The scope of CO-induced N-2 cleavage in a series of zirconocene and hafnocene complexes containing activated, side-on bound dinitrogen ligands has been studied. In each case, bridging oxamidide ligands, [N2C2O2](4-), were formed from N-N bond cleavage coupled to N-C and C-C bond assembly. For the zirconium examples, [(eta(5)-C5Me4H)(2)Zr](2)(mu(2),eta(2),eta(2)-N-2) and [Me2Si(eta(5)-C5Me4)(eta(5)-C5H3-3-Bu-t)Zr](2)(mu(2),eta(2),eta(2)-N-2), dinitrogen loss became competitive with N-2 carbonylation, and significant quantities of the zirconocene dicarbonyl accompanied oxamidide formation. In contrast, the hafnocene complex [(eta(5)-C5Me4H)(2)Hf](2)(mu(2),eta(2),eta(2)-N-2) underwent clean carbonylative dinitrogen cleavage with no evidence of N-2 loss. CO-induced N-2 cleavage was also coupled to N-H bond formation by hydrogenation and C-H bond activation, as carbonylation of the zirconocene and hafnocene dinitrogen complexes in the presence of H-2 or phenylacetylene furnished isocyanato metallocene complexes with bridging imido (mu-NH) ligands. In the case of the ansa-hafnocene dinitrogen complex, replacing the dihydrogen atmosphere with various primary silanes yielded an isocyanato hafnocene mu-oxo hydride resulting from cleavage of N-2 and CO, the diatomics with the two strongest bonds in chemistry.