John F. Knifton

Homogeneous olefin hydroformylation catalyzed by ligand stabilized platinum(II)-group IVB metal halide complexes

Abstract Ligand-stabilized platinum(II)-Group IVB metal halide complexes have been found to catalyze the homogeneous hydroformylation of olefins to aldehydes. With the preferred catalyst composition, bis(triphenylphosphine)platinum(II) chloride-tin(II) chloride, α-olefin hydroformylation proceeds under mild conditions [60–80 °C, 800–1500 psig H 2 CO (1:1)], to give good yields of aldehyde (85–90 mole%), and high selectivity of the desired linear, straight-chain, aldehyde (85–93 mole%). The dependence of the yield and linear aldehyde selectivity, upon catalyst and olefin structure, temperature, H 2 CO pressures, reactant concentrations and solvent composition has been studied, and is discussed in relation to the proposed hydroformylation mechanism for this class of catalyst.

Ethylene glycol-dimethyl carbonate cogeneration

Abstract In this paper eight classes of effective, and in most cases novel, transesterification catalysts are identified for the cogeneration of ethylene glycol plus dimethyl carbonate from ethylene carbonate and methanol. They include: (a) macroreticular and gel-type exchange resins with tertiary amine and quaternary ammonium pendant groups, (b) zirconium, titanium and tin homogeneous catalysts, (c) homogeneous Group VB and VIB compounds, (d) alkali metal silicates on silica, (e) ammonium-exchanged zeolites, (f) acidic resins bearing sulfonic acid and carboxylic acid functional groups and (g) tertiary phosphine polymer catalysts. Liquid products comprising in many cases near-equilibrium concentrations of ethylene glycol and dimethyl carbonate have been cogenerate in⩾ 98 mol% selectivity (based on EC converted) using continuous unit equipment under moderate conditions (60–150 °C, 100 psi). Unreacted methanol plus EC make up >99% of the remaining organics. The relative performance advantages and mechanistic pathways of these different classes of catalyst are compared and discussed.

Syngas reactions : II. The homogeneous catalyzed carbonylation and cyclization of allylic substrates

Abstract Carbon monoxide insertion and/or addition to allylic precursors may lead to the formation of both linear and cyclic carbonylation products. In examining these competing reaction paths, rhodium, platinum, palladium and nickel-based homogeneous catalysts have been developed which are particularly useful for the selective synthesis of γ-butyrolactam, N -alkyl-2-pyrrolidones, vinylacetate and phenylacetate esters and diesters from a variety of allylic and benzylic substrates. The extension of this catalysis to the carbonylation of certain vinylic and propargyl congeners had also been considered.

Syngas reactions III. Ruthenium catalyzed homologation of aliphatic carboxylic acids

Selective homologation of aliphatic carboxylic acids has been demonstrated via ruthenium homogeneous catalysis. C3+ carboxylic acids are prepared from syntheis gas plus acetic acid solutions of ruthenium precursors, e.g., RuO2, Ru3(CO)12 and H4Ru4(CO)12, coupled with alkyl or hydrogen iodide promotes. Other linear and branched carboxylic acids may be homologated by one or more additional methylene groups and this versatile technique provides a novel means to building such acids exclusively from CO/H2. The scope and mechanism of carboxylic acid homologation has been examined in relation to the structure of the acid substrate, the concentration, and composition of the ruthenium catalyst precursor and iodide promoter, syngas ratios, as well as 13C enrichment studies and the spectral identification of ruthenium iodocarbonyl intermediates.

Syngas reactions: IV. Vicinal glycol esters from synthesis gas☆

Abstract Vicinal glycol esters, such as ethylene glycol acetate esters, are prepared from synthesis gas via homogeneous ruthenium catalysis. Aliphatic carboxylic acids, e.g., glacial acetic acid, act both as coreactant and as ruthenium catalyst solvent for this CO-hydrogenation reaction. Yields and selectivity to glycol ester are substantially improved through the addition of bulky cationic promoters, particularly quaternary phosphonium and cesium cations.

