Phenylalanine-a biogenic ligand with flexible η~6- and η~6:κ~1-coordination at ruthenium(ii) centres

摘要

The reaction of (S)-2,5-dihydrophenylalanine 1 with ruthenium(iii) chloride yields the μ-chloro-bridged dimeric η~6-phenylalanine ethyl ester complex 3, which can be converted into the monomeric analogue, η~6:κ~1-phenylalanine ethyl ester complex 12, under basic conditions. Studies were carried out to determine the stability and reactivity of complexes bearing η~6- and η~6: κ~1-chelating phenylalanine ligands under various conditions. Reaction of 3 with ethylenediamine derivatives N-p-tosylethylenediamine or 1,4-di-N-p-tosylethylenediamine results in the formation of monomeric η~6:κ~1-phenylalanine ethyl ester complexes 14 and 15, which could be saponified yielding complexes 16 and 17 without changing the inner coordination sphere of the metal centre. The structure of η~6:κ~1-phenylalanine complex 17 and an N-κ~1-phenylalanine complex 13 resulting from the reaction of 3 with an excess of pyridine were confirmed by X-ray crystallography.