Relevance of the ligand exchange rate and mechanism of fac-[[(CO)3M(H2O)3].sup.+] (M = Mn, Tc, Re) complexes for new radiopharmaceuticals

The multinuclear NMR was utilized to investigate the kinetics of water exchange and substitution on [[(CO)3M(H2O)3].sup.+] (M = Mn, Tc, Re) complexes. The substitution of water in fac-[[(CO)3M(H2O)3].sup.+] by dimethyl sulfide (DMS) is slightly faster than that by C[H.sub.3]CN, 3 times faster of Mn, 1.5 times faster for Tc and 1.2 times faster for Re.