Cobalt Cyclopentadienyl-Phosphine Dinitrogen Complexes

Abstract

By applying the potassium salts of cyclopentadienyl-phosphine ligands LK to CoCl₂ , the corresponding cobalt chlorides (1, LCo^II Cl) were prepared. By reducing complexes 1 with KHBEt₃ under a N₂ atmosphere, bridging end-on complexes, LCo^I -N₂ -Co^I L (2 a and 2 b), were successfully obtained. ¹⁵ N₂ -labeled [¹⁵ N₂ ]-2 a was prepared under ¹⁵ N₂ /¹⁴ N₂ exchange in THF solution. LCo^I -N₂ -Co^I L complex 2 a could react with P₄ molecules to release N₂ and generate a Co-P₄ -Co moiety 4. Further reduction of complex 2 b led to cleavage of a P-C bond in the cyclopentadienyl-phosphine ligand to provide novel μ-PCy₂ -bridged Co⁰ -N₂ complex 5. DFT calculations confirmed the experimental observations.

Keywords: P4 activation; cobalt; dinitrogen activation; dinitrogen fixation.