Figure 11.

Presumed structure of the cationic technetium and rhenium [M(CO)₃] ⁺ aqua complex (A), and possible structures of [M(CO)₃]⁺ complexes with phosphate, that could give rise to additional ³¹P NMR resonances and negatively charged complexes. As well as mononuclear species such as (B-E), dinuclear species such as (F) and higher nuclearity species may be expected to exist in bulk solutions used for NMR, while at trace concentrations of Tc and Re present in the radioactive solutions, only mononuclear species would be expected to contribute significantly to the speciation. Also shown, (G) is a putative “salt bridge” interaction between an arginine side chain and coordinated phosphate.