N-Donor stabilized tin() cations as efficient ROP catalysts for the synthesis of linear and star-shaped PLAs the activated monomer mechanism

α-Iminopyridine ligands L 1 (2-(CH&z.dbd;N(C 6 H 2 -2,4,6-Ph 3 ))C 5 H 4 N), L 2 (2-(CH&z.dbd;N(C 6 H 2 -2,4,6- t Bu 3 ))C 5 H 4 N) and L 3 (1,2-(C 5 H 4 N-2-CH&z.dbd;N) 2 CH 2 CH 2 ) differing by the steric demand of the substituent on the imine CH&z.dbd;N group and by the number of donating nitrogen atoms were utilized to initiate a Lewis base mediated ionization of SnCl 2 in an effort to prepare ionic tin( ii ) species [L 1-3 → SnCl][SnCl 3 ]. The reaction of L 1 and L 2 with SnCl 2 led to the formation of neutral adducts [L 1 → SnCl 2 ] ( 2 ) and [L 2 → SnCl 2 ] ( 3 ). The preparation of the desired ionic compounds was achieved by subsequent reactions of 2 and 3 with an equivalent of SnCl 2 or GaCl 3 . In contrast, ligand L 3 containing four donor nitrogen atoms showed the ability to ionize SnCl 2 and also Sn(OTf) 2 , yielding [L 3 → SnCl][SnCl 3 ] ( 7 ) and [L 3 → Sn(H 2 O)][OTf] 2 ( 8 ). The study thus revealed that the reaction is dependent on the type of the ligand. The prepared complexes 4-8 together with the previously reported [{2-((CH 3 )C&z.dbd;N(C 6 H 3 -2,6-iPr 2 ))-6-CH 3 O-C 5 H 3 N}SnCl][SnCl 3 ] ( 1 ) were tested as catalysts for the ROP of l -lactide, which could operate via an activated monomer mechanism. Finally, a DFT computational study was performed to evaluate the steric and electronic properties of the ionic tin( ii ) species 1 and 4-8 together with their ability to interact with the l -lactide monomer. N-donor stabilized tin( ii ) cations were synthesized by a chloride abstraction from neutral complexes or by an auto-ionization concept. Prepared tin( ii ) cations are universal catalysts for the production of linear and star-shaped PLAs via ROP.