Pentalene complexes ruthenium

Experiments with cyclooctatetraene and its methyl and phenyl derivatives have demonstrated that reaction with certain ruthenium carbonyl complexes can occur with transannular bonding to give pentalene complexes directly.253,264 The structures of these unique molecules have been confirmed by X-ray crystallography. 

Treatment of 5,8-bis(trimethylsilyl)cyclo-octa-l,3,6-triene or 3,5,8-tris(trimethyl-silyl)cyclo-octa-l,3,6-triene with triruthenium dodecacarbonyl gave the pentalene complexes (352 X = H or SiMe ). Tricarbonyl(Ti-cyclo-octa-l,5-diene)ruthenium and tricarbonyl(T)-cyclo-octa-l,3-diene)osmium have been prepared. They react with trityl fluoroborate to give cyclo-octadienylium complexes [(CgHn)M(CO)3] which react with anionic nucleophiles to give neutral compounds, some of which... 

Hafner succeeded in the synthesis of the unsubstituted pentalene complex 142 as early as 1973 by irradiation of a [2+2] dimer in the presence of Fe2(CO)9, and substituted complexes such as 143 were obtained by treatment of the respective dihydropentalenes with pentacarbonyliron [165, 166]. In a remarkable reaction, ruthenium complex 144 was obtained by treatment of 1,3,5,7-cyclooctatetraene with cis-Ru(CO)4(GeMe3)2 (Scheme 10.50) [167]. 

Gold chloride forms an unstable complex with cyclo-octatetraene at low temperatures. This decomposes at — 20°C to l,2-dichlorocyclo-octa-3,5,7-triene, which gradually cyclizes to (562). In an attempt to form pentalene-metal complexes, cyclo-octatetraene was reduced to a mixture of trienes and bicyclo [4,2,0] octadiene, which was then treated with substituent ruthenium carbonyls, affording a variety of complexes, including (563). °... 

Attempts to prepare the antiaromatic compound pentalene have so far failed. Various transition metal complexes of pentalene are, however, easily prepared [for example, ruthenium carbonyl complexes, Eq. (167) (Brookes et at., 1973)] so that pentalene might be generated in situ from such complexes and trapped with various reagents (Knox and Stone, 1974). 

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