Neue Azidokomplexe des Tantals(V). Synthese und Molekülstruktur der Zweikernverbindungen [Cp*TaCl(N3)(μ‐N3)]2(μ‐O) und [Cp*Ta(N3)3(μ‐N3)]2 (Cp* = Pentamethylcyclopentadienyl)

New Azido Complexes of Tantalum(V). Synthesis and Molecular Structure of the Dinuclear Compounds [Cp*TaCl(N₃)(μ‐N₃)]₂(μ‐O) and [Cp*Ta(N₃)₃(μ‐N₃)]₂ (Cp* = Pentamethylcyclopentadienyl) The reaction of Cp*TaCl₄ ( 1 ) with an excess of trimethylsilyl azide (Me₃Si–N₃) leads to azide‐rich dinuclear complexes which contain both terminal and bridging azido ligands. The oxo complex [Cp*TaCl(N₃)(μ‐N₃)]₂(μ‐O) ( 4 ) was formed in dichloromethane in the presence of traces of water, whereas [Cp*Ta(N₃)₃(μ‐N₃)]₂ ( 5 ) was obtained from boiling toluene after several days. According to the X‐ray structure determinations the Ta…Ta distance in 4 (314,5 pm) is considerably shorter than in 5 (382,2 pm).     

Zur Reaktion von Dichlorphenylboran mit Nitridokomplexen des Rheniums

The Reaction of Dichlorophenylborane with Nitrido Complexes of Rhenium BCl₂Ph reacts with terminal nitrido ligands of rhenium complexes under formation of a nitrogen bridge between the transition metal and boron. Structural studies on [Re(NBCl₂Ph)Cl₂(Ph₃P)₂], [Re(NBCl₂Ph)Cl₂(Me₂PhP)₃], [Re(NBCl₂Ph)Cl(Me₂PhP)₂(Et₂dtc)] and [Re(NBCl₂Ph)(Me₂PhP)(Et₂dtc)₂] (Et₂dtc^– = N,N′‐diethyldithiocarbamate) demonstrate that the rhenium‐nitrogen bond is only slightly lengthened upon the formation of the nitrido bridge whereas a significant decrease of the structural trans influence of the nitrido ligand is observed. [Re(NBCl₂Ph)Cl₄(Y)]^– (Y = Cl or solvent) complexes are formed during the reaction of [ReNCl₄]^– with BCl₂Ph. The rhenium(VI) compounds (d¹configuration) can easily be detected by EPR spectroscopy. The formation of {Re(NBCl₂Ph)} complexes with mixed Cl^–/Br^– (or NCS^–) coordination spheres is evident when the reactions start from [ReNBr₄]^– or [ReN(NCS)₅]^2– which can be derived from the EPR spectra of the reaction mixtures.     

Synthese und Strukturen von [ReNBr2(Me2PhP)3] und (Me2PhPH)[fac‐Re(NBBr3)Br3(Me2PhP)2]

Syntheses and Structures of [ReNBr₂(Me₂PhP)₃] and (Me₂PhPH)[ fac ‐Re(NBBr₃)Br₃(Me₂PhP)₂] [ReNBr₂(Me₂PhP)₃] ( 1 ) has been prepared by the reaction of [ReNCl₂(Me₂PhP)₃] with Me₃SiBr in dichloromethane. The bromo complex reacts with BBr₃ under formation of [Re(NBBr₃)Br₂(Me₂PhP)₃] ( 2 ) or (Me₂PhPH)[fac‐Re(NBBr₃)Br₃(Me₂PhP)₂] ( 3 ) depending on the experimental conditions. The formation of the nitrido bridge leads to a significant decrease of the structural trans influence of the nitrido ligand which is evident by the shortening of the Re‐(trans)Br bond from 2.795(1) Å in [ReNBr₂(Me₂PhP)₃] to 2.620(1) Å in [fac‐Re(NBBr₃)Br₃(Me₂PhP)₂]^– and 2.598(1) Å in [Re(NBBr₃)Br₂(Me₂PhP)₃], respectively.     

Nonlinear Assessment of Cable Vibration in a Stayed Bridge

An experimental study for cables in a stayed bridge is presented. In this analysis, the tensions on the cables were calculated considering linear and nonlinear approaches; for the nonlinear analysis a 2D model was used to evaluate vibration modes and responses under wind and traffic loads. The 8 semi-harp cable stayed bridge used for this study has 112 cables and vibration measurements were done under normal operational conditions. Tensions computed from the nonlinear model were compared with those from the traditional linear model, where average differences were within 3.3%. The estimated tensions from vibration tests have good correlation with the experimental values measured from load tests, while the vibration procedure was carried out in less than 2 days without limiting the bridge operation; converse to the load tests where approximately 30 days are necessary and the bridge traffic has to be closed for short periods during measurements.     

