metal-organic compounds
trans-Carbonylchloridobis(tri-o-tolylphosphane-κP)rhodium(I)
aDepartment of Chemistry, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa
*Correspondence e-mail: 2011009426@ufs4life.ac.za
In the title compound, [RhCl(C21H21P)2(CO)], the coordination geometry around the RhI atom is slightly distorted square-planar with the phosphane ligands in trans positions with respect to each other. The chloride and carbonyl ligands show positional disorder, and the RhI atom lies on a center of inversion. The effective cone angle ΘE for the title compound is 169.0 (3)°. There are no significant intermolecular interactions.
Related literature
For background information, see: Angoletta (1959); Vaska & Di Luzio (1961); For a review of related compounds, see: Roodt et al. (2003). For related structures, see: Meijboom et al. (2005); Otto et al. (1999).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2007); cell SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus and XPREP (Bruker, 2007); 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).
Supporting information
https://doi.org/10.1107/S1600536811045715/pv2465sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811045715/pv2465Isup2.hkl
Compound (I) was synthesized by slow addition of 4 equivalents of tri(o-tolyl)phosphane to a dimethyl formamide solution of [RhCl(CO)2]2. After precipitation with ice water and separation of the product, it was recrystallized by slow evaporation from a 1:5 dichloromethane/hexane mixture. Analysis of the compound showed a CO stretching signal in IR at 1972 cm-1, and a signal for the phosphane ligands in 31P NMR at 25.7 p.p.m. with a JRh-P of 125.9 Hz. These signals are in good agreement with various other rhodium Vaska's complexes.
The aromatic and methyl H atoms were placed in geometrically idealized positions (C—H = 0.93 and 0.96 Å, respectively) and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(C) for aromatic, and Uiso(H) = 1.5Ueq(C) for methyl H-atoms. The highest residual electron density was located 0.87 Å from Rh1 and was essentially meaningless.
The complex first synthesized by Angoletta (1959) and later correctly formulated by Vaska (Vaska & Di Luzio, 1961), trans-[IrCl(CO)(PPh3)2] has become known under the name of the latter. This complex and its analogues have been extensively used as catalysts and model compounds (Roodt et al., 2003).
Here we report a rhodium analogue bearing o-tolyl substituents on the phosphane ligands (I). As with many of these 'Vaska complexes', compound (I) crystallized with the metal on a crystallographric centre of symmetry, leading to a 50/50 disorder for the chloride and carbonyl ligands. With this report, Vaska complexes bearing all isomers of tritolylphosphane have been described. Compound (I) crystallizes in a slightly distorted square planar geometry with the phosphane ligands in trans-position to each other (Fig. 1).
The Rh—C and Rh—Cl bonds do not show large deviations from similar complexes, showing that the steric influence of the o-methyl substituents is not so significant as to distort the coordination geometry to a large degree. However, the Rh—P bond is longer than in similar complexes, indicating that the bulky ortho-aryl substituents force the phosphane ligands away from the rhodium. A useful indicator for the steric influence of phosphane ligands is the effective cone angle ΘE. For compound (I) this angle was found to be 169.0 (3) °, significantly larger than differently substituted triarylphosphanes like tri(m-tolyl)-phosphane, for which values of 155° and 160° were reported (Meijboom et al., 2005).
For background information, see: Angoletta (1959); Vaska & Di Luzio (1961); For a review of medle compounds, See: Roodt et al. (2003). For related structures, see: Meijboom et al. (2005); Otto et al. (1999).
