〔C_5H_4C(CH_3)_2CH_2CH=CH_2〕Sm(OH)Cl·2MgCl_2·4THF的晶体结构分析

用Ｘ－射线晶体结构衍射法测定了〔Ｃ５Ｈ４Ｃ（ＣＨ３）２ＣＨ２ＣＨ＝ＣＨ２〕Ｓｍ（ＯＨ）Ｃｌ·２ＭｇＣｌ２·４ＴＨＦ的晶体结构。它属三斜晶系,空间群为Ｐ１,ａ＝１０．７７３（２）,ｂ＝１２．８３６（３）,ｃ＝１５．４７８（３）,α＝１１１．４６（３）,β＝１０７．７１（３）,γ＝９２．５４（３）°,Ｖ＝１８６８（１）３,Ｍｒ＝８２７．９１,Ｄｘ＝１．４７２ｇ／ｃｍ３,μ＝２．０００６ｍｍ－１,Ｆ（０００）＝８４０,Ｚ＝２,Ｒ＝０．０４１,ｗＲ＝０．０５０（Ｉ≥３σ（Ｉ））。分子中Ｓｍ原子的配位数为８,形成一个严重扭曲的八面体结构;２个Ｍｇ原子的配位情况相似,它们的配位数都是６,分别构成２个扭曲的八面体。这３个八面体通过３个共平面联接     

Substituted N-picolylethylenediamines of the type (ArNHCH2CH2){(2-C5H4N)CH2}NR [R = Me, 4-CH2=CH(C6H4)CH2, (2-C5H4N)CH2] and their transition metal(II) halide complexes

Alkylation of (ArNHCH2CH2){(2-C5H4N)CH2}NH with RX [RX = MeI, 4-CH2=CH(C6H4)CH2Cl) and (2-C5H5N)CH2Cl] in the presence of base has allowed access to the sterically demanding multidentate nitrogen donor ligands, {(2,4,6-Me3C6H2)NHCH2CH2}{(2-C5H4N)CH2}NMe (L1), {(2,6-Me3C6H3)NHCH2CH2}{(2-C5H4N)CH2}NCH2(C6H4)-4-CH=CH2 (L2) and (ArNHCH2CH2){(2-C5H4N)CH2}2N (Ar = 2,4-Me2C6H3 L3a, 2,6-Me2C6H3 L3b) in moderate yield. L3 can also be prepared in higher yield by the reaction of (NH2CH2CH2){(2-C5H4N)CH2}2N with the corresponding aryl bromide in the presence of base and a palladium(0) catalyst. Treatment of L1 or L2 with MCl2 [MCl2 = CoCl2.6H2O or FeCl2(THF)1.5] in THF affords the high spin complexes [(L1)MCl2](M = Co 1a, Fe 1b) and [(L2)MCl2](M = Co 2a, Fe 2b) in good yield, respectively; the molecular structure of reveals a five-coordinate metal centre with bound in a facial fashion. The six-coordinate complexes, [(L3a)MCl2](M = Co 3a, Fe 3b, Mn 3c) are accessible on treatment of tripodal L3a with MCl2. In contrast, the reaction with the more sterically encumbered leads to the pseudo-five-coordinate species [(L3b)MCl2](M = Co 4a, Fe 4b) and, in the case of manganese, dimeric [(L3b)MnCl(mu-Cl)]2 (4c); in 4a and 4b the aryl-substituted amine arm forms a partial interaction with the metal centre while in 4c the arm is pendant. The single crystal X-ray structures of , 1a, 3b.MeCN, 3c.MeCN, 4b.MeCN and 4c are described as are the solution state properties of 3b and 4b.     

