Chlorido[1-(2-oxidophen­yl)ethyl­idene][tris­(3,5-dimethyl­pyrazol-1-yl)hydro­borato]iridium(III) chloro­form monosolvate

Laura L Santos; Margarita Paneque; Kurt Mereiter

doi:10.1107/S1600536813007344

. 2013 Mar 23;69(Pt 4):m224–m225. doi: 10.1107/S1600536813007344

Chlorido[1-(2-oxidophenyl)ethylidene][tris(3,5-dimethylpyrazol-1-yl)hydroborato]iridium(III) chloroform monosolvate

Laura L Santos ^a, Margarita Paneque ^a, Kurt Mereiter ^b,^*

PMCID: PMC3629499 PMID: 23634017

Abstract

In the title compound, [Ir(C₁₅H₂₂BN₆)(C₈H₇O)Cl]·CHCl₃, the Ir atom is formally trivalent and is coordinated in a slightly distorted octahedral geometry by three facial N atoms, one C atom, one O atom and one Cl atom. The Ir=C_carbene bond is strong and short and exerts a notable effect on the trans-Ir—N bond, which is about 0.10 Å longer than the two other Ir—N bonds. The chloroform solvent molecule is anchored via a weak C—H⋯Cl hydrogen bond to the Cl atom of the Ir complex molecule. In the crystal, the constituents adopt a layer-like arrangement parallel to (010) and are held together by weak intermolecular C—H⋯Cl hydrogen bonds, as well as weak Cl⋯Cl [3.498 (2) Å] and Cl⋯π [3.360 (4) Å] interactions. A weak intramolecular C—H⋯O hydrogen bond is also observed.

Related literature

The title compound represents a well crystallizing air-stable chloroform solvate of a mononuclear iridium complex based on the (hydrogen tris(3,5-dimethylpyrazolyl)borate-N,N′,N′′)-iridium moiety Ir[Tp^Me2]. Its formation from [(Tp^Me2)Ir(C₆H₅)₂(k ¹-N₂)] (C₆H₅ = phenyl, N₂ = dinitrogen) and ethoxybenzene involved multiple C—C,H,O,Cl bond transformations by the outstanding activity of the Ir[Tp^Me2] moiety. For general information on C—H and C—C activation, see: Lin & Yamamoto (1999 ▶); Dyker (1999 ▶); Labinger & Bercaw (2002 ▶). For C—H bond activation reactions of ethers by Ir[Tp^Me2] complexes, see: Lara et al. (2009 ▶); Conejero et al. (2010 ▶); Santos et al. (2013 ▶). For the synthesis of the complex and related crystal structures, see: Gutiérrez-Puebla et al. (1998 ▶); Lara et al. (2009 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

[Ir(C₁₅H₂₂BN₆)(C₈H₇O)Cl]·CHCl₃
M _r = 763.35
Monoclinic,
a = 10.1271 (4) Å
b = 19.1711 (8) Å
c = 14.3154 (6) Å
β = 91.956 (2)°
V = 2777.7 (2) Å³
Z = 4
Mo Kα radiation
μ = 5.22 mm⁻¹
T = 173 K
0.32 × 0.15 × 0.10 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2003 ▶) T _min = 0.343, T _max = 0.593
52411 measured reflections
8053 independent reflections
6999 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.028
wR(F ²) = 0.071
S = 1.02
8053 reflections
341 parameters
H-atom parameters constrained
Δρ_max = 1.29 e Å⁻³
Δρ_min = −1.43 e Å⁻³

Data collection: SMART (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2003 ▶); data reduction: SAINT; 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

Click here for additional data file.^{(27.3KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536813007344/lh5594sup1.cif

e-69-0m224-sup1.cif^{(27.3KB, cif)}

Click here for additional data file.^{(394KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813007344/lh5594Isup2.hkl

e-69-0m224-Isup2.hkl^{(394KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Ir1—C22	1.937 (3)
Ir1—N3	2.056 (3)
Ir1—N1	2.059 (3)
Ir1—O1	2.063 (2)
Ir1—N5	2.155 (3)
Ir1—Cl1	2.3500 (8)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C24—H24⋯Cl1	1.00	2.55	3.488 (5)	156
C11—H11A⋯O1	0.98	2.37	3.230 (4)	146
C11—H11C⋯Cl3ⁱ	0.98	2.65	3.609 (4)	166

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Symmetry code: (i) Inline graphic .

Acknowledgments

Financial support (FEDER) from the Spanish Ministry of Science (projects CTQ2010–17476 and Consolider-Ingenio 2010 CSD2007–00006) and the Junta de Andalucía (grant FQM-119 and project P09-FQM-4832) is acknowedged.