Data collection: APEX2 (Bruker, 2007); cell
SAINT-Plus (Bruker, 2007); data reduction: SAINT-Plus and XPREP (Bruker, 2007); 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).[RhCl(C21H21P)2(CO)] | F(000) = 800 |
Mr = 775.07 | Dx = 1.418 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2yn | Cell parameters from 6713 reflections |
a = 10.6440 (14) Å | θ = 2.3–28.1° |
b = 10.9464 (15) Å | µ = 0.67 mm−1 |
c = 15.605 (2) Å | T = 100 K |
β = 93.102 (5)° | Cuboid, yellow |
V = 1815.5 (4) Å3 | 0.30 × 0.17 × 0.12 mm |
Z = 2 |
Bruker X8 APEXII 4K KappaCCD diffractometer | 4481 independent reflections |
Radiation source: sealed tube | 3344 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.078 |
Detector resolution: 512 pixels mm-1 | θmax = 28.3°, θmin = 2.3° |
φ and ω scans | h = −12→14 |
Absorption correction: multi-scan (SADABS; Bruker, 2007) | k = −13→14 |
Tmin = 0.872, Tmax = 0.921 | l = −20→19 |
21616 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.049 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.143 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0845P)2 + 0.2003P] where P = (Fo2 + 2Fc2)/3 |
4481 reflections | (Δ/σ)max = 0.001 |
235 parameters | Δρmax = 2.35 e Å−3 |
0 restraints | Δρmin = −1.13 e Å−3 |
[RhCl(C21H21P)2(CO)] | V = 1815.5 (4) Å3 |
Mr = 775.07 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.6440 (14) Å | µ = 0.67 mm−1 |
b = 10.9464 (15) Å | T = 100 K |
c = 15.605 (2) Å | 0.30 × 0.17 × 0.12 mm |
β = 93.102 (5)° |
Bruker X8 APEXII 4K KappaCCD diffractometer | 4481 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2007) | 3344 reflections with I > 2σ(I) |
Tmin = 0.872, Tmax = 0.921 | Rint = 0.078 |
21616 measured reflections |
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.143 | H-atom parameters constrained |
S = 1.03 | Δρmax = 2.35 e Å−3 |
4481 reflections | Δρmin = −1.13 e Å−3 |
235 parameters |
Experimental. The intensity data was collected on a Bruker X8 Apex II 4 K Kappa CCD diffractometer using an exposure time of 60 s/frame. A total of 1376 frames was collected with a frame width of 0.5° covering up to θ=28.27° with 99.5% completeness accomplished. |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
C1 | 0.1009 (10) | −0.1237 (10) | 0.4794 (7) | 0.025 (2) | 0.50 |
C2 | 0.2646 (3) | 0.1270 (3) | 0.4195 (2) | 0.0193 (7) | |
C3 | 0.3138 (3) | 0.1696 (3) | 0.4992 (2) | 0.0249 (8) | |
C4 | 0.4438 (4) | 0.1739 (3) | 0.5146 (3) | 0.0294 (8) | |
H10 | 0.4765 | 0.2061 | 0.5663 | 0.035* | |
C5 | 0.5256 (4) | 0.1321 (3) | 0.4558 (3) | 0.0312 (9) | |
H6 | 0.6121 | 0.1359 | 0.4676 | 0.037* | |
