Reactions of tetrakis[bis(trimethylsilyl)methyl]digallane(4) with carboxylic acids - Substituent exchange and bridging of the Ga-Ga bond by two carboxylato groups

Yellow tetrakis[bis(trimethylsilyl)methyl]digallane(4) 1 reacts with two equivalents of the carboxylic acids RCOOH (R = -C6H5, -p-BrC6H4, -3,5-Me(2)C(6)H(3), -CMe(3)) to yield almost quantitatively colorless products in which two bis(trimethylsilyl)methyl groups are replaced by two carboxylato ligands. As shown by a crystal structure determination with the 4-bromo-phenyl derivative (3), the Ga-Ga bond is bridged by both carboxylato groups in a chelating manner. The Ga-Ga distance is shortened to 238.5(2) pm (1: 254.1(1) pm) and the coordination number of the Ga atoms increased to four.