in situ does not inhibit metathesis activity.

EXPERIMENTAL

General Comments

All manipulations were conducted under a nitrogen atmosphere in a Nitrogen Atmospheres drybox or using Schlenk techniques. All glassware was oven-dried prior to use. Ether, pentane, toluene, dichloromethane, toluene and benzene were degassed with dinitrogen and passed through activated alumina columns. Dimethoxyethane was distilled in vacuo from a dark purple solution of sodium benzophenone ketyl, and degassed three times through freeze-pump-thaw techniques. All dried and deoxygenated solvents were stored over molecular sieves in a nitrogen-filled glovebox.

C₆D₆, CD₂Cl₂, and C₆D₅CD₃ were dried over 4 Å Linde-type molecular sieves. CDCl₃ was used as received. NMR spectra were recorded on a Varian 300 MHz or 500 MHz spectrometers at room temperature unless otherwise noted. Chemical shifts for ¹H and ¹³C spectra were referenced to the residual ¹H/¹³C resonances of the deuterated solvent (¹H: CDCl₃, δ 7.26; C₆D₆, δ 7.16; CD₂Cl₂, δ 5.32; C₆D₅CD₃, δ 2.01 (methyl); ¹³C: CDCl₃, δ 77.23; C₆D₆, δ 128.39; CD₂Cl₂, δ 54.00) and are reported as parts per million relative to tetramethylsilane. Following abbreviations refer to the multiplicity: s = singlet, d = doublet, t = triplet, sept = septet, q = quartet, m = multiplet, br = broad signal. Elemental Analyses were performed by H. Kolbe Mikroanalytisches Laboratorium, Mülheim an der Ruhr, Germany.

Evaporation of organic solutions was carried out through rotary evaporation on a water bath below 40 °C. Product purification by flash column chromatography was accomplished using silica gel 60 (32–63 μm particle size from EMD chemicals) at 0.1 – 0.3 bar pressure. Thin-layer chromatography (TLC) was performed on Merck silica gel 60 F₂₅₄ glass plates. Visualization was achieved by either fluorescence quenching or by staining with aqueous potassium permanganate solution.

Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME), Mo(NAr′)(CHCMe₂Ph)(OTf)₂(DME), Mo(NAd)(CHCMe₂Ph)(OTf)₂(DME) and Mo(NAr_F)(CHCMe₂Ph)(OTf)₂(DME) were prepared as described in the literature.¹⁸ Li-2,5-Me₂NC₄H₂ was prepared by treating the respective pyrrole with Li-n-Bu in diethylether. 2,5-Dimethylpyrrole was purchased from Aldrich. All binaphthols in syntheses below have the R configuation; all biphenols are racemic.

X-ray Crystallography

Low temperature diffraction data were collected on a Siemens Platform three-circle diffractometer coupled to a Bruker-AXS Smart Apex CCD detector with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å), performing φ and ω-scans. All structures were solved by direct methods using SHELXS,¹⁹ and refined against F² on all data by full-matrix least squares with SHELXL-97.²⁰ All non-hydrogen atoms, were refined anisotropically. Except for the hydrogen atoms on carbon atoms binding directly to molybdenum, which have been taken from the difference Fourier synthesis and refined semi-freely with the help of distance restraints, all hydrogen atoms were included in the model at geometrically calculated positions and refined using a riding model. The isotropic displacement parameters of all hydrogen atoms were fixed to 1.2 times the U value of the atoms to which they are linked (1.5 times for methyl groups). Details of the data quality and a summary of the residual values of the refinements are listed in Table 1.

Compound 2a crystallizes in the monoclinic space group P2₁ with one molecule in the asymmetric unit. The entire alkylidene ligand shows disorder over two positions. Again, the atomic positions of the two components of the disorder were found to be relatively close to one another, suggesting flexibility in coordination geometry rather than two alternative conformations. The disorder was refined with the help of similarity restraints on 1–2 and 1–3 distances and displacement parameters as well as rigid bond restraints for anisotropic displacement parameters. The ratio was refined freely, while the total occupancies of both components were constrained to unity; the occupancies of the main component converged at 0.781(7). Including the THF molecule coordinating to the molybdenum atom, the molecule co-crystallized with five crystallographically independent molecules of THF, all of which show at least some disorder. One of the THF molecules is only partially occupied and collides with the minor component of a fully occupied, but nevertheless disordered, THF molecule. Therefore the occupancy of the partially occupied THF molecule was coupled to that of the major component of the one creating the collision. A second component for the partially occupied molecule could not be found. Consequently non-integer values for the elements C, H, and O in the calculated empirical formula of the structure of 2a result.

Complex 5c crystallizes in the triclinic space group P1̄ with one molecule in the asymmetric unit. Both the coordinated THF and the [Biphen_CF3]²⁻ ligand show disorder. The atomic positions of the two components of the disorders are relatively close to one another, suggesting that the disorder can be understood as flexibility in coordination geometry rather than as two alternative conformations. The disorders were refined with the help of similarity restraints on 1–2 and 1–3 distances and displacement parameters as well as rigid bond restraints for anisotropic displacement parameters. The ratios were refined freely, while constraining the total occupancy of both components to unity; the occupancies of the main components converged at 0.806(8) for the [Biphen_CF3]²⁻ ligand and 0.849(7) for the THF. In addition to challenges arising from the disorders, the crystal on which this analysis is based was non-merohedrally twinned. Two independent orientation matrices for the unit cell were found using the program CELL_NOW,²¹ and data reduction taking into account the twinning was performed with SAINT.²² The program TWINABS²³ was used to perform absorption correction and to set up the HKLF5 format file for structure refinement. The twin ratio was refined freely and converged at a value of 0.2143(5). To counteract correlation effects between otherwise uncorrelated parameters that could be traced to twinning, mild similarity restraints on displacement parameters as well as rigid bond restraints for anisotropic displacement parameters were applied to all atoms in the structure. Non-merohedral twinning results in a partial overlap of some reflections in a way that is not related to the Laue symmetry of the crystal. Therefore symmetry equivalent reflections must not be merged and it impossible to calculate a merging R-value. Consequently a merging R-value is not listed in Table 1.

