(R,R Fc,S Ru)-Chlorido(η6-p-cymene){1-[1-(diphenyl­phosphanyl)ethyl]-2-[2-(diphenyl­phosphanyl)phenyl]ferrocene-κ2 P,P′}ruthenium(II) hexa­fluorido­phosphate

Raffael Schuecker; Walter Weissensteiner; Kurt Mereiter

doi:10.1107/S1600536811036506

. 2011 Sep 14;67(Pt 10):m1379–m1380. doi: 10.1107/S1600536811036506

(R,R _Fc,S _Ru)-Chlorido(η⁶-p-cymene){1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene-κ² P,P′}ruthenium(II) hexafluoridophosphate

Raffael Schuecker ^a, Walter Weissensteiner ^a, Kurt Mereiter ^b,^*

PMCID: PMC3201293 PMID: 22058697

Abstract

The asymmetric unit of the title compound, [FeRuCl(C₅H₅)(C₁₀H₁₄)(C₃₇H₃₁P₂)]PF₆, contains two independent, geometrically similar Ru^II complexes of a chiral ferrocenyldiphosphane with piano-stool coordination through the η⁶-bound p-cymene ligand, two chelating phosphorus donor atoms, and an exo-oriented chloride ion. The mean bond lengths of the two Ru complexes are Ru—C = 2.276 Å, Ru—P = 2.3816 Å, and Ru—Cl = 2.3924 Å. Both chloride ligands form only intramolecular C—H⋯Cl interactions. Seven weak intermolecular C—H⋯F interactions involving mainly arene H atoms consolidate the crystal packing, which reveals an approximate c/2 pseudo-translation relating the two independent Ru complex molecules.

Related literature

For general information on ferrocene-based diphosphanes and their applications in asymmetric catalysis, see: Togni (1996 ▶); Blaser et al. (2002 ▶, 2007 ▶); Dai & Hou (2010 ▶); Solvias (2011 ▶). For the synthesis, coordination behaviour and use of Walphos-type ligands in asymmetric catalysis, see: Weissensteiner et al. (2002 ▶); Sturm et al. (2003 ▶); Wang et al. (2008 ▶). For crystal structures with Walphos-type ligands, see: Moberg et al. (2007 ▶); Maddox et al. (2008 ▶). For crystal structures of Ru(II)–(p-cymene) complexes with non-ferrocenyl phosphane ligands, see: Jensen et al. (1998 ▶); Lalrempuia et al. (2003 ▶); Chaplin & Dyson (2007 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶).

Experimental

Crystal data

[FeRuCl(C₅H₅)(C₁₀H₁₄)(C₃₇H₃₁P₂)]PF₆
M _r = 1074.20
Monoclinic,
a = 12.7479 (8) Å
b = 15.8091 (10) Å
c = 22.8897 (15) Å
β = 97.378 (2)°
V = 4574.8 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.87 mm⁻¹
T = 100 K
0.42 × 0.33 × 0.24 mm

Data collection

Bruker Kappa APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.74, T _max = 0.81
84544 measured reflections
26641 independent reflections
25880 reflections with I > 2σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.027
wR(F ²) = 0.069
S = 1.02
26641 reflections
1154 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 1.32 e Å⁻³
Δρ_min = −0.29 e Å⁻³
Absolute structure: Flack (1983 ▶), 12869 Friedel pairs
Flack parameter: −0.005 (6)

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811036506/kp2346sup1.cif

e-67-m1379-sup1.cif^{(97.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811036506/kp2346Isup2.hkl

e-67-m1379-Isup2.hkl^{(1.3MB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Ru1—P1	2.3896 (5)
Ru1—P2	2.3810 (5)
Ru1—Cl1	2.3967 (4)
Ru1—C43	2.301 (2)
Ru1—C44	2.262 (2)
Ru1—C45	2.253 (2)
Ru1—C46	2.329 (2)
Ru1—C47	2.250 (2)
Ru1—C48	2.257 (2)
Fe1—C1	2.093 (2)
Fe1—C2	2.099 (2)
Fe1—C3	2.050 (2)
Fe1—C4	2.039 (2)
Fe1—C5	2.038 (2)
Fe1—C6	2.077 (2)
Fe1—C7	2.084 (2)
Fe1—C8	2.058 (2)
Fe1—C9	2.030 (2)
Fe1—C10	2.048 (2)
Ru2—P3	2.3834 (5)
Ru2—P4	2.3725 (5)
Ru2—Cl2	2.3880 (5)
Ru2—C95	2.320 (2)
Ru2—C96	2.261 (2)
Ru2—C97	2.256 (2)
Ru2—C98	2.318 (2)
Ru2—C99	2.235 (2)
Ru2—C100	2.272 (2)
Fe2—C53	2.094 (2)
Fe2—C54	2.096 (2)
Fe2—C55	2.052 (2)
Fe2—C56	2.034 (2)
Fe2—C57	2.039 (2)
Fe2—C58	2.072 (2)
Fe2—C59	2.083 (2)
Fe2—C60	2.055 (2)
Fe2—C61	2.040 (2)
Fe2—C62	2.048 (2)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C20—H20⋯Cl1	0.95	2.69	3.499 (2)	143
C72—H72⋯Cl2	0.95	2.56	3.389 (2)	145
C13—H13⋯F3ⁱ	0.95	2.51	3.076 (2)	118
C22—H22⋯F5ⁱⁱ	0.95	2.40	3.312 (3)	161
C34—H34⋯F6ⁱⁱⁱ	0.95	2.48	3.161 (3)	129
C51—H51C⋯F9^iv	0.98	2.54	3.422 (4)	149
C60—H60⋯F6	0.95	2.55	3.380 (3)	146
C65—H65⋯F11^v	0.95	2.53	3.395 (3)	152
C74—H74⋯F7^vi	0.95	2.50	3.130 (3)	124

