Coordination compounds of electron-deficient boron cluster anions BnH n2? (n = 6, 10, 12)

This survey concerns the coordination ability of B _n H _n ²⁻ (n = 6, 10, 12) boron cluster anions and their derivatives in complex formation. Boron cluster anions form four types of compounds: salts of organic cations and alkali-metal cations, including Cat₂B _n H _n , where specific interactions can be observed between a cation Cat and a boron cluster anion; salts of protonated anions CatB₆H₇ and CatB₁₀H₁₁, analogues of Cat[MB _n H _n ] complexes, where an extra hydrogen atom appears bound with the BBB face of a boron polyhedron and performs as a hard acceptor; metal complexes with outer-sphere boron cluster anions where specific ligand-ligand interactions may be observed between a boron cluster anion and an inner-sphere ligand; and true metal complexes with boron cluster anions that enter the inner coordination sphere. The last case characterizes closo-hydroborate anions as polydentate ligands whose denticity can vary widely under the effect of substituents or other ligands in the complex.     

Isomerism of metal complexes with the boron cluster anions B10H 102? and B12H 122?

A new type of inner-sphere isomerism in coordination chemistry observed in metal complexes with boron cluster anions B _n H _n ²⁻ (n = 10, 12) is discussed. Specific structure of the closo-borohydride anions gives rise to edge and facial isomers, among which mirror isomers have been found. Examples of edge and facial isomers of metal complexes with the B₁₀H₁₀²⁻ and B₁₂H₁₂²⁻, anions obtained experimentally and studied by X-ray diffraction are considered. Analysis of their structure revealed a new type of isomerism, which was called “positional.”     

Multicenter interactions in lead(II) coordination compounds with B n H n 2? = 6, 10, 12) cluster anions and their derivatives

The structures of earlier synthesized Pb(II) complexes with closo-BnH _n ²⁻ (n = 6, 10, 12) anions and their derivatives are analyzed in terms of M-B and M-H-B distances and MHB angles. In all of the complexes, the metal-ligand bonds are due to pure (MHB)-, (MHB)-₂, or (MHB)₃-type multicenter interactions or their combination. The existence of straight M-B bonds (M-B(H) type) along with the above interactions was deduced only for the lead(II) complex with the closo-hexaborate anion. Original Russian Text ? E.A. Malinina, L.V. Goeva, N.T. Kuznetsov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 3, pp. 464–471.     

Specific interactions in metal salts and complexes with cluster boron anions BnH n2? (n = 6, 10, 12)

Specific interactions that appear in metal salts and complexes with cluster boron anions B _n H _n ²⁻ (n = 6, 10, 12) have been discussed. These interactions, as well as chemical bonds, involve vertices, edges, or faces of boron polyhedra. Specific interactions have a considerable effect on the structure of compounds, making a significant contribution to the formation of the unit cell and forming supramolecular assemblies. Compounds containing B _n H _n ²⁻ cluster anions shed new light onto the nature of specific interactions owing to their many-center character and great variety.     

Theoretical studies on anionic clusters of sulfate anions and carbon dioxide, SO 4?1/?2 (CO2)n, n?=?1?4

Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO₄^−1/−2(CO₂) _n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O₃SO–CO₂ bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O₃S–O–CO₂]⁻², [O₃S–O–C(O)O–CO₂]⁻², and [O₂C–O–S(O₂)–O–CO₂]⁻², where one or two oxygens of SO₄⁻² are shared with CO₂. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO₄^−1/−2(SO₂) _n and CO₃^−1/−2(SO₂) _n clusters, the binding energies are smaller for the present SO₄^−1/−2(CO₂) _n systems, while stabilization of the dianion occurs at n = 2 for both SO₄⁻²(CO₂) _n and SO₄⁻²(SO₂) _n , but only at n = 3 for CO₃⁻²(SO₂) _n .     

Ab initio study of the structure and stability of ThF n(4?n)+ complexes (n = 1–8)

The structural and energetic characteristics of ThF _n ⁽⁴⁻ⁿ⁾⁺ (n = 1–8) complexes have been calculated by the ab initio RHF and MP2 methods.     

Ab initio study of the structure and stability of LaCl n(3 ? n)+ complexes (n = 1?8)

The structural and energetic characteristics of LaCl _n ^{(3 − n)+} (n = 1−8) complexes have been calculated by the ab initio MP2 method. Original Russian Text ? V.Yu. Buz’ko, Kh.B. Kushkhov, M.B. Buz’ko, V.T. Panyushkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 11, pp. 1899–1905.     

