Darstellung, 11B-, 13C-, 1H-NMR- und Schwingungsspektren von Monoethoxyhydro-closo-Dodecaborat(2–) sowie Kristallstruktur von [(C5H5N)2CH2][B12H11(OC2H5)]

Preparation, ¹¹B, ¹³C, ¹H NMR and Vibrational Spectra of Monoethoxyhydro-closo-dodecaborate(2–), and the Crystal Structure of [(C₅H₅N)₂CH₂][B₁₂H₁₁(OC₂H₅)] By treatment of Na₂[B₁₂H₁₂] with dry HF in ethanol Na₂[B₁₂H₁₁(OC₂H₅)] is formed which has been separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from the starting compound and by-products. The X-ray structure determination of [(C₅H₅N)₂CH₂][B₁₂H₁₁(OC₂H₅)] (monoclinic, space group P2₁/m, a = 9.1906(3), b = 12.6612(8), c = 9.3640(12) Å, β = 112.947(6)°, Z = 2) reveals the complete ordering of the anion sublattice. The ¹¹B nmr spectrum exhibits the characteristic feature (1:5:5:1) of a mono substituted B₁₂ cage with a strong down-field shift of ipso-B at +6.5 ppm. In the ¹³C nmr spectrum a triplet at 67.9 ppm of the methylene group and a quartet at 19.5 ppm of the methyl group is observed. Correspondingly, the ¹H nmr spectrum shows two multiplets at 3.7 and 1.3 as expected for an ethoxy substituent, and a multiplet at 2.1 ppm due to the protons of the boron cluster. The i.r. and Raman spectra exhibit strong CH stretching vibrations between 2 963 and 2 863 cm^?1, and in the i.r. spectrum the CO and BO stretching frequencies of the B? O? C bridge are observed at 1 175 and 1 140 cm^?1.     

1‐Oxa‐nido‐dodecaborate [OB11H12]− from the Controlled Oxidation of the closo‐Borates [B11H11]2− and [B12H12]2−

The closo‐dodecaborate [B₁₂H₁₂]^2? is degraded at room temperature by oxygen in an acidic aqueous solution in the course of several weeks to give B(OH)₃. The degradation is induced by Ag²⁺ ions, generated from Ag⁺ by the action of H₂S₂O₈. Oxa‐nido‐dodecaborate(1?) is an intermediate anion, that can be separated from the reaction mixture as [NBzlEt₃][OB₁₁H₁₂] after five days in a yield of 18 %. The action of FeCl₃ on the closo‐undecaborate [B₁₁H₁₁]^2? in an aqueous solution gives either [B₂₂H₂₂]^2? (by fusion) or nido‐B₁₁H₁₃(OH)^? (by protonation and hydration), depending on the concentration of FeCl₃. In acetonitrile, however, [B₁₁H₁₁]^2? is transformed into [OB₁₁H₁₂]^? by Fe³⁺ and oxygen. The radical anions [B₁₂H₁₂] ^{˙ ?} and [B₁₁H₁₁] ^{˙ ?} are assumed to be the primary products of the oxidation with the one‐electron oxidants Ag²⁺ and Fe³⁺, respectively. These radical anions are subsequently transformed into [OB₁₁H₁₂]^? by oxygen. The crystal structure analysis shows that the structure of [OB₁₁H₁₂]^? is derived from the hypothetical closo‐oxaborane OB₁₂H₁₂ by removal of the B3 vertex, leaving a non‐planar pentagonal aperture with a three‐coordinate O vertex, as predicted by NMR spectra and theory.     

Darstellung und Charakterisierung von Thio- und Seleno-closo-hexaboraten sowie Kristallstruktur von (Ph4P)[B6H5Hfac(SH)]

Synthesis and Characterization of the Thio- and Seleno- closo -hexaborates and the Crystal Structure of (Ph₄P)[B₆H₅H^fac(SH)] By treatment of [B₆H₅(SCN)]^2– and [B₆H₅(SeCN)]^2– in strong basic medium the chalcogeno-closo-hexaborates [B₆H₅S]^3– and [B₆H₅Se]^3– are formed. An X-ray structure determination has been performed on the doubly protonated compound (Ph₄P)[B₆H₅H^fac(SH)] (triklin, P 1¯, a = 7.436(2), b = 12.850(2), c = 13.0594(12) Å, α = 93.131(8), β = 94.47(3), γ = 90.40(3)°, Z = 2). The ¹¹B NMR spectra exhibit the characteristic pattern of a monosubtituted B₆ octahedron with the intensity ratio 1 : 4 : 1. The chemical shifts are systematically dependent on the protonation at a facet of the B₆ clusters with H^fac or at the chalcogen atom. Whereas the signals of the equatorial nuclei are nearly at equal positions from –16.0 to –16.9 ppm, the ipso-B atoms absorb in the low field region from –4.7 to –11.7 ppm, and the antipodal-B atoms in the high field from –21.6 to –28.0 ppm. In the IR and Raman spectra the typical B–X and B₆-X stretching vibrations are observed from X = S at 1089 and 383, for X = Se at 1076 and 292 cm^–1, respectively.     

