MATRIX ISOLATION AND ESR STUDY OF PLATINUM(Ⅰ) DIOLEFIN COMPLEXES—NORBORNADIENE AND (1,5-CYCLOOCTADIENE) PLATINUM DICHLORIDE RADICAL ANIONS

摘要

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 b_2 orbital (assuming an idealised C_(2v) symmetry) where the 5d_(yz) is the major metal orbital involved. The low contribution of 5d_(yz) to the SOMO (α~2 = 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.