The closo-Cluster Triad: B9X9, [B9X9]· –, and [B9X9]2– with Tricapped Trigonal Prisms (X = Cl,Br, I). Syntheses,Crystal and Electronic Structures

Halogenation of nido-B₁₀H₁₄ with C₂H₂Cl₄, C₂Cl₆, Br₂, or I₂, produces by cluster degradation the (2 n)-closo-clusters B₉X₉ (X = Cl, Br, I). The synthesis of salts of the perhalogenated radical anions of the type (2 n + 1)-closo-[B₉X₉]^{· –} and of the corresponding dianions (2 n + 2)-closo-[B₉X₉]^2– from neutral B₉X₉ is described [n is the number of cluster atoms; (2 n), (2 n + 1), and (2 n + 2) is the number of cluster electrons]. Molecular and crystal structures of B₉Cl₉, B₉Br₉, [(C₆H₅)₄P][B₉Br₉] · CH₂Cl₂, and [(C₄H₉)₄N]₂[B₉Br₉] · CH₂Cl₂ have been determined via X-ray diffraction. All three oxidation states of the cluster retain the tricapped trigonal prism. The reduction of the clusters B₉X₉ was shown by cyclic voltammetry in CH₂Cl₂ to proceed via two successive one-electron reversible steps, separated by at least 0.4 V. The paramagnetic radical anions [B₉X₉]^{· –} (X = Cl, Br) were further characterized by magnetic susceptibility measurements of [Cp₂Fe][B₉X₉] and [Cp₂Co][B₉X₉], respectively. The EPR spectra of [B₉X₉]^{· –} (X = Cl, Br, I) in glassy frozen CH₂Cl₂ solutions showed increasing g anisotropy for the heavier halogen derivatives, illustrating significant halogen participation at the singly occupied MO. The ¹¹B NMR spectra of CD₂Cl₂ solutions of the neutral clusters B₉X₉ exhibit only one sharp resonance, indicating that the boron atoms are highly fluxional in solution. In contrast, two different boron resonances as expected for a rigid tricapped trigonal prism are clearly observed for the [B₉X₉]^2– dianions in solutions and for solid B₉Br₉ in the ¹¹B MAS NMR spectra. Temperature dependent ¹¹B MAS NMR experiments on B₉Br₉ and [B₉Br₉]^2– in the solid state show a reversible coalescence of the two resonances at higher temperature. ¹¹B MAS NMR spectra and DTA measurements of [B₉Br₉]^2– showed a phase transition.     

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.     

Die Kristallstrukturen der Dicaesium-Dodekahalogeno-closo-Dodekaborate Cs2[B12X12] (X = Cl,Br, I) und ihrer Hydrate

The Crystal Structures of the Dicesium Dodecahalogeno-closo-Dodecaborates Cs₂[B₁₂X₁₂] (X = Cl, Br, I) and their Hydrates The perhalogenated derivatives Cs₂[B₁₂X₁₂] (X = Cl - I) have been synthesized by reaction of Cs₂[B₁₂H₁₂] with the respective elemental halogens (Cl₂, Br₂ and I₂). Upon recrystallization from aqueous solution colourless, face-rich single crystals of the dihydrates (Cs₂[B₁₂X₁₂] · 2 H₂O) are obtained first which can be dehydrated topotactically via the monohydrates (Cs₂[B₁₂X₁₂] · H₂O) leaving to the solvent-free compounds (Cs₂[B₁₂X₁₂]) behind without loss of their crystallinity. The ionic cesium salts were characterized by single crystal X-ray diffraction. All three halogenoborates are isostructural and they crystallize at room temperature in the trigonal space group (Cs₂[B₁₂Cl₁₂]: a = 959.67(3) pm, c = 4564.2(2) pm; Cs₂[B₁₂Br₁₂]: a = 997.92(3) pm, c = 4766.4(3) pm; Cs₂[B₁₂I₁₂]: a = 1047.05(4) pm, c = 5018.3(3) pm; Z = 6). The crystal structures consist of a cubic closest packed host lattice formed by two crystallographically inequivalent quasi-icosahedral [B₁₂X₁₂]^2- anions (Cs₂[B₁₂Cl₁₂]: d(B-B) = 178 - 179 pm, d(B-Cl) = 179 - 180 pm; Cs₂[B₁₂Br₁₂]: d(B-B) = 176 - 180 pm, d(B-Br) = 195 - 197 pm; Cs₂[B₁₂I₁₂]: d(B-B) = 177 - 182 pm, d(B-I) = 214 - 217 pm). By ordered occupation of half of the tetrahedral and formally all octahedral interstices in every intermediate layer with Cs⁺ cations, a structure emerges where (Cs1)⁺ is trigonally non-planar coordinated by three (CN = 9) and (Cs2)⁺ tetrahedrally coordinated by four (CN = 12) [B₁₂X₁₂]^2- anions. Thereby triangular faces of halogen atoms of the icosahedral clusters are coordinatively effective in both cases. In their mono- and dihydrates the incomplete coordination sphere of (Cs1)⁺ is completed by one and two water molecules, respectively. The thermal decomposition of the dicesium dodecahalogeno-closo-dodecaborate hydrates and their dehydration products was investigated using DTA/TG methods in a temperature range between room temperature and 1200 °C. Additionally the compounds were also characterized by ¹¹B-NMR spectroscopy in aqueous solution.     

