A {Co4O4} Cubane Incorporated within a Polyoxoniobate Cluster

A novel octacobalt‐containing polyoxoniobate, Na₆K₁₂[H₂Co₈O₄(Nb₆O₁₉)₄]?39 H₂O, has been prepared by a combination of hydrothermal and diffusion methods. The polyanion [H₂Co₈O₄(Nb₆O₁₉)₄]^18? incorporates a tetrameric assembly of Lindqvist‐type [Nb₆O₁₉]^8? fragments trapping a {Co^II₄Co^III₄} cluster which comprises a central {Co^III₄O₄} cubane core, surrounded by another four Co^II ions linkers. Furthermore, magnetic measurements show that the compound exhibits antiferromagnetic interactions.     

Polyoxotungstate Archetype {P4W27} and its 3d Derivatives

The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C₆H₅P^VO)₂P₄W₂₄O₉₂]¹⁶⁻ to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with Mn^II and Cu^II induce the formation of the previously unknown polyoxotungstate archetype {P₄W₂₇}, isolated as salts of the polyanions [Na⊂{Mn^II(H₂O)}{WO(H₂O)}P₄W₂₆O₉₈]¹³⁻ ( 1 ) and [K⊂{Cu^II(H₂O)}{W(OH)(H₂O)}P₄W₂₇O₉₉]¹⁴⁻ ( 2 ), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).     

Assembly of Large Purely Inorganic Ce‐Stabilized/Bridged Selenotungstates: From Nanoclusters to Layers

A versatile one‐pot strategy was used to synthesize two large, purely inorganic selenotungstates, nanocluster K₆Na₁₆[Ce₆Se₆W₆₇O₂₃₀(OH)₆(H₂O)₁₇]?47 H₂O ( 1 ) and layer K₉Na₅Ce(H₂O)₄[Ce₆Se₁₀W₅₁O₁₈₇(OH)₇(H₂O)₁₈]?45 H₂O ( 2 ), by combining cerium centers and SeO₃^2? heteroanion templates. Compound 1 displays a Ce‐stabilized hexameric nanocluster with one rhombus‐like {W₄O₁₅(OH)₃} unit in the center, whereas compound 2 is the first example of a Ce‐bridged layer selenotungstate network based on linkage of the unusual {Ce₆Se₁₀W₅₁O₁₈₇(OH)₇(H₂O)₁₈} clusters and additional Ce(H₂O)₄ fragments via Ce‐O‐Se bridges. The compounds were characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, powder and single‐crystal X‐ray diffraction, and electrospray ionization mass spectrometry. Moreover, the electrochemical property of compound 1 was also investigated.     

Two Organic–Inorganic Hybrid 3D {P5W30}‐Based Heteropolyoxotungstates with Transition‐Metal/Ln–Carboxylate–Ln Connectors

Two unique organic–inorganic hybrid polyoxometalates constructed from Preyssler‐type [Na(H₂O)P₅W₃₀O₁₁₀]^14? ({P₅W₃₀}) subunits and TM/Ln–carboxylate–Ln connectors (TM=transition metal, Ln=lanthanide), KNa₇[{Sm₆Mn(μ‐H₂O)₂(OCH₂COO)₇(H₂O)₁₈}{Na(H₂O)P₅W₃₀O₁₁₀}] ? 22 H₂O ( 1 ) and K₄[{Sm₄Cu₂(gly)₂(ox)(H₂O)₂₄}{NaP₅W₃₀O₁₁₀}]Cl₂ ? 25 H₂O ( 2 ; gly=glycine, ox=oxalate) have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, UV/Vis‐NIR spectra, thermogravimetric analyses, power X‐ray diffraction, and single‐crystal X‐ray diffraction. Compound 1 displays one interesting 3D framework built by three types of subunits, {P₅W₃₀}, [Sm₂Mn(μ‐H₂O)₂(OCH₂COO)₂(H₂O)₅]⁴⁺, and [Sm₄(OCH₂COO)₅ (H₂O)₁₃]²⁺, whereas 2 also manifests the other intriguing 3D architecture created by three types of subunits, {P₅W₃₀}, [SmCu(gly)(H₂O)₈]⁴⁺, and [Sm₂(ox)(H₂O)₈]⁴⁺. To our knowledge, 1 and 2 are the first 3D frameworks that contain {P₅W₃₀} units and TM/Ln–carboxylate–Ln connectors. The fluorescent properties of 1 and 2 have been investigated.     

