13顶点金属碳硼烷结构和非线性光学性质的DFT研究

采用量子化学密度泛函理论(DFT)B3LYP/6-31G(d)方法,对4,1,6-MC2B10H1213顶点金属碳硼烷几何构型进行优化,结合有限场(FF)方法计算了它们的极化率和二阶非线性光学(NLO)系数.结果表明,十个13顶点金属碳硼烷分子中1a～6a的二阶NLO系数与其构型纵向扩张呈现相同的规律.分子的前线分子轨道能级差越小,其二阶NLO系数越大.对于不同自旋态的同种金属碳硼烷分子,其偶极矩值为高自旋态大于相应的低自旋态,极化率和二阶NLO系数与自旋多重度没有一致的对应规律,自旋多重度对NLO性质影响不大.     

7,10,12顶点Fe(Ⅱ)碳硼烷夹心配合物NLO性质的DFT研究

采用密度泛函理论(DFT)CAM-B3LYP方法对系列7,10,12顶点Fe(Ⅱ)碳硼烷与1,2,4,5-Me4C6H2(dur1),1,2,3,4-Me4C5H(dur2)形成的夹心配合物的非线性光学(NLO)性质进行了计算分析.结果表明,Fe(Ⅱ)碳硼烷的顶点数和硝基的取代位置影响分子的几何构型,从而影响分子的NLO性质;Fe(Ⅱ)碳硼烷夹心配合物的偶极矩与极化率随碳硼烷的顶点数增加而增大;10顶点Fe(Ⅱ)碳硼烷分子的前线分子轨道能级差较小,其第一超极化率βtot值大于12及7顶点Fe(Ⅱ)碳硼烷分子;硝基与Fe(Ⅱ)处于对位时,其βtot值大于未取代分子;硝基与Fe(Ⅱ)处于邻位时,βtot值较未取代分子小;在此类Fe(Ⅱ)碳硼烷夹心配合物中,碳硼烷既可以作电子给体,也可以作电子受体.     

氟代十二顶点碳硼烷结构和非线性光学性质的理论研究

采用密度泛函理论(DFT)方法,计算并分析了四氟取代十二顶点碳硼烷及其衍生物的结构和非线性光学(NLO)性质.结果表明,改变四氟碳硼烷取代基的共轭性或给吸电子能力,会使分子中碳硼笼原子间距离发生改变.碳硼烷取代基的给吸电子能力越强,其偶极矩越大.分子极化率随取代基共轭性和体积的增加而增大.引入强吸电子基或增加四氟碳硼烷取代基的共轭性,可使其二阶NLO响应明显增强.通过分析分子的电子光谱和对应的分子轨道组成可知,第一超极化率最大的分子4a’发生碳硼笼到并苯取代基的电荷转移.     

二芳基氨(硼)-π-碳硼烷三元化合物的二阶非线性光学性质的理论研究

采用密度泛函理论(DFT)方法对二芳基氨(硼)-π-十二顶点碳硼烷三元化合物的结构及二阶非线性光学(NLO)性质进行计算.结果表明,化合物共轭桥长度及二芳基氨(硼)对化合物偶极矩的影响较小.随着分子共轭桥的增长,分子的电子空间范围R2增大,从而使极化率和第一超极化率增大.通过分析化合物的电子光谱和对应的分子轨道组成可知,分子中电荷转移主要发生在二芳基氨(硼)和π-桥之间,碳硼烷的贡献较少.二芳基氨和二芳基硼的供电子能力差异可以调节分子的二阶NLO响应.     

钯催化硼-碳和硼-杂原子键构建一锅法合成双官能团化邻-碳硼烷※

碳硼烷是由碳氢和硼氢顶点组成的笼状分子, 在医药、能源和材料等领域有着重要应用, 但目前在碳硼烷硼顶点引入杂原子取代基的方法还较为有限. 基于此, 本工作从3-碘-邻-碳硼烷出发, 通过钯催化烯基化、金属迁移及后续与杂原子亲核试剂的偶联反应, 一锅法构筑硼碳键和硼杂原子键, 成功实现了一系列新型3-烯基-4-胺基/烷氧基/烷(芳)硫基-邻-碳硼烷衍生物的合成.     

