Molybdenum(VI) dioxo and oxo-imido complexes of fluorinated β-ketiminato ligands and their use in OAT reactions

Substitution of a methyl by a trifluoromethyl moiety in well-known β-ketimines afforded the ligands (Ar)NC(Me)CH(2)CO(CF(3)) (HL(H), Ar = C(6)H(5); HL(Me), A r= 2,6-Me(2)C(6)H(3); HL(iPr), Ar = 2,6-(i)Pr(2)C(6)H(3)). Subsequent complexation to the [MoO(2)](2+) core leads to the formation of novel complexes of general formula [MoO(2)(L(R))(2)] (R = H, 1; R = Me, 2; R = iPr, 3). For reasons of comparison the oxo-imido complex [MoO(N(t)Bu)(L(Me))(2)] (4) has also been synthesized. Complexes 1-4 were investigated in oxygen atom transfer (OAT) reactions using the substrate trimethylphosphine. The respective products after OAT, the reduced Mo(IV) complexes [MoO(PMe(3))(L(R))(2)] (R = H, 5; R = Me, 6; R = iPr, 7) and [Mo(N(t)Bu)(PMe(3))(L(Me))(2)] (8), were isolated. All complexes have been characterized by NMR spectroscopy, and 1-4 also by cyclic voltammetry. A positive shift of the Mo(VI)-Mo(V) reduction wave upon fluorination was observed. Furthermore, molecular structures of complexes 2, 4, 5, and 8 have been determined via single crystal X-ray diffraction analysis. Complex 8 represents a rare example of a Mo(IV) phosphino-imido complex. Kinetic measurements by UV-vis spectroscopy of the OAT reactions from complexes 1-4 to PMe(3) showed them to be more efficient than previously reported nonfluorinated ones, with ligand L' = (Ar)NC(Me)CH(2)CO(CH(3)) [MoO(2)(L')(2)] (9) and [MoO(N(t)Bu)(L')(2)] (10), respectively. Thermodynamic activation parameters ΔH(?) and ΔS(?) of the OAT reactions for complexes 2 and 4 have been determined. The activation enthalpy for the reaction employing 2 is significantly smaller (12.3 kJ/mol) compared to the reaction with the nonfluorinated complex 9 (60.8 kJ/mol). The change of the entropic term ΔS(?) is small. The reaction of the oxo-imido complex 4 to 8 revealed a significant electron-donating contribution of the imido substituent.     

Dioxo-molybdenum(VI) and mono-oxo-molybdenum(IV) complexes supported by new aliphatic dithiolene ligands: new models with weakened Mo=O bond characters for the arsenite oxidase active site

The cis-dioxo-molybdenum(VI) complexes, [MoO2(L(H))2]2- (1b), [MoO2(L(S))(2)]2- (2b), and [MoO2(L(O))2]2- (3b) (L(H) = cyclohexene-1,2-dithiolate, L(S) = 2,3-dihydro-2H-thiopyran-4,5-dithiolate, and L(O) = 2,3-dihydro-2H-pyran-4,5-dithiolate), with new aliphatic dithiolene ligands were prepared and investigated by infrared (IR) and UV-vis spectroscopic and electrochemical methods. The mono-oxo-molybdenum(IV) complexes, [MoO(L(H))2]2- (1a), [MoO(L(S))2]2- (2a), and [MoO(L(O))2]2- (3a), were further characterized by X-ray crystal structural determinations. The IR and resonance Raman spectroscopic studies suggested that these cis-dioxo molybdenum(VI) complexes (1b-3b) had weaker Mo=O bonds than the common Mo(VI)O2 complexes. Complexes 1b-3b also exhibited strong absorption bands in the visible regions assigned as charge-transfer bands from the dithiolene ligands to the cis-MoO2 cores. Because the oxygen atoms of the cis-Mo(VI)O2 cores are relatively nucleophilic, these complexes were unstable in protic solvents and protonation might occur to produce Mo(VI)O(OH), as observed with the oxidized state of arsenite oxidase.     

