Group 9 and 11 metal(I) gallyl complexes stabilized by N-heterocyclic carbene coordination: First structural characterization of Ga-M (M = Cu or Ag) bonds

Reactions of the anionic gallium(I) heterocycle [:Ga{[N(Ar)C(H)](2)}](-) (Ar = C6H3Pr2i-2,6) with a variety of N-heterocyclic carbene (NHC) complexes of group 9 and 11 halides are reported. In all cases, salt elimination occurs, yielding the neutral metal gallyl complexes [M(COD)(IMes){Ga{[N(Ar)C(H)](2)}}] (M = Rh or Ir; COD = 1,5-cyclooctadiene; IMes = :C{N(C6H2Me3-2,4,6)CH}(2)) or [(NHC)M{Ga{[N(Ar)C(H)](2)}}] (M = Cu, Ag, or Au; NHC = IMes, IPr (:C{N(Ar)C(H)}(2)), or ICy (:C{N(C6H11)C(Me)}(2))). NHC coordination apparently stabilizes the formed complexes toward elimination processes that have been observed in previous studies. The majority of the complexes in this study have been the subjects of X-ray crystallographic studies, which in several cases reveal the first examples of Ga-Cu or Ga-Ag bonds in molecular complexes. Analogies between the gallium heterocycle and cyclic boryl ligands are explored. Solid-state and spectroscopic studies on the prepared complexes suggest that the gallyl ligand has a trans influence intermediate between cyclic boryls and chloride.