N3/4-pyridinyl Schiff base copper(II) benzoate complexes: synthesis, crystal structures and ring-opening polymerization studies

• Published in: Transition metal chemistry (Weinheim) 2022-03, Vol.47 (2-3), p.113-126
• Main Authors: Akintayo, Damilola C., Munzeiwa, Wisdom A., Jonnalagadda, Sreekantha B., Omondi, Bernard
• Format: Article
• Language: English
• Subjects: Benzoates; Butanol; Catalysis; Chemical synthesis; Chemistry; Chemistry and Materials Science; Coordination compounds; Copper; Crystal structure; Crystals; Geometry; Imines; Inorganic Chemistry; Ligands; Low molecular weights; Organometallic Chemistry; Physical Chemistry; Polymerization; Ring opening polymerization; Single crystals; Steric hindrance; Structural analysis
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-022-00494-8

Five benzoate complexes of copper(II) were synthesized by the reaction of N -donor Schiff base ligands with copper(II) acetate and benzoate co-ligands. All complexes were characterized by physicochemical, spectroscopic techniques and single-crystal X-ray diffraction studies. Crystal structure analysis revealed mononuclear complexes Cu(C 6 H 5 COO) 2 ( L1 ) 2 ·H 2 O ( 1 ) with a square pyramidal geometry and Cu(Me-C 6 H 5 COO) 2 ( L2 ) 2 ·2H 2 O ( 3 ) with a distorted octahedral geometry around the Cu(II) center. Three other complexes [Cu(C 6 H 5 COO) 2 ( L2 )] 2 ·( 2 ), [Cu(Me-C 6 H 5 COO) 2 ( L3 )] 2 ·( 4 ) and [Cu(C 6 H 5 COO) 2 ( L4 )] 2 ·( 5 ) all adopted a paddlewheel conformation in which the two Cu(II) centers each have a square pyramidal geometry. All complexes were found to be active as catalyst in ring-opening polymerization of ɛ-caprolactone (ε-CL), yielding low molecular weight polymers of about 2200 g mol −1 to 3870 g mol −1 . The activity of complex 4 increased with the addition of different alcohol co-initiators except in t -butanol where a reduction was obtained arguably due to steric hindrance.