A Family of 1,1,3,3‐Tetraalkylguanidine (H‐TAG) Solvated Zinc Aryloxide Precatalysts for the Ring‐Opening Polymerization of rac ‐Lactide

Reaction of [Zn(μ‐TAG){N(SiMe 3 ) 2 }] 2 {TAG = N=C[N(CH 2 CH 3 ) 2 N(CH 3 ) 2 ] (DEDMG), N=C{[NCH 2 CH 2 CH 2 C d H 2 ( N–C d )]N(CH 2 CH 3 ) 2 } (DEPYRG) and N=C{[NCH 2 CH 2 CH 2 CH 2 C e H 2 ( N–C e )]N(CH 2 CH 3 ) 2 } (DEPIPG)} with 2 equiv. of ethanol (EtOH) and 2 equiv. of HOAr {OAr = OC 6 H 3 (CMe 3 )‐2‐(CH 3 )‐6 (BMP) or OC 6 H 2 [C(CH 3 ) 3 ] 2 ‐2,6‐(CH 3 )‐4 (4MeDBP)} results in dizinc alkoxides with the general formula [Zn(μ‐OEt)(OAr)(H‐TAG)] 2 ( 1 – 3 ). Et 2 Zn was additionally treated with 2 equiv. of 1,1,3,3‐tetramethylguanidine (H‐TMG) and H‐BMP or HOC 6 H 3 (C 6 H 5 ) 2 ‐2,6 to yield [Zn(BMP) 2 (H‐TMG) 2 ] ( 4 ) and [Zn{OC 6 H 3 (C 6 H 5 ) 2 ‐2,6} 2 (H‐TMG) 2 ] ( 5 ). Complexes 1 , 2 , 4 , and 5 were characterized by single‐crystal X‐ray diffraction. Polymerization of rac ‐lactide with 1 – 5 and [Zn(μ‐OMe)(4MeDBP)(H‐TMG)] 2 ( 6 ) were found to generate polylactide (PLA). The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FTIR spectroscopy, and 1 H and 13 C NMR spectroscopic studies.