Alkene ligands / 1,6-Dienes / Nickel complexes 1.6-Heptadiene Nickel(0) Complexes: rac/meso-(p-q2,11'-C,H Ni(CDT) dissolves in 1,6-heptadiene with displacement of the CDT to yield the dinuclear homoleptic product rac/meso-(p-r12,~2-C;rH12)~Ni(~2,rlZ-C;rH12))2 (1) as a mixture of stereoisomers, in which the nickel atoms are trigonal-planar coordinated by a chelating 1,6-diene ligand and one C = C bond of a bridging diene ligand. The stereoisomers differ in the coordination mode of the bridging diene ligand. -The bridging diene ligand in 1 can be displaced by various donor/acceptor molecules. In pentane, 1 reacts with ethene to yield a solution of mononuclear (CzH4)Ni(r12,112-C?H12) (2). With alkynes unsta-12){Ni(112.'12-C.IH12))2 and L -Ni(r1*,~'-C7HI2) ble complexes are formed of which the anticipated ethyne derivative (CzHz)Ni(112,'12-C7Hl~) (3) decomposes explosively at -100°C. With isocyanides, methylenephosphoranes, methyllithium, amines, pyridines, phosphanes, and phosphites (i.e. C, N, P donors) crystalline complexes of type L-Ni(qz,qz-C7HI2) have been obtained, of which the derivatives with L = tBuN = C 4, Me3PCH2 5, LiCH3 6, C7H13N 7, C5H5N 8, Me3P 9, iPr3P 10, Ph3P 11, (Ph0)3P 12 are characterized here. For 11 the crystal structure has been determined. 8 9 10 11 12 C, H, , N = l-Azabicyclo[2.2.2]octan C-Donoren Mit CO werden aus 1 bei -78'C alle 1,6-Heptadien-Liganden vom Nickel(0) verdrangt, und es entsteht Ni(C0)4. Aus 1 und tert-Butylisocyanid bilden sich in Ether bei -30°C farblose Nadeln von 4 (47%), die sich bei Raumtemp. langsam zersetzen. lm Massenspektrum von 4 ist das Molekul-Ion M + bei mJz = 237 zu beobachten, das durch schrittweise Abspaltung von Isobuten zum [(HNC)Ni(q2,q2-C7H,2)]+-Ion (181) und weiter zum [Ni(q2,q2-C7HI2)]+-Ion