Role of axial base coordination in isonitrile binding and chalcogen atom transfer to vanadium(III) complexes

Subhojit Majumdar, Julia M. Stauber, Taryn D. Palluccio, Xiaochen Cai, Alexandra Velian, Elena V. Rybak-Akimova, Manuel Temprado, Burjor Captain, Christopher C. Cummins, Carl D. Hoff

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Abstract

The enthalpy of oxygen atom transfer (OAT) to V[(Me3SiNCH2CH2)3N], 1, forming OV[(Me3SiNCH2CH2)3N], 1-O, and the enthalpies of sulfur atom transfer (SAT) to 1 and V(N[t-Bu]Ar)3, 2 (Ar = 3,5-C6H3Me2), forming the corresponding sulfides SV[(Me3SiNCH2CH2)3N], 1-S, and SV(N[t-Bu]Ar)3, 2-S, have been measured by solution calorimetry in toluene solution using dbabhNO (dbabhNO = 7-nitroso-2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5- diene) and Ph3SbS as chalcogen atom transfer reagents. The V-O BDE in 1-O is 6.3 ± 3.2 kcal·mol-1 lower than the previously reported value for 2-O and the V-S BDE in 1-S is 3.3 ± 3.1 kcal·mol-1 lower than that in 2-S. These differences are attributed primarily to a weakening of the V-Naxial bond present in complexes of 1 upon oxidation. The rate of reaction of 1 with dbabhNO has been studied by low temperature stopped-flow kinetics. Rate constants for OAT are over 20 times greater than those reported for 2. Adamantyl isonitrile (AdNC) binds rapidly and quantitatively to both 1 and 2 forming high spin adducts of V(III). The enthalpies of ligand addition to 1 and 2 in toluene solution are -19.9 ± 0.6 and -17.1 ± 0.7 kcal·mol-1, respectively. The more exothermic ligand addition to 1 as compared to 2 is opposite to what was observed for OAT and SAT. This is attributed to less weakening of the V-Naxial bond in ligand binding as opposed to chalcogen atom transfer and is in keeping with structural data and computations. The structures of 1, 1-O, 1-S, 1-CNAd, and 2-CNAd have been determined by X-ray crystallography and are reported. (Graph Presented)

Original languageEnglish (US)
Pages (from-to)11185-11196
Number of pages12
JournalInorganic Chemistry
Volume53
Issue number20
DOIs
StatePublished - Oct 20 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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    Majumdar, S., Stauber, J. M., Palluccio, T. D., Cai, X., Velian, A., Rybak-Akimova, E. V., Temprado, M., Captain, B., Cummins, C. C., & Hoff, C. D. (2014). Role of axial base coordination in isonitrile binding and chalcogen atom transfer to vanadium(III) complexes. Inorganic Chemistry, 53(20), 11185-11196. https://doi.org/10.1021/ic5017005