Iron Complexes Bearing Diphosphine Ligands with Positioned Pendant Amines as Electrocatalysts for the Oxidation of H2

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• 作者：Tianbiao Liu ; Qian Liao ; Molly O鈥橦agan ; Elliott B. Hulley ; Daniel L. DuBois ; R. Morris Bullock
• 刊名：Organometallics
• 出版年：2015
• 出版时间：June 22, 2015
• 年：2015
• 卷：34
• 期：12
• 页码：2747-2764
• 全文大小：936K
• ISSN：1520-6041

文摘

The synthesis and spectroscopic characterization of Cp^C₅F₄NFe(P^tBu₂N^Bn₂)Cl, [3-Cl] (where C₅F₄N is a tetrafluoropyridyl substituent and P^tBu₂N^Bn₂ = 1,5-dibenzyl-3,7-di(tert-butyl)-1,5-diaza-3,7-diphosphacyclooctane), are reported. Complex 3-Cl and [Cp^C₅F₄NFe(P^tBu₂N^tBu₂)Cl], 4-Cl, are precursors to intermediates in the catalytic oxidation of H₂, including Cp^C₅F₄NFe(P^tBu₂N^Bn₂)H (3-H), Cp^C₅F₄NFe(P^tBu₂N^tBu₂)H (4-H), [Cp^C₅F₄NFe(P^tBu₂N^Bn₂)]BAr^F₄ ([3](BAr^F₄), [Cp^C₅F₄NFe(P^tBu₂N^tBu₂)]BAr^F₄ ([4](BAr^F₄), [Cp^C₅F₄NFe(P^tBu₂N^Bn₂)(H₂)]BAr^F₄ ([3-H₂]BAr^F₄), and [Cp^C₅F₄NFe(P^tBu₂N^tBu₂H)H]BAr^F₄ ([4-FeH(NH)]BAr^F₄). All of these complexes were characterized by spectroscopic and electrochemical studies; 3-Cl, 3-H, and 4-Cl were also characterized by single crystal diffraction studies. 3-H and 4-H are electrocatalysts for H₂ (1.0 atm) oxidation in the presence of an excess of the amine bases N-methylpyrrolidine, Et₃N or ⁱPr₂EtN. Turnover frequencies at 22 掳C for 3-H and 4-H with N-methylpyrrolidine as the base are 2.5 and 0.5 s^鈥?, and overpotentials at E_cat/2 are 235 and 95 mV, respectively. Studies of individual chemical and electrochemical reactions of the various intermediates provide important insights into the factors governing the overall catalytic activity for H₂ oxidation.