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(iPr2ImMe)2(Bcat)2] 1 (cat = 1,2-O2C6H4) with the small donor ligand PMe3 led to a complete ligand exchange at nickel with reductive elimination of B2cat2, formation of the bisNHC adduct [B2cat2 · (iPr2ImMe)2] 3 and formation of [Ni(PMe3)4] 2 as the metal-containing species. Electrophilic attack of MeI on complex 1 or ligand dismutation of 1 with trans[Ni(iPr2ImMe)2Br2] led to loss of only one boryl ligand of 1 and afforded the nickel mono-boryl complexes trans-[Ni(iPr2ImMe)2(Bcat)Br] 4a and trans-[Ni(iPr2ImMe)2(Bcat)I] 4b.