Synthesis of a large functional cage compound based on four Ga-Ga single bonds and its application as an oligoacceptor: on the way to bio-organogallium hybrid molecules.

The digallium compound R(2)Ga-GaR(2) (1; R=CH(SiMe(3))(2)) reacts with citracinic acid by the release of two equivalents of bis(trimethylsilyl)methane and the formation of a unique oligofunctional cage compound (2). Four Ga-Ga bonds in a tetrahedral arrangement are bridged by four spacer ligands that are located on the faces of the tetrahedron and bridge the gallium atoms of three different Ga-Ga bonds. Four pyridinium groups result from the shift of one of the three acidic protons of four citracinic acid molecules to the nitrogen atoms of the aromatic rings. The N-H groups are arranged in pairs and are capable of acting as chelating acceptors for the coordination of THF molecules (2(THF)(2)) or the nitrogen atoms of 1-deazapurine (3(OEt(2))(4)). In particular, the last reaction verifies the potential applicability of this relatively water- and air-resistant acceptor compound for the generation of bioorganometallic hybrid molecules.