Complexes of 4‐substituted phenolates with HF and HCN: Energy decomposition and electronic structure analyses of hydrogen bonding

We have computationally studied para‐X‐substituted phenols and phenolates (X = NO, NO₂, CHO, COMe, COOH, CONH₂, Cl, F, H, Me, OMe, and OH) and their hydrogen‐bonded complexes with B^? and HB (B = F and CN), respectively, at B3LYP/6‐311++G** and BLYP‐D/QZ4P levels of theory. Our purpose is to explore the structures and stabilities of these complexes. Moreover, to understand the emerging trends, we have analyzed the bonding mechanisms using the natural bond orbital scheme as well as Kohn–Sham molecular orbital (MO) theory in combination with quantitative energy decomposition analyses [energy decomposition analysis (EDA), extended transition state‐natural orbitals for chemical valence (ETS‐NOCV)]. These quantitative analyses allow for the construction of a simple physical model that explains all computational observations. © 2012 Wiley Periodicals, Inc.     

C3i‐Symmetric Octanuclear Cadmium Cages: Double‐Anion‐Templated Synthesis,Formation Mechanism,and Properties

A series of C_3i‐symmetric bicapped trigonal antiprismatic Cd₈ cages [2X@Cd₈L₆(H₂O)₆] ? n Y ? solvents (X=Cl^?, Y=NO₃^?, n=2: MOCC‐4 ; X=Br^?, Y=NO₃^?, n=2: MOCC‐5 ; X=NO₃^?, Y=NO₃^?, n=2: MOCC‐6 ; X=NO₃^?, Y=BF₄^?, n=2: MOCC‐7 ; X=NO₃^?, Y=ClO₄^?, n=2: MOCC‐8 ; X=CO₃^2?, n=0: MOCC‐9 ), doubly anion templated by different anions, were solvothermally synthesized by means of a flexible ligand. Interestingly, the CO₃^2? template for MOCC‐9 was generated in situ by two‐step decomposition of DMF solvent. For other MOCCs, spherical or trigonal monovalent anions could also play the role of template in their formation. The template abilities of these anions in the formation of the cages were experimentally studied and are discussed for the first time. Anion exchange of MOCC‐8 was carried out and showed anion‐size selectivity. All of the cage‐like compounds emit strong luminescence at room temperature.     

Chemistry of Ruthenium Polypyridine Complexes: IX. Nitro-Nitrosyl Equilibrium in cis-[Ru(2,2'-bpy)2(L)NO2]+ Complexes

Ruthenium(II) bisbipyridyl complexes cis-[Ru(bpy)₂(L)NO₂](BF₄) (bpy is 2,2'-bipyridyl) with 4-substituted pyridine ligands L = 4-(Y)py (Y = NH₂, Me, Ph, and CN) were obtained. The equilibrium constants of the reversible nitro-nitrosyl transition [Ru(bpy)₂(L)NO₂]⁺ + 2H⁺ [Ru(bpy)₂(L)NO]^{3 +} + H₂O were measured in solutions with pH 1.5-8.5 (ionic strength 0.4). The constants correlate with the protonation constants of free ligands 4-(Y)py.     

Effect of the X and Y substituents on the carbonyl bond in 4-YC<Subscript>6</Subscript>H<Subscript>4</Subscript>C(O)X compounds

Mechanistic aspects of the effect of the X and Y substituents (X = Me, H, CF₃, CN, Br, Cl, F, OH, NH₂; Y = H, NMe₂, NH₂, CN, NO₂) on the carbonyl bond in 4-YC₆H₄C(O)X compounds are discussed on the basis of the ¹³C and ¹⁷O NMR data.     

