Synthesis, Dynamics, and DFT Studies of Rhenium Dicarbonyl PNN Pincer Complexes in Three Different Oxidation States

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• 作者：Kothanda Rama Pichaandi ; Michael G. Mazzotta ; John S. Harwood ; Phillip E. Fanwick ; Mahdi M. Abu-Omar
• 刊名：Organometallics
• 出版年：2014
• 出版时间：April 14, 2014
• 年：2014
• 卷：33
• 期：7
• 页码：1672-1677
• 全文大小：299K
• 年卷期：v.33,no.7(April 14, 2014)
• ISSN：1520-6041

文摘

The synthesis and characterization of Re<sup>Isup> and Re<sup>IIsup> dicarbonyl halides 1 and 2 and the Re<sup>IIIsup> dicarbonyl dihalide 3 supported by a PNN pincer ligand are described. Complex 1 (1a, X = Br; 1b, X = Cl) was synthesized by refluxing the PNN ligand with Re(CO)<sub>5sub>X (X = Br, Cl) in toluene. One-electron oxidation of 1 by [(4-BrC<sub>6sub>H<sub>4sub>)<sub>3sub>N][SbCl<sub>6sub>] gave 2, which when oxidized by PhIO afforded 3. X-ray and IR analysis of 1鈥?b>3 revealed a systematic increase of Re鈥?i>C(鈮) and decrease of C鈮?i>O bond lengths and increase in the corresponding C鈮 stretching frequency. All of these results are consistent with weakening in the Re鈥?i>C(鈮) bond from 1 to 3 upon increasing the oxidation state from +1 in 1 to +3 in 3, with 2 being in between. The heptacoordinate complex 3 exhibited temperature-dependent fluxional behavior, caused by the pseudorotation of the rhenium center. This phenomenon was observed by NMR and supported computationally by density functional theory (DFT) calculations.