A new tricarbonyl fac-[M(acac)(isc)(CO)3] complex (M = Re, 99mTc) with acetylacetonate (acac) and isocyanide (isc) in a 2+1 combination

The synthesis and characterization of the neutral 2+1 mixed ligand complex fac-Re(CO)3(acac)(isc) (4) with acetylacetonate (acac) as the bidentate ligand and an isocyanide (the isocyanocyclohexane, isc) as the monodentate ligand is described. The synthesis of 4 proceeds through the intermediate formation of the fac-Re(acac)(H2O)(CO)3 precursor complex 2. Complex 4 was characterized by elemental analysis, spectroscopic methods, and X-ray crystallography showing a distorted octahedral arrangement of the ligands around Re. At technetium-99m level, the corresponding fac-99mTc(acac)(isc)(CO)3 complex 5 was obtained in high yield by reacting the fac-99mTc(acac)(H2O)(CO)3 precursor complex 3 with isocyanocyclohexane and its structure was established by chromatographic comparison with the prototypic rhenium complex using high performance liquid chromatography.