过渡金属催化硼-氢键活化合成含硼-杂原子键邻碳硼烷衍生物的研究进展

十二顶点碳硼烷是一类含有碳、氢及硼原子的簇合物,具有特殊的热稳定性和化学稳定性,在医药、材料、能源、配位化学及金属有机化学中都得到广泛的应用.近年来,过渡金属催化的碳硼烷直接硼-氢键活化发展迅速,为硼顶点选择性官能团化提供了一系列新的高效路径.总结了利用过渡金属催化硼-氢键活化策略来实现邻碳硼烷硼-硼、硼-氮、硼-氧、硼-硫及硼-卤键构建的研究进展,同时对部分反应机理进行了讨论,并就该研究领域所面临的挑战和发展前景进行了展望.     

碳硼烷和碳硼炔金属配合物中金属-碳键的化学性质

碳硼烷和碳硼炔金属配合物中的金属-碳键具有不同于经典金属-碳键的化学性质.一方面,二十面体碳硼烷独特的电子和空间效应使得碳硼烷金属配合物中的金属-碳键不参与和不饱和分子的反应 另一方面,在一定条件下具有大空间位阻的碳硼笼可以诱导某些碳-碳偶联反应.然而,碳硼炔金属配合物中的金属-碳键能与多种不饱和分子发生反应,其反应模式取决于中心金属离子的电子构型.本文简要总结了我们近期在这方面的研究进展.     

碳硼烷硼端衍生物的合成与表征

在路易斯酸催化下,碳硼烷分别与对氰基溴化苄、三苯基膦在甲苯溶液里回流,前者反应中,制备得碳硼烷的硼端与对氰基苄基中的亚甲基直接偶联的产物1,通过调整催化剂的含量,可以显著地提高含B-Cl键的产物2的产率;与三苯基膦的反应中,碳硼烷失去一个硼顶,并与三苯基膦中的P原子直接偶联,生成含B-P键的巢式碳硼烷衍生物3。对此两类化合物进行了核磁、质谱、红外及单晶衍射等表征。化合物1和2中均发现碳硼烷的CH与N形成CH…N氢键和CH…π的弱作用,其中化合物2中,还存在CH…Cl。在巢式化合物3中,发现碳硼烷的CH参与了罕见的CH…HC相互作用。这类反应成功合成了含有B-C、B-Cl、B-P键的碳硼烷衍生物。     

碳硼烷硼顶点选择性亲核取代反应

碳硼烷是一类由两个碳氢及十个硼氢顶点组成的笼状分子,在医学、材料、配位化学和金属有机化学等领域都有重要的应用,因此发展高效、简便的方法高选择性获取碳硼烷官能化衍生物具有重要的理论和现实意义.近年来,通过亲电取代、过渡金属催化、亲核取代等策略,实现了碳硼烷硼–氢键高效、高选择性官能化.本文根据硼–氢键的不同反应位点,评述了利用亲核取代反应策略进行碳硼烷选择性官能团化的研究进展,详细讨论了反应底物普适性、选择性控制及反应机理,并对该领域后续研究所面临的挑战和发展前景进行了展望.     

碳十硼烷及其衍生物的反应性及应用

碳十硼烷(C₂B₁₀H₁₂)是由2个C原子和10个B原子组成的二十面体笼状结构大分子,有邻位、间位和对位三种异构体。碳十硼烷庞大的体积以及类芳香族三维刚性结构使它具有优异的高温稳定性和化学稳定性,良好的溶解性使其具有广泛而灵活的应用。本文总结了近年来碳十硼烷和碳十硼烷衍生物在C原子、B原子上的化学反应性以及在环加成和金属络合方面的研究。另外,由于碳十硼烷衍生物特殊的立体结构,优异的耐高温性、热氧化性及高硼含量,本文综述了碳十硼烷衍生物近年来在功能材料、催化剂及生物医药等多个领域的应用进展。     

An octanuclear coordination cage with a 'cuneane' core--a topological isomer of a cubic cage

The octanuclear coordination cage [Ni(8)(L(14Naph))(12)](BF(4))(16) has the core structure of a 'cuneane'--a toplogical isomer of a cube--with a metal ion at each of the eight vertices and bridging ligand spanning each of the twelve edges; this is the only possible 8-vertex polyhedron other than a cube that will form a cage in which each metal is connected to three others.     

