An electron spin resonance study of bis(tetraphenylarsonium) pentakis(isothiocyanato)nitrosyltechnetate(II): a six-co-ordinate low-spin 4d5 technetium(II) complex

Abstract

The e.s.r. spectrum of the title complex has been studied in non-aqueous solution in the liquid and frozen glass phases. The spectrum is characteristic of a low-spin 4d⁵ technetium(II) ion in an axially symmetric environment with g_∥=(+) 1.928, g_⊥=(+) 2.045, A_‖= 0.0236, and A_⊥= 0.0095 cm^–1. The small quadrupole interaction observed is solvent dependent. A simple crystal field model, in which the unpaired electron is located in the t_2g orbital triplet, is able to explain most features of the e.s.r. spectrum. A consideration of the electronic parameters derived from the g and A values leads to the conclusion that the results are best explained by a large tetragonal distortion from octahedral symmetry with strong π bonding between technetium and the ligands.