A salicylaldiminate/Pd(trifluoroacetate)2 [SalAld/Pd(tfa)2] initiating system for C1 polymerization of diazoacetate: generation of an active initiator from ordinary reagents with facile procedures

Abstract

Salicylaldiminate (SalAld)-ligated Pd complexes were generated by the reaction of SalAld with Pd(tfa)₂ in THF, and their initiating ability for C1 polymerization of diazoacetate was investigated. When a mixture of a series of SalAlds and Pd(tfa)₂ ([SalAld]/[Pd(tfa)₂] = 2 : 1–4 : 1) was employed for the polymerization of ethyl diazoacetate (EDA), polyEDA’ with a high number-average molar mass (M_n,_SEC = 20000–35 000) was obtained in moderate yield; the polymer yield became highest (50%) when the polymerization was conducted with a [SalAld]/[Pd(tfa)₂] ratio of 4 : 1 at 50 °C for 13 h. NMR analyses indicated that polyEDA’ had a syndiotactic-rich main chain stereo-structure. These results demonstrate that the SalAld/Pd(tfa)₂ system is a new effective initiating system for the C1 polymerization of diazoacetate, which can be generated from a combination of ordinary reagents with facile procedures.