Acetonitrile complexes, with

Through selective complexation with nitromethane, dimethyl carbonate and dimethyl oxalate, it was possible to isolate [18]crown-6 in 98 % purity from a crude reaction mixture 14a). Although the acetonitrile complex with [18]crown-6 has been known for some time, the structure was determined only recently because of rapid crystal deterioration 14). 

Compound Monomer Dimer Complexes with acetonitrile Complexes with methanol Complexes with water ... 

Figure 9 An example of a five-coordinate Cu complex (a) and a copper acetonitrile complex with a substituted tris(pyrazolyl) hydroborate ligand (b)...

Five solvated dirhenium acetonitrile complexes with the Rej " " unit have been reported [Re2 (CH3CN)i(j][BArf]4, cw-Re2(dppm)2(CH3CN)g[BF4]4, tr KS-Re2(dppm)2(CH3CN)g[BF4]4, trans-Re2(pynp)2(CFl3CN)4[BF4]4 and tr KS-Re2(tznp)2(CH3CN)4[PFg][BFj3 [98]. 

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

To eluate an antibiotic from chromatographic columns as a mobile phase such solvents as methanol, ethanol, propanol, acetone, acetonitrile are usually used. Influence of these solvents on ions Eu(III) in a complex with OxTC and Cit has been investigated. It is established, that the used solvents do not reduce I Eu(III) ions, and sometimes they increase I by 16-45 %. 

Crown-6 [17455-13-9] M 264.3, m 37-39 . Recrystd from acetonitrile and vacuum dried. Purified by pptn of 18-crown-6/nitromethane 1 2 complex with Et20/nitromethane (10 1 mixture). The complex is decomposed in vacuum and distilled under reduced pressure. Also recrystd from acetonitrile and vacuum dried. 

A terminal 1,13 diene with interstitial deka(difluoromethylene) chain is converted to the corresponding diepoxide by repeated reacUon with a very large excess of hypofluorous acid-acetonitrile complex [22](equation 14)... 

Other measures of nucleophilicity have been proposed. Brauman et al. studied Sn2 reactions in the gas phase and applied Marcus theory to obtain the intrinsic barriers of identity reactions. These quantities were interpreted as intrinsic nucleo-philicities. Streitwieser has shown that the reactivity of anionic nucleophiles toward methyl iodide in dimethylformamide (DMF) is correlated with the overall heat of reaction in the gas phase he concludes that bond strength and electron affinity are the important factors controlling nucleophilicity. The dominant role of the solvent in controlling nucleophilicity was shown by Parker, who found solvent effects on nucleophilic reactivity of many orders of magnitude. For example, most anions are more nucleophilic in DMF than in methanol by factors as large as 10, because they are less effectively shielded by solvation in the aprotic solvent. Liotta et al. have measured rates of substitution by anionic nucleophiles in acetonitrile solution containing a crown ether, which forms an inclusion complex with the cation (K ) of the nucleophile. These rates correlate with gas phase rates of the same nucleophiles, which, in this crown ether-acetonitrile system, are considered to be naked anions. The solvation of anionic nucleophiles is treated in Section 8.3. 

The reaction of alkoxyarylcarbene complexes with alkynes mainly affords Dotz benzannulated [3C+2S+1C0] cycloadducts. However, uncommon reaction pathways of some alkoxyarylcarbene complexes in their reaction with alkynes leading to indene derivatives in a formal [3C+2S] cycloaddition process have been reported. For example, the reaction of methoxy(2,6-dimethylphenyl)chromium carbene complex with 1,2-diphenylacetylene at 100 °C gives rise to an unusual indene derivative where a sigmatropic 1,5-methyl shift is observed [60]. Moreover, a related (4-hydroxy-2,6-dimethylphenyl)carbene complex reacts in benzene at 100 °C with 3-hexyne to produce an indene derivative. However, the expected Dotz cycloadduct is obtained when the solvent is changed to acetonitrile [61] (Scheme 19). Also, Dotz et al. have shown that the introduction of an isocyanide ligand into the coordination sphere of the metal induces the preferential formation of indene derivatives [62]. 

It is expected, therefore, that the cyclic hexamer also exhibits a characteristic tendency to complex with cations. In fact, the addition of an acetonitrile solution of metal thiocyanates to a solution of the cyclic hexamer in the same solvent shifted the carbonyl absorption to a lower wave number46,52 The shift values depended upon the kind of metal ions present, and the largest shift value of 40 cm-1 was observed for barium thiocyanate (molar ratio of Ba2+/hexamer = 10). In addition to the shift of the carbonyl absorption, the intensities of the C—O-C stretching vibrations around 1200 cm-1 varied appreciably. 

In 1999, Kiindig and Bruin reported a closely related catalyst system 29a, in which a more readily accessible ligand has been employed [37]. Catalytic activity and stability are strongly dependent upon the nature of the neutral ligand L. While the acetonitrile complex 29b is stable, yet catalytically inactive, complex 29a with L = acrolein is stable only in the solid state, but decomposes as a solution in DCM... 

Reinhoudt and coworkers studied the synthesis of hyper-branched polymers composed of organopalladium complexes with an SCS pincer ligand [11]. Removal of acetonitrile ligands on palladium led to the self-assembly of dinu-clear palladium complex (9) to give hyper-branched polymer (10), which was... 

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