Syntheses, characterization and facial–meridional isomerism of tungsten tricarbonyl diphosphine complexes

Abstract

The complexes fac-[W(CO)₃(η²-dppf)(η¹-dppm)] 4f, fac-[W(CO)₃(η²-dppm)(η¹-dppf)] 5f, fac-[W(CO)₃(η²-dppf)(η¹-dppe)] 6f, fac-[W(CO)₃(η²-dppe)(η¹-dppf)] 7f, fac-[W(CO)₃(η²-dppm)(η¹-dppe)] 8f and fac-[W(CO)₃(η²-dppe)(η¹-dppm)] 9f have been prepared by treating fac-[W(CO)₃(η²-diphos)(NCMe)] 1–3 [diphos = 1,1′-bis(diphenylphosphino)ferrocene (dppf), dppm (Ph₂PCH₂PPh₂) or dppe (Ph₂PCH₂CH₂PPh₂)] with the corresponding diphosphines. The initially afforded facial isomers are converted into the meridional forms (4m–9m) in a subsequent, slow rearrangement process through opening of the chelated diphosphine ligand. A five-co-ordinate, square-pyramidal intermediate is presumed. In contrast, acid-assisted facial–meridional isomerization of 4f and 6f is likely via a seven-co-ordinate hydrido species. The new compounds have been characterized by elemental analyses and IR, mass and NMR spectroscopy.