Copper olefins

Copper-olefin bonding is of both practical and theoretical interest in view of the catalytic activity of copper(I) toward olefin activation and its role in biological systems. 

Copper olefin complexes are usually generated by the direct reaction of a Cu(l) source, the ligand, and the corresponding olefin. Copper ethylene complexes are of interest in view of their biochemical importance,98,98a-98e their applications in organic chemistry,99,99a,99b and industrial applications.100 100 Because of this, many copper alkene complexes have been reported, with different nuclearity, in compounds with one, two, or even three C=C units coordinated to a given copper center. 

This rate expression is consistent with the reaction scheme shown in Eq. 10.6, formulated on the basis of the Krauss-Smith paper. Thus, the initially formed cuprate dimer/enone complex with lithium/carbonyl and copper/olefin coordinations [71, 72] transforms into the product via an intermediate or intermediates. A lithium/ carbonyl complex also forms, but this is a dead-end intermediate. Though detailed... 

The central feature of the mechanism is the 3-cuprio(III) enolate Cpop, of an open, dimeric nature, as shown by comparison of theory with experimentation involving NMR and KIEs [80, 81]. This species serves as the direct precursor to the product (Scheme 10.5, top box). In this critical CPop complex, copper/olefin (soft/soft) and a lithium/carbonyl (hard/hard) interactions are present. The open complex may be formed directly, by way of an open cluster (bottom left of Scheme 10.5), or by complexation of a closed cluster with the enone (CPcl). Experiments have shown that the enone/lithium complex (top left of Scheme 10.11) is a deadend species [60, 74]. 

Copper (I) complexes of olefins have been less widely studied but have been found to be analogous to silver(I) complexes in several ways. It was shown 54>, that solid cuprous chloride absorbed ethylene, propylene and isobutylene and solid cuprous bromide absorbed ethylene to give 1 1 complexes, while diole-fms (butadiene and isoprene) and acetylenes were reported S6> to form complexes with a 2 I copper olefin (or acetylene) stoichiometry. Andrews and... 

A review of the photochemical properties of copper complexes includes a survey of the photocatalysed reactions of copper-olefin complexes. The addition of acetonitrile to norbornene may be induced by irradiation in the presence of silver ions. The reaction appears to involve excitation of a LMCT excited state of the norbomene-silver complexes and the formation of norbornene radical cations. 

Class 1—Photoexcitation of a preformed copper-olefin complex. Complexation plays a key role by shifting the absorption spectrum of the system into a wavelength region accessible to the irradiating light and/or by providing a sterically or electronically favored pathway to the photoproduct. 

The use of silver fluoroborate as a catalyst or reagent often depends on the precipitation of a silver haUde. Thus the silver ion abstracts a CU from a rhodium chloride complex, ((CgH )2As)2(CO)RhCl, yielding the cationic rhodium fluoroborate [30935-54-7] hydrogenation catalyst (99). The complexing tendency of olefins for AgBF has led to the development of chemisorption methods for ethylene separation (100,101). Copper(I) fluoroborate [14708-11-3] also forms complexes with olefins hydrocarbon separations are effected by similar means (102). 

Another attractive commercial route to MEK is via direct oxidation of / -butenes (34—39) in a reaction analogous to the Wacker-Hoechst process for acetaldehyde production via ethylene oxidation. In the Wacker-Hoechst process the oxidation of olefins is conducted in an aqueous solution containing palladium and copper chlorides. However, unlike acetaldehyde production, / -butene oxidation has not proved commercially successflil because chlorinated butanones and butyraldehyde by-products form which both reduce yields and compHcate product purification, and also because titanium-lined equipment is required to withstand chloride corrosion. 

Finally, selective hydrogenation of the olefinic bond in mesityl oxide is conducted over a fixed-bed catalyst in either the Hquid or vapor phase. In the hquid phase the reaction takes place at 150°C and 0.69 MPa, in the vapor phase the reaction can be conducted at atmospheric pressure and temperatures of 150—170°C. The reaction is highly exothermic and yields 8.37 kJ/mol (65). To prevent temperature mnaways and obtain high selectivity, the conversion per pass is limited in the Hquid phase, and in the vapor phase inert gases often are used to dilute the reactants. The catalysts employed in both vapor- and Hquid-phase processes include nickel (66—76), palladium (77—79), copper (80,81), and rhodium hydride complexes (82). Complete conversion of mesityl oxide can be obtained at selectivities of 95—98%. 

