Organometallic complexes of platinum-group metals incorporating substituted guanidine dianion (triazatrimethylenemethane) ligands

Abstract

Reactions of the platinum-group metal halide complexes [PtCl 2(COD)] (COD=1,5-cyclo-octadiene), [Cp*RhCl 2(PPh 3)] (Cp*= η 5-C 5Me 5), [Cp*IrCl 2(PPh 3)], [( p-cymene)RuCl 2(PPh 3)] and [( p-cymene)OsCl 2(PPh 3)] with symmetrically trisubstituted (acetyl or phenyl) guanidines, mediated by silver(I) oxide, give complexes formally containing the triazatrimethylenemethane ligand. A full X-ray crystal structure determination is reported for the N, N′, N″-triphenylguanidine dianion complex [ Pt{NPhC(NPh)NPh}(COD)] 4a which shows the presence of a planar Pt-NR-C(NR)-NR four-membered platinacycle. At room temperature (r.t.), the 1H- and 13C{ 1H}-NMR spectra of 4a yield a single set of COD CH and CH 2 resonances. At 240 K however, two sets of resonances are observed, interpreted in terms of fluxionality of the CN-Ph moiety. Attempted synthesis of the analogous platinum triacetylguanidine complex yields the new ureylene complex [ Pt{NAcC(O)NAc}(COD)] , via a hydrolysis reaction. Starting with the osmium compound, both the guanidine complex [(p −cymene) Os{NAcC(NAc)N Ac}( PPh 3)] 9 and the ureylene complex [(p −cymene) Os{NAcC(O)NAc}(PPh 3)] 10 were formed; similar results were obtained for the iridium system.