The reaction of pyridine with ditechnetium decacarbonyl [Tc-2(CO)(10)] (1) leads to a novel ortho-pyridyl-ditechnetium hydrido complex, [Tc-2(mu-H)(mu-NC5H4)(Nc(5)H(5))(2)(CO)(6)] (2) and its precursor [Tc-2(mu-CO)(2)(NC5H5)(2)(CO)(6)] (3). At ambient temperature 1 was found to react slowly with pyridine to afford the 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 min. 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 spectroscopy and X-ray analysis. Both compounds 2 and 3 show a complex dynamic behavior in solution that was investigated by one-dimensional and two-dimensional NMR spectroscopy. Both compounds 2 and 3 show isomerization 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 transdiaxial, 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 transdiaxial arrangement of the pyridines.