A concave-bound CpFe complex of sumanene as a metal in a π bowl
A concave-bound CpFe complex of sumanene as a metal in a π bowl
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DOI：
10.1002/anie.200702826
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Hirao, Toshikazu
中科院分区：
文献类型：
--
作者：
Amaya, Toru;Sakane, Hiroyuki;Hirao, Toshikazu
配位是金属结合的主要方式之一。各种平面π共轭化合物以ηn方式与金属结合。另一方面，自从富勒烯和碳纳米管的发现以来，金属与弯曲的碳π表面结合的方式吸引了持续的兴趣。迄今为止，已经发现富勒烯的外π表面充当各种过渡金属的η2-配位配体。[1]对于改性富勒烯π体系，报道了exo络合物中的其他配位模式。[2]还已知富勒烯和碳纳米管形成内配体金属络合物以在碳化学中提供潜在有用的材料。[3]在富勒烯碎片（称为“巴基碗”或碗状烃）的配位化学中，有一个有趣的问题，即金属优先结合到凸面而不是凹面（图1A，B），这是1993年半富勒烯（C30 H12）的计算研究首次提出的。[4]迄今为止，已经制备和表征了几种巴基碗的配位络合物，例如corannulene（C60的C20亚基，图1D）。[5]在某些单取代的corannulene配合物的X射线晶体结构中显示出凸键，包括η1，η2和η6配位模式。[5a最近利用密度泛函理论对corannulene及其衍生物的配合物的理论研究也表明了对过渡金属的优先凸结合。[6]另一方面，钌（II）与corannulene或四甲基corannulene的凸键和凹键都有报道。[5f此外，在气相沉积反应下实现了corannulene和hemifullerene的三金属化和四金属化;金属中心以η2结合结合到凸面和凹面两者。[5e然而，凹选择性配合物从未被分离或预测的分子计算，除了在从头计算研究碱金属阳离子和Ga+的半富勒烯的结合。[7]凹配位被认为提供了一种合成富勒烯或碳纳米管包合物的途径，这些包合物在各个领域具有潜在的应用，例如分子电子学[8]和磁共振成像。[9]Sumanene（1，C21 H12，图1C）是C60的关键C3 v对称部分结构，于2003年首次合成。[10]它有一个比corannulene更深的碗（1.11），并表现出缓慢的碗到碗倒置。此外，通过与苄基碳负离子形成亲核键，允许容易的衍生化。[11]苏曼烯的各种配位模式，包括η1、η2、η4、η5和η6，都是可以想象的，但其与过渡金属的配位化学仅限于预测{Pt（PH 3）2}以η2方式凸结合的计算研究。[12]从这一点来看，在碗里“抓住”一块金属是很有挑战性的。本文首次合成了苏曼烯与{CpFe}+（Cp= C5 H5）的凹键配合物。苏曼烯的金属化反应是通过与二茂铁的一个带取代基的配体交换进行的。反应在铝粉和氯化铝存在下、无溶剂、氩气和120 ℃下进行19小时。用六氟磷酸盐代替粗络合物的抗衡阴离子，得到呈橙子固体的[CpFe（苏曼烯）] PF 6（2）（方案1）。使用过量的二茂铁和氯化铝，以91%的产率选择性地得到所需的单取代络合物。在十氢萘作为溶剂中的反应没有产生2。高分辨率FAB质谱图中的母峰...
Coordination is one of the key modes in metal binding. A variety of planar π-conjugated compounds bind to metals in an ηn fashion. On the other hand, the way in which metals bind to curved carbon π surfaces has attracted continuous interest since the discovery of fullerenes and carbon nanotubes. To date, the exo π surfaces of fullerenes have been found to act as η2-coordination ligands to various transition metals.[1] Other coordination modes in exo complexes were reported for modified fullerene π systems.[2] Fullerenes and carbon nanotubes are also known to form endohedral metal complexes to provide potentially useful materials in carbon chemistry.[3] In the coordination chemistry of fullerene fragments, called “buckybowls” or bowl-shaped hydrocarbons, there is the intriguing issue of the preference for metal binding to the convex surface versus the concave one (Figure 1A, B), which was first addressed by the computational study of hemifullerene (C30H12) in 1993.[4] To date, few coordination complexes of buckybowls, such as corannulene (a C20 subunit of C60, Figure 1D), have been prepared and characterized.[5] Convex binding, including η1, η2, and η6-coordination modes, was displayed in the X-ray crystal structures of some monometalated corannulene complexes.[5a, k, m–q] Recent theoretical studies on complexes of corannulene and its derivatives using density functional theory also indicated preferential convex binding to transition metals.[6] On the other hand, both convex and concave binding of ruthenium (II) to corannulene or tetramethylcorannulene with η6 coordination has been reported.[5f, p, k] Furthermore, tri-and tetrametalation of corannulenes and hemifullerene were achieved under gas-phase deposition reactions; metal centers were bound to both convex and concave faces with η2 binding.[5e, j, g, r] However, a concave-selective coordination complex has never been isolated or predicted by molecular calculations, except in abinitio studies on the binding of alkali-metal cations and Ga+ to hemifullerene.[7] Concave coordination is considered to provide a route toward the synthesis of inclusion complexes of fullerenes or carbon nanotubes, which have potential applications in various fields, such as molecular electronics [8] and magnetic resonance imaging.[9]Sumanene (1, C21H12, Figure 1 C) is the key C3v symmetric partial structure of C60 and was first synthesized in 2003.[10] It has a deeper bowl (1.11) than corannulene and exhibits slow bowl-to-bowl inversion. Furthermore, facile derivatization is permitted by nucleophilic bond formation with the benzylic carbanions.[11] Various coordination modes, including η1, η2, η4, η5, and η6, are conceivable with sumanene, but its coordination chemistry with transition metals has been limited to a computational study that predicts convex binding of {Pt (PH3) 2} in an η2 fashion.[12] From this point of view, it is challenging to “catch” a metal in the bowl. Herein, we report the first synthesis of the concave-binding complex of sumanene with {CpFe}+(Cp= C5H5). The metalation of sumanene was performed by ligand exchange with a cyclopentadienyl group of ferrocene. The reaction proceeded in the presence of aluminum powder and aluminum chloride without solvent under argon at 1208C for 19 h. The counteranion of the crude complex was replaced by hexafluorophosphate, giving [CpFe (sumanene)] PF6 (2) as an orange solid (Scheme 1) The use of excess ferrocene and aluminum chloride selectively afforded the desired monometalated complex in 91% yield. Reaction in decahydronaphthalene as solvent did not yield 2. The parent peak in the high-resolution FAB mass …