title: Carbon monoxide-induced dinitrogen cleavage with group 4 metallocenes: reaction scope and coupling to N-H bond formation and CO deoxygenation.
abstract: 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(2)C(2)O(2)](4-), were formed from N-N bond cleavage coupled to N-C and C-C bond assembly. For the zirconium examples, [(eta(5)-C(5)Me(4)H)(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) and [Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(3)-3-(t)Bu)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)-C(5)Me(4)H)(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.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Knobloch
authors.forename: Emil
authors.initials: E
authors.lastname: Lobkovsky
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Chirik
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; C013108:metallocene; C023398:Zirconocene dichloride; D002248:Carbon Monoxide; D015040:Zirconium; D009584:Nitrogen