Electronic state dependence of the ion-molecule reaction CH(3)CN(+) + CH(3)CN → CH(4)CN(+) + CH(2)CN: threshold electron-secondary ion coincidence (TESICO) and direct ab initio molecular dynamics study

The ion-molecule reaction, CH(3)CN(+) + CH(3)CN → CH(3)CNH(+) + CH(2)CN, has been investigated using the threshold electron-secondary ion coincidence (TESICO) technique. Relative reaction cross sections for two microscopic reaction mechanisms, i.e., proton transfer (PT) from the acetonitrile ion CH(3)CN(+) to neutral acetonitrile CH(3)CN and hydrogen atom abstraction (HA) by CH(3)CN(+) from CH(3)CN, have been determined for two low-lying electronic states, (2)E and (2)A(1) of the CH(3)CN(+) primary ion. The cross section for PT of the (2)A(1) state was smaller than that of the (2)E state, whereas that of HA are almost the same in the two states. Ab initio calculations showed that the dissociation of the C-H(+) bond of CH(3)CN(+) is easier in the (2)E state than that in the (2)A(1) state. The direct ab initio molecular dynamics (MD) calculations showed that two mechanisms, direct proton transfer and complex formation, contribute the reaction dynamics.     

Conformational preferences of RCH2CH2CN (R = CH3, F, Cl) cyanides and their corresponding isocyanides

The structure and relative stability of the different conformers of RCH₂CH₂CN (R = CH₃, F, Cl) cyanides and their corresponding isocyanides have been investigated through the use of high-level ab initio G4 theory as well as B3LYP/aug-cc-pVQZ and M06/aug-cc-pVQZ density functional theory calculations. This theoretical survey ratifies that the gauche conformer of butyronitrile is slightly more stable than the anti one, so that in the gas phase and at room temperature this compound should exist as a mixture of 57 % of the former and 43 % of the latter. Similar stability trends are predicted for the corresponding isocyanide isomer. Conversely, when the terminal methyl group of butyronitrile (or its isocyanide isomer) is replaced by F or Cl, the stability trends are reversed and the anti conformer becomes slightly more stable than the gauche one. These changes in relative stabilities could be traced through an analysis of the reduced density gradient which shows the existence of a stabilizing interaction between the terminal methyl group and the cyano (or isocyano) group in butyronitrile (or its isocyanide isomer), which becomes repulsive when this methyl group is replaced by F or Cl.     

DUAL BEHAVIOR OF ACETONITRILE IN A NEW CADMIUM CYANIDE CLATHRATE: CRYSTAL STRUCTURE OF Cd(CH3CN)2Cd(CN)4·2CH3CN

Abstract

We report a new crystal structure of the title clathrate containing tetrahedral and octahedral Cd atoms in a ratio of 1:1. The preparation of the compound is similar to that of the cristobalite-like clathrate Cd(CN)₂·G, where all Cd atoms are tetrahedral. The new inclusion compound crystallizes in the monoclinic space group C2/c, a = 12.337(4), b = 11.964(3), c = 13.594(3) Å, β = 108.60(2)°, Z = 4, R = 0.034 for 1631 reflections. The three-dimensional host framework is built of alternate linkages between the tetrahedral Cd atom of the tetracyanocadmate and the octahedral Cd atom similar to that of the Hofmann-Td and the en-Td types. In the new clathrate dual behavior of acetonitrile, one as a unidentate ligand in the three-dimensional host framework and the other as the guest in the cage-like cavity, has been demonstrated.     

Intramolecular Rearrangements of >Si(O–C·=O)(CH2–CH3) and >Si(CH2–CH·–CH3)(CH2–CH3) Radicals

Using ESR and IR spectroscopy, the structures of >Si(O–C^·=O)(CH₂–CH₃) (1) and >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) (2) radicals were deciphered. The directions and kinetic parameters of reactions of intramolecular rearrangements in these radicals were determined. The reactions of hydrogen atom abstraction in radical (1) from the CH₂ and CH₃ groups were studied. It was found that the endothermic reaction of hydrogen atom abstraction from the methyl group occurs at a higher rate than the exothermic reaction with the methylene group. The differences are determined by changes in the size of a cyclic transition state. Based on the experimental data, the strengths of separate C–H bonds in surface fragments are compared. The rearrangement >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) >Si(C^·(CH₃)₂)(CH₂–CH₃) was discovered and its mechanism was determined. One of its steps is the skeletal isomerization Si- (2)- _. (1)Si- (1)- _. (2). Experimental data are analyzed using the results of quantum-chemical calculations of model systems.     

