Lewis Acid Supported Nickel Nitrenoids.

Metalation of the polynucleating ligand F,tbs LH6 (1,3,5-C6 H9 (NC6 H3 -4-F-2-NSiMe2 t Bu)3 ) with two equivalents of Zn(N(SiMe3 )2 )2 affords the dinuclear product (F,tbs LH2 )Zn2 (1), which can be further deprotonated to yield (F,tbs L)Zn2 Li2 (OEt2 )4 (2). Transmetalation of 2 with NiCl2 (py)2 yields the heterometallic, trinuclear cluster (F,tbs L)Zn2 Ni(py) (3). Reduction of 3 with KC8 affords [KC222 ][(F,tbs L)Zn2 Ni] (4) which features a monovalent Ni centre. Addition of 1-adamantyl azide to 4 generates the bridging µ3 -nitrenoid adduct [K(THF)3 ][(F,tbs L)Zn2 Ni(µ3 -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,tbs L)Zn2 Ni(µ3 -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 [Zn2 Ni] nitrenoid complexes. However, DFT analysis suggests Ni-borne oxidation for 5.

Surface Chemistry Controls the Density of States in Metallic Nanoparticles.

Ligand-stabilized colloidal metallic nanoparticles are prized in science and technology for their electronic properties and tunable surface chemistry. However, little is known about the interplay between these two aspects of the particles. A particularly glaring absence concerns the density of electronic states, which is fundamental in explaining the electronic properties of solid-state materials. In part, this absence owes to the difficulty in the experimental determination of the parameter for colloidal systems. Herein, we demonstrate the density of electronic states for metallic colloidal particles can be determined from their magnetic susceptibility, measured using nuclear magnetic resonance spectroscopy. For this study, we use small alkanethiolate protected gold nanoparticles and demonstrate that changes in the surface chemistry, as subtle as changes in alkane chain length, can result inasmuch as a 3-fold change in the density of states at the Fermi level for these particles. This suggests that surface chemistry can be a powerful tool for controlling the electronic behavior of the materials to which they are attached, and suggests a paradigm that could be applied to other metallic systems, such as other metal nanoparticles, doped semiconductor systems, and even 2D metals. For all of these metallic systems, the Evans method can serve as a simple means to probe the density of states near the Fermi level.