Synthesis, structure and reactions of coordinatively unsaturated [RuCl(CO)(dppf)(PPh3)]BF4 where dppf is trans-spanning 1,1bis(diphenylphosphino)ferrocene

A novel coordinatively unsaturated cationic 16-electron ruthenium(II) complex having dppf as a bidentate ligand, [RuCl(CO)(dppf)(PPh3)]BF4(1· BF4) is prepared from a hydride complex [RuClH(CO)(dppf)(PPh3)] and an acetylide complex [RuCl(CCPh)(CO)(dppf)(PPh3)] by treatment with HBF4·Et2O. X-Ray structure analysis of 1 reveals that the complex is the first example of the trans-spanning dppf coordinated to a d6 ruthenium (II) centre and the vacant coordination site is sterically shielded effectively by the ferrocene moiety in the solid state. In solution complex 1 is fluxional, allowing the attack of two-electron monodentate ligands such as CO, tBuNC and CH3CN to afford the corresponding six-coordinate octahedral 18-electron species with cis-chelating dppf.