Assignment and conformational investigation of asymmetric phenylindenylidene ruthenium complexes bearing N,O-bidentate ligands.
The NMR conformational study of three asymmetric phenylindenylidene ruthenium complexes 4.1-4.3, is presented. Complete (1)H and (13)C assignments could be obtained for 4.1-4.3 in benzene solution from multiple 2D homonuclear and heteronuclear NMR techniques. Our NMR analysis shows that each complex exists as a 55:45 mixture of two rotational isomers in slow exchange on the NMR chemical shift timescale. They are shown to be related by a 180 degrees flip of the indenylidene ligand along the Ru=CR bond. Both rotational isomers can be discriminated by means of NOEs contacts between the various ligands coordinating to the Ru. By matching these stereospecific assignments to the chemical shift, a chemical shift based fingerprint of the isomers that may allow straightforward assignment of future asymmetric phenylindenylidene ruthenium complexes is proposed.
Hendrickx
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PM
Department of Organic Chemistry, Ghent University, Krijgslaan 281 (S4), B-9000 Ghent, Belgium. Pieter.Hendrickx@UGent.Be
Drozdzak
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Verpoort
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Martins
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JC