Chadwick A. Tolman

Catalytic conversion of cyclohexylhydroperoxide to cyclohexanone and cyclohexanol

Abstract The low-conversion air oxidation of cyclohexane yields a mixture of cyclohexylhydroperoxide, cyclohexanone and cyclohexanol. The cyclohexyl-hydroperoxide is converted to additional cyclohexanone and cyclohexanol before the mixture is concentrated. Cobalt octoate is an active but short-lived catalyst for this transformation. Using a combination of pulse calorimetry and chemical luminescence techniques, a new family of long-lived catalysts has been discovered. These catalysts, based upon the (bis(2-pyridyl-imino)isoindolinato) ligand, are very active and long-lived, allowing cyclo-hexylhydroperoxide to be converted in a selective, low temperature process. The structure of one of these active catalysts, bis[bis((3-methyl-2-pyridyl)-imino)isoindolinato]cobalt(II), has been determined crystallographically. Under reaction conditions, it is likely that the active form of the catalyst has lost one ligand.

The reactivity of tetracarbonylnickel encapsulated in zeolite X. A case history of intrazeolite coordination chemistry.

Abstract Zeolite X shows a high capacity for tetracarbonylnickel (up to 28 weight percent) such that complete pore filling with ‘liquid like’ material takes place. The adsorbed material may be removed simply by evacuation at room temperature. Partial decomposition of the Ni(CO) 4 occurs on standing at room temperature under N 2 . The resultant orange species is highly reactive and has spectroscopic properties consistent with a coordinatively unsaturated ‘Ni(CO) 3 ’. Complete and irreversible decomposition by heating to 200 °C in vacuo gives a black zeolite, with an undefined metal phase, which is unreactive towards carbon monoxide. Reaction of the zeolite supported Ni(CO) 4 with various phosphorus ligands is highly dependent on the original loading level as well as the physical size of the ligands involved. At low loadings two kinds of reactivity are observed: 1) With ligands too large to gain access to the zeolite crystal interior, reaction occurs only in solution and so drags the Ni(CO) 4 from the zeolite: 2) With smaller ligands, reaction takes place inside the zeolite cages leading to well-defined, encapsulated, ship-in-bottle complexes which have a stoichiometry dictated by the available space in the cages. At high loading levels, pore blocking phenomena lead to inhomogeneous distributions of encapsulated complexes wherein a complete shell of phosphorous ligand substituted nickel carbonyl species forms at the crystal surface layers and prevents further reaction deeper inside the crystal. The reactivity with large phosphines has been used to study the diffusion of Ni(CO) 4 from the zeolite. Monitoring the appearance of the Ni(CO) 3 L (where L = phosphine) by 31-P NMR of the supernatant solution shows that Ni(CO) 4 leaves the zeolite with a first order rate constant of at least 2 × 10 −2 sec −1 at 298 K.

Synthesis of iron(II) phosphite complexes

Abstract The cationic iron(II) complexes, [Fe(P(OR) 3 ) 5 X] + , have been prepared by reactions involvin oxidation of Fe(P(OR) 3 ) 5 (for X = H, Me, CF 3 ) or addition of phosphites to iron bis(tetrahydrofuran) dihalide complexes (for X = Cl, Br, I). This latter reaction proceeds, under different conditions, through two distinctly different isolable species, both of which have been characterized by spectroscopic techniques including simulation of the 31 P{ 1 H} NMR spectra.

A Calometric study of steric effects in the reactions of phosphorus ligands with Ni(COD)2

Abstract A calometric study of the reactions of various phosphorous ligands (and t-BuNC) with di-1,5-cycloocatadienenickel shows that both the extent of reaction and mean Ni-P bond strengths tend to decrease with increasing ligand size. The steric strain energies in various NiL4 complexes and ΔG for their formation from nickel metal are estimated.

Shape selectivity in hydrocarbon oxidations using zeolite encapsulated iron phthalocyanine catalysts

The oxidation of alkanes by iodosobenzene is catalysed by iron phthalocyanine encapsulated inside large pore zeolites NaX and NaY so that the product alcohols and ketones show an improved yield and altered selectivity as compared to the unencapsulated complex.

Areneiron complexes from metal atom evaporation

Abstract Metal evaporation syntheses have given Fe(η 6 -arene)L 2 and Fe(η 6 -arene)-(η 4 -diene) complexes (where L  phosphorus ligand). Protonation and methylation of Fe(arene)L 2 complexes yield [Fe(arene)L 2H ] + and [Fe(arene)L 2 Me] + species, respectively. Protonation of Fe(arene)(η 4 -triene) complexes yields [Fe(arene)(η 5 -dienyl)] + salts.

The Oxidation of Organic Compounds by Metal Complexes in Zeolites

The selective oxidation of organic compounds to desired products has long been a challenge to chemists. The industrial oxidation of hydrocarbons to useful oxygenated compounds is commercially important and is carried out on a very large scale — on the order of several billons of pounds per year. The reactions are usually carried out at high temperatures(>150°C) and pressures,1 and often leave much to be desired in terms of selectivity. The difficultylies in the fact that the desired products are often themselves easily oxidizable, so that a certain percentage of the carbon is inevitably lost to CO and CO2, and other byproducts.

Intramolecular rearrangement in Cr[P(OMe)3]5H2

Cr[P(OMe)3]5H2 is fluxional on the n.m.r. time scale allowing the first detailed mechanistic analysis of intramolecular exchange in a seven co-ordinate complex having all monodentate ligands.