Phase dependent η2-alkene versus η1-alkyl transformation in platinum(II) complexes

Addition products of some nucleophiles to the coordinated olefin in [Pt(eta(2)-olefin)Cl(tmen)](+) (1) (tmen = N,N,N',N'-tetramethylethylenediamine) have shown to undergo a chemical transformation in the solid phase. The acetylacetonate (acac) addition product [Pt{CH(H,Ph)CH(Ph,H)(acac)}Cl(tmen)] (2) is formed as a mixture of Marcovnikov and anti-Marcovnikov isomers; in the solid state slow isomerization to the pure Marcovnikov isomer takes place. The complex [Pt{CH2CH2OC(O)CH3}Cl(tmen)] (3), obtained by addition of acetate anion to 1, in the solid state slowly dissociates into its constituent species. Heterometallacycles [Pt{CH(H,Me)CHMeONO}(tmen)](+) (4) formed by endo nucleophilic attack of an oxygen of the nitro Ligand on the cis alkene ligand can be detected in solution; however, they lose stability in the solid state where they revert to the acyclic species. The hydroxyl compound [Pt(CH2CH2OH)Cl(tmen)] (5), formed by addition of OH- to 1, undergoes, in the solid state, a condensation reaction to give the dimeric ether species [(tmen)ClPtCH2CH2OCH2CH2PtCl(tmen)] (6) and a water molecule. Moreover, the 5 to 6 transformation is catalyzed by carbon dioxide. All data are in accord with the solid state increasing the stability of the eta(2)-olefin species and free nucleophile over the eta(1)-alkyl addition product, a role for enthropic factors is envisaged. (C) 1999 Elsevier Science S.A. All rights reserved.