Silylation as a protective method in acetylene chemistry. : Syntheses in the polyeneyne series,R3Si(CC)n(CHCH)4(CC)nSiR3 and H(CC)n(CHCH)4(CC)nH (n = 1, 2)

The Grignard reagents R₃Si(CC)_nMgBr (R = Me, n = 1; R = Et, n = 1,2) couple with cyclooctatetraene dibromide 1 in THF to give, as major products, the silyl-stabilised E, Z, Z, E-polyeneynes, Me₃SiCC(CHCH)₄CCSiMe₃3a, Et₃SiCC(CHCH)₄CCSiEt₃4a and Et₃Si(CC)₂(CHCH)₄(CC)₂SiEt₃6a together with minor proportions of configurational isomers Z, E, Z, Z 3c, all -E 3b, 4b, 6b and compounds in which a bicyclo-octadiene structure 2, 5 and 7 is retained. Irradiation converts the cis(Z)-rich isomers e.g. 3c into the all-trans(E) products. Treatment of the bissilyl compounds 3, 4 and 6 with aqueous base liberates the respective parent polyeneynes, H(CC)_n(CHCH)₄(CC)_nH, in each case.     

Gas-phase diastereoselectivity of secondary 5-substituted (X)-adamant-2-yl (X = F, Si(CH(3))(3)) cations

Secondary 5-X-adamant-2-yl cations IX (X = F, Si(CH3)3) have been generated in the gas phase (total pressure = 760 Torr) from protonation-induced defluorination of epimeric 2-F-5-X-adamantanes 1X and their kinetic diastereoselectivity toward CH318OH investigated in the 40-160 degrees C range. The experimental results indicate that the facial selectivity of IX is insensitive to the composition of the starting 1X epimers as well as to the presence and the concentration of a powerful base (N(C2H5)3). This kinetic picture, supported by B3LYP/6-31G* calculations, is consistent with a single stable pyramidalized structure for IX, that is, (Z)-5-F-adamant-2-yl (I(Z)F) and (E)-5-Si(CH3)3-adamant-2-yl cations (I(E)Si). The temperature dependence of the IX diastereoselectivity lends support to the intermediacy of noncovalent adducts [IX*CH318OH], characterized by a specific C2-H+...O18(H)CH3 hydrogen bonding interaction. Their conversion to the covalently bonded O-methylated (Z)- (II(Z)X) and (E)-5-X-adamantan-2-ols (II(E)X; X = F, Si(CH3)3) is governed by activation parameters, whose magnitude depends on the specific IX face accommodating CH318OH. The gas-phase diastereoselectivity of IX toward CH318OH is compared to that exhibited in related gas-phase and solution processes. The emerging picture indicates that the factors determining the diastereoselectivity of IX toward simple nucleophiles in the gaseous and condensed media are completely different.     

一维链状高价锰配合物[Mn_2(C_7H_4O_3)_4(CH_3OH)_2]·4H_2O_2CH_3OH的合成与结构

合成了一维链状高价锰配合物[Mn2(C7H4O3)4(CH3OH)2]4H2O2CH3OH,并对其进行了IR、X-射线衍射、UV-Vis和TG-DSC等表征。单晶衍射结果表明,该配合物晶体属三斜晶型,空间群P?晶胞参数a=7.653(5),b=10.486(7),c=12.943(8),=103.24(1),?=104.55(1),?=110.11(1),V=885.4(9)3,Z=1。UV-Vis光谱在547nm有一个吸收峰,相应于Mn(Ⅳ)的d-d电子跃迁光谱。     

Cu4(CH3C(OH)(PO3)2)2(C4H4N2)(H2O)4: a novel,three-dimensional copper diphosphonate with metamagnetism

A novel, three-dimensional copper diphosphonate Cu4(CH3C(OH)(PO3)2)2(C4H4N2)(H2O)4 (1) incorporating an organic pyrazine ligand has been hydrothermally synthesized, which exhibits antiferromagnetic ordering below 4.2 K and metamagnetic behavior.     

