Competitive C-I versus C-CN reductive elimination from a Rh(III) complex. Selectivity is controlled by the solvent

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Reaction Mechanisms

Background:

• The RhIII complex [(PNP)Rh(CN)(CH3)][I] (5) is synthesized via oxidative addition of methyl iodide to [(PNP)Rh(CN)] (2).
• Understanding the reactivity of such complexes is crucial for developing new catalytic processes and materials.

Purpose of the Study:

• To investigate the selective reaction pathways of the RhIII complex [(PNP)Rh(CN)(CH3)][I] (5).
• To elucidate the role of solvent polarity in directing the reaction outcomes.
• To understand the mechanism of electrophilic attack on the cyano ligand.

Main Methods:

• Synthesis of the RhIII complex [(PNP)Rh(CN)(CH3)][I] (5).
• Reaction of the complex in various aprotic and protic solvents with alkyl iodides.
• Characterization of products using spectroscopic techniques and X-ray diffraction.

Main Results:

• In aprotic solvents, C-I reductive elimination of methyl iodide occurs, followed by electrophilic attack on the cyano ligand, yielding the methyl isonitrile RhI complex [(PNP)Rh(CNCH3)][I] (3).
• In protic solvents, C-C reductive elimination of acetonitrile occurs, forming the iodo RhI complex [(PNP)RhI] (9).
• X-ray diffraction confirmed hydrogen bonding between the cyano ligand and protic solvents, hindering electrophilic attack.

Conclusions:

• The solvent dictates the reaction pathway of the RhIII complex, leading to distinct RhI products.
• Hydrogen bonding interactions play a critical role in modulating the reactivity of the cyano ligand.
• This study provides insights into selective transformations in organometallic chemistry.