Conversion of arene groups to η2-cyclohexene rings at tungsten metalcenters

Article abstract of DOI:10.1016/0277-5387(95)85015-5

The sodium amalgam (4Na per W) reduction of hydrocarbon solutions of [W(OC6HPh4-2,3,5,6)2Cl4] (1) (OC6HPh4-2,3,5,6=2,3,5,6 tetraphenylphenoxide)in the presence of phosphine ligands (L) leads to the deep-green comple xes [W(OC6HPh3-η6-C6H5)(OC6PHh4-2,3,5,6)(L)] (2a, L=PMe2Ph; 2b, L=PMePH2). The solid state structure of 2a shows one of the ortho-phenyl groups of an aryloxide ligand bound to the tungsten metal center. The η6-arene complex 2a reacts very slowly with H2 (1 atm, 25°C) in C6D6 solution to produce a dark-brown complex [W(OC6HPh3-η2-C6H9)(OC6HPh3-η6-C6H5)(PMe2Ph)] (3a), the solid-state structure of which showsthat one of the ortho-phenyl rings has undergone reaction with two equi valents of H2 to produce a cyclohex-1-ene ring which is η2-bound to the metal center. The remaining aryloxide ligand in 3a is chelated through an η6-interaction, leading to a formal 18-electron configuration at the metal.