Facile C(sp(2))/OR bond cleavage by Ru or Os.

Area of Science:

• Organometallic Chemistry
• Osmium Catalysis
• Reaction Mechanism Elucidation

Background:

• Osmium complexes of the type Os(H)(3)ClL(2) serve as versatile precursors in organometallic synthesis.
• Understanding the reactivity of these osmium complexes is crucial for developing new catalytic transformations.

Purpose of the Study:

• To investigate the reaction pathways of Os(H)(3)ClL(2) with vinyl ethers.
• To elucidate the mechanisms leading to carbene, carbyne, and vinylidene complex formation.
• To explore the influence of spectator ligands and substituents on reaction outcomes.

Main Methods:

• Synthesis and characterization of osmium complexes.
• Kinetic and mechanistic studies of reactions with vinyl ethers.
• Density Functional Theory (DFT) calculations (B3PW91) to probe reaction energetics and transition states.

Main Results:

• Os(H)(3)ClL(2) reacts with vinyl ethers to form eta(2)-olefin adducts, which isomerize to osmium carbenes, OsHCl[CMe(OR)]L(2).
• Subsequent R- and L-dependent reactions lead to C(sp(2))-OR bond cleavage, forming carbyne or vinylidene complexes.
• DFT calculations reveal thermodynamic differences between osmium and ruthenium, and highlight the impact of the OR group and phosphine ligands.

Conclusions:

• The study details a multi-step reaction sequence initiated by osmium hydride complexes and vinyl ethers.
• The formation of diverse osmium complexes (carbene, carbyne, vinylidene) is controlled by electronic and steric factors of the ligands and substituents.
• Computational analysis provides insights into the factors governing the reactivity and thermodynamic landscape of these osmium systems.