Synthesis and catalytic epoxidation activity with TBHP and H2O2 of dioxo-, oxoperoxo-, and oxodiperoxo molybdenum(VI) and tungsten(VI) compounds containing monodentate or bidentate phosphine oxide ligands: crystal structures of WCl2(O)2(OPMePh2)2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2.C4H10O, WCl2(O)2dppmO2, Mo(O)(O2)2dppmO2, and W(O)(O2)2dppmO2

The dioxo tungsten(VI) and molybdenum(VI) complexes WCl2(O)2(OPMePh2)2, WCl2(O)2dppmO2, and MoCl2(O)2dppmO2, the oxoperoxo compounds WCl2(O)(O2)(OPMePh2)2, WCl2(O)(O2)dppmO2, and MoCl2(O)(O2)dppmO2, and the oxodiperoxo complexes, W(O)(O2)2dppmO2 and Mo(O)(O2)2dppmO2 have been prepared and characterized by IR spectroscopy, 31P NMR spectroscopy, elemental analysis, and X-ray crystallography. The structural and X-ray crystallographic data of compounds WCl2(O)2(OPMePh2)2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2.4H10O, WCl2(O)2dppmO2, Mo(O)(O2)2dppmO2, and W(O)(O2)2dppmO2 are also detailed. All complexes were studied as catalysts for cis-cyclooctene epoxidation in the presence of tert-butyl hydroperoxide (TBHP) or H2O2 as an oxidant. The Mo-based catalysts showed a superior reactivity over W-based catalysts in the TBHP system. On the other hand, in the H2O2 system, the W-based catalysts (accomplishing nearly 100% epoxidation of cyclooctene in 6 h) are more reactive than the Mo catalysts (<45% under some conditions). Various solvent systems have been investigated, and ethanol is the most suitable solvent for the H2O2 system.     

Rational Synthesis of Molybdenum(V) Tetramers Consisting of [Mo2O4]2+ Dimers Held Together by Bridging Phosphinate Ligands and the Tungsten(VI) Dimer [(CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2]: Structural and Theoretical Considerations

Reacting MoO₂(acac)₂ with Ph₂POOH or Me₂POOH in EtOH results in the formation of the tetranuclear molybdenum (V) clusters Mo₄(μ ₃-O)₄(μ-O₂PR₂)₄O₄, PR₂ = PPh₂, 1, or PMe₂, 2, in functional yields (>90% and 55% respectively). The reaction of WO₂(acac)₂ with Ph₂POOH in MeOH affords the tungsten dimer [(CH₃O)₂(O)W(μ-O)(μ-O₂PPh₂)₂W(O)(CH₃O)₂], 3. The single crystal X-ray determined structures of complexes 1–3 are reported. In 1 and 2, the four Mo=O units are interconnected by four triply bridging oxygen atoms, resulting in a distorted cubic-like structure for the Mo₄(μ ₃-O)₄O₄ units. Each molybdenum atom forms two additional Mo–O bonds with two oxygen atoms from different adjacent phosphinato ligands. Complex 3, a tungsten dimer, contains packing disorder and consists of bridging oxo and diphenylphosphinato ligands. The bonding of 1 and 2 assessed by density-functional methods showed that bonding between the Mo(V) centers occurs through σ overlap of the d _xy orbitals. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Dedicated to the memory of Professor F. A. Cotton. Veritas numquam perit.     

Synthesis, Crystal Structure and Reactivity of Mo4O6(O2)2(μ3-O)2{(μ2-O,μ3-OC8H14}2(OPMePh2)2: A Self-assembled Tetranuclear Cluster Containing Two Peroxide and Two Trans-Cyclooctanediol Ligands*

The reaction of MoO₂Cl₂(OPMePh₂)₂ with t-butylhydroperoxide (TBHP) in the presence of cis-cyclooctene yields the tetrameric complex Mo₄O₆(O₂)₂(μ₃-O)₂{(μ₂-O,μ₃-OC₈H₁₄}₂(OPMePh₂)₂, (1). Additionally in the absence of cis-cyclooctene MoO(O₂)Cl₂(OPMePh₂)₂, MoO(O₂)₂(H₂O)(OPMePh₂), (2), and two novel yellow compounds can be isolated depending on the quantity of TBHP used and the reaction conditions. Both the starting material MoO₂Cl₂(OPMePh₂)₂ and tetramer 1 are capable of accomplishing the epoxidation of cis-cyclooctene as catalysts. The single crystal X-ray determined structures of complexes 1 and 2 are reported.Dedicated to Professor F. A. “Chief” Cotton on the occasion of his 75th birthday     

Functional Properties of Banana Starch (Musa spp.) and Its Utilization in Cosmetics

Unripe banana fruit of Musa acuminata (Musa AAA; Hom Khieo) and Musa sapientum L. (Musa ABB; Namwa) growing in Chiang Rai (Thailand) were used for extraction. The yield of the starches was 16.88% for Hom Khieo (HK) and 22.73% for Namwa (NW) based on unripe peeled banana fruit. The amylose contents of HK and NW were 24.99% and 26.23%, respectively. The morphology of starch granules was oval shape with elongated forms for large granules and round shape for small granules. The HK and NW showed B-type crystalline structure and the crystallinities were 23.54% and 26.83%, respectively. The peak temperature of gelatinization was around 77 °C and the enthalpy change (ΔH) was 3.05 and 7.76 J/g, respectively. The HK and NW banana starches showed 1.27 ± 0.12 g/g and 1.53 ± 0.12 g/g water absorption capacity, and 1.22 ± 0.11 g/g and 1.16 ± 0.12 g/g oil absorption capacity, respectively. The swelling power of the banana starches was 17.23 ± 0.94 g/g and 15.90 ± 0.15 g/g, respectively, and the percentage of solubility in water showed 26.43 ± 2.50 g/g and 20.54 ± 0.94 g/g, respectively. The banana starches showed very poor flow character. The HK and NW starches have the potential to be used in powder base preparations with no effect on the sensory texture of the product at 15% w/w maximum.     

Reexamination of the structure of MoO(O2)2(H2O)(hmpa), hmpa=hexamethylphosphoramide by crystallographic and theoretical means

The crystal structure of MoO(O₂)₂(H₂O)(hmpa), hmpa=hexamethylphosphoramide, has been reassessed and corrected as one of the axial parameters (namely the c-axis) was reported incorrectly. This resulted in significant differences in the internal geometry of the molecule, notably an decreased O–O atom distance (≈0.03 Å) in the metal-bonded peroxo ligands. Crystal packing forces and a flat bending potential of the Mo–O–P angle accounts for discrepancies between theory and experimental structures.