Oxygen binding to [Pd(L)(L')] (L= NHC, L' = NHC or PR3, NHC = N-heterocyclic carbene). synthesis and structure of a paramagnetic trans-[Pd(NHC)2(η(1)-O2)2] complex

Xiaochen Cai; Subhojit Majumdar; George C Fortman; Catherine S J Cazin; Alexandra M Z Slawin; Charles Lhermitte; Rajeev Prabhakar; Meaghan E Germain; Taryn Palluccio; Steven P Nolan; Elena V Rybak-Akimova; Manuel Temprado; Burjor Captain; Carl D Hoff

doi:10.1021/ja1103348

Oxygen binding to [Pd(L)(L')] (L= NHC, L' = NHC or PR3, NHC = N-heterocyclic carbene). synthesis and structure of a paramagnetic trans-[Pd(NHC)2(η(1)-O2)2] complex

J Am Chem Soc. 2011 Feb 9;133(5):1290-3. doi: 10.1021/ja1103348. Epub 2011 Jan 4.

Authors

Xiaochen Cai¹, Subhojit Majumdar, George C Fortman, Catherine S J Cazin, Alexandra M Z Slawin, Charles Lhermitte, Rajeev Prabhakar, Meaghan E Germain, Taryn Palluccio, Steven P Nolan, Elena V Rybak-Akimova, Manuel Temprado, Burjor Captain, Carl D Hoff

Affiliation

¹ Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States.

PMID: 21204538
DOI: 10.1021/ja1103348

Abstract

The reactivity of a number of two-coordinate [Pd(L)(L')] (L = N-heterocyclic carbene (NHC) and L' = NHC or PR(3)) complexes with O(2) has been examined. Stopped-flow kinetic studies show that O(2) binding to [Pd(IPr)(P(p-tolyl)(3))] to form cis-[Pd(IPr)(P(p-tolyl)(3))(η(2)-O(2))] occurs in a rapid, second-order process. The enthalpy of O(2) binding to the Pd(0) center has been determined by solution calorimetry to be -26.2(1.9) kcal/mol. Extension of this work to the bis-NHC complex [Pd(IPr)(2)], however, did not lead to the formation of the expected diamagnetic complex cis-[Pd(IPr)(2)(η(2)-O(2))] but to paramagnetic trans-[(Pd(IPr)(2)(η(1)-O(2))(2)], which has been fully characterized. Computational studies addressing the energetics of O(2) binding have been performed and provide insight into reactivity changes as steric pressure is increased.