Home – Home – Jornals – Journal of Structural Chemistry 2011 number 1

The spatial and electronic structures of a series of substituted germylene molecules are calculated by DFT and HF methods using the PC GAMESS-Firefly program package. Molecular structures are optimized at the DFT (B3LYP/6-31G(2d,p)) level; wave functions and topological characteristics of the electron density distribution are calculated in the HF/acc-pvtz approximation. By means of NBO and AIM methods, the main characteristics of Ge-X bonds in these molecules are determined. The Ge-X bonds are shown to be the intermediate type bonds. The energies of these bonds are estimated.

A solution of the problem of conditional convergence is obtained in the calculation of Coulomb and multipole energy contributions within direct summation over the crystal lattice. The values correcting the results of the direct summation are shown to have the universal character described by the Lorentz tensor whose components are determined only by crystal symmetry and the direct summation method.

Geometric parameters, vibrational spectra, and the energies of isomerization of seven keto-enol isomeric forms of the H₂Salen molecule (N,N′-ethylene-bis(salicylidenimine)) are calculated using electron density functional theory (DFT/B3LYP) and correlation consistent valence triple-zeta Gaussian basis sets (сс-pvtz). The isomer with two enol groups (EE₁) and C₂ symmetry configuration is most energetically favorable. Calculations of the keto-enol equilibrium show that at Т ≥ 250 K the H₂Salen gas phase is a mixture of four conformers (rotamers of the main isomer EE₁). The contribution of other isomers does not exceed a few percent. The NBO analysis reveals that the system of π-conjugated bonds involves not only the atoms of the benzene moiety, but also the O, C, and N atoms nearest to the benzene ring. The energy stabilization of the isomer EE₁ is shown to be due to the presence of two strong intramolecular N…H hydrogen bonds. Intramolecular N…H and O…H hydrogen bonds are observed in all other isomers. The bathochromic shift of O-H and N-H vibrational frequencies, caused by the effect of hydrogen bonds, is 520-790 cm^-1.

The self-association of di-iso-butylaluminum hydride and di-iso-butylaluminum chloride is studied at the level of density functional theory and second order Möller-Plesset perturbation theory. Thermodynamic parameters of the monomeric, dimeric, trimeric, and tetrameric forms of HAlBu and ClAlBu in a range of 203 K to 373 K are calculated. The energy of solvation is taken into account by the COSMO polarized continuum model. Based on the obtained results the equilibrium concentrations of the associated forms of organoaluminum compounds (OACs) are calculated, which agree with the experimental data. So, at room temperature the dimeric or trimeric forms of OACs are dominant in the gas phase and non-polar solvents; the tetrameric form is present, while the concentration of the monomeric form is negligibly low and decreases with decreasing temperature or diluting.

The structures of a closo-hedral cluster (HAlNH)₁₂ and endohedral complexes ^4/2X@(HAlNH)₁₂ (X = N, P, As, C^-, Si^-) are studied by density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency (ν₁), energetic parameters, magnetic shielding constants (σ), and nucleus independent chemical shifts (NICSs) are discussed. It is found that all guest species are minima at the cage center. Inclusion energies (ΔE_inc) of all species are negative except those of ⁴N and ^4/2P. In all species, the endohedral quartet states (⁴X) are energetically less favorable than their doublet states (²X). The calculations predict that caged X states only donate <0.50 e to the cage and preserve their unencapsulated ground states.

Due to the publication of a number of contradictory assignments of the vibrational wave numbers of rotational isomers of acrolein in the ground electronic state, the analysis of their vibrational spectra is repeated based on the previously calculated scaled ab initio force fields. With the use of the reported results that predicted the force fields of trans-acrolein in the ¹(n,π*) and ³(n, π*) states at the CASSCF/cc-pVTZ level, the experimental vibrational bands are analyzed in these excited electronic states based on well-established regularities. It is noted that in the assignment of the calculated vibrational wave numbers of the molecule, the isotopic shifts in the ground and excited electronic states ¹(n, π*) and ³(n, π*) are taken into account. The previously considered calculated potential curves of the internal rotation of acrolein in combination with the data on the difference in the enthalpies (ΔH₀) of conformers allow a choice to be made in favor of one of the variants of the torsional vibration wave numbers that have been reported in the literature.

