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

The first examples of mononuclear complexes containing the four-membered ruthenalactam ring, Ru-C-C(O)-N, have been synthesised from [RuCl2(PPh3)L] (L = η6-p-cymene or η6-hexamethylbenzene) with N-cyanoacetylurethane [NCCH2C(O)NHCO2Et] and tertiary amine base in refluxing methanol; an X-ray diffraction study showed the four-membered ruthenalactam ring to be highly planar.