Start Date
April 2024
Location
2nd floor - Library
Abstract
Ligands with oxime functional groups are noted for their ability to stabilize normally inaccessible oxidation states, such as nickel (III) or copper (III). Our group has developed a series of distinctive ligands with one or three oxime groups. Our mono-oxime ligands are acetophenone oxime and 2-chloro-acetophenone oxime; the latter is used to synthesize our tri-oxime ligand, which we have named TRIPHOX; the three oxime N atoms and the core N atom all act as donor atoms.
A set of metal salts (MCl₂, where M = Fe, Co, Ni, Cu) were mixed with a mono-oxime ligand (acetophenone oxime). Solvents with different polarities were used, and the ratio of ligand:metal ranged from 1:1 to 6:1. The only significant color changes were observed with CuCl₂; this was not surprising, as Cu is the most reactive first-row transition metal. The products were characterized by UV-vis spectroscopy.
Three metal complexes were synthesized with the tri-oxime ligand: [M(TRIPHOX)Cl2], where M = Co, Ni, Cu. Two oxidants, barium perchlorate hydrate and ceric ammonium nitrate, were mixed with our complexes in hopes of achieving a higher oxidation state of the metals. The combination of [Ni(TRIPHOX)Cl2] and (NH₄)₂Ce(NO₃)₆ gave the most promising result. Addition of the reddish-orange cerium salt with the aqua-blue nickel complex led to an immediate change to a white suspension. The reduced form of cerium (Ce³⁺) is pale-yellow, suggesting the cerium was reduced, hence the Ni center was oxidized from +2 to +3. The +3 state of the nickel will be confirmed with a magnetic susceptibility balance.
High Oxidation States of First-Row Transition- Metal Complexes with Oxime-Based Ligands
2nd floor - Library
Ligands with oxime functional groups are noted for their ability to stabilize normally inaccessible oxidation states, such as nickel (III) or copper (III). Our group has developed a series of distinctive ligands with one or three oxime groups. Our mono-oxime ligands are acetophenone oxime and 2-chloro-acetophenone oxime; the latter is used to synthesize our tri-oxime ligand, which we have named TRIPHOX; the three oxime N atoms and the core N atom all act as donor atoms.
A set of metal salts (MCl₂, where M = Fe, Co, Ni, Cu) were mixed with a mono-oxime ligand (acetophenone oxime). Solvents with different polarities were used, and the ratio of ligand:metal ranged from 1:1 to 6:1. The only significant color changes were observed with CuCl₂; this was not surprising, as Cu is the most reactive first-row transition metal. The products were characterized by UV-vis spectroscopy.
Three metal complexes were synthesized with the tri-oxime ligand: [M(TRIPHOX)Cl2], where M = Co, Ni, Cu. Two oxidants, barium perchlorate hydrate and ceric ammonium nitrate, were mixed with our complexes in hopes of achieving a higher oxidation state of the metals. The combination of [Ni(TRIPHOX)Cl2] and (NH₄)₂Ce(NO₃)₆ gave the most promising result. Addition of the reddish-orange cerium salt with the aqua-blue nickel complex led to an immediate change to a white suspension. The reduced form of cerium (Ce³⁺) is pale-yellow, suggesting the cerium was reduced, hence the Ni center was oxidized from +2 to +3. The +3 state of the nickel will be confirmed with a magnetic susceptibility balance.