A model is introduced for the conductivity of carbon-nanotube polymer composites based upon percolation theory and fractals. These types of polymer composites have been developed in the recent years, and experimental data on their percolation threshold is available. We constructed a fractal space with the aim of the generalized Mandelbrot-Given curve and used the experimental critical exponent of conductivity to calculate the parameters of such a curve. Finally, the moments of the current distribution function are estimated, and the effect of the critical exponent on this function is investigated.

A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ) study of the molecular structure of 2-nitrobenzenesulfonic acid (2-NBSA) is performed. Quantum chemical calculations show that the 2-NBSA molecule has five conformers, and the Gibbs energy of one of them is lower by more than 4.5 kcal/mol than the energy of the other conformers. It is found experimentally that the saturated vapor of 2-NBSA at Т = 394(5) K contains only the low-energy conformer that has an intramolecular hydrogen bond between the H atom of the hydroxyl group and one of the О atoms of the NO₂ group. The C-C-S-O(Н) torsion angle determining the position of the S-O(Н) bond is -72(7)°, while the NO₂ group is substantially turned relative to the benzene ring plane (C1-C2-N-O = 40(5)°). The following experimental values of the internuclear distances are obtained for this conformer (Å): r_h1(C-H)_av = 1.07(2), r_h1(C-C)_av = 1.401(4), r_h1(C-S) = 1.767(6), r_h1(S=O)_av = 1.412(4), r_h1(S-O) = 1.560(6), r_h1(N-O)_av = 1.217(5), r_h1(C-N) = 1.461(8), r_h1(O-H) = 0.99(3).

The high-field ¹⁹F and ⁹¹Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only and F^- ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ( [F₅Zr-OO-ZrF₅]^4- dimer) was detected. The dimer structure is confirmed by ¹⁹F and ⁹¹Zr NMR. In high fields (¹⁹F NMR frequency > 200 MHz), the fluorine exchange between and F^- is slow in the ¹⁹F NMR scale and has a multisite character.

The structure of particles in zirconium n-butoxide solutions in n-butyl alcohol is determined by means of EXAFS, SAXS, and molecular mechanics modeling. Zirconium atoms are found to be bonded to each other via the oxygen atom and to form large anisotropic particles in the solution. Primary particles have a shape close to spherical; their diameter together with the solvate shell is 28.9 Å. These particles then aggregate into anisotropic structures. During solution aging under normal conditions without contact with the atmosphere, the particle anisotropy increases because of the aggregation of complexes. When the solution concentration decreases, the particles are divided into primary spherical particles with a characteristic size of 28.9 Å. The described changes are confirmed by a decrease in the number of Zr-Zr distances of 4.8 Å and 5.1 Å, which according to the EXAFS data, correspond to the bonds between the primary particles. The characteristic maximum sizes of particles in solutions with concentrations from 0.1 g to 0.003 g ZrO₂/ml are 160-80 Å.

Iron(III)-containing complexes with an asymmetric tridentate azomethine 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-N′-ethyl-N-ethylenediamine ligand with Cl^-, and BF counterions are synthesized. The presence of the complexation ion is confirmed by the far FTIR spectra. The structure of the compounds is determined by the matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) method. The results of mass-spectrоmetric studies are consistent with the elemental analysis data. The complexation of iron salts with the asymmetric tridentate ligand is found to yield compounds of the 1:1 composition with octahedral packing of iron in the complex.

The hindered rotation model is used to generalize the association equilibria theory for the case of a dense dipolar hard sphere (DHS) liquid. The derived expressions for the orientation constant of association and the Kirkwood factor of a DHS liquid are well consistent with machine experiments in the high temperature region.

Partial molar volumes  of amino acids in an aqueous urea solution are studied. For a saturated urea solution  equals the molar volume of the amino acid, therefore, in the saturated solution, the amino acid dissolves without changing the system volume. Hydrophobic effects are manifested in the volumetric characteristics only in dilute (<1 mol/kg) urea solutions. Within a three-layer hydration model, the numbers of amino acid hydration are found. By the example of alanine and leucine, it is shown that their decrease with increasing urea concentration is determined by a zwitterionic moiety and does not depend on the size of the hydrocarbon radical of the amino acid.

