Matrix isolation and ESR study of platinum(I) diolefin complexes - norbornadiene and (1,5-cyclooctadiene) platinum dichloride radical anions

The low temperature γ-irradiation of norbornadiene and (1,5-ciclooctadiene) platinum(II) dichloride in methyltetrahydrofurane matrix leads to a selective production of electron capture centres which were identified by ESR as platinum(I) diolefin radical anions. The Molecular Orbital calculations suggest that the unpaired electron is in a b2 orbital (assuming an idealised C2υ symmetry) where the 5dyz is the major metal orbital involved. The low contribution of 5dyz to the SOMO (α2 0.23 as derived from the analysis of the experimental ESR parameters) implies a high delocalization on the ligands. The electronic structure of the paramagnetic species and, in particular, the large negative contributions to the calculated g-tensor elements giving rise from the low energy empty levels, were rationalised by extended Hueckel MO calculations. (author)