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[Display omitted] • New cis -dioxo Mo(VI) complexes incorporating ONO donor Schiff base ligands derived from dihalosalicylaldehyde and nicotinic hydrazide were synthesized and characterized. • X-ray crystallographic study has confirmed the structures of the H 2 Cl 2 SN ligand and two Mo(VI) complexes (2 & 3). • All complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide. Three ONO donor Schiff base ligands were obtained by the condensation of 3,5-dihalosalicylaldehydes with nicotinoylhydrazide (H 2 Cl 2 SN: (E)-N'-(3,5-dichlorosalicylaldehyde) nicotinoylhydrazone, H 2 Br 2 SN: (E)-N'-(3,5-dibromosalicylaldehyde) nicotinoylhydrazone, and H 2 I 2 SN: (E)-N'-(3,5-diiodosalicylaldehyde) nicotinoylhydrazone on refluxing in ethanol. The treatment of [MoO 2 (acac) 2 ] (acac = acetylacetonato) with these ligands in methanol afforded cis -dioxidomolybdenum(VI) complexes [MoO 2 (Cl 2 SN)(CH 3 OH)] (1), [MoO 2 (Br 2 SN)(CH 3 OH)] (2), and [MoO 2 (I 2 SN)(CH 3 OH)] (3). Various techniques like NMR (1H and 13C), FT-IR, Mass, TGA, elemental (CHN), and single-crystal X-ray diffraction analysis (for H 2 Cl 2 SN · H 2 O , 2a , [MoO 2 (Br 2 SN)(C 2 H 5 OH)], and 3a , [MoO 2 (I 2 SN)(H 2 O)].DMF) were utilized to characterize the synthesized compounds. The data collected from diffraction studies revealed that the geometry around Mo(VI) ions was distorted octahedral. Additionally, all complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide. [ABSTRACT FROM AUTHOR]

Molybdenum carbonyl complexes with chalcone ligands incorporating pyridyl and anthryl units were synthesized via microwave activation. The incorporation of the chalcone moiety was found to improve the cytotoxicity and quadruplex DNA binding of these complexes. [Display omitted] • Molybdenum carbonyl complexes with chalcone ligands incorporating pyridyl and anthryl units were synthesized via microwave activation. • The structures of products with 2-pyridyl ligands were different from those with 3- or 4-pyridyl moieties. • The incorporation of the chalcone moiety was found to improve the cytotoxicity and quadruplex DNA binding of these complexes. Microwave irradiation of a mixture of Mo(CO) 6 and pyridinecarboxaldehyde (pyca), acetylpyridine (acpy) and pyridyl-anthryl chalcones with tetrahydrofuran solvent in a closed vessel afforded products in good yields without the need for an inert atmosphere. While the reaction with 3- and 4-pyridyl moieties gave the cis -disubstituted complexes Mo(CO) 4 (L) 2 , the reaction with 2-pyridyl entities yielded complexes with a range of structures such as Mo(CO) 2 (L) 2 , Mo(CO) 4 L and Mo 2 (CO) 6 (L) 2. All the novel complexes have been characterised by IR and 1H NMR spectroscopy as well as elemental analysis. In addition, the solid-state structure of one of the chalcone-ligated compounds has been determined by single-crystal X-ray diffraction. The chalcone-ligated complexes were found to be cytotoxic through the brine shrimp lethality assay, and were able to bind to quadruplex DNA. On the other hand, the pyca- and acpy-ligated compounds did not display any lethality and were unable to interact with DNA. The results indicate that the inclusion of a chalcone ligand plays an important role in improving the cytotoxicity and DNA binding capabilities of molybdenum carbonyl compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two homoleptic clusters [{M 6 I 8 }(DMSO) 6 ](I 3) 4 (M = Mo, W) were obtained. • Addition of iodine in reaction media facilitates the terminal ligand substitution. • Composition of the compounds was confirmed by a set of physicochemical analyses. • The clusters possess broad absorption up to ∼ 800 nm with E g of 1.5–1.6 eV. • The absence of cluster emission was explained by the presence of triiodide anions. The family of octahedral iodide cluster complexes of molybdenum and tungsten – [{M 6 I 8 }L 6 ] n – exhibit a unique set of properties with significant practical potential. Due to the strong influence of terminal ligands L on these properties, the search for new simpler, more convenient and cheaper approaches for their substitution is an urgent task. This work demonstrates a new one-step method for terminal ligand substitution using well-known and readily available complexes [{M 6 I 8 }I 6 ]2–. The synthetic technique involves the addition of molecular iodine to the reaction mixture in order to bind the released I– ions, thereby facilitating the reaction process. As a result, two new cluster complexes with dimethyl sulfoxide ligands [{M 6 I 8 }(DMSO) 6 ](I 3) 4 (M = Mo (1), W (2)) have been obtained and structurally characterized. The optical properties of the obtained compounds have been studied both in solid state and in solution, and E g values have been calculated from the solid-state absorption spectra. The presence of I 3 – anions has been shown to quench the emission of the cluster complexes, explaining the absence of luminescence in the obtained compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • A heterobimetallic [Mo0;CoIII] complex was synthesized and structurally characterized. • The corresponding monometallic [CoIII] counterpart was also obtained. • Both metals in [Mo0;CoIII] are electronically independent from each other, as shown by cyclic voltammetry. • [Mo0;CoIII] showed very low activity in CO 2 hydrogenation, but no conversion was observed for [CoIII]. A heterobimetallic [Mo0;CoIII] complex and the monometallic [CoIII] counterpart were synthesized and fully characterized. Both metals are electronically independent from each other, as shown by cyclic voltammetry. This is in agreement with previous results, obtained in a separate, previously published study, for the RhIII and IrIII analogues of the mono- and heterobimetallic complexes. The catalytic activity of [Mo0;CoIII] and [CoIII], which was analyzed in this work in homogeneous carbon dioxide hydrogenation to formate was studied. While [Mo0;CoIII] showed very low activity, no conversion was observed for [CoIII]. The low activity is most likely due to instability of the corresponding hydride complex, which could undergo reductive elimination liberating 2-phenylpyridine. [ABSTRACT FROM AUTHOR]

