Excision of the

The synthesis of new molybdenum cluster selenocyanide anionic complexes [Mo6Se8(CN)6]7- and [Mo6Se8(CN)6]6- is reported. The [Mo6Se8(CN)6]7- ion was obtained by excision of the cluster core [Mo6Se8] from a Chevrel phase in the reaction of Mo6Se8 with KCN at 650 degrees C; the [Mo6Se8(CN)6]6- ion is formed by oxidation of [Mo6Se8(CN)6]7-. New cluster salts K7[Mo6Se8(CN)6] x 8H2O (1) and (Me4N)4K2[Mo6Se8(CN)6] x 10H2O (2) were isolated and their crystal structures were solved. Compound 1 crystallizes in the cubic space group Fm3m (a=15.552(2) A, Z=4, V=3761.5(8) A3), compound 2 crystallizes in the triclinic space group P1 (a=11.706(2), b=11.749(2), c=12.459(2) A, alpha=72.25(1), beta=77.51(1), gamma=63.04(1), Z=1, V=1448.5(4) A3). Compound 1 is paramagnetic due to an availability of 21 electrons per Mo6 cluster; cyclic voltammetry reveals a quasi-reversible transition [Mo6Se8(CN)6]7- <--> [Mo6Se8(CN)6]6-, E1/2=0.63 V.     

Expanded Prussian blue analogues incorporating [Re6Se8(CN)6](3-/4-) clusters: adjusting porosity via charge balance

Face-capped octahedral [Re(6)Se(8)(CN)(6)](3-/4-) clusters are used in place of octahedral [M(CN)(6)](3-/4-) complexes for the synthesis of microporous Prussian blue type solids with adjustable porosity. The reaction between [Fe(H(2)O)(6)](3+) and [Re(6)Se(8)(CN)(6)](4-) in aqueous solution yields, upon heating, Fe(4)[Re(6)Se(8)(CN)(6)](3).36H(2)O (4). A single-crystal X-ray analysis confirms the structure of 4 to be a direct expansion of Prussian blue (Fe(4)[Fe(CN)(6)](3).14H(2)O), with [Re(6)Se(8)(CN)(6)](4-) clusters connected through octahedral Fe(3+) ions in a cubic three-dimensional framework. As in Prussian blue, one out of every four hexacyanide units is missing from the structure, creating sizable, water-filled cavities within the neutral framework. Oxidation of (Bu(4)N)(4)[Re(6)Se(8)(CN)(6)] (1) with iodine in methanol produces (Bu(4)N)(3)[Re(6)Se(8)(CN)(6)] (2), which is then metathesized to give the water-soluble salt Na(3)[Re(6)Se(8)(CN)(6)] (3). Reaction of [Co(H(2)O)(6)](2+) or [Ni(H(2)O)(6)](2+) with 3 in aqueous solution affords Co(3)[Re(6)Se(8)(CN)(6)](2).25H(2)O (5) or Ni(3)[Re(6)Se(8)(CN)(6)](2).33H(2)O (6). Powder X-ray diffraction data show these compounds to adopt structures based on the same cubic framework present in 4, but with one out of every three cluster hexacyanide units missing as a consequence of charge balance. In contrast, reaction of [Ga(H(2)O)(6)](3+) with 3 gives Ga[Re(6)Se(8)(CN)(6)].6H(2)O (7), wherein charge balance dictates a fully occupied cubic framework enclosing much smaller cavities. The expanded Prussian blue analogues 4-7 can be fully dehydrated, and retain their crystallinity with extended heating at 250 degrees C. Consistent with the trend in the frequency of framework vacancies, dinitrogen sorption isotherms show porosity to increase along the series of representative compounds 7, Ga(4)[Re(6)Se(8)(CN)(6)](3).38H(2)O, and 6. Furthermore, all of these phases display a significantly higher sorption capacity and surface area than observed in dehydrated Prussian blue. Despite incorporating paramagnetic [Re(6)Se(8)(CN)(6)](3-) clusters, no evidence for magnetic ordering in compound 6 is apparent at temperatures down to 5 K. Reactions related to those employed in preparing compounds 4-6, but carried out at lower pH, produce the isostructural phases H[cis-M(H(2)O)(2)][Re(6)Se(8)(CN)(6)].2H(2)O (M = Fe (8), Co (9), Ni (10)). The crystal structure of 8 reveals a densely packed three-dimensional framework in which [Re(6)Se(8)(CN)(6)](4-) clusters are interlinked through a combination of protons and Fe(3+) ions.     

