Brian E. Hanson

Supported aqueous-phase catalysts

Abstract This work describes a novel family of catalysts denoted supported aqueous-phase catalysts. These catalysts consist of a water-soluble organometallic complex supported in a thin film of water residing on a high-surface-area hydrophilic solid. The catalytic reaction takes place at the water-organic interface where the organic phase contains the reactants and products. Supported aqueous-phase catalysis is demonstrated by liquid-phase hydroformylation. The solid support used here was either CPG-240 or CPG-350; both are porous glasses with narrow pore volume distributions. The catalytic species, HRh(CO)[ m -P(PhS0 3 Na) 3 ] 3 was synthesized from Rh(CO) 2 (acac) by a new synthetic route and impregnated onto CPG-240. Solution and solid-state 31 P NMR data are consistent with a mobile rhodium species in the aqueous phase in hydrated forms of the catalyst. The hydroformylation of oleyl alcohol (OLOH) was accomplished at 100°C and 5.1 MPa of H 2 /CO (1/1) using 0.002 g Rh/g OLOH. For example, conversions of up to 96.6% could be achieved in 5.5 h. It is postulated that no significant leaching of Rh occurs, since after filtration to remove the solid catalyst the remaining solution showed no activity for either the hydroformylation of additional OLOH or the hydrogenation of added 1-hexene. The observations that (1) OLOH and its hydroformylation products are not water soluble, (2) the double bond of OLOH is internal, and (3) the Rh does not leach into the organic phase demonstrate the concept of SAP catalysis; the immobilized homogeneous catalyst is active at the interface of two immiscible phases.

Pressure-Induced Cooperative Bond Rearrangement in a Zinc Imidazolate Framework: A High-Pressure Single-Crystal X-Ray Diffraction Study

The pressure-dependent structural evolution of a neutral zinc-imidazolate framework [Zn(2)(C(3)H(3)N(2))(4)](n) (ZnIm) has been investigated. The as-synthesized three-dimensional ZnIm network (alpha-phase) crystallizes in the tetragonal space group I4(1)cd (a = 23.5028(4) A, c = 12.4607(3) A). The ZnIm crystal undergoes a phase transition to a previously unknown beta-phase within the 0.543(5)-0.847(5) GPa pressure range. The tetragonal crystal system is conserved during this transformation, and the beta-phase space group is I4(1) (a = 22.7482(3) A, c = 13.0168(3) A). The physical mechanism by which the transition occurs involves a complex cooperative bond rearrangement process. The room-temperature bulk modulus for ZnIm is estimated to be approximately 14 GPa. This study represents the first example of a high-pressure single-crystal X-ray diffraction analysis of a metal-organic framework.

Amphiphilic phosphines for catalysis in the aqueous phase

Abstract Two new phosphines, Tris[ p -(10-phenyldecyl)phenyl]phosphine and 2,2′-Bis{di[ p -(10-phenyldecyl)phenylphosphinomethyl}-1,1′-biphenyl were successfully synthesized and sulfonated in concentrated H 2 SO 4 . The resulting water soluble surface active phosphines were applied to the rhodium catalyzed hydroformylation of higher olefins. It is found that these two ligands are not only excellent for octene hydroformylation, but catalyze tetradecene hydroformylation under two phase conditions as well. Rates and selectivities are superior to TPPTS modified rhodium catalysts under the same reaction conditions.

Propylene hydroformylation on rhodium zeolites X and Y. II: In situ Fourier transform infrared spectroscopy

Abstract In situ Fourier transform infrared spectroscopy studies of carbonyl formation and propylene hydroformylation by RhNaX and RhNaY are reported. Rhodium dicarbonyl is formed on NaX. Two dicarbonyl species are present on NaY if the zeolite is dried prior to exposure of carbon monoxide. If the NaY is not dried, Rh 6 (CO) 16 is ultimately formed. Propylene hydroformylation is shown to be proceeding similarly on RhNaX and RhNaY in homogeneous-like reaction pathways by comparing the in situ infrared spectra taken under hydroformylation conditions to data from solution. The selective poisoning of a RhNaY catalyst is consistent with hydroformylation active sites located on the surface of the zeolite particles.

