Exploring the reaction mechanism of a cationic terminal iridium methylene complex with ethyl diazoacetate, a Lewis base and dihydrogen: a quantum chemistry study

Abstract

The mechanisms for the formation of a cationic methylene complex [(PONOP)Ir(CH 2 )] + (PONOP = 2,6-bis(ditert-butylphosphinito)pyridine) via a-hydride abstraction from a neutral methyl complex [(PONOP)Ir(CH 3 )] and its reactivity with ethyl diazoacetate, a Lewis base (PMe 3 ) and dihydrogen have been studied computationally with the aid of density functional theory (DFT). The calculation results show that the Z 2 -alkene complex can be formed via a direct C-C coupling reaction involving the methylene ligand and ethyl diazoacetate. A ylide compound is given for the reaction of this cationic methylene complex with PMe 3 . In addition, hydrogenolysis of the IrQCH 2 moiety of this cationic methylene complex results in a hydride iridium complex. Our calculations could provide new insights into the reactivity of methylene complexes. Computational methodsAll geometries of the reactants, intermediates, transition states, and products were fully optimized by the means of the DFT

Substituent Effects on Reactions of [RhCl(COD)]2 with Diazoalkanes

“…Nucleophilic attack of the carbene carbon by the terminal nitrogen of diazofluorene would give intermediate 8 , which then evolves to azine 5 and regenerates [RhCl­(COD)] 2 . Similar pathways have been proposed previously for metal-mediated coupling of diazoalkanes to give olefins , and azines …”

“…Cyclopentadienylidene complex 2DC evolves to olefin complex 5DC by nucleophilic attack on the carbene carbon by the C (N 2 ) carbon of diazocyclopentadiene via transition state TS 2–5DC . , The process is thermodynamically favored by 82.2 kcal/mol with a barrier of 14.0 kcal/mol ( TS 2–5DC ). For comparison, the reaction of Rh 2 (O 2 CH) 4 (CPh­(CO 2 Me) with (MeO 2 C)­CHN 2 to give the olefin (MeO 2 C)­CHCPh­(CO 2 Me) was reported to have a barrier of ca.…”

Phosphonium salts and P-ylides

“…307 A computational study by Xie and co-workers investigated the reactivity of a cationic methylene complex [(2,6-bis(di-tert-butylphosphinito)pyridine)Ir(CH 2 )] 1 with PMe 3 . 308 …”