Technetium VI

Structural and IR Data for [TcviN]3 Halide Complexes and Some 

1 Value fixed in the refinement due to the statistical disorder of the ligands in the cubic space group. 

Solutions of 55 in 1 M p-toluenesulfonic acid, CF3S03H, or MeSOaH are pale yellow and shown by paper electrophoresis to contain a single cationic species (630, 640). Also, dilution of a solution of 56 in 7.5 M CF3S03H leads to the slow formation of the yellow species. That this species is the bis(p-oxo) aquanitrido cation [ TcN(0H2)3 2(p-0)2]2+ (57) is indicated by the similarity of the electronic spectrum to that of the well-established [ MoO(OH2)3 2(p-0)2]2+ cation, the absence of EPR signals, and the isolation of [ TcN(S2CNEt2) 2(p-0)2] on reaction with 

Na(S2CNEt2) (602). Structure 57 has been confirmed in solution by EXAFS studies, but the actual number of coordinated water molecules is uncertain (642). Addition of ethanol to a solution of 55 in aqueous CsOH precipitates the yellow Cs2[ TcN(0H)2 2(/u,-0)2] with v(TcN) at 1046 cm 1 and v(TcOTc) at 734 cm-1. On treatment with HC1 this salt is converted to [TcNC14] (640). 

The reaction of [Tc(NAr)3I] with Na/THF at room temperature yields the homoleptic diamagnetic dimer [Tc2(NAr)6] (Ar = 2,6-diisopropyl-phenyl). The dimer is air-stable in solution and adopts an unprecedented ethane-like structure (61), with the six imido ligands symmetry equivalent in a staggered arrangement. 

Though hexavalcnt technetium is known to be highly sensitive to oxydation and disproportionation, for instance in the case of tetraoxotcchnetale(Vl) [30, numerous complex compounds of rc(VI) were synthesized and identified and proved to be rather stable under normal conditions. Imido and predominantly nitrido ligands frequently act in mono- and dinuclear complexes as strong stabilizing Tr-clcctron donors [31]. In fluoro complexes the coordination numbers 7 and 8 are verified. In addition catccholato and thiolato ligands form well defined compounds. EPR spectroscopy was shown to be an efficient tool to characterize the complexes. 

A = 230 X 10 and Aj = 96 x 10 cm After 1 hr the blue color vanishes and the EPR signal decreases (612). Unstable deep-blue 

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Technetium(vi) and Rhenium(vi).- Values for certain thermodynamic parameters of TcOF4 and ReOF4 have been computed.237 The i.r. spectra have been recorded for ReOF4 as a thin film and isolated in an Ar matrix and these data compared to Raman data obtained for this compound dissolved in HF solutions. All of this information is consistent with a C4r molecular geometry for ReOF4 monomers 679... 

The radioligand X exchange in systems containing tetra- and penta-halogenonitrido-technetium(VI) complexes would provide useful information concerning the nature of the... 

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