title: On the Critical Effect of the Metal (Mo vs. W) on the [3+2] Cycloaddition Reaction of M3 S4 Clusters with Alkynes: Insights from Experiment and Theory.
abstract: Whereas the cluster [Mo3 S4 (acac)3 (py)3 ](+) ([1](+) , acac=acetylacetonate, py=pyridine) reacts with a variety of alkynes, the cluster [W3 S4 (acac)3 (py)3 ](+) ([2](+) ) remains unaffected under the same conditions. The reactions of cluster [1](+) show polyphasic kinetics, and in all cases clusters bearing a bridging dithiolene moiety are formed in the first step through the concerted [3+2] cycloaddition between the C≡C atoms of the alkyne and a Mo(μ-S)2 moiety of the cluster. A computational study has been conducted to analyze the effect of the metal on these concerted [3+2] cycloaddition reactions. The calculations suggest that the reactions of cluster [2](+) with alkynes feature ΔG(≠) values only slightly larger than its molybdenum analogue, however, the differences in the reaction free energies between both metal clusters and the same alkyne reach up to approximately 10 kcal mol(-1) , therefore indicating that the differences in the reactivity are essentially thermodynamic. The activation strain model (ASM) has been used to get more insights into the critical effect of the metal center in these cycloadditions, and the results reveal that the change in reactivity is entirely explained on the basis of the differences in the interaction energies Eint between the cluster and the alkyne. Further decomposition of the Eint values through the localized molecular orbital-energy decomposition analysis (LMO-EDA) indicates that substitution of the Mo atoms in cluster [1](+) by W induces changes in the electronic structure of the cluster that result in weaker intra- and inter-fragment orbital interactions.
authors.affiliation: Departmento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Campus Universitario de Puerto Real, Universidad de Cádiz, 11510 Puerto Real, Cádiz (Spain).
authors.forename: Emilio
authors.initials: E
authors.lastname: Bustelo
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Novosibirsk State University, 630090 Novosibirsk (Russia).
authors.forename: Artem L
authors.initials: AL
authors.lastname: Gushchin
authors.affiliation: Departmento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Campus Universitario de Puerto Real, Universidad de Cádiz, 11510 Puerto Real, Cádiz (Spain).
authors.forename: M Jesús
authors.initials: MJ
authors.lastname: Fernández-Trujillo
authors.affiliation: Departmento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Campus Universitario de Puerto Real, Universidad de Cádiz, 11510 Puerto Real, Cádiz (Spain). manuel.basallote@uca.es.
authors.forename: Manuel G
authors.initials: MG
authors.lastname: Basallote
authors.affiliation: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm (Sweden). andres.algarra@uca.es.
authors.forename: Andrés G
authors.initials: AG
authors.lastname: Algarra
keywords: cluster compounds; cycloaddition; density functional calculations; kinetics; reaction mechanisms