Synthesis of C2 -Symmetric Dimeric Re(I) Peptide Complexes.

The reactions of [Re(CO)3(H2O)3]Br or Re(CO)5Cl with two peptides, glycylglycine or glycylalanine, were investigated. Each reaction produced a unique, well-defined product. Structural elucidation showed the formation of chiral compounds with the formula [Re(CO)3(Gly-Xxx-O)]2, Xxx = Gly 1, Ala 2. Each dimer displays C2 -symmetry and a nearly rectangular shape. The ligands are bound via the amine and amide carbonyl at a rhenium center and via the pendant carboxylate to the adjacent rhenium center. Both products are fully characterized, via X-ray structure elucidation.