Synthesis and X-ray Structural Characterization of Two Unbridged Diplatinum(III) Compounds: cis- and trans-Bis[bis(1-imino-1-methoxyethane)trichloroplatinum(III)]. Transient Species in the Oxidation of Platinum(II) to Platinum(IV)

Abstract

Unbridged PtIII dimers, cis- and trans-[PtCl3L2]2 (L = (E)-HNC(OMe)Me, cis-2 and trans-2), are formed, as transient species, in the oxidation with excess chlorine of the PtII compounds cis- and trans-[PtCl2L2] (cis-1 and trans-1) to the corresponding PtIV species, cis- and trans-[PtCl4L2] (cis-3 and trans-3). Complexes cis-2 and trans-2 are rather stable at low temperature (<0 and −20 °C for cis-2 and trans-2, respectively), while at higher temperature (20 °C) they readily oxidize to PtIV (τ1/2 = 80 and 5 min for cis-2 and trans-2, respectively). The structures of the PtIII species have been solved by single-crystal X-ray diffraction. The compounds are neutral dimers composed of two square-planar PtCl2L2 units perpendicularly connected by a Pt−Pt bond and capped by axially coordinated chloride ligands. Bond distances and angles within the equatorial PtCl2L2 units are normal. The axial Pt−Cl bond lengths are ca. 0.14 A longer than the equatorial ones, indicating a strong trans influence of the intermetalli...