Dicoordinate Au(I)-Ethylene Complexes as Hydroamination Catalysts.

Area of Science:

• Organometallic chemistry
• Catalysis

Background:

• Gold(I) complexes are effective catalysts.
• Ethylene hydroamination is an underexplored reaction.
• Sterically hindered ligands can enhance catalyst stability and performance.

Purpose of the Study:

• To prepare and investigate gold(I)-ethylene π-complexes with bulky phosphine ligands.
• To evaluate their catalytic activity in ethylene hydroamination.
• To elucidate the reaction mechanism.

Main Methods:

• Synthesis of gold(I)-ethylene π-complexes with bulky phosphine ligands.
• Catalytic testing of hydroamination of ethylene under mild conditions.
• Kinetic analysis and density functional theory (DFT) calculations.
• Kinetic isotopic effect studies.

Main Results:

• Sterically demanding phosphine ligands stabilize gold(I)-ethylene complexes and prevent decomposition.
• Precatalysts with highly hindered phosphines achieved full conversion under mild conditions (1 bar ethylene, 60 °C).
• Kinetic studies and DFT calculations suggest a proton shuttle mechanism involving a second nucleophile molecule.
• A primary kinetic isotopic effect indicates X-H bond cleavage in the rate-limiting step.

Conclusions:

• Bulky phosphine ligands are crucial for stabilizing gold(I)-ethylene complexes and improving catalytic hydroamination of ethylene.
• The reaction proceeds via a mechanism involving a proton shuttle, even with sterically demanding catalysts.
• The protodeauration step is rate-limiting and involves X-H bond breaking.