A Crystalline NiX<sub>6</sub> Complex
Josef T. Boronski, Agamemnon E. Crumpton, Simon Aldridge
Abstract
High Resolution Image Download MS PowerPoint Slide High-valent nickel species are implicated as intermediates in industrially relevant chemical transformations and in the catalytic cycles of metalloenzymes. Although a small number of tetravalent NiX 4 complexes have been crystallographically characterized, higher nickel valence states have not been identified. Here we report a stable, crystalline NiX 6 complex, Ni(BeCp) 6 ( 1; cyclopentadienyl anion (Cp)), formed by the insertion of zerovalent nickel into three Be–Be bonds. This 16-electron species features an inverted ligand field, is diamagnetic, and exhibits C 3 v symmetry, on account of the lifting of Ni 4 p -orbital degeneracy in this molecular geometry. Single-crystal X-ray diffraction and quantum chemical calculations both reveal a toroidal band of electron density perpendicular to the C 3 axis of the complex, which may be attributed to delocalized, multicenter aromatic NiBe 6 bonding.