Zwitterionic 2‐Phosphaethene‐thiolates [(L_C)P=CS(L_C/P)]⁺ as PCS Building Blocks (L_C=NHC, L_P=PR₃)

Abstract The zwitterionic compounds [(L C )P=CS(L C/P )] + ( 3 + , L C =NHC, L P =PR 3 ), featuring cationic substituents at the phosphorus and carbon atoms, are synthesized as their triflate salts at a multi‐gram scale from the reaction of Lewis base adducts of CS 2 , namely L C/P −CS 2 ( 4 ), with a combination of [(L C P) 4 ][OTf] 4 ( 1 [OTf] 4 ) and Ph 3 P. The feasibility of using 3 + as PCS building blocks is showcased in their reactions with representative electrophiles (MeOTf) and nucleophiles (MesMgBr, Ph 3 PCH 2 ), leading to selective functionalization of the PCS core at the S ‐ and P ‐terminus, respectively. Additionally, it is reported that 3 + can function as ambident nucleophiles with AgOTf (2 equivalents), affording unprecedented linear coordination polymer [Ag 2 (OTf) 3 ‐μ 2 :κ P ,κ S −((L C )P=CS(PCy 3 ))] + ( 6 b ), where the PCS moiety acts as a bridging ligand in transition metal complexes for the first time. Reduction of 3 + facilitates the cleavage of the P ‐ and C ‐bound substituents leading to the formation of the [PCS] − anion. Moreover, cycloaddition reactions of 3 + with 1 [OTf] 4 are shown to selectively yield five‐ and eight‐membered polyphosphorus heterocycles. Preliminary results suggest the possibility of activating the C−S bond in [(L C )P=CS(L C )] + , resulting in the formation of [(L C )P=C(L C )−P(L C )][OTf] 2 , 12 [OTf] 2 , which may serve as a synthon for the PCP unit in future studies.