1,1'-[四甲基二硅氧撑]双环戊二烯基IVB族金属二氯化物的合成及结构研究

1,3-二氯四甲基二硅氧烷相继与环戊二烯基钠、钠砂及MCl4反应, 制得标题化合物: O(SiMe2)2(C5H4)2MCl2(1, M=Ti; 2, M=Zr; 3, M=Hf)。考察了1的卤素置换反应: 1与(NH4)2SiF6作用生成相应的二氟化物4, 4与氢溴酸作用生成相应的二溴化物5, 经元素分析, UV, ^1H(^1^3C)NMR和MS表征了它们的结构, 并利用X射线衍射法测定了2和3的晶体和分子结构。化合物1,2和3的有关结构数据比较表明, 由于中心金属的不同而引起其键长和键角的差异与其碳桥类似物(CH2)3(C5H4)2MCl2的情况相似。     

1,1'-[四甲基二硅氧撑]双环戊二烯基IVB族金属二氯化物的合成及结构研究

1,3-二氯四甲基二硅氧烷相继与环戊二烯基钠、钠砂及MCl4反应, 制得标题化合物: O(SiMe2)2(C5H4)2MCl2(1, M=Ti; 2, M=Zr; 3, M=Hf)。考察了1的卤素置换反应: 1与(NH4)2SiF6作用生成相应的二氟化物4, 4与氢溴酸作用生成相应的二溴化物5, 经元素分析, UV, ^1H(^1^3C)NMR和MS表征了它们的结构, 并利用X射线衍射法测定了2和3的晶体和分子结构。化合物1,2和3的有关结构数据比较表明, 由于中心金属的不同而引起其键长和键角的差异与其碳桥类似物(CH2)3(C5H4)2MCl2的情况相似。     

柄型金属有机化合物(Ⅳ)——四甲基二硅桥连取代环戊二烯基钛和锆化合物的合成及催化乙烯聚合

四甲基二硅桥连取代环戊二烯基配体相继与丁基锂及MCl₄·2THF作用,生成四甲基二硅桥连取代环戊二烯基钛和锆化合物(Me₂SiSiMe₂)(C₅H₄R)(C₅H₄R')MCl₂[R=H,R'=t-Bu,M=Ti(1),Zr(2),Hf(3);R=H,R'=Me,M=Ti(4);R=R'=Me,M=Ti(5),Zr(6)].通过元素分析、MS和¹HNMR谱表征了化合物的分子结构,并通过X射线衍射分析测定了化合物1的晶体结构.研究了在甲基铝氧烷(MAO)的助催化下,化合物1-3和6对乙烯聚合的催化性能。     

大取代茂钛,锆,铪,铁化合物的合成与结构分析

通过芳基锂与6,6-二烷基富烯发生环外双键的加成反应,形成的取代环戊二烯基阴离子与FeCl_2、MCl_4(M=Ti,Zr,Hf)及(CpTiCl_2)_2络合,合成出16个含或不含手性碳取代茂金属化合物。对其~1H NMR光谱进行了研究。     

茂金属催化剂Cpt2MCl2(Cpt=tBuC5H4，M=Ti、zr、Hf)聚合丁烯-1的研究

探讨了茂金属催化剂Cpt2MCl2(CPt=tBuC5H4,M=Ti,zr,Hf)的合成以及用于聚合丁烯-1的研究,研究了几种不同的茂金属催化剂和不同聚合条件下的催化行为,并通过IR、1H NMR、EI-MS、DSC、粘度法测分子量和正庚烷抽提等测试手段对催化剂和聚合物进行了表征．结果表明,叔丁基取代的茂金属催化剂催化丁烯-1聚合具有较高的催化活性,叔丁基的引入提高了聚合物的等规度和分子量．     

茂金属催化剂Cp_2~tMCl_2(Cp~t=~tBuC_5H_4,M=Ti、Zr、Hf)聚合丁烯-1的研究

探讨了茂金属催化剂 Cpt2 MCl2 ( Cpt=t Bu C5 H4,M=Ti,Zr,Hf)的合成以及用于聚合丁烯 -1的研究 ,研究了几种不同的茂金属催化剂和不同聚合条件下的催化行为 ,并通过 IR、1 H NMR、EI-MS、DSC、粘度法测分子量和正庚烷抽提等测试手段对催化剂和聚合物进行了表征 .结果表明 ,叔丁基取代的茂金属催化剂催化丁烯 -1聚合具有较高的催化活性 ,叔丁基的引入提高了聚合物的等规度和分子量     