Darstellung, 11B-NMR-, Schwingungsspektren und Kristallstruktur von [(C5H5N)2CH2][1-(O2N)B10H9]

Preparation, ¹¹B NMR, Vibrational Spectra, and Crystal Structure of [(C₅H₅N)₂CH₂][1-(O₂N)B₁₀H₉] By reaction of [B₁₀H₁₀]^2? in aqueous acetonitrile with a saturated solution of NO₂ in dichloromethane [1-(O₂N) · B₁₀H₉]^2? and [B₁₀H₉(NO)B₁₀H₉]^3? are formed which can be separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from the starting compound. The X-ray structure determination of [(C₅H₅N)₂CH₂][1-(O₂N)B₁₀H₉] (triclinic, space group P1 , a = 7.1530(9), b = 8.3753(8), c = 15.198(2) Å, α = 96.00(1), β = 95.48(1), γ = 95.60(1)°, Z = 2) reveals the coordination of the NO₂ group via N with a B1? N distance of 1.535(5) Å and an O2? N? O1 angle of 119.3(3)°. The ¹¹B NMR spectrum exhibits the characteristic feature (1 : 1 : 4 : 4) of an apical monosubstituted B₁₀ cluster with a strong downfield shift of the ipso-B atom at +13.4 ppm. The IR and Raman spectra show strong NO stretching vibrations at 1381 und 1420 cm^?1.     

Dodekahydro‐closo‐dodekaborate der schweren Erdalkalimetalle aus wäßriger Lösung: Ca(H2O)7[B12H12] · H2O,Sr(H2O)8[B12H12] und Ba(H2O)6[B12H12]

Dodecahydro‐ closo ‐dodecaborates of the Heavy Alkaline‐Earth Metals from Aqueous Solution: Ca(H₂O)₇[B₁₂H₁₂] · H₂O, Sr(H₂O)₈[B₁₂H₁₂], and Ba(H₂O)₆[B₁₂H₁₂] The crystalline hydrates of the heavy alkaline earth metal dodecahydro‐closo‐dodecaborates (M[B₁₂H₁₂] · n H₂O, n = 6–8; M = Ca, Sr, Ba) are easily accessible by reaction of an aqueous (H₃O)₂[B₁₂H₁₂] solution with an alkaline earth metal carbonate (MCO₃). By isothermic evaporation of the respective aqueous solution we obtained colourless single crystals which are characterized by X‐ray diffraction at room temperature. The three compounds Ca(H₂O)₇[B₁₂H₁₂] · H₂O (orthorhombic, P2₁2₁2₁; a = 1161.19(7), b = 1229.63(8), c = 1232.24(8) pm; Z = 4), Sr(H₂O)₈[B₁₂H₁₂] (trigonal, R3; a = 1012.71(6), c = 1462.94(9) pm; Z = 3) and Ba(H₂O)₆[B₁₂H₁₂] (orthorhombic, Cmcm; a = 1189.26(7) pm, b = 919.23(5) pm, c = 1403.54(9) pm; Z = 4) are neither formula‐equal nor isostructural. The structure of Sr(H₂O)₈[B₁₂H₁₂] is best described as a NaCl‐type arrangement, Ba(H₂O)₆[B₁₂H₁₂] rather forms a layer‐like and Ca(H₂O)₇[B₁₂H₁₂] · H₂O a channel‐like structure. In first sphere the alkaline earth metal cations Ca²⁺ and Sr²⁺ are coordinated by just seven and eight oxygen atoms from the surrounding water molecules, respectively. A direct coordinative influence of the quasi‐icosahedral [B₁₂H₁₂]^2– cluster anions becomes noticeable only for the Ba²⁺ cations (CN = 12) in Ba(H₂O)₆[B₁₂H₁₂]. The dehydratation of the alkaline earth metal dodecahydro‐closo‐dodecaborate hydrates has been shown to take place in several steps. Thermal treatment leads to the anhydrous compounds Ca[B₁₂H₁₂], Sr[B₁₂H₁₂] and Ba[B₁₂H₁₂] at 224, 164 and 116 °C, respectively.     

