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.
- Metal ligand bond
- N-heterocyclic carbene
- Organometallic thermochemistry
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Atomic and Molecular Physics, and Optics
- Materials Science(all)