General synthesis of (salen)ruthenium(III) complexes via N⋯N coupling of (salen)ruthenium(VI) nitrides

Reaction of [RuVI(N)(L1)(MeOH)]+ (L 1 = N,N′-bis(salicylidene)-o-cyclohexylenediamine dianion) with excess pyridine in CH3CN produces [RuIII(L 1)(py)2]+ and N2. The proposed mechanism involves initial equilibrium formation of [RuVI(N)(L 1)(py)]+, which undergoes rapid N⋯N coupling to produce [(py)(L1)RuIIIN≡N-RuIII(L 1)(py)]2+; this is followed by pyridine substituion to give the final product. This ligand-induced N⋯N coupling of Ru VI≡N is utilized in the preparation of a series of new ruthenium(III) salen complexes, [RuIII(L)(X)2] ± (L = salen ligand; X = H2O, 1-Melm, py, Me 2SO, PhNH2, tBuNH2, Cl- or CN-). The structures of [RuIII(L1)(NH 2Ph)2](PF6) (6), K[RuIII(L 1)(CN)2] (9), [RuIII(L2)(NCCH 3)2][AuI(CN)2] (11) (L2 = N,N′-bis(salicylidene)-o-phenylenediamine dianion) and [N nBu4][RuIII(L3)Cl2] (12) (L3 = N,N′-bis(salicylidene)ethylenediamine dianion) have been determined by X-ray crystallography.