Macropolyhedral boron-containing cluster chemistry. The reaction of B16H20 and B14H18 with [PtMe2(PMe2Ph)2] to give [(PMe2Ph)2PtB16H17Me] and [(PMe2Ph)2PtB14H16

Structurally characterised 17-vertex [(PMe2Ph)2PtB16H17Me] 3 is obtained, albeit in low yield, by platination of 16-vertex B16H20 1 using [PtMe2(PMe2Ph)2] under mild conditions. Platination has occurred on the {B10} subcluster of 1, interesting in that B16H20 itself deprotonates on the {B8} subcluster: the reference 16-vertex [B16H19]- anion 1a, prepared by deprotonation of 1 with 1,8-bis(dimethylamino)naphthalene, is also structurally characterised. [PtMe2(PMe2Ph)2] with 14-vertex B14H18 2 similarly gives a low yield of 15-vertex [(PMe2Ph)2PtB14H16] 5, of formulation and structure substantiated by DFT calculations.     

Synthesis, structure, and reactivity of 13-vertex carboranes and 14-vertex metallacarboranes

Syntheses, properties, and synthetic applications of 13-vertex closo- and nido-carboranes are reported. Reactions of the nido-carborane salt [(CH2)3C2B10H10]Na2 with dihaloborane reagents afforded 13-vertex closo-carboranes 1,2-(CH2)3-3-R-1,2-C2B11H10 (R = H (2), Ph (3), Z-EtCH=C(Et) (4), E-(t)BuCH=CH (5)). Treatment of the arachno-carborane salt [(CH2)3C2B10H10]Li4 with HBBr2.SMe2 gave both the 13-vertex carborane 2 and a 14-vertex closo-carborane (CH2)3C2B12H12 (8). On the other hand, the reaction of [C6H4(CH2)2C2B10H10]Li4 with HBBr2.SMe2 generated only a 13-vertex closo-carborane 1,2-C6H4(CH2)2-1,2-C2B11H11 (9). Electrophilic substitution reactions of 2 with excess MeI, Br2, or I2 in the presence of a catalytic amount of AlCl3 produced the hexa-substituted 13-vertex carboranes 8,9,10,11,12,13-X6-1,2-(CH2)3-1,2-C2B11H5 (X = Me (10), Br (11), I (12)). The halogenated products 11 and 12 displayed unexpected instability toward moisture. The 13-vertex closo-carboranes were readily reduced by groups 1 and 2 metals. Accordingly, several 13-vertex nido-carborane dianionic salts [nido-1,2-(CH2)3-1,2-C2B11H11][Li2(DME)2(THF)2] (13), [[nido-1,2-(CH2)3-1,2-C2B11H11][Na2(THF)4]]n (13a), [[nido-1,2-(CH2)3-3-Ph-1,2-C2B11H10][Na2(THF)4]]n (14), [[nido-1,2-C6H4(CH2)2-1,2-C2B11H11][Na2(THF)4]]n (15), and [nido-1,2-(CH2)3-1,2-C2B11H11][M(THF)5] (M = Mg (16), Ca (17)) were prepared in good yields. These carbon-atom-adjacent nido-carboranes were not further reduced to the corresponding arachno species by lithium metal. On the other hand, like other nido-carborane dianions, they were useful synthons for the production of super-carboranes and supra-icosahedral metallacarboranes. Interactions of 13a with HBBr2.SMe2, (dppe)NiCl2, and (dppen)NiCl2 gave the 14-vertex carborane 8 and nickelacarboranes [eta5-(CH2)3C2B11H11]Ni(dppe) (18) and [eta5-(CH2)3C2B11H11]Ni(dppen) (19), respectively. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray diffraction studies.     

Flattening of rhodium vertices in mixed rhodium-nickel carbonyl clusters: relationships to borane and zintl ion structures

The flattened deltahedra and related polyhedra found in hypoelectronic bare group 13 metal cluster anions are also found in some anionic mixed rhodium-nickel carbonyl clusters. In all cases the rhodium vertices rather than the nickel vertices are involved in the flattening process so that the rhodium vertices contribute four internal orbitals and the nickel vertices three internal orbitals to the skeletal bonding of the cluster. Thus, the 11-vertex cluster Rh(5)Ni(6)(CO)(21)(3-) has a D(3h) triflattened pentacapped trigonal prismatic structure similar to that found in the In(11)(7-) anion of the intermetallic K(8)In(11). Similarly the polyhedra in the 11-vertex cluster RhNi(10)(CO)(19)(3-) and the 9-vertex cluster Rh(3)Ni(6)(CO)(17)(3-) are both derived from a 10-vertex isocloso polyhedron by capping (for RhNi(10)(CO)(19)(3-)) or vertex removal (for Rh(3)Ni(6)(CO)(17)(3-)) followed by flattening all of the rhodium vertices. A D(3h) icosahedron with flattened rhodium vertices is found in the 12-vertex cluster Rh(3)Ni(9)(CO)(22)(3-).     

