Ni(ii) complexes of the phosphine-oxime Ph2PC6H4-2-CH=NOH.

We report the solution and structural chemistry of nickel(ii) complexes of the phosphine-oxime Ph₂PC₆H₄-2-CH=NOH (PCH=NOH). PCH=NOH invariably binds in a bidentate manner as illustrated by cis-Ni(PCH=NOH)₂Cl₂ and cis-[Ni(PCH=NOH)₂]²⁺ (as its BF₄⁻ salt). Treatment of PCH=NOH with Ni(OAc)₂(H₂O)₄ gave charge-neutral trans-[Ni(PCH=NO)₂]⁰. Treatment of trans-[Ni(PCH=NO)₂]⁰ with BF₃ gave [Ni(PCH=NO)₂BF₂]BF₄. The cation features a planar NiP₂N₂ center wherein the pair of oximate groups are linked by the difluoroboryl center. The 1 : 1 complexes of the oxime and the oximate are illustrated by [Ni(PCH=NOH)Cl₂]₂ and [Ni(C₆F₅)(PCH=NO)]₂, which feature five- and four-coordinate Ni(ii) centers, respectively. All complexes in this series hydrolyze to give the trinickel oxo-phosphine-oximate complex [Ni₃(PCH=NO)₃O]⁺. One feature of the PCH=NOH ligand is its wide bite angle combined with its protic OH center. These aspects are manifested in the structures of Ni(PCH=NOH)₂Cl₂ and [Ni(PCH=NOH)Cl₂]₂, which show intramolecular hydrogen bonding to terminal chloride ligands. [ABSTRACT FROM AUTHOR]