大跨度斜拉桥的动力特性及其颤振临界风速的计算

基于有限单元法理论,确定了斜拉桥合乎其构造特点的窨计算模型,建立了斜拉桥的自由振动的三维运动方程,对斜拉桥的动力特性进行了求解和分析,在此基础上,建立了在气动荷载作用下斜拉桥的三维运动方程,提出了用于分析斜拉桥颤振临界状态的子空间复特征值方法,推导出计算颤动临界风速的理论公式,并编写了用于计算斜拉桥颤振频率的多振型参与双参数自动搜索的计算机程序。     

矿物桥与珍珠母结构力学性能

本文通过对珍珠母材料的力学实验研究,定性地分析了矿物桥对珍珠母结构弹性模量以及与材料韧性相关的某些力学行为影响,由此说明在珍珠母材料所表现出来的宏观力学性能中矿物桥所起的重要作用．     

The Lewis basicity of nitrido complexes. Theoretical investigation of the structure and bonding of Cl2 (PH3)3ReN–X (X = BH3, BCl3, BBr3, AlH3, AlCl3, AlBr3, GaH3, GaCl3, GaBr3, O, S, Se, Te)

Quantum chemical calculations using gradient-corrected density functional theory (B3LYP) and ab initio methods at the MP2 level are reported for the geometries and bond energies of the nitrido complexes Cl₂ (PH₃)₃ReN–X (X = BH₃, BCl₃, BBr₃, AlH₃, AlCl₃, AlBr₃, GaH₃, GaCl₃, GaBr₃, O, S, Se, Te). The theoretical geometries are in excellent agreement with experimental values of related complexes which have larger phosphine ligands. The parent nitrido complex Cl₂(PH₃)₃ReN is a very strong Lewis base. The calculated bond dissociation energy of Cl₂(PH₃)₃ReN–AlCl₃ is D _e = 43.7 kcal/mol, which is nearly as high as the bond energy of Me₃N–AlCl₃. The donor-acceptor bonds of the other Cl₂(PH₃)₃ReN–AY₃ complexes are also very strong. Even stronger N–X bonds are predicted for most of the nitrido-chalcogen complexes, which exhibit the trend X = O ≫ S > Se > Te. Analysis of the electronic structure shows that the parent compound Cl₂(PH₃)₃ReN has a Re–N triple bond. The Re–N σ bond is clearly polarized towards nitrogen, while the two π bonds are nearly nonpolar. The Re–N σ and π bonds become more polarized toward nitrogen when a Lewis acid or a chalcogen atom is attached. Bonding in AY₃ complexes should be described as Cl₂(PH₃)₃ReE≡N→AY₃, while the chalcogen complexes should be written with double bonds Cl₂(PH₃)₃Re=N=X. The charge-decomposition analysis indicates that the nitrogen-chalcogen bonds of the heavier chalcogen complexes with X = S, Se, Te can also be interpreted as donor-acceptor bonds between the nitrido complex acting as a Lewis base and the chalcogen atom with an empty p(σ) orbital acting as a Lewis acid. The nitrido oxo complex Cl₂(PH₃)₃ Re=N=O has a covalent N–O double bond. Received: 27 July 1998 / Accepted: 26 October 1998 / Published online: 16 March 1999     

三氮唑配合物[Cu2(CH3COO)4(C4H8N4)2]·2CH3CN的合成及晶体结构

Cu(CH3COO)2 和4 氨基 3,5 二甲基 1,2,4 三氮唑反应制得标题化合物的单晶[Cu2(CH3COO)4(C4H8N4)2]·2CH3CN。晶体属三斜晶系 ,空间群 ,a=8.266(2),b=8.585(2),c=10.741(2) ,α=75.58(3),β=88.46(3),γ=86.35(3)°,V=736.7(3) 3 ,Z=1,Dc=1.509g·cm 3,F(000)=346,μ=1.502mm 1 。X 射线衍射结构分析表明 ,Cu2(CH3COO)4(C4H8N4)2 单元是中心对称的双核配合物 ,两个铜原子间距为2.698 。每个金属原子被围成四方锥的配位结构 ,四个乙酸根配体中最近的四个氧原子处在底面上[Cu O=1.965(3)～1.986(3) ] ,一个4 氨基 3,5 二甲基 1,2,4 三氮唑配体位于顶点位置Cu N=2.172 。