kinetics, steric course, and mechanism of stereoisomerization of aluminum β-diketonates

Miles Pickering, Berardo Jurado, Charles Jr Springer

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The activation parameters for the stereoisomerizations of tris(2,6-dimethyl-3,5-heptanedionato)aluminum(III) and bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(2,6-dimethyl-3,5-heptanedionato) aluminum(III) have been determined by dynamic nuclear magnetic resonance (DNMR) spectroscopy and are reported. The reactions are found to be first order and intramolecular. Permutational analysis of the combined results of this study and those of all other DNMR studies of tris(β-diketonato)aluminum chelates reported reveal that the steric course of stereoisomerization involves the effective simultaneous interchange of the terminal groups with n two of the three bidentate ligands and enantiomerization at the metal center. Consideration of the magnitudes of the activation parameters, the effective steric course, and a topological analysis leads to the following mechanistic conclusions. Chelates with alkyl or aryl substituents on the β-diketonate rings most likely stereoisomerize by a rhombic twist mechanism. Chelates with fluorocarbon substituents on the β-diketonate rings stereoisomerize by a bondrupture mechanism which proceeds via an actual square pyramidal-apical five-coordinate intermediate.

Original languageEnglish (US)
Pages (from-to)4503-4515
Number of pages13
JournalJournal of the American Chemical Society
Volume98
Issue number15
StatePublished - 1976
Externally publishedYes

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Aluminum
Kinetics
Magnetic Resonance Spectroscopy
Chemical activation
Fluorocarbons
Interchanges
Nuclear magnetic resonance spectroscopy
Metals
Ligands
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

kinetics, steric course, and mechanism of stereoisomerization of aluminum β-diketonates. / Pickering, Miles; Jurado, Berardo; Springer, Charles Jr.

In: Journal of the American Chemical Society, Vol. 98, No. 15, 1976, p. 4503-4515.

Research output: Contribution to journalArticle

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