Transition-metal mediated formation and cleavage of carbon-hydrogen bonds: hydrogenolysis of trinuclear alkylidyne clusters and oxidative addition of carbon-hydrogen bonds to rhenium
Treatment of dicobalt alkyne complexes Co/sub 2/(CO)/sub 6/(HCCR) (R = alkyl, aryl) with H/sub 2/ and Co/sub 2/(CO)/sub 8/ or CpMo(CO)/sub 3/H leads to ..mu../sub 3/-alkylidyne complexes with molecular formula Co/sub 3/(CO)/sub 9/CCH/sub 2/R and CpMo(CO)/sub 2/Co/sub 2/(CO)/sub 6/CCH/sub 2/R, respectively, in high yield and purity. Hydrogenation of these clusters occurs under mild conditions (60 to 90 /sup 0/C, benzene solution, 3 to 4 atm of H/sub 2/) and gives olefins, paraffins, and carbonyl compounds. A radical pathway for the hydrogenolyses is suggested. ESR experiments involving the reaction of Co/sub 3/(CO)/sub 9/CCH/sub 2/(CH/sub 3/)/sub 3/ (2) with H/sub 2/ in the presence of the spin-trap t-BuNO confirm the intervention of vinyl radical intermediates and reveal that a hydrogen atom donor is generated. Evidence consistent with vinyl radical intermediates is also provided by isotope labelling. Inter- and intramolecular C-H oxidative addition reactions have been observed from two related organorhenium intermediates: Cp*Re(CO)(PMe/sub 3/) (11) and Cp*Re(PMe/sub 3/)/sub 2/c (12) (Cp* = eta/sup 5/-C/sub 5/(CH/sub 3/)/sub 5/). The cyclometallated compounds undergo reductive elimination; the coordinatively unsaturated species thus formed can be trapped to give intermolecular C-H activation products under mild thermal conditions. In contrast to its (carbonyl)phosphine analog 11, 12 is capable of insertion into the C-H bonds of methane as well as cyclopropane and benzene. 100 refs., 20 figs., 1 tab.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5565732
- Report Number(s):
- LBL-19444; ON: DE85012231
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
10 SYNTHETIC FUELS
ALKANES
CHEMICAL PREPARATION
ALKENES
CARBONYLS
COBALT COMPLEXES
ELECTRON SPIN RESONANCE
ORGANOMETALLIC COMPOUNDS
NUCLEAR MAGNETIC RESONANCE
ALKYNES
CATALYSIS
EXPERIMENTAL DATA
HYDROGENATION
ISOTOPIC EXCHANGE
LABELLING
REACTION INTERMEDIATES
RHENIUM COMPLEXES
VINYL RADICALS
ALKYL RADICALS
CHEMICAL REACTIONS
COMPLEXES
DATA
HYDROCARBONS
INFORMATION
MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC COMPOUNDS
RADICALS
RESONANCE
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)
090121 - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989)