3,3′-Bis-(9-anthracenyl)-BINOL (H₂[Binaph_Anth])

In a 100 mL pressure flask 3,3′-diiodo-2,2′-dimethoxy-1-binapthyl (A) (2.15 g, 3.81 mmol) and 9-anthracenyl-boronic acid²⁴ (B) (3.50 g, 15.8 mmol) were suspended in a mixture of toluene (30 mL), ethanol (15 mL) and aqueous Na₂CO₃ solution (2 M, 15 mL). The suspension was purged with nitrogen for 30 min, tetrakis(triphenylphosphine)palladium (441 mg, 0.381 mmol) was added, and the mixture was heated to 90 °C for 14 h. After cooling the mixture to room temperature it was filtered and dichloromethane and water were added to the filtrate. The reaction mixture over MgSO₄ and the solvent was removed in vacuo. The residue was dissolved in methylene chloride (50 mL) and boron tribromide (1.0 M in CH₂Cl₂, 10 mL, 10 mmol) was added. After stirring the mixture for 12 h at 22 °C, it was cooled to 0 °C and water was added. The mixture was extracted with dichloromethane, the dichloromethane solution was dried over MgSO₄, and the solvent was evaporated. Flash column chromatography (silica gel, toluene/hexane/ethyl acetate 25:25:1) gave 3,3′-bis-(9)-anthracenyl-BINOL H₂[Binaph_Anth] as an off-white solid (1.68 g, 66%): ¹H NMR (CDCl₃, 300 MHz) δ 8.24 (s, 2, Ar), 8.03 (m, 2, Ar) 7.86 (m, 2, Ar), 7.80 (d, J= 8.3 Hz, Ar), 7.63–7.75 (m, 8, Ar), 7.10–7.30 (m, 12, Ar), 6.94 (m, 2, Ar), 5.10 (s, 2, OH); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 151.0, 133.9, 133.0, 131.4, 131.4, 130.8, 130.7, 130.7, 129.2, 128.9, 128.5, 128.4, 128.3, 127.8, 127.4, 127.1, 126.2, 126.1, 126.1, 126.1, 125.3, 124.8, 124.2, 113.4; IR (thin film) ν = 3530, 3051, 1623, 1497, 1436, 1246, 1147, 905, 729 cm⁻¹; HRMS (EI, [M + Na]) Calcd for C₄₈H₃₀O₂Na: 661.2138. Found: 661.2159.

3,3′-Bis(pentafluorophenyl)-BINOL (H₂[Binaph_C6F5])

In a 100 mL pressure flask 3,3′-diiodo-2,2′-dimethoxy-1-binapthyl (A) (3.36 g, 5.93 mmol), potassium (pentafluorophenyl)trifluoro borate (6.50 g, 23.7 mmol), palladium acetate (220 mg, 1.00 mmol), triphenylphosphine (520 mg, 2.00 mmol), silver oxide (5.50 g, 23.7 mmol), and potassium carbonate (5.45 g, 39.5 mmol) were suspended in toluene (50 mL) and the mixture was heated to 110 °C for 48 h. The mixture was filtered and water was added. The mixture was extracted with chloroform. The chloroform solution was separated and dried over MgSO₄ and the solvent was evaporated in vacuo. The residue was dissolved in methylene chloride (100 mL) and boron tribromide (1 M in CH₂Cl₂, 20.0 mL, 20.0 mmol) added at 0 °C. The mixture was stirred for 14 h. Water was added at 0 °C and the mixture was extracted with dichloromethane. The dichloromethane solution was separated and dried with MgSO₄ and the solvent was evaporated in vacuo. Flash column chromatography (silica gel, hexane/ethyl acetate 30:1) gave 3,3′-bis(pentafluorophenyl)-BINOL H₂[Binaph_C6F5] as a glassy colorless solid (1.90 g, 52%): ¹H NMR (CDCl₃, 300 MHz,) δ 8.04 (s, 2, Ar), 7.95 (m, 2, Ar), 7.40–7.51 (m, 4, Ar), 7.25 (m, 2, Ar), 5.28 (s, 2 OH); ¹⁹F NMR (CDCl₃, 282 MHz, 23 °C) δ −140.03 (dd, J = 22.2, 8.2 Hz, 2F), −140.51 (dd, 25.0, 8.2 Hz, 2F), −155.16 (t, J= 19.4 Hz, 2F), −162.91 (m, 4F); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 150.4, [146.3 (m), 143.0 (m), 142.7 (m), 139.3 (m), 136.0 (m), C₆F₅], 134.1, 133.6, 129.0, 128.9, 128.8, 125.0, 124.0, 115.7, 111.9 (m, C₆F₅), 111.3; IR (thin film) ν = 3532, 3065, 1625, 1520, 1495, 1443, 1360, 1212, 1047, 989, 906, 735; HRMS (ESI, [M − H]) Calcd for C₃₂H₁₁F₁₀O₂: 617.0594. Found: 617.0603.

3,3′-Bis(3,5-bis(trifluoromethyl)phenyl)-BINOL (H₂[Binaph_CF3])

In a 100 mL pressure flask 2,2′-dimethoxy-1-binapthyl-3,3′-diboronic acid (4.02 g, 10.0 mmol), 3,5-bis(trifluoromethyl)-bromo-benzene (8.79 g, 30.0 mmol), and sodium carbonate (2.65 g, 25.0 mmol) were dissolved in a mixture of dimethoxy ethane (50 mL) and water (12 mL). The solution was purged with nitrogen for 15 min. and tetrakis(triphenylphosphine)-palladium (578 mg, 0.500 mmol) added. The mixture was heated to 95 °C for 36 h. The mixture was cooled to room temperature and filtered. The filtrate was extracted with dichloromethane after addition of water. The dichloromethane layer was dried over MgSO₄ and the solvent was evaporated in vacuo. The residue was dissolved in methylene chloride (50 mL) and boron tribromide (1.0 M in CH₂Cl₂, 30 mL, 30 mmol) was added at room temperature. The mixture was stirred for 6 h, cooled to 0 °C, and water was added. The mixture was extracted with dichloromethane. The dichloromethane layer was dried over MgSO₄, and the solvent evaporated in vacuo. Flash column chromatography (silica gel, hexane/ethyl acetate 30:1) gave 3,3′-bis(3,5-bis(trifluoromethyl)phenyl)-BINOL H₂[Binaph_CF3] as a white solid (4.00 g, 56%): ¹H NMR (CDCl₃, 300 MHz) δ 8.31 (s, 4, Ar) 8.18 (s, 2, Ar), 8.05 (d, J= 7.4 Hz, 2, Ar), 7.98 (s, 2, Ar) 7.42–7.58 9M, 4, Ar), 7.30 (d, J= 8.0 Hz, 2, Ar), 5.45 (br s, 2, OH); ¹⁹F NMR (CDCl₃, 282 MHz, 23 °C) δ −63.1; ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 149.87, 139.47, 133.24, 132.38, 131.57 (q, J= 33.4 Hz), 129.89, 129.46, 128.9, 128.67, 127.71, 125.22, 123.99, 123.44 (q, J= 272.7 Hz), 121.34, 111.72; IR (thin film) ν = 3527, 3063, 1622, 1502, 1378, 1358, 1279, 1174, 1135, 895, 682 cm⁻¹; HRMS (El, [M+]) Calcd for C₃₆H₁₈F₁₂O₂: 710.1110. Found: 710.1126.

