Chemistry of Metal Oxo Alkyl Complexes. Mechanistic Studies on the Anaerobic and Aerobic Decompositions of Molybdenum(VI) Dioxo Dialkyl Complexes

William M. Vetter, Ayusman Sen

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The anaerobic and aerobic decompositions of L2Mo(0)2R2 [L2 = 4,4′-dimethyl-2,2′-dipyridyl, R = CH2Ph, 1; R = CH2C6H4CH3-p, 2; R = (CH2)4CH:CH2, 3; R = CH2CHMe2, 4; R = CH2CMe3) 5; R = CH2CMe2Ph, 6] were studied. The anaerobic decomposition mode chosen by a given L2Mo(O)2R2 complex is a sensitive function of the hydrocarbyl group, R. If accessible β-hydrogens are present on R (as in 3 and 4), equal amounts of alkane and alkene are formed through a β-hydrogen abstraction pathway. In the case of 4, an additional pathway involving Mo-R bond homolysis accounts for 10% of the products formed. When β-hydrogens are absent from R (as in 1, 2, and 6), the free radical, R*, formed by Mo-R bond homolysis is the predominant product. However, in every case there is an additional minor pathway for the formation of the alkane, RH, that involves α-hydrogen abstraction from the neighboring hydrocarbyl group. Because of the expected low stability of the primary neopentyl radical, the α-hydrogen abstraction pathway, rather than Mo-R bond homolysis, predominates in the decomposition of 5. The reaction of the L2Mo(O)2R2 complexes with O2 appears to proceed almost exclusively through the intermediacy of the free radical, R*. In inert solvents, the principal organic product is the corresponding aldehyde, and the role of O2 in its formation from L2Mo(O)2R2 is 2-fold: (a) O2 promotes the homolysis of the Mo-R bond to form R*, and (b) O2 traps the resultant radical to yield the aldehyde. Labeling studies indicated that O2, rather than the Mo=O group, was the predominant source of oxygen for the aldehydes. Mechanistic implications of our observations for the heterogeneous oxidation of alkanes and alkenes by Mo(VI)- and V(V)-oxo species are discussed.

Original languageEnglish (US)
Pages (from-to)244-250
Number of pages7
JournalOrganometallics
Volume10
Issue number1
DOIs
StatePublished - Jan 1 1991

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Fingerprint

Dive into the research topics of 'Chemistry of Metal Oxo Alkyl Complexes. Mechanistic Studies on the Anaerobic and Aerobic Decompositions of Molybdenum(VI) Dioxo Dialkyl Complexes'. Together they form a unique fingerprint.

Cite this