Polyolefin complexes, cyclic

The general patterns of structures and bonding in metal poly-olefin complexes are similar to those in olefin complexes. Linear, branched and cyclic polyolefin complexes are known. The bonding is delocalized over the carbon atoms and the metal(s). These species also play important roles in organic syntheses. 

Smooth copolymerization of alkenes with dienes would produce polyolefins with cyclic groups or vinyl pendant groups. The copolymerization was studied by using early transition metal complexes, including metallocene, half metallocene, and nonmetallocene complexes of Zr. 

A number of cyclic polyolefin complexes of metal carbonyls have been shown to react with aluminum halides to produce cyclic ketones [Eqs. (44)-(46)] (212-214). This type of reaction affords easy synthetic routes to... 

Cyclic Polyolefin Complexes. The principal examples of these are the cyclooctatetraene complexes (23-XL1J) and (23-XL11I). In both classes it has... 

Books have been published on cyclic polyolefin complexes and metal vapour synthesis, while a review on metal vapour cryochemistry also contains information relevant to the latter. Reviews have also been published on organometallic derivatives of alkenes and ketenes, cationic Rh diolefin complexes, and nucleophilic addition to cationic hydrocarbon complexes. More personalized reviews have appeared by Maitlis on Pd -acetylene chemistry, by Jonas and Kruger on alkali-metal-transition-metal w-complexes, and by Werner on bridged allyl and cyclopentadienyl complexes. Articles by Wilke on homogeneous catalysis, by Vollhardt on metal-mediated approaches to steroid synthesis, by Schrock > on organotantalum chemistry, and by Grubbs on nickel metallocycles also contain material of relevance to r-complexes. 

G. Deganello, Transition Metal Complexes of Cyclic Polyolefins. Academic Press, London, 1980, 476 pp. 

The first metal-olefin complex was reported in 1827 by Zeise, but, until a few years ago, only palladium(II), platinum(Il), copper(I), silver(I), and mercury(II) were known to form such complexes (67, 188) and the nature of the bonding was not satisfactorily explained until 1951. However, recent work has shown that complexes of unsaturated hydrocarbons with metals of the vanadium, chromium, manganese, iron, and cobalt subgroups can be prepared when the metals are stabilized in a low-valent state by ligands such as carbon monoxide and the cyclopentadienyl anion. The wide variety of hydrocarbons which form complexes includes olefins, conjugated and nonconjugated polyolefins, cyclic polyolefins, and acetylenes. 

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... 

Cyclic oligomeric phosphonates with the varying degrees of structural complexity (Structure 5.4) are also available in the market.25 They are widely used as flame-retardant finishes for polyester fabrics. After the phosphonate is applied from an aqueous solution, the fabric is heated to swell and soften the fibers, thus allowing the phosphonate to be absorbed and strongly held. It is also a useful retardant in polyester resins, polyurethanes, polycarbonates, polyamide-6, and in textile back coatings. A bicyclic pentaerythritol phosphate has been more recently introduced into the market for use in thermosets as well as for polyolefins (preferably, in combination with melamine or ammonium polyphosphate)... 

Cyclooctadiene is a cyclic polyolefin particularly prone to transannular closure under a variety of conditions. With certain metal complexes such as that described below, isomerization to c -bicyclo[3.3.0]oct-2-enehas been observed.67 Phenyl-... 

With metallocene catalysts, not only homopolymers such as polyethylene or polypropylene can be synthesized but also many kinds of copolymers and elastomers, copolymers of cyclic olefins, polyolefin covered metal powders and inorganic fillers, oligomeric optically active hydrocarbons [20-25]. In addition, metallocene complexes represent a new class of catalysts for the cyclopolymerization of 1,5- and 1,6-dienes [26]. The enantio-selective cyclopolymerization of 1,5-hexadiene yields an optically active polymer whose chirality derives from its main chain stereochemistry. 

Deganello, G. Transition Metal Complexes of Cyclic Polyolefins, Academic New York, 1979. Davison, A. McFarlane, W. Pratt, L. Wilkinson, G. Chem. Ind. (London) 1961, 553. Davison, A. McFarlane, W. Wilkinson, G. Chem. Ind. (London) 1962, 820. 

For cyclopolyene and cyclopolyenyl complexes of transition metals, see (a) G De-ganello. Transition Metal Complexes of Cyclic Polyolefins. London Academic Press, 1979, Chap 1. (b) MLH Green, DKP Ng. Chem Rev 95 439-473, 1995. 

In a series of papers215-220, Stone and coworkers show that upon reaction of ruthenium carbonyl silyl complexes such as (CO)4Ru(SiMe3)2 and [(CO)4RuSiMe3]2 with cyclic polyolefins, silyl groups migrate from ruthenium to the ring. Examples are shown in equations 76216 and 77217. 

Cyclic Alkenes.— A number of studies have established that tertiary phosphines react with polyolefin metal carbonyl complexes in a variety of ways (i) by CO displacement, (ii) by displacement of the polyolefin, or (iii) by nucleophilic addition of phosphine to the ring system. The last reaction now appears to be the first step in some examples of type (ii), e.g. the addition of PBu s to [M(CO)3( -C7H7)]+ (M = Cr, Mo, or W) which follows Scheme 3. An independent investigation gives similar... 

Complexes containing two cyclic polyolefinic ligands will be included in this section if one of the rings is cyclopentadienyl. 

A variety of RU2- and Rug-complexes containing silicon-substituted cyclic polyolefins have been prepared and one of these, [RugCCgHgSiMegCHg-CH3iMe2)(CO)s], has been shown to contain an unusual -hydrocarbon ligand bridging both ruthenium atoms. The reactions of [Ru2(CO)e(DAB)]... 

---