3,3′-Bis(tert-butyl)-6,6′-dimethyl-biphenol (G)

In a 250 mL three-necked round bottom flask with reflux condenser 2-tert-butyl-5-methyl-phenol (89.7 g, 546 mmol) and tert-butyl peroxide (7.98 g, 54.6 mmol) were mixed and heated to 140 °C for 36 h. The mixture was cooled to room temperature and residual phenol was distilled off in vacuo. The residue was purified by flash column chromatography (silica gel, hexanes) to give the product as a white solid (16.4 g, 50.2 mmol, 92%): ¹H NMR (CDCl₃, 300 MHz, 23 °C) δ 7.26 (d, J= 8.0 Hz, 2H, Ar), 6.86 (d, J= 8.0 Hz, 2H, At), 5.00 (s, 2H, OH), 1.93 (s, 6H, Me), 1.41 (s, 18H, t-Bu); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ = 152.44, 136.17, 133.84, 127.35, 121.79, 120.05, 34.62, 29.47, 19.16; IR (thin film) ν = 3515, 2959, 2914, 2870, 1606, 1485, 1414, 1384, 1270, 1185, 1136, 812 cm⁻¹; HRMS (ESI, [M + H]) Calcd for C₂₂H₃₁O₂: 327.2319. Found: 327.2328.

5-tert-Butyl-3-(5-tert-butyl-2-methyl-3,6-dioxocyclohexa-1,4-dienyl)-2-methylcyclohexa-2,5-diene-1,4-dione (H)

In a 50 mL flask 3,3′-bis(tert-butyl)-6,6′-dimethyl-biphenol (500 mg, 1.53 mmol) was dissolved in chloroform (25 mL) and mCPBA (660 mg, 3.83 mmol) was added. The mixture was stirred at room temperature for 48 h. After addition of more chloroform the mixture was washed with aqueous sodium thiosulfate and sodium hydrogen carbonate solution. The chloroform layer was dried over Na₂SO₄ and the solvent was evaporated in vacuo. Flash column chromatography (silica gel, hexane/ethyl acetate 20:1) and recrystallization from diethyl ether gave the product as a yellow solid (292 mg, 54%): ¹H NMR (CDCl₃, 300 MHz) δ 6.63 (s, 2, Ar), 1.79 (s, 6, Me), 1.24 (s, 18, CMe₃); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 187.41, 185.29, 156.15, 141.61, 140.01, 131.44, 35.24, 29.04, 13.14; IR (thin film) ν = 2963, 1653, 1635, 1457, 1317, 1251, 1189, 897 cm⁻¹; HRMS (ESI, [M + H]) Calcd for C₂₂H₂₇O₄: 355.1904. Found: 355.1918.

3,3′-Bis(tert-butyl)-5,5′-bis(trifluoromethyl)-6,6′-dimethyl-biphenol (I)

In a 25 mL flask the dienone H (200 mg, 0.564 mmol) and potassium carbonate (20.0 mg, 0.145 mmol) were dissolved in DMF (1 mL) and trifluoromethyltrimethylsilane (241 mg, 1.69 mmol) was added. The orange mixture turned dark and was stirred for 12 h at room temperature. After addition of water, the mixture was extracted with ether and the ether layer was dried over sodium sulfate. The solvent was evaporated in vacuo and the residue was dissolved in a mixture of THF and water (9:1, 15 mL). Aluminum foil (152 mg, 5.64 mmol) was amalgamated by dipping it in an aqueous mercuric chloride solution (2%) for 15 seconds, followed by dipping in ethanol and then in ether. The foil was cut into fine pieces and added to the quinone solution. The mixture evolved hydrogen and was heated to reflux for 2 h. The gray suspension was filtered and washed with THF (200 mL). The solution was concentrated in vacuo and extracted with diethyl ether. The ether layer was dried over Na₂SO₄ and the solvent was evaporated in vacuo. Flash column chromatography (silica gel, hexane/ethyl acetate 30:1) gave the product as white crystals (183 mg, 70%): ¹H NMR (CDCl₃, 300 MHz) δ 7.82 (s, 2, Ar), 4.59 (s, 2, OH), 1.90 (s, 6, Me), 1.30 (s, 18, CMe₃); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 154.82, 135.56, 134.44, 128.88, 126.25 (q, J = 5.9 Hz), 124.8 (q, J= 272.9 Hz), 122.0 (q, J= 29.5 Hz), 121.20, 34.91, 29.19, 15.56; ¹⁹F NMR (CDCl₃, 282 MHz, 23 °C) δ = − 59.6; IR (thin film) ν = 3520, 2965, 2917, 1611, 1576, 1473, 1365, 1327, 1304, 1259, 1185, 1095, 908, 737, 674, 669, 608 cm⁻¹; HRMS (ESI, [M − H]) Calcd for C₂₄H₂₇F₆O₂: 461.1910. Found: 461.1926.

