Selective dimetalation of [Mn(eta5-C5H5)(eta6-C6H6)]: crystal structure and conversion to strained [n]metalloarenophanes.
Selective dimetalation of [Mn(eta5-C5H5)(eta6-C6H6)]: crystal structure and conversion to strained [n]metalloarenophanes.
复制标题
[Mn(eta5-C5H5)(eta6-C6H6)] 的选择性二金属化：晶体结构和向应变[n]金属芳烃的转化。
DOI：
10.1002/anie.200604391
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发表时间：
2007
影响因子：
--
通讯作者：
K. Radacki
中科院分区：
文献类型：
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作者：
H. Braunschweig;T. Kupfer;K. Radacki
在过去的15年里，由于其独特的结构、成键和反应模式，应变柄复合物的化学研究受到越来越多的关注。[1]一般来说，这类有机金属化合物是通过二金属化的二烯烃与元素二卤化物的化学计量的盐消除反应来制备的。因此，选择性二金属化和明确的三明治前体的应用对于该反应和一般茂金属络合物的官能化是必不可少的。在配位胺如N，N，N ′，N ′-四甲基乙二胺（tmeda）或N，N ′，N ′，N“，N”-五甲基二亚乙基三胺（pmdta）存在下，采用烷基锂碱，使均配夹心配合物[M（η5-C5 H5）2]的双去质子化（M= Fe，[2] Ru [3]）和[M（η_6-C_6H_6）_2]（M= V，[4] Cr [5]），以及混配物种[M（η_5-C_5H_5）（η_7-C_7H_7）]（M= Ti，[6] V，[7] Cr [1f]）。然而，除了双硫代二茂铁衍生物[Fe（η5-C5 H4 Li）2]· pmdta [8]和[Fe（η5-C5 H4 Li）2] 3·（tmeda）2 [9]之外，迄今为止，双金属双茂的结构数据非常罕见。最近Mulvey和同事报道了二茂铁及其高级同系物的选择性四金属化[10]，双（苯）铬的协同单去质子化[11]和二茂铁的选择性二金属化[12]，通过混合的碱金属镁酰胺碱沿着相应的晶体结构分析。在我们最近的研究过程中，紧张的金属arenophans，我们开始感兴趣的含锰柄络合物。由于茂锰[Mn（η5-C5 H5）2]不能在不分解的情况下金属化，已知柄型配合物的数量仅限于一个结构表征的实例。[13]因此，我们主要关注最初由Fischer和Breitschaft在1966年报道的混配夹心配合物[Mn（η5-C5 H5）（η6-C6 H6）]（1）。[14]该化合物已经成为几个光谱[15]和理论研究的主题，[16]然而，迄今为止尚未详细研究其反应性，最可能是因为无休止的低产率合成（2-4%）。然而，应该注意的是，一些早期的研究表明，在tmeda存在下，1与BuLi反应时对去质子化的敏感性。[17]因此获得的材料没有被表征，而是用各种元素卤化物原位淬火。从捕集产物的性质，包括提出的[2]硅锰芳烷，[17 b，c]，形成一个硫化茂金属中间体似乎是合理的。然而，捕获产物的构成仅从NMR数据推断，并且由于起始材料的不完全金属化，在各种情况下获得不可分离的产物混合物。[17b]在此，我们报道了1的容易和选择性的去质子化，导致结构特征的二金属化物质，以及其转化为第一个结构特征的硼和硅桥连的[n]锰芳烷（n= 1，通过在室温下使用2.7当量丁基锂和pmdta在脂族溶剂中的混合物实现1的选择性双去质子化，得到碱-稳定配合物[Mn（η_5-C_5H_4Li）（η_6-C_6H_5Li）]· pmdta（2）。化合物2可以以高达85%的高产率分离为浅棕色自燃粉末（方案1）。[18个国家]
During the last 15years the chemistry of strained ansa complexes has been of growing interest as a result of their unique structure, bonding, and reactivity patterns.[1] In general, this class of organometallic compounds is prepared by stoichiometric salt-elimination reactions of dimetalated metallocenes with element dihalides. Hence, the application of a selectively dimetalated and well-defined sandwich precursor is essential for this reaction and for the functionalization of metallocene complexes in general. By employing alkyl lithium bases in the presence of a coordinating amine such as N, N, N’, N’-tetramethylethylenediamine(tmeda) or N, N’, N’, N’’, N’’-pentamethyldiethylenetriamine (pmdta) the double deprotonation of the homoleptic sandwich complexes [M (η5-C5H5) 2](M= Fe,[2] Ru [3]) and [M (η6-C6H6) 2](M= V,[4] Cr [5]), as well as the heteroleptic species [M (η5-C5H5)(η7-C7H7)](M= Ti,[6] V,[7] Cr [1f]), has been accomplished. However, except for the dilithiated ferrocene derivatives [Fe (η5-C5H4Li) 2]· pmdta [8] and [Fe (η5-C5H4Li) 2] 3·(tmeda) 2 [9] structural data of dimetalated metallocenes are acutely rare to date. Very recently Mulvey and co-workers reported on the selective tetrametalation of ferrocene and its higher homologues,[10] the synergic monodeprotonation of bis-(benzene) chromium,[11] and the selective dimetalation of ferrocene [12] by mixed alkali-metal–magnesium amide bases along with the corresponding crystal structure analyses. In the course of our recent studies on strained metalloarenophanes, we became interested in manganese-containing ansa complexes. Since manganocene [Mn (η5-C5H5) 2] cannot be metalated without decomposition, the number of known ansa complexes is limited to one structurally characterized example.[13] Therefore, we focused mainly on the heteroleptic sandwich complex [Mn (η5-C5H5)(η6-C6H6)](1) originally reported by Fischer and Breitschaft in 1966.[14] This compound has been the subject of several spectroscopic [15] and theoretical investigations,[16] however, the reactivity has not been investigated in detail so far, most probably because of the interminable low-yield synthesis (2–4%). It should be noted, though, that a few earlier studies indicated the susceptibility of 1 towards deprotonation upon reaction with BuLi in the presence of tmeda.[17] The material thus obtained was not characterized but quenched insitu with various element halides. From the nature of the trapping products, including a proposed [2] silamanganoarenophane,[17b, c] the formation of a dilithiated metallocene intermediate appears plausible. The constitution of the trapping products, however, was deduced solely from NMR data, and owing to incomplete metalation of the starting material, inseparable product mixtures were obtained in various cases.[17b] Herein we report on the facile and selective deprotonation of 1, leading to a structurally characterized dimetalated species, and its conversion to the first structurally characterized boron-and silicon-bridged [n] manganoarenophanes (n= 1, 2).Selective double deprotonation of 1 was achieved by employing a mixture of 2.7 equivalents of butyllithium and pmdta in aliphatic solvents at room temperature to afford the base-stabilized complex [Mn (η5-C5H4Li)(η6-C6H5Li)]· pmdta (2). Compound 2 can be isolated as a pale-brown, pyrophoric powder in high yields up to 85%(Scheme 1).[18]