The Role of Solvent on the Mechanism of Proton Transfer to Hydride Complexes: The Case of the [W3PdS4H3(dmpe)3(CO)]+ Cubane Cluster |
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Authors: | Andrés?G Algarra Manuel?G Basallote Dr Marta Feliz Dr M?Jesús Fernández‐Trujillo Dr Rosa Llusar Dr Vicent?S Safont Dr |
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Institution: | 1. Departmento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, Universidad de Cádiz, Campus Univ. Rio San Pedro. Puerto Real, 11510 Cádiz (Spain), Fax: (+34)?956‐016‐288;2. Department de Químíca Físca i Analítica, Universitat Jaume I, Campus de Riu Sec, Avda. Sos Baynat s/n. 12071, Castelló (Spain), Fax: (+34)?964‐728‐066 |
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Abstract: | The kinetics of reaction of the W3PdS4H3(dmpe)3(CO)]+ hydride cluster ( 1 +) with HCl has been measured in dichloromethane, and a second‐order dependence with respect to the acid is found for the initial step. In the presence of added BF4? the second‐order dependence is maintained, but there is a deceleration that becomes more evident as the acid concentration increases. DFT calculations indicate that these results can be rationalized on the basis of the mechanism previously proposed for the same reaction of the closely related W3S4H3(dmpe)3]+ cluster, which involves parallel first‐ and second‐order pathways in which the coordinated hydride interacts with one and two acid molecules, and ion pairing to BF4? hinders formation of dihydrogen bonded adducts able to evolve to the products of proton transfer. Additional DFT calculations are reported to understand the behavior of the cluster in neat acetonitrile and acetonitrile–water mixtures. The interaction of the HCl molecule with CH3CN is stronger than the W? H???HCl dihydrogen bond and so the reaction pathways operating in dichloromethane become inefficient, in agreement with the lack of reaction between 1 + and HCl in neat acetonitrile. However, the attacking species in acetonitrile–water mixtures is the solvated proton, and DFT calculations indicate that the reaction can then go through pathways involving solvent attack to the W centers, while still maintaining the coordinated hydride, which is made possible by the capability of the cluster to undergo structural changes in its core. |
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Keywords: | cluster compounds density functional calculations palladium tungsten kinetics sulfides |
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