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Acknowledgments

This work was kindly supported by Solvias AG, Switzerland.

supplementary crystallographic information

Comment

Ferrocenyl-based diphosphines with an asymmetric carbon atom attached to 1,2-disubstituted planar chiral ferrocenes have emerged as valuable ligands of platinum group metals applied in a variety of important catalytical asymmetric transformations (Togni, 1996; Blaser et al., 2002; Blaser et al., 2007; Dai & Hou, 2010). One of their advantages is that they can be modularly designed and synthesised to give larger ligand families like the well known Josiphos ligands, one of which serves the highly efficient industrial production of the enantiopure herbicide (S)-metolachlor in thousands of tons per year (Blaser et al., 2007). The diphosphine ligand of the title compound belongs to another such family known as the Walphos ligands (Weissensteiner et al., 2002; Sturm et al., 2003; Wang et al., 2008). Within this family, the ligand of the title compound has obtained the designation Walphos SL—W002–1 [chemical name: (R,R_Fc)-[1-[1-(diphenylphosphanyl)ethyl]-2-[2-(diphenylphosphanyl)phenyl]ferrocene]; Solvias, 2011], of which a CF₃-substituted derivative (Walphos SL—W001–1) is now in use in a Rh catalysed key step of the industrial synthesis of the chiral hypertension drug aliskiren (Blaser et al., 2007; Wang et al., 2008). While in previous crystallographic research only mononuclear PdCl₂ and PtCl₂ complexes of Walphos-type ligands were structurally characterised (Wang et al., 2008; Maddox et al., 2008), it was now of interest to determine the crystal structure of a Ru half-sandwich complex of this ligand family. Since all attempts to crystallise a Ru-η⁶-arene complex of Walphos SL—W001–1 failed, the title compound, (I), a Ru(II) complex with p-cymene and the Walphos ligand SL—W002–1 (Scheme 1) was successfully crystallised and studied by X-ray diffraction.

The title compound, (I) crystallizes with two crystallographically independent Ru complexes of very similar overall geometry (Table 1 and Figs. 1, 2 and 3). In both molecules, the Ru(II) reveals a three-legged piano-stool coordination with the η⁶-bound p-cymene ligand, the two chelating phosphorus donor atoms, and an exo-oriented chloride ligand. The bond lengths of the two Ru complexes are in the ranges Ru—C = 2.235 (2) – 2.329 (2) Å (mean value 2.276 Å), Ru—P = 2.3725 (5) – 2.3896 (5) Å (mean value 2.3816 Å), and Ru—Cl = 2.3880 (5) – 2.3967 (4) Å (mean value 2.3924 Å). The bond angles P—Ru—P (102.34 (2)° and 101.02 (2)°) are systematically larger than the angles P—Ru—Cl (80.41 (2) – 83.26 (2)°). These values correspond well with those found in [Ru(p-cymene)(PPh₃)₂Cl](BF₄) [refcode ESCOLUT (Lalrempuia et al., 2003)] and related complexes [refcodes HAJCUQ (Jensen et al., 1998), SIGJUO and SIGKEZ (Chaplin & Dyson, 2007); Cambridge Structural Database, Version 5.31, with Aug. 2010 updates; Allen, 2002]. Interestingly, they all, including (I), have the isopropyl group of the p-cymene ligand placed approximately over the Ru—Cl bond. It appears that this feature is not due to electronic rather than steric reasons, namely least steric congestion by the P-bonded phenyl rings in the vicinity of Cl. The P-metal-P triangle in (I) adopts an exo-orientation, which turns its tip (Ru) away from the line through the centroids of the two ferrocene cyclopentadienyl rings. In the PdCl₂ and PtCl₂ complexes of Walphos-type ligands [refcodes JOFYAF and JOFJEY (Maddox et al., 2008); QODHIB, QODHOH, QODHUN, QOFRIN (Wang et al., 2008)] this triangle as part of a distorted square-planar metal-P₂Cl₂ coordination is with its tip (Pd, Pt) turned toward this line. This change in the metal position is enabled by a significant flexibility of Walphos ligands, which normally form eight-membered chelate rings. Evidence for this flexibility is provided by tetranuclear Ru cluster complexes, where Walphos ligands bridge the two Ru atoms with a P—P bite distance of ca 5.6 Å (Moberg et al., 2007), whereas in mononuclear complexes like (I) this distance is about 3.7 Å.