C6 | 0.4771 (3) | 0.0841 (3) | 0.3786 (2) | 0.0279 (8) | |
H15 | 0.5311 | 0.0537 | 0.3389 | 0.033* | |
C7 | 0.3484 (3) | 0.0814 (3) | 0.3608 (2) | 0.0230 (7) | |
H9 | 0.3168 | 0.0488 | 0.3090 | 0.028* | |
C8 | 0.2326 (4) | 0.2095 (4) | 0.5707 (2) | 0.0345 (9) | |
H24A | 0.1527 | 0.2374 | 0.5467 | 0.052* | |
H24B | 0.2736 | 0.2747 | 0.6024 | 0.052* | |
H24C | 0.2198 | 0.1418 | 0.6083 | 0.052* | |
C9 | 0.0342 (3) | 0.2733 (3) | 0.3794 (2) | 0.0211 (7) | |
C10 | 0.1102 (4) | 0.3733 (3) | 0.4027 (2) | 0.0263 (8) | |
H22 | 0.1910 | 0.3603 | 0.4266 | 0.032* | |
C11 | 0.0664 (4) | 0.4919 (3) | 0.3905 (3) | 0.0327 (9) | |
H18 | 0.1174 | 0.5581 | 0.4062 | 0.039* | |
C12 | −0.0537 (4) | 0.5105 (3) | 0.3547 (3) | 0.0362 (10) | |
H4 | −0.0836 | 0.5897 | 0.3462 | 0.043* | |
C13 | −0.1299 (4) | 0.4121 (4) | 0.3314 (3) | 0.0319 (9) | |
H19 | −0.2102 | 0.4264 | 0.3070 | 0.038* | |
C14 | −0.0886 (3) | 0.2918 (3) | 0.3437 (2) | 0.0238 (7) | |
C15 | −0.1760 (3) | 0.1889 (4) | 0.3142 (2) | 0.0285 (8) | |
H14A | −0.1528 | 0.1600 | 0.2592 | 0.043* | |
H14B | −0.2611 | 0.2184 | 0.3097 | 0.043* | |
H14C | −0.1695 | 0.1233 | 0.3550 | 0.043* | |
C16 | 0.0791 (3) | 0.0561 (3) | 0.2837 (2) | 0.0188 (7) | |
C17 | 0.1169 (3) | 0.1212 (3) | 0.2114 (2) | 0.0222 (7) | |
C18 | 0.0976 (3) | 0.0660 (4) | 0.1308 (2) | 0.0271 (8) | |
H23 | 0.1215 | 0.1074 | 0.0822 | 0.033* | |
C19 | 0.0436 (4) | −0.0488 (4) | 0.1218 (2) | 0.0305 (8) | |
H17 | 0.0326 | −0.0838 | 0.0676 | 0.037* | |
C20 | 0.0061 (3) | −0.1115 (3) | 0.1923 (2) | 0.0286 (8) | |
H13 | −0.0311 | −0.1880 | 0.1858 | 0.034* | |
C21 | 0.0239 (3) | −0.0601 (3) | 0.2729 (2) | 0.0235 (7) | |
H5 | −0.0008 | −0.1029 | 0.3206 | 0.028* | |
C22 | 0.1748 (4) | 0.2474 (3) | 0.2150 (2) | 0.0273 (8) | |
H16A | 0.2179 | 0.2619 | 0.1635 | 0.041* | |
H16B | 0.2334 | 0.2529 | 0.2638 | 0.041* | |
H16C | 0.1098 | 0.3073 | 0.2200 | 0.041* | |
O1 | 0.1652 (12) | −0.2035 (10) | 0.4677 (9) | 0.030 (3) | 0.50 |
P1 | 0.09397 (8) | 0.11591 (8) | 0.39409 (6) | 0.0182 (2) | |
Cl1 | 0.1376 (3) | −0.1671 (3) | 0.4666 (2) | 0.0226 (7) | 0.50 |
Rh1 | 0.0000 | 0.0000 | 0.5000 | 0.01825 (13) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.029 (6) | 0.018 (6) | 0.027 (5) | −0.004 (4) | 0.001 (4) | −0.004 (4) |
C2 | 0.0171 (15) | 0.0122 (15) | 0.0287 (17) | −0.0030 (12) | 0.0015 (13) | 0.0071 (13) |
C3 | 0.0302 (19) | 0.0125 (16) | 0.0319 (19) | −0.0026 (14) | 0.0020 (15) | 0.0026 (14) |
C4 | 0.0285 (19) | 0.0198 (19) | 0.039 (2) | −0.0063 (15) | −0.0085 (16) | 0.0042 (16) |
C5 | 0.0226 (18) | 0.023 (2) | 0.048 (2) | −0.0048 (15) | −0.0030 (16) | 0.0143 (17) |
