Double Bond Cleavage in Small Molecules Using a Geminal Sc/P Lewis Pair.

Area of Science:

• Organometallic Chemistry
• Main Group Chemistry
• Catalysis

Background:

• Frustrated Lewis pairs (FLPs) activate small molecules via cooperative Lewis acid-Lewis base interactions.
• While FLPs excel at H-H bond cleavage, their ability to rupture double bonds is less explored.
• Developing FLPs for complete double bond cleavage remains a significant challenge in small molecule activation.

Purpose of the Study:

• To investigate the reactivity of a novel geminal scandium/phosphorus Lewis pair.
• To explore the capability of this FLP system in cleaving various unsaturated double bonds.
• To demonstrate the potential of rare-earth metal complexes in capturing reactive species.

Main Methods:

• Synthesis of a geminal Sc/P Lewis pair: (ArO)2ScN(tBu)PPh2.
• Reaction of the FLP with carbon dioxide (CO2) to confirm FLP-type reactivity.
• Testing the FLP's ability to cleave double bonds in azobenzene, pyridazine, nitrosobenzene, and N-sulfinylaniline.
• Characterization of resulting metallacyclic products.
• Formation and characterization of a rare-earth metal sulfur monoxide adduct from PhNSO.

Main Results:

• The Sc/P FLP demonstrated typical FLP-type 1,2-addition reactivity with CO2.
• Complete cleavage of N=N bonds in azobenzene and pyridazine was achieved.
• Cleavage of N=O bonds in nitrosobenzene and N=S/S=O bonds in N-sulfinylaniline was successful, yielding metallacycles.
• The first rare-earth metal sulfur monoxide adduct was synthesized via PhNSO bond cleavage.
• This highlights the capacity of rare-earth complexes to trap reactive species.

Conclusions:

• A novel geminal Sc/P Lewis pair exhibits potent FLP reactivity, extending beyond H-H bond cleavage.
• This FLP system effectively cleaves diverse double bonds (N=N, N=O, N=S, S=O), forming stable metallacycles.
• The study showcases the potential of rare-earth metal complexes in activating and capturing challenging small molecules and reactive intermediates.