Tetrakis(μ3-9-oxa-10-boraanthracen-10-olato)tetrakis[(diethyl ether)lithium]

Daniel Franz; Hans-Wolfram Lerner; Dominik Büttner; Michael Bolte

doi:10.1107/S1600536811041201

. 2011 Oct 12;67(Pt 11):m1525. doi: 10.1107/S1600536811041201

Tetrakis(μ₃-9-oxa-10-boraanthracen-10-olato)tetrakis[(diethyl ether)lithium]

Daniel Franz ^a, Hans-Wolfram Lerner ^a, Dominik Büttner ^a, Michael Bolte ^a,^*

PMCID: PMC3246952 PMID: 22219772

Abstract

The title compound, [Li₄O₄(C₁₂H₈BO)₄(C₄H₁₀O)₄], features a Li₄O₄ cube. Each Li atom in the cube is additionally coordinated by a diethyl ether molecule and each O atom in the cube carries a 9-oxa-10-boraanthracene residue. The crystal studied was a non-merohedral twin [twin law (-1 0 0 / 0 0 1 / 0 1 0); the contribution of the major twin component refined to 0.553 (3)] emulating apparent tetragonal symmetry, whereas the actual crystal system is just orthorhombic.

Related literature

For chalcogenolate ligands used to stabilize transition metal centers, see: Wolczanski (2009 ▶); Kückmann et al. (2005 ▶, 2008 ▶, 2010 ▶). For synthetic details, see: Davidson & French (1960 ▶); Mikoshiba et al. (2003 ▶); Zuideveld et al. (2002 ▶); Knizek & Nöth (2000 ▶). For related structures, see: Kückmann et al. (2007 ▶); Lerner et al. (2002 ▶).

Experimental

Crystal data

[Li₄O₄(C₁₂H₈BO)₄(C₄H₁₀O)₄]
M _r = 1104.22
Orthorhombic,
a = 21.4805 (8) Å
b = 17.6053 (10) Å
c = 17.5723 (8) Å
V = 6645.3 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 173 K
0.30 × 0.30 × 0.25 mm

Data collection

Stoe IPDS II two-circle diffractometer
77138 measured reflections
6262 independent reflections
4842 reflections with I > 2σ(I)
R _int = 0.114

Refinement

R[F ² > 2σ(F ²)] = 0.077
wR(F ²) = 0.204
S = 1.04
6262 reflections
758 parameters
29 restraints
H-atom parameters constrained
Δρ_max = 1.10 e Å⁻³
Δρ_min = −0.35 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2001 ▶); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811041201/bg2423sup1.cif

e-67-m1525-sup1.cif^{(80.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811041201/bg2423Isup2.hkl

e-67-m1525-Isup2.hkl^{(306.5KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

In this study, the accordance of the structural characteristics between the alkali metal salts of borinic acids, M⁺[EBR₂]^- (E = O), and the related silyl chalcogenolates M⁺[ESiR₃]^- (E = O, S, Se, Te) is taken into account. It has been shown that chalcogenolate ligands of the type [ESiR₃]^- (E = O, S, Se, Te) were used to stabilize transition metal centers (Wolczanski, 2009; Kückmann et al., 2005, 2008, and 2010). These ligands have also been applied in the field of macromolecular chemistry. Normally, transition metal complexes possess 6 e^- chalcogenolate ligands in a µ₃ binding mode. Recently, however, we have shown that the anion of the mixed valence Mn(I/II) complex [Na(thf)₆][(OC)₃Mn(µ-SSitBu₃)₃MnSSitBu₃] contains a terminal thiolate ligand with a linear Mn—S—Si unit (Kückmann et al., 2008). The prerequisite for electronic communication between the metal center and the ligand is thus fulfilled. By an attempt to synthesize compound III (Fig. 1) we obtained as a by-product single crystals of the title compound (IV). The starting materials I and II were synthesized by modification of the procedures reported in the literature (Mikoshiba et al., 2003; Davidson & French, 1960; Zuideveld et al., 2002). IV displays a heterocubane structure in the solid state. Related structural motifs are found in the silyl chalcogenolates (Na[OSitBu₃])₄, (Na[OSiPhtBu₂])₄, and ([Na(thf)][OSiMePh₂])₄ (Lerner et al. 2002; Kückmann et al., 2007). In conclusion, the solid-state structure of IV provides further evidence for the diagonal relationship between B and Si.

The title compound (Fig. 2) features a Li₄O₄ cube. Each Li atom in the cube is additionally coordinated by a diethyl ether molecule and each O atom in the cube carries a 9-oxa-10-bora-anthryl residue.

Experimental

All transformations were carried out under an atmosphere of dry nitrogen using standard Schlenk techniques and carefully dried solvents. The ¹¹B NMR spectrum was recorded on a Bruker Avance 300. The borinic acid II (1.18 g, 6.0 mmol) was dissolved in Et₂O (40 ml) and cooled to 0 °C. Under vigorous stirring a solution of Li[AlH₄] (9 mmol) in Et₂O (19 mL) was added dropwise over a period of 30 min (beforehand, few small crystallites of 2,2'-biquinoline had been added to the ethereal Li[AlH₄] solution as a color indicator for the consumption of Li[AlH₄]). The mixture was allowed to warm to room temperature over night yielding a pale yellow suspension. In the ¹¹B NMR spectrum (in C₆D₆/THF (1:1), referenced to external BF₃^.Et₂O) a triplet was observed at -24.0 ppm (¹J_BH = 78 Hz) which indicated conversion into the putative 9,9-dihydrido-9-oxa-10-borataanthracene (III) (cf. lithium 9,9-dihydrido-9-boratafluorene: δ(¹¹B) = -22.3 (¹J_-H = 77 Hz) in CDCl₃) (Knizek & Nöth, 2000). The solid was removed by filtration. The clear solution was subject to a crystallization experiment implementing gas phase diffusion exchange of solvent with a reservoir containing a mixture of hexane/pentane (15 ml/15 ml). After three weeks a few cubic crystals of the title compound (IV) were obtained.