The geometries and energetics of Cp 2 FeMo(CO) n (n = 6, 5, 4, 3, 2; Cp = η5-C 5 H 5), including the experimentally known pentacarbonyl Cp 2 FeMo(CO) 5 , have been examined by density functional theory. The lowest energy Cp 2 FeMo(CO) 5 isomer is the experimentally known unbridged structure but an doubly bridged isomer lies within ∼2 kcal/mol of energy. The tricarbonyl Cp 2 FeMo(CO) 3 has an energetically favorable triply bridged structure with a formal Fe≡Mo triple bond analogous to the experimental valence isoelectronic Cp* 2 M 2 (µ-CO) 3 (M = Mn, Re; Cp* = η5-Me 5 C 5) structures. • The lowest energy Cp 2 FeMo(CO) 5 structure is the experimentally known unbridged structure. • A doubly bridged Cp 2 FeMo(CO) 3 (µ-CO) 2 is of comparable energy to its unbridged isomer. • The low-energy doubly bridged Cp 2 FeMo(CO) 2 (µ-CO) 2 structures are disfavored relative to disproportionation. • The highly favored lowest energy Cp 2 FeMo(CO) 3 structure is a triply bridged structure with an Fe≡Mo triple bond. • The lowest energy Cp 2 FeMo(µ-CO) 2 are doubly bridged singlet and triplet structures with Fe-Mo quadruple and triple bonds, respectively. The geometries and energetics of the heterometallic binuclear cyclopentadienyl iron-molybdenum carbonyls Cp 2 FeMo(CO) n (n = 6, 5, 4, 3, 2; Cp = η5-C 5 H 5), including the experimentally known pentacarbonyl Cp 2 FeMo(CO) 5 have been examined by density functional theory. The lowest energy structure for the pentacarbonyl Cp 2 FeMo(CO) 5 by the mPWPW19 method corresponds to the unbridged Cp 2 FeMo(CO) 5 isomer related to the experimental Cp 2 Mo 2 (CO) 6 structure with exclusively terminal carbonyl groups. However, the doubly bridged structure, which is related to the experimental trans - and cis -Cp 2 Fe 2 (CO) 2 (µ-CO) 2 structures of the homonuclear diiron derivative, lies only 1.4 kcal/mol in energy above the unbridged structure. The relative energies of the unbridged and doubly bridged Cp 2 FeMo(CO) 5 are reversed using the BP86 method with the doubly bridged structure lying 2.0 kcal/mol below the unbridged structure. The closeness in energy of these two structures suggests a fluxional system for Cp 2 FeMo(CO) 5. The low-energy structures for the tetracarbonyl Cp 2 FeMo(CO) 4 are doubly bridged structures with formal Fe=Mo double bonds in accord with the 18-electron rule. However, Cp 2 FeMo(CO) 4 is predicted not to be viable since its disproportionation into Cp 2 FeMo(CO) 5 + Cp 2 FeMo(CO) 3 is found to be highly exothermic. The tricarbonyl Cp 2 FeMo(CO) 3 has an energetically favorable triply bridged structure with a formal Fe≡Mo triple bond analogous to the experimental valence isoelectronic Cp* 2 M 2 (µ-CO) 3 (M = Mn, Re; Cp* = η5-Me 5 C 5) structures. The low-energy structures of the dicarbonyl Cp 2 FeMo(CO) 2 are doubly bridged structures which can be either singlets with an Fe Mo quadruple bond or triplets with an Fe≡Mo triple bond. The low-energy structures of the hexacarbonyl Cp 2 FeMo(CO) 6 can be interpreted as consisting of [CpFe(CO) 3 ]+ cations linked to [CpMo(CO) 3 ]− anions through one of the iron-bonded carbonyl groups with long ∼4 Å Fe⋯Mo distances indicating the absence of an iron-molybdenum bond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two new molybdenum complexes were prepared. • The Schiff base ligands and acetylacetonate underwent a Mannich nucleophilic addition reaction with the assistance of the Mo atom. • The complexes have been characterized by single crystal X-ray diffraction. • The complexes have effective antimicrobial activities. Reaction of bis(acetylacetonato)dioxomolybdenum(VI) with 4-fluoro-2-((pyridin-2-ylmethylene)amino)phenol and 3-methyl-2-((pyridin-2-ylmethylene)amino)phenol, respectively in methanol afforded two new molybdenum complexes [MoO 2 L1] and [MoO 2 L2], where L1 and L2 are the dianionic form of 3-(((5-fluoro-2-hydroxyphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H 2 L1) and 3-(((2-hydroxy-6-methylphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H 2 L2). Both complexes have been characterized by elemental analysis, IR, UV–Vis, 1H and 13C NMR spectra. Molecular structures of the complexes have been determined by X-ray crystallography. In the complexes, the ligands coordinated to the Mo atoms via pyridine nitrogen, amino nitrogen, phenolate oxygen, and enolate oxygen atoms. The octahedral coordination of the Mo atoms is furnished by two oxido oxygen atoms. The complexes were evaluated for their antibacterial activities on Bacillus subtilis , Staphylococcus aureus , Escherichia coli and Pseudomonas fluorescens , and antifungal activities on Candida albicans and Aspergillus niger , and gave interesting results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A chiral O 3 N-type l -alanine bisphenol ligand precursor (Et 3 NH)H 2 Lala was prepared. • (Et 3 NH)H 2 Lala forms molybdenum(VI) complexes [MoOCl(Lala)] and (Et 3 NH)[MoO 2 (Lala)]. • The ligand has a tetradentate coordination through three O donors and one N donor. • These complexes catalyze olefin epoxidation using H 2 O 2 and tBuOOH as oxidants. Dioxidomolybdenum(VI) compound [MoO 2 Cl 2 (dmso) 2 ] reacts with a chiral tetradentate O 3 N-type l -alanine bisphenol ligand precursor (Et 3 NH)H 2 Lala to form an oxidochloridomolybdenum(VI) complex [MoOCl(Lala)] (1) as two separable geometric isomers with phenolate groups in cis or trans positions. The single crystal X-ray and NMR analyses of cis - and trans - 1 reveal that the complexes are formed of monomeric molecules, in which the ligand has a tetradentate coordination through three oxygen donors and one nitrogen donor. The reaction of Na 2 MoO 4 ·2H 2 O with the same ligand precursor in an acidic methanol solution leads to the formation of an anionic dioxido complex (Et 3 NH)[MoO 2 (Lala)] (2) with a trans coordination of the tetradentate ligand. Trans - 1 and 2 were studied as active catalysts for olefin epoxidation: i.e. styrene, cyclohexene, S (–)-limonene and (–)-α-pinene using H 2 O 2 and tBuOOH as oxidants. [ABSTRACT FROM AUTHOR]

One pot-synthesis of the fourth category of dinuclear molybdenum(VI) oxalate series. • One - pot synthesis is a good strategy for obtaining oxalatomolybdate compounds ([Mo 2 O 6 (C 2 O 4) 2 ]4−). • The acidity of the medium favors the reduction of the anion [Mo 2 O 6 (C 2 O 4) 2 ]4−. • [Mo 2 O 6 (C 2 O 4) 2 ]4− is thermally stabilized if isolated with tertiary ammoniums as [HDabco]+. Three new dinuclear molybdenum(VI) oxalate (Pr 2 NH 2) 4 ·[Mo 2 O 6 (C 2 O 4) 2 ] (1), (iPr 2 NH 2) 4 ·[Mo 2 O 6 (C 2 O 4) 2 ] (2) and (HDabco) 4 [Mo 2 O 6 (C 2 O 4) 2 ]·2H 2 O (3) compounds, have been prepared by one pot-synthesis at room temperature and characterized by single crystal X-ray diffraction and vibrational spectroscopies. Each compound contains the binuclear [Mo 2 O 6 (C 2 O 4) 2 ]4− anion where each molybdenum is in an octahedral MoO 6 environment. In compound (3), the interconnection between [Mo 2 O 6 (C 2 O 4) 2 ]4− anions, [HDabco]+ cations and water molecules (H 2 O) leads to an infinite inorganic-organic chain structure. Similarly, in compounds (1) and (2) the interactions between [Mo 2 O 6 (C 2 O 4) 2 ]4− anions and respectively [Pr 2 NH 2 ]+ and [iPr 2 NH 2 ]+ cations leads to an infinite inorganic-organic chain structure. A remarkable difference between the compounds is that in compounds (1) and (2) interactions between the chains involve only Van der Waals forces giving rise to layer-like structures, which also interact between them only by Van der Waals forces, whereas in compound (3) the chains interact also through hydrogen bonds giving a 3D supramolecular structure. The thermal properties of the compounds were investigated through thermogravimetric and differential thermal analyzes. The differences in the thermal decomposition of the compounds in the solid state are discussed in relation with their crystal structure. Cyclic voltammetry shows that the [Mo 2 O 6 (C 2 O 4) 2 ]4− anion can be reduced in both aprotic solvent and water. [ABSTRACT FROM AUTHOR]

