Cyclo-octatetraene complexes, with

Cyclo-octatetraene reacts with iron carbonyls to form complexes with the compositions [Fe(CO)3(C8H8)], [Fe2(CO)6(C8H8)], and [Fe2(CO)7(C8H8)] 152, 168, 180). Nakamura and Hagihara 166) report that the complex [Fe(CO)3(C8H8)] decolorizes bromine in carbon tetrachloride and shows absorption bands in its infrared spectrum at 699, 716, and 720 cm-1 due to cis-double bonds. They suggest structure (XVI) for this complex, i.e., the hydrocarbon retains its tub form in the complex. These results are con-... 

The preparation of monocyclo-octatetraenyl uranium(IV) alkoxide complexes from reaction of uranium cyclo-octatetraene precursors with alcohols has been reported [318]. A very unusual monomeric complex, U(OTeF5)6, which can be con-... 

Among mixed-ligand cyclo-octatetraene complexes, the U, Th, Pa, Np, and Pu complexes [(r -Cx 11x)An(p-SPr)2]2 were reported, which can be prepared by reacting the thiol with U(COT)(BH4) [399a], Reduction of the bulky 8-annulene thorium complex [Th COT(TBS)2 2] [COT(TBS)2 = CxIIfi(/-BuMc2Si)2-l,4] by potassium... 

There are many complexes of Cu1 with olefins or other unsaturated compounds, and these are in general rather similar19 to those of Ag+ (page 1051). Although they are usually made by direct reaction with Cu1 halides, they may also be prepared from cupric salts by reduction with trialkyl phosphites in ethanolic solution in presence of the alkene.193 The crystalline compounds obtained when using chelating alkenes such as norbornadiene or cyclic polyalkenes usually have polymeric structures, such as that for the cyclo-octatetraene complex (25-H-V), and only one of the double bonds is normally coordinated. 

Cyclo-octatetraene reacts with [H4Ru4(CO)i2] to give the dimer (217) and its tri-carbonylruthenium complex amongst other products. A minor product in this... 

The synthesis of bis(rj8-cyclooctatetraene)uranium(IV) (uranocene)J from uranium tetrachloride and (cyclooctatetraene)dipotassium was first published in 1968.1 The method reported here is a modification of that procedure and is suitable for a large variety of cyclooctatefraene complexes.2-4 BisO 8-cyclo-octatetraene)uranium(IV) has also been prepared by the reaction of uranium tetrafluoride with (cyclooctatetraene)magnesium in the absence of solvent.5 Direct reaction of finely divided uranium metal with cyclooctatetraene vapors at 150° also gives some uranocene.5 However, both methods give low yields. 

A single crystal X-ray structural determination of the binuclear complex [Fe2(CO)6(C8H8)] (64a) shows it to have the structure (XVIII) and not one of the previously suggested structures 22, 54,152,166,174) including tub and planar forms of the cyclo-octatetraene ring. The cyclo-octatetraene ring in the complex approximates to a chair form in which the four carbon atoms associated with each iron atom are planar or very nearly so. The observed Fe—C and C—C distances in this complex are compared... 

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... 

The electrochemical technique has been relatively rarely applied to obtain the metal 7i-complexes [202,506,507], Thus, the electrosyntheses of complexes of copper with cyclo-octadiene and nickel with cyclo-octatetraene were reported [202,506,507]. The electrochemical reactions (3.242) are of especial interest, since they allow us to produce fe-cyclopentadienyl complexes [563-565] ... 

Recently, the first U(V) heteroleptic cyclo-octatetraene-dithiolene complex 992 was synthesized by AgBPh4 oxidation in THF of the [(COT)UIV(dddt)2][Na(18-crown-6)]2 precursor, which was synthesized by reacting [(COT)UX2(THF)J (X = BH4, n = 0 X = I, n = 2) with Na2dddt [490]. In general, despite the relatively small number of reported actinide S-containing complexes, they have a potentially rich coordination chemistry of such compounds of hard /-elements with soft S-ligands [489] and possible applications [491]. 

