Synthesis of ruthenium(ii) complexes of tetradentate bis(N-pyridylimidazolylidenyl)methane and their reactivities towards N- donors

Abstract

A family of hexa-coordinated ruthenium(II) complexes of bis(N-pyridylimidazolylidenyl)methane (L) were prepared and structurally characterized. Carbene transfer reactions of [Ru(p-cymene)Cl₂]₂, [Ru(CO)₂Cl₂]_n and RuHCl(CO)(PPh₃)₃ with silver–NHC complexes in situ generated from [H₂L](PF₆)₂ and Ag₂O afforded [RuL(CH₃CN)₂](PF₆)₂ (1), [Ru₂L(p-cymene)₂Cl₂](PF₆)₂ (2), [RuL(CO)₂](PF₆)₂ (3) and [RuL(PPh₃)₂](PF₆)₂ (4), respectively. The reactions of 1 towards several N- and P-donors were studied. The treatment of 1 with 1,10-phenanthroline resulted in the substitution of one pyridine and one acetonitrile molecule affording [RuL(phen)(CH₃CN)](PF₆)₂ (5) as a mixture of two isomers. Reaction of 1,2-bis(diphenylphosphino)ethane (dppe) and 1 gave [RuL(dppe)(CH₃CN)₂](PF₆)₂ (7), in which two pyridines were substituted by a dppe ligand trans to two NHC groups. In contrast, reactions of 1 with ethane-1,2-diamine, propane-1,3-diamine and 3,5-dimethyl-1H-pyrazole led to the substitution of acetonitrile and subsequent N–H addition of the CN bond of the coordinated acetonitrile yielding [RuL(ethane-1,2-diamine)(N-(2-aminoethyl)acetimidamide)](PF₆)₂ (8), [RuL(propane-1,3-diamine)(N-(3-aminopropyl)acetimidamide)](PF₆)₂ (9) and RuL(1-(3,5-dimethyl-1H-pyrazol-1-yl)ethanimine)(CH₃CN)](PF₆)₂ (10), respectively.