Infrared spectra of X-.CO(2).Ar cluster anions (X=Cl,Br,I)

Ion-molecule clusters of the heavier halide anions X-.CO(2) (X=Cl-,Br-,I-) with CO2 have been studied by gas phase infrared photodissociation spectroscopy, using Ar evaporation from the complexes X-.CO2.Ar upon infrared excitation. We observe that the asymmetric stretch vibrational mode of the CO(2) molecule is red-shifted from the frequency of free CO2, with the red-shift increasing toward the lighter halide ions. A similar trend is repeated in the region of the Fermi resonance of the combination bands of the asymmetric stretch vibration with two quanta of the bending vibration and the symmetric stretch vibration. We discuss our findings in the framework of ab initio and density functional theory calculations.     

The heI photoelectron spectra of the halogen azides,XN3(X = Cl and Br) and the halogen isocyanates,XNCO(X = Cl,Br and I)

High yield routes to the unstable halogen azides and isocyanates have permitted vacuum ultraviolet photoelectron spectra to be obtained for the chlorine and bromine azides, and the chlorine, bromine and iodine isocyanates. The results are compared with ab initio and semi-empirical calculations, leading to a reassignment of the photoelectron spectra of the parent acids, HN₃ and HNCO in the high energy region. The halogen azide and isocyanate photoelectron spectra provide an interesting investigation into how the orbitals of a linear pseudohalide grouping are perturbed by an off-azis halogen atom. A photoelectron spectrum for the unknown molecule FNCO is predicted.     

Single-crystal absorption spectra of CsVX3 (X = Cl,Br, I)

Polarized single-crystal absorption spectra of CsVCl₃, CsVBr₃ and CsVI₃ have been measured between 5000 and 30000 cm^?1 at temperatures ranging from 6 to 273 K. Spin-allowed transitions arise through a vibronic single-ion mechanism. Spin-forbidden transitions are strongly enhanced through an exchange intensity mechanism.     

He I photoelectron spectra and valence synchrotron photoionization for XC(O)SCl (X = F, Cl) compounds

Small penta-atomic molecules like FC(O)SCl and ClC(O)SCl have been analyzed by using both photoelectron spectroscopy (PES) and results derived from the use of synchrotron radiation in the same energy range. For this second experiment total ion yield (TIY), photoelectron photoion coincidence (PEPICO), and partial ion yield (PIY) spectra have been recorded. This set of data together with results obtained by computational chemistry allow us to study electronic properties and the ionization channels of both species. Thus, whereas the photodissociation behavior of FC(O)SCl can be divided into three well-defined energy regions, the fragmentation dynamics of ClC(O)SCl seems to be more complex. Nevertheless, simultaneous evaluation of the PES and valence synchrotron photoionization studies helps to clarify the molecular ionization processes.     

Theoretical calculation of the photodetachment spectra of XAuY- (X, Y = Cl, Br, and I)

The photodetachment spectra of the title molecules have been calculated, taking electron correlation and spin-orbit coupling into account and employing improved relativistic effective core potentials for gold and the halogen atoms. The calculated spectra have been compared with existing experimental spectra. The spin-orbit splitting of several degenerate electronic states has been calculated. The composition of the spin-orbit eigenstates are analyzed in terms of scalar relativistic electronic states. A comparison of the relative position of peaks in the calculated photodetachment spectra of the title molecules has been made.     

Theoretical study of valance photoelectron spectra of hypoxanthine, xanthine, and caffeine using direct symmetry-adapted cluster/configuration interaction methodology

UV photoelectron spectra of hypoxanthine, xanthine, and caffeine, up to 20 eV, were calculated and compared with the experimental spectra reported in literature. The calculations were performed using a novel version of the quantum mechanical symmetry-adapted cluster/configuration interaction (SAC-CI) method termed, direct SAC-CI. The Duning/Huzinaga valance double-zeta D95+(d,p) Gaussian basis set was also employed with this method. The ionization energies and intensities were calculated, and the corresponding spectral bands were assigned. Natural bonding orbital (NBO) calculations were employed for better spectral band assignment. The calculated ionization energies and intensities reasonably produced the experimental photoelectron spectra.     

