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

Abstract

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,S1)2], respectively, which both exist as a mixture of two isomers in solution. [RuCl2(dpppth-P,S)2] reacts at 25 °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,S1)2] reacts with CO under the same conditions to give only the monocarbonyl complex [RuCl2(CO)(dppterth-P)(dppterth-P,S1)]. Displacement of one of the dppterth ligands in [RuCl2(dppterth-P,S1)2] with bis(diphenylphosphino)methane (dppm) yields cis-[RuCl2(dppm)(dppterth-P,S1)] which isomerizes in solution to trans-[RuCl2(dppm)(dppterth-P,S1)]. 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,S1)] and cis-[RuCl2(dppterth-P,S1)(dppm)] are reported.