SYNTHESIS AND CRYSTAL-STRUCTURE OF TETRANUCLEAR NICKEL(0) COMPLEX WITH 1,4-DIPHENYLBUTADIYNE IN THE ETA(2),ETA(2)-BRIDGING MODE

A novel tetranuclear nickel(0) complex [Ni-4(dpbd)(cod)4] (cod=1,5-cyc looctadiene) with 1,4-diphenylbutadiyne (dpbd) ln the eta(2),eta(2)-br idging mode has been prepared and then characterized crystallographica lly. Two nickel atoms are bridged by every C drop C bond of dpbd in th e eta(2),eta(2)-bridging mode to give the tetranuclear structure. Each of four nickel atoms is also bonded to two C=C bonds of cod, providin g a distorted tetrahedral geometry. The acetylenic C-C distance of the bridging dpbd is 1.35(1) Angstrom. The elongation of the C drop C dis tance indicates the contribution of the large pi back donation from ni ckel to dpbd. It was also found that the acetylenic C-C distances of t he Ni(0) diyne complexes in the eta(2),eta(2)-bridging mode are longer than those in the monodentate mode.