Genta Sakane

Uptake of ethylene by sulfur-bridged cubane-type molybdenum/tungsten-nickel clusters [M3NiS4(H2O)10]4+ M3=Mo3, Mo2W, MoW2, W3): syntheses, structures and 1H NMR spectra

Abstract The reaction of the incomplete cubane-type molybdenum/tungsten clusters [M3S4(H2O)9]4+ M3=Mo2W, MoW2, W3 with nickel metal gave the corresponding single cubane-type molybdenum/tungsten-nickel clusters [M3NiS4(H2O)10]4+, respectively. X-ray analyses of the clusters revealed that when pts− was used as the counter anion (Hpts, p-toluenesulfonic acid), the cluster [Mo2WNiS4(H2O)10]4+ (Mo2WNi) crystallized out as the single cubane-type [Mo2WNiS4(H2O)10](pts)4 · 7H2O (Mo2WNipts), and the clusters [MoW2NiS4(H2O)10]4+-(MoW2Ni) and [W3NiS4(H2O)10]4+ (W3Ni) crystallized out as the double cubane-type [{MoW2NiS4(H2O)9}2](pts)8 · 20H2O (MoW2Nipts) and [{W3NiS4(H2O)9}2](pts)8 · 20H2O (W3Nipts), respectively. The crystallographic results obtained are as follows: Mo2WNipts: triclinic, P 1 , a = 17.836(7), b = 19.599(10), c = 8.924(5) A , α = 102.77(5), β = 103.49(4), γ = 63.67(3)° , V = 2694(2) A 3 , Z = 2, R = 5.0%, MoW2Nipts: tricilinic, P 1 , a = 15.413(3), b = 16.743(3), c = 12.073(4) A , α = 96.123(12) , β = 108.39(2), γ = 102.25(2)°, V = 2838(1) A 3 , Z = 1, R = 8.8% ; W3Nipts: tricilinic, P 1 , a = 15.468(5), b = 16.869(5), c = 12.007(3) A , α = 95.61(3), β = 108.71(2), γ = 102.24(3)°, V = 2853(2) A 3 , Z = 1, R = 9.0% . The molybdenum/tungsten-nickel cubane-type clusters [Mo3NiS4(H2O)10]4+ (Mo3Ni), Mo2WNi, MoW2Ni and W3Ni take up ethylene in aqueous or organic solutions to give olefin π-complexes [Mo3NiS4(C2H4)(H2O)9]4+ (Mo3NiEt), [Mo2WNiS4(C2H4)(H2O)9]4+ (Mo2NiEt), [MoW2NiS4(C2H4)(H2O)9]4+ (MoW2NiEt) and [W3NiS4(C2H4)(H2O)9]4+ (W3NiEt), respectively. The reactivity of Mo3Ni with ethylene is not so high as the tungsten containing clusters, Mo2WNi, MoW2Ni and W3Ni, and the reaction does not complete in aqueous solution. However, in organic solutions such as CH2Cl2, the reaction was completed. The following crystals were obtained and X-ray structures were determined: [ Mo 2 WNiS 4 ( C 2 H 4 )( H 2 O ) 9 ]( pts ) 1 2 ·6 HO (Mo2WNiEtpts), [ MoW 2 NiS 4 ( C 2 H 4 )( H 2 O ) 9 ]( pts ) 4 ( Hpts ) 1 2 ·6 H 2 O (MoW2NiEtpts) and [ W 3 NiS 4 ( C 2 H 4 )( H 2 O ) 9 ]( pts ) 4 ( Hpts ) 1 2 · 6 H 2 O (W3NiEtpts). The crystallographic results obtained are as follows: Mo2WNiEtpts: trigonal, P 3 1 c , a = 16.186(6) , c = 27.898(7) A , V = 6330(3) A 3 , Z = 4, R = 6.7% , MoW2NiEtpts; trigonal, P 3 1 c , a = 16.19(2), c = 27.776(4) A , V = 6306(8) A 3 , Z = 4, R = 7.2% ; W3NiEtpts: trigonal, P 3 1 c , a = 16.247(9), c = 27.785(7) A , V = 6352(4) A 3 , Z = 4, R = 7.2% . The X-ray structure analyses revealed that the three clusters are isomorphous with each other and that ethylene coordinates to the nickel site in each cluster. The ethylene molecule on the three-fold axis is disordered, and molybdenum and tungsten atoms in Mo2WNiEt and MoW2NiEt are statistically disordered. 1H NMR spectra of Mo3NiEt, Mo2WNiEt, MoW2NiEt and W3NiEt were obtained. An increase in the number of tungsten atoms in the clusters resulted in an increase in the upfield chemical shift of the 1H NMR signal due to the coordinated ethylene: this tendency can be explained by the fact that tungsten withdraws less electrons than molybdenum, which causes the higher electron density of the hydrogen atoms of ethylene in tungsten-containing clusters. While the nickel complexes so far reported which are reactive toward ethylene contain zero-valent nickel, the formal oxidation state of the nickel atoms in the clusters Mo3Ni, Mo2WNi, MoW2Ni and W3Ni is two, which is evident from the XPS data of Ni 2 p 3 2 Ni metal, 852.7; Mo3Ni, 854.7; Mo2WNi, 854.6; W3Ni, 854.5 eV.

