Neutral and Ionic Aluminum, Gallium, and Indium Compounds Carrying Two or Three Terminal Ethynyl Groups

The syntheses of the ionic compounds [Li^+·2 dioxane (2,6-iPr2C6H3N(SiMe3)Al(CCSiMe3)3)^-]·0.75 dioxane (1), [(Li^+)2·(dioxane)7] 0.5 [2,6-iPr2C6H3N(SiMe3)Ga(CCSiMe3)3^-]·1.5 dioxane (2), and [(Li^+)2·(dioxane)7]0.5 [2,6-iPr2C6H3N(SiMe3)In(CCSiMe3)3^-]·1.5 dioxane (3) by the reaction of the corresponding organo metal chloride with LiCCSiMe3 are reported. The neutral ethynyl compounds Br-Al(CCtBu)2·2 THF (4), Cl-Ga(CCtBu)2·THF (5), Cl-In(CCtBu)2·2 THF (6), Al(CCtBu)3·C{N(Me)CMe}2 (7), Ga(CCtBu)3·dioxane (8), and In(CCtBu)3·NEt3 (9) have been obtained in good yields from the reaction of AlBr3, GaCl3, and InCl3 with LiCCtBu in the presence of a Lewis base. Compound 7 is the first heterocyclic carbene substituted ethynyl derivative. Aluminum and gallium compounds with three terminal ethynyl groups Al(CCPh)3·NMe3 (10) and Ga(CCPh)3·NMe3 (11) have been prepared by the reaction of AlH3·NMe3 or GaH3· NMe3 with three equivalents of phenylethyne. All the above-mentioned compounds have been structurally studied. In compound 1 the lithium ion is coordinated to the three terminal ethynyl groups, whereas in compounds 2 and 3 the lithium is coordinated to the solvent (dioxane). Compound 8 crystallizes as a coordination polymer with dioxane molecules bridging the individual gallium units.