Abstract
The syntheses of calcium carborates, Ca[HexCB(11)Cl(11)](2), 1, Ca[HCB(11)Cl(11)](2), 2, and Ca[MeCB(11)Cl(11)](2)·2(o-DFB), 3·2(o-DFB), (o-DFB = 1,2-difluorobenzene) including the structure of 2·4(o-DFB) are described. The large size of the Ca(2+) cation is reflected by the coordination geometry with the Ca center being coordinated by three Cl donors from each of the carborate anions and one F donor from each of the two coordinated solvent molecules. Based on (11)B NMR and DOSY NMR studies, the salts 1, 2 and 2·2(o-DFB) form close ion pairs in PhBr and o-DFB solutions. The Fluoride Ion Affinities (FIA) in PhBr for the salts 1 and 2·2(o-DFB) were DFT-calculated (ωB97XD/6-31 + G**) at 211.3 kJ mol(-1) and 217.5 kJ mol(-1), respectively, which is below that of the landmark Lewis acid B(C(6)F(5))(3) (241.5 kJ mol(-1)). The Ca(2+) center in salt 1 is sufficiently Lewis acidic to coordinate 1,5-cyclooctadiene (1,5-COD) and 2,6-octadiyne and to catalyze the hydrosilylation of 1-hexene and several alkynes, albeit slowly. Compound 1 also displays moderate activity as a catalyst for transfer hydrogenation catalysis and carbonyl-olefin metathesis (COM), a first for Ca compounds.