Graphical abstract A series of dimeric 2,2′-bipyridine or 1,10-phenanthroline oxomolybdenum(V) α-hydroxycarboxylates [(MoO) 2 OL 2 (bpy) 2 ]·xH 2 O and [(MoO) 2 OL 2 (phen) 2 ]·yH 2 O have been obtained and well-characterized in acidic media for comparisons. Highlights • A series of N -heterocycle oxomolybdenum(V) α-hydroxycarboxylates have been obtained. • No protonation was observed for α-alkoxy groups even under acidic condition. • Solid state 13C NMR spectra of 1 and 3 show large downfield shifts between the coordinated glycolate and malate. Abstract A series of dimeric oxomolybdenum(V) 2,2′-bipyridine or 1,10-phenanthroline α-hydroxycarboxylates trans -[(MoO) 2 O(glyc) 2 (bpy) 2 ]·3H 2 O (1), trans -[(MoO) 2 O(lact) 2 (bpy) 2 ]·3H 2 O (2), trans -[(MoO) 2 O(Hmal) 2 (bpy) 2 ] (3), trans -[(MoO) 2 O(lact) 2 (phen) 2 ]·4H 2 O (4) and trans -[(MoO) 2 O(Hmal) 2 (phen) 2 ]·4H 2 O (5) have been synthesized in acidic media for comparisons, where glycolate, lactate and malate in 1 – 5 chelate to molybdenum(V) with bidentate α-alkoxy and α-carboxy groups respectively. Unlike the molybdenum(IV) lactate in low valence [1] , no protonation was observed for α-alkoxy groups even under acidic condition. The two molybdenum atoms in 1 and 3 are paramagnetic independently as examples by EPR spectroscopies. Solid state 13C NMR spectra of 1 and 3 show large downfield shifts for the coordinated glycolate and malate (δ α-alkoxy 75.4, 82.8 ppm, Δδ 13.4 ppm). Moreover, a monomeric mixed ligand oxomolybdenum(VI) complex MoO 2 (glyc)(bpy) (6) was isolated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Binding of (E)-3-Phenyl-2-propenyl and (S / R)-1-Phenyl-2-propenyl carbonates on Mo(CO) 3 L. • The importance of hydrogen bonding in the stereoselectivity of the reaction is rationalized. • A scheme is being proposed that is in full compliance with previous mechanistic studies. Abstract The coordination and oxidative addition of (E)-3-phenyl-2-propenyl methyl carbonate (1) and (S / R)-1-phenyl-2-propenyl methyl carbonates (2) on Mo(CO) 3 L have been investigated computationally. In addition to the anticipated η 2 coordination mode of these allylic carbonates prior to their oxidative addition on molybdenum, hydrogen bonding between the leaving group of the substrates and the coordinated amide group of L as well as between the amide groups of L, plays an important role in the stereochemical control of this reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Oxidation of Mo(V) species in the presence of dimethylmalonate (dmm2−) produces a trinuclear [Mo 3 O 8 (dmm) 2 ]2−. Highlights • In presence of carboxylic acids, an inadvertent oxidation of Mo(V) took place. • Fully-oxidized, discrete oxomolybdates(VI) formed. • The used carboxylic acids were dimethylmalonic, mandelic and succinic acid. • Trinuclear [Mo 3 O 8 (dmm) 2 ]2−, tetranuclear [Mo 4 O 10 (OCH 3) 4 Cl 2 ]2− and octanuclear [Mo 8 O 26 Py 2 ]4− ions were obtained. Abstract Unplanned oxidation of molybdenum(V) in the presence of carboxylic acid afforded three fully-oxidized polynuclear oxomolybdates. In very similar reaction mixtures, the initial oxidation state of the metal ion was retained and species with the frequently-encountered dinuclear {MoV(O)(μ 2 -O) 2 MoV(O)}2+ core formed. The chosen carboxylic acid contained either two COOH groups or another functional group, i.e., OH moiety. The carboxylic acid was introduced with the idea that with both of its functional groups engaged in coordination discrete clusters composed of the {MoV(O)(μ 2 -O) 2 MoV(O)}2+ units and the organic linkers would form. Reaction systems with dimethylmalonic acid (dmmH 2) yielded two products, (Bu 4 N) 2 [Mo 3 O 8 (dmm) 2 ] (1) with a trinuclear anion and [{MoV 2 O 4 Py 2 (dmmMe)} 2 (OCH 3) 2 ] (2) (Py = pyridine, dmmMe− = monomethyl dimethylmalonate ester) as the non-oxidized counterpart. The dmm2− ion engaged in coordination to Mo(VI) centers both carboxylate groups, whereas the dmmMe− ion coordinated to Mo(V) centers via its carboxylate moiety in a bidentate bridging mode. Reactions with mandelic (H 2 man) acid resulted in {(C 6 H 5) 4 P} 2 [Mo 4 O 10 (OCH 3) 4 Cl 2 ] (3) with a tetranuclear core and in (PyH) 3 [MoV 2 O 4 Cl 4 (Hman)] (4). Only the non-oxidized compound 4 contains coordinated mandelate ion, whereas the role of the acid in the synthesis of 3 became that of a templating agent. (PyH) 4 [Mo 8 O 26 Py 2 ] (5) with an octanuclear anion is a fully-oxidized compound obtained from the reaction mixture with succinic acid. The compounds were characterized by X-ray structure analysis, bond valence sum (BVS) calculations, IR vibrational and 1H NMR spectroscopy. The TG and DSC experiments were performed on fully-oxidized compounds. Powder X-ray diffraction has confirmed molybdenum(VI) oxide as the end product of the thermal decomposition of (Bu 4 N) 2 [Mo 3 O 8 (dmm) 2 ] (1) and (PyH) 4 [Mo 8 O 26 Py 2 ] (5) in the air atmosphere. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Acenaphthenequinonediimine Mo(II) complexes were intercalated in Layered Double Hydroxides. • The complexes and materials were active in epoxidation of several olefins. • The materials competed effectively with the complexes in the epoxidation of most substrates. Abstract The two layered double hydroxides ZnAl-LDH and MgAl-LDH were functionalized with bis(4-HOOC-phenyl)-acenaphthenequinonediimine) (H 2 BIAN), leading to the intercalation of its dianion, which in a second step reacted with [Mo(CO) 3 X 2 (NCMe) 2 ] (X = I, Br), affording four new materials. These materials and the two complexes [Mo(CO) 3 X 2 (H 2 BIAN) 2 ] (X = I, Br) were tested in the olefin epoxidation reaction with substrates cis -cyclooctene, styrene, 1-octene, trans -hex-3-en-1-ol, and R- (+)-limonene, using tert -butylhydroperoxide (tbhp) as oxidant. The new catalysts were particularly good for cis -cyclooctene and styrene (100% conversions) and at least one heterogeneous catalyst was comparable to the homogeneous ones in the epoxidation of 1-octene and trans -hex-3-en-1-ol. The homogeneous catalysts were the best to oxidize R- (+)-limonene (higher conversions). [ABSTRACT FROM AUTHOR]

