Effect of the spin-orbit interaction of ligands on the parameters of EPR spectra for a series of niobium(IV) complexes of trans-[NbX4(OPPh3)2] (X = Cl, Br, I)

Abstract

Two crystal modifications of new molecular niobium(IV) complex trans-NbI4(OPPh3)2 were obtained by ampoule synthesis, and their X-ray crystal structures were solved (P-1, a = 9.5795 Å, b = 9.7287 Å, c = 11.2337 Å, α = 107.984°, β = 104.061°, γ = 95.500°, V = 949.24 Å3; P21, a = 10.204 Å, b = 16.039 Å, c = 11.857 Å, β = 102.663°, V = 1893.3 Å3). For the series of molecular complexes trans-NbX4(OPPh3)2 (X = Cl, Br, I) magnetic properties were studied and systematized using EPR, magnetic susceptibility measurements, and theory calculations with DFT approximation. Theory calculations of EPR parameters have shown good accordance with experimental data and allowed to establish a negative sign of the principal hyperfine tensor values.