十二顶点邻位双取代碳硼烷衍生物二阶NLO性质的理论研究

采用密度泛函理论(DFT) B3LYP/6-31G*方法, 对系列十二顶点邻位双取代碳硼烷(C2B10H12)衍生物的几何构型进行优化. 在所得优化结构的基础上, 结合有限场方法(FF)和含时密度泛函理论(TD-DFT)对这些分子的二阶非线性光学(NLO)活性及电子吸收光谱进行了研究. 结果表明, 邻位双取代碳硼烷有较强的吸电子作用, 与有机基团形成D-π-A结构时, 可以起到很好的受体作用. 当给体部分或桥的共轭性好, 给体的给电子能力强时, 邻位双取代碳硼烷的吸电子作用更明显, 从而增强了分子的二阶NLO响应.     

Supraicosahedral polyhedra in carboranes and metallacarboranes: The role of local vertex environments in determining polyhedral topology and the anomaly of 13-vertex closo polyhedra

Metal-free carboranes having 13 vertices are anomalous since their closo polyhedra having the expected 28 skeletal electrons are not the usual deltahedra with exclusively triangular faces but instead polyhedra with one or two trapezoidal faces obtained by removal of one or more edges from the corresponding 13-vertex deltahedron. Removal of such edges converts degree 6 boron vertices in the 13-vertex deltahedron into more favorable degree 5 boron vertices while lowering the degree of nearby carbon vertices. Thus the anomaly of the 13-vertex carborane closo polyhedron can be rationalized by the preference of boron for degree 5 vertices. The 12-vertex tetracarbon carborane (CH₃)₄C₄B₈H₈ with a nido electron count of 28 skeletal electrons but with two quadrilateral faces has a solid state structure derived from a 13-vertex “closo” polyhedron with one quadrilateral face by removal of a degree 4 vertex to give the second quadrilateral face. However, the corresponding tetraethyl derivative (C₂H₅)₄C₄B₈H₈ has a different solid state structure derived from removal of a degree 6 vertex from an unusual 13-vertex deltahedron with three degree 6 vertices to give an open hexagonal face rather than two quadrilateral faces. In contrast to the 13-vertex closo polyhedra, the 14-vertex closo polyhedron is a true deltahedron, namely the D_6d bicapped hexagonal antiprism, which is found in a carborane derivative as well as in several dimetallacarboranes with the metal atoms always at the degree 6 vertices. However, the 15-vertex closo polyhedron, so far found only in the metallaborane 1,2-μ-(CH₂)₃C₂B₁₂H₁₂Ru(η⁶-p-cymene), is a non-deltahedron with one quadrilateral face.     

Polyhedral monocarbaborane chemistry. Some C-phenylated seven, eight, nine, ten, eleven and twelve-vertex species

Some synthetic and structural systematics for monocarbaboranes, using the C-phenylated motif as the example, are investigated. The 10-vertex [6-Ph-nido-6-CB(9)H(11)](-) anion 1, from reaction of PhCHO with B(10)H(14) in KOH/H(2)O, is a useful entry synthon into C-phenyl monocarbaborane chemistry. Treatment of anion 1 with Na/thf yields the 10-vertex [1-Ph-closo-1-CB(9)H(9)](-) anion 2a, whereas treatment of anion 1 with iodine in alkaline solution yields the isomeric 10-vertex [2-Ph-closo-2-CB(9)H(9)](-) anion 2b, which isomerises quantitatively to 2a on heating under reflux in DME. Thermolysis of anion 1 yields the 9-vertex [4-Ph-closo-4-CB(8)H(8)](-) anion 5, whereas treatment of anion 1 with FeCl(3)/HCl gives neutral 9-vertex [4-Ph-arachno-4-CB(8)H(13)] 3. Compound 3 gives neutral 9-vertex [1-Ph-nido-1-CB(8)H(11)] 4 in refluxing toluene, and gives the 7-vertex [2-Ph-closo-2-CB(6)H(6)](-) anion 7 and the 8-vertex [1-Ph-closo-1-CB(7)H(7)](-) anion 6 in refluxing toluene with NEt(3). Reaction of 1 with [BH(3)(thf)] yields the 11-vertex [7-Ph-nido-7-CB(10)H(12)](-) anion 8 which can be converted to the 12-vertex [1-Ph-closo-1-CB(11)H(11)](-) anion 10 using [BH(3)(SMe(2))]; alternatively, anion 1 yields anion 10 directly on treatment with [BH(3)(NEt(3))]. Treatment of anion 8 with I(2)/KOH yields the 11-vertex [2-Ph-closo-2-CB(10)H(10)](-) anion 9. The structures of anions 1, 2a, 2b, 5, 6, 7, 8, 9 and 10 have been established by single-crystal X-ray diffraction analyses of their [NEt(4)](+) salts, and those of neutral 3 and 4 estimated by DFT calculations at the B3LYP/6-31G* level; similar calculations have also been applied to the new anionic closo species 2a, 2b, 5, 6, 7, 9 and 10. Crystals of the [NEt(4)](+) salt of the [2-Ph-closo-2-CB(6)H(6)](-) anion 7 required synchrotron X-radiation for sufficient diffraction intensity for molecular-structure elucidation. The syntheses are in principle generally applicable to give extensive derivative C-aryl and C-alkyl chemistries.     

