ADDITION-ELIMINATION EQUILIBRIA INVOLVING 16E(-) PLATINUM(O) AND 18E(-) PLATINUM(II) COMPLEXES

The addition-elimination equilibrium involving a platinum(0) nucleophi le [Pt(N,N'-chelate)(olefin)] (1), an organometal electrophile R(m)MX( n) (M = Hg, Sn; X = Cl, Br, I; R = hydrocarbyl group), and the corresp onding five-coordinate adduct [PtX(MR(m)X(n-1))(N,N'-chelate)(olefin)] (2) has been investigated. The influence on the equilibrium of the gr oups bonded to the electrophilic center and of the ligands bonded to p latinum has been evaluated. It has been found that the adduct is stabi lized by the presence of electron-donor olefins on platinum and of ele ctron-withdrawing groups on the electrophilic metal. It has also been found that the influence of the halide moving onto platinum can be rat ionalized in terms of the relative softness of the two metals involved in the equilibrium. The X-ray molecular structures of [Pt(dmphen)(E-M eO(2)CCH=CHCO(2)Me)] (1k, dmphen = 2,9-Me(2)-1,10-phenanthroline) and of the related addition product [PtCl(SnMe(2)Cl)(dmphen)(E-MeO(2)CCH=C HCO(2)Me)] (2i) have been determined for a better understanding of the influence of steric and bonding features.