Darstellung und schwingungsspektroskopische Untersuchung von [H3B?Se?Se?BH3]2− und [H3B-μ2-Se(B2H5)]− Kristallstruktur und theoretische Untersuchung der Molekülstruktur von [H3B-μ2-Se(B2H5)]−

Synthesis and Vibrational Spectroscopic Investigation of [H₃B? Se? Se? BH₃]^2? and [H₃B-μ₂-Se(B₂H₅)]^? Crystal Structure and Theoretical Investigation of the Molecular Structure of [H₃B-μ₂-Se(B₂H₅)]^? M₂[H₃B? Se? Se? BH₃] 1 is produced by the reaction between elemental selenium and MBH₄ (1 : 1) in triglyme (diglyme), under dehydrogenation. 1 reacts with an excess of B₂H₆ to give M[H₃B-μ₂-Se(B₂H₅)] 2 which is also formed in the reaction of THF · BH₃ with 1 . These reactions proceed under cleavage of the Se? Se bond and hydrogen evolution. [(C₆H₅)₄]Br reacts with Na · 2 to form [(C₆H₅)₄P] · 2 which crystallizes in the tetragonal space group I4 (Nr. 82). An X-ray structure determination failed because of disordering of the cation and anion. ¹¹B, ⁷⁷Se NMR shifts and ¹J(¹¹B¹H) coupling constants as well as IR- and Raman spectroscopic investigations convey further structural information. Structural data of 2 have been calculated by SCF methods. The anion of 2 may be viewed either as an adduct of Se with B₃H₈^?, or as a bridge substituted selena derivative of B₂H₆.     

Zu den Kristallstrukturen der Übergangsmetall(II)‐Dodekahydro‐closo‐Dodekaborat‐Hydrate Cu(H2O)5,5[B12H12]·2,5 H2O und Zn(H2O)6[B12H12]·6 H2O

On the Crystal Structures of the Transition‐Metal(II) Dodecahydro‐closo‐Dodecaborate Hydrates Cu(H₂O)_5.5[B₁₂H₁₂]·2.5 H₂O and Zn(H₂O)₆[B₁₂H₁₂]·6 H₂O By neutralization of an aqueous solution of the free acid (H₃O)₂[B₁₂H₁₂] with basic copper(II) carbonate or zinc carbonate, blue lath‐shaped single crystals of the octahydrate Cu[B₁₂H₁₂]·8 H₂O (≡ Cu(H₂O)_5.5[B₁₂H₁₂]·2.5 H₂O) and colourless face‐rich single crystals of the dodecahydrate Zn[B₁₂H₁₂]·12 H₂O (≡ Zn(H₂O)₆[B₁₂H₁₂]·6 H₂O) could be isolated after isothermic evaporation. Copper(II) dodecahydro‐closo‐dodecaborate octahydrate crystallizes at room temperature in the monoclinic system with the non‐centrosymmetric space group Pm (Cu(H₂O)_5.5[B₁₂H₁₂]·2.5 H₂O: a = 768.23(5), b = 1434.48(9), c = 777.31(5) pm, β = 90.894(6)°; Z = 2), whereas zinc dodecahydro‐closo‐dodecaborate dodecahydrate crystallizes cubic in the likewise non‐centrosymmetric space group F23 (Zn(H₂O)₆[B₁₂H₁₂]·6 H₂O: a = 1637.43(9) pm; Z = 8). The crystal structure of Cu(H₂O)_5.5[B₁₂H₁₂]·2.5 H₂O can be described as a monoclinic distortion variant of the CsCl‐type arrangement. As characteristic feature the formation of isolated [Cu₂(H₂O)₁₁]⁴⁺ units as a condensate of two corner‐linked Jahn‐Teller distorted [Cu(H₂O)₆]²⁺ octahedra via an oxygen atom of crystal water can be considered. Since “zeolitic” water of hydratation is also present, obviously both classical H–O^δ?···^+δH–O and non‐classical B–H^δ?···^+δH–O hydrogen bonds play a significant role for the stabilization of the structure. A direct coordinative influence of the quasi‐icosahedral [B₁₂H₁₂]^2? anions on the Cu²⁺ cations has not been determined. The zinc compound Zn(H₂O)₆[B₁₂H₁₂]·6 H₂O crystallizes in a NaTl‐type related structure. Two crystallographically different [Zn(H₂O)₆]²⁺ octahedra are present, which only differ in their relative orientation within the packing of the [B₁₂H₁₂]^2? anions. The stabilization of the crystal structure takes place mainly via H–O^δ?···^+δH–O hydrogen bonds, since again the hydrogen atoms of the [B₁₂H₁₂]^2? anions have no direct coordinative influence on the Zn²⁺ cations.     