Apparently the alkoxy radical, R O , abstracts a hydrogen from the substrate, H, and the resulting radical, R" , is oxidized by Cu " (one-electron transfer) to form a carbonium ion that reacts with the carboxylate ion, RCO - The overall process is a chain reaction in which copper ion cycles between + 1 and +2 oxidation states. Suitable substrates include olefins, alcohols, mercaptans, ethers, dienes, sulfides, amines, amides, and various active methylene compounds (44). This reaction can also be used with tert-huty peroxycarbamates to introduce carbamoyloxy groups to these substrates (243). 

Thermal polymerization is not as effective as catalytic polymerization but has the advantage that it can be used to polymerize saturated materials that caimot be induced to react by catalysts. The process consists of the vapor-phase cracking of, for example, propane and butane, followed by prolonged periods at high temperature (510—595°C) for the reactions to proceed to near completion. Olefins can also be conveniendy polymerized by means of an acid catalyst. Thus, the treated olefin-rich feed stream is contacted with a catalyst, such as sulfuric acid, copper pyrophosphate, or phosphoric acid, at 150—220°C and 1035—8275 kPa (150—1200 psi), depending on feedstock and product requirement. 

The reactive species that iaitiate free-radical oxidatioa are preseat ia trace amouats. Exteasive studies (11) of the autoxidatioa mechanism have clearly estabUshed that the most reactive materials are thiols and disulfides, heterocycHc nitrogen compounds, diolefins, furans, and certain aromatic-olefin compounds. Because free-radical formation is accelerated by metal ions of copper, cobalt, and even iron (12), the presence of metals further compHcates the control of oxidation. It is difficult to avoid some metals, particularly iron, ia fuel systems. 

Tertiary bismuthines appear to have a number of uses in synthetic organic chemistry (32), eg, they promote the formation of 1,1,2-trisubstituted cyclopropanes by the iateraction of electron-deficient olefins and dialkyl dibromomalonates (100). They have also been employed for the preparation of thin films (qv) of superconducting bismuth strontium calcium copper oxide (101), as cocatalysts for the polymerization of alkynes (102), as inhibitors of the flammabihty of epoxy resins (103), and for a number of other industrial purposes. 

Tetracyanoethylene is colorless but forms intensely colored complexes with olefins or aromatic hydrocarbons, eg, benzene solutions are yellow, xylene solutions are orange, and mesitylene solutions are red. The colors arise from complexes of a Lewis acid—base type, with partial transfer of a TT-electron from the aromatic hydrocarbon to TCNE (8). TCNE is conveniendy prepared in the laboratory from malononitrile [109-77-3] (1) by debromination of dibromoma1 ononitrile [1855-23-0] (2) with copper powder (9). The debromination can also be done by pyrolysis at ca 500°C (10). 

Alkyl chlorides. Olefins are chlorinated to alkyl chlorides in a single fluidized bed. HCl reacts with O9 over a copper chloride catalyst to form chlorine. The chlorine reacts with the olefin to form the alkyl chloride. The process developed by the Shell Development Co. uses a recycle of cat yst fines in aqueous HCl to control the temperature [Chem. Proc., 16, 42 (1953)]. 

In 1958 Simmons and Smith described a new and general synthesis of cyclopropanes by treatment of olefins with a reagent prepared from methylene iodide and a zinc-copper couple in ether solution. 

Perfluoroalkylation of perfluoroalkylethylenes and addition of perfluoroalkyl iodides to olefins or acetylenes are catalyzed by copper metal [238, 239] Similar copper-catalyzed addition of iododifluoroacetates to olefins has been observed [241]... 

The pyrolysis of perfluoro carboxylic salts can result both in mono and bimolecular products At 210-220 °C, silver salts give mostly the coupled products, at 160-165 °C in A -methylpyrrolidinone, the corresponding copper salts also give the simple decarboxylated compounds in nearly equal amounts The decomposition of the copper salts m the presence of lodobenzene at 105-125 °C results m a phenyl derivative, in addition to the olefin and coupled product [94] (equations 60-62)... 

In an alternative syntliesis of panaatistaliti (S7) by Trost et al. [52], fSdieme 9.15) addilioti of tlie Grlgtiatd teagetil 63 [53] lo a mixture of tlie azide 62 and copper cyanide reprodudbly gave tlie desired adduct 64. Because of tlie difliciilties associated witli purification of adduct, tlie overall yield of tlie two steps ftlie next being diliydroxylation of tlie olefin) was 6 296. 

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