Cyclooctatriene complexes

Cyclooctatetraene (continued) with iron, 12 267-273 with nickel, 12 307, 308 with palladium, 12 315 with platinum, 12 319 with rhodium, 12 304 with ruthenium, 12 280 with silver, 12 340, 342, 343, 346 complexes of, 4 81 iron complexes of, 4 89 Cyclooctatriene complexes... 

Coordinated cycloheptatrienes show a considerably larger upheld shift on complexation ( 40 ppm) relative to analogous A -arene derivatives ( 25 ppm) (147). A possible explanation may lie in the greater strength of the triene-metal bond. The preferential coordination of the triene moiety in 1-phenylcycloheptatriene complexes is consistent with this view. Fluxional properties of A -cycloheptratriene and A -cyclooctatriene complexes are dis-... 

A mixture of cycloocta-l,3,5-triene and cycloocta-l,3,6-triene formed by partial reduction of cyclooctatetraene is the usual starting point for the study of cyclooctatriene complexes, and obviously complexes may be derived from both isomers. Also, the 1,3,5-isomer is in thermal equilibrium with its valence tautomer, bicyclo[4.2.0]octa-2,4-diene (XXVII), at 100° C (30), from which complexes may also be formed. Although silver nitrate... 

The RuCl2(PPh3)3 complex has now been used to selectively hydrogenate 1,5,9-cyclooctatriene to the monoene (101), dienes to monoenes... 

Cyclooctatetraene was reduced electrochemically to cyclooctatetraenyl dianion. In DMF the product is mostly (92%) 1,3,5-cyclooctatriene at —1.2 V. If the potential is lowered the main product is 1,3,6-cyclooctatriene. Previous experiments, in which the anion radical was found to be disproportionated, were explained on the basis of reactions of the cyclooctatetraene dianion with alkali metal ions to form tightly bound complexes, or with water to form cyclooctatrienes. The first electron transfer to cyclooctatetraene is slow and proceeds via a transition state which resembles planar cyclooctatetraene102. 

Success was obtained with Ru3(CO)i2 as catalyst precursor [6], but the most efficient catalysts were found in the RuCl2(arene)(phosphine) series. These complexes are known to produce ruthenium vinylidene spedes upon reaction with terminal alkynes under stoichiometric conditions, and thus are able to generate potential catalysts active for anti-Markovnikov addition [7]. Similar results were obtained by using Ru(r]" -cyclooctadiene)(ri -cyclooctatriene)/PR3 as catalyst precursor [8]. (Z)-Dienylcarba-mates were also regio- and stereo-selectively prepared from conjugated enynes and secondary aliphatic amines (diethylamine, piperidine, morpholine, pyrrolidine) but, in this case, RuCl2(arene) (phosphine) complexes were not very efficient and the best catalyst precursor was Ru(methallyl)2(diphenylphosphinoethane) [9] (Scheme 10.1). 

Total yield of the mixture of valence tautomers A and B. Valence tautomer B could not be detected for the case n = 1 in the products of the preparative run. All valence tautomers B for n = 1,2, 3 and even n = 0 (i.e., the bicyclo[2.1.0]pcntanc-annulatcd cyclooctatriene) can, however, he prepared from their corresponding tricarbonyliron complexes by oxidation with... 

A tris(trimethylsilyl)pentalene complex was obtained in 15% yield from a trisubstituted cyclooctatriene with Ru3(CO)12 (75, 95) ... 

This inversion barrier is much lower than that observed for derivatives of cyclooctatetraene (see Section X,B), and recognition that the fluorinated ring in complexes 119 may more closely resemble a cyclooctatriene than a cyclooctatetraene provides one rationale for the difference in its dynamic behavior compared to its rj1 -heptafluorocyclooctatetraeny 1 relatives. 

With regards to actinides, Summerscales et al. [105] have also reported the reductive disproportionation of C02 to carbonate and squarate products, using COTR/ CpR mixed-sandwich U(III) complexes (COT = cyclooctatriene, Cp = cyclopenta-dienyl, R = Si Pr3, R = H, Me). U(III) systems have been shown previously to reduce C02 to a linear Tl -O-coordinated mono-anion [63], and to doubly reduce to give O2- salts plus CO [75, 76]. In this case, the reactions can be considered... 

Complex 224 is also obtained by cyclotrimerization of acetylene promoted by complex 223, with displacement of the bicyclotriene ligand. It is noteworthy that complex 223 is obtained from 200 by simple cycloaddition of alkyne to the cyclooctatriene ligand (139) [Eq. (24)]. 

Scheme 7.6 Preparation of 1,5-cy clo octadiene (1,3,5-cycloheptatriene) and 1,5-cyclooctadiene(l,3,5-cyclooctatriene) metal(O) complexes via the isopropyl Grignard method (25, 27 ...

The suggestion by Fischer et al. (210) that (l,3,r)-cyclooctatriene)tri-carbonylchromium is a ferrocene-type metal-arene complex (27), has been confirmed by X-ray diffraction (10). The molecular structure... 

The reaction between RuglCOlja and 1,3-cyclooctatriene has been reported 97) to give a yellow complex of composition (CgHi2)Rus(CO)io. 

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