柄型金属有机化合物(Ⅵ)——四甲基二硅氧桥连不对称茂金属化合物的合成、结构及催化乙烯聚合

四甲基二硅氧桥连不对称环戊二烯基及茚基配体C₅H₅Me₂SiOSiMe₂Cp′H相继与丁基锂及MCl₄·2THF作用,生成四甲基二硅氧桥连不对称茂金属化合物(Me₂SiOSiMe₂)(C₅H₄)(Cp′)MCl₂[Cp′=C₅H₃Bu^t,M=Ti(1),Zr(2);Cp′=C₉H₆,M=Ti(3),Zr(4)].通过元素分析、MS和¹H NMR谱表征了化合物的分子结构,并通过X射线衍射分析测定了化合物1的晶体结构.研究了在MAO(甲基铝氧烷)的助催化下,化合物1～4对乙烯聚合的催化性能.     

1,1＇-[四甲基二硅氧撑]双环戊二烯基ⅣB族金属二氯化物的合成及结构研究

1,3-二氯四甲基二硅氧烷相继与环戊二烯基钠、钠砂及 MCl_4反应,制得标题化合物:O(SiMe_2)_2(C_5H_4)_2MCl_2(1,M=Ti;2,M=Zr;3,M=Hf).考察了1的卤素置换反应:1与(NH_4)_2SiF_6作用生成相应的二氟化物4,4与氢溴酸作用生成相应的二溴化物5.经元素分析,UV,~1H(~(13)C)NMR 和 MS 表征了它们的结构,并利用 X 射线衍射法测定了2和3的晶体和分子结构.化合物1,2和3的有关结构数据比较表明,由于中心金属的不同而引起其键长和键角的差异与其碳桥类似物(CH_2)_3(C_5H_4)_2MCl_2的情况相似.     

二(三甲硅基环戊二烯基)二氯合锆的合成和晶体结构

在 THF中 ,通过三甲硅基环戊二烯基锂与四氯化锆反应合成了标题化合物 ,经元素分析 ,IR和 1 H NMR谱表征了其结构 ,并用 X-射线衍射测定了晶体结构 ,该晶体属于三斜晶系 ,空间群为 P1 ,晶体学参数 :a=0 .6787(6) ,b=1 .2 92 4 (2 ) ,c=1 .30 34(2 ) nm,α=67.83(1 ) ,β=82 .50 (3) ,γ=75.64 (3)°,V=1 .0 2 5nm3 ,Z=2 ,Dx=1 .41 5 g· cm-3 ,μ=8.989cm-1 ,F (0 0 0 ) =448,R=0 .0 32。质谱研究表明 ,化合物在质谱过程中发生二聚 C*p2 ZrClZr C*P2Cl(C*P=C5H4Si Me3 )。     

大取代环戊二烯基铪的合成与结构分析

芳基锂与6, 6-二烷基富烯发生加成反应, 生成含或不含手性碳的大位阻取代环戊二烯基负离子。用四氯化铪配合物, 合成了19个大取代茂铪化合物。讨论了其^1H NMR。化合物[(CH3)2C(C6H4-p-CH3)-C5H4]HfCl2经X射线衍射分析。晶体为单斜晶系, 空间群为I2/a, 晶胞参数a=2.2263(7), b=0.6674(2), c=2.5379(9)nm,β=135.13(3)°, R=0.058, Rw=0.069。结构研究表明, 取代基的引入, 使得茂环发生变型, 最大扭曲角为8.45°。     

Syntheses and structures of the infinite chain compounds Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14)