Darstellung und Charakterisierung von Thiocyanatderivaten der Hydroboratanionen B10H102− und B12H122−

Preparation and Characterization of Thiocyanate Derivatives of the Hydroborate Anions B₁₀H₁₀^2? and B₁₂H₁₂^2? The reaction of B₁₀H₁₀^2? or B₁₂H₁₂^2? with (SCN)₂ in dichloromethane yields mixtures of thiocyanatohydroborates from which the pure isomers 1-and 2-(SCN)B₁₀H₉^2?, 1, 10-(SCN)₂B₁₀H₈^2?, and 1-(SCN)B₁₂H₁₁^2? are isolated by ion exchange chromatography on diethylaminoethyl cellulose. The structures are determined by ¹¹B and ¹¹B{¹H}NMR spectroscopy. There are characteristic chemical shifts due to apical and equatorial substituents, respectively. In B₁₀H₁₀^2? the substitution at apical positions is prefered. The IR and Raman spectra are similar to those of isosteric halogeno derivatives in the region of ν(BH) and of the borate cages. Because of the high frequencies of ν(CN): 2120–2140 cm^?1 S coordination of SCN^? is supposed.     

Synthese,Kristallstruktur und thermischer Abbau von Mg(H2O)6[B12H12] · 6 H2O

Synthesis, Crystal Structure, and Thermal Decomposition of Mg(H₂O)₆[B₁₂H₁₂] · 6 H₂O By reaction of an aqueous solution of the free acid (H₃O)₂[B₁₂H₁₂] with MgCO₃ and subsequent isothermic evaporation of the resulting solution to dryness, colourless, bead‐shaped single crystals of the dodecahydrate of magnesium dodecahydro closo‐dodecaborate Mg(H₂O)₆[B₁₂H₁₂] · 6 H₂O (cubic, F4₁32; a = 1643.21(9) pm, Z = 8) emerge. The crystal structure is best described as a NaTl‐type arrangement in which the centers of gravity of the quasi‐icosahedral [B₁₂H₁₂]^2— anions (d(B—B) = 178—180 pm, d(B—H) = 109 pm) occupy the positions of Tl^— while the Mg²⁺ cations occupy the Na⁺ positions. A direct coordinative influence of the [B₁₂H₁₂]^2— units at the Mg²⁺ cations is however not noticeable. The latter are octahedrally coordinated by six water molecules forming isolated hexaaqua complex cations [Mg(H₂O)₆]²⁺ (d(Mg—O) = 206 pm, 6×). In addition, six “zeolitic” water molecules are located in the crystal structure for the formation of a strong O—H^δ+···^δ—O‐hydrogen bridge‐bonding system. The evidence of weak B—H^δ—···^δ+H—O‐hydrogen bonds between water molecules and anionic [B₁₂H₁₂]^2— clusters is also considered. Investigations on the dodecahydrate Mg[B₁₂H₁₂] · 12 H₂O (≡ Mg(H₂O)₆[B₁₂H₁₂] · 6 H₂O) by DTA/TG measurements showed that its dehydration takes place in two steps within a temperature range of 71 and 76 °C as well as at 202 °C, respectively. Thermal treatment eventually leads to the anhydrous magnesium dodecahydro closo‐dodecaborate Mg[B₁₂H₁₂].     

