Novel phospholyl(diphenylphosphino)methane-ruthenium complexes: unexpected non-assisted cis to trans isomerization of [RuCl2(κ(2)-P-P')2].

Using the unsymmetrical P-P' phospholyl(phosphino)methane ligand, complex cis-[RuCl(2)(κ(2)-P-P')(2)] is easily prepared from [RuCl(2)(DMSO)(4)]. The two phosphole-phosphorus atoms lie in the trans position to the two cis-chloro ligands. This complex slowly isomerizes spontaneously at 20 °C to the trans-[RuCl(2)(κ(2)-P-P')(2)] diastereoisomer where the two phosphole moieties are mutually trans, as well as the two chloro ligands and the two Ph(2)P moieties. DFT calculations show that this non-classical cis-trans isomerisation process requires a 3 kcal mol(-1) energy and involves the decoordination of a phosphole arm.