The phase-dependent photochemical reaction dynamics of halooxides and nitrosyl halides

Recent progress in understanding the phase-dependent reactivity of halooxides and nitrosyl halides is outlined. Halooxide reactivity is represented by the photochemistry of chlorine dioxide (OClO) and dichlorine monoxide (ClOCl). The gas phase photochemical dynamics of OClO are contrasted with the dynamics in condensed environments. The role of excited-state symmetry in defining the reaction dynamics and the observation of photoisomerization resulting in the production of ClOO are discussed. The current understanding of the excited-state reaction dynamics of ClOCl and evidence for photoisomerization of this species resulting in the production of ClClO are outlined. Finally, the photochemical reaction dynamics of the nitrosyl halide ClNO are presented. The main difference between the gas and condensed phase reaction dynamics of this species is that whereas photodissociation to form Cl and NO dominates the gas phase reaction dynamics, photoisomerization resulting in ClON production occurs to an appreciable extent in condensed environments. The observation of photoisomerization for OClO, ClOCl and ClNO suggests that this process is a general feature of the condensed phase reaction dynamics for smaller halooxides and nitrosyl halides. Finally, future areas for study in both halooxide and nitrosyl halide photoreactivity are outlined.     

Reactions of silicon atoms with methane and silane in solid argon: a matrix-spectroscopic study

The reaction of silicon atoms with methane (1) and silane (7) in argon at 10 K has been studied. Methane (1) is found to be inert to silicon atoms, but reaction occurs upon photochemical excitation under formation of methylsilylene (2). On the contrary, silane (7) is spontaneously converted into a mixture of silylsilylene (10) and disilene (12). Subsequent irradiation generates the butterfly-type disilyne Si(2)H(2) (14), together with a third photoproduct, which we assume to be the doubly bridged Si(2)H(4) isomer 13. The structural elucidation of the new species is based on the comparison of the experimental IR and UV/Vis spectra with data from density functional theory calculations. The results are supported by isotopic labeling studies.     

RuCl3·3H2O Mediated Olefin Isomerizations in Ionic Liquids: A Highly Recyclable System for Olefin Isomerizations

Herein lies a convenient and highly efficient method of olefin isomerization in the presence of RuCl₃·3H₂O in ionic liquid(IL). More importantly, RuCl₃·3H₂O is a robust and recyclable catalyst. Nine cycles of RuCl₃·3H₂O as the catalyst were performed for the isomerization reactions of the selected substrate in IL and MeOH.     

Computational study of hydrogen bonding interaction between formamide and nitrosyl hydride

The hydrogen bonding interaction of formamide–nitrosyl hydride complex has been investigated using density functional theory (DFT) and ab initio method. The natural bond orbital (NBO) analysis and atom in molecules (AIM) theory were applied to understand the nature of the interaction. Two stable geometries are found on the potential energy surface, a six-membered cyclic structure of complex A and a seven-membered cyclic structure of complex B, characterized by AIM analysis. Complex A is less stable than complex B. It is confirmed that there are contractions of CH (compared with the monomer HCONH₂), NH bonds (compared with the monomer HNO) and the corresponding stretching vibrational frequencies are blue-shifted, while there is an elongation of the NH bond and the corresponding stretching vibrational frequency is red-shifted, relative to those of the monomer HCONH₂. From NBO analysis, it is evident that the electron densities in the σ^* (CH) and σ^*(NH) of the complex A are less than those of the monomers HCONH₂ and HNO, which strengthen CH and NH bonds. Furthermore, the increases in s-characters of X also strengthen XH bonds.     

Electron affinities of heavier phosphoryl and thiophosphoryl halides APX3 (A = O, S and X = Br, I)

We carried out computational studies of OPX₃ and SPX₃ (X = Br and I) molecules and their corresponding anions using density functional theory, Møller‐Plesset, and CCSD(T) methods with newly developed model core potentials (MCP). Reliabilities of the MCP were demonstrated by comparing experimental and calculated results. We computed the geometric structure, electron affinities, and electrostatic moments using systematic sequences of the dzp‐, tzp‐, and qzp‐quality basis sets. Both C_3v and C_s symmetries were assumed to ascertain that minima on the potential energy surface were found. Infrared and Raman frequencies were calculated and compared with available experimental data. Natural population analyses were performed and used to determine distribution of the extra electron in anions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007     

Comprehensive study of the interaction between hydrogen halides and methanol derivatives

The R? CH₂? HO…H? X (R = SCl, Cl, SH, NO₂, OMe, CHO, CN, C₂H₅, CH₃, H; X = F, Cl, Br) complexes are considered here as the interest sample for the consideration of different measures of H‐bond strength. The intermolecular interaction energies are predicted by using MP2/6‐31++G(d,p) and B3LYP/6‐31++G(d,p) methods with basis set superposition error and zero‐point energy corrections. The results showed that intermolecular hydrogen bonds for complexes with HF are stronger than such interactions in complexes with HCl and HBr. Quantum theory of “Atoms in Molecules” and natural bond orbitals method were applied to analyzed H‐bond interactions. The gas phase thermodynamic properties of complexes were predicted using quantum mechanical computations. The obtained results showed a strong influence of the R and X substituents on the thermodynamic properties of complexes. Numerous correlations between topological, geometrical, thermodynamic properties and energetic parameters were also found. © 2011 Wiley Periodicals, Inc.     

