Chelating and bridging behaviour of bidentate P,P or P,As ligands (LL) in HRu 3(CCBu t)(CO) 7(LL) as indicated by 1H, 13C and 31P NMR spectroscopy

Abstract

The reactions of the cluster HRu 3(CCBu t)(CO) 9 ( 1) with the bidentate ligands Ph 2PCH 2CH 2EPh 2 (E = P, dppe; E = As, dppae), in the presence of Me 3NO, give the complexes HRu 3(CCBu t)(CO) 7(Ph 2PCH 2CH 2EPh 2), as two isomers, which have been separated by TLC. In the first isomer, the ligand chelates the ruthenium atom opposite to the bridging hydride (1,1-derivative), whereas, in the second, it bridges a hydride-free edge (1,2-derivative). In contrast the rather rigid diphosphine cis-Ph 2PCHCHPPh 2 (c-dppet) gives only the 1,1-derivative. When chelating, the ligands do not show any significant fluxional behaviour, but when they are bridging there is interconvension between axial and equatorial positions.