Simon Doherty

Iminophosphines: synthesis, formation of 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and N-(pyridin-2-yl)-2-diphenylphosphinoylaniline, coordination chemistry and applications in platinum group catalyzed Suzuki coupling reactions and hydrosilylations

The aprotic and protic bi- and multidentate iminophosphines 2-Ph2PC6H4NCR1R2 (R1=H, R2=Ph=2a; R1=Me R2=Ph=2b; R1=H, R2=2-thienyl=2c; R1=H, R2=C6H4-2-PPh2=2d; R1=H, R2=C6H4-2-OH=2e, R1=H, R2=C6H4-2-OH-3-But=2f; R1=H, R2=CH2C(O)Me=2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine 2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph2PC6H4N(H)CH2C6H4-2-PPh2 (2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph2PC6H4NC(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph2PC6H4NC(H)Ph}ClX] and the imino-diphosphine 2-Ph2PC6H4NC(H)C6H4-PPh2 reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph2PC6H4NC(H)C6H4PPh2}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph2PC6H4NC(Me)CH2C(O)Me reacts with [Ni(PPh3)2Cl2] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph2PC6H4NC(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines 2a–h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd2(OAc)6] giving consistently higher conversions than those formed from [Pd2(dba)3] and [PdCl2(MeCN)2]. Catalysts formed from neutral bi- and terdentate iminophosphines 2a–d gave significantly higher conversions than those formed from their monobasic counterparts 2e–f. Notably, under our conditions the conversions obtained with 2a–c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]2 and 2a–h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines 2e–f giving the highest conversions.

Polymer-supported phosphoramidites: Highly efficient and recyclable catalysts for asymmetric hydrogenation of dimethylitaconate and dehydroamino acids and esters

Abstract Several novel phosphoramidites have been prepared by reaction of the primary amines para -vinylaniline, ortho -anisidine, 2-methoxyphenyl(4-vinylbenzyl)amine, 8-aminoquinoline and 3-vinyl-8-aminoquinoline with ( S )-1,1′-bi-2-naphthylchlorophosphite, in the presence of base. Rhodium(I) complexes of these phosphoramidites catalyse the asymmetric hydrogenation of dimethylitaconate and dehydroamino acids and esters giving ee values up to 95%. Soluble non-cross linked polymers of the para -vinylaniline and 3-vinyl-8-aminoquinoline-based phosphoramidites have been prepared by free radical co-polymerisation with styrene in the presence of AIBN as initiator. The corresponding [Rh(COD)] + complexes serve as recyclable catalysts for the asymmetric hydrogenation dimethylitaconate and dehydroamino acids and esters to give ee values up to 80%.

Marked enantioselectivity enhancements for Diels–Alder reactions in ionic liquids catalysed by platinum diphosphine complexes

Asymmetric Diels–Alder reactions using platinum complexes of BINAP, or of conformationally flexible NUPHOS-type diphosphines, have been compared in dichloromethane and selected ionic liquids. Significant enhancements in the enantioselectivity (Δee ≈ 20%), as well as reaction rate, were achieved in ionic liquids compared with the organic media.

Selectivity for the methoxycarbonylation of ethylene versus COethylene copolymerization with catalysts based on C4-bridged bidentate phosphines and phospholes

Abstract The C 4 -bridged phospholes 11,12-bis(2,3,4,5-tetramethylphospholylmethyl)-9,10-dihydro-9,10-ethano-anthracene ( cis , 4a ; trans , 4b ) and diphosphines 11,12-bis(diphenylphosphinomethyl)-9,10-dihydro-9,10-ethano-anthracene ( cis , 5a ; trans , 5b ) and their corresponding palladium complexes [(PP)PdCl 2 ] ( 6a – d ) have been prepared and characterized. Single-crystal X-ray analyses of 6a – d have been undertaken and they reveal that 4a and b and 5a and b coordinate in a bidentate manner forming seven-membered chelate rings with natural bite angles between 98.62 and 100.30°. The palladium-catalyzed carbonylation of ethylene has been studied using 4a and b and 5a and b . Catalyst mixtures generated from 4a and b , palladium acetate and methanesulfonic acid are selective for the copolymerization of ethylene with carbon monoxide, generating low molecular weight polymers. Surprisingly, the activity of catalyst systems based on cis -( 4a ) is markedly higher than that based on its trans -isomer, 4b . The marked influence of the nature of the four-carbon tether is highlighted by comparative catalyst testing with [{1,4-bis(2,3,4,5-tetramethylphospholyl)butane}Pd(OAc) 2 ], which rapidly decomposes under the conditions used for copolymerization. In contrast, under identical conditions catalyst mixtures formed from 5a and b show a marked dependence of the selectivity on the stereochemistry of the ethano-anthracene tether, the former generating a low molecular weight copolymer while the latter generate mainly methyl propanoate. Interestingly, polyketone generated from catalysts based on bisphosphole 4a has a markedly higher average molecular weight than that formed using its diphenylphosphino counterpart, 5a .

The first insoluble polymer-bound palladium complexes of 2-pyridyldiphenylphosphine: highly efficient catalysts for the alkoxycarbonylation of terminal alkynes

Palladium complexes of 2-pyridyldiphenylphosphine anchored on polystyrene, polymethylmethacrylate and styrene-methylmethacrylate copolymer form highly active heterogeneous catalysts for the alkoxycarbonylation of terminal alkynes with activities approaching those obtained under homogeneous conditions.

