Z-Selective Semihydrogenation of Alkynes Catalyzed by a Cationic Vanadium Bisimido Complex
Z-Selective Semihydrogenation of Alkynes Catalyzed by a Cationic Vanadium Bisimido Complex
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DOI：
10.1002/anie.201007876
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发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Toste, F. Dean
中科院分区：
文献类型：
--
作者：
La Pierre, Henry S.;Arnold, John;Toste, F. Dean
早过渡金属加氢催化剂受到的关注比类似的晚过渡金属体系少，特别是自从Wilkinson催化剂的发现以来这种对后期过渡金属系统的强调主要是由实际问题驱动的，包括功能组的容忍度和易于处理。从两个角度进一步研究早期过渡金属体系特别有吸引力：1)识别和阐明二氢活化的不寻常机制；2)应用早期过渡金属的固有性质，特别是高价配合物，选择性地将炔加氢成Z烯烃。这种转化通常是由Lindlar催化剂完成的，实际上很难使用，特别是在共轭芳香体系中，受到E/Z异构化和过氢化的影响开发这种转化的有效分子催化剂仍然是一个深入研究的领域，最近取得了显著的成功我们之前报道了1,2 - SiÀH σ键加到[ReIO2 (PPh3) 2]的氧配体上在酮的催化硅氢化反应中的中间作用我们假设正确连接的[ReIO2 (PPh3) 2]的第5族类似物可以激活二氢并区分烯烃和炔烃，因为烯烃是特别差的配体。H2在金属配体多键上的1,2加成（如LnM= X； X= O,[5] S,[6] NR[7]）是一种相对罕见的转化，其催化潜力尚未得到严格的研究。为了将先前建立的通过极化金属配体多键对H2的早期过渡金属活化与有机底物的催化还原结合起来，我们寻找了一种由不稳定配体支撑的二亚胺钒。本文报道了钒二甲基配合物[V (NtBu) 2 (PMe3) 3][Al-]的合成
Early-transition-metal hydrogenation catalysts have received less attention than comparable late-transition-metal systems, particularly since the discovery of Wilkinson s catalyst.[1] This emphasis on late-transition-metal systems has been largely driven by practical concerns including functional-group tolerance and ease of handling. Further examination of early-transition-metal systems is particularly attractive from two viewpoints: 1) the identification and elucidation of unusual mechanisms of dihydrogen activation and 2) the application of the intrinsic properties of early transition metals, in particular high-valent complexes, to the selective hydrogenation of alkynes to Z alkenes. This transformation is typically accomplished by Lindlar s catalyst, and is practically difficult to employ and suffers, particularly in the case of conjugated aromatic systems, from E/Z isomerization and over-hydrogenation.[2] The development of effective molecular catalysts for this transformation remains an area of intense research with recent notable success.[3] We previously reported the intermediacy of a 1, 2-addition of a SiÀH σ bond to an oxo ligand of [ReIO2 (PPh3) 2] in the catalytic hydrosilylation of ketones.[4] We hypothesized that a properly ligated Group 5 analogue of [ReIO2 (PPh3) 2] could afford the activation of dihydrogen and discriminate between alkenes and alkynes, as alkenes are particularly poor ligands for d0 complexes. The 1, 2-addition of H2 to metal–ligand multiple bonds (eg LnM= X; X= O,[5] S,[6] NR [7]) is a relatively rare transformation and its potential in catalysis has not been rigorously pursued. To combine the previously established early-transition-metal activation of H2 by polarized metal–ligand multiple bonds with catalytic reduction of organic substrates, we sought a vanadium bisimide supported by labile ligands. Herein we report the synthesis of the cationic vanadium bisimido complex [V (NtBu) 2 (PMe3) 3][Al-