Graphical abstract Oxido-alcoholato- and oxido-thiolato-molybdenum(VI) complexes are prepared by oxygen atom transfer reaction to the molybdenum(IV) complexes. The reactivity of the thiolate complex is higher than that of the alcoholate complex. Abstract Oxido-alcoholato- and oxido-thiolato-molybdenum(VI) complexes bearing two ene-1,2-dithiolate ligands (cyclohexene-1,2-dithiolate) are prepared as synthetic models of molybdenum(VI) reaction centers of dimethyl sulfoxide reductase family of molybdenum enzymes. These complexes are prepared by oxygen atom transfer from tertiary amine N -oxide (trimethylamine N -oxide and N,N -dimethylaniline N -oxide) to the five-coordinate alcoholato- and thiolato-molybdenum(IV) complexes, and are characterized by UV–vis, cold-spray-ionization mass, resonance Raman, and 1H NMR spectroscopies. The oxygen atom transfer reactions are studied kinetically at a low temperature (−40 °C) to demonstrate that the reactivity of the thiolato-molybdenum(IV) complex is higher than that of alcoholato-molybdenum(IV) complex by about 7 times, and that the oxygen atom transfer reactivity increases with increasing the electron withdrawing ability of the p -substituent of N , N -dimethylaniline N -oxide derivatives. Mechanistic details are discussed based on the reactivity studies. [ABSTRACT FROM AUTHOR]

Graphical abstract The first case of degrading phosphorothioate pesticides of the form (EtO) 2 P(=S)Ar by a supported molybdenum complex reveals both oxon ((EtO) 2 P(=O)Ar) and diethyl phosphite formation. In terms of the diethyl phosphite product, this transformation converts a known neurotoxin into a commodity chemical. Specifically, the pesticide diazinon produces only diethyl phosphite by polystyrene-supported Mo(OO) n peroxide complex in EtOH with the addition of H 2 O 2 (aq). Highlights • A supported molybdate material degrades live phosphorothioate pesticides. • Diazinon degradation produces the commodity organophosphate diethyl phosphite. • A solution compound is presented that models the supported molybdate material. Abstract A polystyrene-supported molybdate-peroxide polymer (Mo-Y(s)) destroys phosphorothioate pesticides of the form (ArO)P(=S)(OEt) 2 in EtOH under mild oxidative (H 2 O 2) conditions and produces a commodity organophosphate. This is the first report of a metal-based system that successfully degrades the "live" pesticides parathion, diazinon and coumaphos. In addition to the operational advantages of heterogeneous reaction chemistry, the Mo-Y(s) support degrades multiple equivalents of the pesticide in H 2 O 2 (aq). Of particular importance is the predominant production of diethyl phosphite, a commodity chemical, from diazinon degradation over Mo-Y(s) in EtOH; no toxic oxon is found. Coumaphos and parathion produce the corresponding oxon which have ΔHǂ (kcal/mol) of 15.4 (0.5) and 21.7 (0.8), respectively; these activation parameters are consistent with key observations found in the relative amount of coumoxon and paraoxon produced. Finally, a discrete molybdate-peroxide complex is presented as a possible solution model for this heterogeneous reaction. [ABSTRACT FROM AUTHOR]

This work describes a procedure giving cyclopentadienyl molybdenum(II) compounds bearing carboxylic acid function group. It involves synthesis of carboxylic acid ester functionalized cyclopentadienides, their coordination to molybdenum(II) precursor and saponification of ester function groups. The method is not limited only to compounds with the function group directly attached in the cyclopentadienyl ring but also to those functionalized in the side chain. The attempts to synthesize the indenyl analogues were only partially successful due to low stability in the saponification step. All reported structure types were elucidated from spectroscopic measurements and verified by X-ray crystallography. The second part of the work describes an effect of the outer-coordination sphere on cytotoxicity of the cationic molybdenum(II) compounds bearing N,N -chelating ligands. The cytotoxicity of the modified species bearing phenanthroline ligand toward human leukemia cells MOLT-4 (IC 50  = 10.5 ± 0.5 μmol l −1 ) is higher than reported for cisplatin (IC 50  = 15.8 ± 1.9 μmol l −1 ). [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of biological properties a series of Mo2O2S2-thiosemicarbazone complexes. • A class of complexes better than Trolox for antixidant properties. • A strong structure–activity relationship. • Complexes with ligands displaying a phenol group kept free are very efficient for antitumoral activity. • Complexes with ligands displaying a pyridine group kept free are very efficient against bacteria and fungi. This paper deals with the biological properties of 14 coordination complexes assembled from a large panel of thiosemicarbazone ligands and [Mo 2 O 2 S 2 ]2+ cluster. The investigation of biological properties evidences a high cancer inhibition activity, and antimicrobial, antifungal and antioxidant properties. The complexes based on phenolic ligands are the most active towards tumor cells, while the pyridine derivatives are the most efficient against bacteria and fungi. [ABSTRACT FROM AUTHOR]

A series of dimeric N -hetercycle oxomolybdenum(V) complexes cis -Mo 2 O 4 (SO 4 )(phen) 2 ·2H 2 O ( 1 ), cis -Mo 2 O 4 (SO 4 )(bpy) 2 ·4H 2 O ( 2 ), cis -Mo 2 O 4 Cl 2 (bpy) 2 ( 3 ) and cis -Mo 2 O 4 (SO 4 )(im) 4 ( 4 ) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, im = imidazole) have been synthesized and characterized by the elemental analyses, IR, UV–vis, molecular fluorescence spectra, X-ray structural analyses and theoretical calculations. The two N -hetercycle ligands in 1 or 2 exhibit an approximate plane owing to SO 4 2− steric hindrance with strong interactions (2.215 av and 2.186 av  Å), which are new discrete dinuclear oxomolybdenum(V) complexes. 1 – 3 have been synthesized in acidic media under hydrothermal conditions and the transformations of oxomolybdenum(V) 2 – 3 and 1 to cis -Mo 2 O 4 Cl 2 (phen) 2 ( 5 ) are also outlined respectively. Moreover, the catalytic performances of 1 – 5 were tested by the degradation of methyl orange. The conjugated N -hetercycle ligands have obvious influences on their catalytic performances. [ABSTRACT FROM AUTHOR]

Tripodal, tetradentate tetraphosphine ligand tris(1 H -2-diisopropylphosphinoimidazol-1-yl)phosphine ( 1 ) was synthesized in three straightforward steps from widely available starting materials. The ligand crystallized in a C 3 -like conformation suitable for metal coordination. Nickel(II) complex 2 was prepared from 1 and Ni(dme)Br 2 and adopted a classical atrane structure with trigonal pyramidal geometry at the metal, a bromide covalently bonded in the axial position, and a bromide ion in the outer coordination sphere. Molybdenum(III) complex 3 was prepared from 1 and MoCl 3 (thf) 3 and could be structurally characterized using a co-crystal with Cp 2 Co and [Cp 2 Co]Cl. It displayed a face-capped octahedral geometry at the seven-coordinated metal. Complexes 2 and 3 proved prone to decomposition under reductive and oxidative conditions, hindering the investigation of their chemistry. Crystallization attempts from acetonitrile led to the isolation of dinuclear hydrolysis product 4 , with the Mo(III) centres bridged by two chlorides and two 2-(di iso propylphosphino)imidazole moieties in a paddlewheel arrangement. [ABSTRACT FROM AUTHOR]