Unprecedented Selenium and Lanthanide Simultaneously Bridging Selenotungstate Aggregates Stabilized by Four Tetra‐vacant Dawson‐like {Se2W14} Units

In the presence of the larger [H₂N(CH₃)₂]⁺ and K⁺ counter cations as structure‐stabilizing agents, a class of unprecedented selenium and lanthanide (Ln) simultaneously bridging tetra‐vacant Dawson‐like selenotungstate aggregates [H₂N(CH₃)₂]₂Na₉K₂H₁₉{[Ln₄W₄ Se₄O₂₂(H₂O)₅](Se₂W₁₄O₅₂)₂}₂ ⋅ 60 H₂O [Ln=Tb^III ( 1 ), Dy^III ( 2 ), Ho^III ( 3 ), Er^III ( 4 ), Tm^III ( 5 ), Yb^III ( 6 )] have been obtained by the one‐pot assembly reaction of Na₂WO₄ ⋅ 2 H₂O, Ln(NO₃)₃ ⋅ 6 H₂O, and Na₂SeO₃ under moderately acidic aqueous conditions and the complexes were structurally characterized by elemental analyses, IR spectra, single‐crystal X‐ray diffraction, powder X‐ray diffraction (PXRD), and thermogravimetric (TG) analyses. It should be noted that the appropriate molar ratio of Se/W is extremely important in the formation of 1 – 6 and can effectively ameliorate the yield of 1 – 6 . Moreover, dimethylamine hydrochloride is also indispensable and plays a considerably important role in improving the solubility of Ln ions and stabilizing the structures of 1 – 6 . The main polyoxoanion skeletons of 1 – 6 are constructed from two sandwich‐type tetra‐vacant Dawson‐like {[Ln₄W₄Se₄O₂₂(H₂O)₅](Se₂W₁₄O₅₂)₂}¹⁶⁻ half‐units linked through two W‐O‐Ln bridges. The sandwich‐type half‐unit comprises two tetra‐vacant Dawson‐like [Se₂W₁₄O₅₂]¹²⁻ fragments encapsulating a unique dodecanuclear Se‐Ln‐W [Ln₄W₄Se₄O₂₂(H₂O)₅]⁸⁺ oxo cluster. Their solid‐state visible and NIR fluorescent properties and lifetime decay behaviors were measured and their solid‐state luminescent spectra mainly demonstrate the characteristic emission bands of Ln³⁺ ions. Moreover, the dominant wavelengths, the color purity, and correlated color temperatures of 1 – 5 have been also calculated. In addition, the luminous flux values of 1 – 5 are 2031, 6992, 3071, 921, and 477 lumen, respectively.     

Three Cobalt(II)‐Linked {P8W48} Network Assemblies: Syntheses,Structures, and Magnetic and Photocatalysis Properties