In this paper, an analytical expression to the steam-water dipole orientation parameter is proposed. The calculations have been carried out under the presumptions that: the electric properties of the water molecules are characterized completely by a permanent dipole moment and
a constant scalar polarizability, that translational fluctuations may be neglected, and that the positions are orientation-free. The results have been presented in the form of continuous and integrable expressions which could be easily compared to precedent studies as well as involved in similar analytical models

From the solution of the system Na₂WO₄-HNO₃-Ni(NO₃)₂-H₂O acidified to Z = ν(H⁺)/ν(WO) = 1.29, the green crystals of nickel paratungstate B Ni₅[W₁₂O₄₀(ОН)₂]·37H₂O are isolated. By FTIR spectroscopy the isopoly anion is shown to belong to the structural type of paratungstate B. Using single crystal X-ray analysis, the structure of Ni₅[W₁₂O₄₀(ОН)₂]·37H₂O is solved (M_r = 3840.36, monoclinic, P2₁/c space group, a = 21.9061(6) Å, b = 14.9297(4) Å, c = 22.1391(6) Å, β = 107.609(3)°, V = 6901.4(3) ų at T = 293 K, Z = 4, d_x = 3.696 g/cm³, F₀₀₀ = 6944, μ = 21.368 mm^-1, -33 ≤ h ≤ 33, -22 ≤ k ≤ 22, -33 ≤ l ≤33; the final uncertainty values for the observed reflections are R_F = 0.0532, wR² = 0.0831 (R_F = 0.1088, wR² = 0.0894 over all independent reflections), S = 0.978; CSD-421468).

The structure of aluminum(III) tris-dipivaloylmethanate (Bruker Nonius X8 Apex diffractometer with a 4K CCD detector, λMoK_α, graphite monochromator, T = 150(2) K) is determined, and the synthetic procedure for its preparation is suggested. Crystal data are: C2/c space group, a = 28.1587(12) Å, b = 18.5170(7) Å, c = 21.5332(8) Å, β = 97.573(1)°, V = 11129.8(8) ų, Z = 12, d_x = 1.033 g/cm³, R = 6.93. The complex has a molecular structure; the aluminum atom is octahedrally surrounded by six oxygen atoms of three chelating ligands; Al-O distances are 1.860(2)-1.873(2) Å; O-Al-O angles fall within 88.08(9)-91.96(10)° and 177.93(9)-179.83(14)°. The known crystal packings of metal tris-dipivaloylmethanates are analyzed. Three types of the arrangement of the molecules in the crystals denoted as α, β, and γ are identified.

Complex salts [Ir(NH₃)₅Cl]_x[Rh(NH₃)₅Cl]_1-xMO₄ (x = 0.5, 1; M = Mo, W) are synthesized and their thermal properties are studied. The crystal structures are determined for [Ir(NH₃)₅Cl]WO₄ and [Ir(NH₃)₅Cl]MoO₄. In the structures, the ions are linked by N-H…O hydrogen bonds, the shortest ones being 2.868(2)-3.422(2) Å and 2.860(4)-3.434(3) Å respectively. The thermal properties of the complex salts are studied in the hydrogen atmosphere and in hydrogen-helium mixtures. It is demonstrated that the final products are the mixtures of nanocrystalline powders of Ir and binary or ternary solid solutions with the hcp lattice.

The crystal structures of the compounds trans-[Rh(en)₂Cl₂]Cl₂^.H₅O₂ (I), trans-[Rh(en)₂Cl₂]ClO₄ (II), and trans-[Rh(en)₂Cl₂]ReO₄ (III) are determined. The crystal data are: I, a = 10.860(3) Å, b = 7.795(2) Å, c = 9.023(3) Å; β = 111.56(10)°, P2₁/с space group, Z = 4, d_x = 1.875 g/cm³; II, a = 6.593(2) Å, b = 8.309(3) Å, c = 11.922(4) Å, α = 83.55(10)°, β = 79.80(10)°, γ = 75.38(10)°, space group, Z = 2, d_x = 2.106 g/cm³; III, a = 6.533(2) Å, b = 16.391(4) Å, c = 12.411(3) Å; β = 98.30(10)°, P2₁/c space group, Z = 4, d_x = 2.749 g/cm³. The compounds are examined by IR spectroscopy and powder XRD. The solubility of the isolated crystalline phases in water decreases in the following order: trans-[Rh(en)₂Cl₂]Cl₂·H₅O₂ > trans-[Rh(en)₂Cl₂]ClO₄ > trans-[Rh(en)₂Cl₂]ReO₄.