C6 | 0.0220 (17) | 0.0217 (19) | 0.040 (2) | 0.0005 (14) | 0.0065 (15) | 0.0088 (16) |
C7 | 0.0245 (17) | 0.0132 (16) | 0.0314 (19) | −0.0003 (13) | 0.0024 (14) | 0.0032 (14) |
C8 | 0.037 (2) | 0.037 (2) | 0.029 (2) | −0.0065 (18) | 0.0011 (16) | −0.0055 (17) |
C9 | 0.0238 (17) | 0.0160 (16) | 0.0244 (17) | −0.0018 (13) | 0.0089 (13) | 0.0005 (14) |
C10 | 0.0303 (19) | 0.0183 (18) | 0.0309 (19) | −0.0033 (15) | 0.0083 (15) | −0.0002 (15) |
C11 | 0.041 (2) | 0.0162 (18) | 0.042 (2) | −0.0027 (16) | 0.0131 (18) | −0.0035 (16) |
C12 | 0.045 (2) | 0.020 (2) | 0.046 (2) | 0.0091 (17) | 0.016 (2) | 0.0019 (17) |
C13 | 0.032 (2) | 0.025 (2) | 0.040 (2) | 0.0087 (16) | 0.0080 (16) | 0.0019 (17) |
C14 | 0.0231 (17) | 0.0233 (18) | 0.0259 (18) | 0.0018 (14) | 0.0097 (14) | 0.0017 (14) |
C15 | 0.0215 (17) | 0.031 (2) | 0.033 (2) | 0.0027 (15) | 0.0019 (14) | 0.0020 (16) |
C16 | 0.0165 (15) | 0.0171 (17) | 0.0228 (16) | 0.0001 (13) | 0.0013 (12) | −0.0004 (14) |
C17 | 0.0179 (16) | 0.0210 (18) | 0.0279 (18) | 0.0032 (13) | 0.0036 (13) | 0.0002 (14) |
C18 | 0.0267 (18) | 0.029 (2) | 0.0256 (18) | 0.0086 (16) | 0.0012 (14) | 0.0007 (15) |
C19 | 0.030 (2) | 0.031 (2) | 0.030 (2) | 0.0074 (17) | −0.0033 (15) | −0.0135 (17) |
C20 | 0.0250 (18) | 0.0208 (18) | 0.040 (2) | 0.0014 (15) | −0.0034 (15) | −0.0072 (16) |
C21 | 0.0197 (16) | 0.0218 (19) | 0.0292 (18) | 0.0033 (14) | 0.0028 (13) | 0.0007 (15) |
C22 | 0.0302 (19) | 0.0255 (19) | 0.0268 (19) | −0.0044 (15) | 0.0079 (15) | 0.0041 (15) |
O1 | 0.028 (5) | 0.020 (6) | 0.041 (4) | 0.007 (4) | 0.011 (4) | 0.006 (4) |
P1 | 0.0184 (4) | 0.0132 (4) | 0.0233 (4) | −0.0029 (3) | 0.0037 (3) | −0.0007 (3) |
Cl1 | 0.025 (2) | 0.016 (2) | 0.0269 (13) | 0.0042 (13) | 0.0070 (13) | 0.0036 (16) |
Rh1 | 0.01767 (19) | 0.0145 (2) | 0.0230 (2) | −0.00172 (14) | 0.00487 (14) | 0.00057 (14) |
C1—Cl1 | 0.654 (9) | C13—C14 | 1.399 (5) |
C1—O1 | 1.131 (11) | C13—H19 | 0.9300 |
C1—Rh1 | 1.769 (11) | C14—C15 | 1.516 (5) |
C2—C3 | 1.402 (5) | C15—H14A | 0.9600 |
C2—C7 | 1.405 (5) | C15—H14B | 0.9600 |
C2—P1 | 1.842 (3) | C15—H14C | 0.9600 |
C3—C4 | 1.393 (5) | C16—C21 | 1.408 (5) |
C3—C8 | 1.513 (5) | C16—C17 | 1.411 (5) |
C4—C5 | 1.377 (6) | C16—P1 | 1.841 (3) |
C4—H10 | 0.9300 | C17—C18 | 1.401 (5) |
C5—C6 | 1.387 (5) | C17—C22 | 1.513 (5) |
C5—H6 | 0.9300 | C18—C19 | 1.386 (6) |
C6—C7 | 1.383 (5) | C18—H23 | 0.9300 |
C6—H15 | 0.9300 | C19—C20 | 1.373 (6) |
C7—H9 | 0.9300 | C19—H17 | 0.9300 |
C8—H24A | 0.9600 | C20—C21 | 1.382 (5) |
C8—H24B | 0.9600 | C20—H13 | 0.9300 |
C8—H24C | 0.9600 | C21—H5 | 0.9300 |
C9—C10 | 1.398 (5) | C22—H16A | 0.9600 |