3-tert-Butyl-3-(3-tert-butyl-2-hydroxy-6-methylphenyl)-5-methyl-4-trifluoromethyl-phenol (H₂[Biphen_CF3])

In a 100 mL flask semiquinone I (6.00, 17.6 mmol) and potassium carbonate (205 mg, 3.52 mmol) were dissolved in DMF (20 mL) and trifluoromethyltrimethylsilane (3.00 g, 21.1 mmol) added. The orange mixture turned dark and was stirred for 12 h at room temperature. Water was added and the mixture was extracted with ether. The ether layer was dried over sodium sulfate and the solvent evaporated in vacuo. The residue was dissolved in a THF/water mixture (9:1, 200 mL). Aluminum foil (4.75 g, 176 mmol) was amalgamated by dipping in an aqueous mercuric chloride solution (2%) for 15 seconds, then in ethanol and ether. The foil was cut into fine pieces and added to the quinone solution. The mixture evolved hydrogen and was heated to reflux for 2 h. The gray suspension was filtered and washed with THF (400 mL). The solution was concentrated in vacuo and extracted with diethyl ether. The ether layer was dried over Na₂SO₄ and the solvent was evaporated. Flash column chromatography (silica gel, hexane/ethyl acetate 30:1) gave the product as a white powder (2.85 g, 41%): ¹H NMR (CDCl₃, 300 MHz) δ 7.68 (s, 1, Ar), 7.34 (d, J= 8.0 Hz, 1, Ar), 6.92 (d, J= 8.0 Hz, 1, Ar), 5.39 (s, 1, OH), 4.88 (s, 1, OH), 2.08 (m, 3, Me), 1.93 (s, 3, Me), 1.45 (m, 18, CMe₃); ¹³C NMR (CDCl₃, 75 MHz, 23 °C) δ 154.91, 152.44, 136.14, 134.47, 133.81, 128.85, 128.06, 125.61, 125.54, 122.44, 122.29, 118.92, 34.82, 34.68, 30.29, 29.45, 29.19, 19.11; ¹⁹F NMR (CDCl₃, 282 MHz, 23 °C) δ − 59.9; IR (thin film) ν = 3529, 3495, 2961, 2915, 2872, 1576, 1330, 1259, 1188, 1118, 1090, 907, 846, 675 cm⁻¹; HRMS (EI, [M+]) Calcd for C₂₃H₂₉F₃O₂: 394.2114. Found: 394.2121.

Mo(N-2,6-i-Pr2C₆H₃)(CHCMe₂Ph)(2,5-Me₂NC₄H₂)₂ (1a)

2,5-dimethylpyrrolide (103 mg, 1.01 mmol) was added to a chilled (−30 °C) solution of Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) (400 mg, 0.511 mmol) in Et₂O (30 mL), and the reaction was warmed to room temperature during which time the solution’s color changed from yellow to red. After 3 h, the volatiles were removed in vacuo and the crude solid was extracted with toluene (40 mL). Removal of the volatiles in vacuo yielded a dark red solid. Addition of pentane and filtration produced the product as a yellow solid (270 mg, 90%): ¹H NMR (C₆D₆, 300 MHz) δ 13.30 (s, 1, syn Mo = CH, J_CH = 120 Hz), 7.37 (d, 2, Ar) 7.7.14 (m, 3, Ar) 7.03 (d, 1, Ar) 6.97 (d, 2, Ar) 5.94 (br s, 2, NC₄H₂) 3.54 (sept, 2, MeCHMe), 2.02 (s, 12, Me₂NC₄H₂), 1.72 (s, 6, HCMe₂), 1.69 (br, 12, MeCHMe); ¹³C NMR (CD₂Cl₂, 125 MHz) δ 315.16, 151.88, 149.32, 128.72, 127.83, 126.85, 126.44, 124.13, 105.64, 70.77, 58.22, 31.61, 27.99, 25.19, 24.13, 22.79, 18.17. Anal. Calcd for C₃₄H₄₅MoN₃: C, 69.02; H, 7.67; N, 7.10. Found: C, 69.01; H, 7.60; N, 7.14.

Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)(2,5-Me₂NC₄H₂) (1b)

The synthesis was analogous to that for 1a; yield 83%: ¹H NMR (C₆D₆, 300 MHz) δ 13.19 (s, 1, syn Mo=CH, J_CH = 120 Hz), 7.29 (d, 2, Ar) 7.07 (t, 3, Ar) 7.03 (d, 1, Ar) 6.77 (s, 2, Ar) 5.94 (br s, 2, NC₄H₂) 2.16 (s, 6, Me₂C₆H₃), 2.02 (s, 12, Me₂NC₄H₂), 1.61 (s, 6, HCMe₂); ¹³C NMR (CD₂Cl₂, 125 MHz) δ 314.41, 154.34, 149.20, 136.61, 128.76, 128.70, 128.60, 126.96, 126.88, 126.29, 105.91, 57.53, 31.03, 19.64, 17.90. Anal. Calcd for C₃₀H₃₇MoN₃: C, 67.28; H, 6.96; N, 7.85. Found: C, 67.34; H, 7.08; N, 7.74.

Mo(N-1-adamantyl)(CHCMe₂Ph)(2,5-Me₂NC₄H₂) (1c)

The synthesis was analogous to that for 1a; yield 86%: ¹H NMR (C₆D₆, 300 MHz) δ 12.94 (s, 1, syn Mo = CH, J_CH = 120 Hz), 7.38 (d, 2, Ar) 7.10 (t, 3, Ar) 6.98 (d, 1, Ar) , 5.96 (br s, 2, NC₄H₂), 2.22 (br s, 12, Me₂NC₄H₂), 1.77 (s, 3, adamantyl), 1.53 (s, 6, HCMe₂), 1.45 (s, 6, adamantyl), 1.34 (s, 6, adamantyl); ¹³C NMR (CD₂Cl₂, 125 MHz) δ 306.87, 151.05, 128.47, 127.81, 126.10, 74.40, 54.91, 44.45, 36.13, 30.16, 30.10. Anal. Calcd for C₃₂H₄₃MoN₃: C, 67.95; H, 7.66; N, 7.43. Found: C, 68.09; H, 7.60; N, 7.28.

