Magnetic Anisotropy of Dichlorobis(η⁵‐cyclopentadienyl) Complexes of Vanadium, Niobium, and Tantalum

Abstract

The magnetic behavior of the mononuclear nd 1 systems MCp 2 Cl 2 (M = V 4+ [3d 1 ], Nb 4+ [4d 1 ], Ta 4+ [5d 1 ], space group P2 1 /c, pseudosymmetry of the molecules C 2v ) deviates from pure single ion spin magnetism on account of ligand field effect (H lf ), spin-orbit coupling (H so ), and intermolecular spin-spin exchange interactions (H ex ). For both VCp 2 Cl 2 and NbCp 2 Cl 2 excellent adaptations to the measured susceptibility data were obtained (2 K Յ T Յ 300 K) on the basis of spectroscopic data (lf, so) and cooperative metal-metal interactions (ex) of antiferromagnetic nature [molecular field model (mf)]. For TaCp 2 Cl 2 experimental term structure data are not available. Therefore, Jørgen-