Nucleophilic addition to organotransition metal cations containing unsaturated hydrocarbon ligands : A survey and interpretation

The chemistry of binuclear palladium(II) and platinum(II) complexes

Coordination chemistry of stibine and bismuthine ligands

Regio- and stereospecific carbon-carbon bond formation of η4-(trans-dienol)Fe(CO)3 complexes

Publisher Summary This chapter reviews the chemistry of complexes formed by the related acyclic pentadienyl group. η 1 -cyclopentadienyl groups are found both in main group derivatives and in transition metal complexes. The electron affinities of the pentadienyl and cyclopentadienyl radicals in the gas phase are 87 and 173 kJ mol –1 and the first ionization energies 752 and 839 kJ mol –1 , respectively. The metal can be bonded η 3 , which is usually favored for lithium or η 5 , which is adopted by the larger potassium ion. 13 C-nuclear magnetic resonance (NMR) spectra show that the negative charge in the pentadienylmetal derivatives of groups I, II, and III resides preferentially at the terminal and central positions. Allyl silanes and stannanes are established as useful reagents in organic synthesis. Electrophilic attack occurs at the terminal carbon atom of the allyl system, leading to allylic transposition in the product. The first binary pentadienyl complex of a transition element, bis (pentadienyl)-chromium, was obtained from PlNa and CrCl 2 . Pentadienyltricarbonyliron cations are readily attacked by nucleophiles. They are more reactive in this respect than the corresponding cyclic complexes. Cyclopentadienyltricarbonylmanganese (cymantrene) is extensively investigated. Typical reactions include photochemical substitution of carbonyl groups by other ligands and the electrophilic substitution of the cyclopentadienyl ring. Some unusual complexes that include pentadienyl or related ligands have been obtained from the reactions of alkynes with various transition-metal complexes.

Keith A. Holder

Papers

Electrophilic substitution of methoxybenzenes by pentadienyltricarbonyliron cations

4-substituted but-2-enylpalladium(II) complexes

Electrophilic Substitution of 1,3-Dimethoxybenzene By Pentadienyltricarbonyliron Cations