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Reactivity of the Organometallic fac-[(CO)[sub 3]Re[sup I](H[sub 2]O)[sub 3]][sup +] Aquaion. Kinetic and Thermodynamic Properties of H[sub 2]O Substitution.

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Title:	Reactivity of the Organometallic fac-[(CO)[sub 3]Re[sup I](H[sub 2]O)[sub 3]][sup +] Aquaion. Kinetic and Thermodynamic Properties of H[sub 2]O Substitution.
Authors:	Salignac, Bernadette, Grundler, Pascal V., Cayemittes, Sonia, Frey, Urban, Scopelliti, Rosario, Merbach, André E., Hedinger, Roman, Hegetschweller, Kaspar, Alberto, Roger, Prinz, Ulrich, Reabe, Gerhard, Kölle, Ulrich, Hall, Syd
Source:	Inorganic Chemistry. 6/2/2003, Vol. 42 Issue 11, p3516. 11p. 4 Diagrams, 6 Charts, 5 Graphs.
Subjects:	Organometallic compounds, Water chemistry
Abstract:	The water exchange process on [(CO)[sub 3]Re(H[sub 2]O)[sub 3]][sup +] (1) was kinetically investigated by [sup 17]O NMR. The acidity dependence of the observed rate constant kobs was analyzed with a two pathways model in which k[sub ex] (k[sub ex][sup 298] = (6.3 ± 0.1 × 10[sup -3] S[sup -1]) and k[sub OH] (k[sub OH][sup 298] = 27 ± 1 s[sup -1]) denote the water exchange rate constants on 1 and on the monohydroxo species [(CO)[sub 3]Re¹(H[sub 2]O)[sub 2](OH)], respectively. The kinetic contribution of the basic form was proved to be significant only at [H[sup +]] < 3 × 10[sup -3] M. Above this limiting [H[sup +]] concentration, kinetic investigations can be unambiguously conducted on the triaqua cation (1). The variable temperature study has led to the determination of the activation parameters ΔH[sup ‡][sub ex] = 90 ± 3 kJ mol[sup -1], ΔS[sup ‡][sub ex] = +14 ± 10 J K [sup -1] mol[sup -l], the latter being indicative of a dissociative activation mode for the water exchange process. To support this assumption, water substitution reaction on 1 has been followed by [sup 17]O/¹H/[sup 13]C/[sup 19]F NMR with ligands of various nucleophilicities (TFA, Br[sup -], CH[sub 3]CN, Hbipy[sup +], Hphen[sup +], DMS, TU). With unidentate ligands, except Br[sup -], the mono-, bi-, and tricomplexes were formed by water substitution. With bidentate ligands, bipy and phen, the chelate complexes [(CO)[sub 3]Re(H[sub 2]O)(bipy)]CF[sub 3]SO[sub 3] (2) and [(CO)[sub 3]Re(H[sub 2]O)(phen)](NO[sub 3])[sub 0.5](CF[sub 3]SO[sub 3])[sub 0.5]·H[sub 2]O (3) were isolated and X-ray characterized. For each ligand, the calculated interchange rate constants K[sub i] (2.9 × 10[sup -3] (TFA) < K[sub 1] < 41.5 × 10[sup -3] (TU) s[sup -1]) were found in the same order as the water exchange rate constant k[sub ex], the S-donor ligands being slightly more reactive. This result is indicative of Id mechanism... [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	The water exchange process on [(CO)[sub 3]Re(H[sub 2]O)[sub 3]][sup +] (1) was kinetically investigated by [sup 17]O NMR. The acidity dependence of the observed rate constant kobs was analyzed with a two pathways model in which k[sub ex] (k[sub ex][sup 298] = (6.3 ± 0.1 × 10[sup -3] S[sup -1]) and k[sub OH] (k[sub OH][sup 298] = 27 ± 1 s[sup -1]) denote the water exchange rate constants on 1 and on the monohydroxo species [(CO)[sub 3]Re¹(H[sub 2]O)[sub 2](OH)], respectively. The kinetic contribution of the basic form was proved to be significant only at [H[sup +]] < 3 × 10[sup -3] M. Above this limiting [H[sup +]] concentration, kinetic investigations can be unambiguously conducted on the triaqua cation (1). The variable temperature study has led to the determination of the activation parameters ΔH[sup ‡][sub ex] = 90 ± 3 kJ mol[sup -1], ΔS[sup ‡][sub ex] = +14 ± 10 J K [sup -1] mol[sup -l], the latter being indicative of a dissociative activation mode for the water exchange process. To support this assumption, water substitution reaction on 1 has been followed by [sup 17]O/¹H/[sup 13]C/[sup 19]F NMR with ligands of various nucleophilicities (TFA, Br[sup -], CH[sub 3]CN, Hbipy[sup +], Hphen[sup +], DMS, TU). With unidentate ligands, except Br[sup -], the mono-, bi-, and tricomplexes were formed by water substitution. With bidentate ligands, bipy and phen, the chelate complexes [(CO)[sub 3]Re(H[sub 2]O)(bipy)]CF[sub 3]SO[sub 3] (2) and [(CO)[sub 3]Re(H[sub 2]O)(phen)](NO[sub 3])[sub 0.5](CF[sub 3]SO[sub 3])[sub 0.5]·H[sub 2]O (3) were isolated and X-ray characterized. For each ligand, the calculated interchange rate constants K[sub i] (2.9 × 10[sup -3] (TFA) < K[sub 1] < 41.5 × 10[sup -3] (TU) s[sup -1]) were found in the same order as the water exchange rate constant k[sub ex], the S-donor ligands being slightly more reactive. This result is indicative of Id mechanism... [ABSTRACT FROM AUTHOR]
ISSN:	00201669
DOI:	10.1021/ic0341744