Current status and future perspectives in atom transfer radical polymerization (ATRP) are presented. Special emphasis is placed on mechanistic understanding of ATRP, recent synthetic and process development, and new controlled polymer architectures enabled by ATRP. New hybrid materials based on organic/inorganic systems and natural/synthetic polymers are presented. Some current and forthcoming applications are described.

Atom Transfer Radical Polymerization (ATRP): Current Status and Future Perspectives

Which electrophiles react with which nucleophiles? The correlation log k20 °C = s(E + N), in which electrophiles (carbocations, metal-π-complexes, diazonium ions) are characterized by one (E) and nucleophiles are characterized by two parameters (N, s), proved to be applicable for a wide variety of electrophile−nucleophile combinations. Since the introduction of this correlation in 1994 (Angew. Chem., Int. Ed. Engl. 1994, 33, 938−957), numerous new reagents have been characterized, and in 2001 (J. Am. Chem. Soc. 2001, 123, 9500−9512), a new method of parametrization was proposed that facilitates a continuous extension of the data sets without the need for reparametrization of existing data. This Account adjusts the N and s parameters of all presently characterized π-nucleophiles (arenes, alkenes, organometallics) to the new parametrization and illustrates how to employ the resulting reactivity scales for analyzing synthetic and mechanistic problems in organic and macromolecular chemistry. Predictions of ab...

π-Nucleophilicity in Carbon−Carbon Bond-Forming Reactions

Twenty-three diarylcarbenium ions and 38 π-systems (arenes, alkenes, allyl silanes and stannanes, silyl enol ethers, silyl ketene acetals, and enamines) have been defined as basis sets for establishing general reactivity scales for electrophiles and nucleophiles. The rate constants of 209 combinations of these benzhydrylium ions and π-nucleophiles, 85 of which are first presented in this article, have been subjected to a correlation analysis to determine the electrophilicity parameters E and the nucleophilicity parameters N and s as defined by the equation log k(20 °C) = s(N + E) (Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938−957). Though the reactivity scales thus obtained cover more than 16 orders of magnitude, the individual rate constants are reproduced with a standard deviation of a factor of 1.19 (Table 1). It is shown that the reactivity parameters thus derived from the reactions of diarylcarbenium ions with π-nucleophiles (Figure 3) are also suitable for characterizing the nucleoph...

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles

Update 1 of: Electrophilicity Index

Direct Nucleophilic SN1‐Type Reactions of Alcohols

The kinetics of the reactions of dicobalt-coordinated propargyl cations with π-nucleophiles (e.g., allylsilanes) and hydride donors (e.g., trialkylsilanes) have been studied conductometrically and/or photometrically. The reactions follow second-order kinetics with rate-determining CC-bond formation or hydride transfer. It is found that phenyl and trimethylsilyl substituents in the propargyl cation moiety reduce the electrophilic reactivities of these cations by less than a factor of 10. The electrophilicity is reduced by a factor of more than 105, however, when one CO ligand is replaced by PPh3 (3a → 3e). The reactions of the dicobalt-coordinated propargyl cations with allylsilanes and -stannanes, silylated enol ethers and ketene actetals, and hydride donors (R3SiH, R3SnH) follow the linear free enthalpy relationship log k = s(E + N), which allows one to calculate electrophilicity parameters E for these carbocations and to rationalize their synthetic potential.

How Electrophilic Are Cobalt Carbonyl Stabilized Propargylium Ions

Linear free enthalpy relationships : a powerful tool for the design of organic and organometallic synthesis

Which nucleophiles are capable of attacking the allyl ligand of the Pd-stabilized allyl cation 1? This question is answered by the electrophilicity parameter of 1 which is derived from kinetic investigations.

Oliver Kuhn

Papers

How Electrophilic Are Cobalt Carbonyl Stabilized Propargylium Ions

Linear free enthalpy relationships : a powerful tool for the design of organic and organometallic synthesis

Kinetics and Mechanisms of the Reactions of π-Allylpalladium Complexes with Nucleophiles.

Reactions of Carbon Electrophiles with Cobalt-Coordinated Enynes: Scope and Limitations

Kinetik und Mechanismen der Reaktionen von π‐Allylpalladiumkomplexen mit Nucleophilen