Initiating abilities of diphosphine- and diamine-ligated Pd complexes/NaBPh4 systems for C1 polymerization of diazoacetates

Abstract

A series of well-defined Pd complexes bearing diphosphines or diamines and a dichloroquinone-derived unit as ligands were newly prepared and their initiating abilities in conjunction with NaBPh₄ for the C1 polymerization of diazoacetates were investigated. Among the (diphosphine)Pd(II)Cl(Cl-quinonyl) complexes examined here, square planar cis (diphosphine: diphenylphosphinoferrocene) and distorted square planar trans (diphosphine: xantphos) complexes with NaBPh₄ yielded highly syndiotactic polymers from ethyl diazoacetate despite low polymer yields. A series of Pd(0) complexes bearing a bidentate diamine such as N,N,N′,N′-tetramethyl-1,3-propanediamine and 2,3-dichloronaphthoquinone in conjunction with NaBPh₄ polymerized diazoacetates to afford moderately syndiotactic polymers in moderate yields, indicating that the (diamine)Pd(0)(dichloroquinone) framework could be a promising general platform for an initiating system with high activity and stereoselectivity for the C1 polymerization of diazoacetates.