Intramolecular (sp³-hybridized) C−H Activation: Yttrium Alkyls versus Transient Yttrium Hydrides

Abstract

Most likely a hydrid species is formed in the course of this reaction, which undergoes rapid C-H actiVation since 3 is formed from 2 directly about 500 times slower than in the presence of 1 equiV of PhSiH 3 . Molecular structures of complexes 2 and 3 haVe been confirmed by X-ray crystal structure analysis.Even after a lapse of twenty-five years since the pioneering works on the synthesis of the first molecular rare earth metal hydrido complexes, 1 these compounds still attract considerable attention 2 and remain one of the most promising classes of compounds for various catalytic applications. 3 Enhanced reactivity of hydrido complexes, which allows even C-F bond activation, 4 gives evidence of their high potential in stoichiometric reactions. Until very recently rare earth metal hydrides were represented exclusively by sandwich-2 and half-sandwichtype ("constrained geometry") 5 complexes. Remarkable progress has been made in this field, and the formerly challenging monomeric 4 and dihydrido 6 species became a reality. The hydride supported by benzamidinate ligands {[PhC(NSiMe 3 ) 2 ] 2 Y-(µ-H)} 2 7 synthesized by Teuben and co-workers in 1993 was the first and for a long time the sole example of a cyclopentadienyl-free rare earth metal hydrido complex. The recent advances in rare earth metal hydrido chemistry 8 are linked to application of novel types of coordination environments: bis-(silylamido)biphenyl, 9a calyx-tetrapyrrol, 9b,c salicylaldimine, 9d,e tris(pyrazolil)borate. 9f However, to date, "post-metallocene" hydrides still remain a rarity. Recently we reported the synthesis of the series of hydrido lanthanide complexes supported by bulky tetrasubstituted guanidinate ligands, which have demonstrated high catalytic activity in olefin polymerization. 10 Sterically demanding aminopyridinato ligands 11 were also successfully used as a suitable coordination environment for stabilization of monomeric lanthanide species. Both guanidinate and aminopyridinate frameworks have a common feature: a chelating monoanionic planar NCN moiety. In order to investigate the influence of ancillary ligation on the reactivity of the Y-H and Y-C bonds, we decided to employ the aminopyridinate ligation system for synthesis of alkyl and hydrido complexes. Herein we report on the exiting outcomes of the attempts to synthesize alkyl and hydrido yttrium complexes supported by the bulky aminopyridinate ligand system. Bulky 2,6-(diisopropylphenyl)-[6-(2,6-dimethylphenyl)pyridin-2-yl]amine (Ap′-H) (Scheme 1) 11a,b was used as the ligand For example see, hydrogenation: (a) Jeske, G.; Lauke, H.; Mauermann, H.; Schumann, H.; Marks, T. J. J. Am. Chem. Soc. 1985, 107, 8111-8118. (b) Conticello, V. P.; Brard, L.; Giardello, M. A.; Tsyji, Y.; Sabat, M.; Stern, C. L.; Marks, T. J. Lauke, H.; Mauermann, H.; Swepston, P. N.; Schumann, H.; Marks, T. J. (a) Trifonov, A. A.; Fedorova, E. A.; Fukin, G. K.; Bochkarev, M. N. Eur. J. Inorg. Chem. 2004, 4396-4401. (b) Trifonov, A. A.; Skvortsov, G. G.; Lyubov, D. M.; Skorodumova, N. A.; Fukin, G. K.; Bar...

Sixty Years of the Chemistry of Rare-earth Organometallic Complexes

“…稀土三烷基配合物和大立体位阻脒基配体 进行烷烃消除反应, 可合成一系列的单脒基稀土双烷基 配合物, 其再与硼盐反应生成相应的稀土单烷基阳离子 配合物(图 37) [198] . 这些稀土单烷基阳离子配合物可以 催化乙烯聚合, 催化活性强烈依赖于 Ln 3＋ 的离子半径, 最大的 La [204] , 通过控制 [Ap′K] n 或 [Ap*K] n 的 用量也能得到氯化物和二氯化物 [205,206] . 胺基吡啶二价 镱配合物[(Ap′) 2 Yb]也被合成得到 [207] .…”

“…图 39 大位阻胺基吡啶配体 Figure 39 Bulky aminopyridine 将胺基吡啶稀土氯化物进行烷基化生成烷基配合 物, 该配合物不稳定, 室温下即可发生分子内 sp 3 C-H 键活化反应(图 40) [205] . 三烷基钇与胺基吡啶进行烷烃 消除反应, 生成的单烷基配合物随即发生 sp 2 C-H 键 活化反应生成苯基钇环状配合物, 该产物与 PhSiH 3 反 应生成二聚体氢化物 [208] .…”

C‐H‐Aktivierung mit Komplexen der f‐Block‐Elemente

“…Obwohl viele hervorragend stabilisierende Gerüste existieren, ist die nicht vorhergesehene Metallierung, obgleich manchmal umkehrbar, immer noch ein großes Problem. [33] Die thermische Zersetzung von [{(Me 3 Si) 2 [34] Kürzlich haben wir eine neue In-situ-Aren-C-H-Bindungsmetathese-Methode entwickelt, um C-H-in C-B-Bin-dungen umzuwandeln (Schema 7 c). Wenn man Aren-Lç-sungen von einfachen Urankomplexen UX 3 2 ] entsteht, beobachtet.…”

Yttrium‐Amidopyridinate Complexes: Synthesis and Characterization of Yttrium‐Alkyl and Yttrium‐Hydrido Derivatives

“…[18] Related yttrium complexes that contain an amidopyridinate ligand with a shorter ligand backbone [21] have shown a dramatic perturbation of the ligand coordination mode once an intramolecular C-H bond activation occurs {the Y-N covalent bond [2.431(8) Å] becomes longer than the coordinative one [2.338(7) Å]}. In contrast to this, the presence of an additional CMe 2 group between the two nitrogen atoms always results in a "classic" bonding mode (Y-N covalent bonds shorter than coordinative ones; Table 2).…”