Synthesis, characterization, and alkyne cyclotrimerization chemistry of titanium complexes supported by calixarene-derived bis(aryloxide) ligation

Folami T. Ladipo, Vallipuram Sarveswaran, Jesudoss V. Kingston, Rebecca A. Huyck, S. Y.Sergei Y. Bylikin, Shana D. Carr, Randy Watts, Sean Parkin

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


Proximally bridged calix[4]arene compounds (DESC)H2 (3), (DMSHC)H2 (4), (DMSMC)H2 (5), and (DPSC)H2 (6), in which one R2Si group (R=alkyl or aryl) bridges adjacent oxygens, were synthesized via reaction between dialkyl- or diaryldichlorosilane and the corresponding calix[4]arene. Treatment of p- tert -butylcalix[4]arene with Ph2SiCl2 at room temperature or (o-MeC6 H4)2SiCl2 at 80 °C gave (ClPh2SiCl)2Calix-H2 (7) and (o-Tol2SiCl)2Calix-H2 (8), respectively. Titanium dichloride complexes 9-12 (L2 TiCl2, where L2=DESC, DMSHC, DMSMC, or DPSC) were prepared in high yield from reaction of 3-6 with TiCl4. The molecular structures of 7 and 12 were established by single-crystal X-ray diffraction studies. Reduction of 9, 11, and 12 with activated magnesium (Mg*) in the presence of an excess of Me3SiC≡CH produced titananorbornadiene complexes L2Ti{η6-1,2,4-C6H3 (SiMe3)3} (13-15, L2=DESC, DMSMC, or DPSC), which were characterized in solution. Catalytic cyclotrimerization of both terminal and internal alkynes was achieved using catalyst systems derived from L2TiCl2 complexes 9-12 and Mg*. For unsymmetrically substituted internal alkynes, preference for 1,2,4-substitution decreased as the size difference of the substituent groups decreased. The cyclotrimerization of PhC≡CMe was more facile when the calixarene-derived bis(aryloxide) ligand was DPSC versus DMSMC, suggesting that the DPSC ligand may provide a less crowded titanium center and exert greater kinetic control over the course of the cyclotrimerization.

Original languageEnglish
Pages (from-to)502-514
Number of pages13
JournalJournal of Organometallic Chemistry
Issue number3
StatePublished - Feb 9 2004

Bibliographical note

Funding Information:
Thanks are expressed to the US National Science Foundation (Grant No. CHE-9984776) for financial support of this work. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (Grant No. CHE-9974810). Thanks are expressed to Professor Carl Hertzel (Transylvania University) for recruitment of R.A. Huyck, and to Mr. Marc Maynor for his help with mass spectral data.


  • Alkyne cyclotrimerization
  • Calixarene compounds
  • Reduced titanium
  • Titanium(IV)

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry


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