Zero-Valent Binuclear Nickel Complexes

Submitted by J. K. GONG, C. A. WRIGHT, D. L. DELAET, and C. P. KUBIAK Checked by MATTHEW MILLER and MARCETTA Y. DARENSBOURG  

Zero-valent binuclear nickel complexes bridged by diphosphine ligands exhibit interesting ligand- and metal-centered chemistry.They have been used as starting complexes to form nickel clusters. The synthesis of Ni2(CO)3(dppm)2 was first reported in 1988.  

We describe here a simple procedure to prepare the complex in high yield. Materials and General Procedures 

Ni(COD)2 (COD cyclooctadiene, CgHi2] is commercially available (Strem) or can be prepared following the literature synthesis. Dppm is availbale commercially (Aldrich, Strem) and was used as received. Carbon monoxide, (available from various sources) was used as received from Aldrich. All solvents are freshly distilled from the appropriate drying agents and deoxygenated prior to use. 

All reactions and sample preparations are carried under an inert atmosphere using standard Schlenk techniques 

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Precisely the last condition explains the fact that mainly ICC have been obtained by the immediate interaction of ligands and zero-valent metals. Thus, a large series of metal p-diketonates was synthesized in the absence of a solvent [513,634-638], for example, iron bis- and tra-acetylacetonates [635]. It was shown that other ligands can serve as activators or promoters in these processes. In particular, the introduction of a,a or y,y -bipy into the reaction mixture gives the possibility of isolating copper acetylacetonates and adducts of similar complexes of cobalt and nickel [636], meanwhile the p-diketonates of the metals above are not formed under conditions similar to those reported in Ref. 635. Under dissolution of more active metallic barium in the mixture of another p-dikctone - dipivaloyl-methane (DPM) - with dyglime (DG) or tetraglime (TG) in absolute pentane, the mononuclear complex [Ba(DPM)2(TG)] and binuclear complex [Ba2(DPM)4 ( t-H20)(DG)] were isolated and structurally characterized [637]. 

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