Aqueous Phase Separation Behavior of Highly Syndiotactic, High Molecular Weight Polymers with Densely Packed Hydroxy-Containing Side Groups

Herein we describe the Rh-catalyzed C1 polymerization of silyl-protected diazoacetates of the general formula HC(=N₂)C(=O)O(CH₂) _x OSiR₃, where x = 2-5. After polymerization and subsequent desilylation, syndiotactic polymers bearing a hydroxy-containing side group on every backbone carbon are obtained. The molecular weight of the desired polymers can be controlled via chain transfer with methanol during the polymerization. The produced polymers are compared to atactic analogues formed by [(η³-C₃H₅)PdCl]-catalyzed polymerization of silyl-protected diazoacetates with the same general formula. While the polymers produced by the Rh and Pd catalysts have the same hydrophilic/hydrophobic balance, the stereoregularity of the polymers formed by the Rh catalyst was found to be of influence on the thermoresponsive behavior of the polymer. The effect of this stereoregularity on the thermoresponsive phase separation behavior of the produced polymers in aqueous solution was investigated.

Migratory Insertion of Carbenes into Au(III)-C Bonds

Migratory insertion of carbon-based species into transition-metal-carbon bonds is a mechanistic manifold of vast significance: it underlies the Fischer-Tropsch process, Mizoroki-Heck reaction, Ziegler-Natta and analogous late-transition-metal-catalyzed olefin polymerizations, and a number of carbonylative methods for the synthesis of ketones and esters, among others. Although this type of reactivity is well-precedented for most transition metals, gold constitutes a notable exception, with virtually no well-characterized examples known to date. Yet, the complementary reactivity of gold to numerous other transition metals would offer new synthetic opportunities for migratory insertion of carbon-based species into gold-carbon bonds. Here we report the discovery of well-defined Au(III) complexes that participate in rapid migratory insertion of carbenes derived from silyl- or carbonyl-stabilized diazoalkanes into Au-C bonds at temperatures ≥ -40 °C. Through a combined theoretical and experimental approach, key kinetic, thermodynamic, and structural details of this reaction manifold were elucidated. This study paves the way for homogeneous gold-catalyzed processes incorporating carbene migratory insertion steps.

Polymerization of alkyl diazoacetates initiated by the amidinate/Pd system: efficient synthesis of high molecular weight poly(alkoxycarbonylmethylene)s with moderate stereoregularity

The initiating ability of a new system, amidinate/Pd, for the polymerization of diazoacetates is described.

Copolymerization of alkyl diazoacetates with α,β-unsaturated aldehydes: synthesis and application

Copolymerization of alkyl diazoacetates with α,β-unsaturated aldehydes and the product's fluorescence property.

Polymeric palladium-mediated carbene polymerization

A newly-developed metal-carbene radical polymerization mechanism is proposed for poly(imidazole-Pd)-mediated carbene polymerization, which could produce stereoregular polycarbenes besides atactic polycarbenes.

Pd-initiated controlled polymerization of diazoacetates with a bulky substituent: synthesis of well-defined homopolymers and block copolymers with narrow molecular weight distribution from cyclophosphazene-containing diazoacetates

Pd-initiated polymerization of cyclophosphazene-containing diazoacetates proceeded in a controlled manner.