The alkali metal/group 4 metal/polychalcogenides Cs(4)Ti(3)Se(13), Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) have been synthesized by means of the reactive flux method at 823 or 873 K. Cs(4)Ti(3)Se(13) crystallizes in a new structure type in space group C(2)(2)-P2(1) with eight formula units in a monoclinic cell at T = 153 K of dimensions a = 10.2524(6) A, b = 32.468(2) A, c = 14.6747(8) A, beta = 100.008(1) degrees. Cs(4)Ti(3)Se(13) is composed of four independent one-dimensional [Ti(3)Se(13)(4-)] chains separated by Cs(+) cations. These chains adopt hexagonal closest packing along the [100] direction. The [Ti(3)Se(13)(4-)] chains are built from the face- and edge-sharing of pentagonal pyramids and pentagonal bipyramids. Formal oxidation states cannot be assigned in Cs(4)Ti(3)Se(13). The compounds Rb(4)Ti(3)S(14), Cs(4)Ti(3)S(14), Rb(4)Hf(3)S(14), Rb(4)Zr(3)Se(14), Cs(4)Zr(3)Se(14), and Cs(4)Hf(3)Se(14) crystallize in the K(4)Ti(3)S(14) structure type with four formula units in space group C(2)(h)()(6)-C2/c of the monoclinic system at T = 153 K in cells of dimensions a = 21.085(1) A, b = 8.1169(5) A, c = 13.1992(8) A, beta = 112.835(1) degrees for Rb(4)Ti(3)S(14);a = 21.329(3) A, b = 8.415(1) A, c = 13.678(2) A, beta = 113.801(2) degrees for Cs(4)Ti(3)S(14); a = 21.643(2) A, b = 8.1848(8) A, c = 13.331(1) A, beta = 111.762(2) degrees for Rb(4)Hf(3)S(14); a = 22.605(7) A, b = 8.552(3) A, c = 13.880(4) A, beta = 110.919(9) degrees for Rb(4)Zr(3)Se(14); a = 22.826(5) A, b = 8.841(2) A, c = 14.278(3) A, beta = 111.456(4) degrees for Cs(4)Zr(3)Se(14); and a = 22.758(5) A, b = 8.844(2) A, c = 14.276(3) A, beta = 111.88(3) degrees for Cs(4)Hf(3)Se(14). These A(4)M(3)Q(14) compounds (A = alkali metal; M = group 4 metal; Q = chalcogen) contain hexagonally closest-packed [M(3)Q(14)(4-)] chains that run in the [101] direction and are separated by A(+) cations. Each [M(3)Q(14)(4-)] chain is built from a [M(3)Q(14)] unit that consists of two MQ(7) pentagonal bipyramids or one distorted MQ(8) bicapped octahedron bonded together by edge- or face-sharing. Each [M(3)Q(14)] unit contains six Q(2)(2-) dimers, with Q-Q distances in the normal single-bond range 2.0616(9)-2.095(2) A for S-S and 2.367(1)-2.391(2) A for Se-Se. The A(4)M(3)Q(14) compounds can be formulated as (A(+))(4)(M(4+))(3)(Q(2)(2-))(6)(Q(2-))(2).     

Synthesis, structure, and reactivity of Group 4 metallacycles incorporating a Me2C-linked cyclopentadienyl-carboranyl ligand

Group 4 metallacycles [eta5:sigma-Me2C(C5H4)(C2B10H10)]Ti[eta2-N(Me)CH2CH2N(Me)] (1a), [eta5:sigma-Me2C(C5H4)(C2B10H10)]Zr[eta2-N(Me)CH2CH2N(Me)](HNMe2) (1b) and [eta5:sigma-Me2C(C5H4)(C2B10H10)]M[eta2-N(Me)CH2CH2CH2N(Me)] (M = Ti (2a), Zr (2b), Hf (2c)) were synthesized by reaction of [eta5:sigma-Me2C(C5H4)(C2B10H10)]M(NMe2)(2) (M = Ti, Zr, Hf) with MeNH(CH2)(n)NHMe (n = 2, 3). These metal complexes reacted with unsaturated molecules such as 2,6-Me2C6H3NC, PhNCO and PhCN to give exclusively M-N bond insertion products. The M-C(cage) bond remained intact. Such a preference of M-N over M-C(cage) insertion is suggested to most likely be governed by steric factors, and the mobility of the migratory groups plays no obvious role in the reactions. This work also shows that the insertion of unsaturated molecules into the metallacycles is a useful and effective method for the construction of very large ring systems.     

Synthese und konformationsstudien von selen-analoga der metallocen-dithiolen-chelate früher übergangsmetalle

The reaction of the metallocene dichlorides Cp₂MCl₂ (Cp = η⁵-C₅H₅; M = Ti, Zr, Hf, Mo, W) and Cp₂′TiCl₂ (Cp′ = η⁵-C₅H₄CH₃) with equimolar amounts of dilithium-benzene-o-diselenolate, 1,2-(LiSe)₂C₆H₄, gives the chelate complexes Cp₂M(Se₂C₆H₄) (M = Ti (I), Zr (II), Hf (III), Mo (IV), W (V)) and Cp₂′Ti(Se₂C₆H₄) (VI). CpTiCl₃ reacts with 1,2-(LiSe)₂C₆H₄ to give CpTiCl(Se₂C₆H₄) (VII). The ring inversion activation parameters for I–VI can be determined by means of temperature-dependent ¹H NMR spectroscopy in solution. The fragmentation behaviour of I–VII in the mass spectrometer has been investigated by pursuing metastable transitions, using linked-scan techniques.     

