Dichlorido{N-[2-(diphenylphosphanyl)benzylidene]-2-(thiophen-2-yl)ethanamine-κ2 P,N}platinum(II) dichloromethane hemisolvate

The crystal structure of the title compound, [PtCl2(C25H22NPS)]·0.5CH2Cl2, was determined to establish the coordination properties of the (phosphanyl)benzylidene–methanamine ligand to platinum. In the unit cell two molecules of cis-[PtCl2(C25H22NPS)] are accompanied by a dichloromethane solvent molecule. The square-planar Pt2+ coordination sphere is slightly distorted with the bidentate ligand coordinated via the P and the amine N atoms, and the Cl atoms located cis at the two remaining coordination sites. Parts of the thiophene ring and the solvate molecule were modeled as disordered with occupancy ratios of 0.55 (2):0.45 (2) and 0.302 (10):0.198 (10), respectively. Weak C—H⋯Cl interactions stabilize the crystal packing.

The crystal structure of the title compound, [PtCl 2 (C 25 H 22 NPS)]Á0.5CH 2 Cl 2 , was determined to establish the coordination properties of the (phosphanyl)benzylidenemethanamine ligand to platinum. In the unit cell two molecules of cis-[PtCl 2 (C 25 H 22 NPS)] are accompanied by a dichloromethane solvent molecule. The square-planar Pt 2+ coordination sphere is slightly distorted with the bidentate ligand coordinated via the P and the amine N atoms, and the Cl atoms located cis at the two remaining coordination sites. Parts of the thiophene ring and the solvate molecule were modeled as disordered with occupancy ratios of 0.55 (2): 0.45 (2) and 0.302 (10):0.198 (10), respectively. Weak C-HÁ Á ÁCl interactions stabilize the crystal packing.

Comment
Platinum complexes with (phosphanyl)benzylidene-methanamine ligands have been used as catalysts or catalyst precursors for a variety of organic reactions. Our group and others have recently been interested in these types of complexes and have reported several of these types of complexes (Chiririwa et al., 2011;Chiririwa & Meijboom, 2011a, 2011b, 2011cGhilardi et al., 1992;Sanchez et al., (1998Sanchez et al., ( , 2001 and Coleman et al., 2001).
The distortion is featured most prominently in the N1-Pt1-P1 angle of 86.17 (10)° versus. Cl1-Pt1-Cl2 = 89.08 (4)°, indicating some ring strain induced by the chelation of the bidentate ligand. The average Pt-N and Pt-P bond lengths of 2.030 (3) and 2.2089 (9) Å, respectively are in the range expected for similar platinum(II) complexes (Ankersmit et al.(1996)). The initial refinement model of the compound showed some large displacement parameters for the thiophene moiety as well as the dichloromethane solvent. These disorders were elucidated to give an improved model (details can be found under the experimental refinement section). Two weak C-H···Cl interactions (Steiner, 1996) aid in the stabilization of the crystal structure (see Table 1, Fig. 2).

Experimental
To a dry CH 2 Cl 2 (10 ml) solution of the precursor [Pt(COD)Cl 2 ] was added an equimolar amount of (2-(diphenylphosphanyl) benzylidene)(thiophen-2-yl)methanamine in CH 2 Cl 2 (10 ml), and stirred at room temperature for 2 hrs. The solvent was reduced and the complex precipitated out on addition of hexane, filtered off, washed with Et 2 O (2×5 ml) and dried under vacuum for 4 hrs affording a yellow precipitate in 72% yield. Crystals suitable for X-ray structure determination were obtained by recrystallization form a CH 2 Cl 2 -hexane mixture at room temperature.

Refinement
All hydrogen atoms were positioned in geometrically idealized positions with C-H = 0.99 Å and 0.95 Å for methylene and aromatic H atoms respectively. All hydrogen atoms were allowed to ride on their parent atoms with U iso (H) = 1.2U eq . A disorder refinement model was applied to the thiophene that showed large displacements at C2, C3 and S1. Geometrical (FLAT) restraints were applied to keep the rings C1, C2A/B, C3A/B, C4, S1A/B planar. Ellipsoid displacement (SIMU and DELU) restraints were also applied to the disordered moiety. The occupation parameters of the two disordered tiophene fragments were linked to a free variable so that the two sites add to unity. This showed a distribution of 0.54903:0.45097., The dichloromethane solvate was also refined as disordered on two positions in the asymmetric unit. This resulted in four disordered positions for each dichloromethane at each solvent accessible site in the crystal lattice. The occupancies of these supplementary materials sup-2 sites were linked to a free variable to add to unity and refined to a ratio of 0.60331:0.39669 (based on the asymmetric unit fraction). To keep refinement stable geometrical (DIFX and DANG) restraints were applied to the C-Cl bonds and Cl···Cl distances All the above restraints were applied with the default standard deviations. The atoms of the solvate molecule was left isotropic due to the extensive nature of the disorder. The highest residual electron density of 0.84 e.Å -3 is 0.89 Å from Pt1 representing no physical meaning. Fig. 1. View of title compound showing displacement ellipsoids (drawn at a 30% probability level) and labeling. For clarity: a) hydrogen atoms omitted, b) bonds in part B of the disordered thiophene indicated with dotted lines, and c) minor component as well as symmetry generated disordered parts of dichloromethane created by inversion center omitted.

Special details
Experimental. The intensity data was collected on a Bruker Apex-II 4 K CCD diffractometer using an exposure time of 80 s/frame. A total of 1315 frames were collected with a frame width of 0.5° covering up to θ = 28.72° with 99.8% completeness accomplished. 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 Rfactors(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.