Packing effects on the geometry of neutral platinum(II) complexes due to solvate molecules: the structures of...

A series of structures of trans-dichlorobis(triphenylarsine)platinum(II), recrystallized from four different solvents, have been characterized by X-ray crystallography and were shown to crystallize as different solvates (same metal complex, different crystallization solvents). Their geometric differences induced by packing and solvent molecules were analysed with half-normal probability plots and root-mean-square deviations. The recrystallization solvents used in the investigation were 1,1,1-trichloroethane, dichloromethane, 1,2-dichloroethane and benzene, and the following crystallization modes were obtained. From 1,1,1-trichloroethane the metal complex crystallizes without solvent as trans-[PtCl2(AsPh3)2] in P2(1)/n with Z = 2, a = 9.271 (2), b = 19.726 (4), c = 9.830 (2) A, beta = 111.83 (3)degrees, V = 1668.8 (6) A3, R = 0.0262, and from dichloromethane with two solvent molecules as trans-[PtC12(AsPh3)2].2CH2C12 in Pbca with Z= 4, a = 20.582 (4), b = 8.146 (2), c = 23.491 (5) A, V = 3938.5 (14) A3 and R = 0.0316. From dichloroethane it crystallizes with one solvent molecule as trans-[PtC12(AsPh3)2].C2H4C12 in P1 with Z = 1, a = 9.390 (2), b= 9.548 (2), c = 11.931 (2) A, alpha = 109.70 (3), beta = 108.26 (3), gamma = 98.77 (3) , V= 915.6 (3) A3, R = 0.0390, and from benzene with half a solvent molecule as trans- [PtC12(AsPh3)2].0.5C6H6 in P2(1)/n with Z = 4, a = 11.778 (2), b = 18.712 (4), c = 16.647 (3) A, beta = 104.78 (3) , V= 3547.3 (12) A3 and R = 0.0303. In all four compounds platinum(II) coordinates to triphenylarsine and chloride in a pseudo-square-planar trans configuration. The Pt-As distances are in the range 2.4104 (4)-2.3923 (4) A and the Pt-C distances are in the range 2.309 (2)-2.2839 (9) A. The solvents have a large influence on the packing, resulting in different space groups or different occupancies in the same space group. Half-normal probability plots show that the largest geometric differences, within the metal complex, are in the bond and torsion angles around the As-C bonds. Very similar torsion angles were observed around the Pt-As bond for all the structures, except for one AsPh3 ligand in the benzene solvate, which differs by about 10 from the others. The metal-donor bond distance varies by as much as 0.019 and 0.025 A (95% confidence interval) for Pt-As and Pt-C1, respectively. The variations are essentially caused by intermolecular interactions. Packing efficiency is expressed as the volume filled by each metal complex in the unit cell and is calculated by subtracting the sum of the solvent molecule volumes from the total volume of the unit cell and then dividing by Z. The efficiency is largest in the dichloroethane solvate and smallest in the non-solvated compound, with a difference of approximately 22 A3 per metal complex.