We report a new method of crystal growth and synthesis based on liquid-liquid partitioning that allows for isolation and in-depth characterization of molybdenyl bis(formohydroxamate), Mo-FHA , molybdenyl bis(acetohydroxamate), Mo-AHA , and molybdenyl deferoxamine, Mo-DFO , for the first time. This novel approach affords shorter crystal growth time (hourly timeframe) without sacrificing crystal size or integrity when other methods of crystallization were unsuccessful. All three Mo complexes are characterized in solution via FTIR, NMR, UV–vis, and EXAFS spectroscopy. Mo-AHA and Mo-FHA structures are resolved by single crystal X-ray diffraction. Using the molybdenyl hydroxamate structural information, the speciation of Mo in a siderophore complex (Mo-DFO) is determined via complimentary spectroscopic methods and confirmed by DFT calculations. ESI-MS verifies that a complex of 1:1 molybdenum to deferoxamine is present in solution. Additionally, the Mo solution speciation in the precursor organic phase, MoO 2 (NO 3 ) 2 HEH[EHP] 2 (where HEH[EHP] is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), is characterized by FTIR and EXAFS spectroscopy as well as DFT calculations. [ABSTRACT FROM AUTHOR]

Phosphonium ylide complexes of Mo and W formulated as [M(η 3 -allyl){η 2 -(NPh) 2 CH}(CO) 2 (CH 2 PR 3 )] (M = Mo, R = Me: 2a-Mo ; M = Mo, R = Ph: 2b-Mo , and M = W, R = Me: 2a-W ) were prepared by the reaction of amidinato(pyridine) complex, [M(η 3 -allyl){η 2 -(NPh) 2 CH}(CO) 2 (NC 5 H 5 )] (M = Mo: 1-Mo and M = W: 1-W ), with a phosphonium ylide, CH 2 PR 3 (R = Me, Ph), which was generated in situ by the reaction of the corresponding phosphonium salt with n BuLi. These complexes were characterized spectroscopically, as well as by the X-ray diffraction. The phosphonium ylide ligand shows stronger electron donating ability toward the metal than N -heterocyclic carbene or phosphine ligands. This trend is supported by the comparison of the spectroscopic data and the DFT calculations. We also investigated the reactivity of the phosphonium ylide complexes 2-Mo with two-electron donors such as PEt 3 and NHC. In the case of the PPh 3 ylide complex ( 2b-Mo ), the substitution reaction of the ylide ligand for the two-electron donors took place cleanly to yield the corresponding complexes. On the other hand, in the PMe 3 ylide complex ( 2a-Mo ), the substituted complexes formed but the unreacted ylide complex 2a-Mo was also present in the reaction mixture. These results show that the bond strength of the M-C(phosphonium ylide) bond is affected by the substituents on the phosphorus atom. [ABSTRACT FROM AUTHOR]

An unsupported cobalt molybdenum sulfide catalyst was prepared using ammonium heptamolybdate, cobalt nitrate and elemental sulfur under reflux in ammonium hydroxide. The crystal structure of the precursor was identified using XRD and was determined to be a mix of CoMoO 4 and elemental sulfur. The refluxed samples were decomposed in a tube furnace at 450 °C under a constant flow of 10% H 2 :90% Ar gas mix. The freshly prepared catalyst was characterized using XRD and the LeBail fitting procedure, which confirmed the sample was a biphasic mixture of Co 9 S 8 MoS 2 . The synthesized sample was tested for the hydrodesulfurization of dibenzothiophene at 350 °C. The removal of the dibenzothiophene was found to follow pseudo zeroth order reaction with two catalytic rates of 1.63 × 10 −5 mol L −1 ·s −1 for the first 3.5 h and 6.81 × 10 −5 mol L −1 ·s −1 observed in the second 1.5 h (or catalytic activities of 24.5 and 9.27 mol g −1 s −1 ). After 5 h of reaction, the catalyst showed approximately 93% conversion of the dibenzothiophene. The primary product of the hydrodesulfurization of the dibenzothiophene was biphenyl, which was approximately 80% of the products, and the minor product was cyclohexylbenzene at approximately 13%. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoMoO 4 /Co 2 Mo 3 O 8 @C was synthesized by a carburization process of a Co-MOF combined with doping molybdenum. • CoMoO 4 /Co 2 Mo 3 O 8 @C exhibited an excellent catalytic activity for HER. • CoMoO 4 /Co 2 Mo 3 O 8 @C exhibited a smaller Tafel slope of 69 mV·dec−1 and a lower overpotential of 120 mV. • This work provides a new idea for designing efficient HER electrocatalysts. The synergistic effect of graphene and doping elements is vital to improve the electrocatalytic performance. However, it is still a challenge to select appropriate elements for doping to improve the rate of hydrogen evolution reaction (HER). In this study, we prepared a highly efficient and promising electrocatalyst, namely CoMoO 4 /Co 2 Mo 3 O 8 @C , by a carburization process of metal–organic frameworks (MOFs) combined with doping molybdenum via simple hydrothermal and pyrolysis method. Compared with Co-MOF , CoMoO 4 /Co 2 Mo 3 O 8 @C exhibited excellent electrocatalytic performance with an overpotential as low as 120 mV at 10 mA·cm−2 and a Tafel slope as small as 69 mV·dec−1 for HER activity in 0.5 M H 2 SO 4. The excellent performance of CoMoO 4 /Co 2 Mo 3 O 8 @C could be ascribed to the synergistic effect of CoMoO 4 /Co 2 Mo 3 O 8 and graphene coating, which facilitated charge transfer in HER activity. This work may provide novel perspectives for fabricating electrocatalysts composed of transition metal oxide and graphene based on MOFs for enhancing HER performance. [ABSTRACT FROM AUTHOR]

[MI 2 (CO) 3 (pz*H) 2 ] complexes (M = Mo, W; pz*H = pzH, dmpzH, indzH) have been synthesized and characterized in solid state and in solution. These heptacoordinated complexes present a capped octahedron geometry in the solid state where the azole ligands are always coordinated pseudo- cis , and the iodido ligands are coordinated either pseudo- trans (pzH complexes and molybdenum complex with indzH) or pseudo- cis (tungsten complex with dmpzH). Both isomers are found in the crystal structure of [WI 2 (CO) 3 (indzH) 2 ]. The difference in energies between both isomers have been theoretically calculated and range between −2.9 and +1.0 kcal/mol. The complexes where the iodido ligands are coordinated pseudo- trans show unequivalent azoles in the NMR at low temperature while they undergo a dynamic process in solution which makes both heterocycles equivalent at room temperature. The other complexes display a dynamic behavior in solution where both heterocycles are equivalent both at room and at low temperatures. [ABSTRACT FROM AUTHOR]

The Mo(II) complexes [MoX 2 (CO) 3 (BDC)] (X = I, Br; H 2 BDC = 2,2′-bipyridine-5,5′-dicarboxylic acid) were immobilized by intercalation in two layered double hydroxides (LDH), containing Zn/Al (synthesized) and Mg/Al (commercial), as shown by infrared and 13 C solid state NMR spectroscopies, and X-ray powder diffraction. Their catalytic activity was studied in olefin oxidation, using as oxidant tert -butylhydroperoxide (tbhp), and was compared with the activity of the related [MoX 2 (CO) 3 (bpy)] complexes (bpy = 2,2′-bipyridine). cis -Cyclooctene, styrene, 1-octene, trans -hex-3-en-1-ol, and R -(+)-limonene were the substrates tested. All the catalyst showed in average a high selectivity toward the epoxide of each substrate (above 90%, except for styrene), with variable conversions, but none of the heterogeneous catalysts proved to be more active than the homogeneous ones. The same or higher activity in a second catalytic run, as observed in most reactions, suggests a good recycling capability. [ABSTRACT FROM AUTHOR]

