Calcium Hydride Cation [CaH](+) Stabilized by an NNNN-type Macrocyclic Ligand: A Selective Catalyst for Olefin Hydrogenation
Résumé
Reaction of dibenzyl calcium complex [Ca(Me(4)TACD)(CH2Ph)(2)], containing the neutral NNNN-type macrocyclic ligand Me(4)TACD (Me(4)TACD=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane), with triphenylsilane gave the cationic dinuclear calcium hydride [Ca2H2(Me(4)TACD)(2)](PhCHSiPh3)(2) which was characterized by NMR spectroscopy and single-crystal X-ray diffraction. The cation can be regarded as the ligand-stabilized dimeric form of hypothetical [CaH](+). Hydrogenolysis of benzyl calcium cation [Ca(Me(4)TACD)(CH2Ph)(thf)](+) gave dicationic calcium hydrides [Ca2H2(Me(4)TACD)(2)][BAr4](2) (Ar=C6H4-4-Bu-t; C6H3-3,5-Me-2) containing weakly coordinating anions. In THF, they catalyzed the isotope exchange of H-2 and D-2 to give HD and the hydrogenation of unactivated 1-alkenes.