Cyclo-octa-1,3,5-triene complexes

Treatment of tungsten hexacarbonyl with a mixture of cyclo-octa-1,3,5-and -1,3,6-triene gives the complex [W(OO iCslIiohJ (85). The hydrocarbon is believed to be the 1,3,6-triene, acting as a diene, but for the reasons mentioned (see Section III,H) it is possible that the ligand is bicyclo[4,2,0]-octa-2,4-diene (XV). 

Chelate complexes of the type [PdX2(diene)] (X = Cl, Br) are readily formed by the dienes hexa-1,5-diene (124), bicyclo 2,2,lJhepta-2,5-diene (1, 7) tricyclo[4,2,2,0]-deca-triene and -diene derivatives (10), cyclo-octa-1,5-diene and dicyclopentadiene, but not dipentene (43). These may be converted to complexes of the types [Pd2X2(dieneOR)2] and [PdCl(dieneOR)-(amine)] (R = alkyl) (43), and their properties indicate that they have similar structures to the platinum complexes (XXXI) and (XXXIII). 

Anhydrous silver-olefin complexes are readily dissociable, low-melting, and variable in composition 92a, 176, 183). Cyclic olefins and polyolefins form stable complexes with silver nitrate or perchlorate, but again the Stoichiometry of the complexes varies considerably, sometimes depending on the conditions of preparation. The following types have been isolated [Ag(un)2]X (un = e.g., cyclohexene, a- and /3-pinene) ISO), [Ag(diene)]X diene = e.g., dicyclopentadiene 220), cyclo-octa-1,5-diene 50, 130), bi-cyclop, 2,1 ]hepta-2,5-diene 207), and cyclo-octa-1,3,5-triene 52), and [Ag2(diene)]X2 (diene = e.g., cyclo-octa-1,3- and -1,4-diene 180), bi-cyclo[2,2,l]hepta-2,5-diene 1) and tricyclo[4,2,2,0]-decatriene 10)). Cyclo-octatetraene (cot) forms three adducts with silver nitrate 52), viz., [Ag(cot)]NOs, [Ag(cot)2]N03, and [Ag3(cot)2](N03)3. On heating, the first two lose cyclo-octatetraene and all three decompose at the same temperature. From the stoichiometry of the above complexes it appears that the... 

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 ... 

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... 

Cyclo-octa-1,3,5-triene is conveniently stored as its SO2 adduct mild heating regenerates the triene. 9-Thiabicyclo[4,2,l]nona-2,4,7-triene 9,9-dioxide and 9-thiabarbaralane 9,9-dioxide both react with antimony pentafluoride in sulphur dioxide at — 50°C to give the cm/o-homotropylium-8-sulphinate complex (241 ... 

Treatment of ll,ll-dichloro-l,6-methano[10]annulene with Bu"Li in an ether solvent yields C22H hydrocarbons of labile and complex nature/ Trapping experiments support the intermediacy of compounds ( )6) and (607) formed by the sequence of rearrangements (605)- (606)- (607). Reaction of cyclo-octa-2,4,6-trien-l-one with the anion of methyl 4-(dimethylphosphinyl)but-2-enoate gave (608) and (609) the predominant isomer (609) resulted from base-catalysed isomerization of (608) under the conditions of reaction. Low-temperature oxygenation of the enolate anion derived from the mixture of (608) and (609), followed by reduction with triethyl phosphite, gave a 1 1 mixture of 8-methoxycarbonylbicyclo[5,3,l]undeca-l,3,5,9-tetraen-8-exo-ol and -1,3,5,8-tetraen-lO-exo-ol. Pyrolysis of the p-nitro-benzoate esters of these alcohols effected their conversion into methyl 1,5-methano-[10]annulenecarboxylate (610). 

Cyclo-octa-l,5-diyne, prepared in 2% yield by dimerization of buta-l,2,3-triene, has been examined by X-ray diffraction and shown to be almost planar with C—C C bond angles of 159.3°. Irradiation of cyclo-octa-l,5-diyne gave buta-l,2,3-triene, and treatment with ba gave cyclo-octa-tetraene. Cyclo-octa-l,5-diyne underwent Diels-Alder reactions with two molecules of buta-1,3-diene and 2,3-dimethylbuta-1,3-diene, but gave complex mixtures of products when treated with bromine, iodine, dimethyl acetylenedicarboxylate, or tcne. ... 

C19H2nFeNi03, Iron nickel cyclobutadiene complex, 35B, 585 Cl 9H2n05Ru2Si2, Pentacarbonyl-M- 2 -3 -T ,7 -8 -7 4 -6 -T -[4-(cyclo-octa-2 , 5 ,7 -triene-l ,4 -diyl)-1,1,4,4-tetramethyl-l,4-disilapen-tyl] diruthenium(Ru-Ru), 46B, 929 C19H2 gCrN203, (2SR,2 RS)-Tricarbonyl[5-ethyl-2-(5 -ethyl-1 ,2 ,3 ,4 -tetrahydro-l -methyl-2 -pyridyl)-1,6-dihydro-1-methyl-pyridineichromium, 46B, 930... 

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). ... 

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. ... 

Protonation of complexes of cyclo-octa-1,3,5-triene and reaction with nucleophiles is discussed. 

The pure olefin complex, (cyclo-octa-1,3,5-triene)(cyclo-octa-l,5-diene) iron, CjHioFeCsHia, has been prepared in 13% yield by this route [39] the analogous Ru and Os complexes have been reported [39a]. Cyclo-dodeca-l,S,9-triene nickel may be prepared similarly using trialkyl-aluminiums as the reducing agents [40]. 

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. 

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). °... 

Irradiation of solutions of cycloheptatrieneiron tricarbonyl at low temperatures followed by addition of diphenylacetylene produces the [2 + 6] adduct, 7,8-diphenyl-bicyclo[4,2,l]octa-2,4,7-triene similar results were obtained with cyclo-octatetraene-iron tricarbonyl and related compounds. The mechanism suggested involved photo-induced replacement of one of the olefin bonds or carbon monoxide ligands in the complexes by a solvent molecule, thermal replacement of the solvent by the acetylene, and an intramolecular cycloaddition. ... 

The bicyclo[4,2,0]octa-2,4,7-trienyl iron carbonyl complexes (285) and (286) are stable, even in refluxing benzene, in marked contrast to the rapid valence isomerization of free bicyclo[4,2,0]octa-2,4,7-triene to cyclo-octatetraene. This stability is due to the loss of the inert gas configuration on rearrangement to a diTiapto-cyclo-octatetra-ene-Fe(CO)3 complex. The inert gas structure could be retained if the cyclobutene ring of the complexes opened via a forbidden disrotatory opening, but this does not occur because the metal is not in a position to help sterically. ... 

---