Characterisation via electrospray ionisation multistage mass spectrometry of three related series of nitrido technetium complexes containing phosphinothiolate and dithiocarbamate ligands

Abstract

Nine nitrido technetium compounds comprising bis-substituted Tc(N)(PS)(2) (1-4) (PS = bidentate phosphinothiolate ligands) and Tc(N)(dtc)(2) (5, 6) derivatives (dtc = bidentate dithiocarbamate), and mixed-ligand Tc(N)(PS)(dtc) (7-9) species, were subjected to electrospray ionisation mass spectrometry and MS(n) experiments. Bis-substituted phosphinothiolato complexes 1-4 lead to the straightforward formation of dinuclear species reasonably originating from proton bound dimers. These dinuclear species do not show, under collisionally induced fragmentation processes, the formation of monomeric units but cleavages related to the ligand framework, thereby proving the high stability of the [Tc--H(+)--Tc] bond. Bis-dithiocarbamate compounds 5 and 6 show, instead, abundant [M+H](+), [M+Na](+) and [2M+Na](+) ions, and their collisionally induced fragmentations are highly favoured with cleavages related to the C--N and C--S bonds. During these processes, the coordination of a water molecule to [MH-L](+) product ions is observed, as proved by the collisionally induced H(2)O loss detected for this species. Mixed-ligand compounds 7 and 8 show the protonated molecules and Na(+)-cationised ions with fragmentation processes related to the dithiocarbamate moiety. This behaviour indicates that coordination of ether- and ester-substituted dithiocarbamates to the [Tc [triple chemical bond] N] group is weaker than that of phosphinothiolates. Conversely, diethyldithiocarbamate inserted in mixed complex 9 enhances both C--N and Tc--S bonds, and fragmentation processes suggest that metal-phosphinothiolate and metal-dithiocarbamate show comparable strength.