Tris(pyrazolyl)phosphines with copper(i): from monomers to polymers

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Supramolecular Chemistry

Background:

• Tris(pyrazolyl)phosphine ligands are neutral analogues to tris(pyrazolyl)borate scorpionates.
• Phosphorus-centered scorpion ligands possess both N- and P-donor sites for metal coordination.
• Understanding the coordination behavior of these ligands is crucial for developing new metal complexes.

Purpose of the Study:

• To synthesize and characterize phosphorus-centered scorpion ligands and their derivatives.
• To investigate the coordination chemistry of these ligands with copper(I) ions.
• To explore the structural diversity of the resulting copper complexes, including discrete complexes and coordination polymers.

Main Methods:

• Simple synthetic procedures for ligand preparation.
• Phosphine selenide formation to assess Lewis basicity via (1)JP,Se coupling constants.
• X-ray crystallography for structural determination of copper complexes.
• Density Functional Theory (DFT) computational analysis.

Main Results:

• The parent and substituted tris(pyrazolyl)phosphine ligands exhibit modest Lewis basicity.
• Neutral P-scorpion ligands display unique coordination modes with Cu(I) compared to anionic scorpionates.
• Substituted ligands primarily coordinate through N-donors due to steric hindrance at the P-apex.
• Two distinct Cu(I) complex structures were determined: a discrete complex and a 1D coordination polymer.

Conclusions:

• Phosphorus-centered scorpion ligands offer versatile coordination strategies for metal ions.
• The chelating ability of both N- and P-sites allows for diverse structural outcomes.
• The ratio of ligand to metal dictates the formation of discrete complexes versus coordination polymers.
• These findings expand the scope of scorpion ligand chemistry and coordination polymer design.