Reaction of [PtCl2 (COD)] or cis-[PtCl2 (PPh3) 2] with a range of mono-and di-substituted ureas, together with urea itself, and an excess of silver (I) oxide gives ureylene complexes 3 and 4 containing the Pt N C (O) N four-membered ring system. The complexes have been fully characterised by multinuclear NMR and IR spectroscopies, electrospray mass spectrometry, and a single-crystal X-ray structure of the complex (Ad= 1-adamantyl, COD= ...