Carbonyl and cyclopentadienyl complexes

The asymmetric compound [(pico)Cl2(pico)-Tc-0-TcCl(pico)3Cl ° is an isomer to the just described dissymmetric compound. The two types of complexes differ in their arrangement of equatorial ligands around each Tc atom. Both complexes were prepared in the same route. The asymmetric species was suggested to be the precursor of the dissymmetric complex, lire dark reddish-brown [(pico)Cl3(pico)-Tc-0-TcCl (pico)3Cl]° crystallizes in the monoclinic space group P2jln with n=]2.421(1), 6=15.471(1). c-18.764(1) A. /1=93.174(5) , and Z=4. The geometry around each Tc atom is essentially octahedral, lire Tc atoms are linked by a p-oxo bridge with the 

The bis(/i-oxo) mixed valence complex anion [(tcta)l c (/i-0)2Tc (tcta)] (where teta = l,4,7-triazacyclononane-N,N, N -triacetate) was obtained as a deep inky blue 

The optical spectrum of [(tcta)Tc (/(-0)2Tc (tcta)] in water is dominated by an intense band at 592 nm [497]. 

The analogous tetraacetato complex [Tc2(CH3COO)4Cl2]° was obtained by reaction of KTCO4 with HCl and CH3COOH in an atmosphere of hydrogen, llic cherry-red crystals arc insoluble in hydrochloric and acetic acids, alcohol, acetone, and ether and are 

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Although carbonyl and cyclopentadienyl complexes are well known for Tc(I) and Tc(III), none appear to have been reported for Tc(II). This may be ascribed to the tendency to follow the 18-electron rule, which, due to the odd number of electrons, would require dimer formation for compliance. Similarly, no Tc(II) cyano or isonitrile complexes appear to have been isolated. 

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