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.     

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).     

Relevance of π-Backbonding for the Reactivity of Electrophilic Anions [B12X11]− (X=F,Cl, Br,I, CN)

Electrophilic anions of type [B₁₂X₁₁]⁻ posses a vacant positive boron binding site within the anion. In a comparatitve experimental and theoretical study, the reactivity of [B₁₂X₁₁]⁻ with X=F, Cl, Br, I, CN is characterized towards different nucleophiles: (i) noble gases (NGs) as σ-donors and (ii) CO/N₂ as σ-donor-π-acceptors. Temperature-dependent formation of [B₁₂X₁₁NG]⁻ indicates the enthalpy order (X=CN)>(X=Cl)≈(X=Br)>(X=I)≈(X=F) almost independent of the NG in good agreement with calculated trends. The observed order is explained by an interplay of the electron deficiency of the vacant boron site in [B₁₂X₁₁]⁻ and steric effects. The binding of CO and N₂ to [B₁₂X₁₁]⁻ is significantly stronger. The B3LYP 0 K attachment enthapies follow the order (X=F)>(X=CN)>(X=Cl)>(X=Br)>(X=I), in contrast to the NG series. The bonding motifs of [B₁₂X₁₁CO]⁻ and [B₁₂X₁₁N₂]⁻ were characterized using cryogenic ion trap vibrational spectroscopy by focusing on the CO and N₂ stretching frequencies and , respectively. Observed shifts of and are explained by an interplay between electrostatic effects (blue shift), due to the positive partial charge, and by π-backdonation (red shift). Energy decomposition analysis and analysis of natural orbitals for chemical valence support all conclusions based on the experimental results. This establishes a rational understanding of [B₁₂X₁₁]⁻ reactivety dependent on the substituent X and provides first systematic data on π-backdonation from delocalized σ-electron systems of closo-borate anions.     

Synthesis and Structure of Tetrameric Germa‐closo‐dodecaborate Silver Halides

The reaction of germa‐closo‐dodecaborate with oneequivalent of silver halide AgX (X = Cl, Br) leads to the tetrameric1:1 adducts [Et₃MeN]₈[{AgCl(GeB₁₁H₁₁)}₄] ( 1 ) and [Et₃MeN]₈[{AgBr(GeB₁₁H₁₁)}₄] ( 2 ). A cubane‐like structure was determined in the solid state by single‐crystal X‐ray diffraction. The compounds were characterized by crystal structure analysis, ¹¹B NMR spectroscopy and elemental analysis.     

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.     

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.     

HB9X9˙ and H2B9X9 (X = Cl,Br, I): Neutral closo-Nonaboranes in the Novel Series BnHn+1, and BnHn+2 – Syntheses,Ab Initio Calculations,and Electronic Structures

Chemical reduction of B₉X₉ (X = Cl, Br, I) with gaseous HI proceeds stepwise to give the neutral paramagnetic clusters HB₉X₉ ^· , and the corresponding diamagnetic clusters H₂B₉X₉. Together they comprise the first neutral derivatives in the series B_nH_n+1 and B_nH_n+2 with n = 9. The EPR spectra of the paramagnetic HB₉X₉ ^· (X = Cl, Br, I) in glassy frozen CH₂Cl₂ solutions showed increasing g anisotropy for the heavier halogen derivatives, illustrating significant halogen participation at the singly occupied MO due to the larger spin-orbit coupling contributions. Temperature dependent ¹H NMR spectra of H₂B₉X₉ (in CD₃CN, X = Cl, Br) indicate the presence of H₂B₉X₉, [HB₉X₉]^–, and [CD₃CNH]⁺ with H₂B₉X₉ acting as a Brønsted acid. The corresponding ¹¹B NMR spectra (in CD₃CN) show the presence of the dianions [B₉X₉]^2– as a result of the protonation of CD₃CN. The ¹¹B resonances of the species H₂B₉X₉ and [HB₉X₉]^– are obscured by superimposition of the two resonance lines of the dianions [B₉X₉]^2–. Temperature dependent ¹¹B{¹H} MAS-NMR spectra of H₂B₉Br₉ show coalescence at 410 K and hence dynamic behaviour of the neutral B₉-cluster in the solid. Cyclic voltammetry experiments of H₂B₉Br₉ in CH₃CN solvent) are compatible with the redox sequence [B₉Br₉]^2––[B₉Br₉] ^{· –}–B₉Br₉. Quantum chemical calculations with the electron localization function (ELF) are described.     

