双核浆叶式钨配合物电子结构和电子光谱的理论研究

用密度函数理论中的B3LYP方法,对甲脒做配体的过渡金属双核浆叶式配合物W2（form)4((form)^-=[(p-tol)NCHN([p-tol)^-]^-)进行了分子轨道计算,结果表明,W－W键具σ^2π^4δ^2四重键的性质,W－W间的成键和反键分子轨道顺序为σ＜π＜δ＜σ^*＜π^*＜δ^*。用单激发组态相互作用（CIS）方法计算了W2(form)4的电子吸收光谱,得到这种配合物的最低能吸收光谱为λ＝496nm,这是δ（dxy）→σ^*(spz)跃迁产生的,属于金属内部的电荷迁移。     

1-碘丙烷分子的电子动量谱学研究：自旋-轨道耦合效应与分子内轨道相互作用

利用不对称不共面电子动量谱仪,在2.5 keV碰撞能量下,采用高精度的SAC-CI方法计算了1-碘丙烷分子束缚能谱,同时采用Hartree-Fock、B3LYP/aug-cc-pVTZ（C,H）6-311G＊＊（I）方法计算其电子动量分布. 并对电离能峰进行了标示. 结合非相对论与相对论计算方法以及自然键轨道分析,对最外层两个轨道（碘的5p孤对）的自旋-轨道耦合效应与分子内轨道相互作用进行了比较. 两种相互作用对电子动量分布的不同影响是可观的. 实验结果与相对论计算的结果一致,表明1-碘丙烷分子内自旋-轨道耦合效应占主导.     

[2~3]Cyclophanes电子结构的理论研究

用改造的重叠模型多重散射X~α自洽场方法计算环芳类化合物[2~3]cyclophanes的电子结构, 分析该类分子中分子轨道通过空间和通过键的相互作用,单键连接桥.双键连接桥对通过键相互作用的影响, 用过渡态理论方法计算分子前线分子轨道的电离能,理论结果与紫外光电子能谙符合较好.     

用分子片轨道逐步剔除法研究电子离域

估计分子中不同类型的电子离域作用（如p-π → d-π和p-π → σ~*）的相 对强弱对理解分子中化学键的本质有关键的作用。剔除某一分子片轨道（d-π或σ ~*）后分子体系能量的改变可用来计算电子离域到该轨道的离域能。由于轨道之间 的相互作用,使离域能的计算与轨道剔除的次序有关。为克服这种不确定性,可以 逐步轮流增加某一对特定轨道（d-π和σ~*）的库仑积分,以使这对轨道在分子波 函数中的比重逐步减少,即将这对轨道轮流逐步剔除。这样可将轨道间的相互影响 减小以至消除,从而得到各轨道的精确的离域能。以H_3PO中P-O键为例说明了轨道 逐步剔除方法的应用。     

二氧化氮的电子结构

本文根据实验事实和定性分子轨道理论讨论了二氧化氮分子的电子结构,指出分子中的大π键不是Π_3~3,而是Π_3~4。本文还讨论了NO_2分子二聚生成N_2O_4分子的结构模型。     

CNDO/2法计算二茂锆卤化物的电子结构

本文将Pople的闭壳层CNDO/2程序改编成将原子中s,p,d亚层分开处理,并扩展到可计算锆化合物的CNDO/2-TM程序;选取了锆的有关参数;计算了Cp_2ZrX_2(X=F,Cl)分子的电子结构.得到的氯化物分子轨道的能级次序和间隔与光电子能谱相符.计算的偶极矩为5.88D,与实验值相近.计算结果还说明Cp_2ZrX_2是有一定离子性的共价化合物.中心锆原子约呈 1价.金属锆的5s轨道参与茂环的σ键,5p轨道通过移入电子参与茂环σ键,而4d轨道则参与茂环的π键,但成键所占成分不大.Zr-F键的离子性占51％,Zr-Cl键的离子性占44％,Zr-Cp键的共价性在84～93％之间.     

