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

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.