ic5b00294_si_001.pdf (1.61 MB)
Steric Effect on the Nucleophilic Reactivity of Nickel(III) Peroxo Complexes
journal contribution
posted on 2015-07-06, 00:00 authored by Jalee Kim, Bongki Shin, Hyunjeong Kim, Junhyung Lee, Joongoo Kang, Sachiko Yanagisawa, Takashi Ogura, Hideki Masuda, Tomohiro Ozawa, Jaeheung ChoA set
of nickel(III) peroxo complexes bearing tetraazamacrocyclic ligands,
[NiIII(TBDAP)(O2)]+ (TBDAP = N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) and [NiIII(CHDAP)(O2)]+ (CHDAP = N,N′-dicyclohexyl-2,11-diaza[3.3](2,6)pyridinophane), were prepared
by reacting [NiII(TBDAP)(NO3)(H2O)]+ and [NiII(CHDAP)(NO3)]+,
respectively, with H2O2 in the presence of triethylamine.
The mononuclear nickel(III) peroxo complexes were fully characterized
by various physicochemical methods, such as UV–vis, electrospray
ionization mass spectrometry, resonance Raman, electron paramagnetic
resonance, and X-ray analysis. The spectroscopic and structural characterization
clearly shows that the NiO2 cores are almost identical
where the peroxo ligand is bound in a side-on fashion. However, the
different steric properties of the supporting ligands were confirmed
by X-ray crystallography, where the CHDAP ligand gives enough space
around the Ni core compared to the TBDAP ligand. The nickel(III) peroxo
complexes showed reactivity in the oxidation of aldehydes. In the
aldehyde deformylation reaction, the nucleophilic reactivity of the
nickel(III) peroxo complexes was highly dependent on the steric properties
of the macrocyclic ligands, with a reactivity order of [NiIII(TBDAP)(O2)]+ < [NiIII(CHDAP)(O2)]+. This result provides fundamental insight into
the mechanism of the structure (steric)–reactivity relationship
of metal peroxo intermediates.