C2F51分子C—I键解离的自旋-轨道从头算研究

采用考虑相对论效应的6—311G^＊＊全电子基组与多参考微扰理论,计算了该分子的包含自旋-轨道耦合效应的垂直激发能和基态、激发态C—I键解离势能曲线．理论计算发现,势能曲线3^3A＂与1^1A＂,2^1A＇出现交叉,交叉区域在C—I键长为0．241nm附近;基态1^A＇到激发态3^3A＂（^3Q0）的垂直激发能为4．658eV,与实验值4．662eV非常吻合．讨论了C2F5I分子作为碘激光介质的可行性．     

2，2′—双吡啶双氯二价铂化合物Pt（bpy）Cl2（黄色）的电子结构和电子光谱性质的从头计算研究

用从头算MP2方法,采用LANL2DZ基组,对Pt(bpy)Cl2分子进行了分子轨道计算,计算得到这种分子的HOMO和LUMO都具有反键π^*轨道的性质,给出了具有较高能量的分子轨道的顺序,并分析了各分子轨道的组成,用单激发组态相互作用（CIS）方法计算了具有“单体”晶型的Pt(bpy)Cl2的电子吸收光谱的发射光谱,结果表明：最低能吸收光谱为γ＝350．99nm,具有金属到配体的电荷迁移性质;最低能发射光谱为γ＝566．39nm,具有配体内电荷迁移的性质。     

Mo2［(p-tol)NCHN(p-tol)］4及其阳离子电子结构和电子吸收光谱的从头算研究

用密度泛函理论中的B3LYP方法, 采用LanL2DZ基组, 对Mo2(form)4和［Mo2(form)4］+{其中(form)-=［(p-tol)NCHN(p-tol)］-)}, 进行了分子轨道计算, 明确了Mo—Mo键具有σ2π4δ2四重键的性质. 计算得到Mo—Mo间的分子轨道顺序为π<σ<δ<σ*<δ*<π*. 用单激发组态相互作用（CIS）方法计算了Mo2(form)4和［Mo2(form)4］+的电子吸收光谱, Mo2(form)4的最低能吸收光谱λ=390 nm, 是1A1g→1Eg跃迁产生的, 属于金属内部的电荷迁移. ［Mo2(form)4］+的最低能吸收光谱λ=1 096 nm, 也是1Ag→1Eg跃迁产生的, 属于金属内部的电荷迁移.     

菁染料光解机理的前线分子轨道研究

通过SCF PM3和AM1 MO计算研究，揭示了正离子型菁染料与相应中性化合物在分子几何、电荷分布、前线分子轨道能级和组成等方面的不同特点。特别是根据前线轨道理论和成键三原则，通过比较氧的激发单态（^1O2^*)或超氧负离子自由基（O2^-.）与标题物之间的前线轨道相互作用，阐明了标题物的光解机理和正离子较中性化合物光稳定的根由。结论与实验事实良好相符。     

Electronic spectral studies of molybdenyl complexes. 2. MCD spectroscopy of [MoOS4]- centers

Magnetic circular dichroism (MCD) and absorption spectroscopies have been used to probe the electronic structure of [PPh4][MoO(p-SC6H4X)4] (X = H, Cl, OMe) and [PPh4][MoO(edt)2] complexes (edt = ethane-1,2-dithiolate). The results of density functional calculations (DFT) on [MoO(SMe)4]- and [MoO(edt)2]- model complexes were used to provide a framework for the interpretation of the spectra. Our analysis shows that the lowest energy transitions in [MoVOS4] chromophores (S4 = sulfur donor ligand) result from S-->Mo charge transfer transitions from S valence orbitals that lie close to the ligand field manifold. The energies of these transitions are strongly dependent on the orientation of the S lone-pair orbitals with respect to the Mo atom that is determined by the geometry of the ligand backbone. Thus, the lowest energy transition in the MCD spectrum of [PPh4][MoO(p-SC6H4X)4] (X = H) occurs at 14,800 cm-1, while that in [PPh4][MoO(edt)2] occurs at 11,900 cm-1. The identification of three bands in the absorption spectrum of [PPh4][MoO(edt)2] arising from LMCT from S pseudo-sigma combinations to the singly occupied Mo 4d orbital in the xy plane suggests that there is considerable covalency in the ground-state electronic structures of [MoOS4] complexes. DFT calculations on [MoO(SMe)4]- reveal that the singly occupied HOMO is 53% Mo 4dxy and 35% S p for the equilibrium C4 geometry. For [MoO(edt)2]- the steric constraints imposed by the edt ligands result in the S pi orbitals being of similar energy to the Mo 4d manifold. Significant S pseudo-sigma and pi donation may also weaken the Mo identical to O bond in [MoOS4] centers, a requirement for facile active site regeneration in the catalytic cycle of the DMSO reductases. The strong dependence of the energies of the bands in the absorption and MCD spectra of [PPh4][MoO(p-SC6H4X)4] (X = H, Cl, OMe) and [PPh4][MoO(edt)2] on the ligand geometry suggests that the structural features of the active sites of the DMSO reductases may result in an electronic structure that is optimized for facile oxygen atom transfer.     

