Triphenylboron adducts of redox-active cyanomanganese ligands†

Abstract

The reaction of [Mn(CN)(PR₃)(NO)(η-C₅H₄Me)] (R = Ph or OPh) with [AuCl(tht)] (tht = tetrahydrothiophene) in the presence of Na[BPh₄] gave [Mn(CNBPh₃)(PR₃)(NO)(η-C₅H₄Me)], X-ray studies on which (R = OPh) confirm addition of triphenylboron to the nitrogen atom of the cyanomanganese centre. Comparison of the geometry of the Ph₃B–NC interaction, as measured by the mean C–B–C angle and mean B–C length, with those of L·BPh₃ species in the Cambridge Structural Database showed the manganese ligand to be a relatively weak donor comparable with a range of other N and O ligands. The complexes [Mn(CNBPh₃)(PR₃)(NO)(η-C₅H₄Me)], as well as cis-[Mn(CNBPh₃)(CO)₂{P(OEt)₃}(dppm)] and trans-[Mn(CNBPh₃)(CO)(dppm)₂], can be prepared directly from BPh₃ and the appropriate cyanomanganese ligand. Each of the complexes undergoes one-electron oxidation at a platinum disc electrode in CH₂Cl₂ and the reaction of trans-[Mn(CNBPh₃)(CO)(dppm)₂] with [Fe(η-C₅H₅)₂][PF₆] gives trans-[Mn(CNBPh₃)(CO)(dppm)₂][PF₆].