European Journal of Inorganic Chemistry
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Editor: Karen Hindson, Deputy Editor: Preeti Vashi
Impact Factor: 2.686
ISI Journal Citation Reports © Ranking: 2015: 12/46 (Chemistry Inorganic & Nuclear)
Online ISSN: 1099-0682
Associated Title(s): Angewandte Chemie International Edition, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemCatChem, Zeitschrift für anorganische und allgemeine Chemie
European Journal of Inorganic Chemistry ,
April 4, 2013
When Boron Butts In
Bridging N–N ligand borylation in group 4 metallocene complexes
For Nature and chemists alike, making atmospheric nitrogen available for the formation of more complex nitrogen compounds is both essential and difficult. In the European Journal of Inorganic Chemistry, Paul Chirik and Scott Semproni at Princeton University, USA, report the first examples of the use of group 4 metallocene complexes for boron–nitrogen bond formation from elemental N2.
The bond in molecular nitrogen (N2) is very hard to cleave. Transition metal complexes have been used more and more to this end, and recently it was shown that N–N bond cleavage can be coupled to N–element bond formation by use of suitable reagents. Chirik and Semproni achieved this change by treating hafno- and zirconocene complexes containing a highly activated, side-on bound bridging N–N ligand with pinacolborane. Subsequent carbonylation of the borylated fragment leads to N–N bond cleavage and concomitant N–C bond formation.
In contrast, treatment of the borylated metallocene with cyclohexanecarbonitrile or tert-butylisocyanide results only in the insertion of the cyanide ligand into the metal–hydrogen bond but not in cleavage of the N–N bond.
The cyclopentadienyl rings used in the metallocene complexes are well suited for the construction of more elaborate nitrogen-based ligands after dinitrogen functionalization, as they are robust and do not give rise to undesired ancillary ligation. The clean reactivity reported was achieved by a systematic study of the substitution of these ligands to obtain the appropriate activation of the side-on bound N2 ligand. These reactions expand the scope of CO-induced N–N bond cleavage.
About the Author
Professor Paul Chirik works in the Department of Chemistry at Princeton University. His research involves the use of complexes of early transition metals for the activation and functionalization of atmospheric nitrogen as well as the catalytic chemistry of well-defined iron compounds.