Efficient direct fluorination of the B12H11(NH3)− anion in acetonitrile and comparison of the structures of Na(H2O)4(B12F11(NH3)), Na(H3O)(H2O)3(B12F12), and Na2(H2O)4(B12F12)

Activation of Small Molecules by Modified Dodecaborate Anions

Two of the basic requirements of a good catalyst are that molecules be bound to it with energies intermediate between physisorption and chemisorption and be simultaneously activated in the process. Using density functional theory, we have studied the interaction of small molecules such as H2, O2, N2, CO2, CO, and NH3 with modified dodecaborate anion [B12H12]2-, namely, [B12X11]- and [B12X11]2- (X = H, F, CN). Calculations of the structure, stability, and electronic properties of these species interacting with the above molecules show that they meet the above requirements. In addition, [B12X11]2- (X = F, CN) species are not only more stable than [B12X11]- species but also bind to O2 more strongly than their monoanion counterparts.

Synthesis of Perchlorinated Sulfonium Derivatives of closo-Decaborate Anion [2-B10Cl9SR2]- (R = i-C3H7, n-C3H7, n-C4H9, n-C8H17, n-C12H25, n-C18H37, CH2Ph, and cyclo-S(CH2)4)

A method for obtaining perchlorinated di-S,S-substituted derivatives of the closo-decaborate anion with various alkyl groups has been developed: [B₁₀Cl₉SR₂]^- (R= i-C₃H₇, n-C₃H₇, n-C₄H₉, n-C₈H₁₇, n-C₁₂H₂₅, n-C₁₈H₃₇, CH₂Ph, and cyclo-S(CH₂)₄). The method is based on the preparation of the sulfonium-substituted anion [B₁₀H₉SR₂]^- by alkylation of the anion [B₁₀H₉SH]^2- with bromoalkanes (i-C₃H₇Br, n-C₃H₇Br, n-C₄H₉Br, n-C₈H₁₇Br, n-C₁₂H₂₅Br, n-C₁₈H₃₇Br, PhCH₂Br, and BrCH₂(CH₂)₂CH₂Br) followed by the cluster chlorination with sulfuryl chloride SO₂Cl₂ in acetonitrile. The process proceeds until the hydrogen atoms in the boron cluster are completely replaced with chlorine and completes within 60 h. It has been found that the melting point of salts ((C₄H₉)₄N)[B₁₀Cl₉SR₂] (R= i-C₃H₇, n-C₃H₇, n-C₄H₉, n-C₈H₁₇, n-C₁₂H₂₅, and n-C₁₈H₃₇) strongly depends on the length of the hydrocarbon chain of the substituent R.

Synthesis, Electronic Properties and Reactivity of [B12 X11 (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.

[Se(CH2C(O)CH3)3][B12F11NH3]: The first selenium cation with three β-ketone substituents

The cation [Se(CH₂C(O)CH₃)₃]⁺ represents the first example for a cationic selenium compound with three ketone functional groups located in the β-position with respect to the selenium atom. The cation possesses almost trigonal–pyramidal C₃ symmetry and forms hydrogen bonds to the ammonio group of the anion

The reaction of [Se₈][B₁₂F₁₁NH₃]₂ with acetone and subsequent crystallization from acetone/diethyl ether yielded the selenium cation [Se(CH₂C(O)CH₃)₃]⁺ as a by-product, which is stabilized by the weakly coordinating undeca­fluorinated anion [B₁₂F₁₁NH₃]⁻. While attempting to crystallize pure [Se₈][B₁₂F₁₁NH₃]₂, the structure of the isolated product, namely, tris­(2-oxoprop­yl)selenium 1-ammonio­undeca­fluoro­dodeca­borate, was surprising. The cation [Se(CH₂C(O)CH₃)₃]⁺ represents the first example for a cationic selenium compound with three ketone functional groups located in the β-position with respect to the selenium atom. The cation possesses almost trigonal–pyramidal C₃ symmetry and forms hydrogen bonds to the ammonio group of the anion.