Mo(N-2-(CF₃)C₆H₄)(CHCMe₂Ph)(2,5-Me₂NC₄H₂) (1d)

The synthesis was analogous to that for 1a; yield 82%: ¹H NMR (C₆D₆, 300 MHz) δ 13.19 (s, 1, syn Mo = CH, J_CH = 120 Hz), 7.30 (d, 2, Ar), 7.20 – 6.85 (m, 5, Ar), 6.64 (t, 1, Ar), 6.44 (t, 1, Ar), 6.02 (br s, 2, NC₄H₂), 2.08 (br s, 12, Me₂NC₄H₂), 1.59 (s, 6, HCMe₂); ¹³C NMR (CD₂Cl₂, 125 MHz) δ 317.76, 152.73, 149.45, 132.85, 132.05, 128.63, 127.15, 126.59, 126.39, 126.16, 125.20, 123.04, 122.83, 120.86, 59.12, 31.33, 27.99 ; ¹⁹F NMR (C₆D₆, 471 MHz) δ − 60.42. Anal. Calcd for C₂₉H₃₂F₃MoN₃: C, 60.52; H, 5.60; N, 7.30. Found: C, 60.46; H, 5.52; N, 7.24.

Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(Binaph_Anth)(THF) (2a)

To a 50 mL round-bottom flask charged with Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) (200 mg, 0.252 mmol), H₂[Binaph_Anth] (162 mg, 0.252 mmol), THF (15 mL), Et₃N (0.175 mL, 1.26 mmol), and the reaction stirred at room temperature for 12 h. The volatiles were removed in vacuo. Addition of pentane to the crude solid yielded in yellow powder. The yellow powder was isolated by filtration and recrystallized from a mixture of THF and pentane (2:4) to yield yellow crystals (250 mg, 90%): ¹H NMR (CD₂Cl₂, 500 MHz) δ 12.89 (s, 1, anti Mo = CH, J_CH = 147 Hz), 11.95 (s, 1, syn Mo = CH, J_CH = 116 Hz), anti isomer 8.47 - 8.38 (m, 3, Ar), 8.11 - 7.85 (m, 10, Ar), 7.58 - 7.50 (m, 3, Ar), 7.42 - 7.22 (m, 10, Ar), 7.15 - 7.11 (m, 2, Ar), 7.04 - 6.86 (m, 3, Ar), 6.76 (t, 2, Ar), 6.41 (d, 2, Ar), 6.16 (t, 1, Ar), 3.66 (br, 4, CH₂OCH₂), 3.12 (sept, 2, MeCHMe), 1.34 (s, 3, HC(Me)Me), 1.35 (s, 3, HC(Me)Me), 0.81 (d, 3, inequivalent Me of i-Pr), 0.65 (d, 3, inequivalent Me of i-Pr), 0.62 (s, 4, CH₂CH₂) 0.34 (d, 3, inequivalent Me of i-Pr), 0.05 (d, 3, inequivalent Me of i-Pr); ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 317.15, 164.77, 162.07, 155.16, 150.45, 145.83, 143.16, 137.29, 136.42, 135.83, 135.58, 133.54. 132.49, 132.43, 132.13, 131.82, 131.69, 131.40, 131.29, 131.02, 130.67, 130.54, 130.28, 130.16, 129.34, 129.04, 128.77, 128.72, 128.67, 128.51, 128.46, 128.44, 128.37, 128.33, 128.26, 127.56, 127.23, 127.18, 126.49, 126.45, 126.39, 126.02, 125.97, 125.84, 125.81, 125.76, 125.71, 125.52, 125.33, 125.20, 125.06, 124.09, 123.07, 123.04, 122.62, 122.13, 119.90, 68.60, 51.03, 47.38, 29.12, 28.07, 27.34, 27.18, 25.76, 24.75, 22.35, 21.99, 21.89, 21.81. Anal. Calcd for C₇₄H₆₅MoNO₃: C, 79.91; H, 5.89; N, 1.26. Found: C, 80.09; H, 5.81; N, 1.24.

Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)(Binaph_Anth)(THF) (2b)

Compound 2b was prepared in a manner similar to 2a and isolated in 84% yield: ¹H NMR (CD₂Cl₂, 500 MHz) δ 12.73 (s, 1, anti Mo = CH) 12.05 (s, 1, syn Mo = CH), one isomer 8.47 - 8.40 (m, 3, Ar), 8.10 -7.87 (m, 10, Ar), 7.52 - 7.24 (br m, 13, Ar), 7.11 (br s, 2, Ar), 7.01 - 6.93 (m, 3, Ar), 6.60 (t, 2, Ar), 6.42 (d, 2, Ar), 6.22 (br, 1, Ar), 3.12 (br s, CH₂OCH₂), 1.37 (br s, 3, Me), 1.34 (br s, 3, Me), 0.91 (m, 4, CH₂CH₂), 0.74 (s, 3, HC(Me)Me), 0.66 (s, 3, HC(Me)Me); ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 315.15, 168.90, 168.77, 164.30, 164.09, 162.57, 162.25, 156.32, 155.37, 151.73. 150.29, 150.11, 137.11, 135.95, 135.68, 135.49, 135.12, 134.99, 134.44, 133.70, 133.57, 133.31, 132.51, 132.27, 132.08, 131.97, 131.93, 131.77, 131.67, 131.54, 131.37, 131.26, 130.94, 130.74, 129.85, 129.64, 129.47, 129.19, 129.06, 128.98, 128.90, 128.62, 128.54, 128.49, 128.44, 128.34, 128.22, 128.08, 127.90, 127.79, 127.73, 127.70, 127.62, 126.82, 126.66, 126.50, 126.45, 126.30, 126.22, 126.08, 126.00, 125.93, 125.89, 125.83, 125.74, 125.66, 125.57, 125.15, 125.05, 124.84, 124.75, 124.17, 123.36, 123.16, 123.03, 122.93, 122.36, 119.89, 50.85, 47.36, 32.55, 28.46, 25.11, 19.99. Anal. Calcd for C₇₀H₅₇MoNO₃: C, 79.61; H, 5.44; N, 1.33. Found: C, 79.47; H, 5.37; N, 1.31.