An ESR study on the reaction between dicarbonyl titanocene and aryl-tin halides

The oxidation elimination reaction between dicarbonyl titanocene and aryltin halides was studied by means of paramagnetic resonance spectroscopy. The radical intermediates containing Ti(III) were discovered from the ESR spectra to be (Cp₂TiSnAr_nX_3-n), Cp₂Ti(CO)X, and Cp₂TiX, and a radical mechanism for the reaction is proposed. © 1996 John Wiley & Sons, Inc.     

Different orientations of C=O versus P=O in P(O)NHC(O) skeleton: the first study on an aliphatic diazaphosphorinane with a gauche orientation

Different orientations of P(O) versus C(O) in P(O)NHC(O) skeleton have been discussed in two new phosphorus(V)-nitrogen compounds with formula XP(O)Y and XP(O)Z₂ where X = NHC(O)C₆H₄(4-F) and Y = NHCH₂C(CH₃)₂CH₂NH (1), Z = NHC₆H₄(4-CH₃) (2). Compound 1 is the first example of an aliphatic diazaphosphorinane with a gauche orientation which has been studied by X-ray crystallography; the P=O bond is in the equatorial position of the ring. Both compounds show ⁿ J(F,C) and ^m J(F,H) coupling constants (n = 1, 2, 3 and 4; m = 3 and 4) and ³ J(P,C) > ² J(P,C). Quantum chemical calculations were performed with HF and Density Functional Theory (DFT) methods using 6−31+G(d,p) basis set. A tentative assignment of the observed vibrational bands for these molecules is discussed. Compound 1 shows a deshielded C atom of the carbonyl moiety (in ¹³C NMR spectrum) relative to that of 2, which is supported by IR spectroscopy in which the considerably lower C=O frequency is observed for 1. Comparing the X-ray crystallography and IR spectra of 1 and 2 shows that the acyclic compound 2, containing P=O and C=O bonds in an anti position, are involving in a stronger N–H···O=P hydrogen bond in crystal network. This leads to a weaker P=O and N_C(O)NHP(O)–H bonds and stronger N···O interaction. The N_amide–H is involved in an intramolecular N–H···O hydrogen bond.     

The gas-phase reaction between O3 and HO radical: a theoretical study.

We report a theoretical study on the reaction of ozone with hydroxyl radical, which is important in the chemistry of the atmosphere and in particular participates in stratospheric ozone destruction. The reaction is a complex process that involves, in the first stage, a pre-reactive hydrogen-bonded complex (C1), which is formed previous to two transition states (TS1 and TS2) involving the addition of the hydroxyl radical to ozone, and leads to the formation of HO4 polyoxide radical before the release of the products HO2 and O2. The reaction is computed to be exothermic by 42.72 kcal mol(-1), which compares quite well with the experimental estimate, and the energy barriers of TS1 and TS2 with respect to C1 are computed to be 1.80 and 2.26 kcal mol(-1) at 0 K. A kinetic study based on the variational transition state theory (VTST) predicts a rate constant, at 298 K, of 7.37 x 10(-14) cm3 molecule(-1) s(-1), compared to the experimentally recommended value of 7.25 x 10(-14) cm3 molecule(-1) s(-1).     

Formation of N2O from a nickel nitrosyl: isolation of the cis-[N2O2]2- intermediate

Addition of 2,2'-bipyridine (bipy) to [Ni(NO)(bipy)][PF(6)] (1) results in formation of a rare five-coordinate nickel nitrosyl [Ni(NO)(bipy)(2)][PF(6)] (2). This complex exhibits a bent NO(-) ligand in the solid state. On standing in acetonitrile, 2 furnishes the NO coupled product, [Ni(κ(2)-O(2)N(2))(bipy)] (8) in moderate yield. Subsequent addition of 2 equiv of acetylacetone (H(acac)) to 8 results in formation of [Ni(acac)(2)(bipy)], N(2)O, and H(2)O. Preliminary mechanistic studies suggest that the N-N bond is formed via a bimetallic coupling reaction of two NO(-) ligands.     

Structure and bonding of three-coordinate N-heterocyclic carbene nickel nitrosyl complexes: Theoretical study

The structure and bonding of the for C₃N₃H₂X₂Ni(Cp)NO (X = H, F, Cl, Br) and their linkage isomers C₃N₃H₂X₂Ni(Cp)ON has been studied by carrying out density functional theory. The bonding nature of NiC bonds has been further explored by means of AIM method and natural bond orbital (NBO) analysis. Nucleus-independent chemical shift (NICS) values calculated at several points above ring center indicate aromaticity of heterocyclic cycle. Also, the effect of substitution (X = F, Cl, Br, CN) in N-heterocyclic carbene on the properties of complex has been shown.     

