1. N-heterocyclic carbene complexes of palladium in oxygen atom transfer reactions involving the making and breaking of N-O bonds
- Author
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Burjor Captain, Subhojit Majumdar, Leonardo F. Serafim, Catherine S. J. Cazin, Carl D. Hoff, Manuel Temprado, Xiaochen Cai, and Steven P. Nolan
- Subjects
NITRILE OXIDES ,Stereochemistry ,DATIVE LIGANDS ,chemistry.chemical_element ,Crystal structure ,010402 general chemistry ,OXIDATION ,01 natural sciences ,Medicinal chemistry ,Inorganic Chemistry ,chemistry.chemical_compound ,Materials Chemistry ,Physical and Theoretical Chemistry ,ORGANONITRILES ,Phosphine oxide ,010405 organic chemistry ,Ligand ,CORRELATION-ENERGY ,Cycloaddition ,ELECTRONIC-STRUCTURES ,0104 chemical sciences ,Chemistry ,chemistry ,Yield (chemistry) ,DENSITY ,NITRONES ,Carbene ,Phosphine ,Palladium ,TRAPPING REACTIONS ,CYCLOADDITION - Abstract
Reaction of three equivalents of MesCNO (Mes = 2,4,6-trimethylphenyl) with one equivalent of [Pd(IPr)(P(p-tolyl)3)] in toluene yields the solid complex [Pd(IPr)(NCMes)(κ2-O–N C-Mes(–N–C( O)Mes))]. Three major steps are proposed to be involved in the reaction based on spectroscopic studies as well as literature precedents for related cycloadditions: i. oxidation of the coordinated phosphine ligand to phosphine oxide ii. oxygen atom transfer forming a C O bond from the N–O bond of MesCNO, and iii. cycloaddition of a final MesCNO ligand to yield product. Addition of two equivalents of NO at low temperature to the in situ generated peroxide complex [Pd(IPr)2(η2-O2)] generates the N-bonded complex trans-[Pd(IPr)2(NO2)2] in keeping with a literature precedent reported for similar complexes. Insight into the energetics of this reaction are probed by DFT calculations using the truncated ligand complex [Pd(IMe)2]. The computed enthalpy of binding of two moles of NO2 to form [Pd(IMe)2(NO2)2] is −112 kcal/mol indicating that its preparation from [Pd(IMe)2], N2 and 2O2 is thermodynamically favorable by −96 kcal/mol. Crystal structures of [Pd(IPr)(NCMes)(κ2-O–N C-Mes(–N–C( O)Mes))] and trans-[Pd(IPr)2(NO2)2] are reported.
- Published
- 2017