title: β-Diketiminate calcium hydride complexes: the importance of solvent effects.
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·OEt2or (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)2with PhSiH3gave conversion to a calcium hydride complex that dismutated in (DIPPnacnac)2Ca and CaH2. The reaction of (DIPPnacnac)CaN(SiMe3)2·S with PhSiH3gave [(DIPPnacnac)CaH·S]2for S = THF, Et2O or N-Me-morpholine (Morph). For S = DME, high reaction temperatures were needed and dismutation into (DIPPnacnac)2Ca and CaH2was observed. Extensive NMR investigations (VT-NMR and PGSE) confirm the dimeric nature of [(DIPPnacnac)CaH·THF]2in aromatic solvents or in THF. Thermal decomposition of [(DIPPnacnac)CaH·THF]2(release of H2at 200 °C) is compared to that of Mg and Zn analogues. Weakly coordinating Et2O in [(DIPPnacnac)CaH·OEt2]2could be replaced by THF, Morph or DABCO but not with Et3N. The addition of TMEDA led to the formation of CaH2and unidentified products. The addition of DME led to the decomposition of Et2O and complex [(DIPPnacnac)CaOEt]2was 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.
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Andrea
authors.initials: A
authors.lastname: Causero
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Gerd
authors.initials: G
authors.lastname: Ballmann
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Pahl
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Färber
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Intemann
authors.affiliation: Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany. sjoerd.harder@fau.de.
authors.forename: Sjoerd
authors.identifier: http://orcid.org/0000-0002-3997-1440
authors.initials: S
authors.lastname: Harder