Α β-Diketiminato−Nickel(II) Synthon for Nickel(I) Complexes

The compound (Nacnac)Ni(μ-Br)2Li(THF)2 (Nacnac = (HC(CMeNC6H3(i-Pr)2)2) was reduced
by reaction with K/Na alloy in toluene. The resulting product [((Nacnac)Ni)2(μ-η3:η3-C6H5Me)] (1) was characterized and is best described as a Ni(II) species in which electron transfer
from Ni to toluene has occurred. This compound reacts with a variety of donors to give Ni(I)
complexes. For example, compound 1 reacts with phosphines, nitriles, acetylenes, olefins,
and ketones to give the paramagnetic complexes (Nacnac)Ni(PCy3) (2), (Nacnac)Ni(Ph2PCH2PPh2) (3), (Nacnac)Ni(NCPh) (4), (Nacnac)Ni(η2-PhCCPh) (5), (Nacnac)Ni(η2-Me3SiCCSiMe3)(6), (Nacnac)Ni(η2-H2CCPh2) (7), and (Nacnac)Ni(OCPh2) (8). In the related reaction of 1
with dimethylfulvene, electron transfer from metal to ligand is evidenced by the formation
of the dimetallic species [((Nacnac)Ni(η3:η3-C5H4CMe2))2] (9). The crystal structures of 1−9
are reported, and the bonding and reactivity of these products are discussed.