Dienyl complexes properties

The properties of the 7-norbornyl (18), 7-nobomenyl (19), and 7-norboma-dienyl (20) ions and radicals have aroused much interest in view of the evidence that the cations 19 and 20 have nonclassical -complex structures. We... 

Other complexes synthesized which also exist in solution as interconverting isomers were (dienyl)2M2(CO)4 x(CNR) (M = Fe, Ru x = 1, 2 dienyl = Cp, C5H4Me R = alkyl, aryl) (191 -195) and the isomer distribution from these series was found to be related to the electron withdrawing properties of R (increase in electronegativity favors bridging) and the bulk of R (increase in size favors terminal bonding) (194). 

Removal of the 0-substituted Fp group can be achieved by conversion into the cationic alkene-Fp complex using Ph3CPF6 and subsequent treatment with iodide, bromide or acetonitrile. Oxidative cleavage with ceric ammonium nitrate in methanol provides the methyl esters via carbon monoxide insertion followed by demetallation. The [3 + 2]-cydoaddition has been successfully applied to the synthesis of hydroazulenes (Scheme 1.11) [34]. This remarkable reaction takes advantage of the specific nucleophilic and electrophilic properties of V-allyl-, cationic t 5-dienyl-, cationic ri2-alkene- and ti4-diene-iron complexes, respectively. 

The molecular structure of decabenzylferrocene also helped to explain the rather low solubility of this compound in toluene or benzene, in sharp contrast with the previously found excellent solubility properties of other decabenzylmetallocenes and the pentabenzyl-Cp thallium and indium complexes in these solvents. The steric crowding of the benzyl groups in the ferrocene and their limited mobility leave little space for the solvent arene molecules to interact and subsequently to dissolve the molecule. This is quite similar to the situation encountered in the pentaphenylcyclopenta-dienyl derivatives with their closely packed phenyl rings (see Fig. 3). 

Co, Rh and Ir - The synthesis, properties and reactions of (T]5-bicyclo[3.2.01hcpta-l,3-dienyl)(il -COD)cobalt(I) have been reported, including the X-ray crystal structure of the tetraphenylcyclobutadiene complex, (17), the product of its reaction with diphenylethyne. The reaction of [(Ti5-C5H4R)Co( n -COD)] with 1,6-cyclodecadiyne afforded the (q. C5H4R)cobalt-capped cyclobutadiene superphane. The yield of the reaction was reported to vary with the substituent R. 

Unfortunately almost all other information on the nature and structure of lanthanoid arene complexes is based on indirect data. The exception is the recently obtained unusual complex with Yb-naphthalene-V grouping [68] and the mixed cyclopenta-dienyl/naphthalene complex of lutetium [69]. Their properties and X-ray data are discussed below. 

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