Imperial College London

ProfessorJanetPowell

Faculty of MedicineDepartment of Surgery & Cancer

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 8846 7312j.powell

 
 
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Location

 

4N17Charing Cross HospitalCharing Cross Campus

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Summary

 

Publications

Publication Type
Year
to

433 results found

Day AC, Powell JT, 1968, Some reactions of trismethylenemethyl from the photolysis of tricarbonyltrismethylenemethyliron, Chemical Communications (London), Pages: 1241-1243, ISSN: 0009-241X

Journal article

Powell J, Shaw BL, 1968, The relative rates of neutral ligand exchange reactions in some complex iridium(III) hydrides and halides. Iridium(III) hydrido- and halogeno-complexes containing two different tertiary phosphine and/or tertiary arsine ligands, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 617-622, ISSN: 0022-4944

The tertiary phosphine or tertiary arsine ligands (L) in trans-position to hydride in complexes of the type [IrHCl2L3] configuration (I), is labile towards substitution by the strongly bonding phosphine, PMe 2Ph, the other two neutral ligands (L) being inert. Complexes of the type [IrHCl2L2(PMe2Ph)], configuration (II) (L = tertiary phosphine or tertiary arsine; X = Cl), can thus be readily prepared. The reaction goes through a dissociative mechanism, being independent of PMe2Ph concentration. The relative rates of substitution of the ligand L (studied by a 1H n.m.r. method) are in the order L = AsEt3 ≫ PEt3 > PBun3 ≫ PEt2Ph > PBu2Ph, and substitution is faster in [IrHBr2(PEt3)3] than in [IrHCl 2(PEt3)3]. The monohydride-complex [IrHCl 2(PEt2Ph)3], configuration (III), undergoes general displacement of the PEt2Ph ligands by PMe2Ph but the dihydrido-complexes [IrH2X(PEt2Ph)3] [X = Cl, Br, or I] are inert to substitution by PMe2Ph. Treatment of complexes of the type mer-[IrCl3Ars3] (Ars = AsEt 3 or AsEt2Ph) with PMe2Ph gave complexes of the type [IrCl3(Ars)(PMe2Ph)2], configuration (VI), but similar treatment of the corresponding phosphine complexes mer-[IrCl3Phos3] (Phos = PEt3 or PEt 2Ph) gave complexes of type [IrCl3(Phos)(PMe 2Ph)2], configuration (VII). Infrared and n.m.r. data are given and discussed.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XII. Allylic complexes of ruthenium(II), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 159-161, ISSN: 0022-4944

New allylic complexes of ruthenium(II) of the type [Ru(all)2(diolefin)] (all = allyl or 2-methylallyl; diolefin = cyclo-octa-1,5-diene or norbornadiene) are described. The allylic ligands in these complexes are asymmetrically bonded. The complexes react with allyl halides to give halogeno-bridged complexes of the type [Ru2X2(all)2(diolefin)2] (X = Cl or Br). On treatment with triphenylphosphine cyclo-octa-1,5-diene is displaced from [Ru(2-methylallyl)2C8H12] giving [Ru(2-methylallyl)2(PPh3)2]. This in turn reacts with carbon monoxide to give [Ru(CO)3(PPh3)2] and 2,5-dimethylhexa-1,5-diene. Nuclear magnetic resonance and far-infrared data are given.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XIII. Di-μ-chlorodicarbonyldi- (ethylene)dirhodium(I), Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 211-212, ISSN: 0022-4944

[Rh2Cl2(CO)4] and [Rh2Cl 2(C2H4)4] react in benzene solution to give [Rh2Cl2(CO)2(C2H 4)2] in good yield. [Rh2Cl2(CO) 2(C2H4)2] reacts with hydrogen chloride to given an ethylrhodium(III) complex [RhCl2Et(CO)] x which in turn reacts with dimethylphenylphosphine to give [RhCl2Et(CO)(PMe2Ph)2]. Nuclear magnetic resonance and infrared data are given.

Journal article

Powell J, Shaw BL, 1968, Transition metal-carbon bonds. Part XIV. Allylic complexes of rhodium, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 583-596, ISSN: 0022-4944

A convenient synthesis of complexes of the type [Rh2Cl2(all)4] (all = allyl, 1-methyl-, 2-methyl-, or 2-chloro-allyl) is described from the oxidative hydrolysis of [Rh2Cl2(CO)4] in the presence of an allylic chloride (allCl) in aqueous methanol. If the synthesis is carried out in the presence of potassium hydroxide the reactions are much faster and the yields higher; [Rh2Cl2(1-phenylallyl)4] was prepared by this method. With 2-methylallyl chloride and [Rh2Cl2(CO)4] reacting in aqueous methanol at ca. 0° the major product is [Rh2Cl2(2-methylallyl)4] but at 60° only [Rh2Cl2(2,5-dimethylhexa-1,5-diene)2] was isolated. Deuteriation and other studies show that reversible protonation of the 2-methylallyl groups plays an essential part in the formation of the 2,5-dimethylhexa-1,5-diene ligand. Complexes of the type [Rh2Cl2(all)4] contain asymmetrically bonded allylic groups, the nature of which is discussed. Some complexes of the type [Rh2Cl2(all)4] react with alcoholic potassium hydroxide to give an olefin (allH). They can also be used to prepare complexes of the types: [Rh2X2(all)4] (X = Br, I, or Ac); [RhCl(all)2L] and [Rh(all)2py2]+(L = py, PR3, or AsR3); [RhCl(PPh3)3]; [Rh2Cl2(cyclo-octa-1,5-diene)]; [Rh(acac)(all)2]; [Rh(σ-all)(π-all)(C5H5)]; [RhCl2(all)]xand [Rh(all)3]. [Rh(all)3] reacts with Na2PdCl4to give [Rh2Cl2(all)4] and [Pd2Cl2(all)2], or with PPh3to give [Rh(all)(PPh3)2]. Complexes of the types [RhCl2(all)L2] (L = py or PMe2Ph) and [Rh2Cl4(all)2(CO)2], and the complex [RhCl2(C5H5)]xare described. Near-infrared, far-infrared, and nuclear magnetic resonace data are given and discussed.