C9—C14 | 1.407 (5) | C22—H16B | 0.9600 |
C9—P1 | 1.846 (4) | C22—H16C | 0.9600 |
C10—C11 | 1.389 (5) | P1—Rh1 | 2.3496 (10) |
C10—H22 | 0.9300 | Cl1—Rh1 | 2.418 (3) |
C11—C12 | 1.383 (7) | Rh1—C1i | 1.769 (11) |
C11—H18 | 0.9300 | Rh1—P1i | 2.3496 (10) |
C12—C13 | 1.385 (6) | Rh1—Cl1i | 2.418 (3) |
C12—H4 | 0.9300 | ||
Cl1—C1—Rh1 | 172.6 (14) | H14A—C15—H14C | 109.5 |
O1—C1—Rh1 | 178.8 (14) | H14B—C15—H14C | 109.5 |
C3—C2—C7 | 118.4 (3) | C21—C16—C17 | 119.7 (3) |
C3—C2—P1 | 122.0 (3) | C21—C16—P1 | 116.6 (2) |
C7—C2—P1 | 119.3 (3) | C17—C16—P1 | 123.7 (3) |
C4—C3—C2 | 119.0 (3) | C18—C17—C16 | 117.8 (3) |
C4—C3—C8 | 117.7 (3) | C18—C17—C22 | 117.8 (3) |
C2—C3—C8 | 123.3 (3) | C16—C17—C22 | 124.4 (3) |
C5—C4—C3 | 122.1 (4) | C19—C18—C17 | 121.4 (3) |
C5—C4—H10 | 119.0 | C19—C18—H23 | 119.3 |
C3—C4—H10 | 119.0 | C17—C18—H23 | 119.3 |
C4—C5—C6 | 119.0 (3) | C20—C19—C18 | 120.6 (3) |
C4—C5—H6 | 120.5 | C20—C19—H17 | 119.7 |
C6—C5—H6 | 120.5 | C18—C19—H17 | 119.7 |
C7—C6—C5 | 120.0 (4) | C19—C20—C21 | 119.6 (4) |
C7—C6—H15 | 120.0 | C19—C20—H13 | 120.2 |
C5—C6—H15 | 120.0 | C21—C20—H13 | 120.2 |
C6—C7—C2 | 121.2 (3) | C20—C21—C16 | 120.9 (3) |
C6—C7—H9 | 119.4 | C20—C21—H5 | 119.6 |
C2—C7—H9 | 119.4 | C16—C21—H5 | 119.6 |
C3—C8—H24A | 109.5 | C17—C22—H16A | 109.5 |
C3—C8—H24B | 109.5 | C17—C22—H16B | 109.5 |
H24A—C8—H24B | 109.5 | H16A—C22—H16B | 109.5 |
C3—C8—H24C | 109.5 | C17—C22—H16C | 109.5 |
H24A—C8—H24C | 109.5 | H16A—C22—H16C | 109.5 |
H24B—C8—H24C | 109.5 | H16B—C22—H16C | 109.5 |
C10—C9—C14 | 120.2 (3) | C16—P1—C2 | 105.01 (15) |
C10—C9—P1 | 120.5 (3) | C16—P1—C9 | 101.78 (16) |
C14—C9—P1 | 119.3 (3) | C2—P1—C9 | 107.12 (15) |
C11—C10—C9 | 120.7 (4) | C16—P1—Rh1 | 116.59 (11) |
C11—C10—H22 | 119.6 | C2—P1—Rh1 | 109.66 (11) |
C9—C10—H22 | 119.6 | C9—P1—Rh1 | 115.72 (11) |
C12—C11—C10 | 119.3 (4) | C1—Rh1—C1i | 180.000 (2) |
C12—C11—H18 | 120.4 | C1—Rh1—P1i | 90.0 (4) |
C10—C11—H18 | 120.4 | C1i—Rh1—P1i | 90.0 (4) |
C11—C12—C13 | 120.5 (4) | C1—Rh1—P1 | 90.0 (4) |
C11—C12—H4 | 119.8 | C1i—Rh1—P1 | 90.0 (4) |
C13—C12—H4 | 119.8 | P1i—Rh1—P1 | 180.0 |
C12—C13—C14 | 121.4 (4) | C1—Rh1—Cl1 | 2.0 (4) |
C12—C13—H19 | 119.3 | C1i—Rh1—Cl1 | 178.0 (4) |
C14—C13—H19 | 119.3 | P1i—Rh1—Cl1 | 91.66 (10) |
C13—C14—C9 | 117.9 (3) | P1—Rh1—Cl1 | 88.34 (10) |
C13—C14—C15 | 118.3 (3) | C1—Rh1—Cl1i | 178.0 (4) |
C9—C14—C15 | 123.7 (3) | C1i—Rh1—Cl1i | 2.0 (4) |
C14—C15—H14A | 109.5 | P1i—Rh1—Cl1i | 88.34 (10) |
C14—C15—H14B | 109.5 | P1—Rh1—Cl1i | 91.66 (10) |
H14A—C15—H14B | 109.5 | Cl1—Rh1—Cl1i | 180.00 (18) |
C14—C15—H14C | 109.5 |
