D_(3d)[E_3ME_3]~(2-)(E=P,As;M=Ni,Pd,Pt):含η~3-P_3~-和η~3-As_3~-配体的最小无机三明治配合物

C4H42-、C5H5-(Cp-)及C6H6(Ar)等有机配体可以与过渡金属形成典型的三明治夹心化合物.作为CH的等电子体,P可以取代CH与过渡金属形成混合型三明治配合物,例如:CpNiP3,CpFeP5,[CpMPnMCp]等.2002年,Schleyer等首次成功地合成了以η5-P5-为配体的不含碳的无机三明治配合物[P5TiP5]2-;2007年,Chen等采用密度泛函方法预测了含P4四元环的[P4MP4]n-三明治结构.本文采用密度泛函和从头计算方法首次系统地研究了含η3-P3-和η3-As3-三元环配体的过渡金属三明治配合物D3d[E3ME3]2-(E=P,As;M=Ni,Pd,Pt)(图1),对该系列化合物进行了结构优化、频率分析、自然轨道分析和光谱性质预测.结果表明,三元环状P3-和As3-与五元环状P5-和As5-具有类似的芳香性,可能作为新颖配位形成一大类过渡金属夹心化合物.[E3ME3]2-满足18电子规则,交错型单重态D3d[E3ME3]2-是该七原子体系的全局极小,而重叠型单重态D3h[E3ME3]2-在能量上略高(2.0kcal/mol),其他二维和三维结构则远非稳定(24kcal/mol).作为体系的全局极小,D3d[E3ME3]2-是在实验上可能合成的最小无机三明治夹心结构.在[E3ME3]2-系列配合物中,配位中心M携带的电荷为+0.07|e|～+0.27|e|,Wiberg键级为1.84～2.22;配体E原子携带的电荷为-0.35|e|～-0.38|e|,Wiberg键级为2.93～2.98.配体原子间以单键(WBIE-E=1.03-1.07),配体E和配位中心M间的Wiberg键级为WBIM-E=0.31-0.37,体现典型的配位成键特点.显然,与实验已知的[P5TiP5]2-类似,在[E3ME3]2-体系中配位中心M向配体E3发生了部分电荷转移,E3三元环表现为电子受体.轨道分析表明,该夹心化合物体系存在典型的离域π键(图1).体系存在较大NICS(-18.1～-24.8ppm),表明其芳香性本质.引进Li+阳离子可以有效稳定[E3ME3]2-二价阴离子,形成含交错型Cs[E3ME3]Li-和C2h[E3ME3]Li2.Cs[E3ME3]Li-的第一计算电子剥离能介于2.7～2.9eV,位于355nm激发光能量(3.496eV)范围之内.     

D3d[E3ME3]^2-（E=P,As;M=Ni,Pd,Pt）：含η^3-P3^-和η^3-As3^-配体的最小无机三明治配合物（摘要）

C4H42^-、C5H5^-（Cp^-）及C6H6（Ar）等有机配体可以与过渡金属形成典型的三明治夹心化合物.作为CH的等电子体,P可以取代CH与过渡金属形成混合型三明治配合物,例如：CpNiP3,CpFeP5,[CpMPnMCp]等.2002年,Schleyer等首次成功地合成了以η5-P5-为配体的不含碳的无机三明治配合物[P5TiP5]^2-;2007年,Chen等采用密度泛函方法预测了含P4四元环的[P4MP4]^n-三明治结构.     

三核过渡金属配合物[M3ⅢO(OOCR)6L3]+(M=Cr,Fe,Mn;R=CH3,C2H5,CH2NH2;L=C5H5N,H2O)的1H NMR性质

采用1H NMR谱研究了通式为[M3ⅢO(OOCR)6L3]+(M=Cr,Fe,Mn;R=CH3,C2H5,CH2NH2;L=C5H5N,H2O)的一系列氧心三核过渡金属配合物,主要考察其1H化学位移随金属、配体、温度、溶剂等因素变化而变化的规律.结果表明,骨架金属对化学位移的影响最大,M3O中的3个金属离子间存在反铁磁交换相互作用.对Mn配合物中顺磁中心对化学位移和线宽的影响机制的研究表明,其1H各向同性位移主要由接触作用贡献.     

