Chalcogen‐Driven Structural Modulation in Cesium Methanide Complexes: Impact on ROP Catalysis

This study explores the coordination chemistry and catalytic behavior of cesium‐based multinuclear complexes supported by bis(diphenylphosphino)chalcogenide ligands {CH 2 (P(E)Ph 2 ) 2 } [where E = S ( 1 ) and Se ( 2 )] in the ROP of cyclic esters. By reacting {CH 2 (P(E)Ph 2 ) 2 } with cesium amide [Cs{N(SiMe 3 ) 2 }], we isolated two distinct structural motifs: a one‐dimensional coordination polymer [CH{PPh 2 S} 2 Cs] ∞ ( 3 ) and a dimeric complex [CH{PPh 2 Se} 2 Cs] 2 ( 4 ). Furthermore, the intervention of 18‐crown‐6 in 1D polymeric ladder ( 3 ) commands the formation of contact pair [{18C6}Cs{CH(Ph 2 PS) 2 }] ( 5 ), whereas dimeric complex ( 4 ) leads to ion‐separated cesium complex [(18C6) 2 Cs] + [CH(PPh 2 Se) 2 ] − ( 6 ). This is one of the rare reports on the structural characterization of a discrete cesium molecular complex featuring a direct Cs–Se interaction, while only ionic solids were known. Complex 6 is the first ion‐pair to display the [HC(PPh 2 Se) 2 ] − anion in its unbound state, which has predominantly been observed in coordinated form with various metals. All complexes were characterized in solution by spectroscopic analysis ( 1 H and 31 P{ 1 H} NMR), and their solid‐state structures were confirmed by single‐crystal X‐ray diffraction analysis. Notably, the coordination polymer exhibited superior activity in ROP of rac ‐lactide and caprolactone compared to its dimeric or monomeric analog, suggesting a key role for extended metal–ligand cooperativity.