Synthesis and characterisation of the first examples of four-membered ring ruthenalactam complexes

Reaction of the complexes [RuCl2(PPh3)L] (L = η6-p-cymene or η6-hexamethylbenzene) with N-cyanoacetylurethane [NCCH2C(O)NHCO2Et] and tertiary amine base in refluxing methanol gives the first examples of mononuclear complexes containing the four-membered ruthenalactam ring, Ru–C–C(O)–N. The complexes were characterised by 1H and 31P{1H} NMR spectroscopy and ESI mass spectrometry. A single-crystal X-ray diffraction study on the p-cymene complex showed the four-membered ruthenalactam ring to be planar.