Protonation of 3-Arylpropynoic Acid Derivatives in Superacids

According to the ¹H and ¹³C NMR data, 3-arylpropynoic acids and their esters XC₆H _n -C≡C-CO₂R (R = H, Me, Et) having electron-withdrawing substituents in the benzene ring (X = NO₂, CN, COMe, CO₂Me) exist in HSO₃F at ?80 to 0°C as XC₆H _n -C≡C-C⁺(OH)OR ions. Derivatives with other substituents (X = H, F, Me, MeO) in HSO₃F or CF₃SO₃H above ?40°C undergo protonation at the acetylenic carbon atom neighboring to the acid group to give unstable vinyl-type XC₆H _n -C⁺=CH-CO₂R cations which are then transformed into mixtures of stereoisomeric (Z and E) fluorosulfonates or triflluoromethanesulfonates XC₆H _n -CY=CH-CO₂R (Y = OSO₂F, OSO₂CF₃), the E isomer prevailing.     

A New Transition Metal Tetracyanidoborate: Synthesis,Structure and Properties of Co[B(CN)4]2·2H2O

The reaction of tetracyanidoboronic acid, H[B(CN)₄], with CoCO₃ or Co(OH)₂ in aqueous solution leads after slow evaporation of water to single crystals of Co[B(CN)₄]₂ · 2H₂O. The compound has been characterized by single crystal X‐ray diffraction ( , a = 12.2922(9), c = 9.2235(7) Å, Z = 4). The Co²⁺ ion is octahedrally coordinated by four nitrogen atoms of four different tetracyanidoborate CN groups occupying the four equatorial positions and two molecules of water occupying the remaining corners of the octahedron. The single crystal X‐ray structure, the vibrational spectra, and the thermal properties are compared with other known tetracyanidoborates with divalent cations.     

The effect of polar substituents on the heterocyclic benzoxazoles

The synthesis, characterization, and mesomorphic properties of a new type of heterocyclic compounds 1, 2 derived from benzoxazole are reported. In order to understand the relationship between the structure and the mesomorphic behavior, compounds containing a variety of polar substituents (i.e., X=H, F, Cl, Br, CH₃, CF₃, OCH₃, NO₂, CN, OH, NMe₂, COOCH₃) on the terminal end were prepared. The phase behavior of these mesogenic compounds was characterized and studied by differential scanning calorimetry (DSC) and polarization optical microscopy. The formation of mesophases was strongly dependent on the electronic and/or the steric factors of the substituents. In general, a mesophase was better induced by introduction of a polar substituent. Compounds (X=H) formed a crystalline phase, however, other compounds, except for X=OH, exhibited nematic or smectic A phases. Interestingly all compounds with electron-donating substituents (X=CH₃, OCH₃, NMe₂) exhibited nematic phases, however, other compounds with electron-withdrawing substituents (X=F, Cl, Br, CF₃, NO₂, CN, COOCH₃) formed smectic A phases. Compounds (X=NO₂, CN, COOCH₃) have higher clearing temperatures than those of other homologues, and the higher T_cl was attributed to an enhanced conjugative interaction. However, no linear correlation between the clearing temperature or the temperature range of mesophases with Hammett σ_p constants was found. The fluorescent properties of the compounds were examined. All λ_max peaks of the absorption and photoluminescence spectra of compounds occurred at ca. 348-381 and 389-478 nm, respectively. Whereas, the quantum yields of some compounds were relatively low.     

Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. III. Preparation and solution studies of complexes [MX(1)] (M = Cu,Ag and Au; X = anionic ligand; 1 = 2, 11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene)

The preparation of monomeric complexes [MX( 1 )] is reported where M = Cu, Ag, Au; X = I, Cl, NO₃, BF₄ and 1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene. The solution structure of the complexes is discussed on the basis of molecular weight, conductivity and NMR. measurements. In acetonitrile and nitromethane, the nitrate and fluoroborate complexes exist as ionic species [M( 1 )]⁺X^? whereas the halo-complexes are present as equilibrium mixtures of ‘covalent’ and ‘ionic’ forms. All the complexes are associated in CH₂Cl₂-solutions. The values of ¹J show that this association in [Ag(NO₃) ( 1 )] and [Ag(BF₄) ( 1 )] is best described in terms of ion-pairing while that for species [AgX( 1 )] (X = Cl, Br and I) is mainly ‘covalent’ in nature. Evidence is presented for the formation of the complex ion [Ag(CH₃CN)_n( 1 )]⁺ in acetonitrile solution.     

