trans-Chloro­(methyl)­bis­(tri­cyclo­hexyl­phosphine)­platinum(II)

The crystal structure of the title compound, [PtCl(CH₃)(C₁₈H₃₃P)₂], is isostructural with various platinum(II) and palladium(II) complexes containing two bulky tri­cyclo­hexyl­phosphine ligands in a trans orientation. The Pt atom resides on an inversion centre, resulting in a 50% statistical disorder in the chloro and methyl positions. The most significant geometrical parameters are Pt-P 2.3431 (8), Pt-­Cl 2.440 (4) and Pt-C1 2.179 (13) Å, and P-Pt-P 180, P-Pt-Cl 89.15 (12) and 90.85 (12), and C-Pt-Cl 172.7 (5)°. The effective and Tolman cone angles for the tricyclohexylphosphine ligands were calculated as 160 and 162°, respectively.

S1. Comment

As part of a systematic investigation involving complexes with the general formula trans-[MMeCl(L)₂] (M = Pt or Pd, L = tertiary phosphine or arsine ligands), crystals of the title compound, (I), were obtained. \sch

The Pt atom lies on an inversion centre resulting in a 50% statistical disorder in the chloro- and methyl positions while the phosphine ligands are in a trans orientation with an 180° angle due to the symmetry requirements. All angles within the Pt coordination sphere are close to that expected for an ideal square planar environment with the P—Pt—Cl angles 89.15 (12) and 90.85 (12)°, while the P—Pt—C1 angles were determined as 89.8 (4) and 90.2 (4)°, respectively. The C1—Pt—Cl angle of 172.7 (5)°, however, deviates quite substantially from 180° while the angle between the disordered ligands, i.e. Cl—Pt—C1' or C1—Pt—Cl' was determined as 7.3 (5)°. The Pt—P and Pt—Cl bond distances of 2.3431 (8) and 2.440 (4) Å are within normal ranges for a complex containing large phosphine ligands and a strong labilizing group, such as Me, trans to the Cl ligand. The Pt—C1 bond distance of 2.179 (13) Å is slightly longer than expected and may be an artifact of the disorder between the methyl and chloro ligands, a conclusion confirmed by the large uncertainty associated with this specific bond.

All three of the cyclohexyl substituents of the phosphine ligands adopt the expected chair conformation for saturated six-membered rings and are exactly staggered with respect to the trans phosphine due to the inversion centre at the Pt position. The average tetrahedral angles around the P atom of 104.87 (16) and 113.65 (12)° for C—P—C and C—P—Pt, respectively, indicate that the substituents are slightly compressed towards each other as is normally encountered in coordinated phosphine ligands.

Measuring the spatial impact of a ligand in a coordination complex is an issue that attracted much interest in the past and will continue to do so in future as the existing models are refined and new models are introduced. One such model and probably the most generally recognized measure of steric size of phosphine ligands is the Tolman cone angle (Tolman, 1977). In this regard it has been noted before that the flexiblity of the PCy₃ ligand allows several conformers of the cyclohexyl groups to exist leading to values for the Tolman cone angle ranging from 163° for trans-[Pt(I)₂(PCy₃)₂] (Alcock & Leviston, 1974; Ferguson et al., 1978) up to the 181° determined in [Hg(NO₃)₂(PCy₃)₂] (Alyea et al., 1977). In this study the cone angle calculations were done based on Tolman's model using C—H bond distances of 0.97 Å and a van der Waals radius of hydrogen of 1.2 Å. The effective cone angle is calculated in a similar way as the Tolman cone angle but using the actual Pt—P bond distance as determined from crystallography while a fixed distance of 2.28 Å is used for the Tolman cone angle calculations. Values of 160 and 162° were calculated for the effective- and Tolman cone angles, respectively. Both these values are very similar to the 163° determined for the isostructural trans-[Pt(I)₂(PCy₃)₂] complex as mentioned above.

In Table 2, the title compound is compared with other closely related Ni^II, Pd^II and Pt^II complexes from the literature containing two bulky tricyclohexylphosphine ligands in a trans orientation. The compound was found to be isostructural to several of these complexes as indicated showing that the crystal packing is predominantly determined by the tricyclohexylphosphine ligands and only when the metal core is drastically influenced as by the introduction of a Ph or H ligand are the packing modes changed.