Kinetics, mechanism, and computational studies of rhenium-catalyzed desulfurization reactions of thiiranes (thioepoxides)

The oxorhenium(V) dimer {MeReO(edt)}2 (1; where edt = 1,2-ethanedithiolate) catalyzes S atom transfer from thiiranes to triarylphosphines and triarylarsines. Despite the fact that phosphines are more nucleophilic than arsines, phosphines are less effective because they rapidly convert the dimer catalyst to the much less reactive catalyst [MeReO(edt)(PAr3)] (2). With AsAr3, which does not yield the monomer, the rate law is given by v = k[thiirane][1], independent of the arsine concentration. The values of k at 25.0 degrees C in CDCl3 are 5.58 +/- 0.08 L mol(-1) s(-1) for cyclohexene sulfide and ca. 2 L mol(-1) s(-1) for propylene sulfide. The activation parameters for cyclohexene sulfide are deltaH(double dagger) = 10.0 +/- 0.9 kcal mol(-1) and deltaS(double dagger) = -21 +/- 3 cal K(-1) mol(-1). Arsine enters the catalytic cycle after the rate-controlling release of alkene, undergoing a reaction with the Re(VII)(O)(S) intermediate that is so rapid in comparison that it cannot be studied directly. The use of a kinetic competition method provided relative rate constants and a Hammett reaction constant, rho = -1.0. Computations showed that there is little thermodynamic selectivity for arsine attack at O or S of the intermediate. There is, however, a large kinetic selectivity in favor of Ar3AsS formation: the calculated values of deltaH(double dagger) for attack of AsAr3 at Re=O vs Re=S in Re(VII)(O)(S) are 23.2 and 1.1 kcal mol(-1), respectively.     

Thermodynamics, kinetics, and mechanism of the reversible formation of oxorhenium(VII) catecholate complexes

Mononuclear Re(V) compounds MeReO(mtp)NC(5)H(4)X, 3, where mtpH(2) is 2-(mercaptomethyl)thiophenol have been prepared from the monomerization of [MeReO(mtp)](2) by pyridines with electron-donating substituents in the para or meta position; X = 4-Me, 4-Bu(t), 3-Me, 4-Ph, and H. Analogous compounds, MeReO(edt)N(5)H(4)X, 4, edtH(2) = 1,2-ethanedithiol, were prepared similarly. The equilibrium constants for the reaction, dimer + 2Py = 2M-Py, are in the range (2.5-31.6) x 10(2) L mol(-1). Both groups of monomeric compounds react with quinones (phenanthrenequinone, PQ, and 3,5-tert-butyl-1,2-benzoquinone, DBQ), displacing the pyridine ligand and forming Re(VII) catecholate complexes MeReO(dithiolate)PCat and MeReO(dithiolate)DBCat. With PQ, the reaction MeReO(dithiolate)Py + PQ = MeReO(dithiolate)PCat + Py is an equilibrium; values of K(Q) for different Py ligands lie in the ranges 9.2-42.7 (mtp) and 3.2-11.2 (edt) at 298 K. These second-order rate constants (L mol(-1) s(-1)) at 25 degrees C in benzene were obtained for the PQ reactions: k(f) = (5.3-15.5) x 10(-2) (mtp), (6.6-16.4) x 10(-2) (edt); k(r) = (3.63-5.71) x 10(-3) (mtp), (14.7-22.0) x 10(-3) (edt). The ranges in each case refer to the series of pyridine ligands, the forward rate constant being the largest for C(5)H(5)N, with the lowest Lewis basicity. The reactions of MeReO(dithiolate)Py with DBQ proceed to completion. Values of k(f)/L mol(-1) s(-1) fall in a narrow range, 4.02 (X = Bu(t)) to 8.4 (X = H) with the dithiolate being mtp.     

