Synthesis and characterization of trigonal-bipyramidal platinum(II) olefin complexes with chalcogenide ligands in axial positions.: X-ray molecular structures of [Pt(SMe)2(dmphen)(diphenyl fumarate)], its cationic dipositive derivative [Pt(SMe2)2(dmphen)(diphenyl fumarate)][BF4]2, and free diphenyl fumarate

The oxidative addition of RE-ER molecules (E = O, R = H, C(O)Ph, C(O)Me; E = S, Se, Te, R = Me, Ph) to Pt(0) precursors [Pt(N,N-chelate)(olefin)] (1: N,N-chelate = e.g. 2,9-dimethyl-1,10-phenanthroline; olefin = maleic or fumaric ester) has been studied. Symmetrical cleavage of the E-E bonds affords unprecedented trigonal-bipyramidal Pt(II) complexes of the formula [Pt(ER)2(N,N-chelate)(olefin)] (2). Products of type 2, which have been characterized through H-1 and C-13 NMR spectroscopy, contain chalcogenide ligands in the axial positions. The reactivity of the new compounds has also been investigated. Thus, Pt-OH fragments generated by the addition of H2O2 are acetylated by acetic anhydride. Furthermore, S, Se, and Te coordinated to Pt are readily methylated by trimethyloxonium tetrafluoroborate, affording the first examples of dipositive coordinatively saturated platinum(11) cations (3). The structures of the related neutral [Pt(SMe)(2)(2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] and cationic [Pt( Me2)(2)(2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] [BF4](2) compounds have been determined by X-ray diffraction together with that of the free diphenyl fumarate ligand.