Indenyl Complexes of Manganese(II). Conformational Flexibility of the Manganese(II)−(RnC9H7−n) Bond

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• 作者：Jeffrey A. Crisp ; Ryan M. Meier ; Jason S. Overby ; Timothy P. Hanusa ; Arnold L. Rheingold ; William W. Brennessel
• 刊名：Organometallics
• 出版年：2010
• 出版时间：May 24, 2010
• 年：2010
• 卷：29
• 期：10
• 页码：2322-2331
• 全文大小：1043K
• 年卷期：v.29,no.10(May 24, 2010)
• ISSN：1520-6041

文摘

Bis(cyclopentadienyl) complexes (Cp₂M) of the divalent first-row transition metals V−Ni have been known and used for over 50 years. For almost as long, an analogous series of compounds has been known with the indenyl ligand (i.e., Ind₂M), with the conspicuous exception of M = Mn. Bis(indenyl) complexes of manganese(II), Ind′₂MnL_n, have now been synthesized by halide metathesis from MnCl₂ and an appropriate potassium indenide. Depending on the indenyl ligand substituents and the presence of coordinated bases, a variety of structural motifs and bonding modes of the indenyl ligand are found in the resulting complexes. Single-crystal X-ray structures obtained for [2-(SiMe₃)C₉H₆]₂Mn, [1,3-(SiMe₃)₂C₉H₅]₂Mn, and [1,3-(i-Pr)₂C₉H₅]₂Mn confirm that they possess classic η⁵-bound sandwich structures. In contrast, the unsubstituted parent complex recrystallizes from THF as a disolvate with two differently bonded indenyl ligands: i.e., (η³-C₉H₇)(η¹-C₉H₇)Mn(thf)₂. Without the coordinated solvent, density functional theory calculations suggest that the complex would have two slipped η⁵-bound ligands. When methyl groups are present on the benzo portion of the indenyl ligand, specifically in the 4,7-positions, the corresponding manganese complex is isolated as a cyclic octomer, {(4,7-Me₂C₉H₅)₂Mn}₈, containing both bridging and terminal indenyl ligands. In the presence of 1,4-dioxane, however, attempted synthesis of (4,7-Me₂C₉H₅)₂Mn results in the isolation of the [K(dioxane)_1.5][Mn(4,7-Me₂C₉H₅)₃] salt, in which each manganese atom is surrounded by a paddlewheel of three η²-bound 4,7-dimethylindenyl ligands. Cation−π bonding to the potassium and the presence of coordinated dioxane molecules generates a layered structure for the salt. Magnetic susceptibility measurements on the compounds indicate the presence of high-spin Mn(II) centers in all cases. These compounds demonstrate the high degree of conformational flexibility in the Mn(II)−indenyl bond.