Cluster-to-metal magnetic coupling: synthesis and characterization of 25-electron [Re6-nOsnSe8(CN)6](5-n)-(n = 1, 2) clusters and (Re6-nOsnSe8[CNCu(Me6tren)]6)9+(n = 0, 1, 2) assemblies

The first face-capped octahedral clusters with 25 metal-based valence electrons are shown to provide versatile building units capable of engaging in magnetic exchange coupling. Reactions of [Re(5)OsSe(8)Cl(6)](3-) and [Re(4)Os(2)Se(8)Cl(6)](2-) with NaCN in a melt of NaNO(3) or KCF(3)SO(3) afford the 24-electron clusters [Re(5)OsSe(8)(CN)(6)](3-) and [Re(4)Os(2)Se(8)(CN)(6)](2-). The 13C NMR spectrum of a 13C-labeled version of the latter species indicates a 1:2 mixture of cis and trans isomers. Cyclic voltammograms of the clusters in acetonitrile display reversible [Re(5)OsSe(8)(CN)(6)](3-/4-), cis-[Re(4)Os(2)Se(8)(CN)(6)](2-/3-), and trans-[Re(4)Os(2)Se(8)(CN)(6)](2-/3-) couples at E(1/2) = -1.843, -0.760, and -1.031 V vs FeCp(2)(0/+), respectively, in addition to other redox processes. Accordingly, reduction of [Re(5)OsSe(8)(CN)(6)](3-) with sodium amalgam and [Re(4)Os(2)Se(8)(CN)(6)](2-) with cobaltocene produces the 25-electron clusters [Re(5)OsSe(8)(CN)(6)](4-) and [Re(4)Os(2)Se(8)(CN)(6)](3-). EPR spectra of these S = 1/2 species in frozen DMF solutions exhibit isotropic signals with g = 1.46 for the monoosmium cluster and g = 1.74 and 1.09 for the respective cis and trans isomers of the diosmium cluster. In each case, results from DFT calculations show the unpaired spin to delocalize to some extent into the pi* orbitals of the cyanide ligands, suggesting the possibility of magnetic superexchange. Reaction of [Re(5)OsSe(8)(CN)(6)](3-) with [Ni(H(2)O)(6)](2+) in aqueous solution generates the porous Prussian blue analogue Ni(3)[Re(5)OsSe(8)(CN)(6)](2).32H(2)O; however, the tendency of the 25-electron clusters to oxidize in water prohibits their use in reactions of this type. Instead, a series of cyano-bridged assemblies, [Re(6-n)Os(n)Se(8)[CNCu(Me(6)tren)](6)](9+) (n = 0, 1, 2; Me(6)tren = tris(2-(dimethylamino)ethyl)amine), were synthesized to permit comparison of the exchange coupling abilities of clusters with 23-25 electrons. As expected, the results of magnetic susceptibility measurements show no evidence for exchange coupling in the assemblies containing the 23- and 24-electron clusters, but reveal the presence of weak ferromagnetic coupling in [Re(4)Os(2)Se(8)[CNCu(Me(6)tren)](6)](9+). Assuming all cluster-Cu(II) exchange interactions to be equivalent, the data were fit to give an estimated coupling strength of J = 0.4 cm(-1). To our knowledge, the ability of such clusters to participate in magnetic exchange coupling has never previously been demonstrated.     

Synthesis and structural characterization of bi- and trimetallic octacyanometalate(IV) complexes: [Delta,Lambda-MII(en)3][cis-MII(en)2(OH2)][MIV(CN)8].2H2O and [cis-MII(en)2(OH2)]2[(mu-NC)2MIV(CN)6].4H2O (MII = Mn, Co, Ni; MIV = Mo, W)

Treatment of [M(II)(en)(3)][OTs](2) or methanolic ethylenediamine solutions containing transition metal p-toluenesulfonates (M(II) = Mn, Co) with aqueous K(4)M(IV)(CN)(8).2H(2)O or Cs(3)M(V)(CN)(8) (M(IV) = Mo, W; M(V) = Mo) affords crystalline clusters of [M(II)(en)(3)][cis-M(II)(en)(2)(OH(2))(mu-NC)M(IV)(CN)(7)].2H(2)O (M(IV) = Mo; M(II) = Mn, 1; Ni, 5; M(IV) = W; M(II) = Mn, 2; Ni, 6) and [cis-M(II)(en)(2)(OH(2))](2)[(mu-NC)(2)M(IV)(CN)(6)].4H(2)O (M(IV) = Mo; M(II) = Co, 3; Ni, 7; M(IV) = W; M(II) = Co, 4) stoichiometry. Each cluster contains cis-M(II)(en)(2)(OH(2))(mu-NC)(2+) units that likely result from dissociative loss of en from [M(II)(en)(3)](2+), affording cis-M(II)(en)(2)(OH(2))(2)(2+) intermediates that are trapped by M(IV)(CN)(8)(4-).     

Synthesis and reactions of group 6 metal half-sandwich complexes of 2,2-dicyanoethylene-1,1-dichalcogenolates [(Cp*)M[E(2)C=C(CN)(2)](2)]-(M = Mo,W; E = S,Se)

