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• C-H bond activation of coordinated pyridine: Ortho-pyridyl-di-technetiumhydridocarbonyl metal cyclus. Crystal structure and dynamic behaviour in solution.

M. Zuhayra, U. Lützen, A. Lützen, L. Papp, E. Henze, G. Friedrichs, F. Oberdorfer
Inorg. Chem. 47 (2008) 10177-10182.


The reaction of pyridine with ditechnetium decacarbonyl [Tc2(CO)10] (1) leads to a novel ortho-pyridyl-ditechnetium hydrido complex, [Tc2(μ-H)(μ-NC5H4)(NC5H5)2(CO)6] (2) and its precursor [Tc2(μ-CO)2(NC5H5)2(CO)6] (3). At ambient temperature 1 was found to react slowly with pyridine to afford substitution product 3 after 120 h. However, heating the reaction mixture to reflux exclusively leads to the pyridine-ortho-metalated complex 2 in only 30 minutes. Similarly, complex 3 can be converted completely into 2 upon heating in pyridine for 30 min. Both compounds 2 and 3 were characterized by NMR and X-ray analysis. Both compounds 2 and 3 do show a complex dynamic behaviour in solution that was investigated by 1-D and 2-D NMR spectroscopic means. Both compounds 2 and 3 show isomerisation in solution according to the relative position of the non-bridging pyridine ligands. For 2, the existence of three isomers was shown at equilibrium conditions, 2a (56%) with trans-diaxial, 2b (38%) with cis-diaxial and 2c (6%) with axial-equatorial arrangement of the non-bridging pyridines. For 3, an equilibrium was detected between two isomers, 3a (67%) with a cis-diaxial and 3b (33%) with a trans-diaxial arrangement of the pyridines.


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