Electronic spectral studies of molybdenyl complexes. 2. MCD spectroscopy of [MoOS4]- centers

Magnetic circular dichroism (MCD) and absorption spectroscopies have been used to probe the electronic structure of [PPh4][MoO(p-SC6H4X)4] (X = H, Cl, OMe) and [PPh4][MoO(edt)2] complexes (edt = ethane-1,2-dithiolate). The results of density functional calculations (DFT) on [MoO(SMe)4]- and [MoO(edt)2]- model complexes were used to provide a framework for the interpretation of the spectra. Our analysis shows that the lowest energy transitions in [MoVOS4] chromophores (S4 = sulfur donor ligand) result from S-->Mo charge transfer transitions from S valence orbitals that lie close to the ligand field manifold. The energies of these transitions are strongly dependent on the orientation of the S lone-pair orbitals with respect to the Mo atom that is determined by the geometry of the ligand backbone. Thus, the lowest energy transition in the MCD spectrum of [PPh4][MoO(p-SC6H4X)4] (X = H) occurs at 14,800 cm-1, while that in [PPh4][MoO(edt)2] occurs at 11,900 cm-1. The identification of three bands in the absorption spectrum of [PPh4][MoO(edt)2] arising from LMCT from S pseudo-sigma combinations to the singly occupied Mo 4d orbital in the xy plane suggests that there is considerable covalency in the ground-state electronic structures of [MoOS4] complexes. DFT calculations on [MoO(SMe)4]- reveal that the singly occupied HOMO is 53% Mo 4dxy and 35% S p for the equilibrium C4 geometry. For [MoO(edt)2]- the steric constraints imposed by the edt ligands result in the S pi orbitals being of similar energy to the Mo 4d manifold. Significant S pseudo-sigma and pi donation may also weaken the Mo identical to O bond in [MoOS4] centers, a requirement for facile active site regeneration in the catalytic cycle of the DMSO reductases. The strong dependence of the energies of the bands in the absorption and MCD spectra of [PPh4][MoO(p-SC6H4X)4] (X = H, Cl, OMe) and [PPh4][MoO(edt)2] on the ligand geometry suggests that the structural features of the active sites of the DMSO reductases may result in an electronic structure that is optimized for facile oxygen atom transfer.     

[C6N2H18]2[Mo5O15(HPO4)2]·H2O的水热合成与结构表征

通过水热法合成了一个新化合物[C6N2H18]2[Mo5O15(HPO4)2]·H2O,并通过IR光谱、ICP、元素分析、差热与热重分析和X射线单晶衍射分析等手段进行了表征.结果表明,晶体属三方晶系,P3(2)21空间群,a=1.1231(1)nm,c=2.2802(5)nm,V=2.4911(7)nm3,Dx=2.835Mg/m3,Z=6,最后的一致性因子R=0.0227,wR=0.0675.阴离子中Mo5O15构成一环状结构,2个HPO4一个连在环的下方,一个连在环的上方,形成类似于“飞碟”状的结构,阳离子为2个质子化的四甲基乙二胺.     

Synthesis and structures of bis(dithiolene)molybdenum complexes related to the active sites of the DMSO reductase enzyme family

Structural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes are sought. These sites usually contain two pterin-dithiolene cofactor ligands and one protein-based ligand. Reaction of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R = Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum-(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to [MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes [Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- affordthe trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1- (Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]- (9, 10). In contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1-(14, 15), which have not been successfully decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(mu-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(mu-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3-5, 7-10, 12-14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations. Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)     

[Bu~4N]~3[Mo~2FeS~8O].(CH~2OH)~2簇合物的合成, 结构和性质研究

(NH4)2MoS~4、FeCl~3与乙二醇钠在乙二醇溶液中反应, 再与Bu~4NBr作用可得到一种M0-Fe-S簇合物[Bu~4N]~3[Mo~2FeS~8O].HOCH~2OH。其结构经X光晶体结构分析确定。并测定其红外光谱、紫外光谱、Mossbauer谱和电化学性质。该化合物可催化KBH~4转化乙炔还原为乙烯的反应。     