A series of group 6 transition metal half-sandwich complexes with 1,1-dichalcogenide ligands have been prepared by the reactions of Cp*MCl(4)(Cp* = eta(5)-C(5)Me(5); M = Mo, W) with the potassium salt of 2,2-dicyanoethylene-1,1-dithiolate, (KS)(2)C=C(CN)(2) (K(2)-i-mnt), or the analogous seleno compound, (KSe)(2)C=C(CN)(2) (K(2)-i-mns). The reaction of Cp*MCl(4) with (KS)(2)C=C(CN)(2) in a 1:3 molar ratio in CH(3)CN gave rise to K[Cp*M(S(2)C=C(CN)(2))(2)] (M = Mo, 1a, 74%; M = W, 2a, 46%). Under the same conditions, the reaction of Cp*MoCl(4) with 3 equiv of (KSe)(2)C=C(CN)(2) afforded K[Cp*Mo(Se(2)C=C(CN)(2))(2)] (3a) and K[Cp*Mo(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))] (4) in respective yields of 45% and 25%. Cation exchange reactions of 1a, 2a, and 3a with Et(4)NBr resulted in isolation of (Et(4)N)[Cp*Mo(S(2)C=C(CN)(2))(2)] (1b), (Et(4)N)[Cp*W(S(2)C=C(CN)(2))(2)] (2b), and (Et(4)N)[Cp*Mo(Se(2)C=C(CN)(2))(2)] (3b), respectively. Complex 4 crystallized with one THF and one CH(3)CN molecule as a three-dimensional network structure. Inspection of the reaction of Cp*WCl(4) with (KSe)(2)C=C(CN)(2) by ESI-MS revealed the existence of three species in CH(3)CN, [Cp*W(Se(2)C=C(CN)(2))(2)]-, [Cp*W(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))]-, and [Cp*W(Se(Se(2))C=C(CN)(2))(2)]-, of which [Cp*W(Se(2)C=C(CN)(2))(Se(Se(2))C=C(CN)(2))]-(5) was isolated as the main product. Treatment of 2a with 1/4 equiv of S(8) in refluxing THF resulted in sulfur insertion and gave rise to K[Cp*W(S(2)C=C(CN)(2))(S(S(2))C=C(CN)(2))](6), which crystallized with two THF molecules forming a three-dimensional network structure. 6 can also be prepared by refluxing 2a with 1/4 equiv of S(8) in THF. 3a readily added one Se atom upon treatment with 1 mol of Se powder in THF to give 4 in high yield, while the treatment of 3a or 4 with 2 equiv of Na(2)Se in THF led to formation of a dinuclear complex [(Cp*Mo)(2)(mu-Se)(mu-Se(Se(3))C=C(CN)(2))] (7). The structure of 7 consists of two Cp*Mo units bridged by a Se(2-) and a [Se(Se(3))C=C(CN)(2)](2-) ligand in which the triselenido group is arranged in a nearly linear way (163 degrees). The reaction of 2a with 2 equiv of CuBr in CH(3)CN yielded a trinuclear complex [Cp*WCu(2)(mu-Br)(mu(3)-S(2)C=C(CN)(2))(2)] (8), which crystallized with one CH(3)CN and generated a one-dimensional chain polymer through bonding of Cu to the N of the cyano groups.     

The pH dependent nuclearity variation of {Mo(154-x)}-type polyoxomolybdates and tectonic effect on their aggregations

The pH dependence of the structures of {Mo(154-x)} mixed-valence oxomolybdate giant clusters were investigated by synchrotron X-ray diffraction of systematically prepared crystals containing [Mo138O410(OH)20(OH2)46](40-) (1), [Mo138O410(OH)20(OH2)38](40-) (2), [Mo138O406(OH)16(OH2)46](28-) (3), [Mo142O400(OH)52(OH2)38](28-) (4), [Mo142O432(OH2)58](40-) (5), [Mo148O436(OH)15(OH2)56](27-) (6), [Mo150O451(OH)5(OH2)61](35-) (7), and both [Mo150O442.5(OH)11.5(OH2)64](24.5-) and [Mo152O446(OH)20(OH2)54](28-) (8). Crystals 1, 4, and 5 contain discrete clusters while intercluster Mo-O-Mo bonds connect the clusters into chains in crystal 7, into two-dimensional networks in crystals 2 and 3, and into a three-dimensional framework structure in crystal 6. Crystal 8 contains both discrete and linearly catenated clusters: discrete {Mo150} are located between the chains of {Mo152}. Direct correlation was observed between the nuclearity of the clusters with the pH of the mother liquor. On the other hand, the geometries of extended structures do not show apparent correlation with the pH. They turned out to be governed by the tectonics of the component clusters. The pH of the mother liquor exerts influence on the extended structure through the structures of the constituent clusters.     

Solid-state coordination chemistry: influences of (M(terpyridyl))(M = Fe(III), Cu(II), Ni(II)) subunits on molybdenum oxide structures

The hydrothermal reactions of Na2MoO4 x 2H2O and 2,2':6',2"-terpyridine with appropriate salts of Fe(II), Cu(II), and Zn(II) yield a variety of mixed metal oxide phases. The Cu(II) system affords the molecular cluster [Cu(terpy)MoO4].3H2O (MOXI-40 x 3H2O), as well as a one-dimensional material [Cu(terpy)Mo2O7](MOXI-41) which is constructed from (Mo4O14)4- clusters linked through (Cu(terpy))2+ units. In constrast, the Zn(II) phase of stoichiometry identical to that of MOXI-41, [Zn(terpy)Mo2O7](MOXI-42), exhibits a one-dimensional structure characterized by a (Mo2O7)n2n- chain decorated with peripheral (Zn(terpy))2+ subunits. The iron species [(Fe(terpy))2Mo4O12](MOXI-43) is also one-dimensional but exhibits [(Fe(terpy))2(MoO4)2]2+ rings linked through (MoO4)2- tetrahedra. A persistent structural motif which appears in MOXI-40, MOXI-41, and MOXI-43 is the [(M(terpy))2(MoO4)2]n cluster with a cyclic )(M2Mo2O4) core. In general, the secondary metal sites M(II, III) are effective bridging groups between molybdate subunits of varying degrees of aggregation. Furthermore, the ligands passivate the bimetallic oxide from spatial extension in two or three dimensions and provide a routine entree into low-dimensional structural types of the molybdenum oxide family of materials.     

Synthesis and reactivity of W3Te74+ clusters and chalcogen exchange in the M3Q7 (M = Mo, W; Q = S, Se, Te) cluster family

Heating WTe(2), Te, and Br(2) at 390 degrees C followed by extraction with KCN gives [W(3)Te(7)(CN)(6)](2-). Crystal structures of double salts Cs(3.5)K{[W(3)Te(7)(CN)(6)]Br}Br(1.5).4.5H(2)O (1), Cs(2)K(4){[W(3)Te(7)(CN)(6)](2)Cl}Cl.5H(2)O (2), and (Ph(4)P)(3){[W(3)Te(7)(CN)(6)]Br}.H(2)O (3) reveal short Te(2)...X (X = Cl, Br) contacts. Reaction of polymeric Mo(3)Se(7)Br(4) with KNCSe melt gives [Mo(3)Se(7)(CN)(6)](2-). Reactions of polymeric Mo(3)S(7)Br(4) and Mo(3)Te(7)I(4) with KNCSe melt (200-220 degrees C) all give as final product [Mo(3)Se(7)(CN)(6)](2)(-) via intermediate formation of [Mo(3)S(4)Se(3)(CN)(6)](2-)/[Mo(3)SSe(6)(CN)(6)](2-) and of [Mo(3)Te(4)Se(3)(CN)(6)](2-), respectively, as was shown by ESI-MS. (NH(4))(1.5)K(3){[Mo(3)Se(7)(CN)(6)]I}I(1.5).4.5H(2)O (4) was isolated and structurally characterized. Reactions of W(3)Q(7)Br(4) (Q = S, Se) with KNCSe lead to [W(3)Q(4)(CN)(9)](5-). Heating W(3)Te(7)Br(4) in KCNSe melt gives a complicated mixture of W(3)Q(7) and W(3)Q(4) derivatives, as was shown by ESI-MS, from which E(3)[W(3)(mu(3)-Te)(mu-TeSe)(3)(CN)(6)]Br.6H(2)O (5) and K(5)[W(3)(mu(3)-Te)(mu-Se)(3)(CN)(9)] (6) were isolated. X-ray analysis of 5 reveals the presence of a new TeSe(2-) ligand. The complexes were characterized by IR, Raman, electronic, and (77)Se and (125)Te NMR spectra and by ESI mass spectrometry.     

Factors affecting the solid-state structure and dimensionality of mercury cyanide/chloride double salts, and NMR characterization of coordination geometries

In the reaction of organic monocationic chlorides or coordinatively saturated metal-ligand complex chlorides with linear, neutral Hg(CN)(2) building blocks, the Lewis-acidic Hg(CN)(2) moieties accept the chloride ligands to form mercury cyanide/chloride double salt anions that in several cases form infinite 1-D and 2-D arrays. Thus, [PPN][Hg(CN)(2)Cl].H(2)O (1), [(n)Bu(4)N][Hg(CN)(2)Cl].0.5 H(2)O (2), and [Ni(terpy)(2)][Hg(CN)(2)Cl](2) (4) contain [Hg(CN)(2)Cl](2)(2-) anionic dimers ([PPN]Cl = bis(triphenylphosphoranylidene)ammonium chloride, [(n)Bu(4)N]Cl = tetrabutylammonium chloride, terpy = 2,2':6',6' '-terpyridine). [Cu(en)(2)][Hg(CN)(2)Cl](2) (5) is composed of alternating 1-D chloride-bridged [Hg(CN)(2)Cl](n)(n-) ladders and cationic columns of [Cu(en)(2)](2+) (en = ethylenediamine). When [Co(en)(3)]Cl(3) is reacted with 3 equiv of Hg(CN)(2), 1-D [[Hg(CN)(2)](2)Cl](n)(n-) ribbons and [Hg(CN)(2)Cl(2)](2-) moieties are formed; both form hydrogen bonds to [Co(en)(3)](3+) cations, yielding [Co(en)(3)][Hg(CN)(2)Cl(2)][[Hg(CN)(2)](2)Cl] (6). In [Co(NH(3))(6)](2)[Hg(CN)(2)](5)Cl(6).2H(2)O (7), [Co(NH(3))(6)](3+) cations and water molecules are sandwiched between chloride-bridged 2-D anionic [[Hg(CN)(2)](5)Cl(6)](n)(6n-) layers, which contain square cavities. The presence (or absence), number, and profile of hydrogen bond donor sites of the transition metal amine ligands were observed to strongly influence the structural motif and dimensionality adopted by the anionic double salt complex anions, while cation shape and cation charge had little effect. (199)Hg chemical shift tensors and (1)J((13)C,(199)Hg) values measured in selected compounds reveal that the NMR properties are dominated by the Hg(CN)(2) moiety, with little influence from the chloride bonding characteristics. delta(iso)((13)CN) values in the isolated dimers are remarkably sensitive to the local geometry.     

Complexation of molybdenum(V) with glycolic acid: an unusual orientation of glycolato ligand in {Mo2O4}2+ complexes

(PyH)5[Mo(V)OCl4(H2O)]3Cl2 and (PyH)n[Mo(V)OBr4]n reacted with glycolic acid (H2glyc) or its half-neutralized ion (Hglyc(-)) to afford a series of novel glycolato complexes based on the {Mo(V)2O4}2+ structural core: (PyH)3[Mo2O4Cl4(Hglyc)]. (1)/ 2CH 3CN (1), (PyH) 3[Mo 2O 4Br 4(Hglyc)].Pr(i)OH(2), (PyH)2[Mo2O4(glyc) 2Py 2] (3), (PyH) 4[Mo 4O 8Cl 4(glyc) 2].2EtOH (4), and [Mo 4O 8(glyc) 2Py 4] (5) (Py = pyridine, C 5H 5N; PyH(+) = pyridinium cation, C 5H 5NH (+) and glyc (2-) = a doubly ionized glycolate, (-)OCH 2COO (-)). The compounds were fully characterized by X-ray crystallography and infrared spectroscopy. The Hglyc (-) ion binds to the {Mo 2O 4} (2+) core through a carboxylate end in a bidentate bridging manner, whereas the glyc (2-) ion adopts a chelating bidentate coordination through a deprotonated hydroxyl group and a monodentate carboxylate. The orientations of glyc (2-) ions in 3- 5 are such that the alkoxyl oxygen atoms occupy the sites opposite the multiply bonded oxides. {(C6H5) 4P}[Mo(VI)O 2(glyc)(Hglyc)] ( 6), an oxidized complex, features a reversed orientation of the glyc(2-) ion. The theoretical DFT calculations on the [Mo(V)2O4(glyc) 2Py 2](2-) and [Mo(VI)O2(glyc)2](2-) ions confirm that binding of glycolate with the alkoxyl oxygen to the site opposite the MoO bond is energetically more favorable in {Mo(V)2O4}(2+) species, whereas a reversed orientation of the ligand is preferred in Mo(VI) complexes. An explanation based on the orbital analysis is put forward.     

N-对R苯基氮杂15冠5八钼多酸钠超分子配合物的合成与结构

为研究大环化合物对客体分子的选择性, 合成了通式为[NaL(Et2O)]2Na2Mo8O26的三种新型N-对R苯基氮杂15冠5八钼多酸钠超分子配合物(其中L分别为: N-苯基氮杂15冠5、N-对氯苯基氮杂15冠5和N-对甲苯基氮杂15冠5), 进行了元素分析, 红外光谱与核磁共振等结构参数的表征, 对R基为CH3的标题配合物作了X射线四圆衍射测定, 该晶体属单斜晶系, 空间群为P21/a,a=1.4590(4)nm, b=1.3817(3)nm, c=1.7639(5)nm, β=112.67(2)°, V=3.281(1)nm^3, Mr=2021.3, Dc=2.11g/cm^3,μ=2.37mm^-^1, F(000)=2048, R=0.045和Rw=0.057, 与[Na.(DB18C6)(CH3OH)M6O19和[Na(DB24C8)]2M6O19进行比较,结果表明: 大环化合物不仅对客体金属离子有分子识别性, 而且对与之抗衡的多酸阴离子也具有影响。     

Construction of Ag/1,2,4-triazole/polyoxometalates hybrid family varying from diverse supramolecular assemblies to 3-d Rod-packing framework

Eight members of the Ag/1,2,4-triazole/polyoxometalates (POMs) hybrid supramolecular family, namely, [Ag4(dmtrz)4][Mo8O26] (dmtrz=3,5-dimethyl-1,2,4-triazole, 1), [Ag6(3atrz)6][PMo12O40]2.H2O (3atrz=3-amino-1,2,4-triazole, 2), [Ag2(3atrz)2]2[HPMoVI10MoV2O40] (3), [Ag2(dmtrz)2]2[HPMoVI10MoV2O40] (4), [Ag2(trz)2]2[Mo8O26] (trz=1,2,4-triazole, 5), [Ag2(3atrz)2][Ag2(3atrz)2(Mo8O26)] (6), [Ag4(4atrz)2Cl][Ag(Mo8O26)] (4atrz=4-amino-1,2,4-triazole, 7), and [Ag5(trz)4]2[Ag2(Mo8O26)].4H2O (8), were synthesized through hydrothermal reactions of 1,2,4-triazole or its derivatives with appropriate silver salts and molybdates. Crystal structure analysis reveals that the POM-dependent Ag-1,2,4-triazolate units in these hybrid compounds form a novel tetranuclear cluster (1), a unique double calix[3]arene-shaped hexamer (2), zigzag chains (5 and 6), helix chains (3, 4, and 8), and an interesting looped chain (7). A series of hydrogen bonding-based supramolecular assemblies varying among the 0-D+0-D (1 and 2), 0-D+1-D (3 and 4), 1-D+1-D (5 and 7), and 1-D+2-D (6) modes between the organomatic cations and POM anions were observed in these structures. Moreover, the inorganic chain [Ag(Mo8O26)]n3n- in 7 constructed by the building block [Mo8O26]4- linked only via single Ag+ ion is unprecedented. Compound 8 is the first high-dimensional framework constructed from the [Ag2(Mo8O26)]n2n- rod-shaped subunits. These hybrid supramolecular compounds present interesting photochemical properties. The spectroscopic experiments show that they not only are potential semiconductor materials but also have interesting photoluminescence phenomena, including O-->Mo [LMCT] and intraligand [pi-pi*] emissions generated by internal heavy metal effect.     

Preparation and properties of the full series of cuboidal clusters [Mo(x)W4-xSe4(H2O)12]n+ (n = 4-6) and their derivatives

Hydrothermal reactions between incomplete cuboidal cluster aqua complexes [M3Q4(H2O)9]4+ and M(CO)6 (M = Mo, W; Q = S, Se) offer easy access to the corresponding cuboidal clusters M4Q4. The complete series of homometal and mixed Mo/W clusters [Mo(x)W4-xQ4(H2O)12]n+ (x = 0-4, n = 4-6) has been prepared. Upon oxidation of the mixed-metal clusters, it is the W atom which is lost, allowing selective preparation of new trinuclear clusters [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+. The aqua complexes were converted by ligand exchange reactions into dithiophosphato and thiocyanato complexes, and crystal structures of [W4S4((EtO)2PS2)6], [MoW3S4((EtO)2PS2)6], [Mo4Se4((EtO)2PS2)6], [W4Se4((i-PrO)2PS2)6], and (NH4)6[W4Se4(NCS)12]-4H20 were determined. Cyclic voltammetry was performed on [Mo(x)W4-xCO4(H2O)12]n+, showing reversible redox waves 6+/5+ and 5+/4+. The lower oxidation states are more difficult to access as the number of W atoms increases. The [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+ species were derivatized into [Mo2WSe4(acac)3(py)3]+ and [MoW2Se4(acac)3(py)3]+, which were also studied by CV. When appropriate, the products were also characterized by FAB-MS and NMR (31P, 1H) data.     

Stabilization of reduced molybdenum-iron-sulfur single- and double-cubane clusters by cyanide ligation

Recent work has shown that cyanide ligation increases the redox potentials of Fe(4)S(4) clusters, enabling the isolation of [Fe(4)S(4)(CN)4]4-, the first synthetic Fe(4)S(4) cluster obtained in the all-ferrous oxidation state (Scott, T. A.; Berlinguette, C. P.; Holm, R. H.; Zhou, H.-C. Proc. Natl. Acad. Sci. U.S.A. 2005, 102, 9741). The generality of reduced cluster stabilization has been examined with MoFe(3)S(4) clusters. Reaction of single-cubane [(Tp)MoFe(3)S(4)(PEt(3))3]1+ and edge-bridged double-cubane [(Tp)2Mo(2)Fe(6)S(8)(PEt(3))4] with cyanide in acetonitrile affords [(Tp)MoFe(3)S(4)(CN)3]2- (2) and [(Tp)2Mo(2)Fe(6)S(8)(CN)4]4- (5), respectively. Reduction of 2 with KC(14)H(10) yields [(Tp)MoFe(3)S(4)(CN)3]3- (3). Clusters were isolated in approximately 70-90% yields as Et(4)N+ or Bu(4)N+ salts; clusters 3 and 5 contain all-ferrous cores, and 3 is the first [MoFe(3)S(4)]1+ cluster isolated in substance. The structures of 2 and 3 are very similar; the volume of the reduced cluster core is slightly larger (2.5%), a usual effect upon reduction of cubane-type Fe(4)S(4) and MFe(3)S(4) clusters. Redox potentials and 57Fe isomer shifts of [(Tp)MoFe(3)S(4)L3]2-,3- and [(Tp)2Mo(2)Fe(6)S(8)L(4)]4-,3- clusters with L = CN-, PhS-, halide, and PEt3 are compared. Clusters with pi-donor ligands (L = halide, PhS) exhibit larger isomer shifts and lower (more negative) redox potentials, while pi-acceptor ligands (L = CN, PEt3) induce smaller isomer shifts and higher (less-negative) redox potentials. When the potentials of 3/2 and [(Tp)MoFe(3)S(4)(SPh)3]3-/2- are compared, cyanide stabilizes 3 by 270 mV versus the reduced thiolate cluster, commensurate with the 310 mV stabilization of [Fe(4)S(4)(CN)4]4- versus [Fe(4)S(4)(SPh)4]4- where four ligands differ. These results demonstrate the efficacy of cyanide stabilization of lower cluster oxidation states. (Tp = hydrotris(pyrazolyl)borate(1-)).     

Syntheses, structures, and magnetic properties of the face-centered cubic clusters [Tp(8)(H(2)O)(12)M(6)Fe(8)(CN)(24)](4+) (M = Co, Ni)

Reactions between K[TpFe(CN)3] (Tp- = hydrotris(1-pyrazolyl)borate) and M(ClO4)2 x 6H2O (M = Co or Ni) in a mixture of acetonitrile and methanol afford, upon crystallization via THF vapor diffusion, [Tp8(H2O)12Co6Fe8(CN)24](ClO4)4.12THF x 7H2O (1) and [Tp8(H2O)12Ni6Fe8(CN)24](ClO4)4.12THF x 7H2O (2). Both compounds contain cyano-bridged clusters with a face-centered cubic geometry, wherein octahedral CoII or NiII centers are situated at the face-centering sites. The results of variable-temperature magnetic susceptibility measurements indicate the presence of ferromagnetic exchange coupling within both molecules to give ground states of S = 7 and 10, respectively. Low-temperature magnetization data reveal significant zero-field splitting, with the best fits for the Co6Fe8 and Ni6Fe8 clusters yielding D = -0.54 and 0.21 cm-1, respectively; ac magnetic susceptibility measurements performed on both samples showed no evidence of the slow relaxation effects associated with single-molecule magnet behavior.     

Edge-bridged Mo2Fe6S8 to pN-type Mo2Fe6S9 cluster conversion: structural fate of the attacking sulfide/selenide nucleophile

Reaction of the edge-bridged double cubane cluster [(Tp)(2)M(2)Fe(6)S(8)(PEt(3))(4)] (1; Tp = hydrotris(pyrazolyl)borate(1-)) with hydrosulfide affords the clusters [(Tp)(2)M(2)Fe(6)S(9)(SH)(2)](3)(-)(,4)(-) (M = Mo (2), V), which have been established as the first structural (topological) analogues of the P(N) cluster of nitrogenase. The synthetic reaction is an example of core conversion, resulting in the transformation M(2)Fe(6)(mu(3)-S)(6)(mu(4)-S)(2) (C(i)) --> M(2)Fe(6)(mu(2)-S)(2)(mu(3)-S)(6)(mu(6)-S) (C(2)(v)), the reaction pathway of which is unknown. The most prominent structural feature of P(N)-type clusters is the mu(6)-S atom, which bridges six iron atoms in two MFe(3)S(3) cuboidal halves of the cluster. The initial issue in core conversion is the origin of the mu(6)-S atom. Utilizing SeH(-) as a surrogate reactant for SH(-) in the system 1/SeH(-)/L(-) in acetonitrile, a series of selenide clusters [(Tp)(2)Mo(2)Fe(6)S(8)SeL(2)](3)(-) (L(-) = SH(-) (4), SeH(-) (5), EtS(-) (6), CN(-) (7)) was prepared. The electrospray mass spectra of 4 and 6 revealed inclusion of one Se atom in each cluster, and (1)H NMR spectra and crystallographic refinements of 4-7 indicated that this atom was disordered over the two mu(2)-S/Se positions. The clusters {[(Tp)(2)Mo(2)Fe(6)S(9)](mu(2)-S)}(2)(5)(-) (8) and {[(Tp)(2)Mo(2)Fe(6)S(8)Se](mu(2)-Se)}(2)(5)(-) (9) were prepared from 2 and 5, respectively, and shown to be isostructural. They consist of two P(N)-type cluster units bridged by two mu(2)-S or mu(2)-Se atoms. It is concluded that, in the preparation of 2, the probable structural fate of the attacking nucleophile is as a mu(2)-S atom, and that the mu(3)-S and mu(6)-S atoms of the product cluster derive from precursor cluster 1. Cluster fragmentation during P(N)-type cluster synthesis is unlikely.     

Synthesis, characterization, and photoresponsive properties of a series of Mo(IV)-Cu(II) complexes

Six Mo(IV)-Cu(II) complexes, [Cu(tpa)](2)[Mo(CN)(8)]·15H(2)O (1, tpa = tris(2-pyridylmethyl)amine), [Cu(tren)](2)[Mo(CN)(8)]·5.25H(2)O (2, tren = tris(2-aminoethyl)amine), [Cu(en)(2)][Cu(0.5)(en)][Cu(0.5)(en)(H(2)O)][Mo(CN)(8)]·4H(2)O (3, en = ethylenediamine), [Cu(bapa)](3)[Mo(CN)(8)](1.5)·12.5H(2)O (4, bapa = bis(3-aminopropyl)amine), [Cu(bapen)](2)[Mo(CN)(8)]·4H(2)O (5, bapen = N,N'-bis(3-aminopropyl)ethylenediamine), and [Cu(pn)(2)][Cu(pn)][Mo(CN)(8)]·3.5H(2)O (6, pn = 1,3-diaminopropane), were synthesized and characterized. Single-crystal X-ray diffraction analyses show that 1-6 have different structures varying from trinuclear clusters (1-2), a one-dimensional belt (3), two-dimensional grids (4-5), to a three-dimensional structure (6). Magnetic and ESR measurements suggest that 1-6 exhibit thermally reversible photoresponsive properties on UV light irradiation through a Mo(IV)-to-Cu(II) charge transfer mechanism. A trinuclear compound [Cu(II)(tpa)](2)[Mo(V)(CN)(8)](ClO(4)) (7) was synthesized as a model of the photoinduced intermediate.     

Template synthesis of [(Mo(V)2O4)(O3PCH2PO3)]n clusters (n = 3, 4, 10): solid state and solution studies

The influence of three exogenous ligands (acetate, formate and carbonate) on the condensation process of the [Mo2O4]2+ dioxocation with the [O3PCH2PO3](4-) group has been investigated. Four cyclic or bicyclic compounds have been isolated and characterized by X-ray diffraction studies. Two closely related acetato and formato ovoidal duodecanuclear compounds, Na24[Na4(H2O)6[(Mo2O4)10(O3PCH2PO3)10(CH3COO)8(H2O)4]].103H2O (1) and Na28[Na2[(Mo2O4)10(O3PCH2PO3)10(HCOO)10]].110H2O (2), respectively, have been obtained. Their structures can be described as two interconnected nonequivalent wheels, delimiting a large cavity. When the condensation is performed in similar conditions but replacing carboxylato groups by carbonato ligands, the ellipsoidal octanuclear Na11[Na(H2O)2[(Mo2O4)4(O3PCH2PO3)4(CO3)2]].70H2O (3) compound is isolated. 31P NMR spectroscopic studies have shown that complexes 1 and 3 are stable in solution at room temperature. Nevertheless, on heating an aqueous solution of 3, the Na8[(Mo2O4)3(O3PCH2PO3)3(MoO4)].18H2O (4) complex, free of carbonato groups, is obtained. 4 is a hexanuclear Mo(V) wheel encapsulating a tetrahedral [Mo(VI)O4](2-) anion. Its rational synthesis using a controlled Mo(V)/Mo(VI) ratio is also presented.     

(EDT-TTF-CONH2)6[Re6Se8(CN)6], a metallic Kagome-type organic-inorganic hybrid compound: electronic instability, molecular motion, and charge localization

(EDT-TTF-CONH2)6[Re6Se8(CN)6], space group R, was prepared by electrocrystallization from the primary amide-functionalized ethylenedithiotetrathiafulvalene, EDT-TTF-CONH2 (E(1/2)1 = 0.49 V vs SCE in CH3CN), and the molecular cluster tetraanion, [Re6Se8(CN)6]4- (E(1/2) = 0.33 V vs SCE in CH3CN), equipped with hydrogen bond donor and hydrogen bond acceptor functionalities, respectively. Its Kagome topology is unprecedented for any TTF-based materials. The metallic state observed at room temperature has a strong two-dimensional character, in coherence with the Kagome lattice symmetry, and the presence of minute amounts of [Re6Se8(CN)6](3-)* identified by electron spin spectroscopy. A structural instability toward a distorted form of the Kagome topology of lesser symmetry is observed at ca. 180 K. The low-temperature structure is associated with a localized, electrically insulating electronic ground state and its magnetic susceptibility accounted for by a model of uniform chains of localized S = 1/2 spins in agreement with the 100 K triclinic crystal structure and band structure calculations. A sliding motion, within one out of the three (EDT-TTF-CONH2)2 dimers coupled to the [Re6Se8(CN6)(3-)*]/[Re6Se8(CN6)4-] proportion at any temperature, and the electronic ground state of the organic-inorganic hybrid material are analyzed on the basis of ESR, dc conductivity, 1H spin-lattice relaxation, and static susceptibility data which qualify a Mott localization in [EDT-TTF-CONH2]6[Re6Se8(CN)6]. The coupling between the metal-insulator transition and a structural transition allows for the lifting of a degeneracy due to the ternary axis in the high temperature, strongly correlated metallic phase which, in turn, leads to Heisenberg chains at low temperature.     

Oxidative scission of a Mo-Mo quadruple bond

Two compounds containing the cations Mo2(DPhIP)4n+, n = 1 or 2 and DPhIP = the anion of 2,6-diphenyliminopiperidine, have been obtained by oxidation of the quadruply-bonded Mo2(DPhIP)4 species. The first oxidation process conserves the structure but results in a slight increase of the Mo-Mo distance from 2.114(1) to 2.136(2) A in [Mo2(DPhIP)4](PF6).2CH2Cl2 (1.2CH2Cl2). However, the second oxidation process breaks the dimolybdenum bond, giving a bioctahedral complex, [Mo2(DPhIP)4](BF4)2.5CH3CN.Et2O (2.5CH3CN.Et2O), with Mo...Mo separation of 2.9954(7) A. Crystallographic data for 1.2CH2Cl2 are space group C2/c, a = 17.1891(9) A, b = 17.807(1) A, c = 24.210(2) A, beta = 106.403(4) degrees, Z = 4; for 2.5CH3CN.Et2O, space group P2(1)/n, a = 16.523(5) A, b = 27.418(5) A, c = 18.163(3) A, beta = 93.48(2) degrees, Z = 4.