Cycloocta-l,5-dienes

An example of a rhodium(I) complex with a tridentate phosphine is shown in Figure 2.16 it is formed by the usual route, reaction of the phosphine with [RhCl(cycloocta-l. 5-diene)]2. 

With dienes and acetylenes, only M = Fe, Co or Ni showed activity. The Fe and Co systems gave many side products. Therefore, the Ni catalyst was studied in greater detail. Bis-(7r-cycloocta-l,5-diene)nickel(0) was equivalent to the Ziegler catalyst in hydrosilation of penta-1,3-diene. 

These Ziegler catalysts were inactive for hydrosilation of cyclopenta-diene, c/s,c/s-cycloocta-l,5-diene, or norbornadiene. 

A solid-state transformation that involves an electrocyclic ring opening is described by Bellus and his co-workers (78). They found that when 1,2,5,6-tetracyano-anri-tricyclo-[4.2.0. O Joctane (33) is heated in the crystal, only 1,2,5,6,-tetracyano-(Z,E)-cycloocta-l, 5-diene (34a) is formed, as expected on... 

Since borane BH3 reacts with only one or two equivalents of a sterically hindered alkene, it is possible to prepare less reactive and more selective borane reagents R2BH and RBH2 respectively. In addition to disiamylborane 8 and thexylbo-rane 10, the 9-borabicyclo[3.3.1]nonane (9-BBN) 14 is an important reagent for hydroboration, since it is stable to air it is prepared by addition of borane 2 to cycloocta-l,5-diene 13 ... 

Ni-organic chemistry of butadiene started in the early 1950 s when this substrate could be slowly dimerized to cis, cis-cycloocta-l,5-diene in relatively low yields ( 40%) by using so-called Reppe catalysts of the type L2Ni (CO)2. Carbonyl-free low-valent Ni-complexes and catalysts on the basis of Cr and Ti were more effective and also led to further ring-syntheses (Scheme 1-1)... 

Thermal cyclodimcrization of methylenecyclopropane results in head-to-head cycloaddition (see Section 1.3.1.1.). By contrast the bis(cycloocta-l,5-diene)nickel(0) catalyzed reaction of methylenecyclopropane gives the head-to-tail dimerization product 6 in 9% yield in addition to a [3 + 2] dimer 7.20... 

Bipyridylnickelacyclopentane (2), obtained by addition of 1,4-dibromobutane to 2,2 -bipyridylbis( 4-cycloocta-l,5-diene)nickel in tetrahydrofuran, liberated cyclobutane in 45-60% yield on treatment with oxygen and highly activated alkenes, such as 1,4-benzoquinone, dimethyl fumarate, or maleic anhydride.121 122... 

Fitch, J. W., and Kettner, C. A., Texas J. Sci. 26, 53 (1975) Chem. Abstr., 83, 164344 (1975) (Reaction of cycloocta-l,5-diene-copper(I)chloride with dimethyldivi-nylsilane). 

The ( /4-bicyclo[2.2.1]hepta-2,5-diene)bis( /3-2-propenyl)ruthenium(II) and (>/4-cycloocta-l,5-diene)bis(>/3-2-propenyl)ruthenium(II) complexes have previously been reported,5,6 but we present here scaled-up procedures that produce synthetically useful quantities of these compounds. The preparation of Grignard reagents is based upon the methods described by Eisch.7... 

The complexes ( /4-cycloocta-l, 5-diene)bis(>/3-2-methyl-l-propenyl)-ruthenium(II), [ Ru(i/4-C8H12)(02CCCl3) 2(p-02CCCl3)2(/i-0H2)], and [ Ru( 4-C7H8)(02CCF3) 2(p-02CCCl3)2(p-0H2)] may be prepared by procedures similar to those described for the related complexes in Sections D, E, and G. 

Ru,F, OgC24Hi6, Ruthenium(II), )A-aqua-bis-( x-trinuoroacetato)bis[(-ri4-cycloocta-l,5-diene)(trifluoroacetato)-, 26 254... 

Similarly, (r/3-crotyl)(cycloocta-l,5-diene)palladium hexafluoro-phosphate can be activated with a with a co-catalyst such as AgBF4 or AgSbF6 (40). 