Oxo- and sulfido-bridged sandwich cubane-type molybdenum-indium mixed-metal cluster. Synthesis and X-ray structure of [(H2O)9Mo3S3OInOS3Mo3-(H2O)9](CH3·C6H4·SO3)8·3OH2O

Abstract The aqua cluster [Mo3(μ3-S)(μ-O)(μ-S)2(H2O)9]4+ (B) reacts with indium metal in aqueous solution of Hpts to give a novel sandwich cubane-type molybdenum-indium mixed- metal cluster [(H2O)9Mo3S3OInOS3Mo3(H2O)9]8+ (C). The cluster C is oxidized in hydrochloric acid to give the starting species B, evolution of hydrogen gas being detected. An intermediate is isolated, and is tentatively assigned to Mo3In(μ3-S)(μ-O)(μ-S)25+(aq) (D). The following reaction pathways are proposed: 2B+In→C; C+H+→D+B+ 1 2 H2; D+2H+→B+In3++H2.

Convenient route to niobium in lower oxidation states: synthesis and crystal structure of K4[Nb(C2O4)4] · 4H2O · 1/2H2C2O4

Abstract A convenient preparative route to an Nb(IV) complex, K 4 [Nb(C 2 O 4 ) 4 ] · 4H 2 O · 1/2H 2 C 2 O 4 , is obtained by zinc reduction of concentrated hydrochloric acid-ethanol solutions of niobium pentachloride followed by in situ complexation with oxalate. This direct method of synthesis of an Nb(IV) complex may serve to open up a new avenue to the aqueous solution chemistry of niobium in lower oxidation states. The structure of the complex, as determined by X-ray crystallography, is a square-antiprism tetrakis-chelate arrangement of the oxalate ligand coordinated to an Nb(IV) center. The brown complex crystallizes in the triclinic space group P 1 , with Z = 2, a = 11.219(4), b = 12.931(5), c = 9.257(4) A , α = 110.79(3), β = 114.15(2), γ = 88.56(3)°, V = 1134.4(9) A 3 , M r = 718.46, D calc = 2.10 g cm −3 , R = 0.029 and R w = 0.0049.

Universal spectrochemical series of six-coordinate octahedral metal complexes for modifying the ligand field splitting.

We studied a novel universal spectrochemical series of six-coordinated octahedral 3d transition metal complexes, which can be used for any combination of central metal atom and ligand molecules. A two dimensional spectrochemical series could be used to estimate the ligand field splitting energy of not only known compounds but also the unknown compounds. Therefore, it should be possible to control the physical properties, such as the electronic and magnetic properties and the optical phenomena of octahedral transition metal complexes by modifying the ligand field splitting.