Journal article

Powell J, Shaw BL, 1967, Transition metal-carbon bonds. Part X. Reactions between allylic palladium halides and tertiary phosphines, triphenylarsine, triphenylstibine, or carbon monoxide, Journal of the Chemical Society A: Inorganic, Physical, and Theoretical Chemistry, Pages: 1839-1851, ISSN: 0022-4944

A series of complexes of the type [PdX(all)L] (X = halogen, all = allylic ligand, and L = tertiary phosphine, triphenylarsine, or triphenylstibine) is described and the asymmetric bonding of the allylic ligand discussed. Several fast rate processes occur in solutions containing allylic palladium halides [Pd2X2(all)2] and neutral ligands L (e.g., phosphines) as the ratio L/Pd is varied from 0 to ca. 2 and these have been studied by n.m.r. spectroscopy at 34°. These fast rate processes involve the conversion of the π-allylic complexes into dynamic σ-allylic systems in which various rotations about carbon-carbon and palladium-carbon bonds and also exchange of the co-ordinated ligand L with free ligand occur. Co-ordination of dimethylphenylphosphine to the palladium atom of [Pd2Cl 2(2-methylallyl)2] has been studied both by n.m.r. and by osmometry and at least two dimethylphenylphosphine ligands can become co-ordinated to the palladium, with the probable formation of [PdCl(σ-2-methylallyl)-(PMe2Ph)2] in solution. Carbon monoxide will also co-ordinate to the palladium atom of [Pd 2Cl2(2-methylallyl)2], the n.m.r. spectrum in chloroform solution corresponding to that of a 'dynamic' σ-2-methylallylic system.

Journal article

Powell J, Shaw BL, 1966, Allylic complexes of rhodium, Chemical Communications (London), Pages: 236-237, ISSN: 0009-241X

Journal article

Nicholson JK, Powell J, Shaw BL, 1966, The mechanism of formation of π-allylic palladium(II) chlorides from sodium chloropalladite, allylic chlorides, and carbon monoxide reacting in aqueous methanol, Chemical Communications (London), Pages: 174-175, ISSN: 0009-241X

Journal article

Lupin MS, Powell J, Shaw BL, 1966, The palladium-chlorine stretching frequencies of bridged chloro-π-allylic palladium(II) complexes, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 1410-1411, ISSN: 0022-4944

Two extremely strong absorption bands at ca. 250 cm.-1in the infrared absorption spectra of di-μ-chloro-diallyldipalladium(II) and its 1-methylallyl and 2-methylallyl analogues are assigned to palladium-chlorine stretching modes of vibration. Previously a band of ca. 360 cm.-1had been incorrectly assigned to these modes.

Journal article

Lupin MS, Powell J, Shaw BL, 1966, Transition metal-carbon bonds. Part VII. The formation of π-allylic-palladium complexes from allenes and palladium halides and the reversed reactions, Journal of the Chemical Society A: Inorganic, Physical, Theoretical, Pages: 1687-1691, ISSN: 0022-4944

The formation of bridged-chloro- 2-chloroprop-2-enyl- and β-(3-chloroprop-1-en-2-yl)allyl-palladium(II) complexes by reacting allene with palladium(II) chloride complexes are described. Similar reactions of methylallene and 1,1-dimethylallene are also described. The resultant bridged-chloro-π-allylic complexes undergo reactions such as metathesis and conversion to monomeric acetylacetonates and also bridged splitting reactions with amines or tertiary phosphines. Under certain conditions, the β-halo π-allylic complexes can eliminate allenes on reaction with ammonia or tertiary phosphines. The mechanisms of the formation of π-allylic complexes from allenes and palladium(II) halide complexes are discussed as are the reversed reactions, e.g., elimination of allene from β-haloallyl complexes. Nuclear magnetic resonance data are given.

Journal article

Powell J, Shaw BL, 1966, Triallylrhodium(III) and a crotyl-butadiene complex of rhodium, Chemical Communications (London), Pages: 323-325, ISSN: 0009-241X

Journal article

Powell J, Shaw BL, 1965, 715. The proton magnetic resonance spectra of some complex platinum hydrides, Journal of the Chemical Society (Resumed), Pages: 3879-3881, ISSN: 0368-1769

Journal article

Powell J, Robinson SD, Shaw BL, 1965, Intermediates in the conversion of π- Into σ-allyic palladium(II) complexes, Chemical Communications (London), Pages: 78-79, ISSN: 0009-241X

Journal article

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