Unexpected Formation of Ga₄C₂H₄ Heteroadamantane Cages by the Reaction of Carbon-Bridged Bis(dichlorogallium) Compounds with <i>tert</i>-Butyllithium

Reactions of the carbon-bridged bis(dichlorogallium) compounds (Cl2Ga)2C(SiR2R′)-CH2-Ph (1a, R = R′ = Me; 1b, R = Ph, R′ = Me; 1c, R = Me, R′ = CMe3) with four equivalents of tert-butyllithium yielded bis[tert-butyl(hydrido)digallium] compounds {[(Me3C)(H)Ga]2C(SiR2R′)-CH2-Ph}2 (3a to 3c), via β-elimination and release of isobutene. 3a to 3c are dimeric in solution and the solid state and contain unprecedented Ga4C2H4 heteroadamantane structures in which four metal atoms are bridged by four hydrogen and two carbon atoms. In contrast, n-propyllithium gave the monomeric tetra(n-propyl)digallium compound (nPr2Ga)2C(SiMe3)-CH2-Ph (2) under similar conditions, which has two coordinatively unsaturated gallium atoms and may be applicable as a chelating Lewis acid.碳桥联双(二氯化镓)化合物(Cl₂Ga)₂C(SiR₂R′)-CH₂-Ph（1a：R=R′=Me；1b：R=Ph，R′=Me；1c：R=Me，R′=CMe₃）与四当量叔丁基锂反应，经β-消除并释放异丁烯，得到双[叔丁基(氢)二镓]化合物{[(Me₃C)(H)Ga]₂C(SiR₂R′)-CH₂-Ph}₂（3a~3c）。3a~3c在溶液与固态下均为二聚体，其结构中包含前所未有的Ga₄C₂H₄杂金刚烷骨架，该骨架由四个金属原子、四个桥联氢原子与两个碳原子构成。与之相比，正丙基锂在相同反应条件下仅生成单核四(正丙基)二镓化合物(nPr₂Ga)₂C(SiMe₃)-CH₂-Ph（2），该化合物含有两个配位不饱和的镓原子，可作为螯合型路易斯酸使用。