平面四配位和五配位的B6S5团簇

采用B3LYP/def2-TZVP优化和在耦合簇方法(CCSD)单点水平下, 将$B_{6}S^{n}_{5}$ (n=0, +1, +2)作为基础结构研究证实了S原子对于形成B平面多配位结构具有良好的作用. 研究发现, $B_{6}S^{n}_{5}$ (n=0, +1, +2) 3种价态下最稳定和次稳定结构均为纯平面结构, 仅在不同电子数下两者的能量次序发生改变. 中性的B₆S₅因满足18电子规则其最稳定结构具有D_5h对称性, 且中心B为平面五配位. 在$B_{6}S^{+}_{5}$和$B_{6}S^{2+}_{5}$中, 其17电子和16电子时的最稳定结构中的所有B均为平面四配位. 18电子的B₆S₅更为稳定.     

包含两个平面五配位碳原子C_(2+n)B_(10-n)(n=0～10)团簇的结构的理论研究

采用B3LYP/6-311+G**方法,我们优化了初始构型中包含两个平面五配位碳原子(ppCs)的C2+nB10-n(n=0～10)团簇的结构并计算了它们的振动频率.计算结果表明,C2+nB10-n(n=0～2)团簇是稳定的,而且这三个结构中ppC—B键的Wiberg键级介于0.511～0.909之间,ppC—C键的Wiberg键级为0.2254(n=1)和0.8586(n=2),ppC的键级介于3.778到3.879之间,即这三个结构中存在两个ppCs,而且ppC遵循八隅规则;C2+nB10-n(n=3～6)团簇的最稳定结构包含一个ppC;C2+nB10-n(n6)团簇能量最低结构中不存在ppC.而且只有团簇C2+nB10-n(n=0～2)中没有悬键,它们的π电子数分别为:6,7和8,计算它们的NICS(0)值表明强芳香性一般位于局部的三元环中心,表明局部离域有利于平面结构的形成.C2+nB10-n(n=0～2)团簇的第一垂直激发能分别为:1.91,0.56和3.12eV.     

包含两个平面五配位碳原子C2＋nB10－n (n＝0～10)团簇的结构的理论研究

采用B3LYP/6-311＋G**方法, 我们优化了初始构型中包含两个平面五配位碳原子(ppCs)的C_{2＋nB10－n (n＝0～10)团簇的结构并计算了它们的振动频率. 计算结果表明, C2＋nB10－n (n＝0～2)团簇是稳定的, 而且这三个结构中ppC—B键的Wiberg键级介于0.511～0.909之间, ppC—C键的Wiberg键级为0.2254 (n＝1)和0.8586 (n＝2), ppC的键级介于3.778到3.879之间, 即这三个结构中存在两个ppCs, 而且ppC遵循八隅规则; C2＋nB10－n (n＝3～6)团簇的最稳定结构包含一个ppC; C2＋nB10－n (n＞6)团簇能量最低结构中不存在ppC. 而且只有团簇C2＋nB10－n (n＝0～2)中没有悬键, 它们的(电子数分别为: 6, 7和8, 计算它们的NICS(0)值表明强芳香性一般位于局部的三元环中心, 表明局部离域有利于平面结构的形成. C2＋nB10－n (n＝0～2)团簇的第一垂直激发能分别为: 1.91, 0.56和3.12 eV.}     

硅硫二元团簇(SiS2)-n(n=1-5)的结构和振动光谱的量子化学研究

用密度泛函(DFT)方法研究了硅硫团簇(SiS2)-n(n=1-5)的可能几何构型,并计算了相应的振动频率,得到稳定构型的振动光谱.比较其稳定构型可得到团簇的生长规律,由此可初步预测团簇的形成机理.     

B_n(BO)_n~(2-)、CB_(n-1)(BO)_n~-和C_2B_(n-2)(BO)_n(n=5~12):类似于笼状B_nH_n~(2-)、CB_(n-1)H_n~-和C_2B_(n-2)H_n的硼氧团簇

