trans-Carbonyl­chloridobis[tris­(4-meth­oxy­phen­yl)phosphane-κP]rhodium(I)

Stefan Warsink; Andreas Roodt

doi:10.1107/S1600536811046150

. 2011 Nov 5;67(Pt 12):m1695–m1696. doi: 10.1107/S1600536811046150

trans-Carbonylchloridobis[tris(4-methoxyphenyl)phosphane-κP]rhodium(I)

Stefan Warsink ^a,^*, Andreas Roodt ^a

PMCID: PMC3238621 PMID: 22199512

Abstract

The title complex, [RhCl(C₂₁H₂₁O₃P)₂(CO)], is a rhodium analogue to Vaska’s complex with para-methoxy substituents on the six phosphanyl–aryl units. Two independent molecules are present in the unit cell, with their metal atoms both located on an inversion centre. This causes the chloride and carbonyl ligands to exhibit a positional disorder in a 0.5:0.5 ratio. The two Rh^I atoms exhibit a distorted square-planar geometry. There are a few weak intramolecular C—H⋯X interactions (X = O, Cl). Interestingly, no significant intermolecular interactions are found between the two independent molecules.

Related literature

For background to Vaska’s complex, see: Angoletta (1959 ▶); Vaska & Di Luzio (1961 ▶). For related literature on rhodium Vaska complexes, see: Basson et al. (1990 ▶); Clarke et al. (2002 ▶); Kemp et al. (1995 ▶); Rheingold & Geib (1987 ▶); Roodt et al. (2003 ▶); Wilson et al. (2002 ▶). For similar complexes, see: Burgoyne et al. (2010 ▶), Meijboom et al. (2006 ▶), Monge et al. (1983 ▶); Otto et al. (1999 ▶). Synthetic details are given in McCleverty & Wilkinson (1990 ▶).

Experimental

Crystal data

[RhCl(C₂₁H₂₁O₃P)₂(CO)]
M _r = 871.07
Triclinic,
a = 7.8350 (4) Å
b = 12.3151 (8) Å
c = 21.0591 (13) Å
α = 90.995 (2)°
β = 99.591 (2)°
γ = 101.220 (2)°
V = 1962.7 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.64 mm⁻¹
T = 100 K
0.24 × 0.16 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2004 ▶) T _min = 0.887, T _max = 0.937
26016 measured reflections
9327 independent reflections
6401 reflections with I > 2σ(I)
R _int = 0.098

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.144
S = 1.04
9327 reflections
517 parameters
H-atom parameters constrained
Δρ_max = 2.45 e Å⁻³
Δρ_min = −1.17 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT-Plus (Bruker, 2004 ▶); data reduction: SAINT-Plus and XPREP (Bruker, 2004 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811046150/wm2548sup1.cif

e-67-m1695-sup1.cif^{(46.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811046150/wm2548Isup2.hkl

e-67-m1695-Isup2.hkl^{(447KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Rh1—C1	1.699 (12)
Rh1—P1	2.3257 (10)
Rh1—Cl1	2.416 (5)
Rh2—C23	1.751 (11)
Rh2—P2	2.3321 (11)
Rh2—Cl2	2.410 (4)
C1—O1	1.157 (18)
C23—O5	1.171 (13)

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C1—Rh1—P1	90.5 (4)
P1—Rh1—Cl1	91.20 (9)
C23—Rh2—P2	91.9 (4)
P2—Rh2—Cl2	92.06 (10)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C14—H046⋯Cl1	0.95	2.81	3.191 (5)	105
C32—H021⋯Cl2	0.95	2.82	3.157 (5)	102
C8—H04A⋯Cl1ⁱ	0.98	2.73	3.693 (7)	169
C8—H04A⋯O1ⁱ	0.98	2.52	3.486 (18)	168

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank SASOL, the South African NRF and THRIP and the University of the Free State Research Fund for financial support. The views expressed do not necessarily represent that of the NRF.

supplementary crystallographic information

Comment

Vaska's complex was first synthesized by Angoletta (1959) and later correctly formulated as trans-[IrCl(CO)(PPh₃)₂] (Vaska & Di Luzio, 1961). This compound has been used in various catalytic processes and it or its analogues are often employed as model compounds (Rheingold & Geib, 1987; Basson et al., 1990; Kemp et al., 1995; Roodt et al., 2003).

Various 'Vaska complexes' have been synthesized, exploring different metals but especially introducing different substituents on the phosphane ligands. These modifications have an impact on the steric hindrance around the metal (Clarke et al., 2002; Wilson et al., 2002), but in the case of para-substituted triaryl phosphanes the effect is purely electronic (Monge et al., 1983; Otto et al., 1999; Meijboom et al., 2006; Burgoyne et al., 2010). Since only limited data are available on this kind of complexes, we have prepared the rhodium analogue (I), [RhCl(C₂₁H₂₁O₃P)₂(CO)], bearing relatively electron-rich tri(para-methoxyphenyl)-phosphane ligands.

Two independent half-molecules are present in the asymmetric unit of compound (I), in each case with the Rh^I atoms located on inversion centres. The metal atoms display a distorted square planar geometry with the phosphane ligands located in mutual trans-positions (Fig. 1). Selected bond lenghts and angles are presented in Table 1.

The carbonyl moiety has a slightly bent geometry, with Rh—C—O angles of 173.2 (14)° and 176.8 (16)° for the two molecules, respectively. In solution infrared spectroscopy only one signal was observed for the carbonyl ligand at 1974 cm^-1. Also in solid state infrared spectroscopy of the amorphous material, only one signal was observed at 1964 cm^-1. Only when a crystalline sample was analysed, two signals were observed at 1956 and 1973 cm^-1, showing the stretching vibrations of both the independent carbonyl ligands. In ³¹P NMR the signal for the phospine ligands was observed at 24.95 ppm with a J_Rh—P of 124.5 Hz, which is in line with analogous complexes.

The Rh—P bond lengths fall in the range of other, analogous rhodium Vaska complexes. In contrast, the bonds of the metal to the carbonyl and chlorido ligands are significantly influenced by the electron-donating phosphane ligands. The bond to the chlorido ligand is the longest reported for this kind of complexes bearing triaryl phosphanes. The same influence is also notably present in the bonding of the carbonyl ligand. Its bond to the rhodium atom is quite short, which indicates significant metal-to-ligand electron donation. As a consequence, the C—O bond is lengthened.

There are a few weak intramolecular C—H···X interactions (X = O, Cl), which are listed in Table 2. Interestingly, no intermolecular interactions are found between the two independent molecules.

Experimental

Compound (I) was synthesized by slowly adding 4 equivalents of tri(4-methoxyphenyl)phosphane to a dimethyl formamide solution of [RhCl(CO)₂]₂ (McCleverty & Wilkinson, 1990). The product was precipitated with ice water and isolated by filtration. Crystallization was performed by dissolving the complex in a small amount of dichloromethane which was then carefully layered with approximately 5 volumetric equivalents of hexane. The mixture was stored in a loosely closed vessel, from which yellow crystals precipitated.