Ligand displacement and oxidation reactions of methyl(oxo)rhenium(V) complexes

Compounds that contain the anion [MeReO(edt)(SPh)](-) (3-) were synthesized with the countercations 2-picolinium (PicH+3-) and 2,6-lutidinium (LutH+3-), where edt is 1,2-ethanedithiolate. Both PicH+3- and MeReO(edt)(tetramethylthiourea) (4) were crystallographically characterized. The rhenium atom in each of these compounds exists in a five-coordinate distorted square pyramid. In the solid state, PicH+3- contains an anion with a short (d(SH) = 232 pm) and nearly linear hydrogen-bonded (N-H.S) interaction to the cation. Ligand substitution reactions were studied in chloroform. Displacement of PhSH by PPh(3) follows second-order kinetics, d[MeReO(edt)(PPh(3))]/dt = k[PicH+3-][PPh3], whereas with pyridines an unusual form was found, d[MeReO(edt)(Py)]/dt = k[PyH+3-][Py](2), in which the conversion of PicH+3- to PyH+3- has been incorporated. Further, added Py accelerates the formation of [MeReO(edt)(PPh3)], v = k.[PicH+3-].[PPh3].[Py]. Compound 4, on the other hand, reacts with both PPh(3) and pyridines, L, at a rate given by d[MeReO(edt)(L)]/dt = k.[4].[L]. When PicH+3- reacts with pyridine N-oxides, a three-stage reaction was observed, consistent with ligand replacement of SPh(-) by PyO, N-O bond cleavage of the PyO assisted by another PyO, and eventual decomposition of MeRe(O)(edt)(OPy) to MeReO(3). Each of first two steps showed a large substituent effect; Hammett analysis gave rho(1) = -5.3 and rho(2) = -4.3.     

High-nuclearity sulfide-rich molybdenum[bond]iron[bond]sulfur clusters: reevaluation and extension

High-nuclearity Mo[bond]Fe[bond]S clusters are of interest as potential synthetic precursors to the MoFe(7)S(9) cofactor cluster of nitrogenase. In this context, the synthesis and properties of previously reported but sparsely described trinuclear [(edt)(2)M(2)FeS(6)](3-) (M = Mo (2), W (3)) and hexanuclear [(edt)(2)Mo(2)Fe(4)S(9)](4-) (4, edt = ethane-1,2-dithiolate; Zhang, Z.; et al. Kexue Tongbao 1987, 32, 1405) have been reexamined and extended. More accurate structures of 2-4 that confirm earlier findings have been determined. Detailed preparations (not previously available) are given for 2 and 3, whose structures exhibit the C(2) arrangement [[(edt)M(S)(mu(2)-S)(2)](2)Fe(III)](3-) with square pyramidal Mo(V) and tetrahedral Fe(III). Oxidation states follow from (57)Fe M?ssbauer parameters and an S = (3)/(2) ground state from the EPR spectrum. The assembly system 2/3FeCl(3)/3Li(2)S/nNaSEt in methanol/acetonitrile (n = 4) affords (R(4)N)(4)[4] (R = Et, Bu; 70-80%). The structure of 4 contains the [Mo(2)Fe(4)(mu(2)-S)(6)(mu(3)-S)(2)(mu(4)-S)](0) core, with the same bridging pattern as the [Fe(6)S(9)](2-) core of [Fe(6)S(9)(SR)(2)](4-) (1), in overall C(2v) symmetry. Cluster 4 supports a reversible three-member electron transfer series 4-/3-/2- with E(1/2) = -0.76 and -0.30 V in Me(2)SO. Oxidation of (Et(4)N)(4)[4] in DMF with 1 equiv of tropylium ion gives [(edt)(2)Mo(2)Fe(4)S(9)](3-) (5) isolated as (Et(4)N)(3)[5].2DMF (75%). Alternatively, the assembly system (n = 3) gives the oxidized cluster directly as (Bu(4)N)(3)[5] (53%). Treatment of 5 with 1 equiv of [Cp(2)Fe](1+) in DMF did not result in one-electron oxidation but instead produced heptanuclear [(edt)(2)Mo(2)Fe(5)S(11)](3-) (6), isolated as the Bu(4)N(+)salt (38%). Cluster 6 features the previously unknown core Mo(2)Fe(5)(mu(2)-S)(7)(mu(3)-S)(4) in molecular C(2) symmetry. In 4-6, the (edt)MoS(3) sites are distorted trigonal bipramidal and the FeS(4) sites are distorted tetrahedral with all sulfide ligands bridging. M?ssbauer spectroscopic data for 2 and 4-6 are reported; (mean) iron oxidation states increase in the order 4 < 5 approximately 1 < 6 approximately 2. Redox and spectroscopic data attributed earlier to clusters 2 and 4 are largely in disagreement with those determined in this work. The only iron and molybdenum[bond]iron clusters with the same sulfide content as the iron[bond]molybdenum cofactor of nitrogenase are [Fe(6)S(9)(SR)(2)](4-) and [(edt)(2)Mo(2)Fe(4)S(9)](3-)(,4-).     

