Carbene complexes gives

When a 30% solution in hexane is refluxed in a Soxhlet apparatus through a fixed bed of Re207/Al2C>3, preferably pre-treated with Me4Sn, a 68% yield of cyclic dimers is obtained, the proportions being close to the equilibrium values tt 88%, tc 9%, cc 3%272 273. Metal carbene complexes give 20-50% cis polymers120,271,347. 

Transition-metal carbene complexes undergo insertion reactions with C-H compounds. For example, under the action of PF or HCl, the rhodium cyclopen-tadienyl carbene complex gives the products of an migratory insertion of the CPh unit into an Ar/j -C-Hbond of the cyclopentadienyl ring [64] ... 

The ROMP of 1,7,7-trimethylnorbomene initiated by a molybdenum carbene complex gives an -trans, all-HT polymer, which is necessarily isotactic when made from a single enantiomer. It is atactic when made from racemic monomer... 

Bis(alkylthio)-3H-l,2-dithiole-3-thiones 167 can be transformed to 2,4-di-methylidene-l,3-dithietanes 168 on treatment with trialkyl phosphites [93,94] or triphenylphosphine [82]. For example, the bis(dithiacrownether) derivatives 169 have been synthesized by this reaction [93]. The reaction of 5-(alkylthio)-3ff-l,2-dithiole-3-thiones with Fischer carbene complexes gives 6-(alkylthio)-3ff-l,2-dithiine-3-thione complexes with Cr and W [95]. 

The thermolysis of amino-substituted carbene complexes gives high yields of imines (Fischer and Leupold, 1972 Connor and Rose, 1972). 

The comparison with ketenes is made because, for example, the photochemical reaction to give j9-lactams via chromium carbene complexes gives product distributions that closely parallel those obtained using ketenes generated using acid chloride. ... 

Aryl and alkenyl chromium carbene complexes react with HCaC(CH2)3CH=CHCH=CHR (R = C02Et, CH=CHC02Et) by insertion of carbon monoxide to give hydroquinones. Aryl molybdenum carbene complexes give hexahydroazulenes while alkenyl substituted molybdenum complexes generate hydroquinones or cyclopentadiene derivatives. ... 

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