On the Oxidation of the Three‐Dimensional Aromatics [B12X12]2− (X=F,Cl, Br,I)

The perhalogenated closo‐dodecaborate dianions [B₁₂X₁₂]^2? (X=H, F, Cl, Br, I) are three‐dimensional counterparts to the two‐dimensional aromatics C₆X₆ (X=H, F, Cl, Br, I). Whereas oxidation of the parent compounds [B₁₂H₁₂]^2? and benzene does not lead to isolable radicals, the perhalogenated analogues can be oxidized by chemical or electrochemical methods to give stable radicals. The chemical oxidation of the closo‐dodecaborate dianions [B₁₂X₁₂]^2? with the strong oxidizer AsF₅ in liquid sulfur dioxide (lSO₂) yielded the corresponding radical anions [B₁₂X₁₂] ^{? ?} (X=F, Cl, Br). The presence of radical ions was proven by EPR and UV/Vis spectroscopy and supported by quantum chemical calculations. Use of an excess amount of the oxidizing agent allowed the synthesis of the neutral perhalogenated hypercloso‐boranes B₁₂X₁₂ (X=Cl, Br). These compounds were characterized by single‐crystal X‐ray diffraction of dark blue B₁₂Cl₁₂ and [Na(SO₂)₆][B₁₂Br₁₂] ? B₁₂Br₁₂. Sublimation of the crude reaction products that contained B₁₂X₁₂ (X=Cl, Br) resulted in pure dark blue B₁₂Cl₁₂ or decomposition to red B₉Br₉, respectively. The energetics of the oxidation processes in the gas phase were calculated by DFT methods at the PBE0/def2‐TZVPP level of theory. They revealed the trend of increasing ionization potentials of the [B₁₂X₁₂]^2? dianions by going from fluorine to bromine as halogen substituent. The oxidation of all [B₁₂X₁₂]^2? dianions was also studied in the gas phase by mass spectrometry in an ion trap. The electrochemical oxidation of the closo‐dodecaborate dianions [B₁₂X₁₂]^2? (X=F, Cl, Br, I) by cyclic and Osteryoung square‐wave voltammetry in liquid sulfur dioxide or acetonitrile showed very good agreement with quantum chemical calculations in the gas phase. For [B₁₂X₁₂]^2? (X=F, Cl, Br) the first and second oxidation processes are detected. Whereas the first process is quasi‐reversible (with oxidation potentials in the range between +1.68 and +2.29 V (lSO₂, versus ferrocene/ferrocenium (Fc^0/+))), the second process is irreversible (with oxidation potentials ranging from +2.63 to +2.71 V (lSO₂, versus Fc^0/+)). [B₁₂I₁₂]^2? showed a complex oxidation behavior in cyclic voltammetry experiments, presumably owing to decomposition of the cluster anion under release of iodide, which also explains the failure to isolate the respective radical by chemical oxidation.     

Synthese und Kristallstruktur von Cadmium‐Dodekahydro‐closo‐Dodekaborat‐Hexahydrat,Cd(H2O)6[B12H12]

Synthesis and Crystal Structure of Cadmium Dodecahydro closo‐Dodecaborate Hexahydrate, Cd(H₂O)₆[B₁₂H₁₂] Through neutralization of the aqueous free acid (H₃O)₂[B₁₂H₁₂] with cadmium carbonate (CdCO₃) and after isothermic evaporation of the resulting solution, colourless lath‐shaped single crystals of Cd(H₂O)₆[B₁₂H₁₂] are obtained. Cadmium dodecahydro closo‐dodecaborate hexahydrate crystallizes at room temperature in the monoclinic system (space group: C2/m) with the lattice constants a = 1413.42(9), b = 1439.57(9), c = 749.21(5) pm and β = 97.232(4)° (Z = 4). The crystal structure of Cd(H₂O)₆[B₁₂H₁₂] can be regarded as a monoclinic distortion variant of the CsCl‐type structure. Two crystallographically different [Cd(H₂O)₆]²⁺ octahedra (d(Cd–O) = 227–230 pm) are present which only differ in their relative orientation. The intramolecular bond lengths for the quasi‐icosahedral [B₁₂H₁₂]^2? cluster anions range in the intervals usually found for dodecahydro closo‐dodecaborates (d(B–B) = 177–179 pm, d(B–H) = 103–116 pm). The hydrogen atoms of the [B₁₂H₁₂]^2? clusters have no direct coordinative influence on the Cd²⁺ cations. Due to the fact that no “zeolitic” crystal water molecules are present, a stabilization of the lattice takes place mainly via the B–H^δ?···^+δH–O hydrogen bonds.     

