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 [P-3-(P(3)fc(2))RuCl2] P(3)fc(2) = [eta (5)-( R(2)pC(5)H(4))Fe-eta (5):eta (5)-(C5H4P(R')C5H4)Fe(eta (5)-C5H4PR2)], R, R' = Ph, iPr with linear nitriles results in the formation of the pseudooctahe dral complexes, e.g. [P-3-(P(3)fc(2))Ru(NCCH2R)Cl-2] R = H, Ph while the re action of [(P(3)fc(2))RuCl2] with pyridines results in partial deligation o f one of the ferrocenyl phosphine ligand arms to give the products [P-2-(et a (5)-(R2PC5H4)Fe-eta (5):eta (5)-(C5H4P(R')C5H4Fe(eta (5)-C5H4PR2))Ru(pyr) (2)Cl-2]. The latter products revert to the starting complexes in the absen ce 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. Th e single crystal structures of mer-[P-3-(P(3)fc)(2)Ru(CO)Cl-2], and mer-[P- 2-(P(3)fc)(2)Ru(pyr)(2)Cl-2] have been determined. Cyclic voltammetry suppo rts the role assigned to pyridine in the reaction with the P(3)Fc(2)-RuCl2 complexes. (C) 2001 Published by Elsevier Science B.V.