Synthesis, Crystal and Electronic Structures of a Thiophosphinoyl‐ and Amino‐Substituted Metallated Ylide

Abstract

α‐Metallated ylides have revealed themselves to be versatile reagents for the introduction of ylide groups. Herein, we report the synthesis of the thiophosphinoyl and piperidyl (Pip) substituted α‐metallated ylide [Ph 2 (Pip)P=C−P(S)Ph 2 ]M (M=Li, Na, K) through a four‐step synthetic procedure starting from diphenylmethylphosphine sulfide. Metallation of the ylide intermediate was successfully accomplished with different alkali metal bases delivering the lithium, sodium and potassium salts, the latter isolable in high yields. Structure analyses of the lithium and potassium compounds in the solid state with and without crown ether revealed different aggregates (monomer, dimer and hexamer) with the metals coordinated by the thiophosphoryl moiety and ylidic carbon atom. Although the piperidyl group does not coordinate to the metal, it significantly contributes to the stability of the yldiide by charge delocalization through negative hyperconjugation.

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

“…Furthermore, the metalation is accompanied by a significant increase of the 2 J P,P coupling constants, e.g., from 19.4 for the iminophosphinoyl substituted ylide 2a-N to 88.1 Hz in its metalated congener. These trends have been reported earlier for other metalated ylides and are well in line with the increasing charge at the ylidic carbon atom and the resulting shortening of the P–C bond. − …”

“…At the same time, the bonds between the phosphorus atoms and their substituents (P–N and P–C Ph ) elongate because of negative hyperconjugation effects. Both effects are typical for metalated ylides and contribute to the stability of these compounds. − They are in general on little affected by the aggregation of the compounds since the predominantly ionic interactions to the alkali metal cations have only a small influence on the charge on the central carbon atom. − …”

Thiophosphinoyl‐Tethered Ylide‐Substituted Heavier Carbenes: Synthesis, Structures and Stabilities

“…Nonetheless, these angles are much smaller than those observed in the metallated ylide Y‐K . For example, the largest P−C−P angle of 129.27(17)° in Y 2 Pb is still smaller than the P−C−P binding angle observed in the yldiide with 134.95(7) [18a] . A reason for the large angles are negative hyperconjugation effects that stabilize the negative charge at the ylidic carbon atom and have a direct influence on the bond lengths and angles.…”

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

“…In the former, a phosphine ligand is formally replaced by an anionic ligand X, thus rendering a different bonding description necessary (vide infra). Over the past few years, several metalated ylides have been isolated and applied in different research directions (Figure B), particularly as ylide-transfer reagents. − …”