The Formation of Macrocyclic Compounds Containing Two Ga–Ga Bonds by the Reaction of Tetraalkyldigallane(4) R2Ga–GaR2 [R = CH(SiMe3)2] with Dicarboxylic Acids

Tetrakis[bis(trimethylsilyl)methyl]digallane(4) 1 reacts with dicarboxylic acids like 1,4-benzenedi(methylcarboxylic) acid, 1,4-cyclohexanedicarboxylic acid, 1,6-hexanedicarboxylic acid, and 1,4-butanedicarboxylic acid (adipinic acid) by the release of two equivalents of bis(trimethylsilyl)methane and the retention of the Ga–Ga bond. Products are formed, in which the very short Ga–Ga bonds (237.7 pm on average) are bridged by two carboxylato groups. Two of these moieties are connected in each compound by two spacers (dimethylbenzene, cyclohexane, hexane, or butane) to form macrocyclic compounds with up to 22 atoms in the resultant heteroatomic rings. The dimeric form is also observed in solution. For comparison, the synthesis and structure of the product of the reaction of 1 with 1-adamantanecarboxylic acid is included, which also has the Ga–Ga bond (239.1 pm) bridged by two carboxylato groups.