Bis(diazadien)metall(O)-Komplexe, III. Nickel(O)-bis(chelate) mit aliphatischen N-Substituenten/ Bis(diazadien)metal(O) Complexes, III. Nickel(O)-bis(chelates) with Aliphatic N-Substituents

Abstract

Abstract Diazadienes (DAD) (with R1, R2 = H, CH3 and R3, R4 = alkyl) form nickel complexes 1-14 with composition (DAD)2Ni. They can be prepared by ligand substitution from other Ni(O) compounds or, preferably, by the reduction of Ni(II) salts in the presence of DAD. Spectroscopic differences (NMR, UV) indicate different structures (type 1 and 2) for diamagnetic (DAD)2Ni of same composition, depending on substituents R1-R4. The steric requirement of R3, R4 is most important as the main differences show up when going from tertiary (type 1: R2CH-N = ) to secondary a-carbon (type 2: RCH2-N = ) . X-ray analysis of a type 1 complex (R1, R2 = H, R3, R4 = cyclo-hexyl) reveals two strictly orthogonal chelate rings (D2d) corresponding to (pseudo-)tetrahedrally coordinated Nickel(O). A D2-structure with smaller dihedral angle is discussed for type 2 complexes.