Isolation of a 1,2-dialuminacyclobutene
Isolation of a 1,2-dialuminacyclobutene
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DOI：
10.1002/anie.200504329
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Zhu, XQ
中科院分区：
文献类型：
--
作者：
Cui, CM;Li, XF;Zhu, XQ
近年来，包含重主族元素的小环体系由于其独特的结构特征和高反应活性而引起了人们的广泛关注。[1，2，3]在这些环中，含有三配位的第13族元素和烯烃-碳单元的那些（环丙烯和环丁烯类似物）特别有吸引力，因为它们分别与Hückel芳族系列的最小成员（即环丙烯鎓离子和环丁二烯二价阳离子）等电子。碳硼烷（CH）_2（BH）_n（n= 1，2）及其衍生物在实验和理论上都得到了广泛的研究。[2]因此，（CH）2（BH）2的理论研究表明，稳定的1，3-二戊烯异构体优先采用非平面，起皱的几何形状类似于（CH）2（BH）4的预测，这随后被实验验证。[2]因此，形式上2π MC 2和M2 C2环（M= Al，Ga，In，Tl）的较重同系物的合成和表征由于其潜在的芳香性而具有根本的兴趣。令人惊讶的是，这样的环系统在文献中是罕见的。最近报道的具有大体积配体的环丙烯衍生物的AlC 2环是这一系列中唯一已知的例子，其中铝原子都是四配位的。[3]稳定的金属环丁烯M2 C2环含有M2 C2键，至今仍是未知的。本文报道了1，2-二铝环丁烯（Ar'Al）_2（CSiMe_3）_2（2; Ar'= 2，6-Dipp_2C_6 H_3，Dipp= 2，6-iPr_2C_6 H_3）的合成和单晶X-射线结构。最初由Power及其同事制备的庞大的三联苯配体Ar '已被证明对单价较重的13族元素的稳定是有效的。[4]然而，“二铝烯”Ar'AlAlAr'还没有被分离出来，并且被假定为在从甲苯中结晶时通过[2+ 4]环加成形成双环Al 2C 6环的中间体。[5]我们对这一系统的兴趣源于最近的发现，
In recent years, small-ring systems that incorporate heavier main-group elements have drawn intense attention because of their unique structural features and high reactivity.[1, 2, 3] Among such rings, those which contain three-coordinate Group 13 elements and olefinic-carbon units (cyclopropene and cyclobutene analogues) are particularly attractive since they are isoelectronic with the smallest members of the Hückel aromatic series, that is, the cyclopropenium ion and the cyclobutadiene dication, respectively. The carboranes (CH) 2 (BH) n (n= 1, 2) and their derivatives have been intensively investigated both experimentally and theoretically.[2] Thus, theoretical studies of (CH) 2 (BH) 2 revealed that the stable 1, 3-diboretene isomer preferentially adopted a nonplanar, puckered geometry similar to that predicted for (CH) 2þ4, which was subsequently verified experimentally.[2] Accordingly, the synthesis and characterization of the heavier congeners of the formally 2π MC2 and M2C2 rings (M= Al, Ga, In, Tl) are of fundamental interest as a result of their potential aromaticity. Surprisingly, such ring systems are rare in the literature. The recently reported AlC2 rings of cyclopropene derivatives with bulky ligands are the only known examples in this series, in which the aluminum atoms are all four-coordinate.[3] Stable metallacyclobutene M2C2 rings which contain MÀM bonds have remained unknown until now. Herein, we report the synthesis and single-crystal X-ray structure of the 1, 2-dialuminacyclobutene (Ar’Al) 2 (CSiMe3) 2 (2; Ar’= 2, 6-Dipp2C6H3, Dipp= 2, 6-iPr2C6H3). The bulky terphenyl ligand Ar’, which was originally prepared by Power and co-workers, has proved effective for the stabilization of monovalent heavier Group 13 elements.[4] However, the “dialuminene” Ar’AlAlAr’has not been isolated and was postulated as an intermediate in the formation of a bicyclic Al2C6 ring through a [2+ 4] cycloaddition upon crystallization from toluene.[5] Our interest in this system stems from the recent findings that aluminum