1.3-Cyclopentadiene, chromium complex

C5H5.1,3-Cyclopentadiene, chromium complex, 29 247,251, 252 chromium, molybdenum, and tungsten complexes, 26 343, 28 148,196,197 cobalt complex, 26 191-197,309 cobalt and rhodium complexes, 28 280, 281... 

Aryl(dialkylamino)carbene chromium complexes do not yield aminonaphthols upon treatment with alkynes, but form indene derivatives. Vinyl(dialkylamino)car-bene complexes, however, react with alkynes to yield aminophenols as the main products if solvents of low nucleophilicity are used [335]. (2-Amino-1-vinyl)carbene complexes do not undergo benzannulation when treated with alkynes, but form cyclopentadienes or heterocycles instead [251]. 

The extensive organometallic chemistry of chromium, i.e. the hexacarbonyl and its derivatives, organochromium compounds without carbonyl ligands, cyanide and isocyanide complexes, alkene, allyl, diene, cyclopentadiene and arene derivatives, and complexes of a-donor carbon ligands, has been recorded in Chapters 26.1 and 26.2 of Volume 3 of Comprehensive Organometallic Chemistry .1 In the present section, chromium complexes... 

Acylmetallates lp,q generated by addition of lithio prop-2-ynylic ethers to hexacarbonyl chromium or tungsten afford oxacyclopenten-2-ylidene complexes 173 on contact with wet silica gel (Scheme 73).194 The chromium complex 173 (M = Cr) undergoes a condensation with tolane to give a 1,4-dioxy aromatic compound 174. Addition of cyclopentadiene to 173 (M = W) affords a Diels-Alder adduct 176 in a 1 3 exo/endo ratio,195 while addition of dimethylamine quite unexpectedly does not lead to production of an aminocarbene complex but to formation of 5,5 -diphenyl-2,2 -bifuran 175 (Scheme 73).196... 

The earliest studies examining the stereoselectivity of these reactions involved cyclopentadiene - and among the examples in the literature is the reaction of the isopropenyl chromium complex (48a). The reaction is nq>id and gives the endo and exo adducts (49) and (51), as well as the chelated complex... 

When the reactants are mixed in a 3 1 ratio, an intermediate (7) appearing to contain three o--cyclopentadienyl groups is formed at -80°C. Upon allowing the temperature to rise to -60°C, rearrangement occurs that yields ferrocene and a polymeric cyclopentadiene. The proposed mechanism for this reaction is similar to that proposed in the formulation of Hein s vr-arene chromium complex (2) (Fig. 7). 

Diels-Alder reaction with cyclopentadiene gave the corresponding adduct (Eq. 31) [28]. (Dihydronaphthalene)chromium complex gave addition product by reaction with diazomethane with high diastereoselectivity [29]. The acrylate having chiral arene chromium complex underwent Diels-Alder reaction with high selectivity in the presence of Lewis acid (Eq. 32) [30]. 

C10H15N, Benzenemethanamine, N,N,4-trimethyl-, lithium complex, 26 152 C10H15P, Phosphine, diethylphenyl-, nickel complex, 28 101 platinum complex, 28 135 CioHigAsi, Arsine, 1,2-phenylenebis(dimethyl-, gold complex, 26 89 nickel complex, 28 103 CioHie, 1,3-Cyclopentadiene, 1,2,3,4,5-pen-tamethyl-, 28 317 chromium complex, 27 69 cobalt complexes, 28 273, 275 iridium complex, 27 19 samarium complex, 27 155 titanium complex, 27 62 ytterbium complex, 27 148 CioH,gBrN04S, Bicyclo[2.2.1]heptane-7-methanesulfonate, 3-bromo-1,7-di-methyl-2-oxo-, U.IRHENDO, ANTPi]-, ammonium, 26 24... 

In a similar fashion, the intermediate chromium complex can react further to give a substituted cyclopentadiene in moderate yield (eq45) ... 

The simple cyclopropylmethoxycarbenechromium complex 142 reacts with alkynes to afford cyclopentenones 143 and 144 via the cyclopentadiene intermediate 145, which is hydrogenated with the aid of the chromium(O) residue and water (Scheme 31) [100-103]. Formation of 145 can be regarded as... 

The chromium tricarbonyl derivative 252 ° and the cyclopentadiene complexes 253 and 254 ° have been prepared. 

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