Synthesis and Structure of Chromium(VI) Nitrido Cyclopentadienyl Complexes

A series of rare nitrido cyclopentadienyl complexes have been prepared of chromium(VI). An improved synthesis of NCr(I)(NPri2)2 is provided, which reacts with NaCp to give NCr(η1-Cp)(NPri2)2 (1) in 82% isolated yield. The η1-indenyl complex 2 can be prepared using a similar procedure. Replacement of one diisopropylamido ligand was accomplished to prepare NCr(NPri2)Cp(O2CPh) (3), NCr(NPri2)Cp(Cl) (4), and [NCr(NPri2)Cp(NCMe)]+[SbF6]− (5). In the series, the Cr–C interactions increase in bond order, 3 < 4 < 5, as the cyclopentadienyl compensates for the decreasing donor ability of the other ligands on chromium. The Ligand Donor Parameters (LDPs) for the η1-cyclopentadienyl and η1-indenyl ligands were measured as 13.73 and 13.76 kcal/mol, respectively. Compounds 1–5 were characterized by single-crystal X-ray diffraction.