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Titolo:
LIGAND-EXCHANGE REACTIONS IN MOLECULAR-HYDROGEN COMPLEXES OF OSMIUM(II) - A QUANTUM-CHEMICAL STUDY USING DENSITY-FUNCTIONAL THEORY
Autore:
BYTHEWAY I; BACSKAY GB; HUSH NS;
Indirizzi:
UNIV SYDNEY,SCH CHEM SYDNEY NSW 2006 AUSTRALIA UNIV SYDNEY,DEPT BIOCHEM SYDNEY NSW 2006 AUSTRALIA
Titolo Testata:
Journal of physical chemistry
fascicolo: 36, volume: 100, anno: 1996,
pagine: 14899 - 14903
SICI:
0022-3654(1996)100:36<14899:LRIMCO>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOLVENT; SUBSTITUTION; ENERGY; THERMODYNAMICS; DISTRIBUTIONS; DIHYDROGEN; MECHANISMS; SOLVATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
30
Recensione:
Indirizzi per estratti:
Citazione:
I. Bytheway et al., "LIGAND-EXCHANGE REACTIONS IN MOLECULAR-HYDROGEN COMPLEXES OF OSMIUM(II) - A QUANTUM-CHEMICAL STUDY USING DENSITY-FUNCTIONAL THEORY", Journal of physical chemistry, 100(36), 1996, pp. 14899-14903

Abstract

The energetics and mechanism of ligand exchange reactions in a range of molecular hydrogen complexes of Os(II), [Os(NH3)(4)L(z)(eta(2)-H-2)]((z + 2)+) (where L(z) = C5H5-N, CH3CN, NH2OH, NH3, (CH3)(2)CO, H2O CN-, CH3COO-, and Cl-), have been studied using quantum chemical methods. Density functional theory using the BLYP functional was employed todetermine the gas phase equilibrium geometries and the binding energies of H-2 and the trans ligand L(z). The effects of solvation on the energetics were estimated using two variants of the self-consistent reaction field method. Thermal enthalpy and entropy contributions were also calculated, resulting in theoretical estimates of standard free energy changes for the ligand exchange reactions [Os(NH3)(4)H2O(eta(2)-H-2)](2+) + L(z) --> [Os(NH3)(4)L(z)(pi(2)-H-2)]((z + 2)+) + H2O in aqueous solution which were compared with the available experimental data. A reasonable level of qualitative to semiquantitative agreement between theory and experiment is demonstrated, especially when L(z) = Cl-, CH3COO- and (CH3)(2)CO. In agreement with experiment, theory also predicts that [Os(NH3)(4)CN(eta(2)-H-2)](+) will hydrolyze, with H2O replacing H-2 as a ligand with the evolution of H-2 gas. The theoretical studies also suggest that ligand exchange in these systems takes place via an S(N)1 type mechanism, e.g., with the formation of a loosely associated [Os(NH3)(4)-(eta(2)-H-2)](2+) and H2O as transition state. The computed free energy changes of activation are consistent with the experimentally deduced values.

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Documento generato il 24/11/20 alle ore 10:28:27