The crystal structure bears some pseudosymmetry because the complexes of Ru1 located near z≈ 0, 1, etc (Figs. 4 and 5) show similar orientations and spatial arrangements like the complexes of Ru2 located near z≈ 1/2, 3/2, etc, leading to a pseudo-translation of c/2. However, in closer detail the differences between the structure segements near z≈ 0 and z≈ 1/2 are considerable, as can be seen for instance by comparing the y-coordinates of Ru1 and Ru2(-x, y + 1/2, -z), 0.749937 (8) versus 0.781768 (9), corresponding to a difference of 0.50 Å, or the phenyl ring positions of Ru1 and Ru2 complexes relative to the unit cell box, e.g. along the blue z-axis (Fig. 5). Moreover, the spatial orientations of the PF₆ octahedra of P5 and P6 are entirely different and violating the c/2 pseudo-translation. Apart from this pseudosymmetry, the crystal packing of (I) bears no especially remarkable features. Both chloride ligands form only intramolecular C—H···Cl interactions and seven weak intermolecular C—H···F interactions involving mainly arene hydrogen atoms consolidate the crystal packing (Table 2).

Experimental

A suspension of [RuCl₂(p-cymene)]₂ (23.3 mg, 0.04 mmol) and silver nitrate (12.9 mg, 0.08 mmol) in methanol (2 mL) was stirred at ambient temperature for 1 h. After filtration the filtrate was added to a suspension of Walphos SL—W002–1 (50.0 mg, 0.08 mmol) in methanol (2 mL). The resulting mixture was stirred for two hours resulting in a red solution. This reaction mixture was again filtered and a solution of ammonium hexafluorophosphate (37.1 mg, 0.2 mmol) in methanol (1 mL) was added to the filtrate. Partial removal of the solvent under reduced pressure induced precipitation of the orange complex, which was filtered off, washed with cold methanol and diethyl ether and dried in vacuo (42 mg; 59%). Crystals suitable for X-ray diffraction were grown by vapour diffusion of hexane into a saturated dichloromethane solution.

¹H NMR (400 MHz, acetone-d₆): δ 0.45 (d, J = 6.8 Hz, 3H, H50), 0.99 (d, J = 7.1 Hz, 3H, H51), 1.60 (dd, J = 7.18 Hz, J = 12.21 Hz, 3H, H12), 2.17 (br s, 3H,H52), 2.21–2.30 (m, 1H, H49), 2.36 (br s, 1H, H3), 2.94 (br s, 1H, H5), 3.10 (dq, J₁ = J₂ = 7.03 Hz, 1H, H11), 3.10 (dd, J₁ = J₂ = 2.50 Hz, 1H, H4), 4.09 (s, 1H, H6–H10), 4.39 (br s, 1H, H44), 4.63 (br s, 1H, H48), 5.07 (br s, 1H, H45), 5.89 (br s, 1H, H47), 7.26–2.36 (m, 2H, H26+H30),7.36–7.43 (m, 1H, H16), 7.97–8.06 (m, 1H, H17), 8.37–8.45 (m, 1H, H14); ¹³C{¹H} NMR (100.6 MHz, CDCl₃): δ 18.5 (br s, C52), 19.2 (br s, C50), 21.7 (br d, J = 4.5 Hz, C12), 22.3 (s, C51), 28.3 (d, J = 18.4 Hz, C11), 30.9 (s, C49), 65.2 (br d, J = 2.3 Hz, C3), 65.6 (br s, C4), 70.0 (br s, 5 C, C6–C10), 71.0 (s, C5), 90.2 (br s, C2), 90.6 (br d, J = 9.1 Hz, C44), 95.6 (C1), 96.4 (s, C47), 90.6 (d, J = 4.2 Hz, C45), 126.4 (d, J = 8.8 Hz, C16), 128.4 (d, J = 8.8 Hz,2 C, Ph-meta), 128.4 (d, J = 10.3 Hz, 2 C, Ph-meta), 129.9 (d, J = 39.8 Hz, Ph-ipso),130.3 (d, J = 2.6 Hz, C15), 130.8 (d, J = 2.6 Hz, Ph-para), 131.2 (d, J = 2.3 Hz, Ph-para), 132.2 (d, J = 2.3 Hz, Ph-para), 133.0 (d, J = 2.3 Hz, Ph-para), 135.6 (d, J = 5.1 Hz, C17), 136.6 (br d, J = 13.0 Hz, 2 C, Ph-ortho), 136.7 (d, J = 44.8 Hz, Ph-ipso), 138.5 (d, J = 11.1 Hz, C13), 139.5 (br d, J = 8.7 Hz, C14), 141.6 (d, J = 44.7 Hz, Ph-ipso); ³¹P NMR (162 MHz, acetone-d₆): δ -143.0 (PF₆), 26.6 (d, J = 47.7 Hz, P1), 42.1 (d, J = 49.0 Hz, P2).