Three cobalt(II)‐containing tungstophosphate compounds, Na₈Li₈Co₅[Co_5.5(H₂O)₁₉P₈W_48.5O₁₈₄] ? 60 H₂O ( 1 ), K₂Na₄Li₁₁Co₅[Co₇(H₂O)₂₈P₈W₄₈O₁₈₄]Cl ? 59 H₂O ( 2 ), and K₂Na₄LiCo₁₁[Co₈(H₂O)₃₂P₈W₄₈O₁₈₄](CH₃COO)₄Cl ? 47 H₂O ( 3 ), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, elemental analyses, and magnetic measurements. The pH value impacts the formation of distinct cobalt‐linked frameworks. The cyclic cavity of the polyanion accommodates 5.5, 7, and 8 cobalt ions in 1 , 2 , and 3 , respectively. In compounds 1 and 2 , each {Co_5.5P₈W₄₈} and {Co₇P₈W₄₈} fragment links to four others through multiple {Co‐O‐W} coordination bonds to generate a two‐dimensional network. Compound 3 can be considered as a 3D network based on the {Co‐O‐W} coordination bonds and the {Co₃(CH₃COO)₂(H₂O)₁₀} linkers between the {P₈W₄₈} fragments. Interestingly, acetate ligands have been employed to form the {Co₃(CH₃COO)₂(H₂O)₁₀} unit, thereby inducing the construction of a 12‐connected framework. To the best of our knowledge, compound 3 contains the largest‐ever number of cobalt ions in a {P₈W₄₈}‐based polyoxometalate when counterions are taken into account and the {P₈W₄₈} unit shows the highest number of connections thanks to the carboxyl bridges. The UV/Vis diffuse reflectance spectra of these powder samples indicate that the corresponding well‐defined optical absorption associated with E_g can be assessed at 2.58, 2.48, and 2.73 eV and reveal the presence of an optical band gap. The photocatalytic H₂ evolution activities of these {P₈W₄₈}‐based compounds are evaluated.     

Self‐Assembly of [B‐SbW9O33]9− Subunit with Transition Metal Ions (Mn2+, Cu2+, Co2+) in Aqueous Solution: Syntheses,Structures and Magnetic Properties of Sandwich Type Polyoxometalates with Subvalent SbIII Heteroatom

Rational self‐assembly of Sb₂O₃ and Na₂WO₄, or (NH₄)₁₈[NaSb₉W₂₁O₈₆] with transition‐metal ions (Mn²⁺, Cu²⁺, Co²⁺), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na₂H₂[Mn_2.5W_1.5(H₂O)₈(B‐β‐SbW₉O₃₃)₂]?32 H₂O (1) , Na₄H₇[Na₃(H₂O)₆Mn₃(μ‐OAc)₂(B‐α‐SbW₉O₃₃)₂]?20 H₂O (OAc=acetate anion) (2) , NaH₈[Na₂Cu₄Cl(B‐α‐SbW₉O₃₃)₂]?21 H₂O (3) , Na₈K[Na₂K(H₂O)₂{Co(H₂O)}₃(B‐α‐SbW₉O₃₃)₂]? 10 H₂O (4) , and Na₅H[{Co(H₂O)₂}₃W(H₂O)₂(B‐β‐SbW₉O₃₃)₂]?11.5 H₂O (5) . These structures are determined by using the X‐ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two [B‐β‐SbW₉O₃₃]^9? building units, whereas 2 , 3 , and 4 consist of two isomerous [B‐α‐SbW₉O₃₃]^9? building blocks, which are all linked by different transition‐metal ions (Mn²⁺, Cu²⁺, or Co²⁺) with different quantitative nuclearity. It should be noted that compound 2 represents the first one‐dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate‐bridging ligands. Additionally, 3 is constructed from sandwiched anions [Na₂Cu₄Cl(B‐α‐SbW₉O₃₃)₂]^9? linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion [{Co(H₂O)₂}₃W(H₂O)₂(B‐β‐SbW₉O₃₃)₂]^6? linked by Co²⁺ and Na⁺ ions. EPR studies performed at 110 K and room temperature reveal that the metal cations (Mn²⁺, Cu²⁺, Co²⁺) reside in a square‐pyramidal geometry in 2 , 3 , and 4 . The magnetic behavior of 1 – 4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J=?0.552 cm^?1 in 2 .     

Following the Reaction of Heteroanions inside a {W18O56} Polyoxometalate Nanocage by NMR Spectroscopy and Mass Spectrometry

By incorporating phosphorus(III)‐based anions into a polyoxometalate cage, a new type of tungsten‐based unconventional Dawson‐like cluster, [W₁₈O₅₆(HP^IIIO₃)₂(H₂O)₂]^8?, was isolated, in which the reaction of the two phosphite anions [HPO₃]^2? within the {W₁₈O₅₆} cage could be followed spectroscopically. As well as full X‐ray crystallographic analysis, we studied the reactivity of the cluster using both solution‐state NMR spectroscopy and mass spectrometry. These techniques show that the cluster undergoes a structural rearrangement in solution whereby the {HPO₃} moieties dimerize to form a weakly interacting (O₃PH???HPO₃) moiety. In the crystalline state the cluster exhibits a thermally triggered oxidation of the two P^III template moieties to form P^V centers (phosphite to phosphate), commensurate with the transformation of the cage into a Wells–Dawson {W₁₈O₅₄} cluster.     

