Diferrocenyltriphosphines 2. Reversible phosphine deligation in the chemistry of diferrocenyltriphosphine Ru(II) dichloride complexes with nitriles and pyridines: towards a pH-switchable catalyst?

The reaction of the complexes [P3-(P3fc2)RuCl2], P3fc2=[η5-(R2PC5H4)Fe-η5:η5-(C5H4P(R′)C5H4)Fe(η5-C5H4PR2)], R, R′=Ph, iPr with linear nitriles results in the formation of the pseudooctahedral complexes, e.g. [P3-(P3fc2)Ru(NCCH2R)Cl2], R=H, Ph while the reaction of [(P3fc2)RuCl2] with pyridines results in partial deligation of one of the ferrocenyl phosphine ligand arms to give the products [P2-(η5-(R2PC5H4)Fe-η5:η5-(C5H4P(R′)C5H4Fe(η5-C5H4PR2))Ru(pyr)2Cl2]. The latter products revert to the starting complexes in the absence of excess pyridine in solution. The deligated pendant phosphine may be ‘trapped’ by reaction with Pd(II) or elemental sulfur. A molecular modelling study has been carried out to verify the conformations of the products. The single crystal structures of mer-[P3-(P3fc)2Ru(CO)Cl2] and mer-[P2-(P3fc)2Ru(pyr)2Cl2] have been determined. Cyclic voltammetry supports the role assigned to pyridine in the reaction with the P3Fc2-RuCl2 complexes.