多元掺杂尖晶石型Li1.02MxMn2-xQyO4-y正极材料的电化学特性

The effect of doping on the electrochemical performance was studied for spinel type Li_1.02M_xMn_2-xQ_yO_4-y used as cathode material in lithium-ion battery. TG/DTA curves of the precursor(the raw materials) doped with different elements were studied. The spinel materials Li_1.02Mn₂O₄, Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98, Li_1.02Co_0.02Cr_0.01 La_0.01Mn_1.96Cl_0.02O_3.98, Li_1.02Co_0.02La_1.02Mn_1.97Cl_0.02O_3.98, Li_1.02Co_0.02Cr_0.01Mn_1.97O₄, were prepared by solid-state reaction method after the pretreatment of conversion under low temperature and uniform mixing. X-ray diffraction patterns showed that all the samples had perfect spinel structure. SEM indicated that the particles of the samples had uniform size and were distributed evenly. The results of the charge/discharge curves showed that Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98 had better performance than other materials according to the inhibition of decline of reversible capacity of spinel Li_1.02M_xMn_2-xQ_yO_4-y. Therefore, cycle performance had been improved so obviously that 93.9% of the initial capacity were preserved after 100 cycles. Furthermore, electrochemical impedance tests were carried out with the spinel Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98 as working electrode, Lithium as counter electrode and reference electrode. Results showed that this material possessed good charge/discharge reversible capability and had the lowest impedance in 3.95～4.25 V range (on the stage of charge / discharge).     

流变相法合成LiNi0.85Co0.15O2的结构与电化学性能

以一种新型的软化学方法——流变相法, 成功地合成了锂离子电池正极材料LiNi_0.85Co_0.15O₂. 将在600～850 ℃氧气氛下处理6 h后得到的LiNi_1－yCo_yO₂ (y＝0.10, 0.15, 0.20, 0.25), 进行X射线粉末衍射(XRD)与电化学测试. 测试结果表明, 流变相前体经过800 ℃烧结后合成的LiNi_0.85Co_0.15O₂晶胞参数a＝0.2866 nm, c＝1.4193 nm及晶胞体积V＝0.1010 nm³, 以0.1 C倍率在3.0～4.3 V (vs. Li^＋/Li)放电时, 首次放电容量可以达到198.2 mAh/g, 20次循环后, 其放电容量仍在174 mAh/g以上.     

锂离子蓄电池正极材料LiMn2-x-y-zTlxAlyMzO4(M=Co、Cr、Ni)的合成及电化学性能研究

采用同时掺杂Tl、Al和M(M=Co、Cr和Ni)三种金属原子和改进固相反应的方法合成了复合尖晶石正极材料 LiMn_2-x-y-zTl_xAl_yM_zO₄，并采用XRD、SEM、TEM、循环伏安和电化学测试考察了它的物理性质和电化学性能。结果表明，所合成的正极材料具有与母体LiMn₂O₄尖晶石同样完整的尖晶石结构，规则的形貌和均匀的粒径分布。当M为Co和Cr时，目标材料的平均粒径约800nm，且具有良好的电化学性能，其首次充电容量分别为123.70mAh·g^-1和121.30mAh·g^-1，首次放电容量分别为117.30mAh·g^-1和115.70mAh·g^-1。当M为Ni时，材料的电化学性能相对较差。循环伏安和充放电曲线表明该正极材料的充放电分别为两步脱锂和插锂机理。当Li掺杂量较小时，目标材料在充放电过程中均各有两个平台。随着Li掺杂量的增加，充放电平台有由两个逐渐转变为一个的趋势。当M为Co或Cr时，该正极材料不仅拥有较高的比容量和常温循环稳定性能，而且还具有较优良的高温循环稳定性能，这可能主要归因于三种金属的协同作用使目标材料的结构更加稳定，这也使该材料有可能成为电动车电池的较佳正极材料。     

