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

/pdf/cocatalysts-for-metal-catalyzed-olefin-polymerization-37a9jvjiei.pdf

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

Recent progress in the synthesis of benzene and 1,3-cyclohexadiene derivatives, and heterocyclic compounds such as pyridines, pyridones, pyrans, pyrimidine diones, etc, has been reviewed. The general mechanistic aspects of the [2+2+2] cycloaddition reaction are discussed. The asymmetric variants of these reactions are also discussed along with the proposed models of asymmetric induction.

http://web4.uwindsor.ca/users/j/jlichaa/reference.nsf/0/10ff8b04ff3a317885256d88005720f6/$file/asc-2006-348-2307 2+2+2.pdf

[2+2+2] Cycloaddition Reactions Catalyzed by Transition Metal Complexes

Publisher Summary The chemistry of metal–alkynyl compounds is developing at a rapid pace. The bonds of alkynyl ligands, like those of organic alkynes have been shown to participate in a rich set of chemical transformations. Electronic-absorption band maxima and extinction coefficients have been reported for a large number of metal–alkynyl complexes. Casual comparisons of electronic-absorption band energies or intensities among a series of compounds in the absence of such experiments are not without the risk of misinterpretation because a variety of important effects not associated with the presence or absence of M-CCR π-bonding may be operative such as mixings between electronic states of identical symmetry but different orbital character. The best and simplest means of placing the M–C bond distances of metal–alkyl complexes in a context that allows insight into whether or not they manifest M-CCR π-interactions is to compare them to M–C bond distances of complexes where such effects are expected to be insignificant, as for metal–alkynyl compounds.

The Bonding of Metal-Alkynyl Complexes

In this paper, the first examples of baseline separation of isomeric macromolecules by electrospray ionization/ion mobility spectrometry (ESI/IMS) at atmospheric pressure are presented. The behavior of a number of different isomeric peptides in the IMS was investigated using nitrogen as a drift gas. The IMS was coupled to a quadrupole mass spectrometer, which was used for identification and selective detection of the electrosprayed ions. The mobility data were used to determine their average collision cross sections. The gas-phase ions of isomeric peptides were found to have different collision cross sections. In all cases, doubly charged ions exhibited significantly (8-20%) larger collision cross sections than the respective singly charged species. The analysis of mixtures of the isomeric peptides clearly demonstrated the capability of IMS to separate gas-phase peptide ions due to small differences in their conformational structures, which cannot be determined by mass spectrometry. An actual resolving power of 80 was achieved for two doubly charged reversed sequenced pentapeptides. Baseline separation was provided for ions differing by only 2.5% in their measured collision cross sections; partial separation was shown for isomeric ions exhibiting differences as small as 1.1%.

Separation of isomeric peptides using electrospray ionization/high-resolution ion mobility spectrometry.

Publisher Summary This chapter focuses on supracyclopentadienyl derivatives in organometallic chemistry. Within organometallic chemistry—synthetic, analytical, physical, applied, and theoretical chemists are involved in research projects, dealing with highly substituted cyclopentadienylide (Cp)-metal complexes. Supra-Cp's are a major focus of this chapter, whereas for many others they are just a sideline where the bulkiness is a minor feature in the comparative study of certain phenomena. This chapter reveals unifying interest, sometimes with no cross-referencing to similar bulky Cp systems or even different metals carrying the same supra-Cp. The basic bulky Cp systems that are common in organometallic chemistry are discussed in the chapter, in their anionic form as ball-and-stick models with the hydrogens included. Other basic bulky Cp's described in the chapter are di(isobutyl)(tert-buty1)-Cp, penta(isopenty1)- Cp [isopentyl=( H,C2)2CH-], and tris(methoxycarbony1)-Cp. This chapter presents highly substituted Cp's, supracyclopentadienes that so far have escaped attention as ligands in organometallic complexes: tetra(terfbuty1)- Cp, 3,Mimethyl- and 3,5di-n-propyl- 1,2,4-triphenyl-Cp, and 1,2,3,5-tetraphenyl-4-p(7-cycloheptatrienyl)phenyl-Cp. Most of the bulky ring substituents are simple hydrocarbon moities, either alkyl or aryl groups, and consequently the supra-Cp's can be divided into two classes: peralkyl and peraryl systems. The use of bulky cyclopentadienes with functional group substituents causes problems in organometallic synthesis. Although there is a sizable number of Cp- metal complexes with only one functional group on the Carbon, ring examples for persubstituted systems are limited. This chapter also covers tetrasubstituted fulvalenes ethylene-bridged bis(tetrahydroindeny1) complexes and a dibornacyclopentadienyl ligand.

Bulky or Supracyclopentadienyl Derivatives in Organometallic Chemistry

rotation,I0 spectrophot~metry,~~~~-~~ circular dichroism,I5 fluorescen~e,’~ NMR,16 temperature jump,’*J7 and v i s c ~ m e t r y . ~ ~ J ~

Surreptitious involvement of a metallacycle substituent in metal-mediated alkyne cleavage chemistry

Le depart de l'ion chlorure du complexe (PPh 3 ) 2 Cl-iridacyclopenta-2,4-diene-2,3,4,5-tetracarboxylate de tetramethyle, en presence de CH 3 CN; AgBF 4 ; PMe 3 donne les complexes cationiques de type (PPh 3 ) 2 (L) (L') iridacyclopenta-2,4-diene-2,3,4,5-tetracarboxyle de tetramethyle, avec L=CO ou NCCH 3 ; L=H 2 O ou NCCH 3 . Ces complexes reagissent avec soit le but-3-yn-1-ol, soit le pent-4-yn-2-ol. On obtient des complexes cationiques metallocycliques-carbeniques. Le complexe cationique (CO) (PPh 3 ) 2 [1-(tetrahydro-2-urylidene) iridacyclopenta-2,4-diene-2,3,4,5-tetracarboxylate de tetramethyle] est etudie par diffraction RX

Synthesis, structure, and reactivity of metallacycle-carbene and -bis(carbene) complexes. A new intramolecular carbene-carbene coupling process

On the mechanism of a new metallacycle annelation reaction : evidence for an intramolecular methoxy group transfer

Le compose du titre cristallise dans le systeme monoclinique, groupe d'espace Cc et sa structure est affinee jusqu'a R=0,0311

The first stable metallacycle-carbene complexes: structural characterization of [cyclic] Ir(CR:CRCR:CR)(PPh3)2(CO)(:C(CH2)3O)+BF4-, R = CO2CH3

Oxidative coupling of cis-carbene ligands: synthesis, structure, and reactivity of an iridium(III) bis(oxacyclopentylidene) complex

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