α,β-unsaturated carboxylic esters from alkynes catalyzed by homogeneous palladium complexes

Abstract Ligand-stabilized palladium(II)—tin(II) chloride complexes exemplified by ((p-CH3·C6H4)3P)2PdCl2SnCl2 and ((CH3)2C6H5P)2PdCl2SnCl2, have been found to catalyze the regioselective carbonylation of 1-alkynes. Linear α,β-unsaturated acid esters are obtained in up to 96 mol% selectivity under mild conditions.

Syngas reactions: I. The catalytic carbonylation of conjugated dienes

Abstract 3,8-Nonadienoate acid esters are prepared from 1,3-butadiene in 80 mol% yields and >90% selectivity when catalyzed by combinations of halide-free palladium salts and tertiary alkyl-phosphine ligands of p K a > 8, solubilized in N -heterocyclics and tertiary arylamines of moderate base strength (e.g., quinoline and N,N -diethylaniline). The related palladium(II) acetate-triphenylphosphine couple in isoquinoline/2-propanol allows continued improved activity upon recycle and turnover number exceeding 2 × 10 3 . Concurrent C 5 and C 9 acid syntheses are possible with Pd(OAc) 2 -DIPHOS. The importance of counterion and Group VB donor ligand structure together with preferred solvent properties are discussed in relation to palladium carbonylation performance and inactivating side reactions.

Homogeneous catalyzed reduction of nitrocompounds: II. Hydrogenation to oximes

Abstract Group IB metal salts solubilized in alkylpolyamine solvents have been found to catalyze the homogeneous hydrogenation of nitroalkanes to oximes in good yields. The selective synthesis of various linear, cyclic, and substituted oximes is described. The effectiveness of copper and silver salts is in the order, Cu(I) ≈ Cu(II) > Ag(I), for constant anion, with specific activity being particularly sensitive to the structure and basicity of the amine solvent and to the addition of π-acceptor ligands. For the synthesis of cyclohexanone oxime from nitrocyclohexane, catalyzed by solutions of copper(I) chloride in ethylenediamine, the proposed mechanism involving initial formation of cuprous hydride by hetcrolytic splitting of molecular hydrogen, followed by deoxygenation of the coordinated nitroalkane anion as a rate-determining step, is consistent with observed kinetics, deuterium isotope effects, and the use of complex metal hydrides as the hydride source.

New synthesis gas chemistry

Abstract Recent research at Texaco regarding new synthesis gas chemistry has focused on (a) the production of aliphatic primary amines through olefin oxoamination using CO/H 2 plus ammonia, (b) the amidocarbonylation of olefin and aldehyde substrates for the synthesis of a variety of amidocarboxylic acids and (c) the development of a Texaco Fischer-Tropsch process for the generation of low MW alcohol fuels. Both the scope and chemistry of these syntheses will be discussed in this chapter. Important classes of chemical products that can be made using this technology include surface active agents, specialty surfactants, food additives, chelating agents, as well as intermediates for sweetness, anticorrosion agents and paint dispersants.

Syngas reactions: IX. Acetic acid from synthesis gas

Abstract Acetic acid has been generated directly from synthesis gas ( CO H 2 ) in up to 95 wt% selectivity and 97% carbon efficiency using a RuCoI Bu 4 PBr “melt” catalyst combination. The critical roles of each of the ruthenium, cobalt and iodide catalyst components in achieving maximum selectivity to HOAc have been identified. C 1 -oxygenate formation is only observed in the presence of ruthenium carbonyls; [Ru(CO) 3 I 3 ] − is here the dominant species. Controlled quantities of iodide ensure that initially formed MeOH is rapidly converted to the more reactive methyl iodide. Subsequent cobalt-catalyzed carbonylation to acetic acid may be preparatively attractive (>80% selectivity) relative to competing syntheses where the [Co(CO) 4 ] − concentration is maximized; that is, where the Co/Ru ratio is > 1, the syngas feedstock is rich in CO and the initial iodide/cobalt ratios are close to unity. Formation of cobalt-iodide species in significant concentrations appears to be an inhibiting step in this synthesis.