Vibrational spectra of the trihalocyclopropenium ions [C3X3]+ (X = Cl,Br or I)

Vibrational spectra are reported and assigned for the planar D_3h symmetry cyclopropenium cations [C₃X₃]⁺ (X= Cl, Br or I) from investigations of the compounds C₃Cl₃AlCl₄, C₃Cl₃GaCl₄, C₃Cl₃FeCl₄, C₃Cl₃SbCl₆, C₃Br₃AlBr₄ and C₃l₄, using conventional infrared and Raman spectroscopy and Fourier transform Raman spectroscopy. The symmetric C—X stretching modes of [C₃X₃]⁺ occur at 458, 269 and 180 cm⁻¹ and the ring-breathing modes at 1790, 1732 and ca. 1650 cm⁻¹ in [C₃Cl₃]⁺, [C₃Br₃]⁺ and [C₃I₃]⁺, respectively. A normal coordinate calculation is performed for [C₃Cl₃]⁺.     

Theoretical study of structure, stability and infrared spectra of CH3X-SO3 (X = F, Cl, Br) complexes

Ab initio computational study of the electronic structure and infrared spectra of donor-acceptor complexes formed between SO3 and CH3X (X = F, Cl, Br) molecules was carried out at the MP2(full)/6-31G(d) level of theory. The calculated complexation energy at G2MP2 level shows that stability of complexes decrease, as CH3Cl-SO3 > CH3Br-SO3 > CH3F-SO3. The NBO partitioning scheme show that the lengthening of the C-F, C-Cl, and C-Br bond lengths, upon complexation, is due to an decreasing "s" character in these bonds.     

C6F5X＋（X=Cl,Br,I,CH3）离子的理论研究

用DFT B3LYP方法及6-311G（d,p）,6-311＋G（d,p）和LanL2dz基组,对C6F5X＋（X=Cl,Br,I,CH3）阳离子做了理论研究,优化了它们的电子基态的构型,计算了对应分子的垂直电离势（VIP）和绝热电离势（AIP）.结果表明四种离子的构型的对称点群和对应分子相同,但构型参数有明显差别.B...     

The reactions of K2ReX6 (X = Br OR I) and Re3X9 (X = Cl,Br OR I) with alkyl and aryl isocyanides

The reactions of alkyl isocyanides (RNC) and aryl isocyanides (ArNC) with the rhenium halides K₂ReX₆ (X = Br or I) and Re₃X₉ (X = Cl, Br or I) have been investigated. When the K₂Rex₆ salts are treated with neat isocyanide at room temperature, or with isocyanide ligands in polar solvents under reflux conditions, then the homoleptic isocyanide cations [Re(CNR)₆]⁺ or [Re(CNAr)₆]⁺, are isolated. Under less forcing conditions, various rhenium(III) and rhenium(I) species, e.g. [Re(CNCMe₃)₅I₂]⁺ and Re(CNAr)₅I, which may be considered as intermediates on the way to the formation of the homoleptic species, can be obtained. The rhenium(I) complexes Re(CNAr)₅I₃, which are believed to contain the coordinated triiodide ligand, have also been isolated and characterized. One route to these complexes is through the reaction of Re(CNAr)₅I with I₂. Reactions of the trinuclear halides Re₃X₉ (X = Cl, Br or I) with alkyl isocyanides at room temperature are found, in all instances, to provide adducts of the type Re₃X₉(CNR)₃. Under reflux conditions, Re₃Cl₉ and Re₃Cl₉(PEtPh₂)₃ react with Me₃CNC to fom products of cluster disruption, viz. [Re(CNCMe₃)₆]⁺ and [Re(CNCMe₃)₄(PEtPh₂)₂]⁺, respectively. The spectroscopic and electrochemical properties of complexes derived in this study are reported. These results are compared with those reported previously by Freni et al.     

Fe+与CH3X（X=Cl,Br,I）反应的理论研究

铁及其复合物催化的C—X键功能化日益引起人们的重视.采用密度泛函理论(DFT),在B3LYP/def2-SVP水平下详细研究了Fe+与CH3X(X=Cl,Br,I)的反应活性和机理.计算结果表明标题反应存在两种反应机制,即插入机制和SN2机制.从机理上来看,在插入机理中,反应都始于Fe+离子从侧面进攻CH3X,生成产物FeX+和CH3;而在SN2机制中,反应则始于Fe+离子从背后进攻CH3X,生成产物3FeCH+和X.从我们的计算可以看出,四重态或六重态下的Fe+离子在C—X键活化中展现了截然不同的催化活性;在所有通道中,都以四重态为主导;SN2机制中相对较高的决速能垒使其丧失了竞争性.再者,计算表明在所有的插入机制中,所有通道都是放热的,而在SN2机制中,仅有X=I时,反应是放热的.此外,计算表明这些反应属于两态反应活性,两种机制中,在反应的入口和出口存在最小能量交叉点.此外,反应途径电子结构追踪分析表明自旋极化对能量影响较大,调控着反应采取的反应通道和主副产物比例.通过本文的理论研究,尤其是详细的电子结构分析,为铁催化剂活化C—X键和C—C耦联反应提供了线索和以铁为基的催化剂设计提供理论依据.     

