Enthalpies of ligand substitution for [Mo(η5C 5H5)(CO)2(NO)] - The role of π-bonding effects in metal-ligand bond strengths

Subhojit Majumdar, Burjor Captain, Catherine S.J. Cazin, Steven P. Nolan, Carl D. Hoff

Research output: Contribution to journalArticlepeer-review


Enthalpies of ligand substitution for [Mo(η5-C 5H5)(CO)2(NO)] producing [Mo(η5- C5H5)Mo(CO)(L)(NO)] have been measured by solution calorimetry at 30 °C in THF for L = P(OMe)3 < PMePh 2 < SIPr < PMe2Ph < IPr < PMe < PnBu 3 (SIPr = 1,3-bis(2,6-bis(diisopropylphenyl)imidazolinylidene; IPr = 1,3-bis(2,6-bis(diisopropylphenyl)-imidazol-2-ylidene)). The accepting metal fragment [Mo(η5-C5H5)(CO)(NO)] has a vacant site containing strongly π-accepting carbonyl and nitrosyl ligands and this is shown to influence the stability of the product complex. Infrared studies of both νCO and νNO show that metal-to-ligand backbonding increases in the order P(OMe)3 < PMe3 < SIPr < IPr implying that both steric and electronic factors play a role in determining complex stability. The crystal structures of [Mo(η5- C5H5)(CO)(IPr)(NO)] and [Mo(η5-C 5H5)(CO)(SIPr)(NO)] are reported.

Original languageEnglish (US)
Pages (from-to)156-162
Number of pages7
JournalJournal of Chemical Thermodynamics
StatePublished - Jun 2014


  • Carbonyl
  • Metal ligand bond
  • Molybdenum
  • N-heterocyclic carbene
  • Nitrosyl
  • Organometallic thermochemistry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)


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