In Table 3, the title compound is compared with related trans-[MMeCl(L)₂] (M = Pd or Pt, L = P or As ligands) complexes illustrating the effect of different phosphine and arsine ligands on the geometrical parameters. The Pt—P bond distance of 2.3431 (8) Å is comparably longer than the other M—P bond distances - even longer than in the PdPPh₂Fc complex that also contains a bulky phosphine ligand. This can, in addition to the large size of PCy₃, also be due to the strong electron-donating capability of this ligand causing a mutual labilization when occupying positions trans to each other. The Pt—Cl bond distance of 2.440 (4) Å is also slightly longer than in the related complexes and is probably a combination of steric crowding and an electron rich metal centre. Although the Pd—L bond lengths seem to be slightly longer than in the corresponding Pt—L complexes this effect is not as evident in the M—Cl bonds.

S2. Experimental

[PtMeCl(COD)] was prepared according to literature procedures (Clark & Manzer, 1973). To a solution of [PtMeCl(COD)] (50 mg, 0.14 mmol) in dichloromethane (10 ml) was added PCy₃ (98 mg, 0.35 mmol) dissolved in dichloromethane (8 ml). Slow evaporation of this solution yielded colourless crystals suitable for X-ray analysis. ¹H NMR (CDCl₃) δ: 0.28 (t, 3H, ³J_P—H = 11 Hz, ²J_Pt—H = 84 Hz), 2.6–1.2 (m, 66H). ³¹P NMR (CDCl₃) δ 21.9 (t, ¹J_Pt—P = 2822 Hz).

S3. Refinement

Both the minimum and maximum residual electron density lies within 1 Å of the Pt atom.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The structure with the atom-numbering scheme and displacement ellipsoids (30% probability) for the title compound; the disorder in the chloro and methyl positions is not indicated. The H atoms of the methyl group are of arbitrary size while those on the cyclohexyl rings are omitted for clarity.

trans-chloromethylbis(tricyclohexylphosphine)platinum(II)

Crystal data

[PtCl(C18H33P)2(CH3)]	Z = 1
Mr = 806.40	F(000) = 416
Triclinic, P1	Dx = 1.422 Mg m^−3
a = 10.654 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.0701 (8) Å	Cell parameters from 5952 reflections
c = 10.2620 (9) Å	θ = 2.2–29.7°
α = 91.4460 (8)°	µ = 3.90 mm^−1
β = 109.639 (2)°	T = 293 K
γ = 112.649 (2)°	Prism, colourless
V = 941.7 (2) Å^3	0.49 × 0.32 × 0.25 mm

Data collection

Siemens SMART CCD diffractometer	5659 independent reflections
Radiation source: fine-focus sealed tube	5169 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.027
ω scans	θmax = 32.0°, θmin = 2.1°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −14→14
Tmin = 0.093, Tmax = 0.142	k = −14→14
10201 measured reflections	l = −13→14

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.076	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0444P)^2] where P = (Fo^2 + 2Fc^2)/3
5659 reflections	(Δ/σ)max < 0.001
198 parameters	Δρmax = 0.95 e Å^−3
0 restraints	Δρmin = −1.18 e Å^−3

