Nickel catalysis of olefin epoxidation
The catalytic epoxidation of olefins is examined with a wide variety of nickel(II) complexes derived from different tetraaza macrocycles (both neutral and anionic), Schiff bases, porphyrins, and bidentate phosphines. The most effective among these are the dicationic Ni/sup II/(cyclam)/sup 2 +/ and its unsaturated analogues Ni/sup II/(Me/sub 4/(14)tetraeneN/sub 4/)/sup 2 +/ and Ni/sup II/ (CR)/sup 2 +/ as well as the Schiff base derivatives Ni/sup II/(Tfaced) and Ni/sup II/(Aceted). All of the nickel(II) complexes efficiently convert iodosylbenzene as the terminal oxidant to iodobenzene. However, despite extensive efforts to optimize the solvent, counterions, added donor ligands, and terminal oxidants, the conversions of olefins are restricted to modest yields of epoxides owing to competition from the oxidative attack on the solvent and the ligands. The catalytic activity is tentatively ascribed to an active oxo-nickel(IV) intermediate that is rather indiscriminate in oxygen atom transfer and in homolytic attack on solvent as well as ligand. A spectral transient is assigned to a (..mu..-oxo)nickel(III) dimer arising from the facile association of the putative oxo-nickel(IV) intermediate with the nickel(II) precursor. In these regards, the nickel(II) precursor. In these regards, the nickel catalysis of olefin epoxidation is strongly reminiscent of the behavior of cationic manganese(III) complexes under similar conditions. 48 references, 1 figure, 6 tables.
- Research Organization:
- Univ. of Houston, University Park, TX
- OSTI ID:
- 6630434
- Journal Information:
- Inorg. Chem.; (United States), Vol. 26:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKENES
CHEMICAL REACTIONS
NICKEL COMPLEXES
CATALYTIC EFFECTS
EPOXIDES
EXPERIMENTAL DATA
COMPLEXES
DATA
HYDROCARBONS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
TRANSITION ELEMENT COMPLEXES
090110* - Hydrocarbon Fuels- Properties- (1979-1989)
400201 - Chemical & Physicochemical Properties