Synthesis and Structural Characterization of a Salt{[Co(Phen)3][Mo2S2(μ-S)2(edt)2]}2·(DMSO)2·(Et2O)(Phen = 1,10-Phenanthroline,edt = Ethane-1,2-dithiolate)

Reaction of [Et4N]2[Mo2S2(μ-S)2(edt)2] with CoCl2(6H2O and Phen in MeCN followed by recrystallization in DMSO/Et2O gave rise to dark-red block crystals of {[Co(Phen)3]- [Mo2S2(μ-S)2(edt)2]}2·(DMSO)2·(Et2O) 1 (C88H86Co2Mo4N12O3S18). 1 crystallizes in the monoclinic system, space group P21/c with a = 24.631(4), b = 16.117(3), c = 24.791(4) (A), β = 92.835°, V = 9829.3(3) (A)3, Z = 4, Mr = 2438.57, Dc = 1.648 g/cm3, F(000) = 4928, μ = 12.61 cm-1, R = 0.0936 and wR = 0.1682 for 12998 observed reflections with I > 2.0σ(I). In the structure of 1, the Co atom of the [Co(Phen)3]2+ dication is octahedrally coordinated by three Phen ligands. The Mo atom of the [Mo2S2(μ-S)2(edt)2]2- dianion is coordinated by two μ-S, one terminal S and two S atoms from edt, forming a distorted square pyramidal geometry. The mean Co-N and Mo…Mo bond distances are 2.139 and 2.872 (A), respectively.     

Synthesis and Structural Characterization of a Salt {[Co(Phen)_3][Mo_2S_2(μ-S)_2(edt)_2]}_2·(DMSO)_2·(Et_2O)(Phen = 1,10-Phenanthroline,edt=Ethane-1,2-dithiolate)

1 INTRODUCTION Dinuclear sulfido-bridged complexes with M2S2(μ-S)2 unit serving as building blocks for the construction of mixed-metal clusters are well docu- mented due to their rich structure diversities[1～3] as well as their potential applications in catalytic sys- tems and eletro/photonic materials[4, 5]. For example, reaction of [CpEt2Mo2S2(μ-S)2] with 2 equiv. of Co- (CO)3(NO) gave rise to a cubane-like cluster com- pound [CpEt2Mo2S2(μ-S)2Co2(CO)2][6]. In the case of[Mo…     

Theoretical Studies on the M-M Bonding in Complexes [M2Cl4L2] and [M2Cl7L]- （M = Mo, Re; L = Ph2Ppy, （Ph2P）2py）

