Hydrocarbon-Soluble Calcium Hydride: A "Worker-Bee" in Calcium Chemistry

The reactivity of the hydrocarbon‐soluble calcium hydride complex [{CaH(dipp‐nacnac)(thf)}2] (1; dipp‐nacnac=CH{(CMe)(2,6‐iPr2C6H3N)}2) with a large variety of substrates has been investigated. Addition of 1 to CO and CN functionalities gave easy access to calcium alkoxide and amide complexes. Similarly, reduction of the CN bond in a cyanide or an isocyanide resulted in the first calcium aldimide complexes [Ca{NC(H)R}(dipp‐nacnac)] and [Ca{C(H)NR}(dipp‐nacnac)], respectively. Complexation of 1 with borane or alane Lewis acids gave the borates and alanates as contact ion pairs. In reaction with epoxides, nucleophilic ring‐opening is observed as the major reaction. The high reactivity of hydrocarbon‐soluble 1 with most functional groups contrasts strongly with that of insoluble CaH2, which is essentially inert and is used as a common drying agent. Crystal structures of the following products are presented: [{Ca{OC(H)Ph2}(dipp‐nacnac)}2], [{Ca{NC(H)Ph}(dipp‐nacnac)}2], [{Ca{C(H)NC(Me)2CH2C(Me)3}(dipp‐nacnac)}2], [{Ca{C(H)NCy}(dipp‐nacnac)}2], [Ca(dipp‐nacnac)(thf)]+[H2BC8H14]− and [{Ca(OCy)(dipp‐nacnac)}2]. The generally smooth and clean conversions of 1 with a variety of substrates and the stability of most intermediates against ligand exchange make 1 a valuable key precursor in the syntheses of a wide variety of β‐diketiminate calcium complexes. Busy as a bee: Whereas CaH2 is essentially inert towards many functional groups, reactions of the well‐defined hydrocarbon‐soluble calcium hydride complex 1 with numerous substrates are smooth and give easy access to a variety of calcium complexes, thus underscoring its importance as a precursor in calcium chemistry.