Complex of ethylene

Furthermore, treatment of the aminopalladation product with bromine affords aziridines[176]. The aziridine 160 was obtained stereoselectively from methylamine and 1-decene in 43% yield. The aminopalladation of PdCl2 complexes of ethylene, propylene, and 1-butene with diethylamine affords the unstable ir-alkylpalladium complex 161, which is converted into the stable chelated acylpalladium complex 162 by treatment with CO[177],... 

The carbonylation of COD PdCl2 complex in aqueous sodium acetate produces /rui7x-2-hydroxy-5-cyclooctenecarboxylic acid /i-lactone (240). The lactone is obtained in 79% yield directly by the carbonylation of the COD complex in aqueous sodium acetate solution[220]. /i-Propiolactone (241) is obtained in 72% yield by the reaction of the PdCC complex of ethylene with CO and water in MeCN at —20 " C. /3-Propiolactone synthesis can be carried out with a catalytic amount of PdCC and a stoichiometric amount of CuCl2[221]. 

The shift in the C=C frequency, vi, for adsorbed ethylene relative to that in the gas phase is 23 cm-1. This is much greater than the 2 cm-1 shift that is observed on liquefaction (42) but is less than that found for complexes of silver salts (44) (about 40 cm-1) or platinum complexes (48) (105 cm-1). Often there is a correlation of the enthalpy of formation of complexes of ethylene to this frequency shift (44, 45). If we use the curve showing this correlation for heat of adsorption of ethylene on various molecular sieves (45), we find that a shift of 23 cm-1 should correspond to a heat of adsorption of 13.8 kcal. This value is in excellent agreement with the value of 14 kcal obtained for isosteric heats at low coverage. Thus, this comparison reinforces the conclusion that ethylene adsorbed on zinc oxide is best characterized as an olefin w-bonded to the surface, i.e., a surface w-complex. 

The last stage is supposed to be limiting. However, the limiting stage can be the transformation of the TT-complex into the o-complex of ethylene with palladium (preliminary stage). The rate constant k (water, T 298 K, ion force = 3g ion L-1) has the following values [246]. 

Cant and Hall (13) suggest a mechanism of leaking D into the zeolite by exchange with acidic OH via 1 1 complex of ethylene. For D2, D is presumably leaking into the pool of rapidly moving H. Imanaka et al. (12) suggest that a triatomic intermediate is formed with the hydroxyls. If this is true for the supercage hydroxyls, the residence time of D2 on the surface site occupied by a proton should be on the order of 10-6 sec to have a chance to capture the proton (23, 25). 

Bromination of ethylene oxide vu reported as early as 1862 by Wurtz18 7 to give a red solid of unknown constitution. Maas and Boomer1081 obtained the same red solid on warming to room temperature oxonium complexes of ethylene oxide and bromine prepared at —80°. Freezing-point results indicated for these complexes the empirical formulas CsH40 Bt and CxH 0-2Br. No explosion occurs on warming to room temperature, however. 

The action of boron trichloride has been examined with several epoxidea. Grimley and Holliday871 claimed to have isolated the oxen him complex of ethylene oxide and boron trichloride by allowing them... 

The gas-phase oxidation of ethylene to ethylene oxide over a supported silver catalyst was discovered in 1933 and is a commercially important industrial process. Using either air or oxygen, the ethylene oxide is produced with 75% selectivity at elevated temperatures (ca. 250 °C). Low yields of epoxides are obtained with propylene and higher alkenes so that other metal-based catalysts are used. A silver-dioxygen complex of ethylene has been implicated as the active reagent.222... 

Bromine complexes of ethylene and cyclopropene have been isolated in argon matrices and studied by IR spectroscopy and ab initio methods. Two methods, namely MP2 and BLYP, were compared and found suitable for the calculation of IR spectra as they exhibited only minor differences.25... 

Other methods for obtaining complexes of ethylene and other alkenes include ligand substitution reactions, reduction of a higher valent metal in the presence of an alkene, and synthesis from alkyl and related species [reductive elimination, of an allyl or hydride, for example hydride abstraction from alkyls protonation of sigma-allyls from epoxides (indirectly)] [74a],... 

Figure 4-28. The tt- complexes of ethylene formed from the 6-member chelate (after methyl acrylate insertion) with the model (14, 14a, 14b, 14c) and real catalyst (14, 14a )...

There is no dissent that the first step of the reaction should be the complexing of ethylene to give the palladium complex 2 according to eq. (8). 

The mechanism of the Wacker oxidation is simply another Pd-catalyzed nucleophilic substitution of an alkene, with H2O as the nucleophile. H2O adds to a Pd(II) complex of ethylene, and /3-hydride elimination occurs to give a 77 complex of the enol of acetaldehyde. After rotation about the Pd(II)-alkene a bond, the alkene reinserts into the Pd(II)-H bond to give a new Pd(II)-alkyl. This complex undergoes /3-hydride elimination one more time to give acetaldehyde itself and Pd(II)-H. Deprotonation of the Pd(II) complex converts it to Pd(0), and oxidation of Pd(0) by air (see below) brings it back to Pd(II). 

Lattermann et al. reported the first metallomesogenic dendrimer when they described results on trigonal bipyramidal metal complexes of ethylene-imine dendrimers of the first and second generation, based on derivatives of tris(2-aminoethyl)amine. Complexes of cobalt, nickel, copper, and zinc were prepared and found to exhibit relatively low temperature mesophases, which generally possessed hexagonal columnar structures. These materials therefore provided the first examples of metallomesogenic dendrimers [72,73]. 

Use for resolution of cycloalkenes. W s-Cycloalkenes of intermediate size (Cg-Cjo) should be capable of existing in enantiomeric forms because of the inability of the trans double bond to rotate with respect to the remainder of the molecule. But in the absence of salt-forming groups, resolution cannot be accomplished by the usual methods of forming derivatives. However, Cope et al.s found that the strong tendency of an alkene to complex with a platinum compound provides an effective method of resolution. The complex of ethylene with platinous chloride and (+) or (-)-a-methylbenzylamine exists in only one form since ethylene is symmetrical. But addition of the base to a solution of the platinum complex of trans-cyclooctene opens the way for formation of the diastereoisomeric complexes derived from the R- and S-forms of the base. Fractional crystallization at —20° (liquid at 25°) effected separation. Liberation of the (—)-hydrocarbon from the complex with potassium cyanide gave a product of aD — 411°. 

Formation constants for the complexing of ethylene and propylene with tris-triphenylphosphinechlororhodium(I) have been obtained 9S> that for propylene is lower than that for ethylene by a factor of over 103. 

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