Search

The synthesis and characterization of three novel keplerate-type compounds containing the {W72Mo60} mixed-metal core are reported. Complexes (NH4)72[{W6O21(H2O)6}12{Mo2O4(SeO4)}30]·150H2O·6(NH4)2SeO4 (1a) and (NH4)25(NH2Me2)47[{W6O21(H2O)6}12{Mo2O4(SeO4)}30]·130H2O·3(NH4)2SeO4 (1b) were prepared by ligand substitution from the acetate anionic complex [{W6O21(H2O)5(CH3COO)0.5}12{Mo2O4(CH3COO)}30]48− and selenate. The selenate anions in keplerate ions [{W6O21(H2O)6}12{Mo2O4(SeO4)}30]72− are very labile and easily aquate with the formation of [{W6O21(H2O)6}12{Mo2O4}30(SeO4)20(H2O)20]52−, which was isolated as (NH4)20(NH2Me2)32[{W6O21(H2O)6}12{Mo2O4}30(SeO4)20(H2O)20]·150H2O (2) and structurally characterized. In the crystal structure of 2 selenate has several coordination modes, preferentially bonding to the {Mo2O4}2+ units, and, additionally, to the {(W)W5} pentagonal blocks. The compounds have been characterized by elemental analysis, Raman, IR and 77Se NMR spectroscopy, and by ESI mass spectrometry. Capillary electrophoresis was used for characterization of keplerates in solution for the first time. [ABSTRACT FROM AUTHOR]

Abstract: Hydrothermal reaction of [Mo3S4(H2O)9]4+ with [Re(CO)5Br] at 140 °C in 4 M HCl gives a brown product, which upon treatment with KS2P(OEt)2 and recrystallyzation from an acetone/methanol mixture gives the title product via unstable [Mo3ReS4((EtO)2PS2)6]. The crystal structure of [Mo3ReS4(O)2(S2P(OEt)2)5] was determined. To cite this article: R. Llusar et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

Reaction of [Nb6O19]8- with H6TeO6 in water gives telluropentaniobate [(OH)TeNb5O18]6- (1) as single product, which was isolated as Na+ and mixed Na+/K+ salts. Crystal structures were determined for Na6[(OH)TeNb5O18]•15H2O (Na6-1) and K6Na[Nb5.5{Te(OH)}0.5O18.5]•26H2O (K6Na-1). Formation of 1 was monitored with electrospray ionization mass spectrometry (ESI-MS) and 125Te NMR techniques. Capillary electrophoresis was used to calculate electrophoretic mobilities and radii of the anionic species in solutions of [(OH)TeNb5O18]6- and [Nb6O19]8- in borate buffer. No condensation or degradation products were detected. Reactions of 1 with {Cp*Rh}2+ sources gives 1:1 and 2:1 hybrid polyoxometalate, which are present in solution as a mixture of isomers, as detected by 125Te NMR. The isomerism is related to various possibilities of coordination of {Cp*Rh}2+ to different {M3O3} faces, relative to the unique Te atom. According to ESI-MS experiments in water and methanol, rapid redistribution of the organometallic fragments between the 1:1 and 2:1 complexes takes place. The 1:1 complexes are more stable in water, while 2:1 complexes dominate in methanol. X-ray structural analysis of the crystals isolated from 2:1 reaction mixture allowed identification of Na3[{Cp*Rh}2TeNb5O19]•24H2O (Cp*2Rh2-1) with two {Cp*Rh}2+ fragments capping the opposing faces of the Lindqvist anion. [ABSTRACT FROM AUTHOR]

Abstract: New complexes of triangular clusters M3S4 4+ (M=Mo, W) with incomplete cuboidal metal–chalcogenide framework bearing chiral α-hydroxy and amino acids have been prepared. l-lactic acid (H2lac), l-mandelic acid (H2man), and l-alanine (Hala) react with [W3S4Br4(PPh3)3] in 1:1 ratio to yield, respectively, monosubstituted complexes [W3S4(PPh3)3Br3(Hlac)(CH3CN)] (1), [W3S4(PPh3)3Br3(Hman)(CH3CN)] (2), and [W3S4(PPh3)3Br3(Hala)(CH3CN)]Br (3). In the presence of base [Mo3S4Cl4(PPh3)3] gives trisubstituted complexes [Mo3S4(PPh3)3(Hlac)2(lac)] (4) and [Mo3S4(PPh3)3(Hman)3]Cl (5). Circular dichroism studies of 4 indicate chirality transfer from the ligand to the Mo3S4 4+ cluster core. These complexes incorporate Cu+ with the formation of corresponding {M3CuS4}5+ cuboidal derivatives. NMR and ESI-MS studies of solution behavior are presented. [Copyright &y& Elsevier]

The [Mo3S4Cl3(dhprpe)3]+ (1+) cluster cation has been prepared by reaction between Mo3S4Cl4(PPh3)3 (solvent)2 and the water-soluble 1,2-bis(bis(hydroxypropyl)phosphino)ethane (dhprpe, L) ligand. The crystal structure of [1]2[MO6Cl14] has been determined by X-ray diffraction methods and shows the typical incomplete cuboidal structure with a capping and three bridging sulfides. The octahedral coordination around each metal center is completed with a chlorine and two phosphorus atoms of the diphosphine ligand. Depending on the pH, the hydroxo group of the functionalized diphosphine can substitute the chloride ligands and coordinate to the cluster core to give new clusters with tridentate deprotonated dhprpe ligands of formula [Mo3S4(dhprpe-H)3]+ (2+). A detailed study based on stopped-flow, 31P{1H} NMR, and electrospray ionization mass spectrometry techniques has been carried out to understand the behavior of acid-base equilibria and the kinetics of interconversion between the 1+ and the 2+ forms. Both conversion of 1+ to 2+ and its reverse process occur in a single kinetic step, so that reactions proceed at the three metal centers with statistically controlled kinetics. The values of the rate constants under different conditions are used to discuss on the mechanisms of opening and closing of the chelate rings with coordination or dissociation of chloride. [ABSTRACT FROM AUTHOR]

The crystal structures of compounds (III) and (IV) are determined by single crystal XRD. [ABSTRACT FROM AUTHOR]