Side-on dinitrogen complexes of titanocenes with disubstituted cyclopentadienyl ligands: Synthesis, structure, and spectroscopic characterization

Scott P. Semproni, Carsten Milsmann, Paul J. Chirik

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24 Scopus citations

Abstract

Reduction of the 1,3-disubstituted titanocene complexes, (η 5-C 5H 3-1,3- iPr 2) 2TiI or rac, meso-(η 5-C 5H 3-1- iPr-3-Me) 2TiI, with excess 0.5% sodium amalgam under an N 2 atmosphere furnished the corresponding titanocene dinitrogen compounds, [(η 5-C 5H 3-1,3- iPr 2) 2Ti] 22, η 22-N 2) and [(η 5- C 5H 3-1- iPr-3-Me)Ti] 2222-N 2). Crystallographic studies on both molecules revealed side-on bound, [N 2] 2- ligands with N-N distances of 1.226(5) and 1.216(5) Å, respectively. Variable temperature magnetic susceptibility studies established population of a triplet ground state at ambient temperature that is slightly higher in energy than the singlet. Reducing the size of the 1,3-cyclopentadienyl substituents to methyl groups, [(η 5-C 5H 3-1,3-Me 2) 2Ti], resulted in crystallization of a trimetallic titanium dinitrogen complex with an activated μ 3211-N 2 ligand with an N-N distance of 1.320(3) Å. Hydrogenation of the isomeric titanocene dimethyl complex, (η 5-C 5H 3-1,2-Me 2) 2TiMe 2, in the presence of dinitrogen did not result in N 2 coordination but rather furnished the bimetallic titanium compound, (η 5-C 5H 3-1,2-Me 2) 2Ti(μ 2-H) Ti(η 5-C 5H 3-1,2-Me 2) (η 51-C 5H 2-1,2-Me 2), resulting from C-H activation of a cyclopentadienyl ring position. Addition of PhC≡CPh furnished (η 5-C 5H 3-1,2-Me 2) 2Ti(η 2- PhCCPh), demonstrating that the C-H bond activation event was reversible. By contrast, a bridging formyl complex was obtained following addition of five equivalents of CO, highlighting the availability of hydride insertion chemistry.

Original languageEnglish (US)
Pages (from-to)3672-3682
Number of pages11
JournalOrganometallics
Volume31
Issue number9
DOIs
StatePublished - May 14 2012

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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