锂离子电池正极材料Li1.2Mn0.54-xNi0.13Co0.13ZrxO2的制备及电化学性能

为了改善富锂锰基正极材料Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ 的循环性能,采用燃烧法合成了正极材料Li_1.2Mn_0.54-xNi_0.13Co_0.13Zr_xO₂（x=0.00,0.01,0.02,0.03,0.06）. 通过X射线衍射（XRD）和扫描电镜（SEM）对其结构与形貌进行了表征,利用恒电流充放电测试,循环伏安（CV）及电化学交流阻抗谱（EIS）技术对其电化学性能进行测试. 结果表明,Li_1.2Mn_0.54-xNi_0.13Co_0.13Zr_xO₂（x=0.00,0.01,0.02,0.03,0.06）正极材料均具有α-NaFeO₂型层状结构;在室温,2.0-4.8 V电压范围,以0.1C和1.0C（充放电电流以1.0C=180 mA·g^-1计算）倍率充放电进行测试,样品Li_1.2Mn_0.52Ni_0.13Co_0.13Zr_0.02O₂的首次放电比容量分别为280.3 和206.4 mAh·g^-1. 其中,在1.0C倍率下,100次循环后容量保持率由原来的73.2%提高到88.9%;以5.0C倍率充放电进行测试,经50次循环后,掺杂正极材料的放电比容量为76.5 mAh·g^-1,而未掺杂材料仅有15.0 mAh·g^-1. 在50、25 和-10 ℃,2.0C倍率条件下,掺杂正极材料的电化学性能均得到有效改善,其中,在- 10℃ 经过50 次循环后正极材料Li_1.2Mn_0.52Ni_0.13Co_0.13Zr_0.02O₂比未掺杂的正极材料相比,其放电比容量提高了61.1%.     

Li[Ni1/3Mn1/3Co1/3]O2掺杂Mo研究

采用高温固相合成法制备了Li[Ni_(1－x)/3Mn_(1－x)/3Co_(1－x)/3Mo_x]O₂ (x＝0, 0.005, 0.01, 0.02). 对它们进行了XRD, SEM, 循环伏安及充放电容量测试, 结果发现, 掺杂x＝0.01 Mo的样品具有较高的嵌锂容量和良好的循环稳定性, 在20 mA/g放电电流密度和2.3～4.6 V的电压范围内具有211.6 mAh/g的首次放电比容量, 循环50周后放电比容量仍能达到185.9 mAh/g, 容量损失为12.1%.     

锂离子二次电池正极材料LiAlyCo0.2Ni0.8-yO2的合成及其电化学性能研究

用固相反应法合成了锂离子二次电池正极材料LiAl_yCo_0.2Ni_0.8-yO₂(y=0,0.001,0.005,0.01,0.03),采用XRD、SEM、ICP-AES、差分计时电位法和充放电循环等对合成的材料的物理化学性质以及电化学性能进行了测试分析。结果表明所合成的产物均为α-NaFeO₂型的层状结构,产物无杂质相,产物的表面形貌规则,颗粒大小均匀。实验结果证明经过Al掺杂后的材料的放电电压平台有所提高,容量也有所上升。并且随着Al含量的增加,材料在电化学充放电过程的结构稳定性在上升,因此电化学稳定性得到了提高。实验结果还表明低含量Al元素的掺杂既提高了LiNi_0.8Co_0.2O₂的放电容量,又提高了其循环可逆性,使材料的容量保持率显著提高。     

层状Li(Ni1/3Co1/3Mn1/3)O2正极材料的合成与电化学性能研究

采用共沉淀-喷雾造粒法制备前驱体, 于750 ℃在空气中煅烧20 h合成出层状Li(Ni_1/3Co_1/3Mn_1/3)O₂正极材料, 并用XRD, SEM, 粒度分析和电性能测试考察了所得材料结构、形貌及电化学性能. 本层状Li(Ni_1/3Co_1/3Mn_1/3)O₂正极材料具有α-NaFeO₂结构, 六方晶系, R3m空间群, 其晶胞参数为a＝0.2865 nm, c＝1.4238 nm. 当材料分别在2.8～4.2, 2.8～4.5 V间进行充放电时, 其首次放电容量分别为173.5和185.4 mAh•g^－1, 首次充放电效率分别为90%和83.8%, 40次循环后容量保持率分别为96%和84%.     