Strukturelle Untersuchungen an Cs2[B12H12]

Structural Investigations on Cs₂[B₁₂H₁₂] The crystal structure of Cs₂[B₁₂H₁₂] has been determined from X‐ray single‐crystal data collected at room temperature. Dicesium dodecahydro‐closo‐dodecaborate crystallizes as colourless, face‐rich crystals (cubic, Fm 3; a = 1128.12(7) pm; Z = 4). Its synthesis is based on the reaction of Na[BH₄] with BF₃(O(C₂H₅)₂) via the decomposition of Na[B₃H₈] in boiling diglyme, followed by subsequent separations, precipitations (with aqueous CsOH solution) and recrystallizations. The crystal structure is best described as anti‐CaF₂‐type arrangement with the Cs⁺ cations in all tetrahedral interstices of the cubic closest‐packed host lattice of the icosahedral [B₁₂H₁₂]^2–‐cluster dianions. The intramolecular bond lengths are in the range usually found in closo‐hydroborates: 178 pm for the B–B and 112 pm for the B–H distance. Twelve hydrogen atoms belonging to four [B₁₂H₁₂]^2– icosahedra provide an almost perfect cuboctahedral coordination sphere to the Cs⁺ cations, and their distance of 313 pm (12 ×) attests for the salt‐like character of Cs₂[B₁₂H₁₂] according to {(Cs⁺)₂([B₁₂H₁₂]^2–)}. The ¹¹B{¹H}‐NMR data in aqueous (D₂O) solution are δ = –12,70 ppm (¹J_B–H = 125 Hz), and δ = –15,7 ppm (linewidth: δν_1/2 = 295 Hz) for the solid state ¹¹B‐MAS‐NMR.     

Reaktionen von [B12H12–n(OH)n]2–, n = 1, 2 mit Säuredichloriden und Kristallstruktur von Cs2[1,2-B12H10(ox)] · CH3OH

Reactions of [B₁₂H_12–n(OH)_n]^2–, n = 1, 2 with Acid Dichlorides and Crystal Structure of Cs₂[1,2-B₁₂H₁₀(ox)] · CH₃OH By treatment of [B₁₂H₁₁(OH)]^2– with organic and inorganic acid dichlorides in acetonitrile the bridged dicluster compounds [B₁₂H₁₁(ox)B₁₂H₁₁)]^4– ( 1 ), [B₁₂H₁₁(p-OOCC₆H₄COO)B₁₂H₁₁]^4– ( 2 ), [B₁₂H₁₁(m-OOCC₆H₄COO)B₁₂H₁₁]^4– ( 3 ), [B₁₂H₁₁(SO₃)B₁₂H₁₁]^4– ( 4 ), [B₁₂H₁₁(SO₄)B₁₂H₁₁]^4– ( 5 ) are obtained in good yields. The dihydroxododecaborates [1,2-B₁₂H₁₀(OH)₂]^2– and [1,7-B₁₂H₁₀(OH)₂]^2– afford clusters with an anellated ring: [1,2-B₁₂H₁₀(ox)]^2– ( 6 ), [1,2-B₁₂H₁₀(SO₄)]^2– ( 7 ) and [1,7-B₁₂H₁₀(OOC(CH₂)₈COO)]^2– ( 8 ). Isomerically pure [1,7-B₁₂H₁₀(OH)₂]^2– ( 9 ) is formed by reaction of (H₃O)₂[B₁₂H₁₂] with ethylene glycol. All new compounds are characterized by vibrational, ¹¹B, ¹³C and ¹H NMR spectra. The crystal structure of Cs₂[1,2-B₁₂H₁₀(ox)] · CH₃OH (monoclinic, space group P 2₁/c, a = 9.616(2), b = 10.817(1), c = 15.875(6) Å, β = 95.84(8)°, Z = 4) reveals a distortion of the B₁₂ icosahedron caused by the anellated six-membered heteroring.     

Dodecahydro‐closo‐undecaborate [B11H12]–

DFT‐calculations of the geometries of the closo‐anion [B₁₁H₁₁]^2– in its ground state and in the transition state of its skeletal rearrangement and of the protonated species [B₁₁H₁₂]^– in its ground state were performed at the B3LYP/6‐31++G(d,p) level. The corresponding NMR shifts were computed on the basis of the optimized geometry by the GIAO method at the same level. Calculated and observed NMR data are in good agreement and thus prove the structure of [B₁₁H₁₂]^–, previously deduced from 2 D‐NMR spectra. The addition of water, ethanol, and pyridine to [B₁₁H₁₂]^– at low temperature gave the nido‐species [B₁₁H₁₃(OH)]^–, [B₁₁H₁₃(OEt)]^–, and [B₁₁H₁₂(py)]^–, respectively. The structures of these anions were investigated by NMR methods and the last two of them by crystal structure analyses of appropriate salts. The course of the addition reactions can be rationalized on the basis of the structurally characterized reaction components.     