笼状硼氢化合物BnHn2-、CBn-1Hn-和C2Bn-2Hn(n=5~12)含n个顶点和(n+1)对骨架电子,具有典型的三维芳香性、高的芳香化能和类似于苯的化学反应性.2005年以来,在研究B-O二元团簇的过程中,我们首次提出硼的硼羰基化合物(boron boronyls)和碳的硼羰基化合物(carbon boronyls)的概念,探讨了Bn(BO)m0/-1/-2(n=1~2,m=2~4)及Cn(BO)n(n=3~7)系列化合物的几何结构和电子性质.基于高分辨光电子能谱实验和密度泛函理论分析,确认线性B(BO)20/-1及三角形B(BO)30/-1新颖结构,首次发现线性D∞h B2(BO)22-离子含有B≡B三重键.理论和实验结合研究表明,BO与H具有等瓣相似性,BO自由基具有类似于CN的化学行为.在此基础上,本文用BO基团取代BnHn2-、CBn-1Hn-及C2Bn-2Hn(n=5~12)中的H原子,形成Bn(BO)n2-、CBn-1(BO)n-及C2Bn-2(BO)n(n=5~12)系列硼氧化物,对其几何和电子结构、稳定性和芳香性进行密度泛函B3LYP/6-311+G(3df)理论研究.图1给出n=1...     

五原子平面四配位碳分子[CAl_3X]和[CAl_3X]~-(X=Sn,Pb)的理论研究

在B3LYP计算水平下,使用混合基组6-311+G(d)LANl2dz首次对含Sn,Pb的五原子平面四配位碳分子[CAl3X]和[CAl3X]-(X=Sn,Pb)两个体系(分别具有17和18价电子)的异构体结构及能量进行了量子化学计算研究,并与文献已经报道的[CAl3X]和[CAl3X]-(X=Si,Ge)作了比较.结果表明,具有平面四配位碳结构的异构体int1是能量的全局最小点.相对于17e的[CAl3X]体系来说,在得到一个电子以后形成18e的[CAl3X]-int1异构体在热力学上变得更稳定.本项研究将进一步丰富五原子平面四配位碳化学.     

五配位铁硫化合物(Et4N)4〔Fe2(S,X-C6H4-o)4〕的合成与晶体结构

利用无水FeCl与双齿配体Na_2BDT或Na_2MP(Na_2S,X-C,H_4-o_2:X=S,BDT;X=O,MP)在乙醇溶液中反应,然后加入沉淀剂Et_4NBr,可以得到双核铁硫化合物(Et_4N)_2[Fe_(S,X-CH_4-o)_4](1,X=S;2,X=0)。它们分别具有以双硫或双氧桥联起来的五配位扭曲三角双锥构型的铁原子。分子为心对称,核心Fe_2X_2~(2+)为平面。每个铁原子上的二个苯环平面A和B相互近于平行(1,二面角10.1°)或近于垂直(2,二面角100.2°);但铁原子与XSCC平面非共面。Fe原子离平面0.05～0.5A。2是第一个以双齿配位的双氧桥铁硫化合物,它既含有桥基氧原子又具有端基氧原子,对研究含氧配位的铁原子周围环境,为模拟固氧酶中的“P簇”,有一定意义。     

通过核独立化学位移(NICS)计算研究二价三、五、七元环C2H2M, C4H4M and C6H6M(M=C, Si, Ge, Sn and Pb)的芳香族特性

The aromatic character of divalent three, five and seven-membered rings C₂H₂M, C₄H₄M and C₆H₆M(M=C, Si, Ge, Sn and Pb) is investigated through magnetic and geometric criteria by Density Functional Theory (DFT)method using 6^-311++G(3df,2p) basis set of the GAUSSIAN 98 program. The result of Nucleus-independent Chemical Shifts (NICS)(0.5) calculations show an aromatic character for singlet state of C₂H₂M(M=C, Si, Ge, Sn and Sn) and nonaromatic character for triplet states of C₂H₂M(except M=Ge and Pb). NICS (0.5) calculations show nonaromatic character for the singlet state of C₄H₄C and antiaromatic character for C₄H₄M(M=Si, Ge, Sn and Pb). In contrast, NICS (0.5) calculations indicate antiaromatic character for the triplet state of C₄H₄C and nonaromatic character to C₄H₄M(M=Si, Ge, Sn and Pb). NICS (0.5) calculations show a slightly homoaromatic character for the singlet state of C₆H₆M and anti-aromatic character for triplet state of C₆H₆M.     

