Chiral SalenCr and SalanCr complexes with bulky substituents for asymmetric alternating copolymerization of cyclohexene oxide with carbon dioxide or phthalic anhydride

• New chiral salenCr and salanCr complexes with bulky substituents. • Different structures and substituents affect the catalytic performance greatly. • Stereoregular PCHCs and PCHPs with moderate ee for the CHO units. A series of new chiral salenCr and salanCr complexes bearing ( R,R )-1,2-diaminocyclohexane backbone with bulky substituents (cumyl, 1,1-diphenylethyl and trityl) at the ortho-position of the aryloxide moieties were synthesized and investigated as catalysts in the asymmetric copolymerization of cyclohexene oxide (CHO) with CO 2 or phthalic anhydride (PA). The substituents of the Cr complexes affect the catalytic activity as well as stereoselectivity greatly toward the copolymerizations. The different salen/salan backbones of the Cr complexes also play an important role on catalytic performance. Poly(cyclohexene carbonate)s (PCHCs) with number-average molecular weight (M n ) of 4.8-9.1 kg·mol −1 and 19.0-19.4% enantiomeric excess (ee) value of the 1,2-cyclohexanediol unit were prepared by using salenCr with 1,1-diphenylethyl groups and salanCr with cumyl or 1,1-diphenylethyl groups as catalyst, respectively. Poly(cyclohexene phthalate)s (PCHPs) with M n of 1.6 kg·mol −1 and ee value of 7.1-8.7% were obtained by using salenCr with cumyl or 1,1-diphenylethyl groups as catalyst, respectively. While, the salanCr complexes resulted in atactic PCHPs.