Magnetothermal studies of a series of coordination clusters built from ferromagnetically coupled {Mn(II) (4)Mn(III) (6)} supertetrahedral units

Three high‐nuclearity mixed valence manganese^II/III coordination clusters, have been synthesised, that is, [Mn ^III ₆Mn ^II ₄(μ₃‐O)₄(HL¹)₆(μ₃‐N₃)₃(μ₃‐Br)(Br)](N₃)_0.7/(Br)_0.3 ? 3 MeCN ? 2 MeOH ( 1 ) (H₃L¹=3‐methylpentan‐1,3,5‐triol), [Mn^III₁₁Mn^II₆(μ₄‐O)₈(μ₃‐Cl)₄(μ,μ₃‐O₂CMe)₂(μ,μ‐L²)₁₀Cl_2.34(O₂CMe)_0.66(py)₃(MeCN)₂] ? 7 MeCN ( 2 ) (H₂L²=2,2‐dimethyl‐1,3‐propanediol and py is pyridine), and [Mn^III₁₂Mn^II₇(μ₄‐O)₈(μ₃‐η¹N₃)₈(HL³)₁₂(MeCN)₆]Cl₂ ? 10 MeOH ? MeCN ( 3 ) (H₃L³=2,6‐bis(hydroxymethyl)‐4‐methylphenol) with high ground‐spin states, S=22, 28±1, and 83/2, respectively; their magnetothermal properties have been studied. The three compounds are based on a common supertetrahedral building block as seen in the Mn₁₀ cluster. This fundamental magnetic unit is made up of a tetrahedron of Mn^II ions with six Mn^III ions placed midway along each edge giving an inscribed octahedron. Thus, the fundamental building unit as represented by compound 1 can be described as a Mn₁₀ supertetrahedron. Compounds 2 and 3 correspond to two such units joined by a common edge or vertex, respectively, resulting in Mn₁₇ and Mn₁₉ coordination clusters. Magnetothermal studies reveal that all three compounds show interesting long‐range magnetic ordering at low temperature, originating from negligible magnetic anisotropy of the compounds; compound 2 shows the largest magnetocaloric effect among the three compounds. This is as expected and can be attributed to the presence of a small magnetic anisotropy, and low‐lying excited states in compound 2 .     

Assembly of Cerium(III)‐Stabilized Polyoxotungstate Nanoclusters with SeO32−/TeO32− Templates: From Single Polyoxoanions to Inorganic Hollow Spheres in Dilute Solution

A versatile one‐pot strategy was employed to synthesize three cerium(III)‐stabilized polyoxotungstates nanoclusters by combining cerium linkers and SeO₃^2?/TeO₃^2? heteroanion templates: K₃₂Na₁₆[{(XO₃)W₁₀O₃₄}₈{Ce₈(H₂O)₂₀}(WO₂)₄‐ (W₄O₁₂)] ? n H₂O [X=Se, n=81 ( 1 ); X=Te, n=114 ( 2 )] and K₁₂Na₂₂[{(SeO₃)W₁₀O₃₄}₈{Ce₈(H₂O)₂₀}(WO₂)₄‐ {(W₄O₆)Ce₄(H₂O)₁₄(SeO₃)₄(NO₃)₂}] ? 79 H₂O ( 3 ), which are the first lanthanide‐containing polyoxotungstates with selenium or tellurium heteroatoms. The three clusters were characterized by single‐crystal X‐ray structure analysis, IR spectroscopy, thermogravimetric/differential thermal analysis, UV/Vis spectroscopy, ESI‐MS, and X‐ray photoelectron spectroscopy. Their electrochemical, photoluminescence, and magnetic properties were investigated. Their behavior in solution was studied by transmission electron microscopy, which showed that their single polyoxoanions assemble into intact, uniform‐sized, purely inorganic hollow spheres in dilute water/acetone solution.     