Darstellung und Schwingungsspektren von trans-[Pt(acac)2X2] (X  Cl,Br, I,SCN, SeCN,N3)

Preparation and Vibrational Spectra of trans-[Pt(acac)₂X₂] (X ? Cl, Br, I, SCN, SeCN, N₃) By electrolytical oxidation of [Pt(acac)₂] in presence of chloride or bromide, dissolved in dichlormethane, trans-[Pt(acac)₂X₂], X ? Cl, Br, are formed. On treatment of trans-[Pt(acac)₂I₂] with silver pseudohalides trans-[Pt(acac)₂X₂], X ? SCN, SeCN, N₃, are obtained. Beside the nearly persistent bands of coordinated acetylacetonate in the Raman spectra the intensive and sharp symmetric, in the IR spectra the corresponding antisymmetric stretching vibration of the X? Pt? X axis is observed. The observance of the rule of mutual exclusion proves the complexes to belong to point group D_2h. From the resonance Raman spectrum of trans-[Pt(acac)₂I₂] for v_s (Pt? I), A_g, the harmonic frequency ω₁ = 142.45 cm^?1 and the inharmonicity constant x₁₁ = 0.48 cm^?1 is calculated. In the Raman spectrum of trans-[Pt(acac)₂Cl₂] v_s (Pt? Cl) is splitted by the isotops ³⁵Cl/³⁷Cl into the triplet 340, 335, 330 cm^?1 giving the force constant f_PtCl = 2.01 N/cm.     

Die Umwandlung [W6X8]X4 [W6X12]X6 (X = Cl,Br)

Transformation of [W₆X₈]X₄ + 3 X₂ = [W₆X₁₂]X₆ (X = Cl, Br) The transformation of [W₆X₈]X₄ + 3 X₂ = [W₆X₁₂]X₆ (X = Cl, Br) has been investigated by changing the relation Cl₂/Br₂ and the temperature. In this way the compounds [W₆Br_12?nCl_n]Cl_6?mBr_m are isolated. All of the products are isotypic with W₆Cl₁₈ and W₆Br₁₈. Most often n equals 6, however compounds with other relations of Cl/Br are also observed (e. g. n = 4.8) The 6 ligands standing outside of the brackets are replaced by Cl or Br. The substitution of [W₆Br₆Cl₆]Cl₆ by means of bromine leads to the cluster [W₆Br₁₂]X₆. The backward transformation of the cluster compound [W₆Br₁₂]Br₆ happens by decomposition on the thermobalance, e. g. according to Gl. (1) (See Inhaltsübersicht). By analogy [W₆Br₁₂]Cl₆ is decomposed to [W₆Br₈]Cl₂Br₂, which by treatment with conc. HCl is transformed into [W₆Br₈]Cl₄ · 2 H₂O.     

Untersuchungen zur Kristallstruktur von Lithium‐dodecahydro‐closo‐dodecaborat aus wäßriger Lösung: Li2(H2O)7[B12H12]

Investigations on the Crystal Structure of Lithium Dodecahydro‐closo‐dodecaborate from Aqueous Solution: Li₂(H₂O)₇[B₁₂H₁₂] By neutralization of an aqueous solution of the acid (H₃O)₂[B₁₂H₁₂] with lithium hydroxide (LiOH) and subsequent isothermic evaporation of the resulting solution to dryness, it was possible to obtain the heptahydrate of lithium dodecahydro‐closo‐dodecaborate Li₂[B₁₂H₁₂] · 7 H₂O (≡ Li₂(H₂O)₇[B₁₂H₁₂]). Its structure has been determined from X‐ray single crystal data at room temperature. The compound crystallizes as colourless, lath‐shaped, deliquescent crystals in the orthorhombic space group Cmcm with the lattice constants a = 1215.18(7), b = 934.31(5), c = 1444.03(9) pm and four formula units in the unit cell. The crystal structure of Li₂(H₂O)₇[B₁₂H₁₂] can not be described as a simple AB₂‐structure type. Instead it forms a layer‐like structure analogous to the well‐known barium compound Ba(H₂O)₆[B₁₂H₁₂]. Characteristic feature is the formation of isolated cation pairs [Li₂(H₂O)₇]²⁺ in which the water molecules form two [Li(H₂O)₄]⁺ tetrahedra with eclipsed conformation, linked to a dimer via a common corner. The bridging oxygen atom (∢(Li‐ O ‐Li) = 112°) thereby formally substitutes Ba²⁺ in Ba(H₂O)₆[B₁₂H₁₂] according to (H₂ O )Li₂(H₂O)₆[B₁₂H₁₂]. A direct coordinative influence of the [B₁₂H₁₂]^2— cluster anions to the Li⁺ cations is not noticeable, however. The positions of the hydrogen atoms of both the water molecules and the [B₁₂H₁₂]^2— units have all been localized. In addition, the formation of B‐H^δ—···^δ+H‐O‐hydrogen bonds between the water molecules and the hydrogen atoms from the anionic [B₁₂H₁₂]^2— clusters is considered and their range and strength is discussed. The dehydratation of the heptahydrate has been investigated by DTA‐TG measurements and shown to take place in two steps at 56 and 151 °C, respectively. Thermal treatment leads to the anhydrous lithium dodecahydro‐closo‐dodecaborate Li₂[B₁₂H₁₂], eventually.     