Cubane-Type Molybdenum-Zinc or -Cadmium Mixed-Metal Clusters with Diethyldithiophosphate or Nitrilotriacetate Ligands

The reactions of sulfur-bridged clusters, [Mo3(μ3-S)(μ-S)3(μ-dtp)(dtp)3(CH3CN)] (1) in acetonitrile or [Mo3(μ3-S)(μ-S)3(Hnta)3]2− (2) in pure water, with zinc or cadmium metal result in the formation of three novel molybdenum-zinc or molybdenum-cadmium mixed-metal clusters, [Zn{(μ3-S)4Mo3(μ-dtp)(dtp)3(CH3CN)}2] (3), [Cd{(μ3-S)4Mo3(μ-dtp)(dtp)3(CH3CN)}2] (4), and [Cd{(μ3-S)4Mo3(Hnta)3}2]4− (5), respectively. The X-ray crystal structures of 1·H2O(1′), 3, 4, and [Co(H2O)6]25·22H2O (5′) were determined, and the existence of the sandwich cubane-type cores Mo3S4MS4Mo8+3 cores (M=Zn, Cd) in 3, 4, and 5′ verified. By the change of the ligands, the peak positions at the longest wavelength in the electronic spectra are distinctly different from each other between 4 (856 nm) and 6 (1235 nm). The electronic structures of 3, 4, and 5 have been calculated by Discrete Variational (DV)-Xα method.

Synthesis, Structure, and 31P NMR of Sulfur/Oxygen-Bridged Incomplete Cubane-Type Molybdenum and Tungsten Clusters with Triphenylphosphine Ligands

Sulfur/oxygen-bridged incomplete cubane-type triphenylphosphine molybdenum and tungsten-clusters [Mo3S4Cl4(H2O)2(PPh3)3]·3THF (1A), [Mo3S4Cl4(H2O)2(PPh3)3]·2THF (2A), [Mo3OS3Cl4(H2O)2(PPh3)3]·2THF (1B), and [W3S4Cl4(H2O)2(PPh3)3]·2THF (1C) were prepared from the corresponding aqua clusters and PPh3 in THF/MeOH. On recrystallization from THF, procedures with and without addition of hexane to the solution gave 1A and 2A, respectively, while the procedures gave no effect on the formation of 1B and 1C. Crystallographic results obtained are as follows: 1A: monoclinic, P21/n, a=17.141(4) Å, b=22.579(5) Å, c=19.069(4) Å, β=96.18(2)°, V=7337(3) Å3, Z=4, R(Rw)=0.078(0.102); 1C: monoclinic, P21/c, a=12.635(1) Å, b=20.216(4) Å, c=27.815(3) Å, β=96.16(1)°, V=7062(2) Å3, Z=4, R(Rw)=0.071(0.083). If the phenyl groups are ignored, the molecule [Mo3S4Cl4(H2O)2(PPh3)3] in 2A has idealized CS symmetry with the mirror plane perpendicular to the plane determined by the metal atoms, while the molecule in 1A does not have the symmetry. The tungsten compound 1C is isomorphous with the molybdenum compound 2A. 31P NMR spectra of 1A, 2A, and 1C were obtained and compared with similar clusters with dmpe (1,2-bis(dimethylphosphino)ethane) ligands.

Solid state synthesis and crystal structure of a novel cluster, [WS4Ag3I(AsPh3)3](SAsPh3)

SummaryThe cluster [WS4Ag3I(AsPh3)3](SAsPh3) was prepared by the solid state reaction of (NH4)2WS4, AgI and AsPh3 at low heat. Some AsIII atoms were oxidized to Asv in the process. The structure of [WS4Ag3I(AsPh3)3](SAsPh3) was determined by single crystal X-ray diffractometry and can be described as the combination of cubane-like [WS4Ag3I(AsPh3)3] with an SAsPh3 moiety.