IB 族金属-乙烯配合物[N{(Me)C(Ph)N}2]M-C2H4 (M=Cu,Ag, Au)的电子结构

采用从头算Hartree-Fock(HF),M??ller-Plesset微扰(MP2),二级近似耦合簇(CC2)和密度泛函理论(DFT)方法,对IB族金属-乙烯配合物LM-C2H4(L=[N{(Me)C(Ph)N}2];M=Cu,Ag,Au)的几何结构、电子结构以及LM与C2H4之间的结合能进行了理论研究.MP2、CC2和密度泛函方法对C2H4配位前后C=C键长的变化情况都给出了正确的描述.电子结构分析显示LM与C2H4之间主要以C2H4→LM"σ-给予"和LM→C2H4"π-反馈"方式协同成键,这种成键方式使C2H4配体π轨道上的电子密度下降,π*轨道上的电子密度增加,并使得C=C键长增加、键能下降,从而达到活化C=C键的目的.自然电荷布居和能量分解分析显示LM-C2H4中的"σ-给予"作用弱于"π-反馈"作用,若使用"σ-给予"作用强于"π-反馈"作用的M+-C2H4体系作为LM-C2H4的简化模型进行理论研究是不合适的.LM-C2H4中金属原子M的改变对C=C键长、C2H4电荷布居以及LM与C2H4之间的结合能等性质影响显著.LAu与LCu、LAg相比其接受和反馈电子的能力最强,使C2H4配体π轨道电子密度减少的程度和π*轨道电子密度增加的程度也最大,因此LAu对C2H4中C=C键的活化效果最好.螯合配体取代基供、吸电能力的改变对上述性质的影响则非常有限.     

金属串配合物[Cr3(dpa)4LL?](dpa=dipyridylamide;L, L?=Cl, BF4, CCPh)的Cr―Cr成键特性

采用密度泛函理论 UBP86方法计算了 Cr3(dpa)4Cl2(1)、 Cr3(dpa)4(BF4)2(2)、 Cr3(dpa)4 Cl(BF4)(3)、Cr3(dpa)4(CCPh)2(4)和Cr3(dpa)4Cl(CCPh)(5)金属串配合物的结构,并对配合物的构型、 Cr―Cr键的本质以及轴向配体对Cr―Cr键的影响进行了研究.结果表明:(1) Cr―Cr平均键长较长的配合物趋于形成对称构型,较短时趋于形成非对称构型,最稳定的五重态的Cr―Cr平均键长最长,故优化时趋于形成对称构型;七重态Cr―Cr平均键长最短,趋于形成非对称构型;(2)五重态的Cr36+金属链均存在三中心三电子σ键,含弱σ给电子轴向配体BF4-的2和3的Cr―Cr短键还具有弱的π相互作用.七重态下,对称构型4中仅有三中心三电子σ键,而非对称构型1-3、5的Cr―Cr短键为三重键,非对称构型存在Cr36+链的σ离域作用,仍具有分子导线的潜在应用;(3)轴向配体L与Cr的作用主要表现为nL→4sCr或nL→3dz2Cr离域,较强的σ给电子配体CCPh-还存在σC―C→4sCr离域. Cr与L的结合强度为2<3<1<5<4, CCPh-与Cr的结合最强,使Cr―Cr键减弱, Cr―Cr距离增长,故4的各自旋态均为对称构型.     

