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.