Tanuhadi Elias, Bair Anna S, Johnson Mary, Fontaine Philip, Klosin Jerzy, Pal Sudipta, Arnold Polly L
Dept of Chemistry, University of California, Berkeley Berkeley CA 94720 USA
Chemical Sciences Division, Lawrence Berkeley National Laboratory Berkeley CA 94720 USA.
Chem Sci. 2024 Nov 25;16(1):280-287. doi: 10.1039/d4sc05983b. eCollection 2024 Dec 18.
Rare earth tris(alkyl) complexes such as M(CHSiMe)(sol) are widely used as precursors for many compounds and as homogeneous catalysts for alkene polymerization and alkane functionalization. However, the thermal instability of those most conveniently made from the commercially available lithium salt of the neosilyl anion, LiCHSiMe, Li(r), restricts their utility. We present a new range of synthetically useful, more kinetically stable rare earth neosilyl solvates, derived from a full kinetic study of the various possible decomposition mechanisms of 7 known and 12 new solvated rare earth neosilyl complexes M(CHSiMe)(sol) M = Sc(iii), Y(iii), Lu(iii), Sm(iii), and sol = THF; TMEDA; DMPE; diglyme ((CH)(OCHCH)O, G), triglyme ((CH)(OCHCH)O, G). Surprisingly, simply using higher-denticity donors to sterically disfavor neosilyl -H elimination is not effective. While Sc(r)((CH)(OCHCH)O) has a half-life, , of 258.1 h, six times longer than for Sc(r)(CHO) ( = 43 h), Lu(r)((CH)(OCHCH)O) and Y(r)((CH)(OCHCH)O) do not show the expected, analogous increased . This is because new decomposition pathways appear for poorly fitting donors. Finally, kinetic studies demonstrate the impact of small, and increasing amounts of LiCl on the kinetics of the reactivity of the smaller alkyls Y(r)(THF) and Lu(r)(THF); molecules used in hydrocarbon chemistry and catalysis for fifty years. A new route to pure Y(r)(THF), which avoids the traditional use of Li(r), is presented.
稀土三（烷基）配合物，如M(CHSiMe)(sol)，被广泛用作许多化合物的前体以及烯烃聚合和烷烃官能化的均相催化剂。然而，那些最方便地由新硅基阴离子的市售锂盐LiCHSiMe、Li(r)制备的配合物的热不稳定性限制了它们的实用性。我们提出了一系列新的、合成上有用的、动力学上更稳定的稀土新硅基溶剂化物，这是通过对7种已知的和12种新的溶剂化稀土新硅基配合物M(CHSiMe)(sol)（M = Sc(iii)、Y(iii)、Lu(iii)、Sm(iii)，sol = THF；TMEDA；DMPE；二甘醇二甲醚((CH)(OCHCH)O, G)、三甘醇二甲醚((CH)(OCHCH)O, G)）的各种可能分解机制进行全面的动力学研究而得出的。令人惊讶的是，仅仅使用更高齿合度的给体在空间上不利于新硅基 -H消除是无效的。虽然Sc(r)((CH)(OCHCH)O)的半衰期 为258.1小时，比Sc(r)(CHO)（ = 43小时）长六倍，但Lu(r)((CH)(OCHCH)O)和Y(r)((CH)(OCHCH)O)并没有表现出预期的类似增加的 。这是因为对于适配性差的给体出现了新的分解途径。最后，动力学研究证明了少量且不断增加的LiCl对较小烷基Y(r)(THF)和Lu(r)(THF)反应动力学的影响；这两种分子已在烃类化学和催化中使用了五十年。本文提出了一种避免传统使用Li(r)来制备纯Y(r)(THF)的新方法。