The global energy demand and the present high dependence on fossil fuels have caused an unprecedented increase in the Earth’s atmosphere carbon dioxide concentration. Its exponential and uncontrollable rise is responsible for large and unpredictable impacts on the world climate and for ocean acidification, thus, being a major concern for the ecosystems and human’s daily life. On the other hand, the carbon dioxide abundance and low cost make it an interesting source for the production of chemical feedstocks and fuels. Yet, the thermodynamic and kinetic stability of the carbon dioxide molecule makes its utilization a laboratorial/industrially challenging task. In this Review, we propose to use the molybdenum and tungsten-containing formate dehydrogenase (FDH) enzymes as a model to understand the mechanistic strategies and key chemical features needed to reduce carbon dioxide to formate. We will highlight the present knowledge about the structure of FDHs, with particular emphasis on active site features, reaction mechanism and ability to reduce carbon dioxide to formate. The information gathered aims to inspire the development of new efficient (bio)catalysts for the atmospheric carbon dioxide utilization, to produce energy and chemical feedstocks, while reducing an important environmental pollutant. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) properties of push–pull Mo complexes with ONO tridentate ligands have been studied. The compounds were obtained in high yields using multicomponent reactions and their structures were confirmed by NMR, IR and HRMS analysis. Furthermore, TGA studies revealed good thermal stability of the Mo complexes. The linear and NLO properties evidenced enhanced responses compared with their boron and tin analogs, indicating that Mo complexes should be further investigated as robust building blocks for NLO materials. [ABSTRACT FROM AUTHOR]

The octahedral molybdenum cluster compounds Na 2 [Mo 6 I 8 (N 3 ) 6 ] and Na 2 [Mo 6 I 8 (NCS) 6 ] were synthesized and their luminescent properties and biological activity were investigated. Most molybdenum cluster compounds reported so far have had low solubility in water and/or underwent hydrolysis connected with aggregation, sedimentation, and diminishing luminescence and singlet oxygen-sensitizing properties. This behavior prevented the investigation of their photophysical properties and in vitro biological activities in aqueous media. Title compounds behave differently. They are well soluble in water and have red luminescence, which is quenched by oxygen to produce singlet oxygen, O 2 ( 1 Δ g ), in high quantum yields. Even though [Mo 6 I 8 (N 3 ) 6 ] 2− and [Mo 6 I 8 (NCS) 6 ] 2− gradually hydrolyze to mono-hydroxy derivatives, they do not form sedimenting aggregates, luminescence properties are well-defined, and the quantum yields of O 2 ( 1 Δ g ) remain unchanged. These attractive features, suitable for luminescent probes or O 2 ( 1 Δ g ) sensitizers in living cells, are overshadowed by the toxicity, especially of [Mo 6 I 8 (NCS) 6 ] 2− , and by the limited uptake by the HeLa and HEK 293T cell lines. [ABSTRACT FROM AUTHOR]

Cothermolysis of [(Ph)P(Se)(μ-Se)] 2 or Woollins’ reagent (WR) with Cp 2 Mo 2 (CO) 4 ( 2 ) in toluene at 110 °C led to the isolation of three different metal clusters, [Cp 2 Mo 2 {(μ-Se) 2 (PPh(Se))}{(μ-Se)(PPh) 3 ] ( 3 ), Cp 4 Mo 4 (CO) 3 (μ-Se) 4 ( 4 ) and a pair of isomer complexes of Cp 3 Mo 3 (CO) 4 [Se 3 (PPh) 2 ] ( 5a and 5 b ) in 17.5%, 3.1% and 4.9% yields, respectively. A similar reaction at 70 °C gave only 5a and 5 b in 2.0% and 4.9% yields, respectively. All complexes have been fully characterized via NMR, IR and ESI mass spectroscopy. Molecular structures of 3 , 4 and 5a were confirmed by single crystal X-ray diffraction analyses. A variable temperature 1 H NMR study of 4 was carried out. Finally, a free-radical addition pathway by selenation of WR was postulated. [ABSTRACT FROM AUTHOR]

A series of molybdenum complexes based on chiral C 2 -symmetric picchxn-type ligands (N 4 ligands, defined as trans - N,N ′-bis(heterocycl-2-ylmethyl)-1,2-diaminocyclohexanes) has been synthesized and characterized. Reported and novel picchxn-type ligands form ( κ 3 -N 4 )Mo(CO) 3 , [( κ 4 -N 4 )Mo(NO)(CO)]PF 6 , and [( κ 4 -N 4 )Mo(NO)X]PF 6 (X = Br, I) compounds. Multiple tridentate ( κ 3 ) and tetradentate ( κ 4 ) ligand configurations were observed, and the favored κ 4 configuration was found to vary with N 4 heterocycle identity. Heterocycle variation allowed for directed modification of the molybdenum electronic characteristics, but none of the studied {( κ 4 -N 4 )Mo(NO)} + fragments was found to be a suitable π -base for dearomatization chemistry. The crystal structures of eight molybdenum complexes with picchxn-type ligands were determined. [ABSTRACT FROM AUTHOR]

Three new molybdenum complexes have been synthesized from one-pot reactions between Mo(CO) 3 (NCMe) 3 and pyridine-2-thiol (pySH) in the presence of different P-donors. Reaction with P(OMe) 3 in MeCN at ca. 55 °C gives Mo(CO) 2 [P(OMe) 3 ](κ 2 -pyS) 2 ( 1 ) and Mo(CO) 4 [P(OMe) 3 ] 2 ( 2 ). A similar reaction involving bis(diphenylphosphino)methane (dppm) furnishes the dinuclear species Mo 2 (CO) 4 (μ,κ 2 -pyS) 2 (κ 2 -dppm) ( 3 ) together with the mononuclear complexes Mo(CO)(κ 2 -pyS) 2 (κ 2 -dppm) ( 4 ) and Mo(CO) 4 (κ 2 -dppm) ( 5 ). With bis(diphenylphosphino)ethane (dppe) only the mononuclear complexes Mo(CO)(κ 2 -pyS) 2 (κ 2 -dppe) ( 6 ), Mo(CO) 4 (κ 2 -dppe) ( 7 ), and Mo(CO) 3 (κ 1 -dppe)(κ 2 -dppe) ( 8 ) resulted. Complexes 1 , 3 , and 6 have been characterized by single-crystal X-ray diffraction analyses and the bonding in 1 and 3 has been evaluated by density functional theory (DFT) calculations, optimized structures being discussed relative to the observed solid-state structures. [ABSTRACT FROM AUTHOR]

The application of Mo(II) complexes [Mo(η 3 -C 3 H 5 )(CO) 2 X(L 2 )] and [Mo(CO) 3 X 2 (L 2 )] to the oxidation of alkenes is described. We have synthesized, characterized and studied the catalytic activity of a series of complexes with nitrogen bidentate ligands (also a few monodentate and a few with N, O donors). They were modified with –Si(OR) 3 groups to immobilize in silicon based materials, MCM-41 and silica, using several procedures. Others were deprotonated to intercalate in clays. Many complexes catalyzed selectivity of cis- cyclooctene to its epoxide with high conversions, but oxidation of styrene led to more benzaldehyde than epoxide. Other substrates could be oxidized to several products with variable success. The materials containing immobilized complexes showed in some cases better conversions, in others worse, and others similar, for all substrates tested. Recycling experiments showed that the catalysts lose only a small amount of their activity in the second and third runs, while the selectivity (when determined) was kept. We discuss the mechanisms of the catalytic epoxidation of alkenes based on DFT studies. [ABSTRACT FROM AUTHOR]