Double complex salts (DCS) [RuNO(NH₃)₄(H₂O)]₂[MCl₄]Cl₄·2H₂O, M = Pt (I) and Pd (II), are prepared and characterized using IR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Crystalline phases of I and II are isostructural (P2(1)/n space group) and have the following crystallographic characteristics: a = 6.689 Å, b = 15.609 Å, c = 12.348 Å, V = 1289.1 ų, Z = 2, d_x = 2.425 g/cm³ (I) and a = 6.637 Å, b = 15.521 Å, c = 12.244 Å, V = 1261.2 ų, Z = 2, d_x = 2.255 g/cm³ (II). The thermolysis of the obtained DCS in the hydrogen atmosphere affords two-phase mixtures of limited solid solutions of the metals: hcp for ruthenium-based ones and fcc for Pt or Pd based solutions. On decomposition in the helium atmosphere the products contain a minor amount of RuO₂. For the phases obtained during thermolysis the parameters are determined and the compositions are estimated. The heating of I to 400°C in the helium-air atmosphere yields a nanocrystalline composite Pt+RuO₂ with CSR of ~20 nm.

The thermal reaction of Ru₃(CO)₁₂ with the saturated fatty acids (heptanoic, nonanoic, decanoic, tridecanoic, tetradecanoic, heptadecanoic, octadecanoic) in refluxing tetrahydrofuran, followed by addition of triphenylphosphine (PPh₃) or pyridine (C₅H₅N), gives the dinuclear complexes Ru₂(CO)₄{OOC(CH₂)_nCH₃}₂L₂ (1: n = 5, 2: n = 7, 3: n = 8, 4: n = 11, 5: n = 12,
6: n = 15, 7: n = 16; a: L = NC₅H₅, b: L = PPh₃). The single-crystal structure analysis of 1b, 2a, 3a, 4a and 5a reveals a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two L ligands occupy the axial positions at the ruthenium atoms. In 2a, π-π stacking interactions between adjacent pyridyl units of symmetry related molecules prevail, while in the longer alkyl chain derivatives 3a, 4a and 5a, additional van der Waals and electrostatic interactions between the alkyl chains take place as well in the packing arrangement of the molecules, thus giving rise to layers of parallel alkyl chains in the crystal.

A polymeric silver(I) complex, bis(N-methylthiourea)silver(I) nitrate, {[Ag(Metu)₂]NO₃}_n is prepared and its crystal structure is determined by X-ray crystallography. The compound crystallizes in the monoclinic C2/c space group. In the structure, distorted AgS₄ tetrahedra are linked through the sulfur atoms of the Metu ligand to form isolated infinite chains of the type [Ag(SR)₂]. The cationic chains are separated from each other by nitrate ions that do not coordinate to the metal ion. The chains are bridged via N-H…O hydrogen bonds involving the nitrate ions. The complex exhibits an Ag---Ag separation of ~3.21 Å indicating the existence of significant argentophilic interactions. An upfield shift in the >C=S resonance of Metu in ¹³C NMR and downfield shift in the N-H resonance in ¹H NMR are consistent with sulfur coordination to silver(I).

The crystal structures of three new chloride-iodide cluster complexes of Mo(II) of the compositions (H₇O₃)₂[(Mo₆Cl_7.22I_0.78)Cl₆]·3H₂O (1), (H₉O₄)₂[(Mo₆Cl_6.66I_1.34)Cl₆] (2), and (H₅O₂)₂[(Mo₆Cl_6.36I_1.64)Cl₆]·2H₂O (3) are determined. All cluster anions in 1-3 are derived from octahedral halide-bridged clusters {Mo₆(μ₃-Hal)₈}⁴⁺ (Hal = Cl, I). The iodide ligands are disordered over three μ₃-positions. According to mass-spectrometry, all these compounds are solid solutions of the hydroxonium salts of [(Mo₆Cl₆I₂)Cl₆]^2- and [(Mo₆Cl₇I)Cl₆]^2-. Small changes in the iodine content of the cluster cores give rise to changes in the composition of the hydroxonium cations, in the hydrogen bonding network and can lead to changes in the structural type. The cluster anions are packed according to the fcc (1, 3) or hcp (2) motifs.