Symmetry code: (i) −x, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [RhCl(C21H21P)2(CO)] |
Mr | 775.07 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 100 |
a, b, c (Å) | 10.6440 (14), 10.9464 (15), 15.605 (2) |
β (°) | 93.102 (5) |
V (Å3) | 1815.5 (4) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.67 |
Crystal size (mm) | 0.30 × 0.17 × 0.12 |
Data collection | |
Diffractometer | Bruker X8 APEXII 4K KappaCCD |
Absorption correction | Multi-scan (SADABS; Bruker, 2007) |
Tmin, Tmax | 0.872, 0.921 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 21616, 4481, 3344 |
Rint | 0.078 |
(sin θ/λ)max (Å−1) | 0.666 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.143, 1.03 |
No. of reflections | 4481 |
No. of parameters | 235 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 2.35, −1.13 |
Computer programs: APEX2 (Bruker, 2007), SAINT-Plus (Bruker, 2007), SAINT-Plus and XPREP (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2008), WinGX (Farrugia, 1999).
Acknowledgements
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.
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The complex first synthesized by Angoletta (1959) and later correctly formulated by Vaska (Vaska & Di Luzio, 1961), trans-[IrCl(CO)(PPh3)2] has become known under the name of the latter. This complex and its analogues have been extensively used as catalysts and model compounds (Roodt et al., 2003).
Here we report a rhodium analogue bearing o-tolyl substituents on the phosphane ligands (I). As with many of these 'Vaska complexes', compound (I) crystallized with the metal on a crystallographric centre of symmetry, leading to a 50/50 disorder for the chloride and carbonyl ligands. With this report, Vaska complexes bearing all isomers of tritolylphosphane have been described. Compound (I) crystallizes in a slightly distorted square planar geometry with the phosphane ligands in trans-position to each other (Fig. 1).
The Rh—C and Rh—Cl bonds do not show large deviations from similar complexes, showing that the steric influence of the o-methyl substituents is not so significant as to distort the coordination geometry to a large degree. However, the Rh—P bond is longer than in similar complexes, indicating that the bulky ortho-aryl substituents force the phosphane ligands away from the rhodium. A useful indicator for the steric influence of phosphane ligands is the effective cone angle ΘE. For compound (I) this angle was found to be 169.0 (3) °, significantly larger than differently substituted triarylphosphanes like tri(m-tolyl)-phosphane, for which values of 155° and 160° were reported (Meijboom et al., 2005).