An unusual bis-heteroscorpionate complex with anomalous ligands: [tris(3,4-dibromo-5-phenylpyrazolyl)hydroborato][hydrotris(3-neopentylpyrazolyl)borato]nickel(II).

Tridentate trispyrazolylborate (Tp) ligands, introduced by Trofimenko in 1966, have been widely utilized in metal coordination chemistry because of the relatively facile synthetic modification of their electronic and steric factors. The title heteroscorpionate, [Ni(CHBBrN)(CHBN)], features one ligand, namely hydrotris(3-neopentylpyrazolyl)borate, that has previously displayed variable steric effects, and a brominated ligand, namely tris(3,4-dibromo-5-phenylpyrazolyl)hydroborate, that, atypical in trispyrazolylborate chemistry, coordinates such that the less bulky pyrazole substituent is oriented facing toward the metal ion. The potential molecular threefold symmetry in scorpionates can allow axial chirality. Although crystallized in the centrosymmetric P-1 space group, a closer inspection of the structure of the title compound reveals axial diastereomers.