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Multielectron Redox Chemistry of Transition Metal Complexes Supported by a Non‐Innocent N 3 P 2 Ligand: Synthesis, Characterization, and Catalytic Properties
Author(s) -
Wang Denan,
Ekanayake Danushka M.,
Lindeman Sergey V.,
Verani Cláudio N.,
Fiedler Adam T.
Publication year - 2018
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201800843
Subject(s) - chemistry , redox , ligand (biochemistry) , catalysis , transition metal , chelation , imine , metal , amine gas treating , coordination complex , medicinal chemistry , non innocent ligand , benzaldehyde , crystallography , inorganic chemistry , stereochemistry , organic chemistry , biochemistry , receptor
A new redox‐active, diarylamido‐based ligand ( L N3P2 ) capable of κ 5 ‐ N , N , N,P,P chelation has been used to prepare a series of complexes with the general formula [M II ( L N3P2 )]X, where M = Fe ( 1 ; X = OTf), Co ( 2 ; X = ClO 4 ), or Ni ( 3 ; X = ClO 4 ). The diarylamido core of monoanionic L N3P2 is derived from bis(2‐amino‐4‐methylphenyl)amine, which undergoes condensation with two equivalents of 2‐(diphenylphosphanyl)benzaldehyde to provide chelating arms with both arylphosphine and imine donors. X‐ray structural, magnetic, and spectroscopic studies indicate that the N 3 P 2 coordination environment generally promotes low‐spin configurations. Three quasi‐reversible redox couples between +1.0 and –1.5 V (vs. Fc + /Fc) were observed in voltammetric studies of each complex, corresponding to M II /M III oxidation, L N3P2 ‐based oxidation, and M II /M I reduction (in order of highest to lowest potential). Spectroscopic and computational analyses of 3 ox – generated via chemical one‐electron oxidation of 3 – revealed that a stable diarylaminyl radical ( L N3P2· ) is formed upon oxidation. The ability of the Co II complex ( 2 ) to function as an electrocatalyst for H 2 generation was evaluated in the presence of weak acids. Moderate activity was observed using 4‐ tert ‐butylphenol as the proton source at potentials below –2.0 V. The insights gained here will assist in the future design of pentadentate mixed N/P‐based chelates for catalytic processes.