trans-Dichloridobis[dicyclohexyl(phenyl)phosphane-κP]palladium(II)

The title compound, [PdCl2{P(C6H11)2(C6H5)}2], forms a monomeric complex with a trans-square-planar geometry. The Pd—P bond lengths are 2.3343 (5) Å, as the Pd atom lies on an inversion centre, while the Pd—Cl bond lengths are 2.3017 (4) Å. The observed structure was found to be closely related to [PdCl2{P(C6H11)3}2] [Grushin et al. (1994 ▶). Inorg. Chem. 33, 4804–4806], [PdBr2{P(C6H11)3}2] [Clarke et al. (2003 ▶). Dalton Trans. pp. 4393–4394] and [PdCl2P(C6H11)2(C7H7)}2] [Vuoti et al. (2008 ▶). Eur. J. Inorg. Chem. pp. 397–407] (C6H11 is cyclohexyl and C7H7 is o-tolyl). One of the cyclohexyl rings is disordered with the phenyl ring in a 0.587 (9):413 (9) ratio. Five long-range C—H⋯Cl interactions were observed within the structure.


trans-Dichloridobis[dicyclohexyl(phenyl)phosphane-κP]palladium(II)
Andrew R. Burgoyne, Reinout Meijboom and Hezron Ogutu Comment Complexes involving palladium metal centres are amongst some of the most popular catalytic precursors in organic synthesis due to their catalytic abilities. They are used in carbon-carbon bond formation reactions like the Heck, Stille and Suzuki reactions (Bedford et al., 2004).
[PdCl 2 (L) 2 ] (L = tertiary phosphine, arsine or stibine) complexes can conveniently be prepared by the substitution of 1,5-cyclooctadiene (COD) from [PdCl 2 (COD)]. The title compound, trans-[PdCl 2 (C 18 H 27 P) 2 ], crystallizes with the Pd atom on a center of symmetry and each pair of equivalent ligands in a mutually trans orientation. The geometry is, therefore, slightly distorted square planar and the Pd atom is not elevated out of the coordinating atom plane. All angles in the coordination polyhedron are close to the ideal value of 90°, with P-Pd-Cl = 89.296 (16)° and P-Pd-Cl i = 90.704 (16)°. As required by the crystallographic symmetry, the P-Pd-P i and Cl-Pd-Cl i angles are 180°. The symmetry code used to define atoms through the inversion point is: (iv) 2 -x, -y, 2 -z.
One of the cyclohexyl rings, C13-C18, in the title compound is disordered with the phenyl ring, C1-C6, over the same positions in a 59:41 (9) occupancy ratio.
The title compound compares well with other closely related Pd II complexes from the literature containing two chloro and two tertiary phosphine ligands in a trans geometry (Muller & Meijboom, 2010a, b). The title compound, having a Pd -Cl bond length of 2.3017 (4) Å and a Pd-P bond length of 2.3343 (5) Å, fits well into the typical range for complexes of this kind. Notably the title compound did not crystallize as a solvated complex; these type of Pd II complexes have a tendency to crystallize as solvates (Ogutu & Meijboom, 2011).
A weak hydrogen bond exists between C13-H13···Cl1 i (Symmetry code: -x + 2, -y, -z + 2) with the distance listed in Table 1. Four other longer range hydrogen interactions exist as shown in Table 1.

Refinement
The undisordered quintessential cyclohexyl ring, C7-C12, was used to model the disordered cyclohexyl ring, C1B-C6B, by restraining the two rings to have similar bond lengths and 1,3 atom distances within a standard deviation of 0.02 Å. (SAME command in Shelxtl, Sheldrick, 2008). Atoms C1 and C1B, the two ipso-carbons for the disordered phenyl and dicyclohexyl rings, were constrained to have identical ADPs. The phenyl ring has been constrained to resemble an ideal hexagon with C-C distances of 1.39 Å All hydrogen atoms were positioned geometrically with C-H = 0.98 Å for H atoms bonded to tertiary C atoms, 0.97 Å for methylene H atoms, and 0.93 Å for aromatic H atoms. . All hydrogen atoms were allowed to ride on their parent atoms with U iso (H) = 1.2U eq (C). The remaining highest electron peak was 0.37 at 0.95 Å from P1 and the deepest hole was -0.38 at 0.92 Å from Pd1.

Special details
Experimental. The intensity data was collected on a Bruker X8 Apex II 4 K Kappa CCD diffractometer using an exposure time of 10 s/frame. A collection frame width of 0.5° covering up to θ = 24.9° resulted in 97% completeness accomplished. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.