The Phosphinoboration Reaction

The synthesis of phosphinoboronate esters containing a single P-B bond is reported, together with preliminary reactivity studies towards a range of organic substrates. These compounds add readily to aldehydes, ketones, aldimines, and α,β-unsaturated enones to give primarily the corresponding 1,2-addition products containing a new P-C bond. The first examples of transition-metal-catalyzed phosphinoborations of C-C multiple bonds in which P-C and B-C bonds are formed in a single step are also disclosed; allenes react by a highly regioselective 1,2-addition whereas terminal alkynes undergo a formal 1,1-addition.

Synthesis of an electron-rich KITPHOS monophosphine, preparation of derived metal complexes and applications in catalysis

This protocol describes the synthesis of a representative example of the electron-rich biaryl-like KITPHOS class of monophosphine, 11-dicyclohexylphosphino-12-phenyl-9,10-dihydro-9,10-ethenoanthracene (H-KITPHOS). The bicyclic architecture of H-KITPHOS is constructed via [4+2] Diels-Alder cycloaddition between 1-(dicyclohexylphosphinoylethynyl)benzene and anthracene. H-KITPHOS monophosphine is prepared via an operationally straightforward three-step procedure and is isolated in an overall yield of ∼55%. The synthesis of palladium and gold precatalysts of H-KITPHOS are also described; the yields of analytically pure complexes are high (75–85% and 85–90%, respectively). The palladium complex of H-KITPHOS forms a highly active catalyst for C-C and C-N cross-coupling of a range of aryl and heteroaryl chlorides and bromides, and the electrophilic Lewis acid gold complex efficiently catalyzes a host of cycloisomerizations. The total time required for the synthesis of H-KITPHOS is 95 h; the preparation of corresponding palladium and gold precatalysts requires an additional 7–8 h, and, if necessary, crystallizations will require a further 48 h.

Efficient and selective oxidation of sulfides in batch and continuous flow using styrene-based polymer immobilised ionic liquid phase supported peroxotungstates

Styrene-based peroxotungstate-modified polymer immobilized ionic liquid phase catalysts [PO4{WO(O2)2}4]@ImPIILP (Im = imidazolium) are remarkably efficient systems for the selective oxidation of sulfides under mild conditions both in batch and as a segmented or continuous flow process using ethanol as the solvent and mobile phase, respectively. The performance of these styrene-based systems has been compared against their ring opening metathesis polymerisation derived counterparts to assess their relative merits. A comparative survey revealed the catalyst supported on N-benzyl imidazolium decorated polymer immobilised ionic liquid to be the most efficient and a cartridge packed with a mixture of [PO4{WO(O2)2}4]@ImPIILP and silica operated as a segmented or continuous flow system giving good conversions and high selectivity for sulfoxide. The immobilised catalyst remained highly active for the sulfoxidation of thioanisole in ethanol with a stable conversion–selectivity profile for up to 8 h under continuous flow operation; for comparison conversions with a mixture of [NBu4]3[PO4{WO(O2)2}4] and silica dropped dramatically after only 15 min as a result of rapid leaching while [PO4{WO(O2)2}4]@ImPIILP prepared from commercially available Merrifield resin also gave consistently lower conversions; these benchmark comparisons serve to underpin the potential benefits of preparing the polymer immobilized ionic liquid supports.

Chemical vapour deposition of electrochromic tungsten oxide films employing volatile tungsten(VI) oxo alkoxide/β-diketonate complexes

Tungsten(VI) oxo alkoxides and tungsten(VI) oxo alkoxide/β-diketonate complexes are volatile precursors for the low-pressure chemical vapour deposition of tungsten oxide electrochromic films, which are characterized by SEM, XPS, XRD and cyclic voltammetry.

Reactions of the anionic phenylphosphinidene cluster [Os3-(µ-H)(µ-PPh)(CO)10]– and its phenylphosphido isomer [Os3-(µ-PHPh)(CO)10]– with electrophiles. Crystal structures of [Os3H(µ-PMePh)(CO)10] and [{Os3H(PPh)(CO)10}2Hg]

Deprotonation of [Os3H(µ-PHPh)(CO)10]3 gives the anion [Os3H(µ-PPh)(CO)10]–4 containing a nucleophilic phosphorus centre which reacts with H+ to regenerate cluster 3 with the Ph group exo to the Os(CO)4 group as in the starting material. However, Mel reacts with anion 4 at the most accessible side of the µ-PPh ligand to give [Os3H(µ-PMePh)(CO)10]6(X-ray structure reported) which has the Ph group endo and the Me group exo to the Os(CO)4 group. Anion 4 reacts with [AuCl(PMe2Ph)] to give [Os3H(µ-PhPAuPMe2Ph)(CO)10]8(Ph probably endo) but the thermally generated isomer of 4, [Os3(µ-PHPh)(CO)10]–5, reacts by the attack of gold at osmium atoms to give [Os3(µ-AuPMe2Ph)(µ-PHPh)(CO)10]9(Ph probably endo) which is isomeric with 8. Compounds with P-Hg bonds are formed by the reaction of 4 with [HgCl(R)](R = Et, PhCH2 or ferrocenyl) or with HgX2(X = Cl, Br or I). The X-ray structure of the Hg-bridged product, [{Os3H(PPh)(CO)10}2Hg], formed from anion 4 and HgX2 or [Fe(C5H5)(C5H4HgCl)], is described. Although the co-ordination of the Hg atom is closely linear [P-Hg-P 171.8(2)°], there are fairly close approaches of O atoms of axial CO ligands to this atom (Hg ⋯ O 2.88 and 2.85 A). The conformations of the two µ3-PPh groups are different.