Theoretical study of the structure and stability of cage-substituted icosahedral closo-boranes, alanes, and gallanes MiM′12 ? iH 122? (M, M′ = B, Al, and Ga; i = 0–12)

The equilibrium geometric parameters and energetic and spectroscopic characteristics of low-lying conformers for several series of model cage-substituted (mixed) borane, alane, and gallane closo-dianions M _i M′_{12 − i} H₁₂²⁻(M, M′ = B, Al, Ga), as well as of “bare” gallium-aluminum anions Ga _i Al_12−i ⁻ with i = 0–12, were calculated within the B3LYP approximation of the density functional theory using 6–31G* and 6–311+G** basis sets. Differences in structure and stability between alanoborane clusters of similar composition are revealed. In clusters where the M and M’ heteroatoms are close in size and electronegativity (in gallonoalanes and gallium-aluminum anions), successive substitutions of M′ for M are accompanied by small energy changes and occur quasi-stochastically in different positions of the cage. When the substituents are significantly different (in alanoboranes), mixed clusters are unstable against disproportionation into homonuclear “predecessors” M₁₂H₁₂²⁻ and M′₁₂H₁₂²⁻, and the most favorable M _i M′_{12 − i} H₁₂²⁻ structures among them are those in which M _i M′_{12 − i} the cages are subdivided into homonuclear “subclusters” M _i and M′t′_12−i with a maximal number of homonuclear bonds (M-M and M′-M′) and a minimal number of heteronuclear bonds (M-M′).     

Exchange coupling in alkoxy-polyoxovanadates [VIVnVV6?nO7(OR)12]4?n (n = 4, 3, 2)

The molecular structure and magnetic properties of alkoxy-polyoxovanadates [V^IV _n V^V _6−n O₇(OR)₁₂]⁴⁻ⁿ (n = 4, 3, 2) were studied within the framework of the DFT approach. The equilibrium geometric configurations of all complexes studied in this work are characterized by a distorted octahedral hexavanadate core; the unpaired d-electrons are localized on the metal centers (V^IV). The localized spin density distribution is also retained in the low-temperature crystal structures of the compounds whose magnetic properties are described by the Heisenberg-Dirac-van Vleck exchange spin Hamiltonian. The exchange parameters calculated using the broken symmetry formalism suggest predominance of ferromagnetic coupling between vanadium(IV) ions in the μ-OR bridged dimeric units {V^IVO(OR)V^IV} and in the diagonal pairs {V^IVOV^IV} (n = 4). The results obtained indicate that the magnitude and sign of the exchange parameters in the isostructural dimeric units within the hexavanadate core depend on the total number of unpaired electrons in the system.     

Decavanadates with complex cations: synthesis and structure of (NH4)2[M(H2O)5(NH3CH2CH2COO)]2V10O28·nH2O (M?=?ZnII, n?=?4; M?=?MnII, n?=?2)

Decavanadates with complex cations, (NH₄)₂[Zn(H₂O)₅(NH₃CH₂CH₂COO)]₂V₁₀O₂₈·4H₂O (4) and (NH₄)₂[Mn(H₂O)₅(NH₃CH₂CH₂COO)]₂V₁₀O₂₈·2H₂O (5), have been prepared and characterized by elemental analysis, i.r., Raman, UV–vis. and ⁵¹V-n.m.r. spectroscopies and by thermal analysis. The X-ray structure determination revealed, both in 4 and 5, the presence of complex cations with hexacoordinated central atoms and monodentate β-alanine ligands, and decavanadate V₁₀O₂₈ ⁶⁻ anions. The differences in the structural arrangement in 4 and 5 are probably a consequence of the different ionic radii of Zn²⁺ and Mn²⁺ (high spin).     

Subsolidus binary phase diagram of (n-CnH2n+1NH3)2ZnCl4 (n?=?14, 16, 18)

The thermotropic phase solid–solid transitions compound (n-C _n H_2n+1NH₃)₂ZnCl₄ (n = 14, 16, 18) were studied, and a series of their mixtures were prepared. These laminar materials contain bilayers sandwiched between metal halide layers. The low temperature crystal structures of the pure salts are characteristic of the piling of sandwiches in which a two-dimensional macro-anion ZnCl₄ ²⁻ is sandwiched between two alkylammonium layers. These layers become conformationally disordered in the high temperature phases. The subsolidus binary phase diagrams of (n-C₁₄H₂₉NH₃)₂ZnCl₄-(n-C₁₈H₃₇NH₃)₂ZnCl₄ and (n-C₁₆H₃₃NH₃)₂ZnCl₄-(n-C₁₈H₃₇NH₃)₂ZnCl₄ were established by differential thermal analysis and X-ray diffraction. In each phase diagram, an intermediate compound and two eutectoid invariants were observed. There are three noticeable solid solution ranges (α, β, γ) at the left boundary, right boundary, and middle of the phase diagram.     

