Cyclohexene complexes with silver

Cyclohexaselenium, 28 137-142 Cyclohexasulfur (S ), 18 288, 293, 294 Cyclohexene complexes with gold, 12 348 with silver, 12 342... 

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 cyclohexadiene complex 29 has been further elaborated to afford either the cydo-hexenone 34 or the cyclohexene 36 in moderate yields (Scheme 1) [21]. The addition of HOTf to 29 generates the oxonium species 33, which can be hydrolyzed and treated with cerium(IV) ammonium nitrate (CAN) to release the cyclohexanone 34 in 43 % yield from 29. Alternatively, hydride reduction of 33 followed by treatment with acid eliminates methanol to generate the r 3-allyl complex 35. This species can be trapped by the conjugate base of dimethyl malonate to afford a cyclohexene complex. Oxidative decomplexation of this species using silver trifluoromethanesulfonate liberates the cyclohexene 36 in 57 % overall yield (based on 29). 

Complexes. Silver tetrafluoroborate is insoluble in cyclohexane but very soluble in water, ether, toluene, and nitromethane, and moderately soluble in benzene and cyclohexene. - Solubility in the unsaturated hydrocarbons is attributed to n-bond formation between the unsaturated compound and silver ion. Complexes have been observed with both ir-electron donors and lone-pair donors thus Meerwein prepared stable complexes with benzene, mesitylene, cycloheptatriene, diethyl ether, dimethyl sulfoxide, and a series of acid nitriles. However, the silver tetrafluoroborate-benzene complex is reported variously as a 1 1 complex, a 1 2 complex, and as a 2 3 complex. ... 

A catalytically active silylsilver intermediate was observed using low-temperature 29Si NMR and IR spectroscopy (Scheme 7.18).83 Exposure of cyclohexene silacyclopropane 58 to the silver complex produced cyclohexene as well as a new species, which exhibited two doublets at 97 ppm (./Agsi = 260 and 225 Hz) in the 29 Si 1H NMR spectmm. The 29 Si H NMR spectra of this species are consistent with a Lewis base-stabilized metal silylenoid. Tilley and coworkers have reported that (Et3P)2Pt(H)-Si(Sf-Bu)2(OTf) appears at 52 ppm,39 and Jiitzi et al. observed... 

Transition metal complexes were known to facilitate the addition of silylene to acetylenes from a variety of different sources.60,61,90,91 These conditions, however, often required heating, and the initially formed silacyclopropene often incorporated a second molecule of the acetylene to afford a silole.92,93 With their discovery of low-temperature silver-mediated di-ferf-butylsilylene transfer conditions from cyclohexene silacyclopropane 58 to olefins, Woerpel and coworkers set out to investigate the... 

Experimental information on the energetics of silver-olefin bonds comes from a 1973 study by Partenheimer and Johnson26. Using titration calorimetry with the inert dichloromethane as solvent, these authors measured the enthalpies of reaction 14 for several olefin complexes (hfacac = 1, 1, 1, 5, 5, 5-hexafluoro-2,4-pentanedionate) whose structure (1) is illustrated below for olefin = cyclohexene. 

The interaction by ji coordination of Ag(I) between silver ions and C=C double bonds or aromatic groups is the basic principle for many effective chromatographic separations. Silver trifluoroacetate and silver trifluoromethanesulfonate are very soluble in poly(methylphenylsiloxane), due to the presence of phenyl groups. Such stationary phases were studied for the GC separation of benzene-cyclohexene-cyclohexane mixtures. The salting-out effects and formation constants of the complex of Ag(I) with various olefinic and aromatic compounds were estimated based on retention time measurements271. 

---