7 7-cycloheptatrienyl complexes

A growing body of work deals with CpV(cycloheptatrienyl) complexes and derivatives, which are formally V(0), if the cycloheptatrienyl (tropylium) ligand is considered to have a +1 charge [11-13]. The parent complex has a facile reversible oxidation (—0.17 V) in TlTF but it cannot... 

Cycloheptatrienes with chromium, 5, 337 in molybdenum carbonyls, 5, 480 tj7-Cycloheptatrienyl complexes, with tungsten carbonyls and isocyanides, 5, 693 Cycloheptatrienyl compounds actinide complexes, 4, 227 with actinides, 4, 226 lanthanide complexes, 4, 122... 

Three zirconium/cycloheptadienyne complexes (231a-c) have been prepared by /3-hydrogen elimination from a mixture of cycloheptatrienyl complexes 269-271 (Scheme 33) and have been used as intermediates for the preparation of a zirconaazulene.87 The alkyne complexes are formed to the exclusion of the allene isomer 268. This is believed to be due to the proximity of the /3-vinyl hydrogen that is a result of both the shorter double bond and its forced coplanarity with the metal. Allene formation from 269 might be induced by blocking the vinyl position (see Sections IV,B and IV,C), but this has not been tested. 

Only one cycloheptatrienyl complex of the lanthanides is known nntil now. Reaction of Nd(BH4)3(THF)2 with K(C7H9) yields (THF)(BH4)2Nd(/x-) ) -C7H7)Nd (BH4)(THF)3 (Fignre 76). The X-ray stmcture determination shows a uniqne reverse-sandwich stmctnre with both Nd atoms r coordinated to the planar ligand. 

The complex (tetraphenylcyclobutadiene)iododicarbonylcobalt reacts upon heating with 1,3,5-cycloheptatriene to give the cation [(1,3,5-cycloheptatriene)(tetraphenylcyclobutadiene)Co]+, isolated as the I , PFg , or [Co(NCS)4] salts (184). This cation is also very susceptible to nucleophilic attack to yield the 7T-cycloheptatrienyl complex. 

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 . 

Cycloheptatrienyl Complexes. There are a number of cases in which cycloheptatrienyl rings are bound in trihapto fashion, i.e. use an allyllic portion of the ring. In the three cases (23-XXXIV), (23-XXXV) and (23-XXXVI)... 

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