Syntheses, Spectroscopic Properties and Crystal Structures of （2-Cl-C6H4CH2）3SnS2CN（C5H10） and （2-Cl-C6H4CH2）3SnS2CN（C4H9N）

1 INTRODUCTION The chemistry of organotin(IV) complexes was extensively studied due to their biological activity and coordination chemistry[1～7]. More recently, phar- maceutical properties of alkyltin(IV) complexes with dithiocarbamate ligands have bee…     

Synthesis and single-crystal x-ray diffraction examination of a structurally homologous series of tetracoordinate heteroleptic anionic lanthanide complexes: Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(L)3 (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb; (L)3 =(THF)3, (Et2O)3, (THF)2(Et2O)

Anhydrous lanthanide(III) chlorides (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) react with 3 equiv of lithium 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentanide, Li[N[Si(CH3)2CH2Ch2Si(CH3)2]], in THF or Et(2)O to afford the monomeric four-coordinate heteroleptic ate complexes Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(THF/Et2O)3 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), Tm (8), Yb (9)), whose solid-state structures were determined by the single-crystal X-ray diffraction technique. All complexes additionally were characterized by melting point determination, elemental analyses, and mass spectrometry.     

Syntheses,Crystal Structures and Properties of Three New Complexes [Ni（C9N2O2H7）2（CH3OH）2],[Zn（C9N2O2H7）2（H2O）2] and [Cd（C9N2O2H7）2（CH3OH）2]

Three novel metal-organic complexes with formulas [Ni(C9N2O2H7)2(CH3OH)2](1),[Zn(C9N2O2H7)2(H2O)2](2) and [Cd(C9N2O2H7)2(CH3OH)2](3) were synthesized by the reactions of Ni,Zn and Cd salts with ethyl 2-benzimidazolylacetate under hydrothermal conditions or layering technique,and characterized by single-crystal X-ray diffraction analysis,IR spec-troscopy,solid-state luminescent properties and thermogravimetric(TG) analysis.The crystal data for these three complexes are as follows:for 1,monoclinic,space group P21/c,a = 9.384(3),b = 9.634(3),c = 11.292(3) ,β = 95.787(5)°,V = 1015.7(5) 3,Z = 2,F(000) = 492,Dc = 1.547 Kg/m3,μ = 1.002 mm-1,the final R = 0.0451 and wR = 0.0900 for 1833 observed reflections with Ⅰ 2σ(Ⅰ);for 2,orthorhombic,space group Pbca,a = 10.031(4),b = 10.379(4),c = 17.525(7),V = 1824.6(12) 3,Z = 4,F(000) = 928,Dc = 1.645 Kg/m3,μ = 1.392 mm-1,the final R = 0.0452 and wR = 0.0996 for 1661 observed reflections with Ⅰ 2σ(Ⅰ);for 3,monoclinic,space group P21/c,a = 9.9114(13),b =10.4852(15),c = 10.4120(14) ,β = 108.453(5)°,V = 1026.4(2) 3,Z = 2,F(000) = 532,Dc = 1.705 Kg/m3,μ = 1.110 mm-1,the final R = 0.0322 and wR = 0.0805 for 1822 observed reflections with Ⅰ 2σ(Ⅰ).In the three complexes,the ethyl 2-benzimidazolylacetate shows the same chelating mode,and the adjacent units are interlinked into a two-dimensional layer through hydrogen-bonds(O-H···O,N-H···O).     

Preparation and Crystal Structure of Hetero-metal Clusters [h5-C5H4C(O)CH2CH2C(O)OCH3]FeCoM(m3-S)(CO)8 (M = Mo or W)

The hetero-metal clusters [h5-C5H4C(O)CH2CH2C(O)OCH3]FeCoM(m3-S)(CO)8 (M = Mo 1, M = W 2) were prepared by thermal reactions of FeCo2(CO)9(m3-S) with metal exchange reagent [h5-C5H4C(O)CH2CH2C(O)OCH3]M(CO)3Na (M = Mo or W) in THF. Cluster 1 reacted with 2,4-dinitrophenylhydrazine at room temperature to yield the cluster hydrazone derivative (m3-S)CoFeMo(CO)8[h5-C5H4C(NR)Me] [R = NHC6H3-2,4-(NO2)2] 3. All the compounds were characterized by elemental analyses, IR and NMR spectra. Cluster 1 was determined by single crystal X-ray diffraction. Crystal data: C18H11O11SCoFeMo, Mr = 646.05, triclinic, space group P_1, a = 8.148(2), b = 10.685(3), c = 13.410(4) ?, a = 100.077(5), b = 102.452(5), g = 91.108(6)°, V = 1120.4(5) ?3, Z = 2, Dc = 1.915 g/cm3, F(000) = 636, m = 2.071 mm-1, the final R = 0.0378 and wR = 0.0968 for 5074 observations with (I > 2s(I)).     

Three-, two-, and one-dimensional metal phosphonates based on [hydroxy(4-pyridyl)methyl]phosphonate: M{(4-C5H4N)CH(OH)PO3}(H2O) (M = Ni, Cd) and Gd{(4-C5H4N)CH(OH)P(OH)O2}3.6H2O

Based on the [hydroxy(4-pyridyl)methyl]phosphonate ligand, three compounds with formula Ni{(4-C(5)H(4)N)CH(OH)PO(3)}(H(2)O) (1), Cd{(4-C(5)H(4)N)CH(OH)PO(3)}(H(2)O) (2), and Gd{(4-C(5)H(4)N)CH(OH)P(OH)O(2)}(3).6H(2)O (3) have been synthesized under hydrothermal conditions. The crystal data for 1 are as follows: orthorhombic, space group Pbca, a = 8.7980(13) A, b = 10.1982(15) A, and c = 17.945(3) A. For 2 the crystal data are as follows: monoclinic, space group C2/c, a = 23.344(6) Angstroms, b = 5.2745(14) Angstroms, c = 16.571(4) Angstroms, and beta = 121.576(4) degrees. The crystal data for 3 are as follows: rhombohedral, space group R, a = 22.2714(16) Angstroms, b = 22.2714(16) Angstroms, and c = 9.8838(11) Angstroms. Compound 1 adopts a three-dimensional pillared layered structure in which the inorganic layers made up of corner-sharing {NiO(5)N} octahedra and {CPO(3)} tetrahedra are connected by pyridyl groups. A two-dimensional layer structure is found in compound 2, which contains alternating inorganic double chains and pyridyl rings. Compound 3 has a one-dimensional chain structure where the Gd atoms are triply bridged by O-P-O linkages. The pyridyl nitrogen atom in 3 remains uncoordinated and is involved in the interchain hydrogen bonds. Magnetic susceptibility studies of 1 and 3 reveal that weak ferromagnetic interactions are mediated between Ni(II) centers in compound 1. For compound 3, the behavior is principally paramagnetic.     

Kinetics and mechanism of the reactions of CH3CO and CH3C(O)CH2 radicals with O2. Low-pressure discharge flow experiments and quantum chemical computations

The reactions CH(3)CO + O(2)--> products (1), CH(3)CO + O(2)--> OH +other products (1b) and CH(3)C(O)CH(2) + O(2)--> products (2) have been studied in isothermal discharge flow reactors with laser induced fluorescence monitoring of OH and CH(3)C(O)CH(2) radicals. The experiments have been performed at overall pressures between 1.33 and 10.91 mbar of helium and 298 +/- 1 K reaction temperature. OH formation has been found to be the dominant reaction channel for CH(3)CO + O(2): the branching ratio, Gamma(1b) = k(1b)/k(1), is close to unity at around 1 mbar, but decreases rapidly with increasing pressure. The rate constant of the overall reaction, k(2), has been found to be pressure dependent: the fall-off behaviour has been analysed in comparison with reported data. Electronic structure calculations have confirmed that at room temperature the reaction of CH(3)C(O)CH(2) with O(2) is essentially a recombination-type process. At high temperatures, the further reactions of the acetonyl-peroxyl adduct may yield OH radicals, but the most probable channel seems to be the O(2)-catalysed keto-enol transformation of acetonyl. Implications of the results for atmospheric modelling studies have been discussed.     

