Phosphines (PR3) are widely used in transition metal-catalyzed reactions. One of their many attractive features is the fact that their steric and electronic properties can be easily adjusted in a predictable manner by variation of the R substituents. As a consequence, their application as ancillary ligands in catalysis has led to major breakthroughs in many fields of academic and industrial research. Specifically, strong electron-donating alkylphosphines are the ligands of choice when electron-rich metal centers are required. As part of our program to enhance the donor strength of phosphines we reported a new approach to highly electron-rich phosphines based on the use of imidazolin-2-ylidenamino groups directly attached to the phosphorus atom. These phosphines display excellent donor properties, which exceed that of N-heterocyclic carbenes. Investigations of the basicity of the phosphines reveals a pKBH+(THF) values up to 31.0 and a correlation with their donor strength. Thus, P(NIiPr)3 is the strongest reported nonionic phosphorus(III) superbase and in the range of the phosphazene superbases. Due to its unique electronic properties it is able to bind and cleave CO2.

Imidazolin-2-ylidenaminophosphines: A highly electron-rich phosphorus(III) superbase that splits CO2

253rd National Meeting (2017)

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