A complete family of isostructural cluster compounds with cubane-like M(3)S(4)M' cores (M = Mo, W; M' = Ni, Pd, Pt): comparative crystallography and electrochemistry

Unusual Square Pyramidal Chalcogenide Mo5 Cluster with Bridging Pyrazolate-Ligands

The family of chalcogenide molybdenum clusters is well presented in the literature by a series of compounds of nuclearity ranging from binuclear to multinuclear articulating octahedral fragments. Clusters actively studied in the last decades were shown to be promising as components of superconducting, magnetic, and catalytic systems. Here, we report the synthesis and detailed characterization of new and unusual representatives of chalcogenide clusters: square pyramidal complexes [{Mo₅(μ₃-Se)ⁱ₄(μ₄-Se)ⁱ(μ-pz)ⁱ₄}(pzH)^t₅]^1+/2+ (pzH = pyrazole, i = inner, t = terminal). Individually obtained oxidized (2+) and reduced (1+) forms have very close geometry (proven by single-crystal X-ray diffraction analysis) and are able to reversibly transform into each other, which was confirmed by cyclic voltammetry. Comprehensive characterization of the complexes, both in solid and in solution, confirms the different charge state of molybdenum in clusters (XPS), magnetic properties (EPR), and so on. DFT calculations complement the diverse study of new complexes, expanding the chemistry of molybdenum chalcogenide clusters.

Hydrolysis of Element (White) Phosphorus under the Action of Heterometallic Cubane-Type Cluster {Mo3PdS4}

Reaction of heterometallic cubane-type cluster complexes—[Mo₃{Pd(dba)}S₄Cl₃(dbbpy)₃]PF₆, [Mo₃{Pd(tu)}S₄Cl₃(dbbpy)₃]Cl and [Mo₃{Pd(dba)}S₄(acac)₃(py)₃]PF₆, where dba—dibenzylideneacetone, dbbpy—4,4′-di-tert-butyl-2,2′-bipyridine, tu—thiourea, acac—acetylacetonate, py—pyridine, with white phosphorus (P₄) in the presence of water leads to the formation of phosphorous acid H₃PO₃ as the major product. The crucial role of the Pd atom in the cluster core {Mo₃PdS₄} has been established in the hydrolytic activation of P₄ molecule. The main intermediate of the process, the cluster complex [Mo₃{PdP(OH)₃}S₄Cl₃(dbbpy)₃]⁺ with coordinated P(OH)₃ molecule and phosphine PH₃, have been detected by ³¹P NMR spectroscopy in the reaction mixture.

Tunable transport and optoelectronic properties of monolayer black phosphorus by grafting PdCl2 quantum dots

The electronic, transport, and optoelectronic properties of monolayer black phosphorus (MLBP) are much influenced by grafting PdCl2 groups, demonstrated here by using density functional theory (DFT) and non-equilibrium Green's function (NEGF) as well as the Keldysh Nonequilibrium Green's Functions (KNEGF) methods. We find that the PdCl2 groups prefer to locate over the furrow site of MLBP and form a planar quadridentate structure of . The PdCl2 groups serve as quantum dots by introducing discrete flat levels between the MLBP valence band and the Fermi level (E f). The conductivity is much lowered after attaching PdCl2 quantum dots, due to the fact that the scattering effect of PdCl2 plays a major role in the process of electron transporting. A threshold voltage is found for the functionalized system with a large density of PdCl2 quantum dots, a valuable clue for exploring current switches. However, no evident threshold voltage is found for the pure MLBP. Electrons permeate easier through the armchair direction compared with the zigzag either in the pure MLBP or in the functionalized composites. More importantly, grafting PdCl2 quantum dots is very beneficial for enhancing photoresponse. The values of photoresponse for the modified species are about 20 times higher than the free MLBP. A significant photoresponse anisotropy is observed for both MLBP and nPdCl2-BP (n = 1, 2, and 4), contrary to the conductivity, the zigzag direction shows much stronger photoresponse than the armchair. All of the aforementioned unique properties make these new two-dimensional (2D) MLBP based materials especially attractive for both electronic and optoelectronic devices.

The first heterocubane cluster with a [W3GaS4] core

The paramagnetic cuboidal clusters [Mo₃(GaCl)(μ₃-S)₄(dppe)₃Cl₃] and [W₃(GaBr)_0.81(μ₃-S)₄(dppe)₃Br₃] were synthesized by treatment of the corresponding triangular clusters [M₃S₄(dppe)₃X₃]X with [Ga(η⁵-C₅Me₅)]₆.

