Intramolecular hydrogen bonding stabilizes the nuclearity of complexes. A comparative study based on the H-carborane and Me-carborane framework.

New dinuclear carboranylcarboxylate-bridged and mononuclear copper(ii) compounds containing the 1-CO2H-2-H-1,2-closo-C2B10H10 carborane ligand () have been synthesized from the previously synthesized dinuclear compound [Cu2(μ-L)4(THF)2], . Reaction of with CuSO4 in THF leads to the dinuclear compound [Cu2(μ-L)4(THF)2], . The reaction of with different terminal pyridyl ligands leads to the formation of a series of structurally analogous complexes by substitution of the terminal ligand THF (Lt = py, ; p-CF3-py, ; p-CH3-py, ), which maintain the structural Cu2(μ-O2CR)4 core in most of the cases except for o-(CH3)2-py where a mononuclear compound () is exclusively obtained. In the case of and , other dinuclear compounds [Cu2(L)4(Lt)4], and are obtained in lower yield. These compounds have been characterized using analytical, spectroscopic (NMR, IR, UV-visible) and electrochemical techniques (CV, DPV). X-ray analysis revealed a paddle-wheel structure for the main dinuclear compounds with a square-pyramidal geometry around each copper ion and the carboranylcarboxylate ions bridging two copper atoms in syn-syn mode. In the case of and there are two carboranylcarboxylate ions bridging the copper atoms in syn-anti mode whereas the other two adopt a monodentate coordination mode. The mononuclear complex obtained with the o-(CH3)-py ligand presents a square-planar structure, in which the carboranylcarboxylate ligand adoptsmonodentate coordination. The effect of the substituent group on the cluster of the carboranylcarboxylate ligands on the reactivity of compound is also discussed.