The [U2F12]2− Anion of Sr[U2F12]

The D_2h‐symmetric dinuclear complex anion [U₂F₁₂]^2? of pastel green Sr[U₂F₁₂] shows a hitherto unknown structural feature: The coordination polyhedra around the U atoms are edge‐linked monocapped trigonal prisms, the U^V atoms are therefore seven‐coordinated. This leads to a U–U distance of 3.8913(6) Å. A weak U^V–U^V interaction is observed for the dinuclear [U₂F₁₂]^2? complex and described by the antiferromagnetic exchange J_exp of circa ?29.9 cm^?1. The crystalline compound can be easily prepared from SrF₂ and β‐UF₅ in anhydrous hydrogen fluoride (aHF) at room temperature. It was studied by means of single crystal X‐ray diffraction, IR, Raman and UV/VIS spectroscopy, magnetic measurements, and by molecular as well as by solid‐state quantum chemical calculations.     

Darstellung und Kristallstrukturen von Dipyridiniomethan-Monohalogenohydro-closo-Dodecaboraten(2−), [(C5H5N)2CH2][B12H11X]; X = Cl,Br, I

Preparation and Crystal Structures of Dipyridiniomethane Monohalogenohydro-closo-Dodecaborates(2?), [(C₅H₅N)₂CH₂][B₁₂H₁₁X]; X = Cl, Br, I [B₁₂H₁₂]^2? reacts with dihalogenomethanes CH₂X₂ in presence of trifluoro acetic acid, yielding the monohalogenododecaborates [B₁₂H₁₁X]^2? (X = Cl, Br, I), which are separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from the starting compound and higher halogenated products. The X-ray structure determinations of [(C₅H₅N)₂CH₂][B₁₂H₁₁Cl] · 2(CH₃)₂SO (orthorhombic, space group Pnma, a = 17.351(6), b = 16.034(5), c = 9.659(2) Å, Z = 4) and of the isotypic bromo and iodo compounds [(C₅H₅N)₂CH₂][B₁₂H₁₁X] (monoclinic, space group P2₁/n, Z = 4; for X = Br: a = 7.339(2), b = 15.275(3), c = 16.761(4) Å, β = 96.80(2)°; for X = I: a = 7.4436(8), b = 15.3510(8), c = 16.9213(16) Å, ß = 97.326(7)°) exhibit crystal lattices build up by columns of substituted boron clusters and angular dications [(C₅H₅N)₂CH₂]²⁺ orientated along the shortest axis which are assembled to alternating layers.     

Dodecahydro‐nido‐undecaborate [B11H12]3–

The deprotonation of the nido‐anion [B₁₁H₁₄]^– by two equivalents of LitBu yields the anion [B₁₁H₁₂]^3–. Three observed ¹¹B NMR shifts of this anion in the ratio 1 : 5 : 5 are in agreement with shifts calculated by the GIAO method on the basis of the ab initio computed geometry. The deprotonation can be reversed, giving back [B₁₁H₁₄]^– via [B₁₁H₁₃]^2–. The thermolysis of [Li(thp)_x]₃[B₁₁H₁₂] in thp at 80 °C leads to the closo‐borate [Li(thp)₃]₂[B₁₁H₁₁] under elimination of LiH. Anhydrous air transforms [B₁₁H₁₂]^3– into the known oxa‐nido‐dodecaborate [OB₁₁H₁₂]^–. The rhoda‐closo‐dodecaborate [L₂RhB₁₁H₁₁]^3– is formed from [B₁₁H₁₂]^3– and RhL₃Cl (L = PPh₃).     

Chemische und cyclovoltammetrische Untersuchung der Redoxreaktionen der Decahalogendecaborate closo‐[B10X10]2– und hypercloso‐[B10X10]· – (X = Cl,Br). Kristallstrukturanalyse von Cs2[B10Br10] · 2 H2O

