Unexpected cis preference in palladium(II) bis(diphenylphosphinoarylthiolato) complexes. Crystal structure of cis-[Pd(PPh2(C6H4-2-S))2]

The complexes [Pd(PPh2(6-R-C6H3-2-S))2] (R=H (1); R=SiMe3 (2)) have been found to exist in solution as an equilibrium cis/trans mixture, the cis complex being the major component in both cases. The use of a low polarity crystallisation solvent allows the isolation of pure cis-1. The crystals of cis-1 are monoclinic (P21/n) with a=15.559(2), b=9.5224(9), c=22.563(3) Å and β=91.91(1)°. The angles P–Pd–P of 100.57(3)° and S–Pd–S of 85.16(3)° deviate from the right angle to accommodate the bulky –PPh2 groups in the square planar geometry. The use of polar CH3CN as a crystallisation solvent allows the isolation of trans-2.