Jump to main content
Jump to site search

Issue 6, 2017
Previous Article Next Article

β-Diketiminate calcium hydride complexes: the importance of solvent effects

Author affiliations

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.

Graphical abstract: β-Diketiminate calcium hydride complexes: the importance of solvent effects

Back to tab navigation

Supplementary files

Publication details

The article was received on 09 Dec 2016, accepted on 16 Jan 2017 and first published on 23 Jan 2017


Article type: Paper
DOI: 10.1039/C6DT04659B
Dalton Trans., 2017,46, 1822-1831

  •   Request permissions

    β-Diketiminate calcium hydride complexes: the importance of solvent effects

    A. Causero, G. Ballmann, J. Pahl, C. Färber, J. Intemann and S. Harder, Dalton Trans., 2017, 46, 1822
    DOI: 10.1039/C6DT04659B

Search articles by author

Spotlight

Advertisements