Cyclo-octa-l,3,5-trienes

One case of some interest for which kinetic data are not available, but for which equilibrium data are, is that of cyclo-octa-l,3,5-triene. At 100° there is a rapid equilibration between the triene and bicyclo[4,2,0] octadiene ... 

Polymeric-ruthenium catalysts have been prepared by the reaction of ( / -cyclo-octa-l,3,5-triene) (// -cycloocta-1,5-diene) ruthenium(0), (// -cydoocta-l,3,5-triene) (COT) (// -cycloocta-1,5-diene) (COD) with polystyrene in hydrogen at room temperature [258]. Elemental analysis, IR and mass-spectrometry data show that in these polymer-metal complexes, two cycloolefin ligands, present in the starting Ru(COT)(COD) complex, are substituted by two phenyl rings of polystyrene ... 

Dibromo-3,3,6,6-tetramethylcycloheptanone reacts with potassium t-butoxide in THF to give the stable cyclopropenone (238). 2,3-Homotropone has been prepared from cyclo-octa-l,3,5-triene by bromination to give 1,6-dibromocyclo-octa-2,4-diene, oxidation to 6-bromocyclo-octa-2,4-diene-1-one, and cyclization. ... 

Epoxy-cyclo-octa-l,3,5-triene reacts with ethynylmagnesium bromides to give ethynylcycloheptatrienyl carbinols (239) which were converted by thionyl chloride into enynes (240). ... 

The n.m.r. spectra of cis,cis,cis-cyclo-octa-l,3,5-triene at low temperatures is consistent with a process that interconverts a chiral twist-boat conformer with its... 

Z,Z,Z)-Cyclo-octa-l,3,5-triene reacts with SO2 to give 9-thiabicyclo[4,2,l]nona-2,7-diene dioxide which was converted into 9-thiabicyclo[4,2,l]nona-2,4-diene dioxide. Thermal expulsion of SO2 had a free energy of activation lOkcalmol" greater for the latter dioxide than for the former dioxide so showing that linear extrusion of SO2 is favoured over non-linear extrusion or sequential bond cleavage. Photolysis of 1,2,5,6-tetramethylenecyclo-octane gave a mixture of the [3,3,2] propellane (230) and the tricyclodiene (74). ... 

Ru(dppm)(n -cyclooctenyl)Cp] is formed the latter complex exists as two isomers due to restricted rotation about the Ru-cyclooctenyl bond. Treatment of [RuH n-cod)CpJ with CCl gives [RuCKn-codlCpl which is a precursor to [RuClLgCp] (L=phosphine, L2=diene), [RuL CpHPFgl (L=C0, L2=n -polyalkene) and cyclic ally complexes such as (14). Reaction of [RuCl(n-cod)Cp] with excess [NH ][PFg] yields [Ru(n -cyclo-octa-l,3,5-triene)CpJlPFgl via the crystallographically characterised intermediate (15). ... 

The dienone (187) has been shown to be the product of thermodynamic control, and not merely an unstable precursor of other products, in the reaction of cycloheptatriene with chlorosulphonyl isocyanate. Cyclo-octa-l,3,5-triene reacts similarly to give (188), together with a trace of the 1,2-adduct at the terminal olefin. ... 

The reaction of cyclo-octatetraene dianion with a variety of esters and anhydrides is reported with ethyl oxalate at — 60°C the tetraene (287) is obtained, via 7,8-disubstituted cyclo-octa-l,3,5-triene, whereas with ethyl acetate the product is (288). ... 

Cyclo-octa-l,3>5-trienes fused to other rings exist entirely in the form (316) when n = 2, but as n is increased the bicyclic form (317) is also observed. ... 

By complexation with diene- or triene-seeking metal carbonyls, products of each form may be selectively sequestered. An n.m.r. study of the protonation of cyclo-octa-l,3,5-triene is reported. ... 

It may be noted that even in the case of conjugated olefins, the number of available electrons on an olefin by no means solely dictates the stoicheio-metry of the olefin-metal product. Thus the reactions on pp. 9, 10 show butadiene acting as a 2- and 4-electron ligand towards iron, and cyclo-octa-l,3,5-triene may act as a 4- or 6-electron ligand [35], e.g.. 

A number of binuclear complexes of stoicheiometry olefin Fe2(CO)6 (where olefin = cycloheptatriene, cyclo-octa-l,3,5-triene or cyclo-octa-tetraene) have each been shown by Mdssbauer studies to have equivalent iron atoms [87]. On the basis of this evidence it is proposed that in all cases the olefins bond to each iron by a r-enyl s tem (see 2.26). For example. 

Treatment of chromium hexacarbonyl with cyclo-octa-l,3,5-triene gives the deep red complex CsHioCr(CO)3 [95]. X-Ray analysis shows the structure, 5.11 [96] in which six of the carbons are within 2-24-2-28 A of the chromium atom and may be assumed to bond to it, the remaining two carbon atoms are further away (/ 3-l A). The bond lengths of the six-bonded carbons show distinct alternate single and double bond character. 

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