High-nuclearity Ni-substituted polyoxometalates: a series of poly(polyoxotungstate)s containing 20–22 nickel centers

Three high‐nuclearity Ni‐substituted polyoxotungstates (POTs)—[Ni(enMe)₂(H₂O)₂]₂[Ni(H₂O)₆]₂‐ [Ni(enMe)₂][Ni(H₂O)₂]_1.5[HNi₂₀X₄W₃₄‐ (OH)₄O₁₃₆(H₂O)₆(enMe)₈] ? 11 H₂O ( 3 ), [Ni(en)₂(H₂O)]₂[H₈Ni₂₁X₄W₃₄(OH)₄‐ O₁₃₆(en)₁₀(H₂O)₅] ? 22 H₂O ( 4 ), and [Ni‐(enMe)₂]₂[H₆Ni₂₂X₄W₃₄(OH)₄O₁₃₆(H₂O)₆(enMe)₁₀] ? 18 H₂O ( 5 ), in which en=ethylenediamine, enMe=1,2‐diaminopropane, X=0.5 P+0.5 Ge—were made under hydrothermal conditions and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The structures of 3 – 5 can be viewed as novel derivatives of [H₆Ni₂₀P₄W₃₄(OH)₄O₁₃₆(enMe)₈‐ (H₂O)₆] ? 12 H ₂O ( 1 ) and [Ni(en)₂‐ (H₂O)]₂[H₈Ni₂₀P₄W₃₄(OH)₄O₁₃₆(en)₉‐ (H₂O)₄] ? 16 H ₂O ( 2 ), which both contain 20 nickel ions per structural unit. Compound 3 is the first example of a 1D cluster chain constructed from Ni₂₀‐substituted polyanions [HNi₂₀X₄‐ W₃₄(OH)₄O₁₃₆(H₂O)₆(enMe)₈]^11? and [Ni(enMe)₂]²⁺ bridges. Compound 4 is a novel cluster–organic chain built by Ni₂₁‐substituted polyanions [H₈Ni₂₁X₄W₃₄(OH)₄O₁₃₆(en)₁₀(H₂O)₅]^4? and en molecule bridges. Compound 5 is a discrete POT with 22 Ni centers, and is not only the largest nickel‐substituted POT, but also contains the highest number of nickel ions in one polyanion to date. Magnetic measurements illustrate that overall ferromagnetic interactions exist in 1 – 5 . The magnetic behavior of 1 and 2 was theoretically simulated by the MAGPACK magnetic program package.     

Strategic Capture of the {Nb7} Polyoxometalate

Group V Nb-polyoxometalate (Nb-POM) chemistry generally lacks the elegant pH-controlled speciation exhibited by group VI (Mo, W) POM chemistry. Here three Nb-POM clusters were isolated and structurally characterized; [Nb₁₄O₄₀(O₂)₂H₃]¹⁴⁻, [((UO₂)(H₂O))₃Nb₄₆(UO₂)₂O₁₃₆H₈(H₂O)₄]²⁴⁻, and [(Nb₇O₂₂H₂)₄(UO₂)₇(H₂O)₆]²²⁻, that effectively capture the aqueous Nb-POM species from pH 7 to pH 10. These Nb-POMs illustrate a reaction pathway for control over speciation that is driven by counter-cations (Li⁺) rather than pH. The two reported heterometallic POMs (with UO₂²⁺ moieties) are stabilized by replacing labile H₂O/HO−Nb=O with very stable O=U=O. The third isolated Nb-POM features cis-yl-oxos, prior observed only in group VI POM chemistry. Moreover, with these actinide-heterometal contributions to the burgeoning Nb-POM family, it now transects all major metal groups of the periodic table.     

