Diazadiene stabilized butadiene nickel(0) complexes: synthesis, characterization and reaction with acetylene and carbon monoxide. Crystal structures of (dad)Ni-μ1,4;η1-4-C4H4>Ni(dad) and (dad)Ni-μ1,4;η1-4-C4H4>Ni(CO)2

Article abstract of DOI:10.1016/0022-328X(90)85035-W

Some new reactive diazadiene nickel butadiene compounds (dad)Ni(1,3-butadiene) (4) have been prepared by reduction of the appropriate (dad)Ni^II halides (dad)NiX2, (dad = RN = CR'CR' = NR) with magnesium-1,3-butadiene-2THF.The compounds are very reactive towards acetylene and CO.Reaction with acetylene leads to the binuclear complex 5 (R = 2,6-diisopropylphenyl).The structure of 5 can be described as a non-planar (dad)nickela-2,4-cyclopentadiene, with a (dad)Ni moiety hapto-4 bonded to the metallacyclodiene; the Ni-Ni distance is 2.677(1) Angstroem.Further reaction of 5 with carbon monoxide gives 6, in which the dad ligand at the hapto-4 bonded Ni atom has been replace by two CO ligands, with the other dad ligand at the Ni^II center remaining unchanged.The crystal structure of 6 shows that replacement of one of the sterically demanding dad ligands gives a system with typical Ni⁰/Ni^II geometries, although the Ni-Ni distance (2.561(2) Angstroem) is shorter than that in 5.