Metalltetrahydridoborate und Tetrahydridoborato-metallate, 12 [1] Zur Kenntnis von Calcium-bis(tetrahydridoborat)-bis(dimethylglykolether)/Metal Tetrahydroborates and Tetrahydroborato Metalates, 12 [1] On Calcium Bis(tetrahydroborate)-bis(dimethylglycolether)

Abstract

<jats:p>Ca(BH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>·2(CH<jats:sub>3</jats:sub>OCH<jats:sub>2</jats:sub>CH<jats:sub>2</jats:sub>OCH<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>, (1) has been prepared from Ca(BH<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>·2 THF by ligand displacement. IR and NMR data are in agreement with the presence of a nonionic BH<jats:sub>4</jats:sub> group, but a specific binding to calcium could not be deduced unambiguously. However, the X-ray structure analysis of a single crystal of 1 reveals that the lattice is built up from molecules of 1 in which each BH<jats:sub>4</jats:sub> group binds to Ca via three hydrogen atoms, and the ether forms a chelate. Therefore, calcium in 1 is decacoordinated. Taking the boron atoms as the center of gravity for the BH<jats:sub>4</jats:sub> groups one can best describe the coordination as being derived from a strongly distorted octahedron due to repulsive interactions of the BH<jats:sub>4</jats:sub> groups as well as of the "bite” of the chelating diether which im poses a O-Ca-O bond angle of ~ 67°.</jats:p>

Hydrides of the Main-Group Metals: New Variations on an Old Theme

“…397 Calcium takes up an intermediate position, yielding complexes that contain both η 2 -and η 3 -BH 4 groups. 398,399 Thus, strontium and barium tetrahydroborates have been reported by No ¨th et al 397 to form ether complexes with the stoichiometries M(BH 4 ) 2 (thf) 2 , M(BH 4 ) 2 (diglyme) 2 , and M(BH 4 ) 2 -(18-crown-6) (M ) Sr or Ba). Of these Sr(BH 4 ) 2 (thf) 2 and Ba(BH 4 ) 2 (thf) 2 are infinite chain coordination polymers in the solid state; successive metal centers are bridged by two BH 4 ligands, each coordinated in η 3 fashion to both metals, and the coordination sphere of the metal is completed by two mutually trans thf ligands to give an overall coordination number of 14 (two thf oxygens and four sets of three bridging hydrides).…”

“…Rather more specific M···H interactions are implied by the structures of some of the tetrahydroborate derivatives of these metals, with η 2 -BH 4 ligands predominating for the smaller magnesium center − and η 3 -BH 4 ligands for the larger strontium and barium ones . Calcium takes up an intermediate position, yielding complexes that contain both η 2 - and η 3 -BH 4 groups. , Thus, strontium and barium tetrahydroborates have been reported by Nöth et al . to form ether complexes with the stoichiometries M(BH 4 ) 2 (thf) 2 , M(BH 4 ) 2 (diglyme) 2 , and M(BH 4 ) 2 (18-crown-6) (M = Sr or Ba).…”

Nanocomposite polymer electrolyte for rechargeable magnesium batteries

“…The 25 Mg NMR peak shapes is also informative regarding the dissociation of Mg(BH 4 ) 2 in the series of glymes. The line width-measured through the full-width-at-half-maximum [93,94]. The longer triglyme and tetraglyme, with more ether oxygens and conformation flexibility, may instead adopt more numerous modes of coordination to the cations, with some or all of the ether oxygens from one or two glyme molecules coordinated, which may vary the local environment of the Mg 2+ cations to a greater extent (for both the solvent and anion coordination due to steric factors) thus explaining the broad peak widths observed for the solutions with these glymes.…”

Synthesis and structure of divalent thulium borohydrides, and their application in ε-caprolactone polymerisation

“…The coordination geometry can be described as distorted octahedral, with the borohydrides occupying two coordination positions in a cis configuration. The structure is isomorphous and isostructural with that of [Ca(BH 4 ) 2 (DME) 2 ], 9 owing to the similar sizes of Ca 2+ and Tm 2+ with ionic radii of 1.00 and 1.03 A ˚in 6-coordinate environments, respectively. 10 1 is less stable than [TmI 2 (DME) 3 ].…”