Synthesis and Crystal Structure of [H-amp]4[Mo8O26（DMF）2].2H2O（amp = 2-Amino-6-methyl-pyridine）

1INTRODUCTIONMetal-oxoclusterchemistryhasbeenactivelypurchasedduetotheinterestinchemistryitselfanditsvariousapplicationsinfieldssuchascatalysis,electronicconductivity,magnetism,nonlinearopti-calpropertiesandmedicine[1～3].Recently,anim-portantadvanceinmet…     

Synthesis and Structural Characterization of a Salt {[Co(Phen)_3][Mo_2S_2(μ-S)_2(edt)_2]}_2·(DMSO)_2·(Et_2O)(Phen = 1,10-Phenanthroline,edt=Ethane-1,2-dithiolate)

1 INTRODUCTION Dinuclear sulfido-bridged complexes with M2S2(μ-S)2 unit serving as building blocks for the construction of mixed-metal clusters are well docu- mented due to their rich structure diversities[1～3] as well as their potential applications in catalytic sys- tems and eletro/photonic materials[4, 5]. For example, reaction of [CpEt2Mo2S2(μ-S)2] with 2 equiv. of Co- (CO)3(NO) gave rise to a cubane-like cluster com- pound [CpEt2Mo2S2(μ-S)2Co2(CO)2][6]. In the case of[Mo…     

Hydrothermal synthesis, structure and quantum chemistry of transition metal complex supported by metal-oxo cluster [{Ni(phen)2}2(x-Mo8O26)]

A nickel-1,10-phenanthroline complex supported on an octamolybdate, [{Ni(phen)2}2(x- Mo8O26)], has been hydrothermally synthesized with MoO3, H2MoO4, Ni(OAc)2· 6H2O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P21/n space group, a = 1.2952(2), b = 1.6659(10), c = 1.3956(12) nm, b =106.273(8)°, V = 2.8906(5) nm3, Z = 2. 5604 observable reflections (I ＞2s(I)) were used for structure resolution and refinements to converge to final R1 = 0.0414, wR2 = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as x-isomer). The feature of x-[Mo8O26]4- is that it is composed of Mo6O6 ring and two MoO6 octahedra located at cap positions on opposite faces. The Mo6O6 ring contains two octahedral and four trigonal-bipyramidal MoVI atoms. Each x-[Mo8O26]4- unit is bonded with two [Ni(phen)2]2+ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo6O6 ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method.     

Synthesis and Structural Characterization of a Salt{[Co(Phen)3][Mo2S2(μ-S)2(edt)2]}2·(DMSO)2·(Et2O)(Phen = 1,10-Phenanthroline,edt = Ethane-1,2-dithiolate)

Reaction of [Et4N]2[Mo2S2(μ-S)2(edt)2] with CoCl2(6H2O and Phen in MeCN followed by recrystallization in DMSO/Et2O gave rise to dark-red block crystals of {[Co(Phen)3]- [Mo2S2(μ-S)2(edt)2]}2·(DMSO)2·(Et2O) 1 (C88H86Co2Mo4N12O3S18). 1 crystallizes in the monoclinic system, space group P21/c with a = 24.631(4), b = 16.117(3), c = 24.791(4) (A), β = 92.835°, V = 9829.3(3) (A)3, Z = 4, Mr = 2438.57, Dc = 1.648 g/cm3, F(000) = 4928, μ = 12.61 cm-1, R = 0.0936 and wR = 0.1682 for 12998 observed reflections with I > 2.0σ(I). In the structure of 1, the Co atom of the [Co(Phen)3]2+ dication is octahedrally coordinated by three Phen ligands. The Mo atom of the [Mo2S2(μ-S)2(edt)2]2- dianion is coordinated by two μ-S, one terminal S and two S atoms from edt, forming a distorted square pyramidal geometry. The mean Co-N and Mo…Mo bond distances are 2.139 and 2.872 (A), respectively.     

