title: Kinetic and DFT studies on the mechanism of C-S bond formation by alkyne addition to the [Mo3S4(H2O)9]4+ cluster.
abstract: Reaction of [Mo3(μ3-S)(μ-S)3] clusters with alkynes usually leads to formation of two C-S bonds between the alkyne and two of the bridging sulfides. The resulting compounds contain a bridging alkenedithiolate ligand, and the metal centers appear to play a passive role despite reactions at those sites being well illustrated for this kind of cluster. A detailed study including kinetic measurements and DFT calculations has been carried out to understand the mechanism of reaction of the [Mo3(μ3-S)(μ-S)3(H2O)9](4+) (1) cluster with two different alkynes, 2-butyne-1,4-diol and acetylenedicarboxylic acid. Stopped-flow experiments indicate that the reaction involves the appearance in a single kinetic step of a band at 855 or 875 nm, depending on the alkyne used, a position typical of clusters with two C-S bonds. The effects of the concentrations of the reagents, the acidity, and the reaction medium on the rate of reaction have been analyzed. DFT and TD-DFT calculations provide information on the nature of the product formed, its electronic spectrum and the energy profile for the reaction. The structure of the transition state indicates that the alkyne approaches the cluster in a lateral way and both C-S bonds are formed simultaneously.
authors.affiliation: Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, Universidad de Cádiz , Apartado 40, Puerto Real, 11510 Cádiz, Spain.
authors.forename: Jose Ángel
authors.initials: JÁ
authors.lastname: Pino-Chamorro
authors.forename: Andrés G
authors.initials: AG
authors.lastname: Algarra
authors.forename: M Jesús
authors.initials: MJ
authors.lastname: Fernández-Trujillo
authors.forename: Rita
authors.initials: R
authors.lastname: Hernández-Molina
authors.forename: Manuel G
authors.initials: MG
authors.lastname: Basallote
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D011789:Quantum Theory; D013440:Sulfides / Q000737:chemistry*
chemical_list: D000480:Alkynes; D056831:Coordination Complexes; D004220:Disulfides; D013440:Sulfides; D008982:Molybdenum; C082964:molybdenum disulfide