Quantum-chemical calculation of spectral characteristics and structure of complexes [Mg(DMF) i (CH3CN)6−i ]2+ and IR spectra of the tricomponent solutions Mg(ClO4)2-DMF-CH3CN

Geometry of complexes [Mg(DMF) _i (CH₃CN)_6?i ]²⁺ (i from 0 to 6) was optimized, IR spectra were calculated, and values of ΔG of the ligand replacement in the cation coordination sphere were estimated by DFT BLYP/6-31G** method. Regularities in variations of spectral and structural characteristics of the complexes at variation in their compositions were elucidated. Quantitative relations between the calculated changes in frequency and intensity of the IR bands ν_C≡N, ν_C-C, ν_C=O, and δ_OCN of the complexes and the respective values in the IR spectra of solutions CH₃CN-Mg(ClO₄)₂-DMF at varying composition of the binary solvent were established. The main regularities in the changes of the DMF ν_C=O band contour in the process of resolvation of Mg²⁺ ions were interpreted.     

Synthesis and Characterization of （CH3CH2CH2CH2NH3）2SnBr6

1 INTRODUCTION Recently, the researches on inorganic-organic hy-brid compounds represent an advanced field in mate-rial science[1]. At the molecular level, the combina-tion of two extremely different components providesan avenue to design new hybrid materials as well asthe ability to modulate properties of one or more ofthe components[2～6]. Some attractive properties, suchas efficient luminescence[2～4], ideal thermal and me-chanical stability, interesting magnetic[5], non-linearoptical[…     

Structures of Pd(CN)2 and Pt(CN)2: intrinsically nanocrystalline materials?

Analysis and modeling of X-ray and neutron Bragg and total diffraction data show that the compounds referred to in the literature as "Pd(CN)(2)" and "Pt(CN)(2)" are nanocrystalline materials containing small sheets of vertex-sharing square-planar M(CN)(4) units, layered in a disordered manner with an intersheet separation of ~3.44 ? at 300 K. The small size of the crystallites means that the sheets' edges form a significant fraction of each material. The Pd(CN)(2) nanocrystallites studied using total neutron diffraction are terminated by water and the Pt(CN)(2) nanocrystallites by ammonia, in place of half of the terminal cyanide groups, thus maintaining charge neutrality. The neutron samples contain sheets of approximate dimensions 30 ? × 30 ?. For sheets of the size we describe, our structural models predict compositions of Pd(CN)(2)·xH(2)O and Pt(CN)(2)·yNH(3) (x ≈ y ≈ 0.29). These values are in good agreement with those obtained from total neutron diffraction and thermal analysis, and are also supported by infrared and Raman spectroscopy measurements. It is also possible to prepare related compounds Pd(CN)(2)·pNH(3) and Pt(CN)(2)·qH(2)O, in which the terminating groups are exchanged. Additional samples showing sheet sizes in the range ~10 ? × 10 ? (y ~ 0.67) to ~80 ? × 80 ? (p = q ~ 0.12), as determined by X-ray diffraction, have been prepared. The related mixed-metal phase, Pd(1/2)Pt(1/2)(CN)(2)·qH(2)O (q ~ 0.50), is also nanocrystalline (sheet size ~15 ? × 15 ?). In all cases, the interiors of the sheets are isostructural with those found in Ni(CN)(2). Removal of the final traces of water or ammonia by heating results in decomposition of the compounds to Pd and Pt metal, or in the case of the mixed-metal cyanide, the alloy, Pd(1/2)Pt(1/2), making it impossible to prepare the simple cyanides, Pd(CN)(2), Pt(CN)(2), or Pd(1/2)Pt(1/2)(CN)(2), by this method.     

Influence of axial ligands and anions on the Ni–Ni distances in trinickel string complexes: synthesis,structure, and properties of [Ni3(dpa)4(CH3CN)2] · (ClO4)2 · (CH3CN) · H2O

A cation–anion metal string complex with neutral axial ligands, [Ni₃(dpa)₄(CH₃CN)₂] · (ClO₄)₂ · (CH₃CN) · H₂O (1) where dpa^? is 2,2′-dipyridylamine anion, was synthesized and characterized by elemental analysis, IR, fluorescence, UV, and CV spectroscopic methods, and single crystal X-ray analysis. The Ni–Ni distances in 1 are longer than those in [Ni₃(dpa)₄(CH₃CN)₂] · (PF₆)₂ · 3.14CH₃CN (2) and [Ni₃(dpa)₄F₂] · [Ni₃(dpa)₄(H₂O)₂] · (BF₄)₂ · 2CH₃OH, indicating that the counter anions affect the Ni–Ni distances of trinickel string complexes. Compared with Ni₃(dpa)₄Cl₂ and Ni₃(dpa)₄(ClO₄)₂, 1 also has different fluorescence, UV, and CV properties. Therefore, this study clearly indicates that ligands and counter anions largely influence the structures and properties of trinickel string complexes.     

