m-Metallaphenol: synthesis and reactivity studies

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Aromaticity Studies

Background:

• Osmium complexes are crucial in catalysis and materials science.
• The exploration of metallaphenols expands the understanding of aromaticity in inorganic systems.
• Previous research has not established osmaphenol complexes with aromatic character.

Purpose of the Study:

• To synthesize and characterize the first osmaphenol complex.
• To investigate the aromaticity of the novel osmaphenol complex.
• To explore the reactivity and synthetic utility of the osmaphenol complex.

Main Methods:

• Synthesis of osmium complex [Os{CHC-(PPh3 )CH(OH)-η(2) -C≡CH}(PPh3 )2 (NCS)2 ] (1) via treatment with triethylamine.
• Characterization using NMR spectroscopy, structural analysis, and nucleus-independent chemical-shift (NICS) calculations.
• Reactivity studies involving reactions with isocyanates, isothiocyanates, pyridine, and sodium thiocyanate.

Main Results:

• Successful synthesis of the first osmaphenol complex, [Os{CHC(PPh3 )CHC(OH)CH}(PPh3 )2 (NCS)2 ] (2).
• NMR, structural data, and NICS values confirm the aromatic character of osmaphenol 2.
• Osmaphenol 2 undergoes annulation reactions with isocyanates, isothiocyanates, pyridine, and sodium thiocyanate to form fused osmabenzene complexes.
• Reactions with electrophiles lead to decomposition, indicating high electrophilicity and nucleophilic reactivity.

Conclusions:

• The first osmaphenol complex with confirmed aromatic character has been synthesized.
• Osmaphenol 2 exhibits versatile reactivity, enabling the formation of novel fused osmabenzene structures.
• The complex's electrophilicity is attributed to the osmium metal center and phosphonium group.