Rhenium Complex with Noninnocent Dioxolene Ligand: Combined Experimental and ab Initio Study of [(3,5-di-<i>tert</i>-Bu₂C₆H₂O₂)ReCl₃(OPPh₃)]

Reaction of [ReOCl₃(PPh₃)₂] with 3,5-di-<i>tert</i>-butyl-1,2-benzoquinone (3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-<i>tert</i>-Bu₂C₆H₂O₂)­Re­(OPPh₃)­Cl₃] (<b>1</b>), which was isolated and characterized by elemental analysis, IR, UV–vis spectroscopy, and cyclic voltammetry. In order to clarify the charge state of rhenium and the coordinated dioxolene ligand, X-ray experiments at 150 and 290 K were carried out. The C–O, C–C, and Re–O bond distances at both 150 and 290 K fall between those for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms; an empirical “metrical oxidation state” of the dioxolene ligand was estimated to be −1.5. High-level <i>ab initio</i> calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature of the triplet ground state of complex <b>1</b> corresponding to a superposition of the <i>Re</i>^<i>IV</i>–<i>SQ</i> and <i>Re</i>^<i>V</i>–<i>cat</i> forms. In agreement with the high-level <i>ab initio</i> and DFT calculations, the temperature dependence of the magnetic susceptibility (5–300 K) is well described in the assumption of the triplet ground state, with the anomalously large zero-field splitting (ZFS) arising from the spin–orbit coupling. According to the <i>ab initio</i> calculations, all absorption bands in the visible region of the electronic absorptions spectrum are assigned to the LMCT bands, with significant contribution of the intraligand transition in the most intense band at 555 nm

Rhenium Complex with Noninnocent Dioxolene Ligand: Combined Experimental and ab Initio Study of [(3,5-di-<i>tert</i>-Bu₂C₆H₂O₂)ReCl₃(OPPh₃)]

Reaction of [ReOCl₃(PPh₃)₂] with 3,5-di-<i>tert</i>-butyl-1,2-benzoquinone (3,5-DTBQ) in hot toluene produces a new complex [(3,5-di-<i>tert</i>-Bu₂C₆H₂O₂)­Re­(OPPh₃)­Cl₃] (<b>1</b>), which was isolated and characterized by elemental analysis, IR, UV–vis spectroscopy, and cyclic voltammetry. In order to clarify the charge state of rhenium and the coordinated dioxolene ligand, X-ray experiments at 150 and 290 K were carried out. The C–O, C–C, and Re–O bond distances at both 150 and 290 K fall between those for semiquinolate (3,5-DTBSQ) and catecholate (3,5-DTBCat) forms; an empirical “metrical oxidation state” of the dioxolene ligand was estimated to be −1.5. High-level <i>ab initio</i> calculations (SOC-CASSCF/NEVPT2) revealed a mixed valence nature of the triplet ground state of complex <b>1</b> corresponding to a superposition of the <i>Re</i>^<i>IV</i>–<i>SQ</i> and <i>Re</i>^<i>V</i>–<i>cat</i> forms. In agreement with the high-level <i>ab initio</i> and DFT calculations, the temperature dependence of the magnetic susceptibility (5–300 K) is well described in the assumption of the triplet ground state, with the anomalously large zero-field splitting (ZFS) arising from the spin–orbit coupling. According to the <i>ab initio</i> calculations, all absorption bands in the visible region of the electronic absorptions spectrum are assigned to the LMCT bands, with significant contribution of the intraligand transition in the most intense band at 555 nm

pH-Controlled One Pot Syntheses of Giant Mo₂O₂S₂‑Containing Seleno-Tungstate Architectures

Self-assembly reactions of Na₂WO₄, SeO₂/SeO₃^2–, and [Mo₂O₂(μ-S)₂(H₂O)₆]²⁺ give, depending on the pH value, two new large polyoxometalate complexes: i.e., [(γ-Se₂W₁₄O₅₂)₃­(Mo₂O₂(μ-S)₂­(H₂O)₂)₆]^24– (<b>1</b>) isolated at pH 3.5 and [(γ-Se₂W₁₄O₅₂)₄­(WO₃(H₂O))₈­(W₂O₅)₂­(W₄O₁₂)₂­(Mo₂O₂(μ-S)₂­(H₂O)₂)₄­(Mo₂O₂(μ-S)₂­(SeO₃))₄]^36– (<b>2</b>) isolated at pH 2. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in solution by ESI-MS and NMR

pH-Controlled One Pot Syntheses of Giant Mo₂O₂S₂‑Containing Seleno-Tungstate Architectures