离子交换法制备层状LixNi0.3Mn0.7O2正极材料及其离子交换规律的研究

通过共沉淀法高温固相反应在空气气氛中合成出具有P2型结构特征的碱青铜前驱体Na_0.66Ni_0.3Mn_0.7O₂，研究了在4种不同离子交换条件下进行离子交换反应得到目标正极材料Li_xNi_0.3Mn_0.7O₂的离子交换规律，并用XRD、SEM、粒度分析和电性能测试考察了目标正极材料及其前驱体的结构、形貌和电化学性能。结果表明，以熔融LiNO₃为介质于300 ℃离子交换4h反应进行得最为完全，离子交换率达98 %，且目标正极材料具有较完善的O2型层状结构，在2.6～2.9 V存在唯一的充放电平台，循环过程中未发现向尖晶石相转变；而离子交换时间过长，目标正极材料将出现尖晶石相而影响其放电容量和循环稳定性。     

LiMn2O4表面包覆Li4Ti5O12的制备及倍率特性

采用固相法合成了尖晶石型LiMn₂O₄，并通过溶胶-凝胶法制备了不同物质的量的百分比含量Li₄Ti₅O₁₂包覆的正极材料。X-射线衍射和扫描电镜结果表明，Li₄Ti₅O₁₂微粒包覆在LiMn₂O₄的表面没有产生晶体结构的变化。实验电池在室温下，以1C，2C和5C倍率作充放电循环测试；结果表明，与未包覆的LiMn₂O₄相比，表面包覆Li₄Ti₅O₁₂微粒的正极材料在高倍率下具有更好的循环稳定性。     

溶胶-凝胶法合成Li1-xNaxMn2O4及其作为水系锂离子电池正极材料的电化学性能

用溶胶凝胶法合成了Na⁺离子掺杂的Li_1-xNa_xMn₂O₄(x=0,0.01,0.03,0.05)。X射线衍射图表明Na⁺取代Li⁺进入Li_1-xNa_x Mn₂O₄晶格中,扫描电镜图看出产物是粒径为100~300 nm的颗粒。恒流充放电测试结果表明,Li_0.97Na_0.03Mn₂O₄在2C倍率下循环100圈后放电容量保持率比未掺杂的LiMn₂O₄从51.2%提升到84.1%。循环伏安测试表明Na⁺离子掺杂降低了材料极化且增大了锂离子扩散系数。10C倍率下Li_0.97Na_0.03Mn₂O₄仍有79.0 mAh·g^-1的放电容量,高于未掺杂样品的52.1 mAh·g^-1。Na⁺离子掺杂可以稳定材料结构并提高锂离子扩散系数,从而提高LiMn₂O₄的电化学性能,是一种可行的改性方法。     

Synthesis and electrochemical properties of Li1-xVxCryFe1-yPO4/C as a cathode material

Composites Li1-xVxCryFe1-yPO4/C（x=0.01, 0.02; y = 0.01, 0.02） were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.     

Structural and spectral studies of N-2-(pyridyl)-, N-2-(3-, 4-, 5-, and 6-picolyl)- and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenylthioureas

Structures of the following compounds have been obtained: N-(2-pyridyl)-N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2₁/c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) ų and Z=4; N-2-(3-picolyl)-N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) ų and Z=8; N-2-(4-picolyl)-N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2₁/a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) ų and Z=4; N-2-(5-picolyl)-N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) ų and Z=8; N-2-(6-picolyl)-N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2₁/c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) ų and Z=4 and N-2-(4,6-lutidyl)-N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2₁/c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) ų and Z=4. Comparisons with other N-2-pyridyl-N′-arylthioureas having substituents in the 2-position of the aryl ring are included.     

