Experimental and computational investigations of phosphine exchange in 15-electron [CrCpCl2(PR3)] systems by stopped-flow and density functional calculations: a single-state SN2 mechanism - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of the Chemical Society Dalton Transactions Année : 1999

Experimental and computational investigations of phosphine exchange in 15-electron [CrCpCl2(PR3)] systems by stopped-flow and density functional calculations: a single-state SN2 mechanism

Résumé

The exchange of the phosphine ligand on the half-sandwich 15-electron, spin quartet [CrCpCl2L] system has been investigated experimentally by stopped-flow kinetics with visible detection and theoretically by calculations with DFT methods on the PH3 self-exchange model system. The exchange of PMePh2 with PMe3 follows clean second- order kinetics with the activation parameters ΔH ‡ = 7.0(2) kcal mol–1 and ΔS ‡ = –24.3(8) cal K–1 mol–1, consistent with an associative exchange. The rate constant for the exchange of L with PMe3 in [CrCpCl2L] at room temperature varies only within a factor of 8 for the series of complexes with L = PPh3, PMePh2, PMe2Ph, PEt3, or η1-dppe. The computational work showed that the PH3 self-exchange process occurs via a symmetric transition state along the spin quartet hypersurface, without crossover to the spin doublet state. The optimized transition state corresponds to a first-order saddle point with Cr–P distances of 3.190 and 3.174 Å, located 7.6 kcal mol–1 above the [CrCpCl2(PH3)] (spin quartet) + PH3 combination, or 13.6 kcal mol–1 below the [CrCpCl2(PH3)2] doublet minimum. Thus, the phosphine exchange reaction can be classified as a classical SN2 process.
Fichier principal
Vignette du fichier
138-10.1039-a809129c-Accepted.pdf (463.09 Ko) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-03304774 , version 1 (04-10-2021)

Identifiants

Citer

Edmond Collange, David Duret, Rinaldo Poli. Experimental and computational investigations of phosphine exchange in 15-electron [CrCpCl2(PR3)] systems by stopped-flow and density functional calculations: a single-state SN2 mechanism. Journal of the Chemical Society Dalton Transactions, 1999, 1999 (6), pp.875-880. ⟨10.1039/A809129C⟩. ⟨hal-03304774⟩
13 Consultations
32 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More