π-Ligands for Generating Transition Metal−Peptide Complexes:  Coordination of Amino Acid Derivatives to Tungsten Utilizing Alkyne Ligands

<UFIGR ID="ol026298an00001">Amino acid derivatives bearing an alkyne (AA-CCH) at either the N- or C-terminus readily react with W(CO)<INF>3</INF>(S<INF>2</INF>CNMe<INF>2</INF>)<INF>2</INF> to replace the carbon monoxides and form the novel bis-alkyne complexes W(AA-CCH)<INF>2</INF>(S<INF>2</INF>CNMe<INF>2</INF>)<INF>2</INF>; the solution behavior of these complexes shows that only the alkyne, and not the other functional groups on the amino acid, bonds to the tungsten.