Molybdenum complexes of type [MoO 2 L] n (L = tridentate ONO Schiff base ligands based on the salicylidene-2-aminophenolato structure) have been synthesized and used as catalysts for the solvent-free epoxidation of olefins. The effect of donor (diethylamino) and/or acceptor (nitro) substituents has been studied. [ABSTRACT FROM AUTHOR]

The title complex reacted with the aryl isocyanides CNXyl and CN( p -tol) rapidly at room temperature to yield the corresponding derivatives [Mo 2 Cp 2 ( μ -PR ∗ )(CO) 2 (CNR) 2 ] (Cp = η 5 -C 5 H 5 ; R = Xyl, p -tol; R ∗ = 2,4,6-C 6 H 2 t Bu 3 ) even when using 1 equiv of reagent. In contrast, reactions with 1 equiv of CN t Bu yielded the isocyanide-bridged derivatives cis - or trans -[Mo 2 Cp 2 ( μ -PR ∗ )( μ - η 1 : η 2 -CN t Bu)(CO) 2 ] depending on reaction conditions (Mo–Mo = 3.0818(3) and 3.1453(8) Å, respectively). The cis isomer was computed to be 16 kJ/mol more stable than the trans isomer, and could be also prepared by heating petroleum ether solutions of the latter at 333 K, while reaction of excess CN t Bu with the trans isomer yielded [Mo 2 Cp 2 ( μ -PR ∗ )(CO) 2 (CN t Bu) 2 ]. The title complex reacted with Me 2 PCH 2 PMe 2 (dmpm) to give the corresponding diphosphine-bridged derivative [Mo 2 Cp 2 ( μ -PR ∗ )(CO) 2 ( μ -dmpm)] or its chelate isomer [Mo 2 Cp 2 ( μ -PR ∗ )(CO) 2 ( κ 2 -dmpm)], depending on reaction conditions (Mo–Mo = 3.342(1) and 3.176(1) Å, respectively), whereas its room-temperature reaction with PH 2 Cy involved a H-shift to the phosphinidene ligand, to give the bis(phosphide) derivative [Mo 2 Cp 2 ( μ -PHCy)( μ -PHR ∗ )(CO) 2 ]. Photolysis of the latter induced decarbonylation, C–H bond cleavage, and dehydrogenation, to eventually yield the triply-bonded phosphaindanide derivative [Mo 2 Cp 2 { μ -P(CH 2 CMe 2 )C 6 H 2 t Bu 2 }( μ -PHCy)( μ -CO)] (Mo–Mo = 2.511(2) Å). Density functional theory analysis of the bonding in the title complex revealed a substantial mixing of one of the δ components of the intermetallic triple bond with the p π orbital of the phosphinidene ligand. As a result of this, the LUMO of the molecule is mainly centered at the P atom, but leads to little reactivity because of the steric protection provided by the ortho - t Bu groups of the phosphinidene substituent. The electron-acceptor reactivity of the molecule is then dominated by the close LUMO+1 orbital, which has Mo–Mo antibonding character and is well suited for interaction with donors approaching the dimetal site from the less congested side of the molecule, located between the carbonyl ligands. [ABSTRACT FROM AUTHOR]

Four dioxomolybdenum(VI) complexes were synthesized by reacting [MoO2(acac)2] with thiosemicarbazone ligands derived from 5-chloro-2-hydroxybenzaldehyde (H2L1), 2-hydroxy-5-methylbenzaldehyde (H2L2), 3-tert-butyl-2-hydroxybenzaldehyde (H2L3), or 2,3-dihydroxybenzaldehyde (H2L4). In all the complexes, the ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography showed that the distorted octahedral coordination of molybdenum atom is completed by methanol molecule (D) as in [MoO2(L1D)], [MoO2(L2D)], and [MoO2(L3D)], or by an ethanol molecule as in [MoO2(L4D)]. The molecular structures of H2L2, H2L3, and all synthesized complexes were determined via single crystal X-ray crystallography. The binding properties of the ligand and the complexes with calf thymus DNA were analyzed by UV, fluorescence titration, and viscosity measurements. Gel electrophoresis shows that all complexes can cleave the pBR322 plasmid DNA. The cytotoxic properties of the complexes were studied against human colorectal cell lines. All complexes showed strong antiproliferative activities in the relative order [MoO2(L3D)] > [MoO2(L1D)] ~ [MoO2(L2D)] > [MoO2(L4D)] with IC50 values of 3.2, 4.5, 4.6, and 6.4 µM, respectively. The complexes exhibited greater pronounced activity than the standard reference drug, 5-fluorouracil, did (IC50 = 7.3 µM). These studies demonstrate the potential application of dioxomolybdenum(VI) complexes in chemotherapy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Seven Mo(0) tetracarbonyl complexes of new phosphonite ligands have been synthesized and characterized by NMR spectroscopy. [•] X-ray crystal structures of four of the complexes have been determined. [•] The electron-donor abilities and steric effects of the phosphonite ligands can be independently adjusted. [ABSTRACT FROM AUTHOR]

Highlights: [•] Transformations among different types of citrato molybdates were studied in solid and solution. [•] Several experimental conditions emerged as the controlling factor of structural variation. [•] Each citrate acts as a tridentate ligand while a β-carboxy group is free. [Copyright &y& Elsevier]

Highlights: [•] Electroneutral phosphane synthesis. [•] Electrophilic phosphane synthesis. [•] Second order 19F NMR coupling. [•] Substitution chemistry with molybdenum hexacarbonyl. [Copyright &y& Elsevier]

Highlights: [•] We prepared novel molybdenum–tricarbonyl complexes bearing macrocyclic ligands. [•] Molecular structure of complex has intra- and intermolecular hydrogen bond. [•] We compare CO stretching vibration of several carbonyl complexes by FT-IR. [•] Hydrogen bond interaction controls the environment around metal center. [Copyright &y& Elsevier]

Abstract: Novel molybdenum and tungsten complexes with tridentate bis(phenolate) ligands containing [O,X,O] donor atoms (X=S or Se), [MoO2LS] (1), [MoO2LSe] (2), [WO2LS] (3) and [WO2LSe] (4), were synthesized and characterized as functional models for molybdenum- and tungsten-dependent oxidoreductases. The catalytic oxo-transfer properties of 1–4 were investigated by oxo-transfer reactions from nitrate to PPh3 with a ratio of complex (1–4):PPh3:(Bu4N)(NO3 −)=1:10:20 and from DMSO to PPh3 with varied catalyst:PPh3 ratios. For the oxygen atom transfer reaction from nitrate to PPh3, the molybdenum compounds are catalytically more active than their tungsten analogues. Whereas for the oxygen atom transfer reaction from DMSO to PPh3, the tungsten compounds exhibit more efficient catalytic behavior than the molybdenum analogues. In all catalytic reactions, sulfur containing compounds have a higher catalytic ability than their selenium analogues. In comparison, all four compounds catalyze the oxygen atom transfer reaction from DMSO to PPh3 much more effectively than the oxidation of PPh3 with NO3 −. [Copyright &y& Elsevier]

