[(Triphos)Ni(η²-BH₄)]:  An Unusual Nickel(I) Borohydride Complex

Reduction of [(triphos)NiCl₂] (<b>1</b>) with an excess of NaBH₄ in THF produces the paramagnetic Ni(I) complex [(triphos)Ni(η²-BH₄)] (<b>2</b>). X-ray crystallography shows <b>1</b> to be a square-planar Ni(II) species in which the phosphine ligand is bidentate, whereas <b>2</b> has <i>pseudo</i>tetrahedral geometry at the Ni(I) center, with a tridentate phosphine and the borohydride ligand occupying a single coordination site. Density functional theory calculations show the unpaired electron in <b>2</b> to reside in an orbital located mainly on the Ni atom.