Single-crystal electron paramagnetic resonance of (dialkyldithiocarbamato-S,S′)[hydrotris(3,5-dimethylpyrazolyl)borato] oxovanadium(IV)(alkyl = ethyl or n-propyl)

Abstract

The single-crystal EPR spectra, at room temperature and Q-band frequencies, of [VO(L)(R₂dtc)] diluted in the isostructural molybdenum compound are reported [L = hydrotris(3,5-dimethylpyrazolyl)borato, R₂dtc = dialkyldithiocarbamato (R = Et or Prⁿ)]. The relative orientations of the principal axes of the g and A tensors show small angles of non-coincidence. The relationships between the EPR parameters and the molecular geometries are considered. Of the eight possible interpretations of the single-crystal data for each compound, those which give the most consistent interpretation between the structurally similar molecules are: for R = Et, g₁₁= 1.958, g₂₂= 1.983, g₃₃= 1.986, A₁₁=–151.9 × 10^–4 cm^–1, A₂₂=–53.0 × 10^–4 cm^–1, A₃₃=–51.0 × 10^–4 cm^–1, with g₁₁ and A₁₁ at 15.8° and 12.9° from VO, respectively; R = Prⁿ, g₁₁= 1.956, g₂₂= 1.982, g₃₃= 1.985, A₁₁=–153.4 × 10^–4 cm^–1, A₂₂=–56.6 × 10^–4 cm^–1, A₃₃=–48.7 × 10^–4 cm^–1, with g₁₁ and A₁₁ at 6.0° and 2.1° from VO, respectively. These EPR parameters and the molecular geometries, in conjunction with a parametrised angular overlap model, have been used to discuss the electronic structures of both molecules. A corresponding treatment of the literature data on [VO(Et₂dtc)₂] is also given for comparison.