Zirconium, hafnium, and tantalum amide silyl complexes: their preparation and conversion to metallaheterocyclic complexes via gamma-hydrogen abstraction by silyl ligands.
Zirconium, hafnium, and tantalum amide silyl complexes: their preparation and conversion to metallaheterocyclic complexes via gamma-hydrogen abstraction by silyl ligands.
复制标题
锆、铪和钽酰胺甲硅烷基配合物：它们的制备以及通过甲硅烷基配体夺取γ-氢将其转化为金属杂环配合物。
作者：
Xianghua Yu;Siwei Bi;I. Guzei;Zhenyang Lin;Z. Xue
新的过渡金属硅酰胺配合物(Me(2)N)(3)Ta[N(SIME(3))(2)](SIPH(2)Bu(T))(1)和(Me(2)N)M[N(SIME(3))(2)](2)(SIPH(2)Bu(T))(M=Zr，2a和Hf，2b)分别被硅基配体进行伽马-H抽提，得到金属杂环化合物(3)和(M=Zr，4a和Hf，4b)。由(Me(2)N)Zr[N(Sime(3))(2)](2)Cl(5a)和Li(THF)(2)SIPH(2)Bu(T)(6)生成4a的反应是由(Me(2)N)Zr[N(Sime(3))(2)](2)Cl(5a)和Li(THF)(2)SiPh(2)Bu(T)(6)生成的。用解析方法和数值方法对这些连续反应进行了动力学研究，即二级反应得到2a，然后一级伽马-H抽提得到4a。在278K，两个连续反应的速率常数k(1)和k(2)分别为2.17(0.03)x10(-)(3)M(-)(1)S(-)(1)和5.80(0.15)x10(-)(5)S(-)(1)。本工作是对A+B-->；C->；D(+E)连续反应的罕见的动力学研究。据我们所知，金属杂环形成的动力学研究尚未见报道。此外，通过硅基配体提取伽马-H来得到这样的金属杂环部分是新的。用密度泛函理论在Becke3LYP(B3LYP)水平上对硅基配体的伽马-H抽提进行了理论研究，结果表明，通过伽马-H抽提形成的金属环络合物是由熵驱动的。还报道了(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)和(M=Zr，4a，Hf，4b)的X射线晶体结构。
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.