1-Azadienes as bridging ligands in nickel(0) complexes of the type [(1-aza-1.3-diene)Ni(L)]2 (L=1-aza-1.3-diene, alkyne, triphenylphosphine)

Dinuclear nickel(0) complexes of the type [(R1CHCHCHNR2)2Ni]2 have been prepared from 1-aza-1.3-dienes and (cod)2Ni. Reactions of both [Ni(A)2]2 (1) and [Ni(B)2]2 (2) (A: 1-aza-1.3-diene with R1=2-furyl, R2=phenyl; in B: R1=2-furyl, R2=furfuryl) with Ph3P result in the formation of the complexes [Ni(A)(PPh3)]2 (3) and [Ni(B)(PPh3)]2 (4). According to the X-ray analyses, 1, 3 and 4 contain two 1-aza-1.3-dienes, which act as bridging ligands yielding a diaza-dinickela eight-membered ring in the boat conformation. A variety of alkynes react with bis(1-aza-1.3-diene)nickel(0) complexes to form complexes of the type [(R1CHCHCHNR2)Ni(alkyne)]2. The molecular structures of [(B)Ni(HOC(Me)2CCC(Me)2OH)]2, [(A)Ni(PhCCC(Me)2OH)]2 and [(B)Ni(PhCCC(Me)2OH)]2, determined by X-ray analyses, also show that in these complexes both 1-azadienes bridge the Ni(0) centres. The inner dimetalla ring exhibits a chair conformation and the alkynes are terminally coordinated.