Structures and Aromaticity of Planar XY2Z （X = Li,K, Y - P,As and Z = C,Si, Ge） Clusters

Clusters XY2Z species are theoretically investigated with density functional theory （DFT） method. The results show that for LiP2C, LiAs2Ge and KAs2C species, the C2v isomer is the most stable planar structure, while for other species the Cs isomer is the most stable planar structure at the B3LYP/6-311＋G＊ level. Wiberg Bond Index （WBI） and Nucleus-Independent Chemical Shift （NICS） values indicate the existence of delocalization in stable planar structures. A detailed Molecular Orbital （MO） analysis further reveals that planar isomers of these species have strong aromatic character, which strengthens the structural stability and makes them closely connect with the concept of aromaticity.     

杂硼原子簇XB6+ (X=C,Si, Ge,Sn, Pb)的稳定性和芳香性

利用从头算MP2方法和密度泛函理论B3LYP和B3PW91方法, 研究了杂硼原子簇XB₆⁺ (X=C, Si, Ge, Sn, Pb)的结构、稳定性及化学键合情况. 对C, Si, Ge, B使用6-311+G(d)基组, 对Sn和Pb使用LANL2DZ赝势基组. 研究结果表明, 具有C_s对称性的假平面XB₆⁺ (X=C, Si, Ge, Sn, Pb)结构是势能面上的全域极小点, 其稳定性要高于C_6v对称性的锥形结构和C₂对称性的假锥形结构. 在B3LYP水平上, 对这些异构体的势能面的极小点进行了自然键轨道(NBO)的分析; 对最稳定构型的最高占据分子轨道(HOMO)和最低空轨道(LUMO)能级差、分子轨道(MO)和核独立化学位移(NICS)进行了计算和讨论. 分析了杂原子和硼原子间、相邻硼原子间的键合情况, 讨论了最稳定构型的芳香性质.     

The structures,thermochemistry, and electron affinities of hydrogenated silicon clusters Si6Hn/Si6H (n = 3–14)

The hydrogenated silicon clusters structures, electron affinities, and dissociation energies of the Si₆H_n/Si₆H (n = 3?14) species have been systematically investigated by means of three density functional theory (DFT) methods. The basis set used in this work is of double‐ζ plus polarization quality with additional diffuse s‐ and p‐type functions, denoted DZP++. The geometries are fully optimized with each DFT method independently. Three different types of energy separations presented in this work are the adiabatic electron affinity (EA_ad), the vertical electron affinity (EA_vert), and the vertical detachment energy (VDE). The first Si? H dissociation energies D_e (Si₆H_n→ Si₆H_n?1+H) for the neutral Si₆H_n and D_e (Si₆H→Si₆H+H) for the anionic Si₆H species have also been reported. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Structures and Aromaticity of Three-membered BeXP （X = C,Si, Ge） and CYP （Y = O,S, Se） Rings

Three-membered BeXP （X = C, Si, Ge） and CYP （Y = O, S, Se） rings are theoretically investigated using density functional theory （DFT） methods at the B3LYP/6-311＋G^＊ and B3PW91/6-311＋G^＊ levels of theory. The research results show that the size of atoms has a great influence on the structural stability of these species. The wiberg bond indexs （WBIs） suggest the existence of delocalization in these structures. Negative nucleus-independent chemical shift （NICS） values for these species indicate that a strong ring current exists in these three-membered structures （Cs symmetry）. A detailed molecular orbital （MO） analysis further reveals that a delocalized π MO strengthens the structural stability and makes these species show strong aromatic characters.     

Tetrel bonds between PhSiF3/PhTH3 (T = Si,Ge, Sn) and H3ZO (Z = N,P, As): A pentacoordinate silicon (IV) complex

The nature of the complexes PhTH₃ H₃ZO and PhSiF₃ H₃ZO (T = Si, Ge, and Sn; Z = N, P, and As) has been investigated at the MP2/aug’‐cc‐pVTZ(PP) level. These complexes are primarily stabilized by one T···O tetrel bond. Interaction energies of these complexes vary from 11 to 220 kJ/mol, and T···O separations from 1.89 to 3.09 Å. Charge transfer from the O lone pair into the C T and T H σ* antibonding orbitals leads to the stabilization of these complexes. The T···O tetrel bond between PhTH₃/PhSiF₃ and H₃NO exhibits a significant degree of covalence, characterized by the large interaction energy, negative energy density, and large charge transfer. Furthermore, a pentacoordinate silicon (IV) complex is formed in PhSiF₃ H₃NO with the Si···O distance almost close to the length of Si O bond. This indicates that the oxygen atom in N‐oxides shows a strong affinity to the silicon atom in organosilicon compounds.