Local Structure and Electronic State of Technetium in Pentacarbonyl Hydride TcH(CO) ₅

Technetium pentacarbonyl hydride 99 TcH(CO) 5 was studied using X-ray absorption spectroscopy at the Tc K-edge, complemented by a series of 99 TcX(CO) 5 (X = Cl, Br, I, 99 Tc(CO) 5 ) as the references. Experimental Tc K-edge XANES and EXAFS data were interpreted with the aid of density functional theory and advanced spectral modeling. EXAFS analysis of liquid pentacarbonyl hydride showed that the Tc–C and Tc–O interatomic distances in the molecule of this complex were close to those in 99 Tc 2 (CO) 10 . The Tc K-edge XANES fingerprint and the first-shell EXAFS responses are largely controlled by the carbonyl coordination, whereas the nature of the X ligands in a series of 99 TcX(CO) 5 (X = Cl, Br, I, 99 Tc(CO) 5 ) exerts only a secondary role. The combined experimental and computational results further elucidate the factors underlying the enhanced stability of 99 TcH(CO) 5 toward carbonyl substitution.