Neodymium monochloride and monoallyl complexes {2-[Ph2P(O)]C6H4NC(But)N(2,6-Me2C6H3)}2NdR (R = Cl, CH2CH=CH2) with the tridentate amidinate ligand in the catalysis of ring-opening polymerization of cyclic esters

Abstract

The reaction of tridentate amidine 2-[Ph2P(O)]C6H4NHC(But)=N(2,6-Me2C6H3) (1) containing the side-chain donor group Ph2P=O with NdCl[N(SiMe3)2]2 (2) in a molar ratio of2:1 afforded the neodymium bis(amidinate) monochloride complex {2-[Ph2P(O)]-C6H4NC(But)N(2,6-Me2C6H3)}2NdCl (3). The neodymium bis(amidinate) monoallyl complex {2-[Ph2P(O)]C6H4NC(But)N(2,6-Me2C6H3)}2Nd(C3H5) (5) was synthesized by the elimination reaction between the tris-allyl derivative Nd(C3H5)3-(C4H8O2)2 (4) and amidine 1 in a molar ratio of 1:2 and by the exchange reaction between equimolar amounts of complex 3 and allylmagnesium bromide (C3H5MgBr). Complex 5 exhibits high activity as an initiator for the ring-opening polymerization of rac-lactide and e-caprolactone, providing the conversion of up to 500 equivalents of the rac-lactide and e-caprolactone within 5 and 2 min, respectively. The resulting polylactide samples have high number-average molecular weights ((47.38–93.02) · 103) and low polydispersity indices (Mw/Mn = 1.18–1.47). The polycaprolactone samples are characterized by high number-average molecular weights ((114.34–237.46) · 103) and a somewhat broadened molecular weight distribution (Mw/Mn = 1.87–2.40).