trans-Di-μ-chlorido-bis{chlorido[tris(3,5-dimethylphenyl)phosphane-κP]palladium(II)} dichloromethane monosolvate

In the dimeric title compound, [Pd2Cl4{P(C8H9)3}2]·CH2Cl2, the metal complex molecule is situated about an inversion centre and is accompanied by a dichloromethane solvent molecule situated on a twofold rotation axis. The PdII atom has a slightly distorted square-planar coordination sphere. The effective cone angle for the tris(3,5-dimethylphenyl)phosphane ligand was calculated to be 169°. In the crystal, the metal complex and solvent molecules are linked via C—H⋯Cl interactions, generating chains along [10-2]. There are also C—H⋯π and weak π–π interactions present [centroid–centroid distance = 3.990 (2) Å, plane–plane distance = 3.6352 (15) Å and ring slippage = 1.644 Å], forming of a three-dimensional structure.

In the dimeric title compound, [Pd 2 Cl 4 {P(C 8 H 9 ) 3 } 2 ]ÁCH 2 Cl 2 , the metal complex molecule is situated about an inversion centre and is accompanied by a dichloromethane solvent molecule situated on a twofold rotation axis. The Pd II atom has a slightly distorted square-planar coordination sphere. The effective cone angle for the tris(3,5-dimethylphenyl)phosphane ligand was calculated to be 169 . In the crystal, the metal complex and solvent molecules are linked via C-HÁ Á ÁCl interactions, generating chains along [102]. There are also C-HÁ Á Á and weakinteractions present [centroidcentroid distance = 3.990 (2) Å , plane-plane distance = 3.6352 (15) Å and ring slippage = 1.644 Å ], forming of a three-dimensional structure.

Related literature
For background on catalysis of palladium compounds, see: Bedford et al. (2004). For the synthesis of the starting materials, see: Drew & Doyle (1990). For a description of the Cambridge Structural Database, see: Allen (2002). For background on cone angles, see: Tolman (1977); Otto (2001 Table 1 Hydrogen-bond geometry (Å , ).
In the title compound, Fig. 1, the dimeric Pd II complex is situated about an inversion centre and crystallizes with a dichloromethane solvate molecule that is located on a 2-fold rotation axis. Each equivalent pair of terminal bonded ligands is in a mutually trans orientation, with only slight distortions in the P1-Pd1-Cl1 and Cl2-Pd1-Cl1 angles of 173.90 (3) and 173.20 (3)°, respectively. The distortion of the square-planar metal coordination is further exemplified by the displacement of the Pd II metal centre by 0.1122 (4) Å from the plane formed by the coordinating atoms Cl2/P1/Cl1/Cl1 i (symmetry code: (i) = -x+1, -y+1, -z+1; r.m.s. deviation of mean plane = 0.0085 Å).
To describe the steric demand of the phosphane ligand the Tolman cone angle (Tolman, 1977) is still the most commonly used model. Applying this model to the geometry obtained for the title compound (and adjusting the Pd-P bond distance to 2.28 Å) we calculated an effective cone angle (Otto, 2001) of 169°. A search of the Cambridge Structural Database (CSD, V5.33, last update Aug. 2012; Allen, 2002) gave only three hits for structures containing the tris(3,5-dimethylphenyl)phosphane moiety. Cone angle calculations for these structures gave values ranging from 160 to 180°, with the value obtained for the title compound (169°) fitting well in this range.

Experimental
Dichloro(1,5-cyclooctadiene)palladium(II), [PdCl 2 (COD)], was prepared according to the literature procedure of Drew & Doyle (1990). Tris(3,5-dimethylphenyl)phosphane (12.1 mg, 0.035 mmol) was dissolved in CH 2 Cl 2 (5 cm 3 ). A solution of [Pd(COD)Cl 2 ] (5.0 mg, 0.017 mmol) in CH 2 Cl 2 (5 cm 3 ) was added to the phosphane solution. The mixture was stirred for 2hr at room temperature, after which the solution was left to slowly evaporate. Dark red crystals of the title compound suitable for a single-crystal X-ray study were obtained. Spectroscopic data for the title compound are available in the archived CIF.

Refinement
The H atoms were placed in calculated positions and allowed to ride on their parent atoms: C-H = 0.95, 0.99 and 0.98 Å for CH, CH 2 and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H atoms and = 1.2 for other H atoms. Methyl torsion angles were refined from electron density. The deepest residual electron-density hole (-1.12 eÅ 3 ) is located at 0.71 Å from Cl3 and the highest peak (0.9 eÅ 3 ) 0.86 Å from Pd1.      where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.90 e Å −3 Δρ min = −1.12 e Å −3 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 > σ(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.