Crystal Structures of 1,3-Calix[4]-bis-crown-6·3CH3CN and 1,3-Calix[4]-bis-(benzo-crown-6)·3 CH3CN

The crystal structures of a new solvate of the ditopic receptor 1,3-calix[4]-bis-crown-6, Bis-C6, and of 1,3-calix[4]-bis-(benzo-crown-6), Bis-benzoC6, are reported. Bis-C6.3 CH3CN (1) crystallizes in the monoclinic space group P21/n, a = 14.388(3), b = 26.947(8), c = 14.707(4) Å, = 113.19(3)°, V = 5241(5) Å3, Z = 4. Refinement led to a final conventional R value of 0.092 for 2723 reflections. The structure of (1) differs from the previously reported structure of Bis-C6.4 CH3CN by the conformation of one crown either chain. Two acetonitrile molecules are in the close neighbourhood of the crown ether cavities. Bis-benzoC6.3 CH3CN (2) crystallizes in the monoclinic space group P21/c, a = 10.391(4), b = 17.264(11), c = 30.426(9) Å, = 94.62(3)°, V = 5440(7) Å3, Z = 4. Refinement led to a final conventional R value of 0.106 for 2965 reflections. Two acetonitrile molecules are located near the crown ether cavities, as in (1). One of the crown ether conformations is the same as in the binuclear caesium complex of Bis-benzoC6, supporting the hypothesis of a preorganization of this ligand towards the complexation of this ion; the second crown ether chain is partially disordered.     

Novel negatively charged cyanocuprate(I) host [Cu4(CN)7]3− built of tetrahedral Cu(I) coordination centers: Crystal structure of [{NH2(CH2CH2)2NCH2CH2NH2}2H][Cu4(CN)7]

The title inclusion compound [{NH₂(CH₂CH₂)₂NCH₂CH₂NH₂}₂H][Cu₄(CN)₇] was obtained as single crystals from an aqueous solution containing CuCN, KCN, andN-(2-aminoethyl)piperazine. It crystallizes in the monoclinic space groupP2/n,a = 12.3829(9),b = 8.5970(9),c = 12.6633(7) Å, = 109.984(5)°,z = 2,R = 0.035 for 2921 independent reflections. The inclusion structure is composed of the hydrogen-bonded dimeric onium guest [{NH₂(CH₂CH₂)₂NCH₂CH₂NH₂}₂H]³⁺ and the negatively-charged three-dimensional host [CU₄(CN)₇]^3– in which the CN-bridged framework Cu(I) atoms are all tetrahedral. A polyacene-like one-dimensional array of hexagons cornered by Cu(I) atoms and edged by -CN- linkages is arrayed in parallel to theb axis and stacked approximately along the c axis. The Cu(I) corner shared in the one-dimensional array extends an N-coordinate CN group along the c axis to a pair of unshared Cu(I) corners for which the C end behaves as a bifurcated ligand to build up the three-dimensional host structure. The cavity is composed of two networks of the hexagons at the top and bottom and pillared by six >CN- groups and accommodates a dimeric guest ofN-(2-aminoethyl)piperazinium cations protonated at each 4-N with the cations being hydrogen-bonded to each other through the 2-NH₂ groups sharing another H⁺.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Formation of a mixed valence copper(II)–copper(I) coordination polymer {[Cu(1,2-pn)2(μ3-I)Cu2(μ2-I)3(CH3CN)]⋅CH3CN}n: in situ reduction of copper(II) at ambient condition

A mixed valence copper(II)–copper(I) coordination polymer has been synthesized starting from a copper(II) salt at ambient condition and characterized by IR and Raman spectra and single crystal X-ray diffraction. The structure of the complex consists of a 1-D infinite chain with repeating unit [Cu(1,2-pn)₂(μ₃-I)Cu₂(μ₂-I)₃(CH₃CN)] and a free CH₃CN, where 1,2-pn = 1,2-diamino-1-propene. The complex shows a very short copper(I)–copper(I) distance (2.412?Å).     

Microwave spectrum,dipole moment and AB initio structure of iminopyruvonitrile (CH3C(CN)NH)

The microwave spectrum of iminopyruvonitrile has been investigated from 19 to 51 GHz. Rotational transitions have been assigned for the vibrational ground state and the rotational and centrifugal distortion constants have been adjusted. The electric dipole components μ_a = 1.806(6), μ_b = 0.759(21) and μ_total = 1.958(10) D have been deduced from Stark splittings. Some rotational transitions showed splittings arising from the internal rotation of the methyl group, the barrier to which has been determined to be V₃ = 593.5(89) cm⁻¹. Different conformations have been predicted via ab initio calculations and are compared to the microwave results.     

