Technetium bonded ligands

Tc(IV) [or Tc(VII)] and Tc. An analogous tendency was observed for these clusters in aqueous solutions [11,80,87]. Polynuclear technetium clusters decompose with the formation of metallic technetium, i.e. the system of M-M bonds in this case appears to be more stable than the bonding of technetium with ligands. 

E. O. Fischer was the first to prepare arene complexes of technetium. Arene ligands in these compound are typically six-electron donors. The nature of the Tc-arene bond is probably very similar to the one of the Tc-Cp bond. The [Tc(arene)2] complexes (arene = benzene or hexamethylbenzene) are prepared by the reaction of TcCLt with the appropriate arene in the presence of AICI3/AI. In a typical reaction, TcCLt, AICI3, and aluminum were heated with benzene in a sealed tube to 135 °C for two days. The product is precipitated as a salt using the hexafluorophosphate ion. A variety of other 18-electron compounds can be prepared from this material, particularly through chemical reduction. 

Polynuclear Carbonyls. Several stmctures consist of dinuclear metal carbonyls as shown in stmctures (4)—(6). The metal atoms in Mn2(CO) Q, as also for technetium and rhenium, are held together by a metal—metal bond and the compound contains 10 terminal CO ligands, five coordinated to each atom. The CO ligands of Mn2(00) 0 adopt a staggered configuration as illustrated in stmcture... 

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. 

Thus, the investigations performed have shown that cluster fragments in technetium compounds are thermally rather stable. However, in a number of compounds thermal decomposition occurs at comparatively low temperatures, which is mainly related to the instability of organic cations and the weak bonding of technetium with organic ligands. 

The Tc complex [TcI(N—Ar)s] (28) (see Section 5.2.2.1.2) can be reduced with Na° in THE to yield the green, nonbridged, dinuclear compound [Tc2(NAr)6] (46), in which three imido-ligands are bound to the Tc center and connected by a single bond to the second technetium. The molecule has a staggered, ethane-like structure and is diamagnetic. Reduction of (28) yields another homoleptic imido-complex of Tc, the imido-bridged, tetrahedral, dinuclear compound [Tc2(/u-NAr )2(NAr )4] (47) (Ar = 2,6-diisopropylphenyl). The conformation could be confirmed by X-ray structure analysis the assumption of a Tc Tc bond is confirmed by the... 

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