Synthesis and Crystal Structure of [H-amp]4[Mo8O26(DMF)2]·2H2O (amp = 2-Amino-6-methyl-pyridine)

The reaction of MoO2(acac)2 with 2-amino-6-methyl-pyridine (amp) in the mixed solvent of DMF (N,N-dimethylformamide) and water affords the title complex [H-amp]4- [Mo8O26(DMF)2]·2H2O which was characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis with the following crystallographic data: C30H54Mo8N10O30, Mr = 1802.35, monoclinic, P21/n, a = 8.631(1), b = 24.260(3), c = 13.351(2)A,β= 104.688(3)°, V = 2704.2(7) A3, Z = 2, Dc = 2.213 g/cm3, μ =1.890 mm－1 and F(000) = 1760. The final R = 0.0281 and Wr = 0.0620 for 4935 observed reflections with I > 2σ(I). X-ray structure analysis has confirmed the existence of γ-[Mo8O26]4－ anion in the molecule. Eight MoO6 distorted octahedra share edges with short terminal Mo-O bonds from 1.691(3) to 1.749(2)A, medium bonds from 1.868(2) to 1.965(2) A And long bonds from 2.059(2) to 2.450(2) A. In the terminal site there exist two DMF ligands bound to the Mo atom through O atoms with the Mo-ODMF bond length of 2.166(3) A, affording a bond strength of 0.433. A three-dimensional network structure was formed through hydrogen bonds.     

Hydrothermal Synthesis and Structure of a Novel Binuclear Molybdenum Complex with Oxalate Ligand,(enH2){NH4[Co(en)3][Mo2O7(C2O4)]}2·2H2O

The title complex (enH2){NH4[Co(en)3][Mo2O7(C2O4)]}2·2H2O (C18H70Co2Mo4- N16O24, Mr = 1396.52) was obtained under hydrothermal conditions and its crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 17.8023(8), b = 7.7527(4), c = 16.9781(4)A,β= 103.878(7)°, V = 2274.8(2) A3, Dc = 2.039 g/cm3, Z = 2,μ(MoKα) = 1.878 mm-1 and F(000) = 1408. The final R = 0.0410 and Wr = 0.1070 for 4065 observed reflections with I≥2σ(I). The crystal structure is composed of bi- nuclear [Mo2O7(C2O4)]4- anions, complex [Co(en)3]2+ cations, protonated ethylenediamine cations, ammonium cations and crystal water molecules, which are held together into a three-dimensional network via hydrogen-bonding interactions. The binuclear structure of [Mo2O7(C2O4)]4- consist of one MoO4 and one MoO6 octahedra through sharing a bridging oxygen atom, where the oxalate ligand acts as a bidentate ligand coordinating to the octahedral molybdenum atom though two deprotonated corboxylate groups.     

Directed synthesis of noncentrosymmetric molybdates using composition space analysis

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown. The relative phase stabilities for these products are dependent upon the reactant mole fractions in the initial reaction gel. This phase stability information was used to direct the synthesis of two new noncentrosymmetric compounds, using either (S)-(-)-3-aminoquinuclidine dihydrochloride or (R)-(+)-3-aminoquinuclidine dihydrochloride. [(R)-C7H16N2]2[Mo8O26] and [(S)-C7H16N2]2[Mo8O26] both crystallize in the noncentrosymmetric space group P2(1) (No. 4), which has the polar crystal class 2 (C2). The second-harmonic generation activities were measured on sieved powders. The structure-directing properties of the molybdate components in each compound were determined using bond valence sums. The structures of all five compounds were determined using single-crystal X-ray diffraction.     

新型Mo-Pb-S异四核簇合物 [Mo~3(PbI~3)S~4(dtp)~3(C~3H~4N~2)~3][(CH~3) ~2CO]~2 的合成和晶体结构

由[Mo~3(μ~3-O)(μ-S)~3(dtp)~4(H~2O)和PbI~3^-在咪唑存在下反应获得异四核混合簇[Mo~3(PbI~3)S~4(dtp)~3(C~3H~4N~2)~3][(CH~3)~2CO]~2(2)[dtp=S~2P(OC~2H~5)~2^-]。簇合物属斜方晶系,空间群P~b~c~a(No.61),晶胞参数为a=2.3590(3),b=1.9161(5),c=2.6458(9)nm,V=11.959(6)nm^3,Z=8。结构最终偏离因子R=0.067。此四核簇分子具有[Mo~3PbS~4]类立方烷簇芯,簇分子整体对称性接近C~3~v。在同一不对称单元中,簇分子的咪唑环以(NH)和溶剂丙酮分子的氧原子形成O---H---N氢键。     

Triruthenium carbonyl clusters derived from chiral aminooxazolines: synthesis and catalytic activity

Treatment of [Ru3(CO)12] with the chiral aminooxazolines (+)-2-amino-(4R)-phenyl-2-oxazoline (H2amphox), (+)-2-amino-(4R,5S)-indanyl-2-oxazoline (H2aminox) and (+)-2-(2-anilinyl)-(4R,5S)-indanyl-2-oxazoline (H2aninox) in THF at reflux temperature, affords the complexes [Ru3(mu-H)(mu3-kappa2-Hox-N,N)(CO)9] (H2ox = H2amphox, 1; H2aminox, 2) and [Ru3(mu-H)(mu-kappa2-Haninox-N,N)(CO)9] (3). In all cases, the activation of an N-H bond has occurred and the resulting amido fragment spans an edge of the metal triangle, while the N atom of the oxazoline ring is attached to the remaining metal atom (as in 1 and 2), or to one of the metal atoms of the bridged edge (as in 3). The use of 1-3 as catalyst precursors in the asymmetric hydrogen-transfer reduction of acetophenone and in the asymmetric cycloaddition of cyclopentadiene and acroleine is reported.     

Pentamethylcyclopentadienyl-iridium(III) complexes with pyridylamino ligands: synthesis and applications as asymmetric catalysts for Diels-Alder reactions

Reaction of the dimer [(Cp*IrCl)2(P-Cl)2] with chiral pyridylamino ligands (pyam, L1-L5) in the presence of NaSbF6 gave complexes [Cp*IrCl(pyam)][SbF6] 1-5 as diastereomeric mixtures, which have been fully characterised, including the X-ray molecular structure determination of the complexes (S(Ir),R(N),R(C))-[Cp*IrClL1][SbF6] 1a and (R(Ir),S(N),S(C))-[Cp*IrClL5][SbF6] 5a. Treatment of these cations with AgSbF6 affords the corresponding aqua species [Cp*Ir(pyam)(H2O)][SbF6]2 6-10 which have been also fully characterised. The molecular structure of the complex (S(Ir),R(N),R(C))-[Cp*IrL,(H2O)][SbF6]2 6 has been determined by X-ray diffractometric methods. The aqua complexes [Cp*Ir(pyam)(H2O)][SbF6]2 (6, pyam = L2 (7), L3 (8)) evolve to the cyclometallated species [Cp*Ir{kappa3(N,N',C)-(R)-(C6H4)CH(CH3)NHCH2C5NH4}][SbF6] (11), [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)-NHCH2C5NH4)}][SbF6] (12), and [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)NHCH2C9NH6)}][SbF6] (13) respectively, via intramolecular activation of an ortho C-H aryl bond. Complexes 6-10 are enantioselective catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene. Reaction occurs rapidly at room temperature with good exo : endo selectivity (from 81 : 19 to 98 : 2) and moderate enantioselectivity (up to 72%). The involved intermediate Lewis acid-dienophile compounds [Cp*Ir(pyam)(methacrolein)][SbF]2 (pyam = L4 (14), L5 (15)) have been isolated and characterised.     

