Rhenium(I) compounds bound by tripodal ligands of pyridine and N-methylimidazole

The reaction of Re(CO)(5)Br with tris(2-pyridyl)methanol (tpmOH) leads to unexpectedly complex chemistry with three new compounds forming instead of a single product. In compound 1, the tpmOH ligand binds to the metal in the N,N',N'-mode; 2 has tpmO(-) bound in the N,N',O-mode; while 3 is a dimer with the tpmO(-) ligand utilizing each of the four donor atoms to bridge the two metal centers. The analogous methyl ether ligands, tris(2-pyridyl)methoxymethane (tpmOMe) or tris2-(l-methylimidazolyl)]methoxymethane (timmOMe), each yielded a single product, 4 and 5, respectively, bound in the N,N',N'-mode, and are new leads for potential radiotherapeutic agents. All compounds have been structurally characterized.