Lee Seul, Park Seung Soo, Kim Jin Gu, Kim Chung Sol, Lee Bun Yeoul
Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea.
Molecules. 2017 Feb 9;22(2):258. doi: 10.3390/molecules22020258.
The Me₂Si-bridged -Cp/amido half-metallocene, [Me₂Si(η⁵-Me₄C₅)(NBu)]TiCl₂, termed a "constrained-geometry catalyst (CGC)", is a representative homogeneous Ziegler catalyst. CGC derivatives with the [1,2]azasilinane framework, in which the amide alkyl substituent is joined by the Si-bridge, were prepared, and the catalytic performances of these species was studied. Me₄C₅HSi(Me)(CH₂CH=CH₂)-NH(C(R)(R')CH=CH₂) (R, R' = H or methyl; Me₄C₅H = tetramethylcyclopentadienyl) was susceptible to ring closure metathesis (RCM) when treated with Schrock's Mo-catalyst to afford -Si(Me₄C₅H)(Me)CH₂CH=CHC(R)(R')NH- containing a six-membered ring framework. Using the precursors and the products of RCM, various CGC derivatives, i.e., [-Si(η⁵-Me₄C₅)(Me)CH₂CH=CHC(R)(H)N-]TiMe₂ (, R = H; , R = Me), [-Si(η⁵-Me₄C₅)(Me)CH₂CH₂CH₂CH₂N]TiMe₂ (), [(η⁵-Me₄C₅)Si(Me)(CH₂CH=CH₂)NCH₂CH=CH₂]TiMe₂ (), [(η⁵-Me₄C₅)Si (Me)(CH=CH₂)NCH₂CH=CH₂]TiMe₂ (), and [(η⁵-Me₄C₅)Si(Me)(CH₂CH₃)NCH₂CH₂CH₃]TiMe₂ (), were prepared. The catalytic activity of the newly prepared complexes was lower than that of CGC when activated with [Ph₃C][B(C₆F₅)₄]/iBu₃Al. However, the catalytic activity of these species was improved by using tetrabutylaluminoxane ([iBu₂Al]₂O) instead of iBu₃Al and the activity of [Ph₃C][B(C₆F₅)₄]/[iBu₂Al]₂O was comparable to that of CGC/[Ph₃C][B(C₆F₅)₄]/iBu₃Al (4.7 and 5.0 × 10⁶ g/mol-Ti, respectively). Advantageously, the newly prepared complexes produced higher molecular weight poly(ethylene--1-octene)s than CGC.
被称为“受限几何催化剂（CGC）”的二甲基硅桥连的 - 环戊二烯基/酰胺半茂金属化合物[Me₂Si(η⁵-Me₄C₅)(NBu)]TiCl₂是一种典型的均相齐格勒催化剂。制备了具有[1,2]氮杂硅环戊烷骨架的CGC衍生物，其中酰胺烷基取代基通过硅桥相连，并研究了这些物质的催化性能。当用施罗克钼催化剂处理时，Me₄C₅HSi(Me)(CH₂CH=CH₂)-NH(C(R)(R')CH=CH₂)（R、R' = H或甲基；Me₄C₅H = 四甲基环戊二烯基）易于发生闭环复分解反应（RCM），得到含有六元环骨架的 -Si(Me₄C₅H)(Me)CH₂CH=CHC(R)(R')NH-。使用RCM的前体和产物，制备了各种CGC衍生物，即[-Si(η⁵-Me₄C₅)(Me)CH₂CH=CHC(R)(H)N-]TiMe₂（，R = H；，R = Me）、[-Si(η⁵-Me₄C₅)(Me)CH₂CH₂CH₂CH₂N]TiMe₂（）、[(η⁵-Me₄C₅)Si(Me)(CH₂CH=CH₂)NCH₂CH=CH₂]TiMe₂（）、[(η⁵-Me₄C₅)Si (Me)(CH=CH₂)NCH₂CH=CH₂]TiMe₂（）和[(η⁵-Me₄C₅)Si(Me)(CH₂CH₃)NCH₂CH₂CH₃]TiMe₂（）。当用[Ph₃C][B(C₆F₅)₄]/iBu₃Al活化时，新制备的配合物的催化活性低于CGC。然而，通过使用四丁基铝氧烷（[iBu₂Al]₂O）代替iBu₃Al，这些物质的催化活性得到了提高，并且[Ph₃C][B(C₆F₅)₄]/[iBu₂Al]₂O的活性与CGC/[Ph₃C][B(C₆F₅)₄]/iBu₃Al的活性相当（分别为4.7和5.0×10⁶ g/mol-Ti）。有利的是，新制备的配合物生成的聚（乙烯 - 1 - 辛烯）的分子量高于CGC。
