On the Reactivity of a NHC Nickel Bis-Boryl Complex: Reductive Elimination and Formation of Mono-Boryl Complexes.

The synthesis of the first terminal mono-boryl complexes of nickel, which are not stabilized by a pincer ligand, is reported. The reaction of the nickel bis-boryl complex cis-[Ni( Pr Im ) (Bcat) ] 1 (cat=1,2-O C H ) with the small donor ligand PMe led to a complete ligand exchange at nickel with reductive elimination of B cat and formation of the bis-NHC adduct [B cat  ⋅ ( Pr Im ) ] 3 and [Ni(PMe ) ] 2 as the metal-containing species. Electrophilic attack of MeI on complex 1 or ligand dismutation of 1 with trans-[Ni( Pr Im ) Br ] led to loss of only one boryl ligand of 1 and afforded the nickel mono-boryl complexes trans-[Ni( Pr Im ) (Bcat)Br] 4 a and trans-[Ni( Pr Im ) (Bcat)I] 4 b.