Cycloheptatriene, complex

Treatment of cycloheptatriene complexes of the type [M(tj -C7H8)(CO)3] (M = Cr, Mo, W) with Ph3C" "BF4 results in hydride abstraction to give orange-coloured tj -cycloheptatrienyl (or tropy-lium) complexes ... 

It was originally reported (92, 174) that the cycloheptatriene complex [Fe(CO)3(C7H8)] with triphenylmethyl fluoroborate gave a tropylium complex [Fe(CO)3(C7H7)] BF4 but subsequent work (59) has shown that an adduct [Fe(CO)3(CvH8CPh3)] BF4 (XIV R = CPh3) is formed in 96%... 

The cycloheptatriene complex undergoes cycloadditions with various unsaturated bonds, such as monoenes, dienes and alkynes, under mild conditions to afford interesting polycyclic compounds. In particular, the intramolecular version offers efficient methods for the construction of strained polycyclic skeletons, which are difficult to synthesize by other means [72]. 

Thus [6+2] cycloaddition of alkene with complex 306, bearing an optically active side chain, under irradiation at room temperature afforded the bicyclic compound 307 in 98% de [73]. According to the Woodward-Hoffmann rule, the [6+2] cycloaddition proceeds by irradiation, and is thermally forbidden. However, the cycloheptatriene complex 308 underwent 1,5-hydride shift, followed by [6+2] cycloaddition by heating, to give the tricyclic compound 309 in 90% yield [74], The cycloaddition was applied to the synthesis of /f-cedrene [75]. 

The mass spectrum of cycloheptatrienetungsten tricarbonyl C7H8W (CO)3 (119) is very similar to that of the toluene analog, the only differences being that the cycloheptatriene complex exhibited the ions C6H6+ and C4H4+, which are not present in significant quantities in the spectrum of... 

M. A. Bennett, L. Pratt, and G. Wilkinson, Proton Resonance Spectra of Cycloheptatriene Complexes of Group YI Metals, J. Chem. Soc. 1961, 2037-2044. 

At present, there are only NMR data available for 7r-arene and TT-cycloheptatriene complexes of chromium, molybdenum, and tungsten (80,158,161) (see Table XXV). The chemical shifts of the complexed... 

C7H7)Fe.,(CO)6]+, obtained by reaction of the cycloheptatriene complex with trityl tetrafluoroborate, shows in solution a rapid valence tautomerisrn involving diene bonding to an iron atom and Tr-allylic bonding to the other. 

Although Able et al. (2, 8) had originally set out to prepare 7r-cyclo-heptatrienyl complexes of metals, the cycloheptatriene complexes they actually obtained served as key intermediates in forming the former complexes. In 1958 Dauben and Honnen (61) reported that cycloheptatriene-molybdenum tricarbonyl reacted with triphenylmethyl tetrafluoroborate in methylene chloride solution with abstraction of hydride ion from the molybdenum complex. The reaction products, obtained in nearly quantitative yields, were triphenylmethane and the 7r-cycloheptatrienyl complex [(7r-C7H7)Mo(CO)3]+BF4 . 

Hexahapto cycloheptatriene complexes (t)6-C7H8) can be treated with Ph3C+BF4 to abstract a hydrogen and yield the t)7-C7H7 ligand. A well-studied example is the synthesis of [(ti7-C7H7)Mo(CO)3]+, as shown below. 

If the organic group is not cyclically conjugated, the spectra appear more complex 132) as the d-band shows structure and there is no longer degeneracy among the ligand 77-orbitals. For the 7 6-cycloheptatriene complexes two d-bands are observed,... 

Cycloheptatriene complexes can be oxidized (hydride ion abstraction) to form cycloheptatrienyl (sometimes called tropylium) complexes 120... 

Normal reaction, forming 7-substituted cycloheptatriene complexes... 

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