By the interaction of aqueous solutions of salts of the [Re₆Se₈(CN)₆]^4- cluster anion with salts of Nd(III), Tb(III), and Yb(III) lanthanides in the presence of tetraatomic alcohol erythritol (butane-1,2R,3S,4-tetraol) three new compounds are obtained: K[Nd(C₄H₁₀O₄)(H₂O)₄{Re₆Se₈(CN)₆}]·4H₂O (space group, a = 11.544 Å, b = 13.643 Å, c = 13.838 Å, α = 111.97°, β = 108.08°, γ = 90.08°) (1); [{Yb₂(C₄H₉O₄)₂×(H₂O)₂}{Re₆Se₈(CN)₆}]·5H₂O ( space group, a = 10.308 Å, b = 10.505 Å, c = 11.154 Å, α = 88.21°, β = 81.83°, γ = 78.50°) (2); [{Tb₂(C₄H₉O₄)₂(C₄H₁₀O₄)}{Re₆Se₈(CN)₆}]·4H₂O (space group, a = 10.002 Å, b = 10.276 Å, c = 11.762 Å, α = 91.32°, β = 104.01°, γ = 106.02°) (3). The structures of these compounds are the coordination polymers (chain (2) and grids (1 and 3)) with different coordination modes of erythritol to the lanthanide cations.

The [2+2]-cycloaddition reaction of N-vinylcaprolactam with 3-chlorophenylcyanate yielding 1-(3-chlorophenyl)-4-[1Н-perhydroazepinone-2]-azetidinone-2 is studied. The structure of the obtained compound is determined by single crystal XRD.

Gossypol forms stable solvates with 4- and 2-picolines at room temperature. The solvates are investigated by single crystal X-ray diffraction and thermal analysis. Solvate crystals of gossypol with 4-picoline (1) have the 1:3 composition (gossypol:4-picoline) and crystallize in the P2₁/с space group. This substance is isostructural to a trisolvate of gossypol with pyridine. Solvate crystals of gossypol with 2-picoline (2) have the 1:4 composition (gossypol:2-picoline) and crystallize in the P-1 space group. The unit cell parameters for the investigated structures are as follows: 1 monoclinic crystals, C₃₀H₃₀O₈·3C₆H₇N, a = 10.7530(1) Å, b = 20.7834(3) Å, c = 19.1166(2) Å, β = 95.537(1)°, V = 4252.32(9) ų, M = 797.92, Z = 4, d_x = 1.246 g/cm³, and R = 0.0489 for 4102 reflections; 2 triclinic crystals, C₃₀H₃₀O₈·4C₆H₇N, a = 11.467(1) Å, b = 14.962(2) Å, c = 15.570(3) Å, α = 75.62(1)°, β = 69.83(1)°, γ = 79.58(1)°, V = 2414.6(7) ų, M = 891.04, Z = 2, d_x = 1.226 g/cm³, and R = 0.0528 for 3779 reflections. The results of the single crystal XRD and thermal analysis confirm that gossypol with 4-picoline forms a trisolvat, and a tetrasolvate with 2-picoline. The transition from 4-picoline to 2-picoline proves to change the type of the host-guest association from one-dimensional to zero-dimensional, i.e., to lead to a new crystal structure. Desolvation of compound 2 begins at a lower temperature than that for compound 1, which is explained by their different crystal structures.

The natural compound gossypol forms a stable clathrate with acridine. The composition of the clathrate is C₃₀H₃₀O₈·0.5C₁₃H₉N. The unit cell is monoclinic, C2/c space group, a = 11.3213(3) Å, b = 30.5957(13) Å, c = 17.0824(4) Å, γ = 94.153(2)°, V = 5901.5(3) ų, M = 1153.24, Z = 8, d_x = 1.369 g/cm³, and R = 0.0413 for 4726 reflections. The structure of the clathrate allows one to refer this compound to the ethyl acetate isomorphic host-guest group of gossypol complexes.

