High Spin Cobalt Complexes Supported by a Trigonal Tris(Phosphinimide) Ligand.

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Terminal, π-basic moieties are crucial for stabilizing reactive inorganic species.
• Phosphinimides (PN) are known to stabilize electron-deficient early transition metals and lanthanides.
• The potential of PN ligands to stabilize high-valent late transition metals remains largely unexplored.

Purpose of the Study:

• To explore the hypothesis that terminal PN ligands can enable access to high-valent states of late first-row transition metals.
• To synthesize and characterize novel multidentate phosphinimide ligands.
• To investigate the coordination chemistry of these ligands with cobalt.

Main Methods:

• Development of a new procedure for electrophilic amination of multidentate phosphines.
• Synthesis of a trinuclear Co^II₃ complex and a homoleptic, three-coordinate Co^III complex.
• Characterization using X-ray diffraction (XRD), magnetic susceptibility measurements, and Density Functional Theory (DFT) calculations.

Main Results:

• Successful synthesis of multidentate phosphinimide ligands.
• Demonstration of terminal PN coordination to cobalt, forming Co^II₃ and Co^III complexes.
• The Co^III complex exhibits a rare S=2 ground state.
• DFT studies reveal strong dπ-pπ interactions between terminal PNs and cobalt.

Conclusions:

• Terminal PN ligands can stabilize high-valent states of late transition metals.
• The observed weak ligand field is suitable for stabilizing high-spin states.
• This work opens new avenues for exploring high-valent metal complexes with unique electronic properties.