(Et4N)[MoIII(DAPBH)Cl2], the first pentagonal-bipyramidal Mo(iii) complex with a N3O2-type Schiff-base ligand: manifestation of unquenched orbital momentum and Ising-type magnetic anisotropy.

The first paramagnetic pentagonal-bipyramidal complex of Mo(iii) with a N3O2-type Schiff-base ligand was synthesized by the comproportionation reaction between Mo(ii) and Mo(iv) congeners. The complex has a low-spin (S = 1/2) ground state of MoIII(4d3) with double orbital degeneracy and unquenched orbital momentum, which result in strong Ising-type magnetic anisotropy.