The structures of complexes [MⅡ2Cl4L2] and [MⅢ2Cl7L]- (M = Mo, Re; L = Ph2Ppy, (Ph2P)2py) were calculated by using density functional theory (DFT) PBE0 method. Based on the optimized geometries, the natural bond orbital (NBO) analyses were carried out to study the nature of Re-Re and Mo-Mo bonds. The conclusions are as follows: the M-M distances in two-Ph2Ppy or (Ph2P)2py complexes [MⅡ2Cl4L2] are shorter than those in mono-Ph2Ppy or (Ph2P)2py complexes [MⅢ2Cl7L]- due to the double bridged N-C-P interactions. For singlet of all complexes, there is ReⅢ-ReⅢ or MoⅡ-MoⅡ quadruply bond in complex [Re2Cl7L]- or [Mo2Cl4L2], while only ReⅡ-ReⅡ or MoⅢ-MoⅢ triply bond in complex [Re2Cl4L2] or [Mo2Cl7L]-. The most stable spin state of 2 and 6, triplet, only contains triple ReⅢ-ReⅢ bond. Because the LPCl → BD*Re-Re delocalizations weaken the Re-Re bond, the distance of ReⅢ-ReⅢ quadruple bonds in [Re2Cl7L]- is slightly longer than that of ReⅡ-ReⅡ triple bonds in [Re2Cl4L2]. Moreover, due to the delocalizations from the lone pair electrons of the remaining P' atom to the M-M antibonding orbitals, the M-M distance in (Ph2P)2py complexes is slightly longer than that in Ph2Ppy complexes.     

Electronic structure of diamagnetic and paramagnetic hexanuclear chalcohalide clusters of rhenium

Hexanuclear chalcohalide clusters of rhenium(III) of general formula [Re(6)S(4+x)Cl(10-x)](x-) with x = 1-4 have been studied using quantum chemical DFT calculations. The optimized structures reproduce the geometrical features found from X-ray data for the members of the series. The relative stability of different stereoisomers for the mono- and dianions has been estimated. The analysis of the tetraanion series [Re(6)Q(8)X(6)](4-) with Q = S, Se and X = Cl, Br, I, and CN demonstrates the influence of the mu(1)- and mu( 3)-ligands on the strength of Re-apical ligand bond. It is shown that the tetragonal distortion found for the stable oxidized paramagnetic species [Re(6)S(8)Cl(6)]*(3-) results from the Jahn-Teller effect for a doubly degenerate electronic state.     

Synthesis and Crystal Structure of a New Mo/Au/S Cluster [Et4N][Mo2S4（AuPPh3）（edt）2]· 0.25Et2O·0.25MeOH （edt = Ethanedithiolate）

Reactions of the preformed cluster precursor [Et4N]2[Mo2S2（μ-S）2（edt）2] （edt = ethanedithiolate） （1） with [Au（PPh3）Cl] in MeOH/MeCN gave rise to a new heterobimetallic Mo/Au/S cluster [Et4N][Mo2S4（AuPPh3）（edt）2]·0.25Et2O·0.25MeOH （2·0.25Et2O·0.25MeOH）. It was characterized by elemental analysis, IR spectrum and X-ray analysis. 2·0.25Et2O·0.25MeOH crystallizes in the monoclinic system, space group C2/c with a = 20.117（4）, b = 9.2705（19）, c = 44.418（9） A^°, β= 93.19（3）°, V = 8271（3） A^°^3, Z = 8, Dc = 1.794 g/cm^3, T = 193 K, C31.25H43AuMo2NO0.50PS8, Mr = 1116.96, F（000） = 4380, μ（MoKa） = 4.603 mm^-1, S = 1.019, R = 0.0672 and wR = 0.1708 for 7243 observed reflections with I 〉 2σ（I）. The anion of 2 consists of a butterfly-shaped Mo2S4Au core in which one [AuPPh3]^＋ cation is coordinated by one bridging S and two terminal S atoms of the [（edt）2Mo2（S）2（μ-S）2] moiety. The Au（I） center adopts a pseudo-tetrahedral coordination geometry, and the Au-S bond lengths vary from 2.425（2） to 2.898（3）A^°.