Nuclear magnetic resonance investigations of configurational non-rigidity in dinuclear platinum(IV) complexes. Part 6. Synchronous pyramidal inversion of chalcogen atoms in [(PtXMe3)2(ECH2CME2CH2E)] complexes (E = S or Se; X = Cl, Br, or I)

Abstract

Platinum(IV) complexes of the type [(PtXMe₃)₂([graphic omitted])](E = S or Se; X = Cl, Br, or I) have been synthesised and shown to possess dinuclear structures with highly strained Pt₂X₂ moieties. Variable-temperature ¹H n.m.r. studies have clearly identified pyramidal inversions of the E atom pairs and scrambling of the Pt-methyl groups. Although chalcogen atom switching between the Pt atom pairs has not been unambiguously detected, this process constitutes the probable link between the other two fluxional processes. The ΔG^† data for the pyramidal inversions are in the range 66–75 kJ mol^–1. Such values, being in most cases ca. 20 kJ mol^–1 higher than the usual single-site inversions, are clearly associated with appreciably slower, synchronous inversions of the chalcogen atom pairs.