Publisher Summary This chapter discusses the chemistry of cationic dicyclopentadienyl group 4 metal–alkyl complexes. Neutral, d 0 group 4 metal alkyl complexes of general form Cp 2 M(R) 2 (R = H, hydrocarbyl) or Cp 2 M(R)(X) (X = anionic, two–electron donor) comprise the most extensively studied class of group 4 organometallics (I). For many years, it has been suspected that cationic d 0 metal–alkyl species Cp 2 M(R) + are involved in metallocene-based Ziegler–Natta olefin polymerization catalyst systems of the general type Cp 2 MX 2 /AIR n X 3 – n . Several key advances in the early 1980s generated renewed interest in the proposal that Cp 2 M(R) + ions are active species in the soluble catalyst systems. A simple but key point in the development of this chemistry was the realization that noncoordinating, nonreactive counterions, such as BPh 4 – are required for the isolation of stable salts. In 1976, Kaminsky reported the isolation of [(C 5 H 5 ) 2 Zr(CH 2 C(H)– (AIEt 2 ) 2 )][C 5 H 5 ] from the reaction of (C 5 H 5 ) 4 Zr and AIEt 3 . Cationic Cp 2 M(R)(L) + complexes exhibit a variety of interesting structural features, which result from the high Lewis acidity of the cationic d 0 metal centers. The tetrahydrofuran (THF) ligands in these complexes are labile and generally undergo rapid (nuclear magnetic resonance (NMR) time scale) exchange with free THF by dissociative or associative mechanisms at ambient temperature. Cationic, d 0 Cp 2 M(R)(L) + and base-free Cp 2 M(R) + complexes are easily prepared from readily available Cp 2 M(R) 2 compounds. There is strong evidence that Cp 2 M(R) + ions are the active species in Cp 2 MX 2 -based Ziegler–Natta olefin polymerization catalysts.

Chemistry of Cationic Dicyclopentadienyl Group 4 Metal-Alky I Complexes

Oxidative-addition reactions of transition metal complexes

Controlled carbometalation as a new tool for carbon-carbon bond formation and its application to cyclization

Publisher Summary This chapter discusses the binding and activation of carbon monoxide, carbon dioxide, and nitric oxide by transition-metal complexes and examines the selected reactions of these molecules, which are catalyzed by metal complexes in solution. These three simple oxides exhibit significantly different coordination chemistries and diverse reactivity patterns when bonded to transition-metal ions. The activation of each, thus poses different problems in the field of homogeneous catalysis. By considering these three simple inorganic oxides together, the chapter compares the similarities and differences apart from examining each independently. Homogeneously catalyzed reactions can be viewed as occurring in a sequence of steps, each of which involves a change in one or more of the following properties of the catalyst metal complex: coordination number, metal-ion oxidation state, and valence-electron count. Of these properties, the metal ion oxidation state seems most susceptible to confusion, especially with ligands, such as nitrosyl, π-bonded allyl, and bridging hydride.

The Binding and Activation of Carbon Monoxide, Carbon Dioxide, and Nitric Oxide and Their Homogeneously Catalyzed Reactions

Organoplatinum chemistry. Significance of metal-induced carbonium ions

Transition metal catalysis exemplified by some rhodium-promoted reactions of olefins

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Transition metal catalysis exemplified by some rhodium-promoted reactions of olefins