Reversible Carbon Dioxide Binding by Simple Lewis Base Adducts with Electron-Rich Phosphines

For
the efficient utilization of carbon dioxide as feedstock in
chemical synthesis, low-energy-barrier CO2 activation is
a valuable tool. We report a metal-free approach to reversible CO2 binding under mild conditions based on simple Lewis base
adducts with electron-rich phosphines. Variable-temperature NMR studies
and DFT calculations reveal almost thermoneutral CO2 binding
with low-energy barriers or stable CO2 adduct formation
depending on the phosphines donor ability. The most basic phosphine
forms an air-stable CO2 adduct that was used as phosphine
transfer agent, providing a convenient access to transition-metal
complexes with highly electron-rich phosphine ligands relevant to
catalysis.