钛锆钒异核双金属配合物[Cp2V(μ-η2:η4-PhC4Ph)MCp2′](M=Ti,Zr; Cp′=C5H5,C5H4SiMe3)的合成与表征

室温下, [Cp2Ti(C≡CPh)2], [Cp2Zr(C≡CPh)2]和[(C5H4SiMe3)2Zr(C≡CPh)2]分别与二茂钒作用, 合成了[Cp2V(μ-η2∶η4-PhC4Ph)MCp2′] (1, M=Ti, Cp′=C5H5; 2, M=Zr, Cp′=C5H5; 3, M=Zr, Cp′=C5H4SiMe3). 用元素分析、质谱、核磁共振谱、磁矩、红外和拉曼光谱对配合物进行了表征. 3个配合物具有相似的磁化率, 配合物3的晶体结构分析表明PhC4Ph通过内部2个碳原子键合到Cp2V上, 内部2个碳原子和外部2个碳原子均与Cp2′Zr键合, 丁二烯骨架内部的2个碳原子都具有四配位的平面结构.     

E_4~(2-),[CoE_4]~+和[P_4CoE_4]~-(E=N～Bi)结构和芳香性的理论预测

用密度泛函理论杂化密度泛函B3LYP方法研究了E24-,[CoE4]+和[P4CoE4]-(E=N,P,As,Sb,Bi)几何结构、键能及芳香性.结果表明,E42-,[CoE4]+和[P4CoE4]-的基态结构分别具有D4h,C4v和C4v(交错型)对称性.三明治配合物中,金属与配体间存在σ,π和δ三种成键方式,P4与E4间相互影响较小.E4对P4中的P—P键长影响随着N,P,As,Sb,Bi顺序逐渐变长,中心Co离子与E4间的键合能随N,P,As,Bi,Sb的顺序增大.N42-的环外具有弱芳香性,其它E42-环中心及环外均为反芳香性.除[CoN4]+外,其它[CoE4]+中的E4环均具有较强的中心和内芳香性及弱的外反芳香性.[P4CoE4]-中的P4和E4均具有较大的中心、内和外芳香性,且P4环芳香性随N,P,As,Sb,Bi顺序逐渐递增.     

Cp_2M_2(μ-B_4N_4H_8)(M=V,Cr,Mn,Fe)金属多重键成键性质的理论研究

对金属多重键配合物Cp2M2(μ-B4N4H8)(M=V,Cr,Mn,Fe)的结构和成键进行了理论研究,并与Cp2M2(μ-C8H8)进行对比.计算结果表明,在Cp2M2(μ-B4N4H8)基态构型中,B4N4H8配体均以硼为桥原子,金属原子的配位数均为5.其中,Cp2M2(μ-B4N4H8)(M=V,Cr,Mn)基态的结构和成键都与Cp2M2(μ-C8H8)非常接近;而Cp2Fe2(μ-B4N4H8)基态结构与Fe为4配位的Cp2Fe2(μ-C8H8)有所不同.Cp2M2(μ-B4N4H8)(M=V,Cr,Mn,Fe)基态结构分别为含V-V三重键的三态、含Cr-Cr三重键的单态、含Mn-Mn双键的三态及含Fe-Fe单键的单态.     

[η~5:σ-Me_2C(C_5H_4)(C_2B_(10)H_(10))]Ru(NCCH_3)_2与中间炔的反应——钌环丁二烯和钌杂环戊三烯配合物的合成与结构

钌可以促使炔烃通过亚乙烯基钌卡宾金属配合物或钌金属杂环配合物的形式发生碳-碳偶联反应,它的化学性质很大程度上取决于配体的电子和立体特征.普通环戊二烯基钌配合物可以促使炔烃三聚生成苯环衍生物或使两分子炔烃和一分子含C=X键(X=C,O,S,N等)的不饱和底物发生环加成反应得到杂环化合物.含桥联碳硼烷-环戊二烯基配体的钌乙腈配合物[η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NCCH3)2(1)表现出与环戊二烯基钌不同的反应性质.例如,配合物1与三甲基硅基取代的端炔或中间炔反应可生成含有单或双亚乙烯基有机钌卡宾配合物;与末端芳炔则通过三分子炔和桥联配体中的环戊二烯基发生加成反应得到含有独特三环结构的有机钌配合物.以上结果表明,配体的位阻效应和炔烃的种类都可以影响产物的类型.本文进一步研究了此钌乙腈配合物1与烷基或芳基取代的中间炔及中间二炔的反应.配合物1与3-己炔或二苯乙炔在甲苯中于80℃反应可以生成对空气和水稳定的η4-钌-环丁二烯配合物[η5:σ-Me2C(C5H4)(C2B10H10)]Ru(η4-C4Et4)(2)或[η5:σ-Me2C(C5H4)(C2B10H10)]Ru(η4-C4Ph4...     