Chemical and Cyclovoltammetric Investigation of the Redoxreactions of the Decahalodecaborates closo ‐[B₁₀X₁₀]^2– and hypercloso ‐[B₁₀X₁₀]^{· –} (X = Cl, Br)¹⁾. Crystal Structure Analysis of Cs₂[B₁₀Br₁₀] · 2 H₂O The oxidation of the decachloro‐closo‐decaborates(2–) Cs₂[B₁₀Cl₁₀] or [Me₄N]₂[B₁₀Cl₁₀] with Tl(CF₃COO)₃ leads to the corresponding radical monoanion hypercloso‐[B₁₀Cl₁₀] ^{· –}, which was characterized by ESR and UV/Vis spectroscopy. [B₁₀Cl₁₀] ^{· –} does not dimerize like [B₁₀H₁₀] ^{· –} but it is reduced by acetonitrile to the dianion [B₁₀Cl₁₀]^2–. Cs₂[B₁₀Cl₁₀] reacts with stronger oxidation agents like CoF₃ (in dichloromethane) or XeF₂ (in perfluorhexane), respectively, to yield B₉Cl₉ and, in traces, B₈Cl₈. In opposite to this, the decabromoderivative Cs₂[B₁₀Br₁₀] does not show any reaction with Tl(CF₃COO)₃ in acetonitrile or with CoF₃ in CH₂Cl₂. The oxidation of the dianions [B₁₀X₁₀]^2– (X = Cl, Br) was studied by electroanalytical methods (cyclic voltammetry, chronoamperometry, chronocoulometry). Formal potentials were determined for the two steps of the reaction, which do not seem to be affected by structural rearrangements. The crystal structure of Cs₂[B₁₀Br₁₀] · 2 H₂O was analyzed by single‐crystal X‐ray diffraction. Cs₂[B₁₀Br₁₀] · 2 H₂O crystallizes monoclinic (space group I2/a, (no. 15), Z = 8, a = 1361.54(9) pm, b = 1215.89(5) pm, c = 3108.4(2) pm, α = 90°, β = 97.916(8)°, γ = 90°). The closo‐cluster B₁₀Br₁₀^2– has a bicapped square antiprismatic structure with idealized D_4d symmetry.     

Monomere und dimere Chrom(III)-Phthalocyanine: Synthese und Eigenschaften von Hydroxopyridinophthalocyaninatochrom(III) und μ-Oxodi(pyridinophthalocyaninatochrom(III))

Monomeric and Dimeric Chromium(III) Phthalocyanines: Synthesis and Properties of Hydroxopyridinophthalocyaninatochromium(III) and μ-Oxodi(pyridinophthalocyaninatochromium(III)) Heating of ?[Cr(OH)Pc^2?]”? in pyridine (Py) gives the paramagnetic (T = 273 K) complexes [Cr(OH)(Py)Pc^2?] (μ_Cr = 3.84 μ_B) and [(Cr(Py)Pc^2?)₂O] (μ_Cr = 1.24 μ_B) by consecutive substitution and condensation reactions. The UV-VIS spectra are characterized by the typical B, Q, and N regions of the Pc^2? ligand being shifted hypsochromically for the dimer with respect to the monomer due to excitonic coupling (1.5 kK). Regions of weak absorbance between 8 and 13 resp. 19 kK are assigned to trip-quartet transitions for both complexes. A weak band at 870 cm^?1 in the FIR/MIR spectra is assigned to v_as(Cr? O? Cr). In the resonance Raman(RR) spectra v(Cr? O) at 514 cm^?1 resp. v_s(Cr? O? Cr) at 426 cm^?1 is selectively enhanced. Further strong RR-lines of the μ-Oxo dimer at 110 and 631 cm^?1 are assigned to a (Py? Cr? O)- resp. internal pyridine deformation of a_1g symmetry. An assignment as 2v_as(Cr? O? Cr) is proposed for the remarkable RR line at 1740 cm^?1.     

Darstellung und Kristallstruktur von [P(C6H5)4][2,9-{N,N′-(2-NH?(C5H4N))}B10H8]

Synthesis and Crystal Structure of [P(C₆H₅)₄][2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈] [N(C₄H₉)₄]₂[B₁₀H₁₀] reacts with 2-aminopyridine forming a product mixture from which [2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈]^? can be isolated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose. The crystal structure of [P(C₆H₅)₄][2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈] (triclinic, space group P1 , a = 10.1103(9), b = 11.5665(9), c = 14.877(2) Å, α = 102.600(8), β = 107.567(8) und γ = 96.487(7)°, Z = 2) reveals the bonding of 2-NH₂-(C₅H₄N) via both N atoms to vicinal B atoms of the two square planes of the B₁₀ cluster (B2? N1 = 1,541(7) und B9? N2 = 1.505(7) Å) forming a five-membered ring.