The syntheses and coordination properties of M(CO)3X(DAB) (M = Mn,Re; X = Cl,Br, I; DAB = 1,4-diazabutadiene)

M(CO)₅X (M = Mn, Re; X = Cl, Br, I) reacts with DAB (1,4-diazabutadiene = R₁N=C(R₂)C(R₂)′=NR′₁) to give M(CO)₃X(DAB). The ¹H, ¹³C NMR and IR spectra indicate that the facial isomer is formed exclusively. A comparison of the ¹³C NMR spectra of M(CO)₃X(DAB) (M = Mn, Re; X = Cl, Br, I; DAB = glyoxalbis-t-butylimine, glyoxyalbisisopropylimine) and the related M(CO)₄DAB complexes (M = Cr, Mo, W) with Fe(CO)₃DAB complexes shows that the charge density on the ligands is comparable in both types of d⁶ metal complexes but is slightly different in the Fe-d⁸ complexes. The effect of the DAB substituents on the carbonyl stretching frequencies is in agreement with the A′(cis) > A″ (cis) > A′(trans) band ordering.Mn(CO)₃Cl(t-BuNCHCHNt-Bu) reacts with AgBF₄ under a CO atmosphere yielding [Mn(CO)₄(t-BuNCHCHN-t-Bu)]BF₄. The cationic complex is isoelectronic with M(CO)₄(t-BuNCHCHNt-Bu) (M = Cr, Mo, W).     

CH3SOCH3与XO(X=Cl,Br)自由基反应的理论研究

采用密度泛函理论B3LYP方法,在6-311 G(d,p)基组水平上研究了二甲亚砜(DMSO)与XO(X=Cl,Br)自由基反应的微观动力学机理,并利用经过wigner校正的传统过渡态理论计算了标题反应在200~2000 K温度范围内的反应速率常数。研究结果表明,DMSO与XO(X=Cl,Br)自由基反应主要有氧转移和抽氢两种反应机理,氧转移反应的能垒显著低于抽氢反应,且前者为放热反应后者为吸热反应;低温时氧转移反应占绝对优势,298 K时DMSO与XO(X=Cl,Br)两个反应体系的总速率常数分别为2.09×10-15和1.75×10-14cm3.molecu le-1.s-1,氧转移反应分支比均为100%。高温时抽氢反应上升为主通道。2000 K时其总速率常数分别为6.32×10-12和8.41×10-12cm3.molecule-1.s-1,抽氢反应分支比分别为91.8%和79.4%。     

卤代氰基卡宾自由基XCCN(X=F,Cl,Br)的理论研究

在C_s对称性和ANO-S基组下, 使用全活化空间自洽场方法(CASSCF), 研究了卤代氰基卡宾自由基及其阴离子的低能电子激发态性质. 为了进一步考虑电子的动态相关效应,采用多组态二级微扰理论(CASPT2)获得更加精确的能量值. 计算结果表明, XCCN的基态是三重态. 单重态和三重态的能隙差ΔE_S-T(kJ/mol): 7.4(FCCN)<13.4(ClCCN)<16.6(BrCCN). 计算得到, XCCN(X=F, Cl, Br)最低垂直激发能分别为408.3, 385.4和 345.2 kJ/mol, 这归因于π(a′) →n_xy 的电子跃迁; XCCN的电子亲和势分别为235.7, 233.0和 237.2 kJ/mol, 与HCCN相比, 其电子亲和势变大.     

