Ruthenium complexes featuring cooperative phosphine-pyridine-iminophosphorane (PNN) ligands: synthesis, reactivity and catalytic activity.

The coordination to ruthenium(ii) centres of two phosphine-pyridine-iminophosphorane ligands LR (PPh2CH2(C6H3N)CH2N[double bond, length as m-dash]PR3, R = Ph or Cy) differing by the nature of the substituent of the P[double bond, length as m-dash]N phosphorus was explored. Coordination to [RuCl2(PPh3)3] afforded the complexes [RuLRCl2(PPh3)] that were successfully deprotonated at the acidic phosphinomethyl position. With LCy, coordination led to a mixture of two isomers. The complexes [RuLRHCl(PPh3)] were similarly obtained from [RuHCl(PPh3)3]. The stability of these complexes depends on the ligand substitution pattern; with LPh a CH activation process took place, while [RuLCyHCl(PPh3)] was thermally stable. Deprotonation of this latter complex was achieved and gave a catalytically competent species for the acceptorless dehydrogenative coupling of alcohols.