Theoretical and experimental study of fullerenol molecules and ions C60(OH)24 ? n(OL)n and C60(OH)24 ? n(OL)nL+ successively substituted by Alkali Metal atoms L (n = 1?24)

The equilibrium geometric parameters and the energetic characteristics of fullerenol molecules and ions C₆₀(OH)_{24 − n} (OL) _n and C₆₀(OH)_{24 − n} (OL) _n L⁺ successively substituted by alkali metal atoms L with the number of substitutions n = 1–24 have been calculated by the density functional theory B3LYP/6-31G* method. For all compounds, the structure of the covalent [C₆₀O₂₄] cage in which the oxygen atoms are bound to the C atoms of the six-membered [C₆] rings of the fullerene cage, six O atoms per [C₆] ring. The lithium derivatives have been considered in most detail. Computations have shown that the first four single substitutions of Li for H in the OH groups attached to the same C₆ ring require very low energy inputs, no more than 1 kcal/mol, and can spontaneously occur under common conditions. The further fifth and sixth single substitutions in the same C₆ ring are endothermic, but the required energy inputs are also modest (on the order of few kcal/mol). The first and second cooperative substitutions of Li for H simultaneously in all four hydroxylated C₆ rings require energy inputs of ∼3 and 11.6 kcal/mol, respectively; in the third and fourth fourfold substitutions, the energies increase by ∼15–16 kcal/mol. The mean partial energy per single substitution of Li for H in this series (n = 1−6) is ∼2 kcal/mol. Calculations have predicted that all C₆₀(OH)_{24 − n} (OLi) _n molecules with intermediated degrees of substitution (n = 1−16) can be obtained under the conditions of relatively low energy inputs (for example, under the conditions of the MALDI experiment) and can exist in the isolated state. For the sodium- and potassium-substituted analogues, the qualitative pattern persists, but the H/Na and H/K substitutions are somewhat more endothermic. The computational results are compared with the MALDI mass spectrum of the [C₆₀(OH) _x (ONa) _y -CH₃COONa) system.     

Structure and luminescence of [Tb0.5(C6NO2H5)3(H2O)2]2n·(H3O)4n(ZnCl5)n(ZnCl4)2n

A novel bimetallic 4f-3d metal-isonicotinic acid inorganic-organic hybrid complex [Tb_0.5(C₆NO₂H₅)₃(H₂O)₂]_2n ·(H₃O)_4n (ZnCl₅) _n (ZnCl₄)_2n (1) is synthesized. It has a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that it displays interesting emissions in the violet, blue, green, and yellow regions.     

Theoretical study on homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO)n (n= 3–5) and Ru2(CO)n (n = 8, 9)

Homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO) _n (n = 3–5) and Ru₂(CO) _n (n = 8,9) have been investigated using density functional theory. Sixteen isomers are obtained. For Ru(CO)₅, the lowest-energy structure is the singlet D _3h trigonal bipyramid. Similar to Os(CO)₅, the distorted square pyramid isomer with C _2v symmetry lies ∼7 kJ·mol⁻¹ higher in energy. For the unsaturated mononuclear ruthenium carbonyls Ru(CO)₄ and Ru(CO)₃, a singlet structure with C _2v symmetry and a C _s bent T-shaped structure are the lowest-energy structures, respectively. The global minimum for the Ru₂(CO)₉ is a singly bridged (CO)₄Ru(μ-CO)Ru(CO)₄ structure. A triply bridged Ru₂(CO)₆(μ-CO)₃ structure analogous to the known Fe₂(CO)₉ structure is predicted to lie very close in energy to the global minimum. For Ru₂(CO)₈, the doubly bridged C ₂ structure is predicted to be the global minimum. For the lowest-energy structures of M₂(CO) _n (M = Fe, Ru, Os, n = 9,8), it is found that both iron and ruthenium are favored to form structures containing more bridging carbonyl groups, while osmium prefers to have structures with less bridging carbonyl groups. The study of dissociation energy shows that the dissociation of Ru₂(CO)₉ into the mononuclear fragments Ru(CO)₅ + Ru(CO)₄ is a less energetically demanding process than the dissociation of one carbonyl group from Ru₂(CO)₉ to give Ru₂(CO)₈.     

Molecular structures and electronic properties of helical thiophene carbon–sulfur oligomers, H2(C2S)nC2H2 (n?=?1–20)

Structure optimizations of the thiophene carbon–sulfur H₂(C₂S) _n C₂H₂ (n = 1–20) were carried out using density functional theory calculations at the B3LYP/6-31G(d) level. The B3LYP/6-31G(d) geometrical data for heptamer H₂(C₂S)₇C₂H₂ and undecamer H₂(C₂S)₁₁C₂H₂ are in good agreement with the X-ray crystallographic data for the helical (C₂S)_n β-heptathiophene and β-undecathiophene, respectively. Structural and electronic properties of helical oligothiophenes obtained at the B3LYP/6-311++G(d,p)//B3LYP/6-31G(d) level are reported. The strain energy formula of n oligothiophenes as a linear function of their molecular length was obtained.     