Die Elektronen-Lokalisierungs-Funktion in closo-Bor-Clustern

The Electron Localization Function in closo Boron Clusters The structure and the electron density in the closo boron clusters B₄X₄ (X = H, Cl, Br, I), B₆X₆^2? (X = H, Cl, Br, I) and B₁₂H₁₂^2? were determined by pseudopotential Hartree-Fock calculations. The Electron Localization Function (ELF) was used to interpret the bonding characteristics. The regions of high ELF values in all cases have the form of the dual polyhedron of the boron cage. They show perfectly the 3 center 2 electron bonds. The comparison between Hartree-Fock and Extended Hückel calculations point out that semiempirical calculations can also be a good basis for ELF interpretations.     

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.     

Synthesis,Electronic Properties and Reactivity of [B12X11(NO2)]2− (X=F–I) Dianions

Nitro-functionalized undecahalogenated closo-dodecaborates [B₁₂X₁₁(NO₂)]²⁻ were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X-diffraction, mass spectrometry, and gas-phase ion vibrational spectroscopy. The NO₂ substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B₁₂X₁₂]²⁻ (X=F–I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum-chemical calculations. The stabilizing effect decreases from X=F to X=I. Thermogravimetric measurements of the salts indicate the loss of the nitric oxide radical (NO^.). The homolytic NO^. elimination from the dianion under very soft collisional excitation in gas-phase ion experiments results in the formation of the radical [B₁₂X₁₁O]^2−.. Theoretical investigations suggest that the loss of NO^. proceeds via the rearrangement product [B₁₂X₁₁(ONO)]²⁻. The O-bonded nitrosooxy structure is thermodynamically more stable than the N-bonded nitro structure and its formation by radical recombination of [B₁₂X₁₁O]^2−. and NO^. is demonstrated.     

Darstellung von trans-[Pt(ox)2X2]2− (X = Cl,Br, I,SCN, OH) durch oxydative Addition an [Pt(ox)2]2− in organischen Solventien

Preparation of trans-[Pt(ox)₂X₂]^2? (X = Cl, Br, I, SCN, OH) by Oxidative Addition to [Pt(ox)₂]^2? in Organic Solvents After extraction of [Pt(ox)₂]^2? with long-chain alkyl-ammonium ions into organic solvents the new Pt^IV complexes trans-[Pt(ox)₂X₂]^2?, X = Cl, Br, I, SCN, OH, are formed directly by oxidative addition. In nonpolar solvents the bulky organic cations prevent the formation of compounds with columnar structure which by partial oxidation in aqueous solution are formed immediately. The IR and Ra spectra of the stable anhydrous (TBA) salts are assigned according to point group D_2h. A characteristical dependence of the C?O, C? O, and Pt? O stretching modes in response to the oxidation state of the central ion is observed. There is vibrational fine structure in the absorption spectrum of [Pt(ox)₂]^2? measured at 10 K with long progressions by coupling of d—d transitions with v_s(Pt? O) and v_s(C?O). The characteristical feature in the UV/VIS spectra of the Pt^IV complexes is caused by intensive π(O, X) ← e_g(Pt) CT transitions.     

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.     

ChemInform Abstract: Protic Anions [H(B12X12)]‐ (X: F,Cl, Br,I) that Act as Broensted Acids in the Gas Phase.

The protic anions [H(B₁₂X₁₂)]^‐ (X: F, Cl, Br, I) are investigated with respect to their ability to protonate neutral molecules in the gas phase by using a combination of tandem mass spectrometry and quantum‐chemical calculations.     

Nitrile Cluster Compounds [(M6X12)X2(RCN)4] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu)

Three new series of mixed-ligand clusters of the [(M₆X₁₂)X₂(RCN)₄] (M=Nb, Ta; X=Cl, Br; R=Et, n-Pr, n-Bu) composition have been prepared. It is supposed that four nitrile molecules and two halogen atoms are coordinated to the terminal octahedral coordination sites of the [M₆X₁₂]²⁺ unit.