Amino-3-cyanofurans (307) are obtained by base catalyzed condensation of the acyloins (306) with malonodinitrile, and on acid hydrolysis yield the butenolides (308) (Scheme 80) (66CB1002). Diketene and an isocyanide react to give the lactone (309) in the presence of a tertiary base (73GEP2222405). When diphenylketene is treated with bis(cycloocta-l,5-diene)nickel and pyridine, the complex Ni(py)2(Ph2C=CO)2 is formed which is converted into compound (310) by carbon monoxide (78JOM(l52)C29). 

Aryltrimethylstaimanes arylate aldehydes in the presence of a cationic rhodium complex, [Rh(cycloocta-l,5-diene)(MeCN)2]+, yielding secondary alcohols.114... 

In a different system, l-(trimethylsilyl)cycloocta-l,5-diene forms complexes with Ag(I), Rh(I), Pd(H) and Pt(II), in which the metals are pushed away from the Me3Si group267. The distortion in their structures, in comparison with the near-symmetrical structures of the corresponding 1,5-cyclooctadiene complexes, changes the characteristics of their 111 and 13 C NMR spectra. 

Bis(cycloocta-l,5-diene)nickel, (C8H,2)2Ni, shows the molecular ion, and fragment ions C8H12Ni+, C4H6Ni+, and Ni+ (149). The platinum analog, (C8H12)2Pt, shows as the principal ions (C8H12)2Pt+, CgH12Pt+,... 

Die Cycloocta-l,5-diene sind moglicherweise keine primaren Photopro-dukte, sondern durch Cope-Umlagerung der entsprechenden 1,2-Divinyl-cyclobutane entstanden. 

Cycloocta-l,5-diens (Formel 41) in der Gasphase. Neben polymerem Material entstehen zu 2—3 % zwei isomere Substanzen, die als Bicyclo-[5,l,0]octen-(3) (Formel 42) und Tricyclo[3,3,0,02< ]octan (Formel 43) identifiziert werden konnten (280, 283). 

Wahrend im Cycloocta-l,5-dien beide Doppelbindungen cis-Anordixung besitzen, leitet sich 43 vom trans-trans-Cydoocta-l,5-dien ab. Der Grand konnte nach Srinivasan (280) darin bestehen, daB im angeregten Zustand beide Doppelbindungen trans-konfiguriert sind. 

Complexes of nickel constitute a distinct group of homogeneous alkylalumi-nium-free catalysts for olefin polymerisation. An efficient catalyst for ethylene polymerisation is formed in the reaction of bis(cycloocta-l,5-diene)nickel(0) [Ni(Cod)2] with phosphorus-ylid and triphenylphosphine in toluene solvent [181] ... 

Styrene undergoes polymerisation with the cationic organonickel(II) complex / 3-methallyl ( /4-cycloocta-l,5-diene)nickel hexafluorophosphate [(MeAll) (Co<7)/W]+[PF]6 combined in situ with tricyclohexylphosphine. The product of such polymerisation is a styrene oligomer with Mn = 1900, characterised by a... 

In this table Cp, pentamethylcyclopentadienyl bipy, 2.2 bipyridyl diox, 1.4-dioxane cod, cycloocta-l,5-diene. 

Cycloocta-l,5-diene)cyclopentadienylpalladium(II) tetrafluo-roborate is an air-stable solid, soluble in polar solvents such as chloroform, methylene dichloride, acetone, or methanol and insoluble in alkanes, benzene, or ether. Its solution in acetone displays a conductivity characteristic of a 1 1 electrolyte.1 Its... 

Reaction of chromium atoms, l,5-cyclooctadiene(l,5-cod), and PF3 on the other hand yielded a separable mixture of [Cr(C8Hu)(PF3)3H] and (j74-cycloocta-l,5-diene)tetrakis(trifluorophosphine)chromium. The latter is readily converted to the former by warming a solution of it to 90°C (Scheme 3). This rearrangement is impaired under an atmosphere of PF3 and the 1,5-cod is preferentially displaced to give [Cr(PF3)6]. 

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