Special details

Experimental. The intensity data were collected on a Siemens SMART CCD diffractometer using an exposure time of 15 s/frame. A total of 1890 frames were collected with a frame width of 0.25° being used covering up to τ = 31.95°. Completeness of 98% was accomplished up to τ = 30.0°. The first 50 frames were recollected at the end of the data collection to check for decay.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pt	0.5000	0.5000	0.5000	0.03725 (7)
P	0.29465 (8)	0.46867 (9)	0.30097 (9)	0.03691 (16)
C11	0.1217 (3)	0.3894 (4)	0.3329 (4)	0.0425 (7)
H11	0.1321	0.4630	0.4048	0.078 (3)*
C12	0.1009 (4)	0.2545 (5)	0.3983 (5)	0.0583 (9)
H12A	0.1893	0.2719	0.4785	0.078 (3)*
H12B	0.0832	0.1741	0.3306	0.078 (3)*
C13	−0.0294 (5)	0.2139 (6)	0.4459 (6)	0.0715 (12)
H13A	−0.0467	0.1221	0.4802	0.078 (3)*
H13B	−0.0056	0.2886	0.5227	0.078 (3)*
C14	−0.1677 (5)	0.1993 (5)	0.3266 (5)	0.0702 (12)
H14A	−0.1999	0.1147	0.2563	0.078 (3)*
H14B	−0.2447	0.1833	0.3626	0.078 (3)*
C15	−0.1446 (4)	0.3305 (5)	0.2597 (5)	0.0664 (11)
H15A	−0.1244	0.4127	0.3269	0.078 (3)*
H15B	−0.2339	0.3136	0.1807	0.078 (3)*
C16	−0.0184 (4)	0.3690 (5)	0.2082 (5)	0.0566 (9)
H16A	−0.0035	0.4584	0.1698	0.078 (3)*
H16B	−0.0414	0.2913	0.1346	0.078 (3)*
C21	0.2722 (4)	0.3676 (4)	0.1341 (4)	0.0448 (7)
H21	0.3716	0.4044	0.1336	0.078 (3)*
C22	0.1785 (5)	0.3868 (5)	−0.0097 (4)	0.0591 (10)
H22A	0.0763	0.3438	−0.0203	0.078 (3)*
H22B	0.2072	0.4904	−0.0115	0.078 (3)*
C23	0.1938 (6)	0.3166 (6)	−0.1344 (5)	0.0742 (13)
H23A	0.1305	0.3297	−0.2215	0.078 (3)*
H23B	0.2942	0.3646	−0.1290	0.078 (3)*
C24	0.1538 (7)	0.1585 (6)	−0.1341 (5)	0.0854 (16)
H24A	0.1735	0.1178	−0.2078	0.078 (3)*
H24B	0.0498	0.1081	−0.1529	0.078 (3)*
C25	0.2424 (7)	0.1353 (6)	0.0088 (5)	0.0821 (15)
H25A	0.3449	0.1746	0.0206	0.078 (3)*
H25B	0.2096	0.0311	0.0091	0.078 (3)*
C26	0.2288 (6)	0.2070 (5)	0.1343 (5)	0.0623 (10)
H26A	0.1284	0.1608	0.1291	0.078 (3)*
H26B	0.2916	0.1929	0.2212	0.078 (3)*
C31	0.3031 (4)	0.6417 (4)	0.2491 (4)	0.0449 (7)
H31	0.2190	0.6200	0.1612	0.078 (3)*
C32	0.2926 (5)	0.7411 (5)	0.3564 (5)	0.0611 (10)
H32A	0.2017	0.6913	0.3710	0.078 (3)*
H32B	0.3734	0.7631	0.4456	0.078 (3)*
C33	0.2978 (5)	0.8797 (5)	0.3051 (6)	0.0678 (11)