配合物稳定性与配体酸碱强度之间的直线自由能关系 Ⅴ.N-(对位取代苯基)氨基乙酸、邻菲罗啉与铜(Ⅱ)、镍(Ⅱ)、钴(Ⅱ)、锌(Ⅱ)生成三元配合物的稳定性研究

应用pH法,在25.0±0.1℃,0.1M NaClO_4,30％(V/V)乙醇水溶液中,测定了以邻菲罗啉(phen)为第一配体(A),N-(对位取代苯基)氨基乙酸(p-RphG;R=CH_3O,CH_3,H,Cl:G=NHCH_2COOH)为第二配体(B)的Cu(Ⅱ),Ni(Ⅱ),Co(II),Zn(Ⅱ)三元配合物的生成常数1ogK_(MAB)~(MA).结果表明,三元配合物的稳定性与第二配体的酸碱强度之间存在着直线自由能关系,即logK_(MAB)~(MA)=apK_B+C.文章讨论了影响三元配合物稳定性的各种因素.三元配合物稳定性的增加可以用金属离子与phen之间形成π反馈键来解释.与二元体系比较,Ni(Ⅱ)和Zn(Ⅱ)的三元配合物稳定性增长更大.此现象可以用π反馈键的生成以及分子内配体的芳环之间的重叠来解释.     

Synthesis and structure of ansa-cyclopentadienyl pyrrolyl titanium complexes: [(η-C5H4)CH2(2-C4H3N)]Ti(NMe2)2 and [1,3-{CH2(2-C4H3N)}2(η-C5H3)]Ti(NMe2)

Reaction of ansa-cyclopentadienyl pyrrolyl ligand (C₅H₅)CH₂(2-C₄H₃NH) (2) with Ti(NMe₂)₄ affords bis(dimethylamido)titanium complex [(η⁵-C₅H₄)CH₂(2-C₄H₃N)]Ti(NMe₂)₂ (3) via amine elimination. A cyclopentadiene ligand with two pendant pyrrolyl arms, a mixture of 1,3- and 1,4-{CH₂(2-C₄H₃NH)}₂C₅H₄ (4), undergoes an analogous reaction with Ti(NMe₂)₄ to give [1,3-{CH₂(2-C₄H₃N)}₂(η⁵-C₅H₃)]Ti(NMe₂) (5). Molecular structures of 3 and 5 have been determined by single crystal X-ray diffraction studies.     

Arylkomplexe des typs trans-[Ir(Ar)(CO)(PPh3)2]

The preparation and properties as well as some reactions of a series of arylcarbonylbis(triphenylphosphine)iridium(I) complexes [Ir(Ar)(CO)(PPh₃)₂] (Ar = C₆H₅, C₆F₅, 2-C₆H₄CH₃, 3-C₆H₄CH₃, 4-C₆H₄CH₃, 2-C₆H₄OCH₃, 2,6-C₆H₃-(OCH₃)₂, 4-C₆H₄N(CH₃)₂, 3-C₆H₄Cl, 4-C₆H₄Cl, 4-C₆H₄Cl, 3-C₆H₄CF₃, 4-C₆H₄CF₃) are described, and the most important IR data as well as the ³¹P NMR parameters of these, without exception trans-planar, compounds are given.

Some of the complexes react with molecular oxygen to form well defined dioxygen adducts [Ir(Ar)(O₂)(CO)(PPh₃)₂] (Ar = C₆H₅, 3-C₆H₄CH₃, 4-C₆H₄CH₃). Complexes with ortho-substituted aryl ligands are not oxygenated. This effect is referred to as a steric shielding of the metal center by the corresponding ortho-substituents. With SO₂ the similar irreversible addition compound [Ir(4-C₆H₄CH₃)-(SO₂)(CO)(PPh₃)₂] is obtained. Sulfur dioxide insertion into the Ir---C bond cannot be observed.

