TECHNETIUM AND RHENIUM COMPLEXES OF MERCAPTO-CONTAINING PEPTIDES .1. TC(V) AND RE(V) COMPLEXES WITH MERCAPTOACETYL DIGLYCINE (MAG2) AND X-RAY STRUCTURE OF ASPH4[TCO(MAG2)].C2H5OH

The reaction of mercaptoacetyl diglycine (MAG2) with technetium(V) glu conate in aqueous solution produced [TcO(MAG2)]-. A single X-ray struc ture determination was carried out for the tetraphenylarsonium salt. T he dark brown crystals are monoclinic, space group P2(1)/n, with a=12. 478(5), b=14.922(5), c=17.183(9) angstrom and Z = 4. The [TcO(MAG2)]- ion has a square pyramidal geometry with the technetium atom displaced by 0.756 angstrom towards the oxo ligand from the plane formed by the equatorial S,N,N,O atoms. The rhenium complex AsPh4[ReO(MAG2)] was pr epared analogously starting from Re(V) gluconate and characterized.