Structure‐Property Studies of Niobium (<i>N</i>‐Heterocyclic) Carbene Complexes

Abstract The structures and magnetic properties of four paramagnetic bis(carbene)niobium and a diamagnetic monocarbene complex are described. Crystallographic studies show solvated crystals of NbCl 4 (IMes) 2 ( 1 ⋅ C 7 H 7 ), NbCl 3 (IMes) 2 ( 2 ⋅ Et 2 O and 2 ⋅ C 5 H 12 ), and NbOCl 2 (IMes) 2 ( 3 ⋅ Et 2 O ) adopt distorted structures consistent with second‐order Jahn‐Teller carbene‐halide interactions. Magnetic studies indicate 1 – 3 display appreciable temperature‐independent paramagnetism contributions to their S= 1/2, 1, and 1/2 spin ground states, respectively. Slow magnetization relaxation dynamics are seen below ca. 6 and 50 K, which are ascribed as arising from Raman and direct/Raman pathways for 1 and 3 , respectively.