Dynamic Permutational Isomerism in a closo-Cluster

Area of Science:

• Organometallic Chemistry
• Cluster Chemistry
• Materials Science

Background:

• Tetrahedral clusters featuring tungsten, rhodium, and iridium are complex structures.
• Understanding isomerism in these clusters is key to predicting their properties.

Purpose of the Study:

• To investigate the formation and interconversion of permutational isomers of a specific tungsten-rhodium-iridium cluster.
• To explore the differing chemical and physical properties of these isomers.

Main Methods:

• Synthesis of the tetrahedral cluster [W2Ir2(CO)10(η(5)-C5H5)2].
• Reaction with [Rh(CO)2(η(5)-C5HMe4)] to form trigonal bipyramidal clusters.
• Analysis of isomer interconversion in solution.
• Characterization of isomer-specific reactivity (CO replacement) and optical properties.

Main Results:

• Formation of permutational isomers of trigonal bipyramidal [W2RhIr2(CO)9(η(5)-C5H5)2(η(5)-C5HMe4)] via competitive capping.
• Observation of slow interconversion in solution attributed to cluster metal vertex exchange.
• Demonstration of isomer-specific reactivity with triphenylphosphine (PPh3).
• Identification of distinct optical power limiting behaviors between isomers.

Conclusions:

• Permutational isomerism in W2Ir2-based clusters arises from competitive capping reactions.
• Cluster metal vertex exchange facilitates isomer interconversion through specific bond cleavage and reformation.
• The distinct properties of these isomers, including reactivity and optical behavior, are directly linked to their specific geometric arrangements.