Heavy Group 15 Element Pacman Complexes.

Area of Science:

• Organometallic Chemistry
• Macrocyclic Chemistry
• Pnictogen Chemistry

Background:

• Calix[4]pyrrole macrocycles, also known as Pacman ligands, offer a unique scaffold for coordinating metal ions and main group elements.
• Incorporating heavy pnictogens (As, Sb, Bi) into macrocyclic frameworks presents synthetic challenges and opportunities for novel reactivity.
• Understanding the coordination chemistry and reactivity of heavy pnictogens is crucial for developing new materials and catalysts.

Purpose of the Study:

• To synthesize and characterize novel halogeno-pnictogen complexes using calix[4]pyrrole macrocycles.
• To investigate the reactivity and stability of these heavy pnictogen complexes.
• To explore the potential for forming biradical species from these complexes.

Main Methods:

• Synthesis of halogeno-pnictogen complexes (Pac(EX)2) using calix[4]pyrrole ligands.
• Isolation and characterization of complexes using spectroscopic (NMR), crystallographic, and theoretical methods.
• Investigation of complex dynamics, hydrolysis, and reduction reactions.

Main Results:

• Successfully synthesized and isolated the arsenic(III) chloro complex Pac(AsCl)2.
• Formed but did not isolate arsenic(III), antimony(III), and bismuth(III) complexes.
• Observed temperature- and chloride-dependent dynamics in the arsenic(III) chloro complex.
• Identified oxygen-bridged complexes (Pac(E-O-E)) from hydrolysis.
• Isolated and characterized an intermediate PacH2(SbCl2)2 during SbCl2 synthesis.
• Bismuth(III) analogues were transiently detected.
• Reduction attempts led to decomposition, not biradical formation.

Conclusions:

• Calix[4]pyrrole macrocycles can effectively incorporate heavy pnictogens into stable complexes.
• The synthesized complexes exhibit unique reactivity, including hydrolysis and temperature-dependent dynamics.
• Direct formation of biradical species from these complexes via reduction is not feasible under the studied conditions.