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, [N 2C 2O 2] 4-, were formed from N-N bond cleavage coupled to N-C and C-C bond assembly. For the zirconium examples, [(η 5-C 5Me 4H) 2Zr] 2(μ 2,η 2,η 2-N 2) and [Me 2Si(η 5-C 5Me 4)(η 5-C 5H 3-3- tBu)Zr] 2(μ 2,η 2, η 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 [(η 5-C 5Me 4H) 2Hf] 2(μ 2,η 2,η 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 (μ-NH) ligands. In the case of the ansa-hafnocene dinitrogen complex, replacing the dihydrogen atmosphere with various primary silanes yielded an isocyanato hafnocene μ-oxo hydride resulting from cleavage of N 2 and CO, the diatomics with the two strongest bonds in chemistry.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry