Selective inclusion of Cu+ and Ag+ electron-rich metallic cations within supramolecular polyoxometalates based on {AsW9O33}{Mo3S4} combinations

Coordination of the [Mo(3)S(4)(H(2)O)(9)](4+) cluster with the trivacant [AsW(9)O(33)](9-) ion gives the supramolecular complex [{(H(4)AsW(9)O(33))(4)(Mo(3)S(4){H(2)O}(5))}(2)](12-) (1) in good yield. The structure of 1 shows that two [H(4)AsW(9)O(33)](5-) subunits sandwich a single central [Mo(3)S(4)(H(2)O)(5)](4+) ion to give a basic monomeric unit [(H(4)AsW(9)O(33))(2){Mo(3)S(4)(H(2)O)(5)}](6-). In the solid state, a supramolecular dimeric association is evidenced that consists of two [(H(4)AsW(9)O(33))(2){Mo(3)S(4)(H(2)O)(5)}](6-) units held together by twelve hydrogen bonds and four SS contacts. Complex 1 reacts with NaAsO(2), AgNO(3) and CuI to give compounds 2, 3 and 4, respectively. X-ray structural analysis reveals that the molecular arrangements of 2 to 4 are closely related to the parent structure of 1. {AsOH}(2+), Ag(+) and Cu(+) ions are located on three distinct pairs of sites. Two hanging {AsOH}(2+) groups in 2 are symmetrically attached to two opposite {AsW(9)O(33)} subunits. Complex 3 is the first example of an Ag/{Mo(3)S(4)} combination in which the environment of the two equivalent Ag(+) cations is remarkable for containing two sulfur atoms belonging to {Mo(3)S(4)}, two oxygen and one central arsenic atom of the {AsW(9)O(33)} subunits. Potentiometric titration shows that the addition of Ag(+) ions is quantitative and occurs in two successive steps (K(1)=4.1 x 10(6) and K(2)=2.3 x 10(5) L mol(-1)), which is consistent with the retention of the supramolecular cluster in solution. The structure of 4 reveals a single copper atom embedded in the central part of the dimer. The Cu(+) cation is bound to four sulfur atoms to complete a cuboidal moiety. UV/Vis studies in solution indicate that the stability of the dimeric assemblies of 2, 3 and 4 is significantly enhanced by the presence of Cu(+) or Ag(+) ions, which act as additional coordination linkers within the supramolecular cluster. The anions 1 to 4 were characterised by (183)W NMR spectroscopy in solution. The 10-line spectra recorded for each of them are consistent with an averaged C(2h) molecular symmetry in solution.     

Polyoxometalates paneling through {Mo2O2S2} coordination: cation-directed conformations and chemistry of a supramolecular hexameric scaffold

The chemical system based on the [Mo(2)O(2)S(2)(OH(2))(6)](2+) aqua cation (noted L) and the trivacant [AsW(9)O(33)](9-) polyoxometalate (noted POM) has been investigated. Depending upon the ionic strength and the nature of the alkali cations, these complementary components assemble to yield three different architectures derived as hexamer (1), tetramer (2), and dimer (3). This series of clusters displays the same stoichiometry {POM(6)L(9)}(36-), {POM(4)L(6)}(24-), and {POM(2)L(3)}(12-) for 1, 2, and 3, respectively, and their conditions of formation differ mainly by the nature and the concentration of the alkali cation (from Li to Cs). Structural characterizations of 1 reveal a large hexameric supramolecular scaffold (about 25 ? in diameter), which encloses a large internal hole (about 200 ?(3)) filled by water molecules and alkali cations (Na(+) or K(+)). The hexameric scaffold 1 exhibits a rare flexibility property evidenced in the solid state by two distinct conformations, either eclipsed (1a) or staggered-off (1b). Both conformations appear clearly separated by a large twist angle (~40°) and depend mainly on the composition of the internal hole. Structure of anion 2 shows a tetrahedral arrangement where the four POM units and the six connecting {Mo(2)O(2)S(2)} linkers are located at the corners and at the edges, respectively. The structure of anion 3 corresponds to the simplest arrangement, described as a dimeric association of two POM units linked by three {Mo(2)S(2)O(2)} pillars. Stability of the hexameric scaffold has been investigated in solution by (183)W and (39)K NMR and by UV-vis, showing that stability of 1 depends strongly on the proportion of potassium ions, which interfere through host-guest exchange. Density functional methodology (DFT) has been applied to compute the geometries and energies of dimer (3), tetramer (2) and hexamer (1) based on {AsW(9)O(33)} (POM) and {Mo(2)O(2)S(2)} (L) units. Calculations tend to show that internal cations act as "glue" to maintain the POM units connected through the conformationally inward-directed {Mo(2)O(2)S(2)} linkers.     

Structure,magnetism, and electrochemistry of the multinickel polyoxoanions [Ni6As3W24O94(H2O)2]17-, [Ni3Na(H2O)2(AsW9O34)2]11-, and [Ni4Mn2P3W24O94(H2O)2]17-

The three novel, multi-nickel-substituted heteropolytungstates [Ni(6)As(3)W(24)O(94)(H(2)O)(2)](17)(-) (1), [Ni(3)Na(H(2)O)(2)(AsW(9)O(34))(2)](11)(-) (2), and [Ni(4)Mn(2)P(3)W(24)O(94)(H(2)O)(2)](17)(-) (3) have been synthesized and characterized by IR, elemental analysis, electrochemistry, and magnetic studies. Single-crystal X-ray analysis was carried out on Na(16.5)Ni(0.25)[Ni(6)As(3)W(24)O(94)(H(2)O)(2)].54H(2)O, which crystallizes in the triclinic system, space group P1, with a = 17.450(4) A, b = 17.476(4) A, c = 22.232(4) A, alpha = 85.73(3) degrees, beta = 89.74(3) degrees, gamma = 84.33(3) degrees, and Z = 2, Na(11)[Ni(3)Na(H(2)O)(2)(AsW(9)O(34))(2)].30.5H(2)O, which crystallizes in the triclinic system, space group P1, with a = 12.228(2) A, b = 16.743(3) A, c = 23.342(5) A, alpha = 78.50(3) degrees, beta = 80.69(3) degrees, gamma = 78.66(3) degrees, and Z = 2, and Na(17)[Ni(4)Mn(2)P(3)W(24)O(94)(H(2)O)(2)].50.5H(2)O, which crystallizes in the monoclinic system, space group P2(1)/c, with a = 17.540(4) A, b = 22.303(5) A, c = 35.067(7) A, beta = 95.87(3) A, and Z = 4. Polyanion 1 consists of two B-alpha-(Ni(3)AsW(9)O(40)) Keggin moieties linked via a unique AsW(6)O(16) fragment, leading to a banana-shaped structure with C(2)(v)() symmetry. The mixed-metal tungstophosphate 3 is isostructural with 1. Polyanion 2 consists of two lacunary B-alpha-[AsW(9)O(34)](9)(-) Keggin moieties linked via three nickel(II) centers and a sodium ion. Electrochemical studies show that 1-3 exhibit a unique and reproducible voltammetric pattern and that all three compounds are stable in a large pH range. An investigation of the magnetic properties of 1-3 indicates that the exchange interactions within the trimetal clusters are ferromagnetic. However, for 1 and 3 intra- and intermolecular interactions between different trinuclear clusters are also present.     

Reactions of a {Mo16}-type polyoxometalate cluster with electrophiles: a synthetic, theoretical and magnetic investigation

A medium-nuclearity mixed-valence polyoxomolybdate [H2Mo16O52]10-={Mo16}(1a) was synthesized using an approach that employed protonated hexamethylenetetramine (HMTAH+) as counter ion and yielded (HMTAH)10 1a.34 H2O (1). The {Mo16} cluster anion exhibits significant nucleophilicity and traps electrophiles such as divalent transition metal ions, resulting in a family of isostructural compounds based on {Mo16M2}-type anions [M(H2O)8H2Mo16O52]6- (M=FeII (2), MnII (3), CoII (4)). The highly reactive nature of the {Mo16} system is also revealed by rearrangement and decomposition reactions of to either slowly form a sodium-bridged heptamolybdate-based chain compound (5) when left in the reaction solution or, in the presence of very high concentrations of electrophiles, to heptamolybdate-based cluster compounds [M2(H2O)9Mo7O24]2- of the {M2Mo7}-type (M=FeII (6), MnII (7)). Compounds were characterised by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, magnetic susceptibility measurements, and density functional theory calculations.     

Ligand Substitution Reactions at the Nickel of [Mo(3)NiS(4)(H(2)O)(10)](4+) with Two Water Soluble Phosphines, CO, Br(-), I(-), and NCS(-) and the Inertness of the 1,4,7-Triazacyclononane (L) Complex [Mo(3)(NiL)S(4)(H(2)O)(9)](4+)

Comparisons (25 degrees C) are made of substitution reactions, X replacing H(2)O, at the tetrahedral Ni of the heterometallic sulfido cuboidal cluster [Mo(3)NiS(4)(H(2)O)(10)](4+), I = 2.00 M (LiClO(4)). Stopped-flow formation rate constants (k(f)/M(-)(1) s(-)(1)) for six X reagents, including two water soluble air-stable phosphines, 1,3,5-triaza-7-phosphaadamantane PTA (119) and tris(3-sulfonatophenyl)phosphine TPPTS(3)(-) (58), and CO (0.66), Br(-) (14.6), I(-) (32.3), and NCS(-) (44) are reported alongside the previous value for Cl(-) (9.4). A dependence on [H(+)] is observed with PTA, which gives an unreactive form confirmed by NMR as N-protonated PTA (acid dissociation constant K(a) = 0.61 M), but in no other cases with [H(+)] in the range 0.30-2.00 M. The narrow spread of rate constants for all but the CO reaction is consistent with an I(d) dissociative interchange mechanism. In addition NMR studies with H(2)(17)O enriched solvent are too slow for direct determination of the water-exchange rate constant indicating a value <10(3) s(-)(1). Equilibrium constants/M(-)(1) for 1:1 complexing with the different X groups at the Ni are obtained for PTA (2040) and TPPTS(3)(-) (8900) by direct spectrophotometry and from kinetic studies (k(f)/k(b)) for Cl(-) (97), Br(-) (150), NCS(-) (690), and CO (5150). No NCS(-) substitution at the Ni is observed in the case of the heterometallic cube [Mo(3)Ni(L)S(4)(H(2)O)(9)](4+), with tridentate 1,4,7-triazacyclononane(L) coordinated to the Ni. Substitution of NCS(-) for H(2)O, at the Mo's of [Mo(3)NiS(4)(H(2)O)(10)](4+) and [Mo(3)(NiL)S(4)(H(2)O)(9)](4+) are much slower secondary processes, with k(f) = 2.7 x 10(-)(4) M(-)(1) s(-)(1) and 0.94 x 10(-)(4) M(-)(1) s(-)(1) respectively. No substitution of H(2)O by TPPTS(3)(-) or CO is observed over approximately 1h at either metal on [Mo(3)FeS(4)(H(2)O)(10)](4+), on [Mo(4)S(4)(H(2)O)(12)](5+) or [Mo(3)S(4)(H(2)O)(9)](4+).     

Metal complexes of tetrapodal ligands: synthesis, spectroscopic and thermal studies, and X-ray crystal structure studies of Na(I), Ca(II), Sr(II), and Ba(II) complexes of tetrapodal ligands N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine

Twelve complexes 1-12 of general category [M(ligand)(anion)(x)(water)(y)], where ligand = N,N,N',N'-tetrakis(2-hydroxypropyl/ethyl)ethylenediamine (HPEN/HEEN), anion = anions of picric acid (PIC), 3,5-dinitrobenzoic acid (DNB), 2,4-dinitrophenol (DNP), and o-nitrobenzoic acid (ONB), M = Ca(2+), Sr(2+), Ba(2+), or Na(+), x = 1 and 2, and y = 0-4, were synthesized. All of these complexes were characterized by elemental analysis, IR, (1)H and (13)C NMR, and thermal studies. X-ray crystal studies of these complexes 1-12, [Ca(HPEN)(H(2)O)(2)](PIC)(2).H(2)O (1), [Ca(HEEN)(PIC)](PIC) (2), Ba(HPEN)(PIC)(2) (3), [Na(HPEN)(PIC)](2) (4), Ca(HPEN)(H(2)O)(2)](DNB)(2).H(2)O (5),Ca(HEEN)(H(2)O)](DNB)(2).H(2)O (6), [Sr(HPEN)(H(2)O)(3)](DNB)(2) (7), [Ba(HPEN)(H(2)O)(2)](DNB)(2).H(2)O](2) (8), [[Ba(HEEN)(H(2)O)(2)](ONB)(2)](2) (9), [[Sr(HPEN)(H(2)O)(2)](DNP)(2)](2) (10), [[Ba(HPEN)(H(2)O)(2)](DNP)(2)](2) (11), and [Ca(HEEN)(DNP)](DNP) (H(2)O) (12), have been carried out at room temperature. Factors which influence the stability and the type of complex formed have been recognized as H-bonding interactions, presence/absence of solvent, nature of the anion, and nature of the cation. Both the ligands coordinate the metal ion through all the six available donor atoms. The complexes 1 and 5-11 have water molecules in the coordination sphere, and their crystal structures show that water is playing a dual character. It coordinates to the metal ion on one hand and strongly hydrogen bonds to the anion on the other. These strong hydrogen bonds stabilize the anion and decrease the cation-anion interactions by many times to an extent that the anions are completely excluded out of the coordination sphere and produce totally charge-separated complexes. In the absence of water molecules as in 2 and 3 the number of hydrogen bonds is reduced considerably. In both the complexes the anions case interact more strongly with the metal ion to give rise to a partially charge-separated 2 or tightly ion-paired 3 complex. High charge density Ca(2+) forms only monomeric complexes. It has more affinity toward stronger nucleophiles such as DNP and PIC with which it gives partially charge-separated eight-coordinated complexes. But with relatively weaker nucleophile like DNB, water replaces the anion and produces a seven coordinated totally charge-separated complex. Sr(2+) with lesser charge/radius ratio forms only charge-separated monomeric as well as dimeric complexes. Higher coordination number of Sr(2+) is achieved with coordinated water molecules which may be bridging or nonbridging in nature. All charge-separated complexes of the largest Ba(2+) are dimeric with bridging water molecules. Only one monomeric ion-paired complex was obtained with Ba(PIC)(2). Na(+) forms a unique dinuclear cryptand-like complex with HPEN behaving as a heptadentate chelating-cum-bridging ligand.     

Electrochemical, spectroscopic, structural, and magnetic characterization of the reduced and protonated alpha-Dawson anions in [Fe(eta(5)-C(5)Me(5))(2)](5)[HS(2)Mo(18)O(62)].3HCONMe(2).2Et(2)O and [NBu(4)](5)[HS(2)Mo(18)O(62)].2H(2)O(1)

Reaction of excess Fe(cp)(2) (cp = eta(5)-C(5)Me(5)) dissolved in Et(2)O with [NHex(4)](4)[S(2)Mo(18)O(62)] in acetonitrile, followed by recrystallization of the precipitated solid from N,N'-dimethylformamide (DMF), leads to isolation of the complex [Fe(cp)(2)](5)[HS(2)Mo(18)O(62)].3DMF.2Et(2)O. The solid has been characterized by microanalysis, by voltammetric analysis, by (1)H NMR, diffuse reflectance infrared, EPR, and M?ssbauer spectroscopies, and by temperature-dependent magnetic susceptibility measurements. The data are consistent with the presence of a paramagnetic [Fe(cp)(2)](+) cation and a diamagnetic two-electron-reduced [HS(2)Mo(18)O(62)](5-) anion. The related salt [NBu(4)](5)[HS(2)Mo(18)O(62)].2H(2)O crystallizes in space group C2/c with a = 25.1255(3) A, b = 15.4110(2) A, c = 35.8646(4) A, beta = 105.9381(4), V = 13353.3(3) A(3), and Z = 4. The (2 e(-), 1 H(+))-reduced anion exists as the alpha-Dawson isomer, and its structure may be compared with those of the oxidized and (4 e(-), 3 H(+))-reduced anions as they exist in [NEt(4)](4)[S(2)Mo(18)O(62)].MeCN and [NBu(4)](5)[H(3)S(2)Mo(18)O(62)].4MeCN, respectively. Overall, the anion expands significantly upon the addition of two and then four electrons. However, the Mo...Mo distances along the bonds which connect the two equatorial belts decrease in the order 3.801, 3.780, and 3.736 A, making these distances the shortest for the three inequivalent sets of corner-sharing octahedra in each anion. This is consistent with the two or four added electrons localizing essentially in molecular orbitals which are bondiing with respect to interactions between the belts.     

Novel hexagonal {V=O}6-containing sandwich-type cluster accompanied by in situ carbon-carbon bond formation of organic cations

Two novel sandwich-type polyanions containing hexagonal {V=O}(6) group (H(2)tpy)(Hbpe)(3)H[(VO)(6)(SbW(9)O(33))(2)]·2H(2)O (1) and (H(2)tcy)(6)(Hbpp)(6)H(4)[VW(12)O(40)][(VO)(6)(SbW(9)O(33))(2)](3)·30H(2)O (2) (tpy = 4-(2,3,4-tri(pyridin-4-yl)butyl)pyridine, bpe = 1,2-(4-pyridyl)ethene, tcy = 1,2,4,5-tetra(pyridin-4-yl)cyclohexanol, bpp = 1,3-bis-(4-pyridyl)propane), were reported. Both compounds are built upon the complex hydrogen bonding networks of C-H···O and N-H···O occurred among inorganic anions and organic cations. Unusual in situ organic reactions involving C-C coupling are also observed in 1 and 2 regardless of the rigid bpe or flexible bpp. Compound 2 represents a rare case in which nano-sized α-Keggin [VW(12)O(40)](4-) and sandwich-type [(VO)(6)(SbW(9)O(33))(2)](6-) anionic clusters are present in a common crystal framework.     

Synthesis and redox properties of triarylmethane dye cation salts of anions [M6O19]2- (M = Mo, W)

Four salts have been isolated combining the triarylmethane dye cations pararosaniline (PR(+)) and crystal violet (CV(+)) with the hexametalates [M(6)O(19)](2-) (M = Mo, W). A new hexatungstic acid H(2)[W(6)O(19)]·4dma (dma = dimethylacetamide) was isolated and is a useful synthon for hexatungstate salts. Single-crystal X-ray diffraction confirmed the presence of PR(+) and [Mo(6)O(19)](2-) ions in [PR](2)[Mo(6)O(19)]·6dmf (dmf = dimethylformamide). A number of charge-assisted hydrogen bonds N-H···O exist between the cation -NH(2) functions and the anion oxygen atoms. Comparative cyclic voltammetry of salts [A]Cl (A = PR, CV), [Bu(4)N](2)[M(6)O(19)](2-) and A(2)[M(6)O(19)] was established in MeCN and Me(2)SO solutions and of solids in contact with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [emim][tfsa]. In the molecular solvents, the reversible potential for the process [Mo(6)O(19)](2-/3-) is less negative than the first reduction processes of the dye cations. In contrast, that for [W(6)O(19)](2-/3-) is more negative. Spectro-electrochemistry and bulk electrolysis experiments reveal significantly different pathways in the two cases. In contrast, in the [emim][tfsa] medium, a positive shift in reduction potential of at least 400 mV is seen for the anion processes but relatively little change for the dye cation processes. This means that initial reduction of the anions always precedes that of the dyes, providing significant simplification of the complex voltammetric data. Chemically modified electrodes can be used in the ionic liquid because of slow dissolution kinetics. However, reduced anion salts dissolve rapidly, allowing dissolved phase electrochemistry to be examined. The electrochemistries of the oxidized salts A(2)[M(6)O(19)] are essentially those of the individual ions, although low level interaction of A(+) with reduced anions [M(6)O(19)](3-,4-) is evident. The work establishes protocols for synthesis and handling of intensely absorbing and relatively insoluble salts which can now be applied to systems containing more complex polyoxometalate anions.     

Interconversion and Reactivity of Two Heterometallic Tin-Containing Cuboidal Clusters from [Mo(3)S(4)(H(2)O)(9)](4+): X-ray Structure of the Single Cube with an Mo(3)SnS(4) Core

The Mo(3)SnS(4)(6+) single cube is obtained by direct addition of Sn(2+) to [Mo(3)S(4)(H(2)O)(9)](4+). UV-vis spectra of the product (0.13 mM) in 2.00 M HClO(4), Hpts, and HCl indicate a marked affinity of the Sn for Cl(-), with formation of the more strongly yellow [Mo(3)(SnCl(3))S(4)(H(2)O)(9)](3+) complex complete in as little as 0.050 M Cl(-). The X-ray crystal structure of (Me(2)NH(2))(6)[Mo(3)(SnCl(3))S(4)(NCS)(9)].0.5H(2)O has been determined and gives Mo-Mo (mean 2.730 ?) and Mo-Sn (mean 3.732 ?) distances, with a difference close to 1 ?. The red-purple double cube cation [Mo(6)SnS(8)(H(2)O)(18)](8+) is obtained by reacting Sn metal with [Mo(3)S(4)(H(2)O)(9)](4+). The double cube is also obtained in approximately 50% yield by BH(4)(-) reduction of a 1:1 mixture of [Mo(3)SnS(4)(H(2)O)(10)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+). Conversely two-electron oxidation of [Mo(6)SnS(8)(H(2)O)(18)](8+) with [Co(dipic)(2)](-) or [Fe(H(2)O(6)](3+) gives the single cube [Mo(3)SnS(4)(H(2)O)(12)](6+) and [Mo(3)S(4)(H(2)O)(9)](4+) (up to 70% yield), followed by further two-electron oxidation to [Mo(3)S(4)(H(2)O)(9)](4+) and Sn(IV). The kinetics of the first stages have been studied using the stopped-flow method and give rate laws first order in [Mo(6)SnS(8)(H(2)O)(18)](8+) and the Co(III) or Fe(III) oxidant. The oxidation with [Co(dipic)(2)](-) has no [H(+)] dependence, [H(+)] = 0.50-2.00 M. With Fe(III) as oxidant, reaction steps involving [Fe(H(2)O)(6)](3+) and [Fe(H(2)O)(5)OH](2+) are implicated. At 25 degrees C and I = 2.00 M (Li(pts)) k(Co) is 14.9 M(-)(1) s(-)(1) and k(a) for the reaction of [Fe(H(2)O)(6)](3+) is 0.68 M(-)(1) s(-)(1) (both outer-sphere reactions). Reaction of Cu(2+) with the double but not the single cube is observed, yielding [Mo(3)CuS(4)(H(2)O)(10)](5+). A redox-controlled mechanism involving intermediate formation of Cu(+) and [Mo(3)S(4)(H(2)O)(9)](4+) accounts for the changes observed.     

An approach to the synthesis of polyoxometalate encapsulating different kinds of oxoanions as heteroions: bisphosphitopyrophosphatotriacontamolybdate [(HPO3)2(P2O7)Mo30O90]8-

A yellow [(HPO(3))(2)(P(2)O(7))Mo(30)O(90)](8-) anion was prepared as a tetrapropylammonium (Pr(4)N(+)) salt from a 50 mM Mo(VI)-2 mM P(2)O(7)(4-)-4 mM HPO(3)(2-)-0.95 M HCl-60% (v/v) CH(3)CN system at ambient temperature. The (Pr(4)N)(8)[(HPO(3))(2)(P(2)O(7))Mo(30)O(90)] salt crystallized in the orthorhombic space group P(nma) (No. 62), with a = 30.827(2) A, b = 22.8060(15) A, c = 30.928(2) A, V = 21743(3) A(3), and Z = 4. The structure contained a (P(2)O(7))Mo(12)O(42) fragment derived from the removal of each corner-shared Mo(3)O(13) unit in a polar position from a [(P(2)O(7))Mo(18)O(54)](4-) structure, and each side of the (P(2)O(7))Mo(12)O(42) fragment was capped by a B-type (HPO(3))Mo(9)O(24) unit. The [(HPO(3))(2)(P(2)O(7))Mo(30)O(90)](8-) anion was characterized by voltammetry and IR, UV-vis, and (31)P NMR spectroscopy. Unlike the Keggin and Dawson anions and the parent [(P(2)O(7))Mo(18)O(54)](4-) anion, the [(HPO(3))(2)(P(2)O(7))Mo(30)O(90)](8-) anion exhibited two-electron redox waves in CH(3)CN with and without acid.     

Self-assembly of [M8L4] and [M4L2] fluorescent metallomacrocycles with carbazole-based dipyrazole ligands

Fluorescent carbazole-based dipyrazole ligands (H(2)L(1-4)) were employed to coordinate with dipalladium corners ([(phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), [(dmbpy)(2)Pd(2)(NO(3))(2)](NO(3))(2), or [(15-crown-5-phen)(2)Pd(2)(NO(3))(2)](NO(3))(2), where phen = 1,10-phenanthroline and dmbpy = 4,4'-dimethyl-2,2'-bipyridine, in aqueous solution to afford a series of positively charged [M(8)L(4)](8+) or [M(4)L(2)](4+) multimetallomacrocycles with remarkable water solubility. Their structures were characterized by (1)H NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis and in the cases of 1·8BF(4)(-) ([(phen)(8)Pd(8)L(1)(4)](BF(4))(8)), and 3·4BF(4)(-) ([(phen)(4)Pd(4)L(2)(2)](BF(4))(4)) by single-crystal X-ray diffraction analysis. Complexes 3-8 are square-type hybrid metallomacrocycles, while complexes 1 and 2 exhibit folding cyclic structures. Interestingly, in single-crystal structures of 1·8BF(4)(-) and 3·4BF(4)(-), BF(4)(-) anions are trapped in the dipalladium clips through anion-π interaction. The luminescence properties and interaction toward anions of these metallomacrocycles were discussed.     

Syntheses and Characterization of gamma-[SiW(10)M(2)S(2)O(38)](6)(-) (M = Mo(V), W(V)). Two Keggin Oxothio Heteropolyanions with a Metal-Metal Bond

The oxothio polyanions gamma-[SiW(10)M(2)S(2)O(38)](6)(-) (M = Mo(V), W(V)) were obtained through stereospecific addition of the dication [M(2)S(2)O(2)](2+) (M = Mo, W) to the divacant gamma-[SiW(10)O(36)](8)(-) anion in dimethylformamide. These compounds were isolated as crystals and are stable in usual organic solvents and in aqueous medium from pH = 1 to pH = 7. NEt(4)Cs(3)H(2)[SiW(10)Mo(2)S(2)O(38)].6H(2)O (a gamma-isomer derived from the alpha Keggin structure capped by the [Mo(2)S(2)O(2)](2+) fragment containing a metal-metal bond) crystallizes in the triclinic space group P&onemacr; with a = 12.050(3) ?, b = 12.695(2) ?, c = 20.111(4) ?, alpha = 74.35(2) degrees, beta = 86.83(2) degrees, gamma = 63.50(2) degrees, Z = 2. NEt(4)Cs(5)[SiW(12)S(2)O(38)].7H(2)O is isostructural and crystallizes in the triclinic space group P&onemacr; with a = 12.197(4) ?, b = 12.714(3) ?, c = 20.298(3) ?, alpha = 74.75(1) ?, beta = 86.48(2) degrees, gamma = 61.80(2) degrees, Z = 2. (183)W NMR spectra of Li(+) salts in aqueous solution agree with the solid state structures and reveal 100% purity for both anions. Polarographic, infrared and UV-vis data are also given.     

Protonolysis of [((i)PrO)TiMo5O18]3-: access to a family of TiMo5 Lindqvist type polyoxometalates

The tetra-n-butylammonium (TBA) salts of [((i)PrO)TiMo(5)O(18)](3-) 1 and [((i)BuO)TiMo(5)O(18)](3-) 2 were prepared by hydrolysis of mixtures of (TBA)(2)[Mo(2)O(7)], (TBA)(4)α-[Mo(8)O(26)] and Ti(OR)(4) (R = (i)Pr or (i)Bu) in acetonitrile. Treatment of (TBA)(3)1 with alcohols ROH afforded primary and tertiary alkoxide derivatives [(RO)TiMo(5)O(18)](3-) (R = Me 3, (t)Bu 4), whilst aryloxides [(ArO)TiMo(5)O(18)](3-) were prepared by reacting 1 with phenols ArOH (Ar = C(6)H(4)Me-4 5, and C(6)H(4)CHO-2 6). Oxo-bridged [(μ-O)(TiMo(5)O(18))(2)](6-)7 rather than the hydroxo derivative [(HO)TiMo(5)O(18)](3-) was obtained upon hydrolysis of 1. X-Ray crystal structures of TBA salts of anions 3-7 show that titanium is six-coordinate in all cases, although titanium sites are disordered over two trans positions in 3. Mo-O bond length alternation is observed in the Mo(4)O(4) planes of 4 and 7 and in one of the two independent anions in the structure of 3. In solution, (17)O NMR spectra are consistent with the higher anionic charge compared to [Mo(6)O(19)](2-) and reveal an order of basicity for the anions [LM'Mo(5)O(18)](3-) associated with the ability of {LM'}(3+) to donate/withdraw electron density from {Mo(5)O(18)}(6-). Protonolysis reactions of 1 and 3 were slower than for tungstate analogues and the possibility of initial protonation at TiOM (M = Mo) rather than TiOR (M = W) in a proton-assisted S(N)1 mechanism for ligand exchange in [(RO)TiM(5)O(18)](3-) is discussed.     

四金属簇钨砷夹心型化合物[M4(H2O)2·(AsW9O34)2]10-(M=CuⅡ, CoⅡ, MnⅡ, NiⅡ, ZnⅡ)的合成、结构和磁特性研究

取代型杂多化合物可改变多酸化合物的酸碱性、氧化还原性和热稳定性,因而受到关注[1]. 夹心型化合物是一类新型化合物,具有大的摩尔质量,高的负电荷,且含有多个磁性中心,近年来已引起国内外的兴趣[2].     