Mo(N-1-adamantyl)(CHCMe₂Ph)(Binaph_Anth)(THF) (2c)

Compound 2c was prepared in a manner similar to 2a and isolated in 92% yield: ¹H NMR (CD₂Cl₂, 500 MHz) δ 12.60 (br s, 1, Mo = CH), 8.44 (br s, 4, Ar), 8.01 - 7.69 (m, 13, Ar), 7.44 - 7.10 (m, 12, Ar), 6.92 (br s, 2, Ar), 6.75 (br s, 2, Ar), 3.13 (t, 4, CH₂OCH₂), 2.08 (br s, 1, adamantyl), 1.87( br s, 1, adamantyl), 1.72 (br s, 2, adamantyl), 1.42 (br s, 4, adamantyl), 1.34 (br s, 6, HCMe₂), 1.09 (s, 2, adamantyl), 0.49 (br s, 4, CH₂CH₂); ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 291.73, 178.08, 166.48, 160.38, 150.09, 137.53, 136.64, 135.87, 135.28, 133.67. 132.69, 131.98, 131.87, 131.44, 131.12, 130.71, 129.93, 129.31, 129.05, 128.81, 128.43, 128.38, 128.32, 128.23, 128.17, 127.92, 127.28, 126.65, 126.38, 125.80, 125.66, 125.38, 122.99, 122.57, 122.22, 122.15, 121.28, 120.64, 119.68, 117.15, 113.99, 76.74, 72.93, 49.93, 47.43, 43.55, 36.07, 32.19, 29.81, 25.86, 24.31, 22.89.

Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(Binaph_C6F5)(THF) (3a)

H₂[Binaph_C6F5] (209 mg, 0.340 mmol) dissolved in THF (2 mL) was added dropwise to a stirred solution (− 30 °C) of la (200 mg, 0.340 mmol) in THF (20 mL). The solution was allowed to come to room temperature and was stirred for 2 h. The volatiles were removed in vacuo and addition of pentane afforded yellow powder (310 mg, 84%): ¹H NMR (C₆D₆, 300 MHz) δ 13.81 (s, 1, anti Mo=CH, J_CH = 140 Hz), 7.80 (s, 1, Ar) 7.76 (s, 1, Ar) 7.73 (s, 1, Ar), 6.70 (s, 1, Ar), 7.41 (d, 1, Ar), 7.15 - 7.06 (m, 6, Ar), 6.99 - 6.80 (m, 7, Ar), 3.78 (br s, 1, MeCHMe),3.10 (d, 4, CH₂OCH₂), 1.72 (s, 3, HC(Me)MePh), 1.46 (s, 3, HC(Me)MePh), 0.95 - 0.78 (br, 12, HCMe₂), 0.42 (br, 4, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282MHz) δ − 133.14, − 136.40, − 139.28, − 142.21, − 157.80, − 158.21, −162.19, −162.99, −163.88, − 165.17; ¹³C NMR (CD₂Cl₂, 125 MHz) δ 319.64, 161.83, 160.07, 154.29, 150.47, 146.57, 146.17, 145.62, 144.60, 144.21, 143.66, 141.70, 139.55, 138.90, 137.50, 136.92, 136.20, 135.61, 132.55, 131.88, 132.55, 131.88, 129.53, 128.94, 128.85, 128.73, 128.57, 127.91, 127.19, 126.93, 126.68, 126.29, 125.85, 123.64, 123.44, 121.88, 119.68, 117.08, 114.36, 106.22, 75.66, 52.13, 29.57, 28.77, 27.98, 27.10, 26.40, 25.64, 22.96. Anal. Calcd for C₅₈H₄₇F₁₀MoNO₃: C, 63.80; H, 4.34; N, 1.28. Found: C, 63.65; H, 4.36; N, 1.23.

(R)-Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)(Binaph_c6F5)(THF) (3b)

Compound 3b was prepared using the same protocol as that employed for 3a and was isolated in a yield of 86%: ¹H NMR (C₆D₆, 500MHz) δ 13.65 (s, 1, anti Mo=CH, J_CH= 140 Hz), 7.87 - 7.76 (m, 4, Ar), 7.46 (d, 1, Ar), 7.32 (d, 1, Ar), 7.19 - 7.12 (m, 6, Ar), 6.98 (t, 2, Ar), 6.89 (t, 1, Ar), 6.84 (br s, 1, Ar), 6.72 - 6.61 (m, 2, Ar), 3.31 (br s, 2, CH₂OCH₂), 2.91 (br s, 2, CH₂OCH₂), 2.24 (s, 3, Me), 1.70 (s, 3, Me), 1.49 (s, 3, HC(Me)Me), 1.42 (s, 3, HC(Me)Me), 0.77 (br s, 2, CH₂CH₂), 0.69 (br s, 2, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282MHz) δ - 130.49, - 134.11, - 137.29, - 140.40, - 156.41, -157.09, - 161.30, - 162.59, - 162.79 - 163.53; ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 318.99, 161.27, 159.94, 155.90, 154.59, 150.34, 149.47, 146.36, 145.47, 144.39, 143.50, 141.67, 141.34, 139.49, 138.71, 136.76, 135.50, 135.22, 133.16, 132.49, 131.91, 129.17, 128.87, 128.82, 128.68, 128.34, 128.20, 128.02, 127.18, 126.95, 126.77, 126.67, 126.43, 126.34, 125.95, 124.01, 123.68, 122.22, 120.08, 119.71, 119.65, 116.63, 113.98, 76.44, 52.08, 28.60, 27.40, 25.32, 19.39, 17.74. Anal. Calcd for C₅₄H₃₉F₁₀MoNO₃: C, 62.62; H, 3.80; N, 1.35. Found: C, 62.80; H, 3.73; N, 1.28.

(R)-Mo(N-1-adamantyl)(CHCMe₂Ph)( Binaph_C6F5)(THF) (3c)

Compound 3c was prepared using the same protocol as that employed for 3a and the yield was 85%: ¹H NMR (C₆D₆, 500MHz) δ 12.59 (s, 1, Mo=CH), 7.99 (br s, 1, Ar), 7.84 (br s, 1, Ar) 7.76 (br s, 1, Ar), 7.71 (d, 2, Ar), 7.55 (br s, 1, Ar), 7.27 (d, 2, Ar), 7.08 (t, 1, Ar), 6.98 (br, 2, Ar), 6.87 (t, 1, Ar), 6.82 - 6.72 (br, 3, Ar), 2.85 (br, 4, CH₂OCH₂), 1.94 - 1.83 (br, 6, adamantyl), 1.46 (br s, 3, adamantyl), 1.44 (br s, 3, adamantyl), 1.18 (br s, 3, adamantyl), 0.64 (br, 4, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282MHz) δ - 130.49, - 134.11, - 137.29, - 140.40, - 156.41, - 157.09, - 161.30, -162.59, - 162.79 - 163.53 ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 294.06, 166.26, 159.40, 149.57, 146.64, 146.23, 145.69, 144.59, 144.26, 143.75, 141.41, 139.36, 137.39, 136.00, 135.40, 132.25, 131.72, 128.89, 128.76, 126.89, 126.80, 126.48, 123.56, 123.16, 121.73, 121.07, 119.91, 118.90, 116.31, 115.51, 77.95, 73.61, 49.97, 44.23, 36.35, 30.08, 24.81, 22.93. Anal. Calcd for C₅₆H₄₅F₁₀MoNO₃: C, 63.10; H, 4.26; N, 1.31. Found: C, 62.88; H, 4.18; N, 1.26.

