Mechanistic insight into fragmentation reactions of titanapinacolate complexes

Jesudoss V. Kingston, Oleg V. Ozerov, Sean Parkin, Carolyn P. Brock, Folami T. Ladipo

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Reactions between terminal alkynes or aromatic ketones and titanapinacolate complexes (DMSC)-Ti(OCAr2CAr2O) (2, Ar = Ph, and 3, Ar = p- MeC6H4; DMSC = 1,2-alternate dimethylsilyl-bridged p-tert-butylcalix[4]arene dianion) occur via rupture of the C-C bond of the titanacycle. Thus, reactions of 2 and 3 with terminal alkynes produce 2-oxatitanacyclopent-4-ene or 2-oxatitanacycloheptadiene complexes along with free Ar2CO. These compounds have been characterized spectroscopically and by X-ray crystallography. Because metallapinacolate intermediates have been implicated in important C-C bond-forming reactions, such as pinacol coupling and McMurry chemistry, the mechanism of the fragmentation reactions was studied. Analysis of the kinetics of the reaction of (DMSC)Ti {OC(p-MeC6H4)2C (p-MeC6H4)2O} (3) with Bu1C≡CH revealed that the fragmentation reactions proceed via a preequilibrium mechanism, involving reversible dissociation of titanapinacolate complexes into (DMSC)Ti(η2-OCAr2) species with release of a ketone molecule, followed by rate-limiting reaction of (DMSC)Ti (η2-OCAr2) species with an alkyne or ketone molecule.

Original languageEnglish
Pages (from-to)12217-12224
Number of pages8
JournalJournal of the American Chemical Society
Volume124
Issue number41
DOIs
StatePublished - Oct 16 2002

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (all)
  • Biochemistry
  • Colloid and Surface Chemistry

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