Aluminum‐ and Gallium‐Containing Open‐Dawson Polyoxometalates

Al‐ and Ga‐containing open‐Dawson polyoxometalates (POMs), K₁₀[{Al₄(μ‐OH)₆}{α,α‐Si₂W₁₈O₆₆}] · 28.5H₂O ( Al₄ ‐ open ) and K₁₀[{Ga₄(μ‐OH)₆}(α,α‐Si₂W₁₈O₆₆)] · 25H₂O ( Ga₄ ‐ open ) were synthesized by the reaction of trilacunary Keggin POM, [A‐α‐SiW₉O₃₄]^10–, with Al(NO₃)₃ · 9H₂O or Ga(NO₃)₃ · nH₂O, and unequivocally characterized by single‐crystal X‐ray analysis, ²⁹Si and ¹⁸³W NMR, and FT‐IR spectroscopy as well as elemental analysis and TG/DTA. Single‐crystal X‐ray analysis revealed that the {M₄(μ‐OH)₆}⁶⁺ (M = Al, Ga) clusters were included in an open pocket of the open‐Dawson polyanion, [α,α‐Si₂W₁₈O₆₆]^16–, which was constituted by the fusion of two trilacunary Keggin POMs via two W–O–W bonds. These two open‐Dawson structural POMs showed clear difference of the bite angles depending on the size of ionic radii. In cases of both compounds, the solution ²⁹Si and ¹⁸³W NMR spectra in D₂O showed only one signal and five signals, respectively. These spectra were consistent with the molecular structures of Al₄ ‐ and Ga₄ ‐ open , suggesting that these polyoxoanions were obtained as single species and maintained their molecular structures in solution.     

{[Mn2(μ3‐Tda)2(μ‐H2O)(H2O)2(bipy)]·DMF}n – a 2D Manganese(II) Coordination Polymer involving Six‐membered Binuclear Metallacycle Nodes

The single crystal X‐ray analysis of a novel thiophene‐2,5‐dicarboxylic acid (H₂Tda) Manganese(II) coordination polymer, {Mn₂(μ₃‐Tda)₂(μ‐H₂O)(H₂O)₂(bipy)]·DMF}_n, shows two different types of Mn²⁺‐ions with environment of Mn1O₆ and Mn2O₄N₂, and the complex is a two‐dimensional polymer as a result of bridging (Tda)^2? ligands and by connecting the carboxylate‐ and water‐bridged {Mn₂(μ‐Tda)₂(μ‐H₂O)} nodes.     

Mechanistic studies on the oxidation of glyoxylic and pyruvic acids by a {Mn3O4}4+ core in aqueous media

In aqueous media, the Mn^IV trimer [Mn^IV₃(μ‐O)₄(phen)₄(H₂O)₂]⁴⁺ ( 1 , phen = 1,10‐phenanthroline) equilibrates with its deprotonated from [Mn₃(μ‐O)₄(phen)₄(H₂O)(OH)]³⁺ ( 2 ). Among the several synthetic multinuclear oxo‐ and/or carboxylato‐bridged manganese complexes known to date containing metal‐bound water, to the best of our knowledge, 1 is one of the rare examples that deprotonates ( 1 ? 2 + H⁺; pK_a = 4.00 (±0.15) at 25.0°C, I = 1.0 mol dm^?3, maintained with NaNO₃) at physiological pH. In aqueous media (pH 2–4), 1 oxidizes both glyoxylic and pyruvic acids to formic and acetic acid, respectively, along with the formation of CO₂, the end manganese state being Mn^II. Kinetic studies suggest that the species 1 , its deprotonated form 2 , the reducing acids (HA), and their conjugate bases (A^?) all take part in the reaction. The oxidant 1 is found to be more reactive than its conjugate base 2 , and HA reacts faster than A^? in reducing 1 or 2 . The gem‐diol form of the α‐oxo acids (especially for glyoxylic acid) is the possible reducing species. The Mn^IV₃ to Mn^II transition in the present observation proceeds through the intermediate generation of the spectrally characterized mixed‐valent Mn^IIIMn^IV dimer that quickly collapses to Mn^II. The observed rates of glyoxylic or pyruvic acid oxidation do not depend on the variation of 1,10‐phenanthroline content of the solution, indicating the absence of any phen‐releasing preequilibrium of the title complex in solution. The reactions rates were found to be lowered in media enriched with D₂O in comparison to that in H₂O and a rate‐limiting one electron one proton (1e, 1H⁺) electroprotic mechanism is proposed. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 323–335, 2010     

