Group 11 Bis(alumanyl)metallates

Reactions of the coinage metal (CM) cyanides, CuCN, AgCN,\nor K[Au(CN)<sub>2</sub>], with [{SiN<sup>Dipp</sup>}AlK]<sub>2</sub> ({SiN<sup>Dipp</sup>} = {CH<sub>2</sub>SiMe<sub>2</sub>N(Dipp)}<sub>2</sub>; Dipp = 2,6-<i>i</i>-Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) result in KCN\nmetathesis and a series of “alumina-Gilman” reagents,\n[({SiN<sup>Dipp</sup>}Al)<sub>2</sub>CM]K (CM = Cu, Ag, or Au). The\nlatter species may be isolated in both charge-separated, [({SiN<sup>Dipp</sup>}Al)<sub>2</sub>CM]<sup>−</sup>[K(THF)<sub>6</sub>]<sup>+</sup>, or contact ion pair forms when crystallized in the\npresence or absence of THF. Computational analysis apportions a high\ndegree of covalency to the CM–Al metal bonding and attribution\nof an aluminum oxidation state that is best represented as Al(II).\nThis latter inference is supported by the experimental observation\nof THF activation, deduced to result from the competitive single electron\nreduction of the group 11 center during the synthesis of the bis(alumanyl)metalates.\nUV photolysis of [({SiN<sup>Dipp</sup>}Al)<sub>2</sub>Ag]K provided\na product of 2-fold Al(II) radical addition to benzene. This species\nis also synthesized by a modification of the reaction that gave rise\nto the initially identified cuprate metathesis product. The intermediacy\nof [{SiN<sup>Dipp</sup>}Al<sup>•</sup>] radicals, which are\nproposed to add to benzene in a stepwise manner, is supported by the\nobservation of <i>in situ</i> recorded EPR spectra, the\nsimulated parameters of which have been assigned to the singly aluminated\nbenzene product, [{SiN<sup>Dipp</sup>}Al(C<sub>6</sub>H<sub>6</sub>)<sup>•</sup>].