Investigation of the radical product channel of the CH(3)C(O)CH(2)O(2) + HO(2) reaction in the gas phase

The reaction of CH(3)C(O)CH(2)O(2) with HO(2) has been studied at 296 K and 700 Torr using long path FTIR spectroscopy, during photolysis of Cl(2)/acetone/methanol/air mixtures. The branching ratio for the reaction channel forming CH(3)C(O)CH(2)O, OH and O(2) () was investigated in experiments in which OH radicals were scavenged by addition of benzene to the system, with subsequent formation of phenol used as the primary diagnostic for OH radical formation. The observed prompt formation of phenol under conditions when CH(3)C(O)CH(2)O(2) reacts mainly with HO(2) indicates that this reaction proceeds partially by channel , which forms OH both directly and indirectly, by virtue of secondary generation of CH(3)C(O)O(2) (from CH(3)C(O)CH(2)O) and its reaction with HO(2) (). The secondary generation of OH radicals was confirmed by the observed formation of CH(3)C(O)OOH, a well-established product of the CH(3)C(O)O(2) + HO(2) reaction (via channel ). A number of delayed sources of OH also contribute to the observed phenol formation, such that full characterisation of the system required simulations using a detailed chemical mechanism. The dependence of the phenol and CH(3)C(O)OOH yields on the initial peroxy radical precursor reagent concentration ratio, [methanol](0)/[acetone](0), were well described by the mechanism, consistent with a small but significant fraction of the reaction of CH(3)C(O)CH(2)O(2) with HO(2) proceeding via channel . This allowed a branching ratio of k(3b)/k(3) = 0.15 +/- 0.08 to be determined. The results therefore provide strong indirect evidence for the participation of the radical-forming channel of the title reaction.     

Atmospheric chemistry of CF3CH=CH2 and C4F9CH=CH2: products of the gas-phase reactions with Cl atoms and OH radicals

FTIR-smog chamber techniques were used to study the products of the Cl atom and OH radical initiated oxidation of CF3CH=CH2 in 700 Torr of N2/O2, diluent at 296 K. The Cl atom initiated oxidation of CF3CH=CH2 in 700 Torr of air in the absence of NOx gives CF3C(O)CH2Cl and CF3CHO in yields of 70+/-5% and 6.2+/-0.5%, respectively. Reaction with Cl atoms proceeds via addition to the >C=C< double bond (74+/-4% to the terminal and 26+/-4% to the central carbon atom) and leads to the formation of CF3CH(O)CH2Cl and CF3CHClCH2O radicals. Reaction with O2 and decomposition via C-C bond scission are competing loss mechanisms for CF3CH(O)CH2Cl radicals, kO2/kdiss=(3.8+/-1.8)x10(-18) cm3 molecule-1. The atmospheric fate of CF3CHClCH2O radicals is reaction with O2 to give CF3CHClCHO. The OH radical initiated oxidation of CxF2x+1CH=CH2 (x=1 and 4) in 700 Torr of air in the presence of NOx gives CxF2x+1CHO in a yield of 88+/-9%. Reaction with OH radicals proceeds via addition to the >C=C< double bond leading to the formation of CxF2x+1C(O)HCH2OH and CxF2x+1CHOHCH2O radicals. Decomposition via C-C bond scission is the sole fate of CxF2x+1CH(O)CH2OH and CxF2x+1CH(OH)CH2O radicals. As part of this work a rate constant of k(Cl+CF3C(O)CH2Cl)=(5.63+/-0.66)x10(-14) cm3 molecule-1 s-1 was determined. The results are discussed with respect to previous literature data and the possibility that the atmospheric oxidation of CxF2x+1CH=CH2 contributes to the observed burden of perfluorocarboxylic acids, CxF2x+1COOH, in remote locations.     

Hydrothermal Synthesis and Crystal Structure of [（CH3CH2）4N]4[（La12（OH）12MoO29）],A Novel Cluster Compound with a MoO5 Hexahedron Center surrounded by La—O Octahedron

IntroductionRecently,the molecular designs of polyox-ometalates( POM) with basic oxometal clusterbuilding blocks are of great interest[1,2 ] . Hy-drothermal synthesis,with the characteristic ofone- pot reaction,provides a convenient method toobtain novel structures of POM compounds[3— 6] . Inthe Ln/Mo/O system ( Ln=rare earth) ,somecompounds containing La and Mo elements havebeen reported[7— 17] . However,these compoundshave all been synthesized under the highly restrict-ed synthetic co…     

Atmospheric chemistry of a model biodiesel fuel, CH3C(O)O(CH2)2OC(O)CH3: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOx

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.     