Synthesis, characterization, and materials chemistry of Group 4 silylimides

This paper focuses on the development of potential single source precursors for M-N-Si (M = Ti, Zr or Hf) thin films. The titanium, zirconium, and hafnium silylimides (Me(2)N)(2)MNSiR(1)R(2)R(3) [R(1) = R(2) = R(3) = Ph, M = Ti(1), Zr (2), Hf (3); R(1) = R(2) = R(3) = Et, M = Ti (4), Zr (5), Hf (6); R(1) = R(2) = Me, R(3) = (t)Bu, M = Ti (7), Zr (8), Hf (9); R(1) = R(2) = R(3) = NMe(2), M = Ti (10), Zr (11), Hf (12)] have been synthesized by the reaction of M(NMe(2))(4) and R(3)R(2)R(1)SiNH(2). All compounds are notably sensitive to air and moisture. Compounds 1, 2, 4, and 7-10 have been structurally characterized, and all are dimeric, with the general formula [M(NMe(2))(2)(μ-NSiR(3))](2), in which the μ(2)-NSiR(3) groups bridges two four-coordinate metal centers. The hafnium compound 3 possesses the same basic dimeric structure but shows additional incorporation of liberated HNMe(2) bonded to one metal. Compounds 11 and 12 are also both dimeric but also incorporate additional μ(2)-NMe(2) groups, which bridge Si and either Zr or Hf metal centers in the solid state. The Zr and Hf metal centers are both five-coordinated in these species. Aerosol-assisted CVD (AA-CVD) using 4-7 and 9-12 as precursors generates amorphous films containing M, N, Si, C, and O; the films are dominated by MO(2) with smaller contributions from MN, MC and MSiON based on XPS binding energies.     

Group 4 complexes of a tert-butylphosphine-bridged biphenolate ligand

The coordination chemistry of group 4 complexes supported by the tridentate, dianionic biphenolate phosphine ligand that carries a phosphorus-bound tert-butyl group, 2,2'-tert-butylphosphino-bis(4,6-di-tert-butylphenolate) ([(t)Bu-OPO](2-)), is described. Metathetical reactions of {[(t)Bu-OPO]Li(2)(DME)}(2) with 2 or 1 equiv of TiCl(4)(THF)(2) selectively produce [(t)Bu-OPO]TiCl(2)(THF) (1a) and Ti[(t)Bu-OPO](2) (2a), respectively. Protonolysis of Ti(O(i)Pr)(4) with 2 or 1 equiv of H(2)[(t)Bu-OPO] cleanly generates 2a and [(t)Bu-OPO]Ti(O(i)Pr)(2) (3a), respectively. Complex 1a can alternatively be prepared from comproportionation of 2a with 1 equiv of TiCl(4)(THF)(2). Treatment of 1a with 2 equiv of NaO(t)Bu affords [(t)Bu-OPO]Ti(O(t)Bu)(2) (4a). In contrast, reactions of {[(t)Bu-OPO]Li(2)(DME)}(2) with ZrCl(4)(THF)(2) or HfCl(4)(THF)(2), regardless of stoichiometry of the starting materials employed, selectively give bis-ligated M[(t)Bu-OPO](2) [M = Zr (2b), Hf (2c)]. Comproportionation of 2b,c with MCl(4)(THF)(2) (M = Zr, Hf) leads to the formation of [(t)Bu-OPO]MCl(2)(THF) [M = Zr (1b), Hf (1c)], which, upon being treated with 2 equiv of NaO(t)Bu, generates [(t)Bu-OPO]M(O(t)Bu)(2)(THF) (4b,c). These synthetic results are markedly different from those obtained from analogous reactions employing a biphenolate phosphine ligand bearing a phosphorus-bound phenyl group ([Ph-OPO](2-)), highlighting a profound phosphorus substituent effect on complex conformation. The alkoxide complexes 3a and 4a-c are all active initiators for catalytic ring-opening polymerization of ε-caprolactone. To assess the potential phosphorus substituent effect on catalysis, [Ph-OPO]Ti(O(i)Pr)(2) (5a) was prepared, and its reactivity was examined. Interestingly, polymers prepared from 3a are characterized by low polydispersities with molecular weights that are linearly dependent on the monomer-to-initiator ratio, thus featuring a living system. The polydispersitiy indexes of polymers prepared from 5a, however, are relatively larger, indicative of the significance of the phosphorus-bound tert-butyl group in 3a in view of discouraging the undesirable transesterification.     