三元掺杂改性锂离子电池正极材料Li3V2(PO4)3

以柠檬酸为螯合剂和还原剂, NH₄VO₃为钒源,通过溶胶-凝胶法制备了锂离子电池正极材料Li₃V₂(PO₄)₃及其三元掺杂体系Li_2.85Na_0.15V_1.9Al_0.1(PO₄)_2.9F_0.1.分别采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、能量损失谱(EELS)、拉曼(Raman)光谱、扫描电子显微镜(SEM)、X射线能谱(EDS)、恒流充放电、循环伏安(CV)和交流阻抗谱(EIS)等技术对材料的微观结构、颗粒形貌和电化学性能进行分析.结果表明:在残余碳包覆的基础上, Na、Al、F三元掺杂有利于稳定Li₃V₂(PO₄)₃的晶体结构,进一步减少颗粒团聚和提升材料导电特性,促进第三个锂离子的脱出和嵌入,从而显著改善Li₃V₂(PO₄)₃的实用电化学性能.未经掺杂的Li₃V₂(PO₄)₃原粉在1/9C、1C和6C倍率下的可逆比容量分别为141、119和98 mAh·g^-1,而三元掺杂改性材料在1/9C、1C、8C和14C倍率下的比容量分别为172、139、119和115 mAh·g^-1.在1C倍率下循环300圈后,掺杂体系的比容量依然高达118 mAh·g^-1,比原粉高出32.6%.值得注意的是,这种三元掺杂还使Li₃V₂(PO₄)₃的多平台放电曲线近似转变为一条斜线,显示出可能不同的储锂机制.     

The organic ligands as template: the synthesis, structures and properties of a series of the layered structure rare-earth coordination polymers

A series of new 2D-layered structural rare-earth coordination polymers with the general formal [Ln(C₈H₄O₅)(H₂O)₅]·(H₂O)·(C₈H₄O₅)_1/2 (Ln=Eu for (1); Gd for (2); Tb for (3); Dy for (4); and Er for (5)) have been yielded by hydrothermal synthesis. The coordination polymers crystallize in monoclinic space group C/2c with a=19.838(16), b=10.529(8), c=17.752(14) Å, β=107.503(14)° for (1), with a=19.823(7), b=10.552(4), c=17.762(6) Å, β=107.443(6)° for (2), with a=19.770(4), b=10.519(2), c=17.698(4) Å, β=107.52(3)° for (3), with a=19.632(2), b=10.492(2), c=17.617(3) Å, β=107.470(12)° for (4), with a=19.648(7), b=10.480(3), c=17.598(6) Å, β=107.502(6)° for (5), respectively. And the metal ions (Ln³⁺) are located in nine-member coordination environment. The carboxyl groups from 5-hydroxyisophthalate chelate the metal ions to form 1D helical cation chains. It is interesting that these helical cation chains are arranged to form 2D anion–cation layers by the uncoordinated ligands' anions as template. And the luminescence properties of the rare-earth ions are studied in the paper.     

一个新颖的三核镍配合物[Ni3(C13H9N2O)5(CH3OH)(CH3CH2OH)]Cl的合成、晶体结构及性质研究

在甲醇-乙醇混合溶剂中, 含有N, O给体的二齿配体2-(2-羟苯基)苯并咪唑与NiCl2•6H2O在常温下反应合成得到标题化合物, 采用元素分析、红外光谱、紫外光谱、热分析以及X射线单晶衍射法对其进行了组成和结构表征. 结果表明该化合物为三斜晶系, 空间群P-1, 晶胞参数: a＝1.2046(2) nm, b＝1.4891(3) nm, c＝2.1342(4) nm, α＝96.787(3)°, β＝104.862(3)°, γ＝99.993(3)°, V＝3.5904(12) nm3, Z＝2, Dc＝1.349 g/cm3, F(000)＝1516, GOF＝1.008, R1＝0.0583, wR2＝0.1455 [I＞2σ(I)]. 在标题化合物的晶体结构中, 晶体学不对称的三个配位中心Ni(II)原子配位环境各不相同, 五个配体提供的五个氧配位基中有四个起着桥联的作用, 形成了一个新颖的V型金属簇状化合物. 变温磁化率研究表明标题化合物在整体上表现为弱的反铁磁性耦合作用.     

Syntheses and crystal structures of 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC), 1,2:5,6:9,10:13,14-tetrabenzo-3,7,11,15-tetradehydro[16]annulene (QBC) and a tetracobalt complex of QBC. The first example of a transition metal complex of QBC