Synthesis and structure of [Cr3O(CH3COO)6(H2O)3][UO2 (CH3COO)3] · 3H2O

Crystals of [Cr₃O(CH₃COO)₆(H₂O)₃][UO₂(CH₃COO)₃]·3H₂O (I) were synthesized for the first time and studied by X-ray crystallography. The crystals of I are orthorhombic: a = 8.3561(3) ?, b = 16.8421(5) ?, c = 25.7448(9) ?, V = 3623.2(2) ?³, space group P2₁2₁2₁, Z = 4, R = 0.0409. The structure is composed of trinuclear [Cr₃O(CH₃COO)₆(H₂O)₃]⁺ complexes and mononuclear [UO₂(CH₃COO)₃]^? complexes classified with crystal-chemical groups A₃M³B ₆ ² M ₃ ¹ (A = Cr³⁺, M³ = O^2?, B² = CH₃COO^?, M¹ = H₂O) and AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?), respectively. The complexes are bound to each other by electrostatic interactions and hydrogen bonds involving outer-sphere water molecules. The results of IR spectroscopic study of I are in good agreement with the structural data for the crystal.     

The reaction of Sn[CH(SiMe3)2]2 with ethyne: formation of (HCC)Sn[CH(SiMe3)2]2(μ-trans-CHCH)Sn[CH-(SiMe3)2]2(CHCH2)

The reaction of Sn[CH(SiMe₃)₂]₂ and ethyne at ambient temperature affords a mixture of products, from which the title compound has been separated and identified by IR, ¹H, and ¹³C NMR spectroscopy.     

Synthesis and Crystallographic Characterization of Complex [(CH3)3NCH2CH2N(CH3)3][HgI4]·H2O Containing Novel Cation

The title compound has been synthesized by the reaction of HgI2 and [(CH3)3- NCH2CH2N(CH3)3]I2 with pH = 7.5 at room temperature, and its crystal structure was determined by single-crystal X-ray diffraction analysis. The title compound crystallizes in monoclinic system, space group P21/c with a = 8.3075(8), b =15.8084(19), c =15.390(2)(°A), β = 95.192(4)o, V = 2012.9(4)(°A)3, Z = 2, Dc = 2.824 g/cm3, F(000) = 1502, C14H39N4O2Hg2I8, Mr = 1711.87, μ(MoKα) = 13.768 mm-1, the final R = 0.0465 and wR = 0.1293 for 3046 observed reflections with I > 2(I). The title compound consists of cations ([C8H22N2]2+) and anion (HgI42-), which are combined by static attracting forces to form the so-called organic-inorganic hybrid material.     

Properties and structure of new volatile phenyl-containing β-diketonates of trimethylplatinum(IV): (CH3)3Pt(btfa)H2O, (CH3)3Pt(bac)Py, and initial complex [(CH3)3PtI]4

By interaction of trimethylplatinum(IV) iodide with phenyl-containing β-diketonates, the volatile monomeric complexes of trimethylplatinum(IV) based on benzoyltrifluoroacetone (Hbtfa) and benzoylacetone (Hbac) of the composition (CH₃)₃Pt(btfa)H₂O (I) and (CH₃)₃Pt(bac)Py (II) are obtained. Synthesis of the complexes is described; data of elemental analysis and IR spectra are reported; thermal characteristics are studied by thermogravimetry. For the first time, a single crystal X-ray diffraction study of complexes (I), (II), and the initial tetrameric complex [(CH₃)₃PtI]₄ (III) is performed.     

Crystal structures of the selenium- and bromo-bridged copper(I) dimers [Cu2(μ2-Br)2(SePPh3)2 · (NCCH3)2] and [Cu2I2(μ3-dppm-Se,Se)2] · 2CH3CN

Reactions of copper(I) halides with Se-donor ligands, namely, triphenylphosphine selenide (Ph₃PSe) and bis(diphenylselenophosphinyl)methane (dppm-Se,Se) yielded bromo-bridged [Cu₂(μ₂-Br)₂(SePPh₃)₂(NCCH₃)₂] (1), and selenium-bridged, [Cu₂I₂(μ₃-dppm-Se,Se)₂]?· 2CH₃CN (2) dimers, whose crystal structures are described. Acetonitrile stabilizes 1 by coordinating and helps to stabilize the packing in crystals of 2.