Technetium(I) Carbonyl β-Diketonate Complexes with Ligands of Different σ-Donor and π-Acceptor Power: A Comparative Analysis

Technetium-99 tetracarbonyl β-diketonates 99Tc(dik)(CO)4 (dik = 2,4-pentanedionate (acetylacetonate, acac), 1-phenyl-4,4,4-trifluoro-1,3-butanedionate (benzoyltrifluoroacetonate, btfa), and 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate (hexafluoroacetylacetonate, hfa)) were prepared by the reaction of 99TcBr(CO)5 in CCl4 with potassium salts of the corresponding β-diketones. 99Tc(dik)(CO)4 reacts with imidazole and pyridine to form the corresponding tricarbonyl species 99Tc(dik)(CO)3(Imd) and 99Tc(dik)(CO)3(Py). The reaction of 99Tc(dik)(CO)4 with triphenylphosphine initially yields the monophosphine complexes 99Tc(dik)(CO)3(PPh3), which readily transform into the bisphosphine dicarbonyl complexes 99Tc(dik)(CO)2(PPh3)2. The complexes obtained were characterized by IR and 1H, 19F, 31P, 99Tc NMR spectroscopy and, in most cases, by single crystal X-ray diffraction analysis. The composition-property relationships and the mutual influence of ligands in technetium carbonyl β-diketonate complexes are discussed.