The 3-[4-fluorophenylazopentandion]-2,4 reagent is synthesized based on acetylacetone, and its crystal and molecular structure is studied by X-ray diffraction. It is found that [C₁₁H₁₁N₂O₂F] crystals 1 belong to the monoclinic symmetry, C2/c space group. The unit cell parameters of 1 are a = 18.827(3) Å, b = 12.839(2) Å, c = 26.475(5) Å, β = 104.834(2)°. The analysis shows that the reagent is present in the solution as well as in the crystal. A comparative analysis of these three structures with the reported data is carried out.

At T = 150 K the crystal structure of [Сu(en)₂](ReO₄)₂ (en is ethylenediamine) is studied: a = 6.6229(1) Å, b = 14.2968(3) Å, c = 7.4859(2) Å, β = 102.415(1)°, V = 692.24(3) ų, P2₁/c space group, Z = 2, d_x = 3.282 g/cm³. Packing of complex cations is shown to be single layered and pseudohexagonal. Perrhenate anions are located between these layers and additionally coordinate copper atoms with Cu…O distances being 2.504(3) Å.

We have previously reported the results of studies of the hydrogen bond nature in N-phenyl-N′-isopropyl-p-phenylenediamine by a quantum chemistry method and FTIR spectroscopy [1-3]. It is shown that the IR spectrum of N-phenyl-N′-isopropyl-p-phenylenediamine has IR bands in the νNH absorption region at 3380 cm^-1 and 3400 cm^-1 corresponding to the NH groups involved in hydrogen bonding.

The title compound [In(C₂₂H₃₀N₄O₄)]Cl (I) bis[(N-salicylidene-N′-(2-hydroxyethyl)ethyleneediamine)indium(III) chloride is prepared, and its crystal structure is determined by single crystal X-ray diffraction at room temperature. The complex crystallizes in the monoclinic space group P2₁/n, a = 9.9704(6), b = 24.9554(15), c = 10.5707(6) Å, β = 116.46(2)°, V =
= 2354.6(2), Z = 4. The X-ray analysis reveals that the In^III ion is surrounded by four nitrogen and two oxygen atoms from two ligands leading to a distorted octahedral geometry. The molecule has the form of tongs at a junction point with the metal. Five membered rings adopt envelope conformation. In the crystal structure, the molecules are linked via N-H…Cl, O-H…O, O-H…Cl, and C-H…Cl intermolecular interactions. The structure is further stabilized by C-H…π (arene) interactions.

Diammine(malonato)palladium(II) is synthesized by the reaction of [Pd(NH₃)₄](NO₃)₂ with malonic acid, and its crystal structure is determined by single crystal X-ray diffraction. Distorted coordination square of the Pd(II) atom is formed by two N atoms of two ammonia molecules and two O atoms of bidentate malonate ligand. The average Pd-N and Pd-O distances are 2.018(7) Å and 2.014(2) Å, respectively. The molecules are stacked in such a way that the planes of coordination squares are parallel with the Pd?KPd distances between the nearest neighbors in a stack of 4.039 Å.

Single crystal X-ray diffraction is used to investigate the cocrystals of 3-(1-amino-2,2,2-trifluoroethylidene)-2-imino-1,1,4,5,6,7-hexafluoroindane (1) with 1,4-dioxane at temperatures of 100 K, 200 K, and 273 K. The study shows that compound 1 is in equilibrium with its tautomer: 2-amino-3-(1-imino-2,2,2-trifluoroethyl)-1,1,4,5,6,7-hexafluoroindene (1a).

The crystal structure of 2,2-difluoro-4-(9Н-fluorene-2-yl)-6-methyl-1,3,2-dioxaborine (С₁₃H₉COCH×COCH₃BF₂) (1) is determined. The structural and spectral luminescent characteristics of 1 are compared to those of its electron analogue: 2,2-difluoro-4-(4-phenylphenyl)-6-methyl-1,3,2-dioxaborine (С₆H₅C₆H₄×COCHCOCH₃BF₂).