Reactivity of the binuclear hydride [Fe₂(CO)₄(µ-H)(µ-CO)(µ-PPh₂)(µ-Ph₂PCH₂PPh₂)] to generate phosphido and hydroxide moieties at the diiron centre

Abstract

Thermolysis of [Fe2(CO)4(µ-H)(µ-CO)(µ-PPh2)(µ-dppm)]1(dppm = Ph2PCH2PPh2) results in benzene loss via phosphorus–carbon bond cleavage yielding [Fe2(CO)5(µ-PPh2)(µ-PhPCH2PPh2)]2. In a number of other reactions of 1, carbon monoxide and the hydride are replaced by three-electron donor ligands. Chromatography on alumina afforded the bridging hydroxide complex [Fe2(CO)4(µ-OH)(µ-PPh2)(µ-dppm)]3, while thermolysis in the presence of secondary phosphines gave the bis(phosphido) complexes [Fe2(CO)4(µ-PPh2)(µ-PR2)(µ-dppm)](R = Ph 4 or C6H115). Complexes 2–4 have been characterised crystallographically. All show a diiron centre bridged by two cis three-electron donor ligands. Both 4 and 5 are fluxional on the NMR time-scale, the observed changes being ascribed to a ‘rocking’ of the phosphido-bridges and ‘twisting’ of the diphosphine respectively.