Synthesis and structures of cycloalkylidene-bridged cyclopentadienyl metallocene catalysts: effects of the bridges of ansa-metallocene complexes on the catalytic activity for ethylene polymerization

A series of cycloalkylidene-bridged cyclopentadienyl metallocene complexes, [(CH(2))(n)C(C(5)H(4))(2)MCl(2)] (M = Ti, n = 4 (4), 5 (5), 6 (6); M = Zr, n = 4 (7), 5 (8), 6 (9); M = Hf, n = 4 (10), 5 (11), 6 (12)), have been synthesized and applied to ethylene polymerization after activation with methyl aluminoxane (MAO). The cycloalkylidene-bridged titanocene catalysts exhibit much higher activities than the corresponding zirconocene and hafnocene analogues, and have the highest activities at higher temperatures. In comparison, the silacyclopentylidene-bridged metallocene complexes [(CH(2))(4)Si(C(5)H(4))(2)MCl(2)] (M = Ti (13), Zr (14)) and isopropylene-bridged metallocene complexes [Me(2)C(C(5)H(4))(2)MCl(2)] (M = Ti (15), Zr (16)) have also been synthesized and applied to ethylene polymerization. In both cases, the titanocene complexes show much higher activities than the corresponding zirconocene analogues, especially at a lower temperature. The molecular structures of complexes 4-9 have been determined by X-ray diffraction. The structure-activity relationships, especially the effects of the bridges of ansa-metallocene complexes, are discussed.     

Synthesis and catalysis of di- and tetranuclear metal sandwich-type silicotungstates [(gamma-SiW10O36)2M2(mu-OH)2]10- and [(gamma-SiW10O36)2M4(mu4-O)(mu-OH)6]8- (M = Zr or Hf)

The di- and tetranuclear metal sandwich-type silicotungstates of Cs10[(gamma-SiW10O36)2{Zr(H2O)}2(mu-OH)2] x 18 H2O (Zr2, monoclinic, C2/c (No. 15), a = 25.3315(8) A, b = 22.6699(7) A, c = 18.5533(6) A, beta = 123.9000(12) degrees, V = 8843.3(5) A(3), Z = 4), Cs10[(gamma-SiW10O36)2{Hf(H2O)}2(mu-OH)2] x 17 H2O (Hf2, monoclinic, space group C2/c (No. 15), a = 25.3847(16) A, b = 22.6121(14) A, c = 18.8703(11) A, beta = 124.046(3) degrees, V = 8974.9(9) A(3), Z = 4), Cs8[(gamma-SiW10O36)2{Zr(H2O)}4(mu4-O)(mu-OH)6] x 26 H2O (Zr4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.67370(10) A, c = 61.6213(8) A, V = 9897.78(17) A(3), Z = 4), and Cs8[(gamma-SiW10O36)2{Hf(H2O)}4(mu4-O)(mu-OH)6] x 23 H2O (Hf4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.68130(10) A, c = 61.5483(9) A, V = 9897.91(18) A(3), Z = 4) were obtained as single crystals suitable for X-ray crystallographic analyses by the reaction of a dilacunary gamma-Keggin silicotungstate K8[gamma-SiW10O36] with ZrOCl2 x 8 H2O or HfOCl2 x 8 H2O. These dimeric polyoxometalates consisted of two [gamma-SiW10O36](8-) units sandwiching metal-oxygen clusters such as [M2(mu-OH)2](6+) and [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). The dinuclear zirconium and hafnium complexes Zr2 and Hf2 were isostructural. The equatorially placed two metal atoms in Zr2 and Hf2 were linked by two mu-OH ligands and each metal was bound to four oxygen atoms of two [gamma-SiW10O36](8-) units. The tertanuclear zirconium and hafnium complexes Zr4 and Hf4 were isostructural and consisted of the adamantanoid cages with a tetracoordinated oxygen atom in the middle, [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). Each metal atom in Zr4 and Hf4 was linked by three mu-OH ligands and bound to two oxygen atoms of the [gamma-SiW10O36](8-) unit. The tetra-nuclear zirconium and hafnium complexes showed catalytic activity for the intramolecular cyclization of (+)-citronellal to isopulegols without formation of byproducts resulting from etherification and dehydration. A lacunary silicotungstate [gamma-SiW10O34(H2O)2](4-) was inactive, and the isomer ratio of isopulegols in the presence of MOCl2 x 8 H2O (M = Zr or Hf) were much different from that in the presence of tetranuclear complexes, suggesting that the [M4(mu4-O)(mu-OH)6](8+) core incorporated into the POM frameworks acts as an active site for the present cyclization. On the other hand, the reaction hardly proceeded in the presence of dinuclear zirconium and hafnium complexes under the same conditions. The much less activity is possibly explained by the steric repulsion from the POM frameworks in the dinuclear complexes.     

