Phosphinoyl-Substituted Ketenyl Anions: Synthesis and Substituent Effects on the Structural Properties

Abstract

Ketenyl anions are versatile intermediates in synthetic chemistry and have recently become accessible as isolable reagents from metalated ylides by exchange of the phosphine with CO. Herein, we report on a systematic study of substituent effects on the structure and bonding situation in ketenyl anions. A series of phosphinoyl-substituted ketenyl anions {[R 2 P(X)CCO] − with X = O, NTol, S, Se} were prepared by carbonylation of the corresponding yldiides and isolated as their corresponding potassium salts. NMR and IR spectroscopic analyses together with computational studies demonstrate that the more electronwithdrawing oxo-and iminophosphinoyl substituents increase the s-character in the bond to the ketene moiety and hence the ynolate character of the anion. This trend is particularly seen in solution, whereas the solid-state properties are influenced by packing effects affecting the bonding situation.

Ligand Exchange at Carbon: Synthetic Entry to Elusive Species and Versatile Reagents

“…Successful carbonylation to the ketenyl anions 28a – d was proven for a series of phosphinoyl-substituted metalated ylides 26 , allowing for the investigation of the influence of the substituents on the electronic structure (Scheme ). Although all of the ketenyl anions were accessible in high yields and could be crystallographically characterized, no obvious trends could be observed in the solid-state structures. This was explained by the flat energy potential for the bending of the P–C–C unit, which is presumably influenced by packing effects or disorders in the crystal and thus also affects bond lengths.…”