Living Polymerization of Carbodiimides Initiated by Copper(I) and Copper(II) Amidinate Complexes

Abstract

Various catalysts for the polymerization of carbodiimide have been investigated. In early studies, anionic polymerization techniques were employed, but the products obtained were low molecular weight oligomers. More recently, a living route using titanium(IV) complexes as initiators has been employed and the high molecular weight polymers obtained exhibit a well-ordered helical, extendedchain conformation. However, the titanium complexes are sensitive to high temperatures and the presence of oxygen or water. Herein, we report that more robust catalysts based on copper(I) and copper(II) complexes also initiate living carbodiimide polymerizations. The tolerance of these complexes to impurities is illustrated by the fact that they cleanly initiate the polymerization of carbodiimides under air and oxygen. They are even active in the presence of water, but both molecular weights and yields tend to be lower than in dry solvents. It has been shown that the catalytic activity of a copper(II) amidinato complex is almost equal that of reported titanium(IV) initiators. Analysis of these systems by gel permeation chromatography-light scattering measurements (GPC-LS) and preliminary kinetic analysis suggest this system to be living.

Reactivity of Ruthenium(II) and Copper(I) Complexes that Possess Anionic Heteroatomic Ligands: Synthetic Exploitation of Nucleophilicity and Basicity of Amido, Hydroxo, Alkoxo, and Aryloxo Ligands for the Activation of Substrates that Possess Polar Bonds as well as Nonpolar C–H and H–H Bonds

“…[27,28] These transformations are of potential relevance to transitionmetal-catalyzed polymerization of heterofunctionalized monomers such as carbodiimides, carbon dioxide, lactams, lactones, lactides, isocyanates, epoxides, and aziridines, [6,8,9,[113][114][115][116][117][118][119][120][121][122][123][124] catalytic hydration of nitriles, [125] catalytic transamidation and transesterification, [126][127][128][129][130][131][132][133][134][135] and related transformations.…”

“…In all cases the structures reveal approximately linear two-coordinate monomeric systems ( Figure 3). We have structurally characterized three Cu-NHPh complexes: 6 ], which is 1.444(4) Å. [23,30] Consistent with the solid-state structures that suggest a negligible Cu-N amido π-interaction for the Cu I anilido complexes 1-4, the calculated Kohn-Sham (KS) HOMO of these systems has little Cu character, and that which is pres ent is Cu 3d (p amido -d Cu π*) rather than 4p ( Figure 5).…”

“…[a] All reactions performed with 5 mol-% catalyst at room temperature in C 6 (Table 2 and Table 3). [37] In all examples studied the reactions are regioselective for the "anti-Markovnikov" product (Scheme 32).…”

Liquid Crystalline Properties of Polyguanidines

“…The same procedure for the preparation of N,N′-di-n-hexylcarbodiimide was employed. 27 The quantities of reagents used were 1.92 g of N-6-(4′-methoxybiphenyl-4-oxy)-hexyl-N′-n-hexylurea (4.50 mmol, 1 equiv), 1.48 g of triphenylphosphine (5.64 mmol, 1.25 equiv), 0.290 mL of bromine (0.900 g, 5.64 mmol, 1.25 equiv), 1.97 mL of triethylamine (1.43 g, 11.3 mmol, 2.5 equiv), and 55 mL of dichloromethane. The crude product from evaporation of n-pentane is recrystallized in warm acetonitrile to give white powder.…”

Transition Metal Catalyzed Reactions of Carbon Dioxide and Other Heterocumulenes

“…)[106] catalysts was developed in the same laboratories for the living polymerization of carbodiimides (Equation19). Helical polymers were obtained from both Scheme 3.…”