Static and dynamic nuclear magnetic resonance studies of complexes of trimethylplatinum(IV) halides with olefinic thio- and seleno-ethers. X-Ray crystal structures of [PtXMe3(MeSeCHCHSeMe)](X = Cl or I)

Abstract

Complexes of general type [ PtXMe3(MeECHCHEMe)](E = S or Se; X = Cl, Br, or I) have been isolated and their solution and solid-state structures established. Static structures in solution were characterised by 1H, 13C, 77Se, and 195Pt n.m.r. parameters; the dynamic stereochemistry of these complexes, arising from low-temperature chalcogen inversion and high-temperature fluxional rearrangements, was studied quantitatively by variable-temperature 1H n.m.r. spectroscopy. Correlations were found between l95Pt and 77Se chemical shifts, and between 195Pt shifts and 1J(PtSe) values in these complexes. 1J(CPt) values can be interpreted in terms of trans influence effects. The solution invertomer populations are very halogen- and temperature-dependent. In the case of selenium complexes, the predominant invertomer in solution corresponds to the single solid-state configuration as determined by X-ray crystallography. For the chloro-complex this is the meso-1 form and for the iodo-complex the meso-2 species. The effects of π-conjugation on the energies of the chalcogen inversion and platinum-methyl scrambling processes are discussed by comparing ΔG‡(298.15 K) values with those for analogous complexes with aliphatic and aromatic chalcogen ligands.