Addition of Benzodioxahalogenophosphoranes to the Carbonyl Group: New Phosphoranes and their Reactivity

Abstract

Halogenophosphoranes catPX₃ (X = C1, Br) (3), catPBr₂Y [Y = CHF₂CF₂CH₂(4), F(5), OCH=CBr₂ (6), CN (7), cat = C₆H₄O₂-o] react with aldehydes containing electron-withdrawing groups (CZ₃CHO, Z = C1, Br) in solvent to form the products of insertion in P-X bond. The structure of compounds (12–15) and their diastereomeric composition were determined by the NMR ¹H, ¹³C, and ³¹P spectroscopy. Phosphoranes (8–11) disproportionate to PX₃ and cat₂POCHXCZ₃ (X, 2 = Br, Br; C1, Br) (16, 17). Dibromophosphoranes (4–7) and monobromophosphorane (3) are also added to the carbonyl group of CZ₃CHO to form unsymmetric P(V) derivatives catPBr(OCHBrCZ₃)Y (18, 19) and (16, 17, 20–25). The thermal behaviour of compounds (18, 19) was investigated.     

Theoretical study of substituent effects on the acidity of the methyl group: Structure of anions CH2X−

Geometries have been optimized using molecular-orbital calculations (a) with a 4-31G Gaussian basis set for carbanions CH₂X^? where X = H, CH₃, NH₂, OH, F, C?CH, CH?CH₂, CHO, COCH₃, CN, and NO₂; and (b) with an STO -3G basis set for methyl acetate and acetyl deprotonated methyl acetate. All the carbanions containing unsaturated substituents are planar, with a considerable shortening of the C? X bond. Carbanions containing saturated substituents are pyramidal with the out-of-plane angle α increasing with the electronegativity of the substituent. Double-zeta basis set calculations give proton affinities over the range 449 (for CH₃CH₂^?) to 355 kcal/mol (for CH₂NO₂^?), with all unsaturated anions having smaller affinities than saturated anions. The correlation of proton affinities with 1s binding energies, and with charges on both the carbon of the anion and on the acidic proton of the neutral molecule are examined.     

Trans influence and charge transfer transitions X → Co in cobalt (III) complexes of the type trans [CO(en)2XY]z

The energies of the CT transitiopns X → Co have been measured for a series of compounds of the type trans [CO(en)₂XY]^+z, with X = Cl, Br and Y = Cl, Br, NH₃, OH, NCS, No₂, SO₃, CN. They depend upon the nature of the Yl igand. Values of the optical electronegativity of the CO d_z2 orbitals have been calculated, showing that the covalent character of the CoX bond increases in the following order of the Y ligands: NCS ≈ NH₃ ≈CN < OH < NO₂ < Cl ≈ Br < SO₃. This result is discussed along with the variations of the Co bonding forces.     

Determination of configuration of products of nucleophilic addition to activated acetylenes by the NMR method

Conclusions It was shown that the stereospecificity of SSCC³ _C,H ^trans > ³J _C,H ^cis is applicable as a configurational test for di- and trisubstituted alkenes R₂E(Y)C=C(X)H with various heteroatomic substituents (E=N, P, S) and activating groups (X=CO₂Alk, CN at Y=H, and X=Y=CO₂Alk, CN, CF₃).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 779–783, April, 1988.     

