Solid-state induced control of kinetically unstable stereoisomers

Area of Science:

• Organometallic Chemistry
• Stereochemistry
• Solid-State Chemistry

Background:

• Arene complexes of the form TpM(pi-acid)(L)(eta2-arene) feature a hydridotris(pyrazolyl)borate ligand and a metal center (Re, Mo, W).
• These complexes involve pi-acid ligands (CO, NO) and ancillary ligands (1-alkylimidazole, pyridine, PMe3), with a prochiral eta2-arene.
• Understanding the stereochemical behavior of these complexes in different phases is crucial for designing stereoselective reactions.

Purpose of the Study:

• To investigate the solution and solid-state diastereomeric behavior of TpM(pi-acid)(L)(eta2-arene) complexes.
• To explore the potential for stereoselective reactions on the bound arene moiety by leveraging solid-state properties.
• To elucidate the influence of the solid phase on the stereochemical outcome of reactions involving prochiral arenes.

Main Methods:

• Synthesis of various arene complexes with different metal centers and ligands.
• Solution NMR spectroscopy to study dynamic equilibrium of coordination diastereomers.
• X-ray crystallography to determine solid-state structures and diastereomeric composition.
• Performing chemical transformations on the bound arene in both solution and solid states.

Main Results:

• Complexes exist as a dynamic equilibrium of coordination diastereomers in solution.
• In the crystalline and amorphous solid states, only a single diastereomer is observed.
• Reactions performed on the bound arenes in the solid state proceed stereoselectively.
• The homomorphic nature of the solid phase dictates the stereochemical outcome.

Conclusions:

• The solid state provides a platform for controlling stereochemistry in arene complexes.
• Exploiting the diastereomerically pure solid phase allows for highly stereoselective functionalization of prochiral arenes.
• This work demonstrates a strategy for achieving stereocontrol in organometallic chemistry through solid-state effects.