Novel behaviour and reactivity in 1,1'-bis(diphenylphosphino)ferrocene and 1,1'-bis(diphenylphosphino)cobaltocene cluster derivatives

Article abstract of DOI:10.1016/S0022-328X(98)00565-8

The clusters > 2 and > 3 have been synthesised from the reaction of the parent cluster 1 with 1,1'-bis(diphenylphosphino)ferrocene (dppf) in THF.The related compound > 4 is produced from 2 and 3 in more forcing conditions.Both clusters 3 and 4 have been structurally characterised by single crystal X-ray analysis.In 3 the dppf ligand is coordinated in the vicinal form and the cluster core is a highly distorted octahedron.In 4 the vicinal mode is retained but the dppf ligand is coordinated to adjacent basal atoms of a square-base pyramid.The 31P-NMR spectra of 3 and 4 in CD2Cl2 at various temperatures show a high degree of stereochemically non-rigid behaviour.Magnetic susceptibility measurements across a range of temperatures indicate that 3 is paramagnetic at all temperatures.An electrochemical study of 1, 3, 4 and the related > 5 has demonstrated a significant degree of communication between the redox-active sites in 3 and 4.The cluster > 7 has also been synthesised from the direct reaction of the parent cluster 6 with 1,1'-bis(diphenylphosphino)cobaltocene (dppc).Synthesis of the dppc analogue of 3 was attempted but was thwarted by unfavorable redox chemistry.EPR spectra have been obtained for both dppc and 7.The oxidation product of 7 has also been produced (7⁺) and displays a high degree of stereochemically non-rigid behaviour in a fashion similar to 3 and 4.The magnetic susceptibility of 7 has also been measured, showing an extraordinarily large magnetic moment at ambient temperature. - Keywords: ruthenium clusters; 1,1'-bis(diphenylphosphino)ferrocene; 1,1'-bis(diphenylphosphino)cobaltocene