Tropylium metal complexes

J. D. Munro, andP. L. Pauson, Cycloheptatriene-and Tropylium-Metal Complexes. Part... 

B. Other Cycloheptatriene-Metal and Tropylium-Metal Complexes 360... 

In an improved process for the synthesis of tropilidene (5) by E. Muller, a solution of diazomethane in benzene is added gradually to refluxing benzene containing cuprous bromide as catalyst. Benzene is used in large excess, and the product is isolated most easily by filtering the solution from the catalyst and adding it to a solution of phosphorus pentachloride in carbon tetrachloride. The tropylium chloride which separates is dissolved in water and treated with perchloric acid to afford tropylium perchlorate in 85% yield. The success of the method is attributed to formation of the intermediate (3), a deactivated electrophilic carbon metal complex. Tropilidene... 

A plethora of electron-deficient arenes can enter the VNS reaction carbocyclic and heterocyclic aromatic compounds activated by the nitro group and arenes that are active electrophiles due to their electronic configuration, such as azulene [35, 36], electron-deficient annulenes [37], tropylium cation [38], and particularly azines and azinium cations. Interestingly, q -transition metal complexes of arenes, such as benzene tricarbonylchromium, do not enter the VNS reactions. Although the addition of carbanions to these electron-deficient rings proceeds efficiently, and these adducts can be oxidized to form the products of ONSH, the p-elimination of HCl from the o adducts of a-halocarbanions does not occur [39, 40]. 

An attempted Friedel-Crafts acylation of (7t-C5H5)(C6H6)M (M = Cr, Mn) resulted in expansion of the benzene ring to give the (7t-tropylium)-(jt-cyclopentadienyl) metal complexes, equation (6-40). 

Unsubstituted butatriene is unstable at 0°, but the complex decomposes only above 230° under nitrogen. Allyl and tropylium ions were also trapped as metal complexes ([6-50], and [6-51]). 0-Quinodimethene iron carbonyl complex also serves as the metal-stabilized active intermediate [6-52]. 

The Institute of Organoelement Compounds of the USSR AS (INEOS) was founded by A.N. Nesmeyanov (1899-1980, the president of the USSR Academy of Sciences from 1951 to 1961 and director of the INEOS AN from 1954 to 1980). The work on EKhOS was conducted in several directions. The polarographic behavior of the tropylium cation [53] was first investigated here in 1957. Active studies of non-benzoid aromatic compounds were started in the laboratory of D.N. Kursanov, corresponding member of the USSR Academy of Sciences, after Mark Efimovich Vol pin has joined the laboratory. In coimection with research on the catalysis by metal complexes (VoPpin s pioneering work on fixation of nitrogen... 

Magnetization transfer was used to detect fluxionality in the bimetallic complex 347 (Scheme 45).138 Both metals move in this case, and the reaction occurs at a considerably lower temperature than is required for 343. An intramolecular mechanism via an achiral intermediate (or transition state) as pictured in 358 was proposed based on selective isotopomer irradiation as described for 343. Stronger bonding of the Mo(CO)3 moiety to the tropylium ion in the transition state than to the distorted cycloheptatriene... 

Complexes of cycloheptatriene (CtHs) and the tropylium cation (C7H7)+ are also known and their chemistry mirrors that of the smaller polyene-containing systems, namely, metal-centered ligand exchange reactions and ligand-centered nucleophilic attack. A detailed review of this chemistry is available. ... 

In Chapter 8 we described how metal carbides (first mentioned in Section 6-1-4) could serve as precursors to carbyne complexes by way of electrophilic addition. Scheme 10.8 revisits a portion of Scheme 8.12, showing Os-carbide complex 72—with its nucleophilic Ccarbide atom—reacting with methyl triflate or tropylium ion to give alkylidynes 73 and 74, respectively. Comparable reactions occur with the corresponding Ru-carbide complex.87 This method may become more general after the synthesis of additional carbide complexes occurs. 

The tropylium ion, C7H7+, is an aromatic six-ir electron system (44) which would be expected to form it complexes with transition metals analogous to... 

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