Bis- and Tris(dimethylgallyl)benzenes: Synthesis, Solid-State Structures, and Redistribution Reactions

Benzene derivatives containing dimethylgallyl substituents in 1,3- (compounds 5 and 6), 1,4- (compound 9), and 1,3,5-position (compound 12) were prepared by reaction of the corresponding chloromercuriobenzenes with an excess of trimethylgallium at higher temperatures. These compounds decompose in solution at room temperature and in the solid state upon mild heating with elimination of trimethylgallium to give oligomeric condensation products of unknown detailed composition. These condensation products can be transformed back into the starting compounds by treatment with an excess of trimethylgallium at higher temperatures. Highly air-sensitive crystals of 5, 6, 9, and 12 suitable for an X-ray analysis are obtained from trimethylgallium as solvent. The X-ray crystallographic studies revealed the presence of higher coordinate gallium atoms, which lead to the formation of strand- or sheet-like polymers. A trigonal-bipyramidal coordination sphere is observed for the gallium atoms in 9. A distorted tetrahedral coordination is found for the gallium atoms in 5, 6, and 12. The latter compounds possess asymmetric aryl-dimethylgallyl bridging units.

通过相应氯汞苯与过量三甲基镓在高温条件下的反应，制备得到了1,3-位（化合物5、6）、1,4-位（化合物9）以及1,3,5-位带有二甲基镓基取代基的苯衍生物（化合物12）。这类化合物在室温溶液中会发生分解，固态时经温和加热也会分解，过程中脱除三甲基镓，生成组成细节尚未明确的低聚缩合产物。该类缩合产物可在高温下与过量三甲基镓反应，重新转化为初始原料化合物。以三甲基镓为溶剂，可获得适用于X射线衍射分析（X-ray analysis）的5、6、9、12的高空气敏性晶体。X射线晶体学研究显示，体系中存在高配位镓原子，该结构特征促使链状或片状聚合物的形成。化合物9中的镓原子呈现三角双锥配位构型。化合物5、6与12中的镓原子则为畸变四面体配位构型，该类后述化合物含有不对称芳基-二甲基镓基桥联单元。