Synthesis and Characterization of 1,3,2‐Bis (arylamino) phospholidine, 2‐oxide Derivatives: Crystal Structures of $\rm Cl(O)\overline{PN(p-Me-C_{6}H_{4})CH_{2}CH_{2}N}(p-Me-C_{6}H_{4})$ and $\rm ((CH_{2}C_{6}H_{5})(O)\overline{PN(p-Me-C_{6}H_{4})CH_{2}CH_{2}N}(p-Me-C_{6}H_{4})$

Using phosphoryl chloride as a substrate, a family of 1,3,2‐bis(arylamino) phospholidine, 2‐oxide of the general formula ; (X=Cl, 6a ; X=NMe₂, 1b ; X=N(CH₂C₆H₅)(CH₃), 2b ; X=NHC(O)C₆H₅, 3b ; X=4Me‐C₆H₄O, 4b ; X=C₆H₅O, 5b ; X=NHC₆H₁₁, 6b ; X=OC₄H₈N, 7b ; X=C₅H₁₀N, 8b ; X=NH₂, 9b ; X=F, 10b and Ar=4Me‐C₆H₄) was prepared and characterized by ¹H, ¹⁹F, ³¹P and ¹³C NMR and IR spectroscopy, and elemental analysis. A general and practical method for the synthesis of these compounds was selected. The structures of 6a and 2b were determined by single‐crystal X‐ray diffraction techniques. The low temperature NMR spectra of 2b revealed the restricted rotation of P‐N bond according to two independent molecules in crystalline lattice.     

Synthesis and Properties of Complexes with Unusual {MnIII4} and {MnII4} Cages

Two types of manganese complexes with [Mn₄] cores featuring the unusual distorted cube topology are presented, the first of which comprises new modifications of the reported complex [Mn^III₄(sao)₄(saoH)₄]·3CHCl₃: [Mn₄(sao)₄(saoH)₄]·1.32(C₄H₁₀O)·0.43(CH₄O) ( 1a ) and [Mn(sao)₄(saoH)₄]·0.5(CH₄O)·0.5(C₂H₃N) ( 1b ) sao = salicylaldoxime. The second, 0.55[Mn₄Cl₄(C₁₂H₉N₂O)₄(CH₃OH)₂(H₂O)₂]·0.45[Mn₄Cl₄(C₁₂H₉N₂O)₄(CH₃OH)₄] ( 2 ), is the first reported case of a {Mn^II₄} core of this topology besides known {Mn^III₄} compounds. Differences between the {Mn^II₄} and {Mn^III₄} situation are discussed, and so far overlooked differences in magnetic properties between different {Mn^III₄} compounds are pointed out.     

Hydrothermal Combination of Trilacunary Dawson Phosphotungstates and Hexanickel Clusters: From an Isolated Cluster to a 3D Framework

