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 1 H and 13 C 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 H 2 O 2 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(II) cations ( 3 ). The structures of the related neutral [Pt(SMe) 2 (2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] and cationic [Pt(SMe 2 ) 2 (2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)][BF 4 ] 2 compounds have been determined by X-ray diffraction together with that of the free diphenyl fumarate ligand.