Cyclopentadienyl compounds radical

Formation of the second aromatic ring in naphtalene is thought to occur by two subsequent additions of acetylene to a phenyl radical (CgHs) or directly by recombination of two cyclopentadienyl (C5H5) radicals, in both cases followed by hydrogen elimination. A three-ring compound can be formed in a similar way, by subsequent additions of acetylene to the naphtyl radical, or by an indenyl radical reacting with the cyclopentadienyl radical. 

While structural evidence indicates that radical 44 is delocalized through the five carbon centers, it has been suggested that annelation of the cyclopentadienyl framework with rigid bicyclic systems leads to localized structures, as in compound 45 (Fig. 7.20). The X-ray structure of 45 indicates that the rather long distances between C1-C2 (1.445 A), C1-C5 (1.442 A), and C3-C4 (1.482 A) correspond to... 

The cyclopentadienyl radical is well established by ESR spectroscopy while the fate of the Sn(I) radical is uncertain183). It should nevertheless be noted that no Sn(III) radical is formed, proving again the difference between cyclopentadienylstannylenes and other molecular tin(II) compounds. 

Matsue et al. [43] attempted to study the molecular rocket reaction in a ruthenocene-/ -cyclodextrin inclusion compound using the I00Ru y, p) "raTc reaction. They noticed a parallel relationship between chemical processes and nuclear-recoil-induced processes in the non-included ruthenocene compound, as shown in Fig. 9. In the nuclear-recoil-induced processes no dimerization can be observed because of the extremely low concentration of the product, whereas in the chemical processes dimerization is possible, as demonstrated by Apostolidis et al. [48]. When ruthenocene included in /J-cyclodextrin is irradiated with y-rays, a part of the ruthenocene molecule is converted to [TcCp2-] which escapes from the jS-cyclodextrin cavity. The [TcCp2] rocket thus produced can attack neighboring inclusion compounds so as to extract the enclosed ruthenocene molecules and abstract H or Cp (Cp cyclopentadienyl radical). This process is shown schematically in Fig. 10. 

Electronic absorption spectra of fc-benzenechromium (I) iodide (5) and its derivatives have been recorded and discussed by Yamada et al.26,26 They noted a loss of the benzene rings aromaticity in these compounds with the n electrons being drawn toward the metal and thereby conferring more a cyclopentadienyl radical character on the rings. 

Fluxional and Nonrigid Behavior of Transition Metal Organometallic ir-Complexes, 16, 211 Free Radicals in Organometallic Chemistry, 14, 345 Functionally Substituted Cyclopentadienyl Metal Compounds, 21,1... 

Compounds with a cyclopentadienyl-silicon cr-bond adopt a variety of bonding arrangements, which can be classified on the basis of the hybridization of the corresponding cyclopentadienyl carbon atom, as displayed in Scheme 1. In species of type 1, the silicon atom is bound to an sp3 -hybridized carbon atom, i.e. to an ally lie carbon within a cyclopentadiene unit. The silicon atom is bound to an sp2-hybridized carbon atom in species of type 2-6, including silylcyclopentadienyl radicals (2), ionic silylcyclopentadi-enide species (3), and silylcyclopentadienyl fragments bound in a /j5 -fashion to a metal centre (4). Species 5 represents the ionic resonance structure of a silafulvene, and structure 6 stands for the vinylic isomers of a cr-cyclopentadienylsilane (type 1), but these two types of compound are not examined in detail in this article. 

Alkenylboron compounds cyclopropanations, 9, 181 haloetherification, 9, 182 hydrogenation and epoxidation, 9, 182 metal-catalyzed reactions, 9, 183 metallic reagent additions, 9, 182 via radical addition reactions, 9, 183 5-Alkenylboron compounds, cross-coupling reactions, 9, 208 Alkenyl complexes with cobalt, 7, 51 with copper, 2, 160, 2, 174 with Cp Re(CO) (alkene)3 , 5, 915-916 with dicarbonyl(cyclopentadienyl)hydridoirons, 6, 175 with gold, 2, 255... 

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