Supported aqueous-phase, rhodium hydroformylation catalysts. I, New methods of preparation

Improved methods for the preparation of supported aqueous phase (SAP) catalysts are described. An in situ preparation of the supported rhodium complex and a more effective hydration procedure are presented. SAP catalysts are also prepared by a self-assembly experiment in which the separated components of a SAP catalyst spontaneously adopt a SAP configuration under reaction conditions.

Novel chiral water soluble phosphines II. Applications in catalytic asymmetric hydrogenation

Abstract The results of the homogeneous asymmetric hydrogenation of several dehydroamino acids by rhodium-diene complexes of the chiral ligands; 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)butane, 2a ; 2,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)pentane, 3a ; and 2,3-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino) butane, 4a ; and their N-protonated and N-Me quaternized analogues are reported. The ligands comprise a versatile set which can be used both in organic and aqueous solvents. A detailed investigation of solvent and substituent effects is provided. The presence of p-NMe 2 groups enhances the rate of reaction in all cases. For the DIOP derivative, 2a , the presence of the dimethylamino group causes a reversal in the observed dominant product antipode. This is attributed predominantly to a change in preferred ligand conformation rather than to a kinetic difference between the two diastereomers of a single ligand conformation.

CTAB micelles and the hydroformylation of octene with rhodium/TPPTS catalysts: Evidence for the interaction of TPPTS with micelle surfaces

Abstract The addition of cetyltrimethylammonium bromide (CTAB) to TPPTS/rhodium hydroformylation catalysts has a complicated effect on reaction activity and selectivity. In water alone as the solvent, high CTAB concentration leads to the formation of emulsions and reaction selectivity drops. In aqueous alcohol solvents selectivity also drops but the effect appears to be due to the solvent composition. Emulsion formation is minimized and initial reaction activity goes through a maximum at a CTAB/TPPTS ratio of 3. NMR studies show that there is a strong interaction of CTAB and TPPTS in water while the interaction in aqueous methanol appears to be nonspecific.

NEW DIRECTIONS IN WATER SOLUBLE HOMOGENEOUS CATALYSIS

Abstract A brief review of the role of water soluble ligands in the immobilization of homogeneous catalysts is given. Amphiphilic water soluble phosphines that aggregate in water are described. In aqueous biphasic catalysis use of the amphiphilic ligands leads to improved reaction rates with substrates that are poorly water soluble. The amphiphilic ligands aggregate in aqueous solution and there is evidence that these ligand aggregates solubilize the substrates in the aqueous phase.

Supported aqueous-phase, rhodium hydroformylation catalysts II. Hydroformylation of linear, terminal and internal olefins

Abstract Hydroformylation of 1−, 2−, and 3-heptene by supported aqueous-phase (SAP) catalysts shows that the conversion to aldehydes and the regioselectivity are functions of the position of the double bond. I-Tetradecene and 1-heptadecene give results similar to 1-heptene while data obtained from t -7-tetradecene compare well to those observed from t -2-heptene indicating the independence of chain length. Linear dienes are shown to be hydroformylated as well. Effects of temperature and pressure and water content are illustrated using linear, terminal, and internal olefins.

Bis[tris(m(sodium sulfonato)phenyl)phosphine] hexacarbonyl dicobalt, Co2(CO)6 (P(m-C6H4SO3Na)3)2, in a supported aqueous phase for the hydroformylation of 1-hexene

Abstract The synthesis of the cobalt carbonyl phosphine complex, Co2(CO)6(P(m-C6H4SO3Na)3)2, is described and the complex is used as a catalyst for the hydroformylation of 1-hexene under two-phase and supported aqueous phase reaction conditions. Under two-phase reaction conditions both with and without excess phosphine substantial quantities of cobalt are leached into the organic phase and the observed activity is consistent with catalysis from HCo(CO)4 in the organic phase. When the complex is supported onto the controlled pore glass CPG-340 in a supported aqueous phase configuration the amount of cobalt lost into the organic phase is minimized and the observed activity appears to come from the complex on the glass. When excess phosphine as well as the complex are supported on the glass cobalt leaching is further reduced under batch reaction conditions.