1,2:5,6:9,10:13,14-Tetrabenzo-3,7,11,15-tetradehydro[16]annulene, or tetrabenzocyclyne (QBC) and 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC) have been structurally characterized by X-ray. crystallography. QBC crystallizes in two different space groups; P2₁/c with a = 10.652(3) Å, b = 10.624(2) Å, c = 19.549(4) Å, β = 93.83(2)°, V = 2207.4(8) ų, and Z = 4 and P4₁2₁2 with a = 9.330(1) Å, c = 25.497(8) Å, V = 2219.6(12) Å, and Z = 4. HBC crystallizes in monoclinic P2₁/n with a = 14.763(3) Å, b = 10.296(2) Å, c = 22.057(4) Å, β = 108.61(3), V = 3177.4(11) ų, T = 133 K, and Z = 4. Reaction of QBC with dicobaltoctacarbonyl has produced a tetracobalt complex which has been characterized by X-ray crystallography. This complex crystallizes in monoclinic P2₁/c with a = 14.699(3) Å, b = 17.188(3) Å, c = 17.254(3) Å, β = 112.63(3)°, V = 4023.5(13) ų, and Z = 4. Only two of the four C---C triple bonds of QBC bind to dicobalthexacarbonyl moieties even when excess dicobaltoctacarbonyl is used.     

Na掺杂Li2-xNaxMnSiO4/C正极材料的微波辅助合成与电化学性能

采用溶胶-凝胶法并辅以微波热处理合成了Na掺杂改性的Li_2-xNa_xMnSiO₄/C(x=0, 0.05, 0.09, 0.13)复合正极材料. 利用X射线衍射(XRD)、 扫描电子显微镜(SEM)、 恒电流充放电测试、 循环伏安(CV)和交流阻抗(EIS)测试等对材料进行了表征. 结果表明, 经微波辐射后得到的电极材料具有Pmn2₁型空间结构, 其碳层分布均匀, 粒径细小均匀, 约为15~30 nm. 在微波辅助原位碳包覆和Na掺杂共同作用下, 复合材料的电荷转移电阻明显降低, Li⁺扩散速率增大, 展现出优良的电化学性能. 在0.1C倍率下Li_1.91Na_0.09MnSiO₄/C样品首次放电比容量为211 mA∙h/g, 50次循环后仍保持80 mA∙h/g的可逆容量; 0.5C和2.0C倍率下的放电比容量分别为106和53 mA∙h/g, 大电流下的可逆容量明显提高.     

A survey of the lone pair effect on the ring geometry of 1,2,4-triazoles and analogous 1,2,3-triazoles and imidazoles : The structures of 1-methyl-5-amino-3-methylthio-1,2,4-triazole, 1-phenyl-5-amino-3-methylthio-1,2,4-triazole and 1-(4-methylbenzyl)-3-amino-5-methylthio-1,2,4-triazole

The structures of the title compounds have been established by X-ray crystallography from diffractometer data. Crystals of the first (I), C₄H₈N₄S, are monoclinic, space group P2₁/c, with a = 8.166(2), b = 10.481(1), c = 8.585(1) Å, β = 109.33(2)°, Z = 4, D_c = 1.381 g cm⁻³. Crystals of the second (II), C₉H₁₀N₄S, are monoclinic, space group P2₁/c, with a = 11.850(4), b = 7.898(1), c = 23.981 (6) Å, β = 117.23(2)°, Z = 8, D_c = 1.373 g cm⁻³. Crystals of the third (III), C₁₁H₁₄N₄S₁ are also monoclinic, space group P2₁/c with a = 12.829(3), b = 8.348(1), c = 11.088(4) Å, β = 94.40(4)°, Z = 4, D_c = 1.314 g cm⁻³. The structures, determined by direct methods (I, III) and Patterson synthesis (II) were refined to R = 0.039 for 1070 reflections of I, R = 0.040 for 2792 reflections of II and R = 0.041 for 1900 reflections of III. The characteristic features of the planar five-membered rings are studied in comparison with the analogous 1,2,3-triazoles and imidazoles. It is shown that these planar rings exhibit only two patterns of the endocyclic bond angles induced dominantly by the number and relative position of the N-lone pairs. A similar effect of the double bonds (attached to C atoms) is also discussed.     