Structural increment system for 11-vertex nido-boranes and carboranes

An increment system forming a set of quantitative rules that govern the relative stabilities of 11-vertex nido-boranes and carboranes is presented. Density functional theory computations at the B3LYP/6-311+G//B3LYP/6-31G level with ZPE corrections were carried out for 61 different boron hydride and carborane structures from [B(11)H(14)](-) to C(4)B(7)H(11) to determine their relative stabilities. Disfavored structural features that destabilize a cluster structure relative to a hypothetical ideal situation were identified and weighted by so-called energy penalties. The latter show additive behavior and allow us to reproduce (within 5 kcal mol(-)(1)) the DFT computed relative energies. Energy penalties for four structural features, i.e., adjacent carbon atoms, CC, a hydrogen atom bridging between a carbon and a boron atom, CH-B, an endo-terminal hydrogen atom at an open face carbon atom, CH(2) and an endo-H between two carbon atoms, C(BH(2))C for the 11-vertex nido-cluster are quite similar to those reported for the 6-vertex nido-cluster, thus showing a behavior independent of the cluster size. Hydrogen structural features, however, vary strongly with the cluster size. Two unknown 11-vertex nido-carboranes were identified which are thermodynamically more stable than known positional isomers.     

The relative stabilities of 11-vertex nido- and 12-vertex closo-heteroboranes and -borates: facile estimation by structural or connection increments

The relative thermodynamic stabilities of ortho-, meta- and para-isomers of 12-vertex closo-heteroboranes and -borates with different p-block heteroatoms were determined using density functional theory. More electronegative (smaller) heteroatoms tend to occupy non-adjacent, whereas less electronegative (larger) heteroatoms tend to occupy adjacent vertices in the thermodynamically most stable closo-diheterododecaborane isomers. The computed relative stabilities agree perfectly with experimental observations. The energy differences of para- and meta- relative to ortho-isomers of 12-vertex closo-heteroboranes generally depend on the extent of electron localization by a given heteroatom and show highly periodic trends, i.e. increase along the period and decrease down the group. The energy penalties for the HetHet structural feature (two heteroatoms adjacent to each other) for the 12-vertex closo-cluster are apparently significantly different from those for the 11-vertex nido-cluster. Reformulating two 11-vertex nido-structural features, i.e. Het(5k)(2) and HetHet, in terms of connection increments along with the additional structural feature HetHet(m) give the relative stabilities of various isomeric 11-vertex nido- as well as 12-vertex closo-heteroboranes and -borates, using one unique set of increments.     

Substituents effect on molecular structures of 13-vertex closo-metallacarboranes of rare earths. Synthesis and structural characterization of metallacarboranes bearing nido- and arachno-carborane ligands

Several new 13-vertex closo-metallacarboranes of rare earths incorporating nido- and arachno-carborane ligands have been prepared and structurally characterized. They represent a new class of metallacarboranes bearing a η⁷-carboranyl ligand recently discovered in our laboratory. This work indicates that the substituents on carborane cage carbons may affect the overall molecular structures of the resultant 13-vertex closo-metallacarborane complexes, but have little influence on the interactions between the central metal ion and nido- or arachno-carborane ligand.