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

Tianbiao Liu, Qian Liao, Molly O'Hagan, Elliott B. Hulley, Daniel L. DuBois, R. Morris Bullock

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The synthesis and spectroscopic characterization of CpC5F4NFe(PtBu2NBn2)Cl, [3-Cl] (where C5F4N is a tetrafluoropyridyl substituent and PtBu2NBn2 = 1,5-dibenzyl-3,7-di(tert-butyl)-1,5-diaza-3,7-diphosphacyclooctane), are reported. Complex 3-Cl and [CpC5F4NFe(PtBu2NtBu2)Cl], 4-Cl, are precursors to intermediates in the catalytic oxidation of H2, including CpC5F4NFe(PtBu2NBn2)H (3-H), CpC5F4NFe(PtBu2NtBu2)H (4-H), [CpC5F4NFe(PtBu2NBn2)]BArF4 ([3](BArF4), [CpC5F4NFe(PtBu2NtBu2)]BArF4 ([4](BArF4), [CpC5F4NFe(PtBu2NBn2)(H2)]BArF4 ([3-H2]BArF4), and [CpC5F4NFe(PtBu2NtBu2H)H]BArF4 ([4-FeH(NH)]BArF4). 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 °C for 3-H and 4-H with N-methylpyrrolidine as the base are 2.5 and 0.5 s-1, and overpotentials at Ecat/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. (Chemical Equation Presented).

Original languageEnglish
Pages (from-to)2747-2764
Number of pages18
JournalOrganometallics
Volume34
Issue number12
DOIs
Publication statusPublished - Jun 22 2015

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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