The first step of the reaction between [Ir(4-C₆H₄CH₃)(CO)(PPh₃)₂] and hydrogen chloride involves an oxidative addition of HCl to give [Ir(H)(Cl)(4-C₆-H₄CH₃)(CO)(PPh₃)₂]. Ir---C bond cleavage by reductive elimination of toluene from the primary adduct does not occur except at elevated temperature.     

Theoretical Studies on Aromaticity of Spiro Metallaaromatics of (C10H10M)2-(M=Ni,Pd, Pt)

Aiming to identify the spiro metallaaromatic systems with potential application value, (C₁₀H₁₀M)^2?(M=Ni, Pd, Pt) derivatives were theoretically investigated. (C₁₀H₁₀M)^2?-Iso1, which has two 6-membered rings(6MRs) connected by the M spiro atom, is a 14π-aromatic as a whole plane. (C₁₀H₁₀M)^2?-Iso2 has one 6π-aromatic 5MR and one 10π-aromatic 7MR connected by the spiro atom. The free (C₁₀H₁₀M)^2? dianions could not exist due to their rather high frontier orbital energies, while the neutral (C₁₀H₁₀M)Li₂ compounds are extremely stable against dissociation. Since (C₁₀H₁₀M)Li₂ coumponds are not fully coordinated, they trend to form (C₁₀H₁₀M)Li₄²⁺ dications, or even[(C₁₀H₁₀M)Li₂]_n polymers. Arguably, (C₁₀H₁₀M)^2? planes are not the only examples for spiro metallaaromaticity, their derivatives are also potential material building blocks.     

Titanium imido complexes containing 1,3,5-triazacyclohexane ligands

The syntheses of the 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane-supported imido complexes [M(NR)(R′₃tach)Cl₂] (M = Ti or Zr (NMR only); R = Bu^t or 2,6-C₆H₃Prⁱ₂; R′ = Me or Bu^t) are reported, along with that of the thermally robust dibenzyl derivative [Ti(NBu^t)(Me₃tach)(CH₂Ph)₂]. The tert-butylimido ligand in [Ti(NBu^t)(Me₃tach)Cl₂] undergoes exchange with ArNH₂ (Ar = 4-C₆H₄Me or 2,6-C₆H₄Me or 2,6-C₆H₃Prⁱ₂) to form the corresponding arylimides [Ti(NAr)(Me₃tach)Cl₂]. The Me₃tach ring in [Ti(NR)(Me₃tach)Cl₂] undergoes slow exchange with Bu^t₃tach or Me₃tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) to give the ring-exchanged products [Ti(NR)(Bu^t₃tach)Cl₂] and [Ti(NR)(Me₃tacn)Cl₂], respectively. The complexes [Ti(NR)(Me₃tach)X₂] (R = Bu^t or 2,6-C₆H₃Prⁱ₂; X = Cl or CH₂Ph) exhibit room-temperature dynamic NMR behaviour via an unusual trigonal twist of the facially coordinated Me₃tach ligand, and the activation parameters for these processes have been measured and are discussed. The X-ray structures of [Ti(NR)(Bu^t₃tach)Cl₂] (R = Bu^t or 2,6-C₆H₃Prⁱ₂) and [Ti(NBu^t)(Me₃tach)(X)₂] [X= Cl or CH₂Ph) are reported. Me₃tach and Bu^t₃tach = 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane, respectively.     