Efficient and Selective N-Methylation of Nitroarenes under Mild Reaction Conditions

Herein, we report a straightforward protocol for the preparation of N,N-dimethylated amines from readily available nitro starting materials using formic acid as a renewable C₁ source and silanes as reducing agents. This tandem process is efficiently accomplished in the presence of a cubane-type Mo₃ PtS₄ catalyst. For the preparation of the novel [Mo₃ Pt(PPh₃ )S₄ Cl₃ (dmen)₃ ]⁺ (3⁺ ) (dmen: N,N'-dimethylethylenediamine) compound we have followed a [3+1] building block strategy starting from the trinuclear [Mo₃ S₄ Cl₃ (dmen)₃ ]⁺ (1⁺ ) and Pt(PPh₃ )₄ (2) complexes. The heterobimetallic 3⁺ cation preserves the main structural features of its 1⁺ cluster precursor. Interestingly, this catalytic protocol operates at room temperature with high chemoselectivity when the 3⁺ catalyst co-exists with its trinuclear 1⁺ precursor. N-heterocyclic arenes, double bonds, ketones, cyanides and ester functional groups are well retained after N-methylation of the corresponding functionalized nitroarenes. In addition, benzylic-type as well as aliphatic nitro compounds can also be methylated following this protocol.

Delivering carbide ligands to sulfide-rich clusters

The propensity of the terminal ruthenium carbide Ru(C)Cl₂(PCy₃)₂ (RuC) to form carbide bridges to electron-rich transition metals enables synthetic routes to metal clusters with coexisting carbide and sulfide ligands.

Heterometallic complexes with cube-type [MTi3N4] cores containing Group 10 metals in a variety of oxidation states

The metalloligand [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)] is capable of stabilizing Group 10 metals in the oxidation states 0,iioriv.

Synthesis, structure and reactivity of cuboidal-type cluster aqua complexes with W3PdS44+core

The reaction of PdCl(2) with [W3S4(H2O)9]4+ in the presence of hypophosphorous acid in 2 M HCl gives cuboidal cluster [W3(PdCl)S4(H2O)9]3+ (1) which undergoes condensation and crystallises from Hpts solutions as edge-linked double cubane cluster [{W3PdS4(H2O)9}2](pts)(8).19H2O (pts = p-toluenesulfonate) (1'). The substitution of Cl- in (1) by different ligands was explored. The Pd atom in the cluster shows an exceptionally high reactivity in the isomerisation of the hydrophosphoryl H2P(O)(OH), HP(O)(OH)2, HPPh(O)(OH) and HPPh2(O) molecules into the corresponding hydroxo tautomers HP(OH)2, P(OH)3, PhP(OH)2 and Ph2P(OH) stabilised by coordination at Pd. The reactions were followed by UV-Vis spectrophotometry and 31P NMR. Formation constants of the 1 : 1 coordination of [M3(PdCl)S4(H2O)9]3+ (M = Mo, W) with HP(OH)2 and As(OH)3 were obtained. The structures of cucurbit[6]uril (C36H36N24O12, CUC[6]) adducts [W3(PdP(OH)3)S4(H2O)8Cl]-(C36H36N24O12)Cl3.12.5H2O (2), and [W3Pd(PhP(OH)2)S4(H2O)7Cl2]2(C36H36N24O12)Cl4.9H2O (3) were determined by single-crystal X-ray diffraction.

Synthesis of the Novel [W3PdS4H3(dmpe)3(CO)]+ Cubane Cluster and Kinetic Studies on the Substitution of Coordinated Hydrides in Acidic Media

