E.P.R. in the [ReNC l4] − Ion

Abstract

The square pyramidal [ReNC l 4] − Ion has been doped into isomorphous the Ph 4As[RuNC l 4] host lattice and a single crystal has been studied by e.p.r. The major features of the spectra are: large anisotropic rhenium hyperfine splittings with unequal spacings; the presence of ΔM I = ± 1 and ΔM I = ± 2 ‘forbidden’ transitions which can become stronger than the ΔM I = 0 ‘allowed’ lines when the field approaches the normal to the Re-N bond; and strong reduction of g values below the free-spin value. The spin Hamiltonian parameters have been determined with accuracy and used to compute molecular orbital coefficients. The e.p.r. spectrum of a polycrystalline sample has been simulated with good agreement using the parameters from the single crystal study. The spectrum of a frozen acetonitrile solution is different and indicative of the presence of [ReNC l 4(NCCH 3)] −.