Chemistry of metal oxo alkyl complexes. Mechanistic studies on the anaerobic and aerobic decompositions of molybdenum(VI) dioxo dialkyl complexes

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00047a056· OSTI ID:6110121

Vetter, W M; Sen, A ^[1]

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1. Pennsylvania State Univ., University Park (United States)

The anaerobic and aerobic decompositions of L{sub 2}Mo(O){sub 2}R{sub 2} (L{sub 2} = 4,4{prime}-dimethyl-2,2{prime}-dipyridyl, R = CH{sub 2}Ph, 1; R = CH{sub 2}C{sub 6}H{sub 4}CH{sub 3}-p, 2; R = (CH{sub 2}){sub 4}CH:CH{sub 2}, 3; R = CH{sub 2}CHMe{sub 2}, 4; R = CH{sub 2}CMe{sub 3}, 5; R = CH{sub 2}CMe{sub 2}Ph, 6) were studied. The anaerobic decomposition mode chosen by a given L{sub 2}Mo(O){sub 2}R{sub 2} complex is a sensitive function of the hydrocarbyl group, R. If accessible {beta}-hydrogens are present on R (as in 3 and 4), equal amounts of alkane and alkene are formed through a {beta}-hydrogen abstraction pathway. In the case of 4, an additional pathway involving Mo-R bond homolysis accounts for 10% of the products formed. When {beta}-hydrogens are absent from R (as in 1, 2, and 6), the free radical, R{sup {sm bullet}}, formed by Mo-R bond homolysis is the predominant product. The reaction of the L{sub 2}Mo(O){sub 2}R{sub 2} complexes with O{sub 2} appears to proceed almost exclusively through the intermediacy of the free radical, R{sup {sm bullet}}. In inert solvents, the principal organic product is the corresponding aldehyde, and the role of O{sub 2} in its formation from L{sub 2}Mo(O){sub 2}R{sub 2} is 2-fold: (a) O{sub 2} promotes the homolysis of the Mo-R bond to form R{sup {sm bullet}}, and (b) O{sub 2} traps the resultant radical to yield the aldehyde. Labeling studies indicated that O{sub 2}, rather than the Mo{double bond}O group, was the predominant source of oxygen for the aldehydes. Mechanistic implications of the authors' observations for the heterogeneous oxidation of alkanes and alkenes by Mo(VI)- and V(V)-oxo species are discussed.

• DOE Contract Number: FG02-84ER13295
• OSTI ID: 6110121
• Journal Information: Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 10:1; ISSN 0276-7333; ISSN ORGND
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AEROBIC CONDITIONS
ALKALINE EARTH METAL COMPOUNDS
ALKANES
ANAEROBIC CONDITIONS
ARYL RADICALS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DECOMPOSITION
DEUTERIUM
ELEMENTS
EVEN-EVEN NUCLEI
GRIGNARD REAGENTS
HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LABELLING
LIGANDS
LIGHT NUCLEI
MAGNESIUM COMPOUNDS
MOLYBDENUM COMPLEXES
NMR SPECTRA
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXIDATION
OXYGEN
OXYGEN 18
OXYGEN ISOTOPES
RADICALS
REACTION KINETICS
SPECTRA
STABLE ISOTOPES
TOLYL RADICALS
TRANSITION ELEMENT COMPLEXES