{Mo102}型纳米多孔无机富勒烯衍生物的合成、表征及三阶非线性光学性质

在室温酸性条件下, 利用高负电性的表面分布有20个{Mo9O9}型纳米孔道的无机富勒烯囊状阴离子[{(MoⅥ)Mo5ⅥO21(H2O)6}12{Mo2ⅤO4(SO4)}30]72-与胍基乙酸反应, 得到了表面分布有20个{Mo6O6}型纳米孔道的由102个Mo及氧原子组成的[{(Mo)Mo5O21(H2O)4SO4}12{MoⅤO(H2O)}30]12-小无机富勒烯囊状阴离子. 通过单晶X射线衍射、元素分析、FTIR、UV-Vis、TG-DTA、ESR等手段对其进行了表征. 该化合物属于三斜晶系, P1空间群, 晶胞参数a=2.5377(5) nm, b=2.5932(5) nm, c=3.9547(8) nm, α =83.58(3) °, β=86.15(3) °, γ=75.55(3) °, V=25.023(9) nm3. 利用脉冲时间为5 ns的532 nm激光通过Z-扫描实验得到该化合物的三阶非线性折射率γ=-3.29×10-18 m2/W, 三阶非线性极化率χ(3)=-1.04×10-23 m2·V-2, 表明该化合物具有较强的自散焦三阶非线性光学效应.     

Electronic properties of polyoxometalates: electron and proton affinity of mixed-addenda Keggin and Wells-Dawson anions

A series of systematic DFT calculations were conducted on Keggin [SiW(9)M(3)O(40)](n-), M = Mo, V, and Nb; and Wells-Dawson anions [P(2)M(18)O(62)],(6-) M = W and Mo; [P(2)M(15)M(3)'O(62)](m-), M = W and Mo, M' = W, Mo, and V to analyze the redox properties and the basicity of the external oxygen sites in polyoxometalates with nonequivalent addenda metals. The energy and composition of the lowest unoccupied orbitals, formally delocalized over the addenda atoms, determine the redox properties of a polyoxometalate. When a Mo(6+) substitutes one W(6+) in the 1:12 tungstate, the energy of the LUMO decreases and the cluster is more easily reduced. The tungstoniobates behave differently because the niobium orbitals insert into the tungsten band and the reduction of [SiW(9)Nb(3)O(40)](7-) yields the blue species SiW(9)Nb(3) 1e and not the cluster SiW(9)Nb(2)Nb(IV). In Wells-Dawson structures, the polar and equatorial sites have different electron affinities and the reduction preferentially occurs in the equatorial sites. Inserting ions with larger electron affinities into the polar sites can modify this traditional conduct. Hence, the trisubstituted [P(2)W(15)V(3)O(62)](9-) anion is reduced in the vanadium polar sites. By means of molecular electrostatic potential maps and the relative energy of the various protonated forms of [SiW(9)V(3)O(40)](7-) and [SiW(9)Mo(3)O(40)](4-), we established the basicity scale: OV(2) > OMo(2) > OW(2) > OV > OW > OMo. Finally, a continuum model for the solvent enabled us to compare anions with different total charges.     

Heterometallic cubane-like {M2Ln2} (M = Ni, Zn; Ln =, Gd, Dy) and {Ni2Y2} aggregates. Synthesis, structures and magnetic properties

The syntheses, structural determinations and magnetic studies of tetranuclear M(II)Ln(III) complexes (M = Ni, Zn; Ln = Y, Gd, Dy) involving an in situ compartmentalized schiff base ligand HL derived from the condensation of o-vanillin and 2-hydrazinopyridine as main ligand are described. Single-crystal X-ray diffraction reveals that all complexes are closely isostructural, with the central core composed of distorted {M(2)Ln(2)O(4)} cubes of the formulas [Ni(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(4)(H(2)O)(3.5)](ClO(4))(2)·3H(2)O (Ln = Y 1 and Gd 2), [Ni(2)Dy(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)(1.5)](ClO(4))·EtOH·H(2)O (3) and [Zn(2)Ln(2)(μ(3)-OH)(2)(L)(2)(OAc)(5)(EtOH)(H(2)O)](ClO(4))·2EtOH·1.5H(2)O (Gd 4 and Dy 5). The Ln(III) ions are linked by two hydroxo bridges and each M(II) ion is also involved in a double phenoxo-hydroxo bridge with the two Ln(III) ions, so that each hydroxo group is triply linked to the two Ln(III) and one M(II) ions. The magnetic properties of all complexes have been investigated. Ni(2)Y(2) (1) has a ferromagnetic Ni(II)Ni(II) interaction. A weak ferromagnetic Ni(II)Ln(III) interaction is observed in the Ni(2)Ln(2) complexes (Ln = Gd 2, Dy 3), along with a weak antiferromagnetic Ln(III)Ln(III) interaction, a D zero-field splitting term for the nickel ion and a ferromagnetic Ni(II)Ni(II) interaction. The isomorphous Zn(2)Ln(2) (Ln = Gd 4, Dy 5) does confirm the presence of a weak antiferromagnetic Ln(III)Ln(III) interaction. The Ni(2)Dy(2) complex (3) does not behave as a SMM, which could result from a subtractive combination of the Dy and Ni anisotropies and an increased transverse anisotropy, leading to large tunnel splittings and quantum tunneling of magnetization. On the other hand, Zn(2)Dy(2) (5) exhibits a possible SMM behavior, where its slow relaxation of magnetization is probably attributed to the presence of the anisotropic Dy(III) ions.     

