D. Parker
Dec 7, 1982
Citations
0
Influential Citations
5
Citations
Journal
Journal of Organometallic Chemistry
Abstract
Abstract A range of monosubstituted olefin rhodium acetylacetonate complexes has been prepared and their solution equilibria and dynamics studied by carbon-13 nuclear magnetic resonance between 188 and 320 K. Vinylcyclohexane forms two diastereomeric bis-olefin complexes which do not interconvert, whereas distyrenerhodium acetylacetonate possesses one major rotamer which interconverts rapidly with its isomers at room temperature. para-Methoxy- and para-nitrostyrene analogues show similar behaviour, and the complexes of these substituted styrenes with rhodium hexafluoroacetylacetonate show enhanced rates of associative olefin exchange. Bis-olefin complexes of orthomethoxystyrene are static in solution with coordination of one of the aryl ether oxygens inhibiting fluxional behaviour. Methyl propenoate forms a bis-olefin complex exhibiting a complex, dynamic 13C NMR spectrum, demonstrating the presence of all possible rotamers of both diastereomers at low temperatures. Vinyl acetate displaces one or two moles of ethylene from diethylenerhodium(I) acetylacetonate. The mixed olefin complex shows rapid independent rotation of its ethylene ligand, whilst bis(vinyl acetate)rhodium(I) acetylacetonate reveals two dynamic processes with different activation energies. The mechanisms of these interconversions are discussed.