Cation–anion interactions in triphenyl telluronium salts. The crystal structures of (Ph3Te)2[MCl6] (M=Pt, Ir), (Ph3Te)[AuCl4], and (Ph3Te)(NO3)·HNO3

Triphenyltelluronium hexachloroplatinate (1), hexachloroiridate (2), tetrachloroaurate (3), and tetrachloroplatinate (4) were prepared from Ph₃TeCl and potassium salts of the corresponding anions. Upon recrystallization of 4 from concentrated nitric acid, K₂[PtCl₆] and (Ph₃Te)(NO₃)·HNO₃ (5) were obtained. The crystal structures of 1–3 and 5 are reported. Compounds 1 and 2 are isostructural. They are triclinic, P , Z=2 (the asymmetric unit contains two formula units). Compound 1: a=10.7535(2), b=17.2060(1), c=21.4700(3) Å, =78.9731(7), β=77.8650(4), γ=78.8369(4)°. Compound 2: a=10.7484(2), b=17.1955(2), c=21.4744(2) Å, =78.834(1), β=77.649(1), γ=78.781(1)°. Compound 3 is monoclinic, P2₁/c, Z=4, a=8.432(2), b=14.037(3), c=17.306(3) Å, β=93.70(3)°. Compound 5 is monoclinic. P2₁/n, Z=4, a=9.572(2), b=14.050(3), c=13.556(3) Å, β=90.76(3)°. The primary bonding in the Ph₃Te⁺ cation in each salt is a trigonal AX₃E pyramid with Te---C bond lengths in the range 2.095(8)–2.14(2) Å and the bond angles 94.1(6)–100.9(5)°. The weak TeCl (1–3) and TeO (5) secondary interactions expand the coordination sphere. In 1 and 2 the cation shows a trigonal bipyramidal AX₃YE coordination with one primary Te---C bond and the shortest secondary TeCl contact in axial positions and the two other Te---C bonds and the lone-pair in equatorial positions. The cation in 3 shows a distorted octahedral AX₃Y₃E environment and that in 5 is a more complex AX₃Y₃Y′₂ arrangement. In both latter salts the structure is a complicated three-dimensional network of cations and anions.     

Synthesis, characterization, and X-ray crystal structures of W(VI) alkyl complexes with chelating diamide and imido co-ligands

The complex W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄] 3 was synthesized from PhN = WCl₄ · OEt₂ and N,N′-(Li₂[o-(NSiMe₃)₂C₆H₄] and reacts with Lewis bases to form the adducts W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄](L) (L = PMe₃, THF, 3-picoline, ^tBuNC, MeCN) 4a–e. Crystals of 4a are triclinic, space group P1¯, with a = 9.562(1), b = 10.277(1), c = 14.920(2) Å, = 82.15(1), β = 80.18(1), γ = 80.41(1)°, and Z = 2. The structure was solved by the heavy atom method and refined to R = 0.0408 for 4224 observed (I > 2σ(I)) reflections. The dialkyl complexes W(NPh)R₂[o-(NSiMe₃)₂C₆H₄] (R = Me, Et, CH₂Ph, CH₂CMe₃, CH₂CMe₂Ph) 5–9 are formed through subsequent reactions of 3 with the corresponding Grignard reagent. Crystals of complex 5 are monoclinic, space group P2(1)/n, with a = 10.3545(2), b = 17.9669(1), c = 13.3168(1) Å, β = 103.826(1)°, and Z = 4. The structure of complex 5 was solved by direct methods in SHELXTL5 and refined to R = 0.0247 for 4572 observed reflections. Compound 5 has a square pyramidal geometry in which the imido ligand occupies the apical position and reacts with PMe₃ to form the adduct W(NPh)Me₂[o-(NSiMe₃)₂C₆H₄](PMe₃) 5a. Crystals of complex 5a are monoclinic, space group C2/m, with a = 13.5336(1), b = 14.4291(1), c = 15.3785(1) Å, β = 110.365(1)°, and Z = 4. The structure of compound 5a was solved by direct methods in shelxtl5 and refined to R = 0.0272 for 3057 observed reflections. Crystals of the bis-neopentyl complex 8 are monoclinic, space group P2(1)/n, with a = 10.6992(4), b = 18.3144(7), c = 16.0726(6) Å, β = 92.042(1)°, and Z = 4. The structure of 8 was solved by direct methods in shelxtl5 and refined to R = 0.0261 for 5881 observed reflections. Complex 8 has a trigonal bipyramidal geometry with both neopentyl groups and one amido nitrogen in the equatorial plane.