Insertion reactions of platinum(II) ureylene complexes

The reactivity of platinum(II) ureylene complexes towards various unsaturated molecules has been investigated. The complexes [Pt{NPhC(O)NPh}(cod)] 1a (cod = cydoocta-1,5-diene) and [Pt{NMeC(O)NPh}(cod)] 1b readily inserted phenyl isocyanate to give [Pt{NPhC(O)NPhC(O)NPh)} (cod)] and [Pt{NPhC(O)NMeC(O)NPh)}(cod)] respectively, with insertion taking place solely at the Pt-NMe linkage for the latter. When Ib was treated with the isoelectronic diphenyl carbodiimide the pro duct was characterised as [Pt{NPhC(O)NMeC(O)NPh} (cod)], presumably the result of hydrolysis. The biureto ligand in the latter was readily liberated by hydrochloric acid to give N'-methyl-N,N "-diphenylbiuret. Complex 1b was also treated with various disubstituted acetylenes. Dimethyl acetylenedicarboxylate rapidly inserted into the Pt-NMe bond to give [Pt{C(CO2Me)=C)CO2Me)NMeC(O)NPh}(cod)] Compound Ib failed to react with diphenylacetylene, and was decomposed by methyl propiolate. Reaction of the more robust platinum ureylene [Pt{NMeC(O)NPh}(PPh3)(2)] with methyl propiolate displaced the urea dianion to give the diacetylide complex [Pt{C=CC(O)OMe}(2)(PPh3)(2)]. The compound [Pt{NMeC(O)NPh}(PPh3)(2)] was also treated with PhNSO and again the ureylene ligand was displaced to give the dimeric platinum sulfito complex [{Pt(SO3)(PPh3)(2)}(2)].2PhNHC(O)NHMe. The crystal structure of the 2CHCl(3) solvate shows the complex to contain cocrystallised N-methyl-N'-phenylurea, hydrogen bonded from the NH moieties to the S(O)(2) groups. The compound presumably arises from hydrolysis of N-sulfinylaniline (or an intermediate insertion product thereof), and was also the only product characterised from the reaction of [Pt{NMeC(O)NPh}(PPh3)(2)] with sulfur dioxide. One of the chloroforms of crystallisation is also hydrogen bonded to the S(O)(2). The complex [Pt{NMeC(O)NPh}(PPh3)(2)] rapidly inserted carbon disulfide to give [Pt{S2CNMeC(O)NPh}(PPh3)(2)] fully characterised by a single-crystal X-ray study. The complex contains a highly puckered six-membered ring, with the fold angle between the least-squares planes drawn through the co-ordination plane of the platinum and the remainder of the metallacycle being 56.8(1)degrees. In solution the compound slowly decomposes by loss of phenyl isocyanate to give [Pt(S2C=NMe)(PPh3)(2)], also fully characterised by an X-ray crystallographic study. All the complexes reported have been subjected to extensive H-1, C-13 and (where appropriate) P-31 NMR analysis. Further data from electrospray mass spectrometry, IR spectroscopy and elemental analysis are also given.