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A Bis(µ‐chlorido)‐Bridged Cobalt(II) Complex with Silyl‐Containing Schiff Base as a Catalyst Precursor in the Solvent‐Free Oxidation of Cyclohexane
Author(s) -
Zaltariov MirelaFernanda,
Vieru Veacheslav,
Zalibera Michal,
Cazacu Maria,
Martins Nuno M. R.,
Martins Luísa M. D. R. S.,
Rapta Peter,
Novitchi Ghenadie,
Shova Sergiu,
Pombeiro Armando J. L.,
Arion Vladimir B.
Publication year - 2017
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.201700875
Subject(s) - chemistry , cyclohexane , catalysis , cobalt , schiff base , aqueous solution , paramagnetism , ligand (biochemistry) , solvent , electrochemistry , inorganic chemistry , crystallography , catalytic oxidation , polymer chemistry , organic chemistry , biochemistry , physics , receptor , electrode , quantum mechanics
A new bis(µ‐chlorido)‐bridged cobalt(II) complex [Co 2 (µ‐Cl) 2 (HL 2 ) 4 ][CoCl 4 ] ( 1 ), where HL 2 is a silyl‐containing Schiff base, was synthesised. The structure of this compound was established by X‐ray crystallography revealing a zwitterionic form adopted by the organic ligand. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetisation indicate the presence of ferromagnetic interactions between paramagnetic d 7 cobalt(II) centres ( S Co = 3/2). The exchange coupling parameter J (Co1–Co2) = +7.0 cm –1 extracted from broken‐symmetry (BS) DFT calculations agrees well with the value of +8.8 cm –1 determined from the experimental data by fitting them with the HamiltonianH^= −JC o 1 − C o 2e x c hS^C o 1⋅S^C o 2. Electrochemical studies indicate that complex 1 is inefficient as a catalyst in electrochemical reduction of protons. One of the reasons is the low stability of the complex in solution. In contrast, 1 acts as an effective homogeneous (pre)catalyst in the microwave‐assisted neat oxidation of cyclohexane with aqueous t BuOOH (TBHP). The possible mechanism of catalytic oxidation and other advantages of using 1 in the oxidation of cycloalkanes are discussed.