?-Diketiminate calcium hydride complexes: the importance of solvent effects.

Title ?-Diketiminate calcium hydride complexes: the importance of solvent effects.
Authors A. Causero; G. Ballmann; J. Pahl; C. Färber; J. Intemann; S. Harder
Journal Dalton Trans
DOI 10.1039/c6dt04659b
Abstract

A series of (DIPPnacnac)CaN(SiMe3)2·S complexes (DIPPnacnac = HC[C(Me)N(2,6-iPr-C6H3)]2; S = solvent) could be obtained by the addition of S = THF, DME or N-Me-morpholine (Morph) to (DIPPnacnac)CaN(SiMe3)2·OEt2 or (DIPPnacnac)CaN(SiMe3)2. Crystal structures for complexes with S = DME and Morph are compared to literature-known structures with S = none, THF or Et2O. Bulkier and weaker Lewis bases like the tertiary amines Et3N, TMEDA and DABCO did not interact with (DIPPnacnac)CaN(SiMe3)2. The reaction of (DIPPnacnac)CaN(SiMe3)2 with PhSiH3 gave conversion to a calcium hydride complex that dismutated in (DIPPnacnac)2Ca and CaH2. The reaction of (DIPPnacnac)CaN(SiMe3)2·S with PhSiH3 gave [(DIPPnacnac)CaH·S]2 for S = THF, Et2O or N-Me-morpholine (Morph). For S = DME, high reaction temperatures were needed and dismutation into (DIPPnacnac)2Ca and CaH2 was observed. Extensive NMR investigations (VT-NMR and PGSE) confirm the dimeric nature of [(DIPPnacnac)CaH·THF]2 in aromatic solvents or in THF. Thermal decomposition of [(DIPPnacnac)CaH·THF]2 (release of H2 at 200 °C) is compared to that of Mg and Zn analogues. Weakly coordinating Et2O in [(DIPPnacnac)CaH·OEt2]2 could be replaced by THF, Morph or DABCO but not with Et3N. The addition of TMEDA led to the formation of CaH2 and unidentified products. The addition of DME led to the decomposition of Et2O and complex [(DIPPnacnac)CaOEt]2 was obtained. Crystal structures of the following compounds are presented: (DIPPnacnac)CaN(SiMe3)2·S (S = Morph, DME), [(DIPPnacnac)CaH·S]2 (S = Et2O, Morph and DABCO) and [(DIPPnacnac)CaOEt]2. Although bulky ligands have long been thought to be the key to the stabilization of calcium hydride complexes, the presence of a polar, strongly coordinating, co-solvent is also crucial.

Citation A. Causero; G. Ballmann; J. Pahl; C. Färber; J. Intemann; S. Harder.?-Diketiminate calcium hydride complexes: the importance of solvent effects.. Dalton Trans. 2017. doi:10.1039/c6dt04659b

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Calcium

See more Calcium products. Calcium (atomic symbol: Ca, atomic number: 20) is a Block S, Group 2, Period 4 element with an atomic weight of 40.078. The number of electrons in each of Calcium's shells is [2, 8, 8, 2] and its electron configuration is [Ar]4s2. Calcium Bohr ModelThe calcium atom has a radius of 197 pm and a Van der Waals radius of 231 pm. Calcium was discovered and first isolated by Sir Humphrey Davy in 1808. It is the fifth most abundant element in the earth's crust and can be found in minerals such as dolomite, gypsum, plagioclases, amphiboles, pyroxenes and garnets. In its elemental form, calcium has a dull gray-silver appearance. Calcium is a reactive, soft metal that is a member of the alkaline earth elements. Elemental CalciumIt frequently serves as an alloying agent for other metals like aluminum and beryllium, and industrial materials like cement and mortar are composed of calcium compounds like calcium carbonate. It is also an biologically essential substance found in teeth, bones, and shells. The name "calcium" originates from the Latin word "calics," meaning lime.

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