The closo-dodecahydrododecaborate [NEt3H]2[B12H12] has been prepared on a lab scale by an improved synthesis from cheap and readily available starting materials Na[BH4] and I2 in diglyme (diethylene glycol dimethyl ether). Subsequent chlorination with elemental chlorine in aqueous solution at normal pressure yielded the per-chlorinated weakly coordinating [B12Cl12]2- anion. By simple metathesis reaction a variety of useful salts [cation]2[B12Cl12] (cation=[NEt3H]+, [NBu4]+, Li+, Na+, K+, Cs+) is available. These salts are useful starting materials, which have the potential to open up the chemistry of [B12Cl12]2- as a weakly coordinating dianion. Exemplarily, they were used in further reactions to prepare [NO]2[B12Cl12], [PPN]2[B12Cl12], and [CPh3]2[B12Cl12]. The crystal structures of Cs2[B12Cl12].SO2, [CPh3]2[B12Cl12].2C2H4Cl2, and [CPh3]2[B12Cl12].2SO2 and preliminary crystal structures of [NO]2[B12Cl12].SO2 and [PPN]2[B12Cl12].CH2Cl2 were determined. The crystal structure of the SO2 solvate Cs2[B12Cl12].SO2 is related to the crystal structure of solvent free Cs2[B12Cl12]. [CPh3]2[B12Cl12].2C2H4Cl2 and [CPh3]2[B12Cl12].2SO2 have very similar structures in the solid state. In both cases the [CPh3]+ cations form only very weak contacts to the [B12Cl12]2- anion and SO2 or C2H4Cl2 solvent molecules respectively. The averaged experimental B-B (178.7 pm) and B-Cl (178.9 pm) bond lengths within [B12Cl12]2- are essentially unchanged in all determined structures and are reproduced well by PBE0/TZVPP quantum chemical calculations (B-B 178.6 pm, B-Cl 179.3 pm). All results indicate that [B12Cl12]2- is a readily accessible weakly-coordinating dianion.
In this study, we investigated the tetraalkylammonium salts of the weakly coordinating fluorinated alkoxyaluminates [pftb](-) ([Al(O(C(CF(3))(3))(4)](-)), [hfip](-) ([Al(OC(H)(CF(3))(2))(4)](-)) and [hftb](-) ([Al(OC(CH(3))(CF(3))(2))(4)](-)) in order to obtain information on their undisturbed spectral and structural properties, as well as to study their electrochemical behavior (i.e., conductivities in non-polar solvents and electrochemical windows). Several of the compounds qualify as ionic liquids with melting points as low as 42 degrees C for [NBu(4)](+)[hfip](-). Simple and almost quantitative metathesis reactions yielding these materials in high purity were developed. These [NR(4)](+) salts serve as model compounds for undisturbed anions and their vibrational spectra--together with simulated spectra based on quantum chemical DFT calculations--were used for the clear assignment of the anion bands. Besides, the ion volumes of the anions (V(ion)([pftb](-)) = 0.736 nm(3), V(ion)([hftb](-)) = 0.658 nm(3), V(ion)([hfip](-)) = 0.577 nm(3)) and their decomposition pathways in the mass spectrometric measurements have been established. The salts are highly soluble in non-polar solvents (up to 1.09 mol L(-1) are possible for [NBu(4)](+)[hftb](-) in CH(2)Cl(2) and 0.41 mol L(-1) for [NBu(4)](+)[hfip](-) in CHCl(3)) and show higher molar conductivities if compared to [NBu(4)](+)[PF(6)](-). The electrochemical windows of CH(2)Cl(2), CH(3)CN and 1,2-F(2)C(6)H(4) using the [NBu(4)](+) aluminate electrolytes are up to +0.5 V/-0.7 V larger than those using the standard [NBu(4)](+)[PF(6)](-).
The new isotypic intermetallic phases Ba 5 M III 5 M IV (M III = Al, Ga; M IV = Sn, Pb) have been synthesized from stoichiometric amounts of the elements at maximum temperatures of 900 to 1000 • C. They crystallize in the hexagonal space group P6m2 (Ba 5 Al 5 Sn: a = 605.05(8), c = 1109.0(2) pm, R1 = 0.0137; Ba 5 Ga 5 Sn: a = 599.45(5), c = 1086.00(7) pm, R1 = 0.0485; Ba 5 Al 5 Pb: a = 606.9(2), c = 1112.0(4) pm, R1 = 0.0409 and Ba 5 Ga 5 Pb: a = 601.76 (7), c = 1091.51(13) pm, R1 = 0.0295), forming a new structure type. Similar to the Zintl phases Ba 2 M IV (Co 2 Si structure type, orthorhombic, space group Pnma; Ba 2 Sn: a = 861.52(14), b = 569.85(9), c = 1056.9(2) pm, R1 = 0.0217 and Ba 2 Pb: a = 865.12(13), b = 569.1(2), c = 1061.8(2) pm, R1 = 0.0470), these new ternary phases contain isolated M IV atoms (coordinated by 11 Ba atoms). In addition, sheets of 3-and 4-bonded Al/Ga atoms similar to those in Ba 3 Al 5 are present. In accordance with this, a formal subdivision of Ba 5 M III 5 M IV into Ba 3 M III 5 · Ba 2 M IV can be performed to describe the observed intergrowth or chemical twinning of two different binary intermetallics to give the new ternary compounds. Beyond structural aspects, also the nature of the chemical bonding (as studied by FP-LAPW calculations) in these new, non-electron precise compounds in the vicinity of the Zintl border can be interpreted in this vein.
Structure D 2000Ba 5 (Al/Ga) 5 (Sn/Pb): New Compounds at the Zintl Border. -The new title phases are synthesized from stoichiometric mixtures of the elements at 900-1000 °C. The isotypic phases Ba5Al5Sn, Ba5Ga6Sn, Ba5Al5Pb and Ba5Ga5Pb crystallize with a new structure type in the hexagonal space group P6m2 with Z = 1 (single crystal XRD). Similar to the Zintl phases Ba2M (M: Sn, Pb; Co2Si structure type, orthorhombic, space group Pnma, Z = 4), the new ternary phases contain isolated M atoms coordinated by 11 Ba atoms. In addition, sheets of 3-and 4-bonded Al/Ga atoms similar to those in Ba3Al5 are present. The observed intergrowth is in accordance with the formula Ba3(Al,Ga)5·Ba2M. -(GUTTSCHE, K.; ROSIN, A.; WENDORFF, M.; ROEHR*, C.; Z. Naturforsch., B: Chem. Sci. 61 (2006) 7, 846-853; Inst. Anorg. Anal. Chem., Albert-Ludwigs-Univ., D-79104 Freiburg/Br., Germany; Ger., Abstr. Eng.) -Schramke 42-002
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