(R)-Mo(N-2-(CF₃)C₆H₄)(CHCMe₂Ph)( Binaph_C6F5)(THF) (3d)

Compound 3d was prepared using the same protocol as that employed for 3a and the yield was 84%: ¹H NMR (C₆D₆, 500MHz) δ 14.08 (s, 1, anti Mo=CH), 13.36 (br s, 1, syn Mo=CH), one isomer 7.86 (s, 1, Ar), 7.78 - 7.69 (m, 4, Ar), 7.46 (t, 1, Ar), 7.34 (d, 1, Ar), 7.24 - 7.06 (m, 6, Ar), 6.55 (t, 2, Ar), 6.53 (t, 1, Ar), 6.40 (br s, 1, Ar), 6.02 (d, 2, Ar), 3.41 (q, 2, CH₂OCH₂), 2.84 (q, 2, CH₂OCH₂), 1.59 (s, 3, HC(Me)Me), 1.37 (s, 3, HC(Me)Me), 0.88 (q, 4, CH₂CH₂); ¹⁹F NMR one isomer (C₆D₆, 282MHz) δ - 60.61, - 132.57, - 136.45, 139.07, - 143.09, - 158.10, - 158.96, - 163.01, - 164.80, - 165.34; ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 320.44 (anti C_α), 307.09 (syn C_α). Anal. Calcd for C₅₃H₃₄F₁₃MoNO₃: C, 59.17; H, 3.19; N, 1.30. Found: C, 59.32; H, 3.26; N, 1.32.

Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(Binaph_CF3)(THF) (4a)

A solution of H₂[Binaph_CF3] (240 mg, 0.338 mmol) in THF (2 mL) was added to a stirred solution of 1a (200 mg, 0.338 mmol) in THF (20 mL) and the reaction stirred at room temperature for 1 h. Removal of the volatiles in vacuo afforded a yellow residue which dissolved in pentane (2 mL). Cooling the pentane solution to - 30 °C yielded 4a as a yellow powder (150 mg, 37%): ¹H NMR (C₆D₆, 300 MHz) δ 13.77 (s, 1, anti Mo=CH), 12.23 (s, 1, syn Mo=CH), 8.13 (s, 1, Ar), 8.12 (s, 1, Ar), 7.90 (s, 1, Ar), 7.82 - 7.71 (m, 3, Ar), 7.64 - 7.47 (m, 4, Ar), 7.29 (d, 1, Ar), 7.23 - 7.02 (m, 10 Ar), 6.90 (t, 1, Ar), 6.81 (d, 2, Ar), 3.29 (br, 2, MeCHMe), 3.25 (br, 4, CH₂OCH₂), 1.85 (s, 3, HC(Me)Me), 1.34 (s, 3, HC(Me)Me), 1.12 (d, 6, MeCHMe), 1.09 (d, 6, MeCHMe), 0.70 (br, 4, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282MHz) δ - 61.92, - 62.19 (anti), - 61.99, - 62.30 (syn); ¹³C NMR one isomer (CD₂Cl₂, 125 MHz) δ 317.90 (C_α. Anal. Calcd for C₆₂H₅₃F₁₂MoNO₃: C, 62.89; H, 4.51; N, 1.81. Found: C, 62.76; H, 4.61; N, 1.09.

In situ generation of Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)( Binaph_CF3) (4b′)

H₂[Binaph_CF3] (9 mg, 0.013 mmol) was added as a solid to the solution of 1b (10 mg, 0.013 mmol, 0.024 M) in CeDe in a J-Young NMR tube. Conversion to 4b′ was complete after 15 mins according to ¹H NMR: ¹H NMR (C₆D₆, 500 MHz) δ 10.86 (s, 1, base-free syn Mo=CH), 7.65 (s, 1,Ar), 7.62 (s, 1, Ar), 7.60 (s, 1,Ar), 7.45 - 6.54 (m, 21, Ar), 6.23 (br, 2, N_pyrH), 5.91 (d, 4, CHCH_pyr), 1.70 (s, 6, Me₂C₆H₃), 1.18 (s, 12, Me₂NC₄H₂), 0.79 (s, 6, HCMe₂).

Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)( Binaph_CF3) (4a′): (C₆D₆, 500 MHz) δ 10.86 (s, 1, base-free syn Mo=CH); Mo(N-1-adamantyl)(CHCMe₂Ph)( Binaph_CF3) (4c′): (C₆D₆, 500 MHz) δ 10.62 (s, 1, base-free syn Mo=CH); and Mo(N-2-CF₃C₆H₄)(CHCMe₂Ph)( Binaph_CF3) (4d′) (C₆D₆, 500 MHz) δ 13.71 (s, 1, anti Mo=CH), 10.66 (s, 1, syn Mo=CH) were generated in situ in a similar manner.