Hydrothermal Synthesis, Crystal Structure and Fluorescent Property of a Novel Mo(Ⅴ) Phosphate [Zn(Mov6P4O31H10)2(C4H14N3)2]·2C4H13N3·8H2O

A new molybdenum phosphate [Zn(Mov6P4O31H10)2(C4H14N3)2]·2C4H13N3·8H2O 1 (C4H13N3 = diethylenetriamine) has been synthesized under hydrothermal condition. Single-crystal X-ray diffraction reveals that compound 1 crystallizes in the monoclinic, space group P21/n, a =13.1679(3), b = 22.1240(6), c = 13.6146(3) (A), β = 103.4847(7)°, V = 3856.95(16) (A)3,C16H90N12O70P8ZnMo12, Mr = 3035.41, Z = 2, Dc = 2.614 g/cm3, μ = 2.483 mm-1, F(000) = 2968, S = 1.014, the final R = 0.0196 and wR = 0.0506 for 7486 observed reflections (I ＞ 2σ(Ⅰ)). Compound 1 consists of two identical rings of six edge-sharing MoO6 octahedra interconnected by one ZnO6 octahedron, whereas the PO4 tetrahedra which share their apices with the MoO6 octahedra are only located on one side of each Mo6 ring. The 2-charge of polyanion [Zn(Mov6P4O31H10)2]2- unit is compensated in the crystal by two mono-protonated diethylenetriamines (C4H14N3)+. By hydrogen bonding interactions the polyanion of compound 1 is interconnected to form pseudo three dimensional molybdophosphate. Other characterizations by elemental analyses, IR spectrum and fluorescent spectrum are also described.     

Synthesis and Crystal Structure of Binuclear Oxomolybdenum(VI) Complex with Both o-Mercaptophenolate

1INTRoDUCTIONMolybdenumintheVandVIoxidationstatesformsaconsiderablenumberofoxocomplexes.Someofthemareactivecatalystsfortheoxidationoforganicsub-stracts[li'Allthesefactshavewidelyarousedchemists'interest.lnordertoobservetheeffectofthedonorgroupsonthedegreeofcomplexaggregationandonthecoor-dinationgeometry,thetitlecompoundwaspreparedbythereactionof(n-Bu'N)'-[Mo,O,,jwitho-mercaptophenolandthesinglecrystalswereobtained.Itcontainsa[Mo,O,j' core.Somereleventreportscanbefoundinthepreviousliter…     

Layered lanthanide molybdate pillared by chiral [lambda-Mo2O4EDTA]2-

Hydrothermal reactions of Na2[Mo2O4EDTA].5H2O and LnCl3.6H2O produce the chiral layered lanthanide molybdate oxides pillared by the chiral cluster ligand, [Ln(H2O)MoO4]2[lambda-Mo2O4EDTA] (Ln = Gd, 1; Eu, 2; Tb, 3; Y, 4). The tetradentate molybdate bridges Ln3+ to form a square grid structure, which is pillared by the chiral cluster ligand, [lambda-Mo2O4EDTA]2-, into a 3-D chiral framework structure. Strong VCD (vibrational circular dichroism) signals confirm the chirality of the bulk oxide materials. These bimetallic oxide materials are of highly thermal stability. The magnetic interactions between the Ln3+ ions in 1 and 3 are weak antiferromagnetic.     

Molybdocalixarene structure control via rim deprotonation. synthesis, characterization, and crystal structures of calix[4]arene Mo(VI) monooxo complexes and calix[4]arene alkali metal/Mo(VI) dioxo complexes

We report a series of calix[4]arene Mo(VI) dioxo complexes M2RC4MoO2 (M = alkali metal, R = H or Bu(t)) that were fully characterized by NMR, X-ray, IR, UV/vis, and elemental analysis. Molybdocalix[4]arene structures can be controlled via lower rim deprotonation, groups at para positions of calix[4]arene, and alkali metal counterions. Mono deprotonation at the lower rim leads to calix[4]arene Mo(VI) monooxo complexes RC4MoO (R = H, Bu(t), or allyl), and full deprotonation gives rise to calix[4]arene Mo(VI) dioxo complexes. Structural studies indicate that HC4 Mo(VI) dioxo complexes easily form polymeric structures via cation-pi interaction and coordination between different calixarene units. However, Bu(t)C4 Mo(VI) dioxo complexes tend to form dimers or tetramers due to steric hindrance of the tert-butyl groups at para positions in calixarene. The structures of the reduced side products A and C were determined by X-ray diffraction studies. The mechanism of RC4MoO formation from the reaction of calixarene monoanions with MoO2Cl2 appears to include the addition of a calixarene -OH group across a Mo=O bond.