Reaction of the incomplete cuboidal [W3S4H3(dmpe)3]+ cluster with a Pd(0) complex under a CO atmosphere produces a rare example of a heterodimetallic hydrido cluster of formula [W3PdS4H3(dmpe)3(CO)]+ ([1]+). There are not significant changes in the W-W bond lengths on going from the trinuclear to the tetranuclear cluster. The average W-W and W-Pd bond distances of 2.769[10] and 2.90[2] A, respectively, are consistent with the presence of single bonds between metal atoms. The heterodimetallic [1]+ complex is easier to oxidize and more difficult to reduce than its trinuclear precursor, which reflects the electron-donating capability of the Pd(CO) fragment. However, mechanistic studies on the reaction of [1]+ with acids show a lower basicity for this complex in comparison with that of its trinuclear precursor, so there is a major electron-density rearrangement within the cluster core upon Pd(CO) coordination. This rearrangement is also reflected in an unusual expansion of the sulfur tetrahedron within the W3PdS4 core with the concomitant elongation of the W-S bond distances by 0.04 A with respect to the analogous bond lengths in the trinuclear precursor. For those thermodynamically favored proton-transfer processes, the reaction mechanism of [1]+ with acids is quite similar to that observed for the incomplete trinuclear cluster, with only small changes in the rate constants. The reaction of [1]+ with HCl in acetonitrile/water mixtures produces [W3PdS4Cl3(dmpe)3(CO)]+ ([2]+) in two kinetically distinguishable steps. Proton transfer occurs in the initial step, in which the W-H bonds are attacked by the acid to yield dihydrogen-bonded adducts that are further attacked by an acetonitrile molecule to give [W3PdS4(CH3CN)3(dmpe)3(CO)]4+ and dihydrogen. The nature of processes involved in the second step are not well-understood with the present data, although it is very likely that these correspond to some secondary processes. In the third resolved step, the coordinated CH3CN ligands in [W3PdS4(CH3CN)3(dmpe)3(CO)]4+ are substituted by Cl- to afford the final [2]+ product. No reaction is observed between [1]+ and HCl in neat acetonitrile, whereas the product of the reaction of [1]+ with HBF4 or Hpts (pts- = p-toluenesulfonate) in this solvent is [W3PdS4(CH3CN)3(dmpe)3(CO)]4+. The reaction occurs in a single kinetic step with a first- (Hpts) or second-order (HBF4) dependence with respect to the acid. The first- and second-order acid dependences can be interpreted through the initial formation of dihydrogen adducts with one or two acid molecules, respectively.

Synthesis of the New, Cubane-like W3S4Co Cluster Core. Completion of the Homologous Series [(η5-Cp‘)3M3S4Co(CO)] (M = Cr, Mo, W)

Reaction between the cluster salts [(eta(5)-Cp')(3)M(3)S(4)][pts] (M = Mo, W; Cp' = methylcyclopentadienyl; pts = p-toluenesulfonate) and [Co(2)(CO)(8)] yielded the electroneutral clusters [(eta(5)-Cp')(3)M(3)S(4)Co(CO)]. The molecular structure of [(eta(5)-Cp')(3)W(3)S(4)Co(CO)] was determined by single-crystal X-ray diffraction methods. The unprecedented 60 electron W(3)S(4)Co cluster completes a homologous series of heterobimetallic clusters, [(eta(5)-Cp')(3)M(3)S(4)Co(CO)] (M = Cr, Mo, W), containing a cubane-like core motif.

Hybrid Cluster-Cages Formed via Cyanometalate Condensation: Cs⊂Co4Ru6S2(CN)12, Co4Ru9S6(CN)9, and Rh4Ru9S6(CN)9 Frameworks

Condensation of cyanometalates and cluster building blocks leads to the formation of hybrid molecular cyanometalate cages. Specifically, the reaction of [Cs subset [CpCo(CN)(3)](4)[CpRu](3)] and [(cymene)(2)Ru(3)S(2)(NCMe)(3)]PF(6) produced [Cs subset [CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)][CpRu](3)](PF(6))(2), Cs subset Co(4)Ru(6)S(2)(2+). Single-crystal X-ray diffraction, NMR spectroscopy, and ESI-MS measurements show that Cs subset Co(4)Ru(6)S(2)(2+ ) consists of a Ru(4)Co(4)(CN)(12) box fused with a Ru(3)S(2) cluster via a common Ru atom. The reaction of PPN[CpCo(CN)(3)] and 0.75 equiv of [(cymene)(2)(MeCN)(3)Ru(3)S(2)](PF(6))(2) in MeCN solution produced [[CpCo(CN)(3)](4)[(cymene)(2)Ru(3)S(2)](3)](PF(6))(2), Co(4)Ru(9)S(6)(2+). Crystallographic analysis, together with NMR and ESI-MS measurements, shows that Co(4)Ru(9)S(6)(2+ ) consists of a Ru(3)Co(4)(CN)(9) "defect box" core, wherein each Ru is fused to a Ru(3)S(2) clusters. The analogous condensation using [CpRh(CN)(3)](-) in place of [CpCo(CN)(3)](-) produced the related cluster-cage Rh(4)Ru(9)S(6)(2+). Electrochemical analyses of both Co(4)Ru(9)S(6)(2+) and Rh(4)Ru(9)S(6)(2+) can be rationalized in the context of reduction at the cluster and the Co(III) subunits, the latter being affected by the presence of alkali metal cations.