Carlaxel Andersson

Synthesis and structure of dimethoxyethane-dichlorodioxo-tungsten(VI) : a highly soluble derivative of tungsten dioxodichloride

Abstract WOCl4 reacted with hexamethyldisiloxane at room temperature in the presence of ethyleneglycol dimethylether (dme) giving the white crystalline compound, WO2Cl2(dme) (80% yield) and its structure was determined by X-ray diffraction. The structure, which is isomorphous with MoO2Cl2(dme), is built up of discrete molecules with a distorted octahedral geometry, the tungsten atom coordinates two oxygens in cis positions, two dme oxygen atoms and two chlorine atoms.

Reduction of tungsten(VI) and molybdenum(V) by allyltrimethylsilane and cyclopentene. Simple high yield syntheses of MoCl4(OEt2)2, MoCl4(dme), WCl4(thf)2, WCl4(dme) and WOCl3(thf)2

Abstract Convenient high yield methods to prepare MoCl 4 (OEt 2 ) 2 , MoCl 4 (dme), WCl 4 (thf) 2 , WCl 4 (dme) and WOCl 3 (thf) 2 by reduction of MoCl 5 and WCl 6 with olefins such as allyltrimethylsilane or cyclopentene are presented.

Enantioselective hydrogenation in water catalysed by rhodium phosphine complexes bound to polyacrylic acid

Abstract The coupling of (2S,4S)-4-diphenylphosphino-2-diphenylphosphino-methylpyrrolidine (PPM) to polyacrylic acid demonstrates an easy way to prepare a water-soluble analogue of the parent ligand. The water solubility of the macromolecular ligand is high and this property can be varied by changing the phosphine to carboxylate ratio on the polymer. Reaction of the macromolecular ligand with bis-norbornadienerhodium(I) triflate [Rh(NBD)2]OTf yield a polymer-bound cationic rhodium phosphine complex catalyst which is active in enantioselective hydrogenation in water or under biphasic conditions (H2O:EtOAc). Hydrogenations of different prochiral enamide precursors give the corresponding aminoacid derivative in moderate to good ee:s, the best enantioselectivity is obtained for α-acetamido cinnamic acid (1a) giving N-acetyl-(R)-phenylalanine (2a) in 89% ee. The enantioselectivity is dependent on the phosphorus loading on the polymer being high at low loading and low at high loading. The enantioselectivity of the catalysts decreases by increasing H2 pressure up to 22 bar where it remains constant. The aqueous catalysts solutions are easily recovered and recycled by phase separation with no loss in enantioselectivity.

Infrared studies on polymer-bound palladium-phosphine complexes

The formation of Pd complexes in phosphinated polystyrene resins has been studied. By the use of Cl2Pd(pyridine)2 as the reacting complex it is shown that, depending on polymer properties such as BET surface area and phosphine content, varying amounts of the complex Cl2Pd(pyridine)(PPS)1 are formed in the resin, together with the complex Cl2Pd(PPS)2. It is found that the monosubstituted complex Cl2Pd(pyridine)(PPS) exists even at formal ratios of PPd > 2. The presence of “inaccessible phosphine groups” in the resin contributes to this effect. Chemical analysis of the polymers treated with varying amounts of Cl2Pd(pyridine)2 has made it possible to calculate the “inaccessible phosphine concentration” in the three different polymers used in this study. This quantity is related to the BET surface area. The polymer with low surface area (1.5 m2/ g) has a higher amount of “inaccessible phosphine groups” than the polymer with the higher surface area (53.5 m2/g). With Cl2Pd(benzonitrile)2 as the reacting complex, no analogous mixed complex is found in the resin. This system was studied by infrared spectroscopy in the M-C1 stretching region and in the spectral range of characteristic vibrations of some extra ligands (CO, 4-cyanopyridine) that were combined with the system. From these measurements we conclude that complexes of the type (PSP)-(PdCl2)n-(PPS) where n ≥ 3 are formed in the resin together with the bisphosphine complex. The role of the species Cl2Pd(pyridine)(PPS) and (PSP)-(PdCl2)n(PPS) in catalytic applications of the resins is briefly discussed.

A novel chiral water-soluble phosphine ligand based on a water-soluble acrylic acid salt

(2S, 4S)-4-diphenylphosphino-2-diphenylphosphinomethyl-pyrrolidine reacts with poly(acrylic acid) to form a macro-ligand useful in biphasic chiral reductions.

A New Highly Active Diphosphane‐Palladium(II) Complex as a Catalyst Precursor for the Heck Reaction

The new diphosphane ligand cis-1,3-bis[(diphenylphosphanyl)methyl]cyclohexane (4) has been prepared and has allowed the synthesis of the palladium complex cis-[Pd(4)(CO2CF3)2] (6). To obtain cis complexation of the diphosphane in 6 the cyclohexane skeleton adopts a chair conformation with a diaxial orientation of the substituents, a structure that has been verified by an X-ray structure determination. This complex efficiently catalyses the vinylation of iodo- and bromobenzenes in high yields. For the best reaction, with methyl acrylate and iodobenzene, a yield of >98% was obtained with an average turnover frequency of 11 760 h−1 and a turnover number of 1 176 000.