A Density Functional Investigation on C2Aun+ (n?=?1, 3, 5) and C2Aun (n?=?2, 4, 6): from Gold Terminals, Gold Bridges, to Gold Triangles

A systematic density functional theory investigation on C₂Au _n ⁺ (n = 1,3,5) and C₂Au _n (n = 2,4,6) indicates that gold atoms serve as terminals (–Au) in the chain-like C_s C₂Au⁺ (C=C–Au⁺) and D_∞h C₂Au₂ (Au–C≡C–Au) and as bridges (–Au–) in the side-on coordinated C_2v C₂Au₃ ⁺ ([Au–C≡C–Au]Au⁺) and C_s C₂HAu₂ ⁺([H–C≡C–Au]Au⁺). However, when the number of gold atoms reaches four, they form stable gold triangles (–Au₃) in the head-on coordinated C_2v C₂Au₄ (Au–C≡C–Au₃) and the side-on coordinated C_2v C₂Au₅ ⁺ ([Au–C≡C–Au]Au₃ ⁺). Similar –Au₃ triangular units exist in the head-on coordinated C_2v C₂HAu₃ (H–C≡C–Au₃) and D_2d C₂Au₆ (Au₃–C≡C–Au₃). The existence of stable –Au₃ triangular units in small dicarbon aurides is significant and intriguing. The high stability of Au₃ triangles originates from the fact that an equilateral D_3h Au₃ ⁺ cation possesses a completely delocalized three-center-two-electron (3c–2e) σ bond and therefore is σ-aromatic in nature. The extension from H/Au analogy to H/Au₃ analogy established in this work may have important implications in designing new gold-containing catalysts and nano-materials.     

Surface active and aggregation behavior of methylimidazolium-based ionic liquids of type [Cnmim] [X], n?=?4, 6, 8 and [X]?=?Cl?, Br?, and I? in water

The surface active and aggregation behavior of ionic liquids of type [C _n mim][X] (1-alkyl-3-methylimidazolium (mim) halides), where n = 4, 6, 8 and [X] = Cl⁻, Br⁻ and I⁻ was investigated by using three techniques: surface tension, ¹H nuclear magnetic resonance (NMR) spectroscopy, small-angle neutron scattering (SANS). A series of parameters including critical aggregation concentrations (CAC), surface active parameters and thermodynamic parameters of aggregation were calculated. The ¹H NMR chemical shifts and SANS measurements reveal no evidence of aggregates for the short-chain 1-butylmim halides in water and however small oblate ellipsoidal shaped aggregates are formed by ionic liquids with 1-hexyl and 1-octyl chains. Analysis of SANS data analysis at higher concentrations of [C₈mim][Cl] showed that the microstructures consist of cubically packed molecules probably through π–π and hydrogen bond interactions.     

Influence of the water molecules (n?=?1–6) on the interaction between Li+, Na+, K+ cations and indole molecule as tryptophan amino acid residue

Influence of the addition of water molecules (n = 1–6) on the interaction energy between Li⁺, Na⁺, K⁺ cations and indole molecule as tryptophan amino acid residue is considered at MP2(FULL)/6-311++G(d,p)//B3LYP/6-311++G(d,p) levels of theory. The calculations suggest that the size of cation and the number of water molecules are two important factors that affect the interaction energy between the hydrated metal cation and indole molecule. The strength of cation–π interactions get substantially reduced when the metal ion is solvated or the size of metal cation increases. Quantum theory of atoms in molecules analysis of cation–π interaction indicates that there is a correlation between the electron density (ρ(r)) in the cage critical points generated upon complexation and the distance between metal cation and centroid of phenyl ring in indole molecule.     

Phenyl(acyloxy)fluorosilanes C6H5Si(OCOR)nF3?n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)FCl

The method of synthesis of the hitherto unknown class of organosilicon compounds, phenyl(acyloxy)fluorosilanes C₆H₅Si(OCOR) _n F_3−n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C₆H₅Si(OCOR) FCl in up to 91% yield has been developed based on the reaction of phenyl(fluoro)chlorosilanes C₆H₅SiCl _n F_3−n (n = 1, 2) with trimethylsilyl esters of carboxylic acids Me₃SiOC(O)R [R = H, CH₃, CF₃, CCl₃, ClCH₂, BrCH₂, CH₂=CHCH₃, CH₂=CHPh, CH(CH₃)=CH₂, Ph].