Carbonylation of Cyclotrisilenes
Carbonylation of Cyclotrisilenes
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DOI：
10.1002/anie.201307450
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发表时间：
2013-12-09
影响因子：
16.6
通讯作者：
Scheschkewitz, David
中科院分区：
文献类型：
--
作者：
Cowley, Michael J.;Ohmori, Yu;Scheschkewitz, David
一氧化碳（CO）是过渡金属化学中一种常见的配体。在有机化学中，它经常用于引入C1单元，尽管羰基化，如氢甲酰化[1]或Pauson-Khand反应[2]通常需要过渡金属催化剂，即使是应变（因此反应性很强）的环化合物关于CO对除碳以外的主族元素化合物的反应性的报道很少。虽然自20世纪30年代施莱辛格和伯格的开创性工作以来，[4]硼烷- co加合物通常在室温下是不稳定的。直到最近，皮尔斯等。氢化硼酸（F5C6） 2BH在受挫Lewis对（FLP）机制中加入了CO和烷基官能化磷化氢AB (C6F5) 3基FLP能够用二氢还原CO一些配位不饱和的刘易斯酸性有机物质，如瞬态三态碳烯，[8]和Bertrand s环烷基氨基碳烯在没有过渡金属的情况下与CO反应，形成酮尽管越来越多的人认识到主要基团物种能够激活小分子，如H2和NH3，但据我们所知，重元素与CO的稳定低价化合物的[10]反应还没有报道。然而，在气相和冷基体中观察到瞬态硅烷- co加合物我们最近表明，环三硅烯与n -杂环碳烯（NHCs）可逆反应产生环三硅烯- nhc加合物[12]，在1a的情况下，[12]可以可逆开环形成高度不饱和nhc稳定的二乙烯基硅烯。[12b]异腈也能与环三烯[13]反应，考虑到与CO的等电子关系，我们对后者的反应性产生了兴趣。在此，我们报告了一氧化碳与环三硅烯在没有催化剂的情况下容易反应形成高官能化环硅烯。将环三硅烯1a的苯溶液在258C下暴露于1atm的CO中，会在几小时内析出一种黄色粉末，由于其不溶性，无法用光谱表征在其他条件相同的情况下，连续反应几天不搅拌，就会得到亮黄色的单晶。元素分析证实每个1a分子中含有一等量的CO。x射线晶体学显示产物为三环布鲁克型[15]bis（沉默烯）2a，形式上由1a和CO两个分子各产生（方案1，图1）
Carbon monoxide (CO) is a common ligand in transitionmetal chemistry. In organic chemistry, it is frequently used to introduce a C1 unit, although carbonylations, such as hydroformylation [1] or the Pauson–Khand reaction,[2] generally require a transition-metal catalyst, even for strained (and thus highly reactive) cyclic compounds.[3] Only a few reports on the reactivity of CO towards compounds of main-group elements other than carbon are available. Although known since the pioneering work by Schlesinger and Burg in the 1930s,[4] borane–CO adducts are usually unstable at room temperature. Only recently, Piers etal. reported a stable adduct between the very Lewis acidic perfluorinated pentaphenylborole and CO.[5] The hydroborating Lewis acid (F5C6) 2BH incorporates CO assisted by a alkenyl-functionalized phosphine in a frustrated Lewis pair (FLP) mechanism.[6] AB (C6F5) 3-based FLP is capable of stoichiometric CO reduction with dihydrogen.[7] A few coordinatively unsaturated and thus Lewis acidic organic species, such as transient triplet carbenes,[8] and Bertrand s cyclic alkyl amino carbenes react with CO in the absence of transition metals, forming ketenes.[9] Despite growing appreciation of the capability of main group species to activate small molecules, such as H2 and NH3,[10] reactions of stable low-valent compounds of the heavier elements with CO have not, to our knowledge, been reported. Transient silylene–CO adducts, however, have been observed in the gas phase and in cold matrices.[11] We have recently shown that reactions of cyclotrisilenes with N-heterocyclic carbenes (NHCs) reversibly afford cyclotrisilene–NHC adducts,[12] which in the case of 1a can undergo reversible ring-opening to form a highly unsaturated NHC-stabilized disilenylsilylene.[12b] Isonitriles also react with cyclotrisilenes,[13] and, mindful of the isoelectronic relationship to CO, we became interested in the reactivity of the latter. Herein, we report the facile reaction of carbon monoxide with cyclotrisilenes in the absence of a catalyst to form highly functionalized cyclic silenes. Exposure of a benzene solution of cyclotrisilene 1a to 1atm of CO at 258C results in precipitation of a yellow powder within a few hours, which owing to its insolubility cannot be characterized spectroscopically.[14] A reaction for several days without stirring under otherwise identical conditions afforded bright yellow single crystals. Elemental analysis confirmed the incorporation of one equivalent of CO per molecule of 1a. X-ray crystallography revealed the product to be the tricyclic Brook-type [15] bis (silene) 2a, formally arising from two molecules each of 1a and CO (Scheme 1, Figure 1).[14]