Diazabutadiene ligands

Hannant et al. also reported the synthesis (Scheme 44) of cationic zinc complexes bearing bulky diazabutadiene ligands.1 7 19F NMR spectroscopy showed that the borate anions of these compounds are non-coordinating in... 

Such reactions are initiated by a single electron transfer from the dialkylzinc moiety to the diazabutadiene ligand to afford radical pairs 109, which collapse by the regioselective transfer of the organic radical to the nitrogen 110 or carbon 111 atoms of the diazabutadiene moiety. If the alkyl radical escapes from the organozinc radical, the latter dimerizes reversibly to 112 via the formation of a very long yet credible carbon-carbon bond. 

Steric crowding in the thermal SN2 transition state for Equation 11 favors loss of the bulky diazabutadiene ligand, while under photochemical conditions simple substitution occurs. 

The radical anionic character of the 1,4-diazabutadiene ligand was further proven in the heteroleptic complex CpfSm(tBuDAB), synthesized from the strong single electron transfer reagent SmCpf(THF)2 and the free ligand [173]. 

Using a similar approach, we complexed diazabutadiene ligands to bromotricar-bonylrhenium(l), again producing mesomorphic complexes (Figure 49), except that this time the reduction in clearing point which was evident in the Mn and Re complexes above, was not observed [101]. 

Acetone adds intramolecularly to a coordinated diazabutadiene ligand in fac-[Mn(C0)3 ButN=CHCH=NBu ) MeC(0)Me ][C104] to yield/ac-... 

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