Synthesis and reactivity of ruthenium(II) complexes containing hemilabile phosphine-thiophene ligands

The syntheses of two new phosphine-thiophene ligands, 2-(2'-{diphenylphosphino}phenyl)thiophene (dpppth) and 3'-diphenylphosphino-2,2':5',2 "-terthiophene (dppterth) are reported. These ligands react with [RuCl2(PPh3)(3)] to give [RuCl2(dpppth-P,S)(2)] and [RuCl2(dppterth-P,S-1)(2)], respectively, which both exist as a mixture of two isomers in solution. [RuCl2(dpppth-P,S)(2)] reacts at 25 degrees C with carbon monoxide to yield a mixture of [RuCl2(CO)(dpppth-P)(dpppth-P,S)] and [RuCl2(CO)(2)(dpppth-P)(2)], while [RuCl2(dppterth-P,S-1)(2)] reacts with CO under the same conditions to give only the monocarbonyl complex [RuCl2(CO)(dppterth-P)(dppterth-P,S-1)]. Displacement of one of the dppterth ligands in [RuCl2(dppterth-P,S-1)(2)] with bis(diphenylphosphino)methane (dppm) yields cis-[RuCl2(dppm)(dppterth-P,S-1)] which isomerizes in solution to trans-[RuCl2(dppm)(dppterth-P,S-1)]. These complexes react with carbon monoxide to give trans-[RuCl2(CO)(dppm)(dppterth-P)] and cis-[RuCl2(CO)(dppm)(dppterth-P)], respectively, in which the thiophene end of the dppterth ligand is displaced by CO. The electronic spectra of these complexes are reported. Crystal structures for [RuCl2(dpppth-P,S)(2)], [RuCl2(CO)(dppterth-P)(dppterth-P,S-1)] and cis-[RuCl2(dppterth-P,S-1)(dppm)] are reported.