双(烷基环戊二烯基)二硫氰基钛、锆、铪的合成

文献报道了双(环戊二烯基)二硫氰基钛、锆、铪^[1-3]及双(甲基环戊二烯基)二硫氰基钛^[4]的合成。我们利用双(烷基环戊二烯基)二氯化钛、锆、铪与过量硫氰酸钾反应,合成了一系列新的双(烷基环戊二烯基)二硫氰基钛、锆、铪(见表1)。     

Group 4 metallacarboranes of constrained geometries derived from B(cage)- and C(cage)-silylamido-substituted carborane ligands: a synthetic and structural investigation

The reactions of RNHSi(Me)₂Cl (1, R=t-Bu; 2, R=2,6-(Me₂CH)₂C₆H₃) with the carborane ligands, nido-1-Na(C₄H₈O)-2,3-(SiMe₃)₂-2,3-C₂B₄H₅ (3) and Li[closo-1-R′-1,2-C₂B₁₀H₁₀] (4), produced two kinds of neutral ligand precursors, nido-5-[Si(Me)₂N(H)R]-2,3-(SiMe₃)₂-2,3-C₂B₄H₅, (5, R=t-Bu) and closo-1-R′-2-[Si(Me)₂N(H)R]-1,2-C₂B₁₀H₁₀ (6, R=t-Bu, R′=Ph; 7, R=2,6-(Me₂CH)₂C₆H₃, R′=H), in 85, 92, and 95% yields, respectively. Treatment of closo-2-[Si(Me)₂NH(2,6-(Me₂CH)₂C₆H₃)]-1,2-C₂B₁₀H₁₁ (7) with three equivalents of freshly cut sodium metal in the presence of naphthalene produced the corresponding cage-opened sodium salt of the “carbons apart” carborane trianion, [nido-3-{Si(Me)₂N(2,6-(Me₂CH)₂C₆H₃)}-1,3-C₂B₁₀H₁₁]³⁻ (8) in almost quantitative yield. The reaction of the trianion, 8, with anhydrous MCl₄ (M=Ti and Zr) in 1:1 molar ratio in dry tetrahydrofuran (THF) at −78 °C, resulted in the formation of the corresponding half-sandwich neutral d⁰-metallacarborane, closo-1-M[(Cl)(THF)_n]-2-[1′-η¹σ-N(2,6-(Me₂CH)₂C₆H₃)(Me)₂Si]-2,4-η⁶-C₂B₁₀H₁₁ (M=Ti (9), n=0; M=Zr (10), n=1) in 47 and 36% yields, respectively. All compounds were characterized by elemental analysis, ¹H-, ¹¹B-, and ¹³C-NMR spectra and IR spectra. The carborane ligand, 7, was also characterized by single crystal X-ray diffraction. Compound 7 crystallizes in the monoclinic space group P2₁/c with a=8.2357(19) Å, b=28.686(7) Å, c=9.921(2) Å; β=93.482(4)°; V=2339.5(9) ų, and Z=4. The final refinements of 7 converged at R=0.0736; wR=0.1494; GOF=1.372 for observed reflections.     

Metallorganische lewissäuren : XX. Reaktionen von (π-C5H5)(CO)2LM-X (L = CO, PR3; M = Mo, W; X = BF4, PF6, AsF6, SbF6) mit Schwefel-haltigen liganden

The compounds (π-C₅H₅)(CO)₂LM-X (L = CO, PR₃; M = Mo, W; X = BF₄, PF₆, AsF₆, SbF₆) react with H₂S, p-MeC₆H₄SH, Ph₂S and Ph₂SO(L′) to give ionic complexes [(π-C₅H₅)(CO)₂LML′]⁺ X⁻. Also sulfur-bridged complexes, [(π-C₅H₅)(CO)₃W---SH---W(CO)₃(π-C₅H₅)]⁺ AsF₆⁻ and [(π-C₅H₅)(CO)₃M-μ-S₂C=NCH₂Ph-M(CO)₃(π-C₅H₅)], have been obtained. Reactions with SO₂ and CS₂ have been examined.     