Self-assembly reactions of Na₂WO₄, SeO₂/SeO₃^2–, and [Mo₂O₂(μ-S)₂(H₂O)₆]²⁺ give, depending on the pH value, two new large polyoxometalate complexes: i.e., [(γ-Se₂W₁₄O₅₂)₃­(Mo₂O₂(μ-S)₂­(H₂O)₂)₆]^24– (<b>1</b>) isolated at pH 3.5 and [(γ-Se₂W₁₄O₅₂)₄­(WO₃(H₂O))₈­(W₂O₅)₂­(W₄O₁₂)₂­(Mo₂O₂(μ-S)₂­(H₂O)₂)₄­(Mo₂O₂(μ-S)₂­(SeO₃))₄]^36– (<b>2</b>) isolated at pH 2. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in solution by ESI-MS and NMR

Cd²⁺ Complexation with P(CH₂OH)₃, OP(CH₂OH)₃, and (HOCH₂)₂PO₂^–: Coordination in Solution and Coordination Polymers

The coordination of Cd²⁺ with P­(CH₂OH)₃ (THP) in methanol was followed by ³¹P and ¹¹¹Cd NMR techniques. A cadmium-to-phosphine coordination ratio of 1:3 has been established, and effective kinetic parameters have been calculated. Air oxidation of THP in the presence of CdCl₂ at room temperature produces coordination polymer ³_∞[Cd₃Cl₆(OP­(CH₂OH)₃)₂] (<b>1</b>). The same oxidation reaction at 70 °C gives another coordination polymer, _∞[CdCl₂(OP­(CH₂OH)₃)] (<b>2</b>). Complexes <b>1</b> and <b>2</b> are the first structurally characterized complexes featuring OP­(CH₂OH)₃ as a ligand that acts as a linker between Cd atoms. The addition of NaBPh₄ to the reaction mixture gives coordination polymer _∞[Na₂CdCl₂(O₂P­(CH₂OH)₂)₂(H₂O)₃] (<b>3</b>) with (HOCH₂)₂PO₂^– as the ligand. Coordination polymers <b>1</b>–<b>3</b> have been characterized by X-ray analysis, elemental analysis, and IR spectroscopy

Synthesis and Characterization of [(OH)TeNb₅O₁₈]^6– in Water Solution, Comparison with [Nb₆O₁₉]^8–

Reaction of [Nb₆O₁₉]^8– with H₆TeO₆ in water gives telluropentaniobate [(OH)­Te­Nb₅O₁₈]^6– (<b>1</b>) as single product, which was isolated as Na⁺ and mixed Na⁺/K⁺ salts. Crystal structures were determined for Na₆[(OH)­TeNb₅O₁₈]·15H₂O (<b>Na</b>_<b>6</b><b>-1</b>) and K₆Na­[Nb_5.5­{Te­(OH)}_0.5O_18.5]·26H₂O (<b>K</b>_<b>6</b><b>Na-1</b>). Formation of <b>1</b> was monitored with electrospray ionization mass spectrometry (ESI-MS) and ¹²⁵Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)­Te­Nb₅O₁₈]^6– and [Nb₆O₁₉]^8– in borate buffer. No condensation or degradation products were detected. Reactions of <b>1</b> with {Cp*Rh}²⁺ sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by ¹²⁵Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}²⁺ to different {M₃O₃} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na₃[{Cp*Rh}₂­TeNb₅O₁₉]·24H₂O (<b>Cp*</b>_<b>2</b><b>Rh</b>_<b>2</b><b>-1</b>) with two {Cp*Rh}²⁺ fragments capping the opposing faces of the Lindqvist anion

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

Nonconventional Three-Component Hierarchical Host–Guest Assembly Based on Mo-Blue Ring-Shaped Giant Anion, γ‑Cyclodextrin, and Dawson-type Polyoxometalate

In this communication, we report on a noteworthy hybrid supramolecular assembly built from three functional components hierarchically organized through noncovalent interactions. The one-pot synthesis procedure leads to the formation of large Mo-blue ring-shaped anion {Mo₁₅₄}, which contains the supramolecular adduct based on the symmetric encapsulation of the Dawson-type [P₂W₁₈O₆₂]^6– anion by two γ-cyclodextrin units. Such a nanoscopic onion-like structure, noted [P₂W₁₈O₆₂]@2γ-CD@{Mo₁₅₄} has been characterized by single-crystal X-ray diffraction, thus demonstrating the capability of the giant inorganic torus to develop relevant supramolecular chemistry, probing the strong affinity of the inner and outer faces of the γ-CD for the polyoxometalate surfaces. Furthermore, interactions and behavior in solution have been studied by multinuclear NMR spectroscopy, which supports specific interactions between γ-CD and POM units. Finally, the formation of this three-component hybrid assembly from one-pot procedure, in water and using nearly stoichiometric conditions, is discussed in terms of the driving forces orchestrating this highly efficient multilevel recognition process

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