Exclusive C-C activation in the rhodium(I) PCN pincer complex. A computational study

Citation
A. Sundermann et al., Exclusive C-C activation in the rhodium(I) PCN pincer complex. A computational study, ORGANOMETAL, 20(9), 2001, pp. 1783-1791
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
ORGANOMETALLICS
ISSN journal
0276-7333 → ACNP
Volume
20
Issue
9
Year of publication
2001
Pages
1783 - 1791
Database
ISI
SICI code
0276-7333(20010430)20:9<1783:ECAITR>2.0.ZU;2-T
Abstract
The mechanism of competitive intramolecular C-C and C-H bond activation in PCN pincer complexes of rhodium(I) has been studied computationally. Experi mentally this system exhibits exclusive cleavage of an aryl-methyl C-C bond ; no products corresponding to C-K bond cleavage in the methyl group have b een observed. The calculated relative energies indicate that the C-C activa tion product is the most stable one (DeltaE < -50 kJ<bullet>mol(-1) relativ e to the C-H activation product) and that its formation is irreversible. C- K activation is not kinetically forbidden, but it is fast and reversible. B ecause of the weak Rh-N bond several intermediates on the C-H activation pa ths are accessible; therefore low concentrations of these species are a pla usible reason for the experimental result. Further, this study reveals that the unique preference of C-C bond activation in the PCN system results fro m insufficient stabilization of the C-H activation product due to strain. T o model the complete ligand including all bulky substituents used in the ex periment, the ONIOM method has been employed, using the B3LYP/lanl2dz level for the inner layer and the HF/lanl1mb level to model substituent effects.