Dissociation reactions of the vinyl radical in the AA″ state

In the present theoretical work we have explored mechanisms of dissociation reactions of the vinyl radical in the A²A″ state (C₂H₃ (A²A″)) and examined possible pathways for nonadiabatic dissociation of C₂H₃ (A²A″) into C₂H₂ (X¹Σ_g⁺). In the calculations we used the complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods in conjunction with the cc-pVDZ and cc-pVTZ basis sets. Mechanisms for the following three dissociation channels of C₂H₃ in the A²A″ state were explored: (1) C₂H₃ (A²A″) → C₂H₂ (trans, ³A_u) + H, (2) C₂H₃ (A²A″) → C₂H₂ (cis, ³A₂) + H, and (3) C₂H₃ (A²A″) → H₂CC (³A₂) + H. The CASSCF and CASPT2 potential energy curve calculations for the C₂H₃ (A²A″) dissociation channels (1)–(3) indicate that there is neither transition state nor intermediate for each of the channels. At the CASPT2//CASSCF/cc-pVTZ level, the dissociation energies for channels (1)–(3) are predicted to be 84.3, 91.1, and 86.9 kcal/mol, respectively. For a recently observed nonadiabatic dissociation of C₂H₃ (A²A″) into C₂H₂ (X¹Σ_g⁺) + H [J. Chem. Phys. 111 (1999) 3783], two previously suggested internal conversion (IC) pathways were examined based on our CASSCF and CASPT2 calculations. Our preliminary CASSCF and CASPT2 calculations indicate that the assumed IC pathway via the twisted C₂H₃ (A²A^′) structure might be feasible. The CASSCF/cc-pVTZ geometry optimization and frequency analysis calculations were performed for the four C_2v bridge structures in the ²B₂, ²A₂, ²B₁, and ²A₁ states along the pathways of the 1²A^′ (X²A^′), 1²A″ (A²A″), 2²A″, and 2²A^′ states of C₂H₃, respectively, and the CASPT2//CASSCF/cc-pVTZ energetic results indicate that the assumed IC pathway, via a C_2v (²A₂) structure and then ²A₂/²A₁ surface crossing, be not feasible since at their excitation wavelengths (327.4 and 366.2 nm) the C_2v (²A₂) structure could not be accessed.     

New Half-sandwich Zirconium（IV） Complexes Containing Salicylaldimine Ligands： Synthesis,Characterizations and Catalytic Properties

Two new half-sandwich zirconium（IV） complexes bearing salicylaldimine ligands of the type Cp＊Zr[2-tBu-4-R-6-（CH=NiPr）C6H2O]C12[R=H（1）, tBu（2）] were prepared by the reaction of Cp＊ZrC13 with the corresponding lithium of salicylaldimine ligands 2-tBu-4-R-6-（CH=NiPr）C6H2OLi[R=H（LiLa）, tBu（LiLb）]. Com- plexes 1 and 2 were characterized by 1H NMR, BC NMR spectroscopy and elemental analysis. When activated with AliBu3 and Ph3CB（C6F5）4, both complexes 1 and 2 exhibited reasonable catalytic activities for ethylene polymeriza- tion, producing polyethylenes with moderate molecular weight. Complexes 1 and 2 also exhibited reasonable catalyt- ic activities for ethylene copolymerization with 1-hexene, producing poly（ethylene-co-l-hexene）s with moderate molecular weight and reasonable 1-hexene content.     

Interaction of half-sandwich alkylmolybdenum(III) complexes with B(C6F5)3. The X-ray structure of [CpMo(η-C4H6)(μ-Cl)(μ-CH2)(O)MoCp][CH3B(C6F5)3]

The reactions of the half-sandwich molybdenum(III) complexes CpMo(η⁴-C₄H₄R₂)(CH₃)₂, where Cp=η⁵-C₅H₅ and R=H or CH₃, with equimolar amounts of B(C₆F₅)₃ have been investigated in toluene. EPR monitoring shows the formation of an addition product which does not readily react with Lewis bases such as ethylene, pyridine, or PMe₃. The analysis of the EPR properties and the X-ray structure of a decomposition product obtained from dichloromethane, [CpMo(η⁴-C₄H₆)(μ-Cl)(μ-CH₂)(O)MoCp][CH₃B(C₆F₅)₃], indicate that the borane attack has occurred at the methyl position.