A Nickel Complex Containing a Pyramidalized, Ambiphilic Pincer Germylene Ligand

Reaction of N-heterocyclic carbene (NHC)-stabilized PGeP-type germylene Ge{o-(PiPr(2))C6H4}(2)(Me)IiPr (1) ((Me)IiPr=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with Ni(cod)(2) gave pincer germylene complex Ni[Ge{o-(PiPr(2))C6H4}(2)]((Me)IiPr) (2), in which the Ge center of 2 is significantly pyramidalized. Theoretical calculation on 2 predicted the ambiphilicity of the germanium center, which was confirmed by reactivity studies. Thus, complex 2 reacted with both Lewis base (IMe)-I-Me ((IMe)-I-Me=1,3,4,5-tetramethylimidazol-2-ylidene) and Lewis acid BH3SMe2 at the germanium center to afford the adducts Ni[Ge{o-(PiPr(2))C6H4}(2)(IMe)-I-Me]((Me)IiPr) (3) and Ni[Ge{o-(PiPr(2))C6H4}(2)BH3]((Me)IiPr) (4), respectively. Furthermore, the former was slowly converted to dinuclear complex Ni-2[Ge{o-(PiPr(2))C6H4}(2)](2)((IMe)-I-Me)(2) (5) at room temperature. Complex 5 can be regarded as a dimer of the (IMe)-I-Me analog of 2 with a Ni-Ge-Ge-Ni linkage.