Hammett and Brown correlations in the structure and electronic properties of H2Si=SiHAr (Ar = p-C6H4X; X = NH2, OH,Me, H,F, Cl,CHO, COOH,CN, NO2) molecules

Substituent effect on the structure and electronic properties of H₂Si=SiHAr (Ar = p-C₆H₄X; X = NH₂, OH, Me, H, F, Cl, CHO, COOH, CN, NO₂) molecules are studied at the CAM-B3LYP/6-311G(d,p) level of theory. Energy decomposition analysis (EDA) is used as a useful tool for illustrating the interaction between H₂Si and SiHAr fragments in HArSi=SiH₂ molecules. Energetic analysis reveals that the singlet state of the fragments is more stable than triplet state. Also, interactions are stronger in the presence of electron-withdrawing groups (EWGs) in comparison to electron donating groups (EDGs). EDG and EDG effects are investigated on the stability of fragments, frontier orbital energy, distortion, HOMO–LUMO gap, electron-donating (ω⁻) and electron-accepting (ω⁺) powers of the studied molecules. Then, the correlations between these calculated parameters with the Hammett and Brown constants (σ_p and σ_p⁺, respectively) are provided. Also, time-dependent density functional theory method (TD-DFT) is employed for the determination of the strongest absorption band values (λ_max,el) of these molecules. This absorption band is attributed to the HOMO →LUMO transition.     

Formation of charge-transfer complexes in systems containing substituted aromatic hydrocarbons and electron-donating organic compounds

Binary systems of monosubstituted benzene derivatives of type C₆H₅X (X=CN, NO₂, COMe, F, Cl, Br, I) and furan, pyrrole, thiophene, pyridine, tetrahydrofuran, and piperidine are analyzed physicochemically by a refractometric method.From deviations from additivity of n (V) isotherms for systems containing furan plus C₆H₅CN, C₆H₅NO₂, or C₆H₅COMe, conclusions can be drawn about interactions of components leading to formation of charge-transfer complexes (CTC) of 21 composition.With pyrrole possible intermolecular interaction must be confirmed by other methods of physicochemical analysis.Almost all of the systems containing tetrahydrofuran investigated, differ by showing more marked interaction between the components, giving CTC of 11 composition.n (V) isotherms for systems containing pyridine and C₆H₅NO₂ are slightly concave to the composition axis. At the same time piperidine clearly reacts with C₆H₅CN and C₆H₅NO₂, giving a 21 complex with the former, and a colored mixture with the latter, (formation of a complex in this case requires confirmation by other methods).All the thiophene binary systems investigated are characterized by linear refractive index isotherms, i.e., they are refractometrically ideal.The electron-donor properties of the heterocyclic compounds investigated vis a vis the aromatic ring with a lowered-electron density lie in the order tetrahydrofuran > furan > piperidine > pyrrole > thiophene.For Part III see [6].     

Regioselectivity in the reactions of the acetonate ion with electron-deficient arenes

The reactions of the acetonate ion with 1,3-dinitro-5-X-, 1,3-X₂-5-nitro- (X = NO₂, CN, COOCH₃, CONH₂, COO^–, and H), and 1,3,5-tricyanobenzenes were studied by ¹H NMR and electronic absorption spectroscopy and by quantum-chemical methods. The kinetic factor is decisive for the initial attack of the carbanion on the C(2) atom of unsymmetrical arenes. However, -adducts in which a nucleophile is added to the C(4) atom are more stable thermodynamically. In the case of 1,3-X₂-5-nitrobenzenes (X = CN, COOCH₃, or CONH₂), the -adducts with the acetonate group in para-position to the X group unexpectedly proved to be very stable. The structures of the -adducts based on trinitro- and 1,3-dinitro-5-cyanobenzenes were determined by X-ray diffraction analysis. Quantum-chemical calculations (the AM1 and PM3 semiempirical methods and the density functional method) were used to interpret the reaction regioselectivity and the molecular and electronic structures of the -adducts.     

