Quinolyl‐Amidinates Chelating Bimetallic Magnesium and Mononuclear Aluminum Complexes for ϵ‐Caprolactone Polymerization

Abstract

AbstractA series of quinolyl‐amidinate compounds ((Ar–N=C(Ph)–N(H)–C9H5N–2–Me: Ar=2,6‐Me2C6H3 (L1), 2,6‐Et2C6H3 (L2), 2,6‐iPr2C6H3 (L3), 2,4,6‐Me3C6H2 (L4), 2,6‐Et2‐4‐MeC6H2 (L5)) was synthesized. These compounds in toluene reacted with C2H5MgBr forming the bimetallic bromomagnesium complexes (Mg1 ‐ Mg5) in high yields, and with AlMe3 producing dimethyl aluminum complexes (Al1 ‐ Al5) in high yields. All organic compounds and their corresponding magnesium and aluminum complexes were characterized by elemental and spectroscopic analyses. The ambiguous structures of complexes Mg2, Mg5 and Al1 were determined by the single crystal X‐ray diffraction analysis, reflecting bimetallic feature of complexes Mg2 and Mg5 with five‐coordination around magnesium atoms and mononuclear aluminum complex Al1 as a distorted trigonal‐bipyramidal geometry. All magnesium and aluminum complexes initiate the ring opening polymerization of ϵ‐caprolactone with good conversion yields. Aluminum complexes showed better activity with TOF up to 3678 h−1 at 80 °C in the presence of BnOH, while bromomagnesium complexes attained the good conversion of ϵ‐CL without of BnOH.