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Titolo:
KINETIC AND MECHANISTIC ASPECTS OF SULFUR ABSTRACTION FROM PD(2)X(2)(MU-S)(MU-DPM)(2) USING DPM OR DPMME [X=HALIDE, DPM=BIS(DIPHENYLPHOSPHINO)METHANE, DPMME=1,1'-BIS(DIPHENYLPHOSPHINO)ETHANE] AND CATALYTIC CONVERSION OF H2S TO H-2
Autore:
WONG TYH; BARNABAS AF; SALLIN D; JAMES BR;
Indirizzi:
UNIV BRITISH COLUMBIA,DEPT CHEM,2036 MAIN MALL VANCOUVER BC V6T 1Z1 CANADA UNIV BRITISH COLUMBIA,DEPT CHEM VANCOUVER BC V6T 1Z1 CANADA
Titolo Testata:
Inorganic chemistry
fascicolo: 9, volume: 34, anno: 1995,
pagine: 2278 - 2286
SICI:
0020-1669(1995)34:9<2278:KAMAOS>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
BIS-PHOSPHORUS LIGANDS; METAL-METAL BONDS; CRYSTAL-STRUCTURE; BIS(DIPHENYLPHOSPHINO)METHANE DPM; DINUCLEAR PALLADIUM(I); HYDROGEN-SULFIDE; COMPLEXES; DERIVATIVES; MONONUCLEAR; PD(I);
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
30
Recensione:
Indirizzi per estratti:
Citazione:
T.Y.H. Wong et al., "KINETIC AND MECHANISTIC ASPECTS OF SULFUR ABSTRACTION FROM PD(2)X(2)(MU-S)(MU-DPM)(2) USING DPM OR DPMME [X=HALIDE, DPM=BIS(DIPHENYLPHOSPHINO)METHANE, DPMME=1,1'-BIS(DIPHENYLPHOSPHINO)ETHANE] AND CATALYTIC CONVERSION OF H2S TO H-2", Inorganic chemistry, 34(9), 1995, pp. 2278-2286

Abstract

Solution kinetic and mechanistic studies were performed on the abstraction of sulfur from Pd(2)X(2)(mu-S)(mu-dpm)(2) [X = Cl (2a), Br (2b),I(2c)] using bis(diphenylphosphino)methane (dpm) to give, respectively, Pd(2)X(2)(dpm)(2) [X = Cl (1a), Br (1b), I (1c)] and dpm(S). The reaction is first-order in both 2 and dpm with the reactivity trend in CHCl3 being X = Cl > Br > I. The activation parameters for the chloridesystem are Delta H-double dagger = 41 +/- 3 kJ mol(-1) and Delta S-double dagger = -127 +/- 10 J K-1 mol(-1), and for the bromide, Delta H-double dagger = 38 +/- 1 kJ mol(-1) and Delta S-double dagger = -144 +/- 4 J K-1 mol(-1), showing the entropy term is dominant in governing reactivity. Low-temperature NMR studies did not reveal the presence ofobservable intermediates. 2b and 1b undergo rapid diphosphine ligand exchange with dpm-d(2); with 2b, prior to any S-abstraction, Pd2Br2(mu-S)(dpm)(dpm-d(2)) (7b) and Pd2Br2(mu-S)(dpm-d(2))(2) (8b) are present, while Pd2Br2(dpm)(dpm-d(2)) (3b) and Pd2Br2(dpm-d(2))(2) (4b) are formed, as well as 1b and dpm(S)-d(2), in the abstraction reaction of 2bwith dpm-d(2). The distribution of products is close to statistical on the basis of the stoichiometries of the reactants. Reaction of 2b with 1,1'-bis(diphenylphosphino)ethane (dpmMe) proceeds in an analogous way generating 1b, Pd2Br2(dpm)(dpmMe) (5b), Pd2Br2(dpmMe)(2) (6b), dpm(S), and dpmMe(S). In contrast, 1b undergoes slow diphosphine ligand exchange with dpmMe to form 5b and 6b; 2b undergoes no ligand exchange with dpmMe prior to the S-abstraction reaction. The findings are rationalized in terms of postulated intermediates and transition states that include formulations with three equivalent diphosphines. No sulfur abstraction occurs on treating 2b with PPh(3), PPh(2)Me, or Ph(2)P(CH2)(3)PPh(2).

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Documento generato il 04/12/20 alle ore 12:59:31