Complexes of MoO2Cl2 and WO2Cl2 with the ligands N,N,N′,N′-tetramethylethylenediamine, N,N′-di-t-butyl-1,4-diaza-1,3-butadiene and N,N′-dimethylpiperazine. cis,trans,cis vs all cis coordination in bidentate N-donor complexes of WO2Cl2 and MoO2Cl2. Crystal structures of MoO2Cl2(N,N,N′,N′-tetramethylethylenediamine) and MoO2Cl2(N,N′-DI-t-butyl-1,4-diaza-1,3-butadiene)

Abstract The complexes [MoO2Cl2(But-dab)], [WO2Cl2(But-dab)] (But-dab  N,N′-di-t-butyl-1,4-diaza-1,3-butadiene), [MoO2Cl2(dmp)] and [WO2Cl(dmp)] (dmp  N,N′-dimethylpiperazine) have been prepared and characterized by IR, Raman, 1H and 13C NMR spectroscopy. [MO2Cl2(dmp)] (M  Mo, W) has cis-dichloroligands and [MoO2Cl2(dmp)] shows fluxional behaviour of the coordinated ligand in CH2Cl2 solution, as monitored by 1H NMR spectroscopy. The structures of [MoO2Cl2(tmen)] (tmen  N,N,N′,N′-tetramethylethylenediamine) and [MoO2Cl2(But-dab)] are reported. Both compounds are built up of discrete molecules with distorted octahedral geometry and cis-dioxoligands, the former having the unusual cis-dichloro and the latter the common trans-dichloro arrangement. MoO2Cl2(tmen) has MoO distances of 1.681(4) and 1.697(4) A with an OMoO angle of 103.1(2)°. The trans influence of the oxo-ligands is shown by two different MoCl distances [2.449(2) A trans to O and 2.338(2) A trans to N] and two different MoN distances [2.464(4) A trans to O and 2.278(4) A trans to Cl]. MoO2Cl2(But-dab) has an MoO distance of 1.688(3) and an OMoO angle of 104.5(2)°. The rans-dichloro ligands have equal distances to molybdenum, d(MoCl) = 2.356(1) A. The MoN distances of the nitrogen atoms trans to the oxo groups are 2.399(2) and 2.388(2) A.

OLefin metathesis of alkenylsilanes: II. On the initiation of olefin metathesis with organosilanes

Abstract A study has been made of the cross-metathesis of alkenylsilanes CH 2 CH(CH 2 ) n SiX 3 ( n  1,2; X = CH 3 , Cl, OMe) with ( Z )-2-pentene with WCl 6 as the catalyst precursor. For allyltrimethylsilane (ATMS; n = 1, X = CH 3 ) the reaction proceeds without added co-catalyst but with an induction period. The catalytically-active intermediate in this case is formed by allyl-group transfer from Si to W, as revealed by the formation of CiSiMe 3 . Allyltrichlorosilane and allyltrimethoxysilane requires the addition of an alkylating co-catalyst, e.g. SnMe 4 . Addition of a Lewis acid, e.g. AlCl 3 or AlBr 3 , show that for ATMS removes the induction period and substantially raises the activity. The initial activity of the E/Z -stereoselectivity are affected in a very similar way by the addition of the Lewis acid. The results indicate that the Lewis acid participates in the initiating, propagating and terminating steps of the reaction.

Synthesis, characterisation and crystal structures of the palladium(II) phosphite complexes cis-[PdI2{cis-(iPr2PO)2C6H10}] and trans-[Pd2I4{cis-(iPr2PO)2C6H10}2]

Abstract Treatment of 2 equiv. of a mixture of the diphosphite cis, trans-1,3-(iPr2PO)2C6H10 with [Pd(CO2CF3)2] and sequential addition of an excess of NaI gives the binuclear 16-atom ring chelate complex trans-[Pd2I4{cis-(iPr2PO)2C6H10}2] (1) and the mononuclear complex cis-[PdI2{cis-(iPr2PO)2C6H10}] (2) exclusively. NMR spectroscopy and X-ray crystallography have unambiguously determined the structures of both complexes in solution and in the solid state. The cyclohexane ring orients its 1,3-substituents in a diaxial manner in 2, while the same ring-substituents in 1 are diequatorially oriented.

Biphasic and SAPC hydroformylation catalysed by rhodium phosphines bound to water-soluble polymers

Abstract Coupling of the triphenylphosphine moiety to poly-acrylic acid and poly-ethyleneimine, respectively, afford the macromolecular ligands PAA–PNH and PEI–PNH. Reaction of the ligands with [Rh(CO)2(acac)] give water-soluble complexes that are active as catalyst in the hydroformylation of different olefins. SAP-catalysts based on PAA–PNH are efficient in gas phase hydroformylation of propene and in liquid phase hydroformylation of 1-octene. Hydroformylations under biphasic conditions are very slow but addition of sodiumdodecyl sulphate (SDS) or methanol increases the rate significantly. Catalysts using PEI–PNH as ligands show lower stability and activity in both SAPC and biphasic applications.