ABSTRACT 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 CsN (SiMe 3) 2, we isolated two distinct structural motifs: a one‐dimensional coordination polymer CHPPh 2 S 2 Cs ∞ (3) and a dimeric complex CHPPh 2 Se 2 Cs 2 (4). Furthermore, the intervention of 18‐crown‐6 in 1D polymeric ladder (3) commands the formation of contact pair 18C6CsCH (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.
Sharma et al. (Wed,) studied this question.