Computational study of the reactions of SiH3X (X=H, Cl, Br, I) with HCN

Ab initio calculations were carried out for the reactions of silane and halosilanes (SiH3X, X=H, Cl, Br, I) with HCN. Geometries of the reactants, transition states, intermediates and products were optimized at HF, MP2, and B3LYP levels of theory using the 6-31G(d) and 6-31G(d,p) basis sets. Energies were also obtained using G3MP2 and G3B3 levels of theory. Intrinsic reaction coordinate (IRC) calculations were performed to characterize the transition states on the potential energy surface. It was found that HCN can react with silane and halosilanes via three different mechanisms. One involves HX elimination by a one-step pathway producing SiH3CN. The second mechanism consists of H2 elimination, producing SiH2XCN via a one-step pathway or three multiple-step pathways. The third mechanism involves dissociation of SiH3X to various products, which can then react with HCN. Activation energies, enthalpies, and free energies of activation along with the thermodynamic properties (DeltaE, DeltaH, and DeltaG) of each reaction pathway were calculated. The reaction of SiH3X with HCN produce different products depending on substituent X. We have found that the standard 6-31G(d) bromine basis set gave results which were in better agreement with the G3MP2 results than for the Binning-Curtiss basis set. Computed heats of formation (DeltaHf) for SiH3CN, SiH3NC, SiH2ClCN, SiH2BrCN, SiH2ICN, SiHCl, SiHBr, and SiHI were found to be 133.5, 150.8, -34.4, 23.6, 102.4, 48.7, 127.1, and 179.8 kJ mol-1, respectively. From enthalpies calculated at G3MP2, we predict that the DeltaHf for SiH2 to be 262.8 kJ mol-1 compared to the experimental value of 273.8+/-4.2 kJ mol-1.     

Darstellung von Germanium-Mangan-, Germanium-Rhenium- und Zinn-Rhenium-Clustern des Typs M2(CO)8[μ-EXM(CO)5]2, (M = Mn,E = Ge,X = Br,I; M = Re,E = Ge bzw. Sn,X = I bzw. Cl,Br, I)

Preparation of Germanium-Manganese-, Germanium-Rhenium- and Tin-Rhenium-Clusters of the Type M₂(CO)₈[μ-EXM(CO)₅]₂ (M = Mn, E = Ge, X = Br, I; M = Re, E = Ge or Sn, X = I or Cl, Br, I) The clusters Re₂(CO)₈[μ-SnXRe(CO)₅]₂ are prepared by reaction of Re₂(CO)₁₀ and SnX₂ in a Schlenk-tube under release of pressure (X = Cl, Br, I) or in a sealed glass tube (X = Br, I). As central structural unit a four-membered Re₂Sn₂ ring has to be assumed. This unit can be opened again by reaction with CO under pressure. X₂Sn[Re(CO)₅]₂, which is also formed during the preparation of the clusters in dependance of the CO-pressure, indicates insertion of SnX₂ into the Re—Re bond to be the primary step. The corresponding clusters M₂(CO)₈[μ-GeXM(CO)₅]₂ (M = Mn, X = Br, I; M = Re, X = I) are prepared by reaction of GeI₂ and M₂(CO)₁₀ or of I₂Ge[Mn(CO)₅]₂ and Mn₂(CO)₁₀ or of Br₃GeMn(CO)₅ and BrMn(CO)₅. Ir frequencies of the new clusters are assigned.     

Theoretical study on tetranuclear boron clusters: B4X4 (X = H, F, Cl, Br, I)

The molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4 and B4I4 have been calculated by using all-electron or effective core potential ab initio method at the self-consistent field level using basis sets with diffuse and polarization functions. The boron-boron and boron-halide (-hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three-centered two-electron (3c2e) B-B-B bonds localized on each of the faces of the B4 tetrahedron are derived for B4X4 clusters. The HOMO-LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4 > B4Cl4, B4H4 > B4Br4 > B4I4.     

The matrix-isolated molecular complexes CO/XF (X=Cl,Br,I) and the molecular structure of FC(O)Br

FC(O)Br has been synthesized, and its IR spectrum in the gas phase and isolated in an Ar matrix, as well as, its Raman spectrum in the solid state at -196 degrees C has been analyzed. Its molecular structure has been determined and its UV has been measured. FC(O)Br and FC(O)Cl has been photodissociated in an argon matrix at 17 K with a 193 nm laser. The photolysis produces CO and XF which recombine to form CO/XF complexes. The formation of complexes are followed by the shift of the normal vibration modes with respect to CO and XF isolated in argon matrix. In the case of FC(O)Br, three isomers are identified, OC...BrF, OC...FBr, and CO...BrF, whereas for FC(O)Cl only one isomer is observed, OC...ClF. High level quantum chemical calculations are used to help the assignment of the different isomers.     

[Pd(en)2Pd(en)2X2]4+n(X=Cl,Br,I)链的畸变研究

对一维卤桥过渡金属化合物〔Ｐｄ（ｅｎ）２Ｐｄ（ｅｎ）２Ｘ２〕ｎ＾４＋（Ｘ＝Ｃｌ,Ｂｒ,Ｉ）应用量子化学从头算及ＥＨＴ能带计算进行了研究,发现Ｐｅｉｅｒｌｓ畸变的产生及程度取决于填充轨道能量的降低与核间及电子间相互作用。