Synthesis, crystal structure and reactivity of Mo \u3c inf\u3e 4 O \u3c inf\u3e 6 (O \u3c inf\u3e 2 ) \u3c inf\u3e 2 (μ \u3c inf\u3e 3 -O) \u3c inf\u3e 2 {(μ \u3c inf\u3e 2 -O,μ \u3c inf\u3e 3 -OC \u3c inf\u3e 8 H \u3c inf\u3e 14 } \u3c inf\u3e 2 (OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 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(OPMePh 2)2, (1). Additionally in the absence of cis-cyclooctene MoO(O2)Cl2(OPMePh2)2, MoO(O 2)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 MoO2Cl 2(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. © 2005 Springer Science+Business Media, Inc

Synthesis and catalytic epoxidation activity with TBHP and H \u3c inf\u3e 2 O \u3c inf\u3e 2 of dioxo-, oxoperoxo-, and oxodiperoxo molybdenum(VI) and tungsten(VI) compounds containing monodentate or bidentate phosphine oxide ligands: Crystal structures of WCl \u3c inf\u3e 2 (O) \u3c inf\u3e 2 (OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2 , WCl \u3c inf\u3e 2 (O)(O \u3c inf\u3e 2 )(OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2 , MoCl \u3c inf\u3e 2

The dioxo tungsten(VI) and molybdenum(VI) complexes WCl2(O) 2(OPMePh2)2, WCl2(O) 2dppmO2, and MoCl2(O)2-dppmO 2, the oxoperoxo compounds WCl2(O)(O2) (OPMePh2)2, WCl2(O)(O2)dppmO 2, 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·C4H 10O, WCl2(O)2dppmO2, Mo(O)(O 2)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 ( \u3c 45% under some conditions). Various solvent systems have been investigated, and ethanol is the most suitable solvent for the H2O2 system. © 2006 American Chemical Society

Crystal structures of MoCl \u3c inf\u3e 2 (O)(O \u3c inf\u3e 2 )(OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2 and mixtures of MoCl \u3c inf\u3e 2 (O \u3c inf\u3e 2 ) (OPPh \u3c inf\u3e 3 ) \u3c inf\u3e 2 and MoCl \u3c inf\u3e 2 (O)(O \u3c inf\u3e 2 )(OPPh \u3c inf\u3e 3 ) \u3c inf\u3e 2 : Allylic alcohol isomerization studies using MoCl \u3c inf\u3e 2 (O)(O \u3c inf\u3e 2 )(OPMePh \u3c inf\u3e 2 ) \u3c inf\u3e 2

Adding one equivalent of H2O2 to compounds of stoichiometry MoCl2(O)2(OPR3)2, OPR3 = OPMePh2 or OPPh3, leads to the formation of oxo-peroxo compounds MoCl2(O)(O2)(OPR 3)2. The compound MoCl2(O)(O 2)(OPMePh2)2 crystallized with an unequal disorder, 63%:37%, between the oxo and peroxo ligands, as verified by single-crystal X-ray diffractometry, and can be isolated in reasonable yields. MoCl2(O)(O2)(OPPh3)2, was not isolated in pure form, co-crystallized with MoCl2(O) 2(OPPh3)2 in two ratios, 18%:82% and 12%:88%, respectively, and did not contain any disorder in the arrangement of the oxo and peroxo groups. These complexes accomplish the isomerization of various allylic alcohols. A mechanism of this reaction has been constructed based on 18O isotopic studies and involves exchange between the alcohol and metal bonded O atoms. © 2004 Elsevier B.V. All rights reserved

Allylic alcohol isomerization and mechanistic considerations with CH \u3c inf\u3e 3 ReO \u3c inf\u3e 3

A mechanism for the isomerization of allylic alcohols by CH 3ReO 3 has been constructed on the basis of 18O isotopic studies and involves exchange between the alcohol and metal-bonded O atoms, in contrast to a previously published mechanism, which involved the 1,3-transposition of the O atom on the alcohol. Our method of analysis does not directly rule out this latter mechanism

Rational synthesis of molybdenum(V) tetramers consisting of [Mo \u3c inf\u3e 2 O \u3c inf\u3e 4 ] \u3c sup\u3e 2+ \u3c/sup\u3e dimers held together by bridging phosphinate ligands and the tungsten(VI) dimer [(CH \u3c inf\u3e 3 O) \u3c inf\u3e 2 (O)W(μ-O)(μ-O \u3c inf\u3e 2 PPh \u3c inf\u3e 2 ) \u3c inf\u3e 2 W(O) (CH \u3c inf\u3e 3 O) \u3c inf\u3e 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 = PPh 2, 1, or PMe2, 2, in functional yields (\u3e 90% and 55% respectively). The reaction of WO2(acac)2 with Ph 2POOH 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. © 2007 Springer Science+Business Media, LLC

Reexamination of the structure of MoO(O \u3c inf\u3e 2 ) \u3c inf\u3e 2 (H \u3c inf\u3e 2 O)(hmpa), hmpa=hexamethylphosphoramide by crystallographic and theoretical means

The crystal structure of MoO(O2)2(H 2O)(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. © 2005 Elsevier B.V. All rights reserved