Tropylium 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%... 

Cycloheptalnene complexes can be oxidized (hydride ion abstraction) to form cydoheptatrienyl (sometunes called tropylium) complexes 120... 

The reaction of methyl tropyl ether-iron tricarbonyl with acid yields a tropylium complex, in which the ring formally contains an uncoordinated double bond (188), but is actually an example of a fluxional molecule. 

Apart from the di- and oligoolefm iron tricarbonyl complexes, which nowadays are frequently used in organic synthesis [71, 72], the chemistry of the readily accessible cyclohepatriene chromium and molybdenum tricarbonyls 2 and 3 was the focus of intense research efforts as well. Only a few months after the synthesis of 2 and 3 was published [58,59], both Hyp Dauben and Peter Pauson reported that these compounds react with triphenylmethyl tetrafluoro-borate in methylene chloride to give the tropylium complexes 4 and 5 in excellent yield (Scheme 7.1) [73, 74]. Later this method of hydride abstraction was also used for the preparation of the tropylium cation itself and subsequently led to the generation of several cationic rc-complexes of iron, manganese and cobalt [71, 72], The reactions of the cations of 4 and 5 with nucleophilic... 

Triclinic crystal system, 75, 78 Trigonal bipyramidal (TBP) structure, 480-483 Trigonal crystal system, 75, 78 Trigonal hybrid, 150-153 Trigonal prism, 489-491 Trimethylborane, 205 Trinegative ions, 332-333 Trinuclear clusters, 813-815 Tropylium complexes, 683-684 Tutankhamen, 458 Twist angles, 490... 

The hydride ion abstraction reaction can be reversed by adding sodium borohydride to the w-tropylium complexes 109,110), e.g., [C7H7Cr(CO)3]+ + H C7HgCr(CO)3. Other anions react with the TT-tropylium-chromium... 

Flow n.m.r. and stopped-flow spectrophotometry have been applied to the reaction of the tropylium complex [M(CO)3(C7H7)]+ (M = Mo or W) with iodide and three intermediates eventually leading to the CO substitution product have been observed (Scheme 22). The initial attack is surprisingly at the metal in view... 

The stereospecificity, regioselectivity, and general mechanisms of nucleophilic addition to iri-tropylium complexes of the group VI metals have been... 

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