碱金属卤化物与NaA分子筛之间的固态离子交换反应

在低于碱金属卤化物熔点的温度下热处理碱金属卤化物和脱水NaA分子筛干混样品时,一部分分散到分子筛内孔的金属离子能够与脱水分子筛进行程度不同的固态离子交换反应,生成的非挥发性NaCl产物将扩散到分子筛笼外单独结晶或剩余的原卤化物形成溶体.热处理温度愈度,离子交换度愈大;在一定温度下热处理干混样品,存在最大离子交换度.     

Absorption spectra of ground-state and low-lying electronic States of copper nitrosyl: a rare gas matrix isolation study

The reaction of ground-state Cu atoms with NO during condensation in solid argon, neon, and binary argon/neon mixtures has been reinvestigated. In addition to the ground-state already characterized in rare gas matrixes by its nu1 mode in reactions of laser-ablated Cu with nitric oxide, another very low lying electronic state is observed for CuNO in solid argon. Photoconversion and equilibrium processes are observed between the two lowest lying electronic states following photoexcitations to second and third excited states in the visible and near-infrared. The electronic spectrum of the CuNO complex was also recorded to understand the photoconversion processes. In solid neon, only the ground state (probably 1A') and the second and third excited states are observed. This suggests that interaction with the argon cage stabilizes the triplet state to make 1A' and 3A' ' states almost isoenergetic in solid argon. On the basis of previous predictions founded on DFT calculations on the very low lying 1A' and 3A' ', a mechanism is proposed, involving the singlet-triplet state manifolds. For these two lower and one higher electronic states, 14N/15N, 16O/18O, and 63Cu/65Cu isotopic data on nu1, nu2, and nu3 have been measured. On the basis of harmonic force-field calculations and relative intensities in the vibronic progressions, some structural parameters are estimated. The molecule is bent in all electronic states, with Cu-N-O bond angles varying slightly around 130 +/- 10 degrees , but the Cu-N bond force constants are substantially different, denoting larger differences in bond lengths.     

Metal nitrosyl reactivity: Acetonitrile-promoted insertion of an alkylidene into a nitrosyl ligand with fission of the NO bond

Treatment of the complexes [Re(NO)2(PR3)2][BAr(F)4] (R = Cy, 1 a; R = iPr, 1 b) with phenyldiazomethane gave the cationic benzylidene species [Re{CH(C6H5)}(NO)2(PR3)2][BAr(F)4] (2 a and 2 b) in good yields. Upon reaction of 2 a and 2 b with acetonitrile, the consecutive formation of [Re(N[triple bond]CCH3)(N[triple bond]CPh)(NO)(OC(CH3)=NH)(PR3)][BAr(F)4] (3 a and 3 b) and [Re(NCCH3)(OC{CH3}NH{C6H5})(NO)(PR3)2][BAr(F)4] (4 a and 4 b) was observed. The proposed reaction sequence involves the coupling of coordinated NO, carbene and acetonitrile molecules to yield the (1Z)-N-[imino(phenyl)methyl]ethanimidate ligand. The coupling of the nitrosyl and the benzylidene is anticipated to occur first, forming an oximate species. The subsequent acetonitrile addition can be envisaged as a heteroene reaction of the oximate and the acetonitrile ligand yielding 3 a and 3 b, which in turn can cyclise and undergo a prototropic shift initiated by an internal attack of the ethaneimidate ligand on the benzonitrile moiety to afford 4 a and 4 b.     

Isomerizations of CH3SO2: Quantum Chemistry and Topological Study

The structures, stabilities and the isomerization reactions of CH₃SO₂ isomers in a doublet electronic state have been studied at B3LYP/6‐311+ +G (d,p), MP2/6‐311++G (d,p) and CCSD(T)/6‐311++G (d,p) levels. The three different levels of calculation give the similar results: thirteen minimum isomers were located and they were connected by eleven transition states. Among the thirteen isomers, cis‐CH₃OSO, trans‐CH₃OSO and CH₃SO₂ are the most stable species, and they should be detected easily in experiment. This is well consistent with the experimental result. These isomers could isomerize to each other by chemical bond vibration, chemical bond rotation and atom migration. The non‐planar ring structure transition state (STS), which was found in this paper, extended the concept of ring STS to the non‐planar systems.     

A study of equilibrium between cadmium cyanide and alkali halides and thiocyanate by solubility measurements

Summary A study of the Cd(CN)₂ +x X^– [Cd(CN)₂X _x ] ^x– equilibrium (where X = Cl, Br or CNS) has been carried out at 18° and 38° by measuring the solubility of cadmium cyanide in potassium chloride, bromide and thiocyanate at various concentrations, and at a high ionic strength (6 M) maintained with sodium perchlorate to minimise the effect of activity coefficients. Equilibrium constants forx = 1 and 2 have been calculated and clearly favour the situation wherex = 1. H values for the dissociation of [Cd(CN)₂X]^– have also been calculated.