A dodeca nuclear cyclic molybdenum cluster, Preparation and X-ray structure of [{(Mo3(μ3-O)(μ-O)3(H2O)9)- (μ-OH)2}4] (CH3C6H4SO3)8·41H2O

Abstract The X-ray crystal structure analysis of a compound obtained from an incomplete cubane-type molybdenum cluster [Mo3(μ3-O-(μ-O)3 (H2O)9]4+ revealed a cyclic structure consiting of four incomplete cubane-type molybdenum (IV) aqua clusters, 3(H2O)5) (μ-OH)2}4] (pts)8·41H2O. The compound crystallized in the triclinic space group P 1 α = 14.068(4), b = 20.844(5), c = 14.026(3) A , α = 92.70(2), β = 117.85(2), γ = 98.87(2)°, V = 3559.6(16) A , Z = 1, R = 1.044. The cluster cation has a center of symmetry, and eight OH ligands bridge the four incomplete cubane-type Mo3O4 cores. Four types of MoO distance exist: (i) MoO (/ within Mo3O4 cores, 1.914[5] A, (ii) MoO (μ3-O within Mo3O4 cores, 2.024[4] A), (iii) MoO (OH bridge between Mo3 O4 cores, 2.094[11] A), (iv) MoO (ligating water molecules, 2.154[7] A). The six independent Mo-Mo distances are classified into two groups; four shorter ones range between 2.483 and 2.499 A (mean 2.489[4] A) and two longer ones range between 2.514 and 2.517 A (mean 2.516[2] A). Elongation of the MoMo distance is due to the larger trans influence of the bridging OH as compared with that of water ligand.

New Sesquiterpene Lactone Dimer, Uvedafolin, Extracted from Eight Yacon Leaf Varieties (Smallanthus sonchifolius): Cytotoxicity in HeLa, HL-60, and Murine B16-F10 Melanoma Cell Lines.

Uvedafolin, 1, a new sesquiterpene lactone dimer, was isolated from the leaves of Smallanthus sonchifolius with five related compounds, 2-6, and their cytotoxicity was assessed against three tumor cell lines (HeLa, HL-60, B16-F10 melanoma). The stereostructure of 1 was newly elucidated by ESI-TOF-MS, 1D/2D NMR, and single-crystal X-ray diffraction. Dimers 1 and 2 had the most effective IC50 values, 0.2-1.9 μM, against the three tumor cell lines when compared with monomers 3-6 (IC50 values 0.7-9.9 μM) and etoposide (IC50 values 0.8-114 μM). The ester linkages of two sets of monomers, uvedalin, 5, and sonchifolin, 6, for 1, and enhydrin, 4, and sonchifolin, 6, for 2, as well as the acetyl group at the C-9 position, were essential for the high cytotoxicity. Dimers 1 and 2 would have potential as anticancer agents.

Discrete Variational (DV)-Xα Calculations of Incomplete Cubane-Type Molybdenum Clusters [Mo3X4(H2O)9]4+ (X= O,S)1

Electronic structures of two incomplete cubane-type clusters [Mo3X4(H2O)9]4+ (X =O, S) have been calculated by the discrete-variational (DV)-Xα method. The calculations explain the experimental results of valence-band X-ray photoelectron spectra, electronic spectra, and reactivity difference toward acetylene. The net charge of Mo in [Mo3S4(H2O)9]4+(S) is more negative than that of Mo in [MO3O4H2O)4+] (O), and the bridging sulfur atoms are the main negative charge-source for the molybdenum atoms in the cluster S. As for S,levels of HOMO (45e) and LUMO (46e) consist mainly of Mo 4d andμ-S 3p atomic orbitals, and contribution ofμ3-S 3p to the orbitals is not large. The existence of Mo-Mo, Mo-μ-S, and Mo-μ3-S bounds is clear from the contour maps of the orbitals. As for O levels of HOMO (40e) and LUMO (41c) consist mainly of Mo 4d andμ-O 2p atomic orbitals. Contribution ofμ3-O 2p to the orbitals is not large except in the orbital 30a1,. The existence of Mo-Mo, Mo-μ-O, and MO-μ3-O bonds also is appreciable from the contour maps of the orbitals.