Dimeric zirconium benzyl and amide complexes supported by an imidazolone framework have been successfully synthesized and fully characterized. The amide complexes were found to be effective catalysts for intramolecular hydroamination of primary and secondary amines.

No abstract

In 1972 Bower and Tennett first synthesized a series of tetra-1-norbornyl derivatives, (nor) 4 M, of the first-row transition metals from titanium to cobalt. These were found to be exceptionally stable for homoleptic metal alkyls containing only metal−carbon σ-bonds. The theoretical energies for the dissociation of 1-norbornyl ligands from these unusually high oxidation state organometallics through the reactions (nor) 4 M → (nor) 3 M + nor • and (nor) 4 M → (nor) 2 M + nor-nor indicate that dispersion effects play an important role in determining their exceptional stability. Thus, all of the (nor) 4 M (M = Ti to Cu) derivatives are viable with respect to 1-norbornyl radical dissociation when the London dispersion effect is considered. However, (nor) 4 Cu becomes disfavored if the dispersion correction is ignored. Thus, the stability of the (nor) 4 M molecules is seen to arise from the favorable combination of steric and dispersion force effects of the four 1-norbornyl groups tetrahedrally disposed around the metal atom and maximizing the dispersion attraction between them in a spherical hydrocarbon structure with a central metal atom. The tri-1-norbornyl derivatives (nor) 3 M appear be disfavored with respect to disproportionation into (nor) 4 M + (nor) 2 M. This is consistent with the experimental syntheses of the (nor) 4 M (M = Cr to Co) derivatives with the metal in the +4 oxidation by reactions with 1norbornyllithium with metal halides in the +2 or +3 metal oxidation states. Both the OPBE method and the BPW91 method predict high-spin states for the d 2 and d 3 complexes (nor) 4 Cr and (nor) 4 Mn but low-spin states for (nor) 4 Fe and (nor) 4 Co, consistent with experiment.

No abstract

We report a nonreductive process mediated by zirconium alkyl complexes for the C-H bond activation and C-N bond cleavage of an anionic amino-linked carbene at room temperature. Reacting the amino-linked NHC with Zr(Bz) 4 led to the isolation of a rare species of metastable Zr complex possessing an azaallyl and an η 2 -N,C-imidazolyl carbene moiety.