H33A	0.2940	0.9431	0.3751	0.078 (3)*
H33B	0.2130	0.8579	0.2195	0.078 (3)*
C34	0.4368 (5)	0.9581 (5)	0.2765 (6)	0.0702 (12)
H34A	0.4366	1.0470	0.2423	0.078 (3)*
H34B	0.5212	0.9855	0.3636	0.078 (3)*
C35	0.4502 (5)	0.8640 (5)	0.1696 (5)	0.0683 (11)
H35A	0.3713	0.8439	0.0794	0.078 (3)*
H35B	0.5427	0.9150	0.1580	0.078 (3)*
C36	0.4429 (4)	0.7230 (4)	0.2191 (5)	0.0579 (9)
H36A	0.5281	0.7435	0.3040	0.078 (3)*
H36B	0.4461	0.6605	0.1479	0.078 (3)*
Cl	0.6092 (5)	0.4387 (6)	0.3465 (5)	0.0542 (9)	0.50
C1	0.4125 (15)	0.5825 (19)	0.6310 (15)	0.029 (2)	0.50
H1A	0.3809	0.5119	0.6874	0.078 (3)*	0.50
H1B	0.3307	0.5996	0.5721	0.078 (3)*	0.50
H1C	0.4874	0.6724	0.6911	0.078 (3)*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt	0.02978 (8)	0.04939 (11)	0.03410 (10)	0.01929 (7)	0.01064 (6)	0.00652 (7)
P	0.0299 (3)	0.0423 (4)	0.0374 (4)	0.0169 (3)	0.0093 (3)	0.0060 (3)
C11	0.0326 (14)	0.0491 (17)	0.0419 (17)	0.0162 (13)	0.0108 (13)	0.0032 (14)
C12	0.0479 (19)	0.060 (2)	0.065 (3)	0.0186 (17)	0.0229 (19)	0.019 (2)
C13	0.065 (3)	0.071 (3)	0.078 (3)	0.016 (2)	0.040 (2)	0.019 (2)
C14	0.047 (2)	0.072 (3)	0.076 (3)	0.0044 (19)	0.031 (2)	−0.008 (2)
C15	0.0365 (18)	0.079 (3)	0.076 (3)	0.0200 (19)	0.0177 (19)	0.004 (2)
C16	0.0363 (16)	0.068 (2)	0.062 (2)	0.0227 (17)	0.0133 (16)	0.013 (2)
C21	0.0406 (16)	0.0459 (17)	0.0457 (19)	0.0214 (14)	0.0099 (14)	0.0061 (15)
C22	0.068 (2)	0.063 (2)	0.043 (2)	0.036 (2)	0.0080 (18)	0.0081 (18)
C23	0.096 (4)	0.082 (3)	0.042 (2)	0.041 (3)	0.019 (2)	0.010 (2)
C24	0.121 (5)	0.080 (3)	0.056 (3)	0.049 (3)	0.027 (3)	−0.006 (2)
C25	0.123 (5)	0.075 (3)	0.067 (3)	0.063 (3)	0.033 (3)	0.009 (2)
C26	0.085 (3)	0.055 (2)	0.055 (2)	0.040 (2)	0.024 (2)	0.0103 (19)
C31	0.0375 (15)	0.0473 (17)	0.0449 (19)	0.0172 (14)	0.0106 (14)	0.0041 (15)
C32	0.067 (2)	0.057 (2)	0.069 (3)	0.031 (2)	0.031 (2)	0.011 (2)
C33	0.070 (3)	0.054 (2)	0.080 (3)	0.033 (2)	0.022 (2)	0.005 (2)
C34	0.068 (3)	0.044 (2)	0.081 (3)	0.0195 (19)	0.012 (2)	0.005 (2)
C35	0.069 (3)	0.050 (2)	0.075 (3)	0.013 (2)	0.027 (2)	0.015 (2)
C36	0.054 (2)	0.0478 (19)	0.074 (3)	0.0191 (17)	0.028 (2)	0.0112 (19)
Cl	0.0359 (15)	0.094 (2)	0.0425 (17)	0.0318 (16)	0.0195 (10)	0.0191 (14)
C1	0.017 (4)	0.056 (5)	0.020 (4)	0.014 (3)	0.014 (3)	0.014 (3)

Geometric parameters (Å, º)

Pt—P	2.3431 (8)	C23—H23B	0.9700
Pt—C1	2.179 (13)	C24—C25	1.534 (7)
Pt—Cl	2.440 (4)	C24—H24A	0.9700
P—C11	1.851 (3)	C24—H24B	0.9700
P—C21	1.864 (4)	C25—C26	1.536 (6)
P—C31	1.812 (3)	C25—H25A	0.9700
C11—C12	1.502 (5)	C25—H25B	0.9700
C11—C16	1.541 (5)	C26—H26A	0.9700
C11—H11	0.9800	C26—H26B	0.9700
C12—C13	1.536 (6)	C31—C32	1.529 (5)
C12—H12A	0.9700	C31—C36	1.539 (5)
C12—H12B	0.9700	C31—H31	0.9800
C13—C14	1.518 (7)	C32—C33	1.492 (6)
C13—H13A	0.9700	C32—H32A	0.9700
C13—H13B	0.9700	C32—H32B	0.9700
C14—C15	1.479 (7)	C33—C34	1.518 (7)
C14—H14A	0.9700	C33—H33A	0.9700
C14—H14B	0.9700	C33—H33B	0.9700
C15—C16	1.524 (5)	C34—C35	1.510 (7)
C15—H15A	0.9700	C34—H34A	0.9700
C15—H15B	0.9700	C34—H34B	0.9700
C16—H16A	0.9700	C35—C36	1.502 (6)
C16—H16B	0.9700	C35—H35A	0.9700
C21—C26	1.501 (5)	C35—H35B	0.9700
C21—C22	1.545 (5)	C36—H36A	0.9700
C21—H21	0.9800	C36—H36B	0.9700
C22—C23	1.532 (6)	Cl—C1^i	0.391 (11)
C22—H22A	0.9700	C1—H1A	0.9600
C22—H22B	0.9700	C1—H1B	0.9600
C23—C24	1.482 (7)	C1—H1C	0.9600
C23—H23A	0.9700
P—Pt—Cl	89.15 (12)	C22—C23—H23B	109.5
P^i—Pt—Cl	90.85 (12)	H23A—C23—H23B	108.1
C1—Pt—Cl	172.7 (5)	C23—C24—C25	110.1 (4)
C1—Pt—P	89.8 (4)	C23—C24—H24A	109.6
C1^i—Pt—P	90.2 (4)	C25—C24—H24A	109.6
C11—P—Pt	112.44 (11)	C23—C24—H24B	109.6
C21—P—Pt	116.74 (10)	C25—C24—H24B	109.6
C31—P—Pt	111.78 (12)	H24A—C24—H24B	108.2
C1^i—Pt—Cl	7.3 (5)	C24—C25—C26	113.8 (4)
C11—P—C21	109.71 (16)	C24—C25—H25A	108.8
C11—P—C31	104.36 (15)	C26—C25—H25A	108.8
C21—P—C31	100.53 (16)	C24—C25—H25B	108.8
C12—C11—C16	111.5 (3)	C26—C25—H25B	108.8
C12—C11—P	114.3 (2)	H25A—C25—H25B	107.7
C16—C11—P	115.7 (2)	C21—C26—C25	110.5 (4)
C12—C11—H11	104.6	C21—C26—H26A	109.5
C16—C11—H11	104.6	C25—C26—H26A	109.5
P—C11—H11	104.6	C21—C26—H26B	109.5
C11—C12—C13	110.4 (3)	C25—C26—H26B	109.5
C11—C12—H12A	109.6	H26A—C26—H26B	108.1
C13—C12—H12A	109.6	C32—C31—C36	109.9 (3)
C11—C12—H12B	109.6	C32—C31—P	113.4 (3)
C13—C12—H12B	109.6	C36—C31—P	111.0 (2)
H12A—C12—H12B	108.1	C32—C31—H31	107.4
C14—C13—C12	111.5 (4)	C36—C31—H31	107.4
C14—C13—H13A	109.3	P—C31—H31	107.4
C12—C13—H13A	109.3	C33—C32—C31	110.1 (4)
C14—C13—H13B	109.3	C33—C32—H32A	109.6
C12—C13—H13B	109.3	C31—C32—H32A	109.6
H13A—C13—H13B	108.0	C33—C32—H32B	109.6
C15—C14—C13	112.2 (4)	C31—C32—H32B	109.6
C15—C14—H14A	109.2	H32A—C32—H32B	108.1
C13—C14—H14A	109.2	C32—C33—C34	111.1 (4)
C15—C14—H14B	109.2	C32—C33—H33A	109.4
C13—C14—H14B	109.2	C34—C33—H33A	109.4
H14A—C14—H14B	107.9	C32—C33—H33B	109.4
C14—C15—C16	112.5 (4)	C34—C33—H33B	109.4
C14—C15—H15A	109.1	H33A—C33—H33B	108.0
C16—C15—H15A	109.1	C35—C34—C33	112.0 (4)
C14—C15—H15B	109.1	C35—C34—H34A	109.2
C16—C15—H15B	109.1	C33—C34—H34A	109.2
H15A—C15—H15B	107.8	C35—C34—H34B	109.2
C15—C16—C11	108.8 (3)	C33—C34—H34B	109.2
C15—C16—H16A	109.9	H34A—C34—H34B	107.9
C11—C16—H16A	109.9	C36—C35—C34	109.2 (4)
C15—C16—H16B	109.9	C36—C35—H35A	109.8
C11—C16—H16B	109.9	C34—C35—H35A	109.8
H16A—C16—H16B	108.3	C36—C35—H35B	109.8
C26—C21—C22	108.3 (3)	C34—C35—H35B	109.8
C26—C21—P	112.9 (3)	H35A—C35—H35B	108.3
C22—C21—P	120.8 (2)	C35—C36—C31	112.4 (3)
C26—C21—H21	104.4	C35—C36—H36A	109.1
C22—C21—H21	104.4	C31—C36—H36A	109.1
P—C21—H21	104.4	C35—C36—H36B	109.1
C23—C22—C21	113.3 (3)	C31—C36—H36B	109.1
C23—C22—H22A	108.9	H36A—C36—H36B	107.9
C21—C22—H22A	108.9	C1^i—Cl—Pt	45 (3)
C23—C22—H22B	108.9	Pt—C1—H1A	109.5
C21—C22—H22B	108.9	Pt—C1—H1B	109.5
H22A—C22—H22B	107.7	H1A—C1—H1B	109.5
C24—C23—C22	110.7 (4)	Pt—C1—H1C	109.5
C24—C23—H23A	109.5	H1A—C1—H1C	109.5
C22—C23—H23A	109.5	H1B—C1—H1C	109.5
C24—C23—H23B	109.5

Symmetry code: (i) −x+1, −y+1, −z+1.