Lewis Acid Supported Nickel Nitrenoids

Metalation of the polynucleating ligand F,tbsLH6 (1,3,5-C6H9(NC6H3-4-F-2-NSiMe2tBu)3) with two equivalents of Zn(N(SiMe3)2)2 affords the dinuclear product (F,tbsLH2)Zn2 (1), which can be further deprotonated to yield (F,tbsL)Zn2Li2(OEt2)4 (2). Transmetalation of 2 with NiCl2(py)2 yields the heterometallic, trinuclear cluster (F,tbsL)Zn2Ni(py) (3). Reduction of 3 with KC8 affords [KC222][(F,tbsL)Zn2Ni] (4) which features a monovalent Ni centre. Addition of 1-adamantyl azide to 4 generates the bridging mu 3-nitrenoid adduct [K(THF)3][(F,tbsL)Zn2Ni(mu 3-NAd)] (5). EPR spectroscopy reveals that the anionic cluster possesses a doublet ground state (S = 1/2 ${{ 1/2 }}$). Cyclic voltammetry of 5 reveals two fully reversible redox events. The dianionic nitrenoid [K2(THF)9][(F,tbsL)Zn2Ni(mu 3-NAd)] (6) was isolated and characterized while the neutral redox isomer was observed to undergo both intra- and intermolecular H-atom abstraction processes. Ni K-edge XAS studies suggest a divalent oxidation state for the Ni centres in both the monoanionic and dianionic [Zn2Ni] nitrenoid complexes. However, DFT analysis suggests Ni-borne oxidation for 5. Stepwise metalation of a polynucleating ligand generated heterobimetallic clusters featuring two redox inactive Lewis acids (Zn2+) and one transition metal (Ni). Reduction of the [Zn2Ni] cluster and reaction with a nitrene transfer reagent yielded [K(THF)3][(F,tbsL)Zn2Ni(mu 3-NAd)]. Ni K-edge XAS (X-ray absorption spectroscopy) studies support the assignment of the primary redox pair as a divalent nickel coupled to an imidyl ligand.+image