Theoretical study of the gas‐phase SN2 reactions of X− with CH3OY (X,Y = Cl,Br, I)

The gas‐phase nucleophilic substitution reactions at saturated oxygen X^? + CH₃OY (X, Y = Cl, Br, I) have been investigated at the level of CCSD(T)/6‐311+G(2df,p)//B3LYP/6‐311+G(2df,p). The calculated results indicate that X^? preferably attacks oxygen atom of CH₃OY via a S_N2 pathway. The central barriers and overall barriers are respectively in good agreement with both the predictions of Marcus equation and its modification, respectively. Central barrier heights (ΔH and ΔH) correlate well with the charges (Q) of the leaving groups (Y), Wiberg bond orders (BO) and the elongation of the bonds (O? Y and O? X) in the transition structures. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A spectroscopic study of cobalt(III) furyldioximates

Summary The electronic properties of a series of cobalt(III)trans-furyldioximato-complexes of the type [CoB(FH)₂X] (B=NH₃, X=Cl, Br, I or NO₂; B=pyridine (py) or thiocarbamide (thio), X=Cl or Br; B=imidazole (imid), X=Br), [Co(FH₂)(FH)Cl₂] and [Co(thio)₂(FH)₂]NO₃ were studied by i.r., u.v. and¹H and¹³C n.m.r. spectra The results were compared with those from the corresponding dimethylglyoximato-complexes. It was concluded that -conjugation over the equatorial plane in the furyldioximates is greater than in the dimethylglyoximates. There is some evidence of thetrans-influence of the anionic ligands in the ammines which are in the order NO ₂ ^– >Br^–>Cl^–.     

The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

Two homologous series of 4-alkoxyphenylazo 4?-(2?- (and 3?-) methyl-) 4?-substituted benzoates (IIn_a–f and IIIn_a–f, six series each) were prepared and investigated. Within each series, the length of the terminal alkoxy group varies among 6, 8, 10 and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changes between the electron-donating CH₃O, CH₃, and the electron-withdrawing Br, NO₂ and CN groups, in addition to the un-substituted analogue, X = H, aiming to investigate the effect of the different orientations of the methyl groups substituted on the central benzene ring, on the mesophase behaviour. The mesomorphic properties were discussed in terms of steric and polarisability effects. The mesophase stability was correlated with the polarisability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the prepared isomers with each other and with the previously investigated laterally neat analogues 4-(4?-alkoxyphenylazo) phenyl 4?-substituted benzoates (In_a–f).     

Gas-phase electrophilic addition reactions of chlorinated alkyl ions

Chemical ionization was used to study gas-phase electrophilic addition reactions of chloromethyl ions ([CH_xCl_3-x]⁺, x = 0, 1, 2) with a number of substituted benzenes (C₆H₅Y, Y = NH₂, OH, CHO, CN, NO₂). Mass-analyzed ion kinetic energy spectrometry was used to characterize the reaction products with respect to the site of electrophilic addition (ring v. substituent). In some cases, examination of secondary reaction products (ion–molecule adduct which has undergone an elimination reaction in the ion source) aided in establishing the original site of electrophilic addition. Aniline, benzonitrile and nitrobenzene exhibited preferential substituent interaction, while phenol and benzaldehyde gave a mixture of ring and substituent reaction products. These gas-phase results differ considerably from solution-phase Friedel–Crafts alkylation; however, they are consistent with the notion of preferential σ-bond formation at polarizable centers of negative charge.     

Linear dependence of the intensity of the [M + H]+ ion peak in fast atom bombardment mass spectrometry on the basicity of meso-substituted octaethylporphyrins

A fast atom bombardment mass spectrometric study of the meso-substituent effect of Octaethylporphyrins (OEPX, X = NH₂, CH₃, H, CHO, Cl, CN, NO₂) is reported. The intensity of the [M + H]⁺ ion peaks was estimated quantitatively using an external standard, which was observed to be correlated linearly with the basicity (pK₃) of the OEPX. The pK₃ value of the OEPXs was obtained by titration with perchloric acid and it was observed to be correlated linearly with Hammett's σ_p value, with a ρ value of 1.38.