Cycloaddition of alkynes to diimino Mo3S4 cubane-type clusters: a combined experimental and theoretical approach

A heterocyclic ligand 4,40-di-tert-butyl-2,20-bipyridine (dbbpy) has been coordinated to the Mo3S4 cluster unit affording the complex [Mo3S4Cl3(dbbpy)3]+ ([1]+) in a one-step ligand-exchange protocol from [Mo3S4(tu)8(H2O)]Cl4 4H2O (tu = thiourea). The new cluster was isolated as [1]PF6 and [1]Cl salts in high yields and the crystal structure of the latter determined by X-ray analysis. The synthetic procedure was extended to tungsten to afford [W3S4Cl3(dbbpy)3]+ ([2]+). Kinetic and NMR studies show that [1]+ reacts with several alkynes to form dithiolene species via concerted [3+2] cycloaddition reactions whereas [2]+ remains inert under similar conditions. The different rates for the reactions of [1]+ are rationalised by computational (DFT) calculations, which show that the more electron-withdrawing the substituents of the alkyne the faster the reaction. The inertness of [2]+ is due to the endergonicity of its reactions, which feature DGr values systematically 5–7 kcal mol 1 more positive than for those of [1]+

Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo3CuS4 Clusters with 4,4′-Di-tert-butyl-2,2′- bipyridine

Treatment of the triangular [Mo3S4Cl3(dbbpy)3]Cl cluster ([1]Cl) with CuCl produces a novel tetrametallic cuboidal cluster [Mo3(CuCl)S4Cl3(dbbpy)3][CuCl2] ([2][CuCl2]), whose crystal structure was determined by X-ray diffraction (dbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine). This species, which contains two distinct types of Cu(I), is the first example of a diimine-functionalized heterometallic M3M′S4 cluster. Kinetics studies on both the formation of the cubane from the parent trinuclear cluster and its dissociation after treatment with halides, supported by NMR, electrospray ionization mass spectrometry, cyclic voltammetry, and density functional theory calculations, are provided. On the one hand, the results indicate that addition of Cu(I) to [1]+ is so fast that its kinetics can be monitored only by cryo-stopped flow at −85 °C. On the other hand, the release of the CuCl unit in [2]+ is also a fast process, which is unexpectedly assisted by the CuCl2 − counteranion in a process triggered by halide (X−) anions. The whole set of results provide a detailed picture of the assembly−disassembly processes in this kind of cluster. Interconversion between trinuclear M3S4 clusters and their heterometallic M3M′S4 derivatives can be a fast process occurring readily under the conditions employed during reactivity and catalytic studies, so their occurrence is a possibility that must be taken into account in future studies

Tрех- и четырехъядерные халькогенидные кластеры молибдена и вольфрама: на пути к новым материалам и катализаторам

The information about electronic structure, redox, magnetic, luminescent, non-linear and catalytic properties of tri- and tetranuclear chalcogenide molybdenum and tungsten clusters is summarized. Prospects of their applications for preparation of new materials for molecular electronics, non-linear optics and catalysis are considered.Суммированы данные по электронному строению, окислительно-восстановительным, магнитным, люминесцентным, нелинейно-оптическим и каталитическим свойствах трех- и четырехъядерных халькогенидных кластеров молибдена и вольфрама. Рассмотрены перспективы применения этого семейства кластерных соединений при создании новых материалов для молекулярной электроники, нелинейной оптики и катализа

Homoleptic Molybdenum Cluster Sulfides Functionalized with Noninnocent Diimine Ligands: Synthesis, Structure, and Redox Behavior

Thiourea (tu) has been coordinated to the Mo3S44+ cluster unit to afford the new cluster compound [Mo3S4(tu)8(H2O)]Cl4·4H2O (1). The high substitutional lability of the thiourea ligands can be exploited to achieve smooth ligand substitution in the Mo3S4 cluster. The reactions of 1 with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) have resulted in new trisubstituted diimino complexes [Mo3S4Cl3L3]+ [L = phen (2), bpy (3)]. The crystal structure of [Mo3S4Cl3(phen)3]Cl·4H2O was determined by X-ray analysis. A solid-state cyclic voltammetry study of 2 shows a ligand-centered reversible two-electron reduction. DFT calculations for [Mo3S4Cl3(phen)3]+ and the 2e-reduced species [Mo3S4Cl3(phen)3]– support our interpretation of the reduction process. Compound 3 undergoes a reversible two-electron reduction, which is more metal-centered on the basis of DFT calculations

Photogeneration of Hydrogen from Water by Hybrid Molybdenum Sulfide Clusters Immobilized on Titania

