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Radical Chemistry of Iminepyridine Ligands
Author(s) -
Budzelaar Peter H. M.
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201100698
Subject(s) - chemistry , alkyl , steric effects , unpaired electron , dissociation (chemistry) , imine , pyridine , reactivity (psychology) , alkylation , ligand (biochemistry) , electron transfer , medicinal chemistry , regioselectivity , bond dissociation energy , metal , photochemistry , stereochemistry , radical , organic chemistry , catalysis , medicine , biochemistry , alternative medicine , receptor , pathology
The reactivity of metal fragments MeLi(THF), Me 2 Mg, Me 2 Zn and Me 3 Al with a variety of imine/pyridine ligands was studied by DFT methods. Ligands having at least two such groups in conjugation very effectively accept an electron from a metal–carbon bonding orbital and thus assist alkyl dissociation: the M–Me dissociation free energy Δ G d decreases by about 45 kcal/mol for the Li, Mg and Zn fragments, and by 60–70 kcal/mol for Me 3 Al. Paths for transfer of an alkyl group to the ligands were also explored. Paths for transfer to ligand carbon atoms were found to have high barriers, and such transfers are instead proposed to proceed via initial M–Me dissociation. Direct alkyl transfer to ligand nitrogen atoms is somewhat easier, and for the most electropositive metal Li such a transfer might compete with radical chemistry. For Dimpy, the most stable products are the C3 and C4 alkylation ones. However, the observed regioselectivity of alkyl transfer (often to N py or C2) does not correlate with product stability and is likely to be a complicated function of radical stability, steric factors and unpaired electron density distribution. The results illustrate that Dimpy and related ligands should be considered strong, reversible oxidants.