Three novel hexa‐Ni‐substituted Dawson phosphortungstates [Ni₆(en)₃(H₂O)₆(μ₃‐OH)₃(H₃P₂W₁₅O₅₆)] ? 14 H₂O ( 1 ), [Ni(enMe)₂(H₂O)][Ni₆(enMe)₃(μ₃‐OH)₃(H₂O)₆(HP₂W₁₅O₅₆)] ? 10 H₂O ( 2 ), and [Ni(enMe)₂]₃[Ni(enMe)₂(H₂O)][Ni(enMe)(H₂O)₂][Ni₆(enMe)₃(μ₃‐OH)₃(Ac)₂(H₂O)(P₂W₁₅O₅₆)]₂ ? 6 H₂O ( 3 ) (en=ethylenediamine, enMe=1, 2‐diaminopropane, Ac=CH₃COO^?) have been made under hydrothermal conditions and were characterized by IR spectroscopy, elemental analysis, diffuse reflectance spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The common structural features of compounds 1 – 3 contain the similar hexa‐Ni‐substituted Dawson polyoxometalate (POM) units that can be viewed as a [Ni₆(μ₃‐OH)₃]⁹⁺ cluster capping on a [P₂W₁₅O₅₆]^12? fragment. Compounds 1 and 2 are two isolated clusters, whereas compound 3 is the first 3D POM framework constructed from hexa‐Ni‐substituted Dawson POM units and Ni(enMe) complex bridges. The preparations of compounds 1 – 3 not only indicate that triangle coplanar Ni₆ clusters are very stable fragments in both trivacant Keggin and trivacant Dawson POM systems, but also offer that the hydrothermal technique can act as an effective strategy for making novel Dawson‐type high‐nuclear transition‐metal cluster substituted POMs by combination of lacunary Dawson precusors with transition‐metal cations in the tunable role of organic ligands. In addition, magnetic measurements illustrate that there exist overall ferromagnetic interactions in compound 3 .     

Diverse Ligand‐Functionalized Mixed‐Valent Hexamanganese Sandwiched Silicotungstates with Single‐Molecule Magnet Behavior

Under hydrothermal conditions, replacement of the water molecules in the [Mn^III₄Mn^II₂O₄(H₂O)₄]⁸⁺ cluster of mixed‐valent Mn₆ sandwiched silicotungstate [(B‐α‐SiW₉O₃₄)₂Mn^III₄Mn^II₂O₄(H₂O)₄]^12? ( 1 a ) with organic N ligands led to the isolation of five organic–inorganic hybrid, Mn₆‐substituted polyoxometalates (POMs) 2 – 6 . They were all structurally characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, diffuse‐reflectance spectroscopy, and powder and single‐crystal X‐ray diffraction. Compounds 2 – 6 represent the first series of mixed‐valent {Mn^III₄Mn^II₂O₄(H₂O)_4?n(L)_n} sandwiched POMs covalently functionalized by organic ligands. The preparation of 1 – 6 not only indicates that the double‐cubane {Mn^III₄Mn^II₂O₄(H₂O)_4?n(L)_n} clusters are very stable fragments in both conventional aqueous solution and hydrothermal systems and that organic functionalization of the [Mn^III₄Mn^II₂O₄(H₂O)₄]⁸⁺ cluster by substitution reactions is feasible, but also demonstrates that hydrothermal environments can promote and facilitate the occurrence of this substitution reaction. This work confirms that hydrothermal synthesis is effective for making novel mixed‐valent POMs substituted with transition‐metal (TM) clusters by combining lacunary Keggin precursors with TM cations and tunable organic ligands. Furthermore, magnetic measurements reveal that 3 and 6 exhibit single‐molecule magnet behavior.     

[Mn12O12(O2CMe)12(NO3)4(H2O)4]: facile synthesis of a new type of Mn12 complex

The title dodecanuclear Mn complex, namely dodeca‐μ₂‐acetato‐κ²⁴O:O′‐tetraaquatetra‐μ₂‐nitrato‐κ⁸O:O′‐tetra‐μ₄‐oxido‐octa‐μ₃‐oxido‐tetramanganese(IV)octamanganese(III) nitromethane tetrasolvate, [Mn₁₂(CH₃COO)₁₂(NO₃)₄O₁₂(H₂O)₄]·4CH₃NO₂, was synthesized by the reaction of Mn²⁺ and Ce⁴⁺ sources in nitromethane with an excess of acetic acid. This compound is distinct from the previously known single‐molecule magnet [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄], synthesized by Lis [Acta Cryst. (1980), B 36 , 2042–2044]. It is the first Mn₁₂‐type molecule containing nitrate ligands to be directly synthesized without the use of a preformed cluster. Additionally, this molecule is distinct from all other known Mn₁₂ complexes due to intermolecular hydrogen bonds between the nitrate and water ligands, which give rise to a three‐dimensional network. The complex is compared to other known Mn₁₂ molecules in terms of its structural parameters and symmetry.