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 = C6H3Pri2-2,6) 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.