Berth-Jan Deelman

Fluorous phase separation techniques in catalysis

Fluorous solvents have limited miscibility with conventional organic solvents. Combined with the fact that compounds functionalized with perfluorinated groups often dissolve preferentially in fluorous solvents this can be used to extract fluorous components from reaction mixtures. This review discusses the application and potential of fluorous phase separation techniques for the recovery of soluble metal catalysts.

Membrane reactor for homogeneous catalysis in supercritical carbon dioxide

A membrane reactor is presented for homogeneous catalysis in supercritical carbon dioxide with in situ catalyst separation. This concept offers the advantages of benign high-density gases, i.e., the possibility of achieving a high concentration of gaseous reactants in the same phase as the substrates and catalyst as well as easy catalyst localization by means of a membrane. For the separation of the homogeneous catalyst from the products an inorganic microporous membrane is used. The concept is demonstrated for the hydrogenation of 1-butene using a fluorous derivative of Wilkinson’s catalyst [RhCl{P–(C 6H4-p-SiMe2CH2CH2C8F17)3}3]. The size of Wilkinson’s catalyst, 2–4 nm, is clearly larger than the pore diameter, 0.5–0.8 nm, of the silica membrane. The membrane will, therefore, retain the catalyst, while the substrates and products diffuse through the membrane. Stable operation and continuous production of n-butane has been achieved at a temperature of 353 K and a pressure of 20 MPa. A turnover number of 1.2× 10 5 has been obtained during 32 h of reaction. The retention of the catalyst was checked using UV–vis spectroscopy and ICP-AAS; no rhodium or phosphorous species were detected at the permeate side of the membrane.

Fluorous derivatives of [Rh(COD)(dppe)]BX4 (X=F, Ph): synthesis, physical studies and application in catalytic hydrogenation of 1-alkenes and 4-alkynes

Abstract Fluorous derivatives of 1,2-bis(diphenylphosphino)ethane (dppe) ( 1 ), containing a para-(1H,1H,2H,2H-perfluoroalkyl)silyl function, were used in the synthesis of fluorous derivatives of [Rh(COD)(dppe)]BF4. The single crystal X-ray crystallographic structure of [Rh(COD)( 1a )]BPh4 ( 7 ) was determined ( 1a =[CH2P(C6H4–SiMe2CH2CH2C6F13-p)2]2). Large differences in catalytic activity and selectivity (higher hydrogenation activity and lower isomerization activity) relative to [Rh(COD)(dppe)]BF4 were observed in the hydrogenation of 1-octene using non-fluorous, silyl-substituted [Rh(COD)( 2 )]BF4 ( 5 ; 2 =[CH2P(C6H4–SiMe3-p)2]2 or [Rh(COD)( 3 )]BF4 ( 6 ; 3 =[CH2P(C6H4–SiMe2C8H17-p)2]2) and even more so with fluorous [Rh(COD)( 1a )]BF4 ( 4a ). For 4a and 6 , the presence of aggregates was demonstrated by dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryoTEM), which is most probably responsible for these differences. Similar differences between (fluorous) silylated catalysts and non-substituted [Rh(COD)(dppe)]BF4 were observed in the semi-hydrogenation of 4-octyne. Recycling of highly fluorous catalyst [Rh(COD)( 1c )]BF4 ( 4c ; 1c =[CH2P(C6H4-Si(CH2CH2C6F13)3-p)2]2) was investigated in two different fluorous biphasic solvent systems. The catalyst could be recycled with 97.5% (for PFMCH/acetone, 1:1 v/v) and >99.92% (for FC-75/hexanes, 1:3 v/v) retention of rhodium, respectively. The leaching of phosphorus was comparable to the leaching of rhodium (in PFMCH/acetone), showing that dissociation and leaching of free ligand does not take place for these rhodium diphosphine catalysts.

