Water-soluble manganese inorganic polymers: the role of carborane clusters and producing large structural adjustments from minor molecular changes.

The reaction of two different carboranylcarboxylate ligands, 1-CH3-2-CO2H-1,2-closo-C2B10H10 or 1-CO2H-1,2-closo-C2B10H11, with MnCO3 in water leads to polymeric compounds 1 a and 1 b. Both compounds have been characterized by analytical and spectroscopic techniques. Additionally, electrochemical techniques have also been used for compound 1 a. X-ray analysis revealed substantial differences between both compounds: whereas a six-coordinated Mn(II) compound with water molecules bridging two Mn(II) centers has been observed for 1 a, a square pyramidal geometry around each Mn(II) ion with terminal water molecules coordinated to each Mn(II) center has been found for 1 b. The observed differences have been attributed to the existence of different substituents, -CH3 or -H, on one of the carbon atoms of the carboranylcarboxylate ligand. The reaction of 1 a and 1 b with coordinating solvents, such as ethers or Lewis bases, leads to the formation of new compounds with low (mononuclear 4 a, 4 b; dinuclear 3 a, 3 b; and trinuclear 2 a) or high nuclearity (hybrid polymer, 5 a), due to breakage of the corresponding polymer. X-ray analysis shows that the structural core present in the polymeric materials is not maintained in the resulting compounds, with the exception of trinuclear compound 2 a. The magnetic properties of the compounds studied show weak antiferromagnetic coupling.