Reduction of π-Bound Nitriles to π-Bound Imines in a Tungsten(II) Bis(acetylacetonate) Coordination Sphere

Abstract

Addition of MeOTf (OTf = CF3SO3) to complexes of the type W(CO)(acac)2(η2-N≡CR) (acac = acetylacetonate) [R = Ph (1a), Me (1b)] yields cationic iminoacyl triflate salts of the type [W(CO)(acac)2(η2-MeN═CR)][OTf]. Complexes 2a and 2b undergo nucleophilic attack at the iminoacyl carbon with Na[HB(OMe)3] or MeMgBr to form neutral η2-imine complexes of the type W(CO)(acac)2[η2-MeN═C(Nuc)R] [Nuc = H (3a, 3b), Me (4)]. Hydride addition to 2b results in W(CO)(acac)2(η2-MeN═CHMe), 3b, a complex that exhibits interconversion of diastereomers at ambient temperature on the NMR time scale. X-ray structures of cationic iminoacyl complex 2a and neutral imine complex 4 confirm η2-C═N bonding of both the iminoacyl and imine ligands.