Zr(7)Sb(4): a new binary zirconium-rich antimonide

Zr(7)Sb(4) has been prepared by arc-melting of the elemental components and annealing at 1000-1150 degrees C. Its crystal structure was determined by X-ray diffraction (Pearson symbol mP44, monoclinic, space group P2(1)/c, Z = 4, a = 8.4905(6) A, b = 11.1557(8) A, c = 11.1217(8) A, beta = 111.443(2) degrees at 295 K). Zr(7)Sb(4) is isotypic to Hf(6)TiSb(4), a compound stabilized by differential fractional site occupancy. It is the first binary group-4 antimonide with this metal-to-antimony ratio, but it differs from the corresponding phosphides and arsenides M(7)Pn(4) (M = Ti, Zr, Hf; Pn = P, As), which adopt the Nb(7)P(4)-type structure. Zr(7)Sb(4) is built up from layers excised from the tetragonal W(5)Si(3)-type structure; these layers are displaced relative to each other to maximize interlayer Zr-Zr and Zr-Sb bonding, as confirmed by band structure calculations.     

Zirconium, hafnium, and tantalum amide silyl complexes: their preparation and conversion to metallaheterocyclic complexes via gamma-hydrogen abstraction by silyl ligands

New transition metal silyl amide complexes (Me(2)N)(3)Ta[N(SiMe(3))(2)](SiPh(2)Bu(t)) (1) and (Me(2)N)M[N(SiMe(3))(2)](2)(SiPh(2)Bu(t)) (M = Zr, 2a, and Hf, 2b) were found to undergo gamma-H abstraction by the silyl ligands to give metallaheterocyclic complexes (3) and (M = Zr, 4a, and Hf, 4b), respectively. The conversion of 1 to 3 follows first-order kinetics with DeltaH() = 23.6(1.6) kcal/mol and DeltaS() = 3(5) eu between 288 and 313 K. The formation of 4a from (Me(2)N)Zr[N(SiMe(3))(2)](2)Cl (5a) and Li(THF)(2)SiPh(2)Bu(t) (6) involves the formation of the intermediate 2a, followed by gamma-H abstraction. Kinetic studies of these consecutive reactions, a second-order reaction to give 2a and then a first-order gamma-H abstraction to give 4a, were conducted by an analytical method and a numerical method. At 278 K, the rate constants k(1) and k(2) for the two consecutive reactions are 2.17(0.03) x 10(-)(3) M(-)(1) s(-)(1) and 5.80(0.15) x 10(-)(5) s(-)(1) by the analytical method. The current work is a rare kinetic study of the A + B --> C --> D (+ E) consecutive reactions. Kinetic studies of the formation of a metallaheterocyclic moiety have, to our knowledge, not been reported. In addition, gamma-H abstraction by a silyl ligand to give such a metallaheterocyclic moiety is new. Theoretical investigations of the gamma-H abstraction by silyl ligands have been conducted by density functional theory calculations at the Becke3LYP (B3LYP) level, and they revealed that the formation of the metallacyclic complexes through gamma-H abstraction is entropically driven. X-ray crystal structures of (Me(2)N)(3)Ta[N(SiMe(3))(2)](SiPh(2)Bu(t)) (1), (Me(2)N)Zr[N(SiMe(3))(2)](2)Cl (5a), and (M = Zr, 4a, and Hf, 4b) are also reported.     

Catalytic dehydrogenation of dimethylamine borane by group 4 metallocene alkyne complexes and homoleptic amido compounds

Dehydrogenation of Me(2)NH·BH(3) (1) by group 4 metallocene alkyne complexes of the type Cp(2)M(L)(η(2)-Me(3)SiC(2)SiMe(3)) [Cp = η(5)-cyclopentadienyl; M = Ti, no L (2Ti); M = Zr, L = pyridine (2Zr)] and group 4 metal amido complexes of the type M(NMe(2))(4) [M = Ti (8Ti), Zr (8Zr)] is presented.