Hydrothermal Synthesis and Crystal Structure of a New Phosphonate： {[Cu（1,10-phen）]2-（H2O3PCH2C6H4C6H4CH2PO3H）2-（HO3PCH2C6H4C6H4CH2PO3H） }n

1 INTRODUCTION Metal organophosphonates have attracted considerable attention for over three decades due to their potential or practical applications, include- ing ion exchanges[1, 2], molecular sensors[3] and optics[4, 5]. Recently, a number of porous m…     

Structures of [(CO2)n(CH3OH)m](-) (n = 1-4, m = 1, 2) cluster anions

The infrared photodissociation spectra of [(CO 2) n (CH 3OH) m ] (-) ( n = 1-4, m = 1, 2) are measured in the 2700-3700 cm (-1) range. The observed spectra consist of an intense broad band characteristic of hydrogen-bonded OH stretching vibrations at approximately 3300 cm (-1) and congested vibrational bands around 2900 cm (-1). No photofragment signal is observed for [(CO 2) 1,2(CH 3OH) 1] (-) in the spectral range studied. Ab initio calculations are performed at the MP2/6-311++G** level to obtain structural information such as optimized structures, stabilization energies, and vibrational frequencies of [(CO 2) n (CH 3OH) m ] (-). Comparison between the experimental and the theoretical results reveals the structural properties of [(CO 2) n (CH 3OH) m ] (-): (1) the incorporated CH 3OH interacts directly with either CO 2 (-) or C 2O 4 (-) core by forming an O-HO linkage; (2) the introduction of CH 3OH promotes charge localization in the clusters via the hydrogen-bond formation, resulting in the predominance of CO 2 (-).(CH 3OH) m (CO 2) n-1 isomeric forms over C 2O 4 (-).(CH 3OH) m (CO 2) n-2 ; (3) the hydroxyl group of CH 3OH provides an additional solvation cite for neutral CO 2 molecules.     

Solution structures and dynamic properties of chelated d(0) metal olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) (R = H, Me): Models for the [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" catalysts.

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.     

Secondary kinetics of methanol decomposition: theoretical rate coefficients for 3CH2 + OH, 3CH2 + 3CH2, and 3CH2 + CH3

Direct variable reaction coordinate transition state theory (VRC-TST) rate coefficients are reported for the (3)CH(2) + OH, (3)CH(2) + (3)CH(2), and (3)CH(2) + CH(3) barrierless association reactions. The predicted rate coefficient for the (3)CH(2) + OH reaction (approximately 1.2 x 10(-10) cm(3) molecule(-1) s(-1) for 300-2500 K) is 4-5 times larger than previous estimates, indicating that this reaction may be an important sink for OH in many combustion systems. The predicted rate coefficients for the (3)CH(2) + CH(3) and (3)CH(2) + (3)CH(2) reactions are found to be in good agreement with the range of available experimental measurements. Product branching in the self-reaction of methylene is discussed, and the C(2)H(2) + 2H and C(2)H(2) + H2 products are predicted in a ratio of 4:1. The effect of the present set of rate coefficients on modeling the secondary kinetics of methanol decomposition is briefly considered. Finally, the present set of rate coefficients, along with previous VRC-TST determinations of the rate coefficients for the self-reactions of CH(3) and OH and for the CH(3) + OH reaction, are used to test the geometric mean rule for the CH(3), (3)CH(2), and OH fragments. The geometric mean rule is found to predict the cross-combination rate coefficients for the (3)CH(2) + OH and (3)CH(2) + CH(3) reactions to better than 20%, with a larger (up to 50%) error for the CH(3) + OH reaction.