Two new hybrid molybdenum(IV) Mo3S7 cluster complexes derivatized with diimino ligands have been prepared by replacement of the two bromine atoms of [Mo3S7Br6]2− by a substituted bipyridine ligand to afford heteroleptic molybdenum(IV) Mo3S7Br4(diimino) complexes. Adsorption of the Mo3S7 cores from sample solutions on TiO2 was only achieved from the diimino functionalized clusters. The adsorbed Mo3S7 units were reduced on the TiO2 surface to generate an electrocatalyst that reduces the overpotential for the H2 evolution reaction by approximately 0.3 V (for 1 mA cm−2) with a turnover frequency as high as 1.4 s−1. The nature of the actual active molybdenum sulfide species has been investigated by X-ray photoelectron spectroscopy. In agreement with the electrochemical results, the modified TiO2 nanoparticles show a high photocatalytic activity for H2 production in the presence of Na2S/Na2SO3 as a sacrificial electron donor system.The financial support of the Spanish Ministerio de Economia y Competitividad (MINECO) (Grant CTQ2011-23157), Fundació Bancaixa-UJI (research project P1.1B2013-19), and Generalitat Valenciana (Prometeo/2014/022 and ACOMP/2014/274) is gratefully acknowledged. R.G. and T. L.-V. also acknowledge the MINECO for financial support through projects MAT2012-37676 (Fondos FEDER) and PRI-PIBIN-2011-0816. The authors also thank the Servei Central d’Instrumentació Cientifica (SCIC) of the Universitat Jaume I for providing us with NMR spectroscopy and mass spectrometry facilities and the SSTTI of the Universitat d’Alacant for the XPS measurements (UAUSTI13-05). D.R. thanks the Spanish Ministerio de Economía y Competetividad for a predoctoral fellowship. A.G. thanks the Spanish Ministerio de Ciencia e Innovación (MICINN) for a postdoctoral fellowship and the Russian Foundation for Basic Research (projects N8 12-03-00305, 12-03-33028). E.K. acknowledges support of SB RAS (project #35), the Ministry of Education and Science of the Russian Federation (SP 85.2012.1 and NSh-1183.2014.3), and the Skolkovo Foundation (Grant Agreement for Russian educational organization No.1 on 28.11.2013)

Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo₃CuS₄ Clusters with 4,4′-Di-<i>tert</i>-butyl-2,2′-bipyridine

Treatment of the triangular [Mo₃S₄Cl₃(dbbpy)₃]Cl cluster ([<b>1</b>]­Cl) with CuCl produces a novel tetrametallic cuboidal cluster [Mo₃(CuCl)­S₄Cl₃(dbbpy)₃]­[CuCl₂] ([<b>2</b>]­[CuCl₂]), whose crystal structure was determined by X-ray diffraction (dbbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine). This species, which contains two distinct types of Cu­(I), is the first example of a diimine-functionalized heterometallic M₃M′S₄ cluster. Kinetics studies on both the formation of the cubane from the parent trinuclear cluster and its dissociation after treatment with halides, supported by NMR, electrospray ionization mass spectrometry, cyclic voltammetry, and density functional theory calculations, are provided. On the one hand, the results indicate that addition of Cu­(I) to [<b>1</b>]⁺ is so fast that its kinetics can be monitored only by cryo-stopped flow at −85 °C. On the other hand, the release of the CuCl unit in [<b>2</b>]⁺ is also a fast process, which is unexpectedly assisted by the CuCl₂^– counteranion in a process triggered by halide (X^–) anions. The whole set of results provide a detailed picture of the assembly–disassembly processes in this kind of cluster. Interconversion between trinuclear M₃S₄ clusters and their heterometallic M₃M′S₄ derivatives can be a fast process occurring readily under the conditions employed during reactivity and catalytic studies, so their occurrence is a possibility that must be taken into account in future studies

Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo₃CuS₄ Clusters with 4,4′-Di-<i>tert</i>-butyl-2,2′-bipyridine

Treatment of the triangular [Mo₃S₄Cl₃(dbbpy)₃]Cl cluster ([<b>1</b>]­Cl) with CuCl produces a novel tetrametallic cuboidal cluster [Mo₃(CuCl)­S₄Cl₃(dbbpy)₃]­[CuCl₂] ([<b>2</b>]­[CuCl₂]), whose crystal structure was determined by X-ray diffraction (dbbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine). This species, which contains two distinct types of Cu­(I), is the first example of a diimine-functionalized heterometallic M₃M′S₄ cluster. Kinetics studies on both the formation of the cubane from the parent trinuclear cluster and its dissociation after treatment with halides, supported by NMR, electrospray ionization mass spectrometry, cyclic voltammetry, and density functional theory calculations, are provided. On the one hand, the results indicate that addition of Cu­(I) to [<b>1</b>]⁺ is so fast that its kinetics can be monitored only by cryo-stopped flow at −85 °C. On the other hand, the release of the CuCl unit in [<b>2</b>]⁺ is also a fast process, which is unexpectedly assisted by the CuCl₂^– counteranion in a process triggered by halide (X^–) anions. The whole set of results provide a detailed picture of the assembly–disassembly processes in this kind of cluster. Interconversion between trinuclear M₃S₄ clusters and their heterometallic M₃M′S₄ derivatives can be a fast process occurring readily under the conditions employed during reactivity and catalytic studies, so their occurrence is a possibility that must be taken into account in future studies