supplementary crystallographic information

Comment

Transition metal compounds capable of inducing C—H bond activation and subsequent C—C bond formation have important applications in the synthesis of complex organic molecules from simple, commonly available substrates (Lin & Yamamoto, 1999; Dyker, 1999; Labinger & Bercaw, 2002). Iridium complexes with hydrogen-tris(pyrazolyl)borate as a stabilizing ligand and labile coordination sites have been found to show an outstanding potential at this respect (Conejero et al., 2010). Part of our work in this field has derived from the study of reactions of ethers with reactive Ir complexes coordinated by the hydrogen-tris(3,5-dimethylpyrazolyl)borate ligand (Tp^Me2) (Lara et al., 2009; Conejero et al., 2010; Santos et al., 2013). When the complex [(Tp^Me2)Ir(C₆H₅)₂(k¹-N₂)] (C₆H₅ = phenyl, N₂ = dinitrogen; Gutiérrez-Puebla et al., 1998) and C₆H₅OCH₂CH₃ (ethoxybenzene) are heated to 333K in cyclohexane a mixture of three compounds is formed (see reaction scheme Fig. 3). The major reaction product is 2, the precursor of the title complex 1. Compound 2 is a hydride-alkylidene whose formation requires multiple C—H bond activations, C—O bond cleavage and C—C bond formation. The other reaction products are a heteroatom-stabilized hydride-carbene 3 derived from three C—H activations of the organic product, and the minor reaction product 4 (ca 5%), which is the hydride-alkene tautomer of 2. Compound 2 could be prepared independently in nearly quantitative yield (~95%) by the reaction of [(Tp^Me2)Ir(C₆H₅)₂(k¹-N₂)] with 2-ethylphenol (Lara et al., 2009). Compound 2 is stable at room temperature but at higher temperatures is in equilibrium with compound 4. On the other hand, if 2 is heated in chloroform at 353K for 4 days, a C—Cl bond activation takes place whereby the hydride is exchanged against a Cl atom under concomitant formation of dichloromethane. The resulting complex 1 (Fig. 3) crystallizes from the excess of CHCl₃ under formation of the title compound, an air-stable solvate 1.CHCl₃, (I). In 1 the iridium atom exhibits a relatively regular octahedral coordination by three pyrazole nitrogen atoms, the carbene atom C22, the phenolate oxygen O1, and the chloride ligand Cl1 (Fig. 1). The cis bond angles about Ir vary from 82.18 (12)° (C22—Ir1—O1) to 98.38 (13)° (C22—Ir1—N3) and the trans bond angles from 173.11 (8)° to 177.55 (9)° (N3—Ir1—O1). The metal-carbene bond Ir1—C22 = 1.937 (3) Å is characteristically short and in good accord with Ir-carbene bonds of well refined crystal structures in the Cambridge Structural Database (version 5.33; Allen, 2002), which gave a mean value of 1.942 (64) Å for 57 crystal structures with 69 bonds. The Ir—N bonds (Table 1) show a typical elongation of ca 0.1 Å for the bond Ir1—N5 trans to the carbene ligand. The Ir—O and Ir—Cl bonds adopt normal values (Allen et al., 1987). Bond lengths and angles in the Tp^Me2 ligand compare well with related complexes (e.g.: Lara et al., 2009; Santos et al., 2013). The chelate ring formed by the carbene ligand has a flat envelope conformation with O1—C16—C21—C22 perfectly planar (r.m.s. deviation from planarity 0.0002 Å) and Ir1 displaced from this plane by -0.352 (5) Å whereas the terminal methyl carbon C23 is 0.419 (7) Å off from this plane. The carbene atom C22 has a very flat pyramidal coordination and deviates by -0.064 (4) Å from the plane defined by Ir1, C21, and C23. In the crystal structure the Ir complexes 1 and the CHCl₃ molecules are organized in a layer-like fashion parallel to (010) as shown in Fig. 2. Such layers are centered at y≈ 1/4; and y≈ 3/4;. The CHCl₃ molecule is anchored in the structure via a pronounced C—H···Cl hydrogen bond (C···Cl = 3.360 (4) Å) to the Cl1 atom of the Ir complex (Fig. 1 and Table 2). It is moreover fixed by the interaction C11—H11c···Cl3 [C11(x,1/2 - y,1/2 + z)···Cl3 = 3.608 (4) Å], by the halogen-halogen contact Cl3···Cl1(x,1/2 - y,1/2 + z) = 3.498 (2) Å, and two side-on contacts between the π-orbitals of arene rings and Cl [Cl2 with pyrazole ring 1 and the shortest contact distance Cl2···C4(x - 1,y,z) = 3.360 (4) Å; Cl3 with the phenyl ring and the shortest contact distance Cl3···C20 = 3.396 (4) Å]. These interactions are included in Fig. 2. Interactions between the Ir complexes are unremarkable and consist essentially of van der Waals contacts. The interaction C11—H11a···O3 is intramolecular.

Experimental

A solution of 2 (0.030 g, 0.049 mmol; see Fig. 3; for synthesis see Lara et al., 2009) in CHCl₃ (3 ml) was stirred at 353K for 4 days. After this time the solvent was removed under reduced pressure. NMR spectra of the crude product revealed the presence of complex 1 in 70% spectroscopic yield. Crystallization from pentane/CH₂Cl₂/CHCl₃ at 253K gave compound 1 as a dark green microcrystalline solid. ¹H NMR (CDCl₃, 298 K) δ 7.47, 7.28, 7.19, 6.60 (dd, ddd, d, ddd, 1 H each, ³J_HH≈ 8.5, ⁴J_HH≈1 Hz, 4 CH_ar), 5.89, 5.88, 5.50 (s, 1 H each, 3 CH_pz), 3.07 (s, 3 H, Ir═CCH₃), 2.77, 2.49, 2.40, 2.36, 2.32, 1.32 (s, 3 H each, 6 Me_pz). ¹³C{¹H} NMR (CDCl₃, 25 °C) δ 273.2(Ir═C), 192.5 (Ir—O—C), 154.7, 153.8, 153.3, 152.3, 144.6, 144.2, 144.1 (Ir ═ C-C + C_qpz), 141.0, 124.2, 119.7, 115.7 (CH_ar), 108.4, 108.3, 108.2 (CH_pz), 34.0 (Ir=CCH₃), 16.4, 14.1, 13.1, 13.0, 12.4, 12.2 (Me_pz). Crystals of 1.CHCl₃ for X-ray diffraction were obtained by recrystallization from CHCl₃/pentane.