Na+[Me3NB12Cl11]-·SO2: a rare example of a sodium-SO2 complex

In the title compound, the SO₂ mol­ecule is η¹-O-coordinated to the Na⁺ cation. The Na⁺ cation has a coordination number of eight in a distorted twofold capped trigonal prism and makes contacts to three individual boron cluster anions resulting in an overall three-dimensional network.

In the title compound, Na⁺[Me₃NB₁₂Cl₁₁]⁻·SO₂ [systematic name: sodium 1-(trimethylammonio)­undeca­chloro-closo-dodeca­borate sulfur dioxide], the SO₂ mol­ecule is η¹-O-coordinated to the Na⁺ cation. Surprisingly, the SO₂ mol­ecule is more weakly bound to sodium than is found in other sodium–SO₂ complexes and the SO₂ mol­ecule is essentially undistorted compared to the structure of free SO₂. The Na⁺ cation has a coordination number of eight in a distorted twofold-capped trigonal prism and makes contacts to three individual boron cluster anions, resulting in an overall three-dimensional network. Although the number of known η¹-O-coordinated SO₂ complexes is growing, sodium-SO₂ complexes are still rare.

Properties of perhalogenated {closo-B10} and {closo-B11} multiply charged anions and a critical comparison with {closo-B12} in the gas and the condensed phase

Dependence of electronic properties and reactivity of closo-borates with size and halogen substituent was investigated.

Manifestations of Weak O-H···F Hydrogen Bonding in M(H2O) n(B12F12) Salt Hydrates: Unusually Sharp Fourier Transform Infrared ν(OH) Bands and Latent Porosity (M = Mg-Ba, Co, Ni, Zn)

Eight M(H₂O) _n(Z) salt hydrates were characterized by single-crystal X-ray diffraction (Z^2- = B₁₂F₁₂^2-): M = Ca, Sr, n = 7; M = Mg, Co, Ni, Zn, n = 6; M = Ba, n = 4, 5. Weak O-H···F hydrogen bonding between the M(H₂O) _n²⁺ cations and Z^2- resulted in room-temperature Fourier transform infrared (FTIR) spectra having sharp ν(OH) bands, with full widths at half max of 10-30 cm^-1, which are much more narrow than ν(OH) bands in room temperature FTIR spectra of most salt hydrates. Clearly resolved ν_asym(OH/OD) and ν_sym(OH/OD) bands with Δν(OH) as small as 17 cm^-1 and Δν(OD) as small as 11 cm^-1 were observed (Δν(OX) = ν_asym(OX) - ν_sym(OX)). The isomorphic hexahydrates ( R3̅) have two fac-(H₂O)₃ sets of H₂O ligands and nearly octahedral coordination spheres. They exhibited four resolvable ν(OH) bands, one ν_asym(OH)/ν_sym(OH) pair for H₂O ligands with longer O(H)···F distances and one ν_asym(OH)/ν_sym(OH) pair for H₂O ligands with shorter O(H)···F distances. The ν(OH) bands for the three H₂O molecules with shorter, slightly stronger O(H)···F hydrogen bonds were broader, more intense, and red-shifted by ca. 25 cm^-1 relative to the bands for the three other H₂O molecules, the first time that such small differences in relatively weak O(H)···F hydrogen bonds in the same crystalline hexahydrate have resulted in observable IR spectroscopic differences at room temperature. For the first time room temperature ν(OH) values for salt hexahydrates showed the monotonic progression Mg²⁺ > Co²⁺ > Ni²⁺ > Zn²⁺, essentially the same progression as the p K_a values for these metal ions in aqueous solution. A further manifestation of the weak O-H···F hydrogen bonding in these hydrates is the latent porosity exhibited by Ba(H₂O)_5,8(Z), Sr(H₂O) _n,m(Z), and Ca(H₂O)_4,6(Z). Finally, the H₂O/D₂O exchange reaction Co(D₂O)₆(Z) → Co(H₂O)₆(Z) was ca. 50% complete in 1 h at 50 °C in N₂/17 Torr H₂O( g).