There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Late-metal catalysts for ethylene homo- and copolymerization.

B. Anionic Ligands 302 IX. Group 9 Catalysts 302 X. Group 10 Catalysts 303 A. Neutral Ligands 303 1. R-Diimine and Related Ligands 303 2. Other Neutral Nitrogen-Based Ligands 304 3. Chelating Phosphorus-Based Ligands 304 B. Monoanionic Ligands 305 1. [PO] Chelates 305 2. [NO] Chelates 306 3. Other Monoanionic Ligands 306 4. Carbon-Based Ligands 306 XI. Group 11 Catalysts 307 XII. Group 12 Catalysts 307 XIII. Group 13 Catalysts 307 XIV. Summary and Outlook 308 XV. Glossary 308 XVI. References 308

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Advances in non-metallocene olefin polymerization catalysis.

One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

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Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

Design strategies for water-soluble small molecular chromogenic and fluorogenic probes.

The dimethylaluminum compounds {3-tBu-2-(O)C6H3CH═N−R}AlMe2 [R = C6H5 (1); 2,6-iPr2C6H3 (2); C6F5 (3)] were used as initiators in the ring-opening polymerization (ROP) of e-caprolactone, l-lactide, and d,l-lactide. Compound 3, in combination with 1 equiv of methanol, exhibited a living behavior in the ROP of the cyclic esters. Such a feature allowed the preparation of poly(d,l-lactide-block-e-caprolactone) and poly(l-lactide-block-e-caprolactone) copolymers. Random copolymers of e-caprolactone and l-lactide and of e-caprolactone and d,l-lactide were also synthesized by compound 3. NMR and DSC characterization confirmed a highly random structure of these copolymers, even in the absence of transesterification reactions. All the materials, characterized by GPC, showed high molecular weight and narrow molecular weight distributions.

Claudio Pellecchia

Papers

Living Ring-Opening Homo- and Copolymerization of ε-Caprolactone and l- and d,l-Lactides by Dimethyl(salicylaldiminato)aluminum Compounds

.beta.-Hydrogen abstraction and regiospecific insertion in syndiotactic polymerization of styrene

Synthesis, crystal structure, and olefin polymerization activity of a zwitterionic .eta.6-arene zirconium tris(hydrocarbyl)

Synthesis of highly syndiotactic polystyrene with organometallic catalysts and monomer insertion

Base-free cationic mono(cyclopentadienyl)zirconium complexes: synthesis, structural characterization, and catalytic activity in olefin polymerization