Tc-X bonds

The broken bonds (boldface = dissociated BDEs (boldface = recommended data reference in parentheses) Methods (reference in  

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Tc—X bonds and the lability of X-ligands, but it has not been investigated, unlike tungsten cyanide complexes and unlike the Cl exchange between gaseous HCl and organic HCl solvates. The equilibrium in dichloromethane has been studied by Thomas and coworkers. ... 

Table 7.2 Effective bond order, total bond order, Tc-Tc and Tc-X bond distances (A) for the TcjXg (X = Cl, Br) calculated at the CASPT2/VTZP level of theory.

As observed from X-ray crystal data, which are available for a variety of complexes [4,5,6], oxotechnetium complexes show the following general feature the metal lies above the equatorial plane of the four basal ligand atoms and the oxo group is at the apex. Tc=0 bond lengths correlate with the displacement of the technetium atom from the basal plane towards the oxygen at the apical position. 

In order to elucidate the causes of the increased stability of the hydrolyzed cluster ions compared with the unhydrolyzed ions, further studies were made of the behaviour of [Te2X8]3 (where X = Cl,Br, or I) in solutions of hydrogen halides [43,52,80,87]. The studies were performed mainly in relation to the most stable and most readily synthesized [Tc2C18]3- ion (Fig. la) kinetic methods with optical recording were employed. The identity of the reaction products was in most cases confirmed by their isolation in the solid phase. The studies showed that the stability of the [Tc2X8]3 ions (where X = Cl, Br, or I) in aqueous solutions is determined by the sum of competing processes acid hydrolysis complex formation with subsequent disproportionation and dissociation of the M-M bonds, and oxidative addition of atmospheric oxygen to the Tc-Tc multiple bond. 

A number of X-ray crystal structures of these complexes with aliphatic diamines and the trans [0=Tc=0]" core have been elucidated. They all have in common that the Tc=0 distances are elongated in comparison to the Tc=0 monooxo counterparts. Typical Tc—O bond lengths are around 1.75 A, whereas the average Tc—distances range from 2.15 A to 2.2 A compar-... 

Another type of complex in which Tc C bonds predominate is the seven-coordinate complex [Tc(CNR)gX] + (398) (R = variety of organic groups X = C1, Br). The compounds are easily prepared in good yield by reaction of the Tc complex [Tc(CNR)6] " with Br2 or CI2 in acetonitrile. Attempts to introduce a bipy ligand as well led to dealkylation of the isocyanide to give the seven-coordinate complex [Tc(CNR)5(CN)X]+ (399). Reductive coupling of the coordinated isocyanides was attempted, but the reduction of Tc to Tc was the only reaction." ... 

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