One of the first and perhaps most interesting examples of a metal-assisted, symmetry-forbidden reaction was Reppe s synthesis of cyclo-octatetraene from acetylene 34). in a careful study of this system, Schrauzer proposed a concerted mechanism in which the four a bonds of the cyclo-octatetraene are essentially formed simultaneously 35). He proposed an octahedral complex (54) with four acetylene hgands fitted to adjacent ligand coordination positions, spatially defining the incipient cyclooctatetraene. 

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. ... 

A two-step synthesis of barbaralone from (cyclo-octatetraene)tricarbonyliron involves treatment of the complex with anhydrous aluminium chloride in benzene followed by the addition of carbon monoxide. 

Further details have appeared concerning the polar 1,4-homoaddition of iV-chloro-sulphonylisocyanate with 1,4-bridged vinylcyclopropanes. The dispiro-system (304) is cleaved to a biradical which, in the presence of an appropriate styrene, affords the paracyclophane (305). Methylenecyclopropane and 3,3-dimethylcyclopropene afford the air-sensitive complexes (306) and (307), respectively, with 2,2 -bipyridyl-(cyclo-octatetraene)nickel, and 2f-ray structural analyses have been performed. The complexes can be easily decomposed, (306) to (308), and (307) to (309). 

The preparation of copper(i) trifluoroacetate and the formation of some phosphine and olefin complexes from it are described. Triphenylphosphine forms mono-, bis-, and tris-phosphine complexes, but evidence for co-ordination of four phosphine groups could be obtained only with bis(diphenyl-phosphino)ethane. The tris(triphenylphosphine)copper(i) trifluoroacetate is also formed by reduction of copper(ii) trifluoroacetate with triphenylphosphine in alcoholic solution. Cyclo-octa-1,5-diene forms 1 1 and 1 2 complexes with copper(i) trifluoroacetate, and cyclo-octatetraene forms a 1 2 complex for which the structure (155) is suggested. ... 

The reaction of actinide tetrachlorides (thorium through plutonium) with the potassium salt of cyclo-octatetraene (COT) results in the formation of actocene complexes, rf — CgH8)2An, named by analogy with ferrocene. All these compounds have a sandwich structure in which two planar COT rings enclose a metal atom. 

Cycloaddition.— Reactions of electrophilic olefins and acetylenes with tricarbonyl-iron complexes of cycloheptatriene and cyclo-octatetraene lead to 1,3-exo-products. Troponetricarbonyliron and tcne, however, have now been found to give complex (20) which results from previously unobserved 1,5-exo-cycloaddition. A dipolar intermediate (21) resulting from initial attack by the electrophile on the hydrocarbon... 

A new dimer of cyclo-octatetraene has been prepared.Reaction of cyclo-octatetraene with the hydrido-carbonylruthenium cluster H Ru (CO)j2 gives the dimer (332) as its tricarbonylruthenium complex. The molecular structure of the complex was determined by X-my crystallography. The metal-free dimer was prepared by oxidation of the complex with cerium(iv). l%is hydrocarbon may be recognized as the product of the unknown Diels-Alder dimerization of cyclo-octatetraene. 

Me, = H 71 %) and (208 R = H, R = Me 21.5 %) was obtained from the iron tricarbonyl complex of methylcyclo-octatetraene. Oxidation of these adducts with ceric (iv) ion gives dihydrotetracyanotriquinacenes in good yield. tcne reacts with the iron-tricarbonyl complex of unsubstituted cyclo-octatetraene to give the 1,3-adduct (208 R = R = H) which is oxidized by cerium (iv) to a dihydrotetracyano-triquinacene. ... 

Treatment of H4Ru4(CO)i2 with freshly distilled cyclo-octatetraene in heptane at reflux yielded the novel dimers (680) and (681) and the tricarbonylruthenium complex of the cyclohexadiene unit of (681). The tautomer (680) was isolated as a complex... 

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