Fluoridonitrosyl Complexes of Technetium(I) and Technetium(II). Synthesis, Characterization, Reactions, and DFT Calculations

A mixture of [Tc(NO)F-5](2-) and [Tc(NO)(NH3)(4)F](+) is formed during the reaction of pertechnetate with acetohydroxamic acid (Haha) in aqueous HF. The blue pentafluoridonitrosyltechnetate(II) has been isolated in crystalline form as potassium and rubidium salts, while the orange-red ammine complex crystallins as bifluoride or PF6- salts. Reactions of [Tc(NO)F-5](2-) salts with HCI give the corresponding [Tc(NO)Cl-4/5](-/2-)complexes, while reflux in neat pyridine (py) results in the formation of the technetium(I) cation [Tc(NO)(py)(4)F](+), which can be crystallized as hexafluoridophosphate. The same compound can be synthesized directly from perteclmetate, Haha, HF, and py or by a ligand-exchange procedure starting from [Tc(NO)(NH3)(4)F](HF2). The technetium(I) cation [Tc(NO)(NH3)(4)F](+) can be oxidized electrochemically or by the reaction with Ce(SO4)(2) to give the corresponding Tc(II) compound [Tc(NO)(NH3)(4)F](2+). The fluorido ligand in [Tc(NO)(NH3)(4)F](+) can be replaced by CF3COO-, leaving the [Tc(NO)-(NH3)(4)](2+) core untouched. The experimental results are confirmed by density functional theory calculations on [Tc(NO)F-5](2-), [Tc(NO)(py)(4)F](+); [Tc(NO)(NH3)(4)F](+), and [Tc(NO)(NH3)(4)F](2+).