Variable Borohydride Hapticity in Nickel(II) Scorpionate Complexes [(TpR,Me)Ni(ηn‐BH4)]: TpR,Me = hydrotris{3‐R‐5‐methyl‐1‐pyrazolyl}borate; R = Ph, n = 3 vs. R = Me, n = 4

Abstract

A "second-generation" scorpionate ligand was utilized to prepare the nickel(II) borohydride complex [(Tp Ph,Me )Ni(η 3 -BH 4 )], wherein the borohydride was coordinated through two bridging B-H bonds, leaving two terminal B-H bonds uncoordinated as determined by X-ray crystallography. The distorted square-pyramidal complex is paramagnetic (S = 1), with 18 valence electrons, and contrasts with a previously reported 20-electron pseudo-octahedral "first-generation" analogue, [(Tp Me,Me )Ni(η 4 -BH 4 )] (P. J. Desrochers, et al. Inorg. Chem.

Mechanochemical Synthesis and Reactivity of a Stable Nickel Borohydride

“…[6,9,18,31 -34] The widely known scorpionate ligand tris(pyrazolyl)borate was used to prepare the well characterised Ni(II) borohydride complex (I) with a variable coordination mode for the borohydride ligand (Figure 1). [35][36][37] The N-donor macrocyclic ligands played an important role in stabilising various key intermediates of metal complexes (II, III). [38][39][40][41] Kersting employed the macrocyclic hexaaza dithiophenolate ligand to isolate the first paramagnetic borohydride bridged dinuclear Ni(II) complex.…”