Mo(N-2,6-i-Pr₂C₆H₃)(CHCMe₂Ph)(Biphen_CF3)(THF) (5a)

To a 100 mL round-bottom flask charged with Mo(NAr)(CHCMe₂Ph)(OTf)₂(DME) (500 mg, 0.632 mmol), H₂[Biphen_CF₃] (292 mg, 0.632 mmol) and THF (60 mL), Et₃N (0.890 mL, 6.32 mmol) was added via a syringe. The reaction was stirred at room temperature for 12 h. The volatiles were removed in vacuo and the residue was extracted with pentane (60 mL). Concentration of the pentane solution resulted in formation of a yellow solid that was isolated by filtration (300 mg, 50%): ¹H NMR (C₆D₆ 500MHz) δ 14.17 (s, 1, anti Mo=CH), 11.46 (br s, 1, syn Mo=CH), 7.90 (s, 1,Ar), 7.78 (br s, 1, Ar) 7.28 (br s, 2, Ar) 7.12 (t, 2, Ar), 7.00 (t, 1, Ar), 6.91 (m, 3, Ar), 3.62 (br, 2, MeCHMe), 3.48 (br, 4, CH₂OCH₂), 2.13 (s, 6, CMe₂), 1.68 (s, 3, BiphenMe), 1.57 (s, 3, BiphenMe), 1.43 (s, 9, Biphen-t-Bu), 1.37 (s, 9, Biphen- t-Bu), 1.20 (br, 4, CH₂CH₂), 1.11 (d, 12, MeCHMe); ¹⁹F NMR (C₆D₆, 282MHz) δ −58.21, −58.40, −58.77, −58.90; ¹³C NMR (CD₂Cl₂, 125 MHz) both isomers δ 322.00 (anti, C_α), 290.30 (syn, C_α), 154.54, 154.00, 150.61, 149.81, 136.08, 135.28, 134.99, 131.38, 131.07, 130.17, 128.92, 128.88, 128.83, 128.65, 127.95, 126.78, 126.74, 126.70, 126.67, 126.64, 123.85, 123.56, 35.96, 35.87, 35.52, 35.49, 30.96, 30.81, 30.48, 30.38, 30.03, 29.48, 29.43, 25.91, 24.54, 24.45, 23.44, 16.00, 15.89. Anal. Calcd for C₅₀H₆₃F₆MoNO₃: C, 64.16; H, 6.78; N, 1.50. Found: C, 64.04; H, 6.85; N, 1.48.

Mo(N-2,6-Me₂C₆H3)(CHCMe2Ph)(Biphen_CF3)(THF) (5b)

Complex 5b was prepared in a manner analogous to 5a and isolated in 60% yield: ¹H NMR (C₆D₆, 500MHz) δ 14.10 (s, 1, anti Mo=CH J_CH= 146 Hz), 12.41 (br, 1, syn Mo=CH J_CH= 117 Hz), 7.93 (s, 1, Ar), 7.72 (s, 1, Ar), 7.39 (d, 2, Ar), 7.18 (t, 1, Ar), 7.10 – 6.96 (m, 2, Ar), 6.71 (d, 2, Ar), 6.63 (t, 1, Ar), 3.45 (br s, 4, CH₂OCH₂), 2.16 (s, 3, CMe₂Ph), 2.15 (s, 3, ArMe) 2.08 (s, 3, CMe₂Ph), 2.05 (s, 3, ArMe), 1.66 (s, 3, BiphenMe), 1.53 (s, 3, BiphenMe), 1.47 (s, 8, Biphen-t-Bu), 1.33 (s, 9, Biphen-t-Bu), 0.98 (br s, 4, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282MHz) δ − 58.2, − 58.3 , − 58.8; ¹³C NMR (C₆D₆, 125 MHz) both isomers δ 320.48, 168.31, 165.48, 156.67, 156.21, 150.76, 149.46, 136.50, 135.45, 134.92, 132.22, 131.99, 131.15, 129.87, 128.99, 128.92, 127.42, 127.28, 126.96, 126.68, 126.32, 126.11, 126.01, 125.70, 124.84, 124.03, 120.83, 75.40, 55.21, 53.72, 35.85, 35.74, 35.69, 34.80, 32.33, 31.16, 30.98, 30.79, 30.68, 30.63, 28.60, 27.22, 25.21, 23.10, 20.11, 19.03, 16.76, 16.60, 16.15, 15.66. Anal. Calcd for C₄₆H₅₅F₆MoNO₃: C, 62.79; H, 6.30; N, 1.59. Found: C, 62.88; H, 6.38; N, 1.62.

Mo(N-1-adamantyl)(CHCMe₂Ph)(Biphen_CF3)(THF) (5c)

Complex 5c was prepared in a manner analogous to 5a and isolated in 71% yield: ¹H NMR (C₆D₆, 500MHz) δ 12.14 (br, 1, syn Mo=CH), 7.92 (s, 1, Ar), 7.86 (s, 1, Ar), 7.26 (d, 2, Ar), 7.15 (t, 2, Ar), 7.01 (t, 1, Ar), 3.42 (br s, 4, CH₂OCH₂), 2.11 (s, 3, CMe₂Ph), 2.08 (s, 3, CMe₂Ph), 1.78 (br s, 6, adamantyl), 1.71 (br s, 3, adamantyl), 1.66 (s, 3, BiphenMe), 1.59 (s, 3, BiphenMe), 1.47 (s, 9, Biphen-t-Bu), 1.42 (s, 9, Biphen-t-Bu), 1.33(br s, 6, adamantyl), 1.23 (m, 4, CH₂CH₂); ¹⁹F NMR (C₆D₆, 282 MHz) δ −58.36, −58.52; ¹³C NMR (CD₂Cl₂, 125 MHz, − 40 °C) both diastereomers δ 309.11, 295.71, 171.06, 168.30, 165.96, 165.39, 148.92, 147.95, 135.02, 134.32, 134.10, 133.91, 132.55, 131.26, 130.70, 130.01, 129.72, 128.35, 126.50, 126.98, 126.22, 126.14, 125.96, 125.86, 124.81, 124.70, 123.84, 123.34, 123.15, 118.46, 117.33, 77.42, 76.93, 74.97, 73.83, 51.13, 50.37, 44.24, 44.08, 35.68, 35.57, 35.12, 34.84, 34.37, 32.47, 31.78, 30.80, 30.32, 30.15, 29.83, 29.69, 29.52, 29.42, 29.28, 25.88, 25.65, 22.77, 15.98, 15.75, 15.62, 15.30. Anal. Calcd for C₄₈H₆₁F₆MoNO₃: C, 63.36; H, 6.76; N, 1.54. Found: C, 63.26; H, 6.71; N, 1.47.

Preliminary ring-closing metathesis reactions

Diallylether (0.225 mmol, 28 μL) was added to a solution of 2a (10 mg, 0.009 mmol) in CeDe. The solution was transferred to a J. Young NMR tube and ¹H NMR spectra recorded after the stated time interval at the stated temperature. A similar procedure was employed for ring-closing diallyltosylamine.