The heteropolytungstate core {BW13O46}11- derived as monomer, dimer, and trimer

A study of the borotungstate system has led to the characterization of new, original compounds based on the unconventional Keggin derivative [H(3)BW(13)O(46)](8-) ion (denoted as 1). [H(3)BW(14)O(48)](6-) (2) and the dimer [H(6)B(2)W(26)O(90)](12-) (3) crystallize as mixed cesium/ammonium salts and have been characterized by single-crystal X-ray diffraction analysis. Anion 2 reveals an unusual arrangement, consisting of an outer {W(3)O(9)} core grafted onto the monovacant [BW(11)O(39)](9-) Keggin moiety and exhibits an unprecedented distorted square-pyramidal arrangement for a cis-{WO(2)} core. Elemental analysis, supported by bond distance analysis, is consistent with the presence of three protons distributed over the terminal oxygens of the outer {W(3)O(7)} capping fragment. The [H(6)B(2)W(26)O(90)](12-) ion (3) is formally derived from the direct condensation of two [H(3)BW(13)O(46)](8-) subunits. The cisoid arrangement of the two [BW(11)O(39)](9-) subunits, coupled with the antiparallel arrangement of the two quasi-linear O=W...O=W-OH2 chains within the central {W(4)O(12)} connecting group, breaks any symmetry, thereby resulting in a chiral compound. Polarography and pH-metric titrations reveal the formation of the monomeric precursor [H(3)BW(13)O(46)](8-) (anion 1) under stoichiometric conditions. (183)W NMR analysis of 2 and 3 in solution gives complex spectra, consistent with the presence of equilibria between several species. In the frame of this study, we also report on a structural re-investigation of the [H(6)B(3)W(39)O(132)](15-) ion (4) based on reliable results obtained in the solid state by means of single-crystal X-ray diffraction analysis, and in solution by means of 1D and 2D COSY (183)W NMR. X-ray diffraction analysis revealed the presence of three attached aquo ligands on the central {W(6)O(15)} connecting core, generating three O=W...O=W-OH2 quasi-linear chains, which are responsible for the chirality of the trimeric assembly. This structural arrangement accounts for the 39-line (183)W solution spectrum. The 2D COSY spectrum permits reliable assignments of the six strongly shielded resonances (around -250 and -400 ppm) to the six central W atoms, as well as additional assignments. The origin of such strong shielding for these particular W atoms is discussed on the basis of previously published results. Infrared data for compounds 1, 3, and 4 are also presented.     

Preparation and Properties of the Corner-Shared Double Cube [Mo(6)BiS(8)(H(2)O)(18)](8+) as a Derivative of [Mo(3)S(4)(H(2)O)(9)](4+) in Aqueous Acidic Solutions

The reaction of [Mo(3)S(4)(H(2)O)(9)](4+) with Bi(III) in the presence of BH(4)(-) (rapid), or with Bi metal shot (3-4 days), gives a heterometallic cluster product. The latter has been characterized as the corner-shared double cube [Mo(6)BiS(8)(H(2)O)(18)](8+) by the following procedures. Analyses by ICP-AES confirm the Mo:Bi:S ratio as 6:1:8. Elution from a cation-exchange column by 4 M Hpts (Hpts = p-toluenesulfonic acid), but not 2 M Hpts (or 4 M HClO(4)), is consistent with a high charge. The latter is confirmed as 8+ from the 3:1 stoichiometries observed for the oxidations with [Co(dipic)(2)](-) or [Fe(H(2)O)(6)](3+) yielding [Mo(3)S(4)(H(2)O)(9)](4+) and Bi(III) as products. Heterometallic clusters [Mo(6)MS(8)(H(2)O)(18)](8+) are now known for M = Hg, In, Tl, Sn, Pb, Sb, and Bi and are a feature of the P-block main group metals. The color of [Mo(6)BiS(8)(H(2)O)(18)](8+) in 2.0 M Hpts (turquoise) is different from that in 2.0 M HCl (green-blue). Kinetic studies (25 degrees C) for uptake of a single chloride k(f) = 0.80 M(-)(1) s(-)(1), I = 2.0 M (Hpts), and the high affinity for Cl(-) (K > 40 M(-)(1)) exceeds that observed for complexing at Mo. A specific heterometal interaction of the Cl(-) not observed in the case of other double cubes is indicated. The Cl(-) can be removed by cation-exchange chromatography with retention of the double-cube structure. Kinetic studies with [Co(dipic)(2)](-) and hexaaqua-Fe(III) as oxidants form part of a survey of redox properties of this and other clusters. The Cl(-) adduct is more readily oxidized by [Co(dipic)(2)](-) (factor of approximately 10) and is also more air sensitive.