Homogeneous Reactions in Supercritical Carbon Dioxide Using a Catalyst Immobilized by a Microporous Silica Membrane

Membrane separation technology is successfully applied for the immobilization of a homogeneous catalyst (a (1H,1H,2H,2H-perfluoroalkyl)dimethylsilyl-substituted derivative of Wilkinsons catalyst) in a continuous process that uses supercritical carbon dioxide as solvent. The catalyst is separated from the products by a microporous silica membrane (see scheme).

Fluorous biphasic hydrogenation of 1-alkenes using novel fluorous derivatives of Wilkinson's catalyst

Abstract A novel approach for the easy attachment of fluorous tails to aryl phospines has been developed, leading to a new fluorous alkylsilyl-substituted triaryl phospines P(C 6 H 4 SiMe 2 R f -4) 3 (R f =-(CH 2 ) 2 (CF 2 ) n CF 3 ; n =5, 7). The derived fluorous tris(aryl phospine)rhodium(I) chloride complexes, being fluorous analogs of Wilkinsons catalyst, show high activity in hydrogeneration of 1-alkenes under fluorous biphasic (FBS) conditions and can be effectively recycled.

Tetrakis{3,5-bis(perfluorohexyl)phenyl}borate: a highly fluorous anion

Abstract In search of new possibilities for rendering catalysts soluble in fluorous solvents, the preparation of a sodium derivative of tetrakis{3,5-bis(perfluorohexyl)phenyl}borate, a new and highly fluorous anion, is described. This weakly coordinating anion exhibits substantial affinity for perfluorinated solvents and is therefore expected to make a broad range of cationic transition-metal catalysts compatible with fluorous biphasic recycling techniques.

Intramolecularly Stabilised Group 10 Metal Stannyl and Stannylene Complexes: Multi‐pathway Synthesis and Observation of Platinum‐to‐Tin Alkyl Transfer

Reaction of [PdClMe(P^N)2] with SnCl2 followed by Cl-abstraction leads to apparent Pd-C bond activation, resulting in methylstannylene species trans-[PdCl{(P^N)2SnClMe}][BF4] (P^N = diaryl phosphino-N-heterocycle). In contrast, reaction of Pt analogues with SnCl2 leads to Pt-Cl bond activation, resulting in methylplatinum species trans-[PtMe{(P^N)2SnCl2}][BF4]. Over time, they isomerise to methylstannylene species, indicating that both kinetic and thermodynamic products can be isolated for Pt, whereas for Pd only methylstannylene complexes are isolated. Oxidative addition of RSnCl3 (R = Me, Bu, Ph) to M(0) precursors (M = Pd or Pt) in the presence of P^N ligands results in diphosphinostannylene pincer complexes trans-[MCl{(P^N)2SnCl(R)}][SnCl4R], which are structurally similar to the products from SnCl2 insertion. This showed that addition of RSnCl3 to M(0) results in formal Sn-Cl bond oxidative addition. A probable pathway of activation of the tin reagents and formation of different products is proposed and the relevancy of the findings for Pd and Pt catalysed processes that use SnCl2 as a co-catalyst is discussed.

Iminophosphanes: Synthesis, Rhodium Complexes, and Ruthenium(II)-Catalyzed Hydration of Nitriles

Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both κ1 and κ2 complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 °C, 3 h) and water (100 °C, 24 h) and under solvent free conditions (180 °C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand.

Platinum- and palladium-catalysed Kocheshkov redistribution of dialkyltin dichlorides or tetraalkyltins with tin tetrachloride

The Kocheshkov redistribution reaction of tetraalkyltin or dialkyltin dichlorides with tin tetrachloride is effectively catalysed by platinum(II) or palladium(II) phosphine complexes, yielding alkyltin trichlorides in high yield and with high selectivity.

Organolanthanide-catalysed Oligomerisation of 2-Cycloalken-1-ones

Yttrium and lanthanum hydrides [(C5Me5)2LnH]2 are active catalysts for the oligomerisation of 2-cycloalken-1-ones; the average degree of oligomerisation increases with temperature.