Abstract: The hydrothermal reactions of Cu(C2H3O2)2·H2O, MoO3, 2,2′:4′,4″:2″,2′″-quarterpyridyl-6′,6″-di-2-pyridine (bisterpy), and organodiphosphonate ligands of varying carbon chain length in the presence of HF yield a series of novel organic–inorganic hybrid materials of the oxomolybdenum–organophosphonate family. All compounds of the study were characterized by elemental analysis, IR spectroscopy, TGA, magnetic susceptibility and single crystal X-ray diffraction. A common feature within the architectures of both the three-dimensional structure of [{Cu2(bisterpy)(H2O)}Mo5O15{O3P(CH2)4PO3}]·4.5H2O (1) and the one-dimensional structure of [{Cu2(bisterpy)(H2O)2}Mo5O15{O3P(CH2)5PO3}] (2) is the presence of {Mo5O15(O3PR)2}4− clusters as building blocks. In the one-dimensional [{Cu2(bisterpy)(H2O)2}Mo2F6O4{HO3P(CH2)4PO3H}] (6), {Cu2(bisterpy)}Mo2F4O4{HO3P(CH2)5PO3H}2]·2H2O (7·2H2O), [{Cu2(bisterpy)(H2O)2}Mo4F8O8{O3P(CH2)6PO3}]·H2O (8·H2O) and [{Cu2(bisterpy)(H2O)2}Mo4F8O8{O3P(CH2)9PO3}] (9), the two-dimensional [{Cu2(bisterpy)(OH)}Mo2F3O4{O3P(CH2)PO3}]·11H2O (3·11H2O) and [{Cu2(bisterpy)(H2O)2}Mo4F4O10{O3P(CH2)2PO3}] (4), and the three-dimensional [{Cu2(bisterpy)}Mo4F6O9{O3P(CH2)3PO3}] (5), the pentamolybdate core has not been formed due to the incorporation of fluoride ions; rather a variety of {Mo x F y O z } units link the copper–bisterpy units. All structures contain the secondary metal–ligand {Cu2(bisterpy)(H2O) x } binuclear unit. The materials of this study demonstrate the wide structural variety available to this family of compounds by modifying both the carbon chain length of the organodiphosphonate ligand and by incorporation of fluoride within the structure. [Copyright &y& Elsevier]

Abstract: The molecular structures of the phosphinoarylthiolato molybdenum and iron complexes [Mo{(SC6H4-2-PPh2)-κ2 S,P}2(CO)2] (1) and [Fe{(SC6H4-2-PPh2)-κ2 S,P}2(CO)2] (2) are reported. They both have a central hexacoordinate metal(II) cation, but compound 1 has a trigonal-prismatic geometry with both CO and both thiolato groups in cis arrangement, while iron(II) complex 2 displays a pseudo-octahedral structure with both CO, both phosphino and both thiolato groups in trans arrangement. This is in a good agreement with DFT calculations, which showed that the different coordination geometry of molybdenum and iron in complexes 1 and 2 is a consequence of the number of d electrons (electronic factor) combined with the geometrical factors. [Copyright &y& Elsevier]

Abstract: Reaction of Mo(CO)6 with propionic acid and propionic anhydride gives the expected μ3-propylidyne capped molybdenum cluster as well as the unanticipated μ3-ethylidyne capped molybdenum cation with bridging propionates, [Mo3(μ3-CR)(μ3-O)(μ-O2CCH2CH3)6(H2O)3]Br·4H2O; R=CH3 and CH2CH3. Due to the similarity in structure, both complexes crystallize together in the triclinic crystal system upon slow evaporation of NaBr solutions (T =277K). Herein, we report the synthesis, characterization, and crystallographic study of the carbon-capped clusters. To our knowledge, this study is the first to report a trinuclear molybdenum cation in which the μ3-alkylidyne ligand is not the same chain length as the carboxylic acid used in the synthesis. [Copyright &y& Elsevier]

Abstract: The reaction of 2-pyridinecarboxaldehyde with K3Na[Mo(CN)4O2]·6H2O in water–ethanol solution at pH ca. 9 result in formation of an [{Mo(CN)3O}2(μ-pyr)]4− ion salt isolated as (PPh4)4[{Mo(CN)3O}2(μ-pyr-1κ2 N,O;2κ2 N,O)]·7H2O, where H2pyr=1,2-bis(2-pyridyl)ethene-1,2-diol. The X-ray crystal structure shows, that the pyr is in the form of endiol with Cd formal 2- charge. Cyclic voltammetry measurements indicate that binuclear complex can be reversibly oxidised to Mo(IV,V) with E 1/2 =+37mV and to Mo(V,V) at +262mV and reduced to Mo(III,III) at −468mV (scan speed 100mV/s). The formation of a Mo(IV,V) mixed valence complex is confirmed by the UV–Vis spectra in the presence of oxygen, [Copyright &y& Elsevier]

Abstract: The synthesis of two Mo(VI) tetradentate Schiff base complexes derived from 2,2′-dimethylpropylenediamine and aromatic aldehydes, (MoO2{hnaphnptn} (1) and MoO2{salnptn(3-OMe)2} (2)) is reported. Full characterization of these complexes was accomplished with elemental analyses, spectroscopic studies (1H NMR, IR, and UV–Vis) and X-ray structure analysis. X-ray crystallography studies reveal that these complexes adopt a distorted octahedral six-coordinate configuration formed by tetradentate Schiff base ligand and two binding oxygen atoms. Catalytic performance of the prepared molybdenum complexes for oxidation of different olefins with tert-butyl hydroperoxide was evaluated. These complexes were found to be an efficient and selective catalyst for the homogeneous oxidation of various olefins. MoO2{salnptn(3-OMe)2} with a methoxy groups on the salicylidene ring of the ligand promote the effectiveness of the catalyst. [Copyright &y& Elsevier]

Abstract: The dioxomolybdenum and dioxotungsten complexes [MoO2L1] (1-Mo) and [WO2L1] (2-W), supported by a diamine bis(phenolate) ligand (L1 =Me2NCH2CH2N(CH2-2-O-3,5-C6H2 tBu2)2) were prepared from MoO2Cl2 and WO2Cl2(dme) in good yields. The solid-state structures of both compounds obtained by single crystal X-ray diffraction reveal distorted octahedral geometries around the metals with cis terminal oxo ligands. Their performance in the catalytic epoxidation of cis-cyclooctene using H2O2 and TBHP as oxidants was evaluated. 2-W displays high activity with H2O2 as terminal oxidant, achieving 84% conversion in 6h (TOF=1400molsub molcat −1 h−1), while its molybdenum counterpart 1-Mo was inactive in the same conditions. Using TBHP as oxidant the opposite trend was observed and 1-Mo attained 93% conversion in 6h (TOF=1550molsub molcat −1 h−1). The Oxovanadium complexes [VOL1Cl] (3-V), [VOL2Cl] (4-V, L2 =Me2NCH2CH(CH3)N(CH2-2-O-3,5-C6H2 tBu2)2) and [(VOL1)2(μ-O)] (5-V) were also tested as catalysts in the epoxidation of cis-cyclooctene. The three compounds display high activity when the epoxidation reaction is performed using TBHP as oxidant. Using H2O2, 3-V and 4-V are moderately active while 5-V is inactive. [Copyright &y& Elsevier]

Abstract: The short chain alkoxycarbonyl complexes of molybdenum, [PPN][Mo(CO)5(COOR)], [R=CH3, CH2CH3 and CH(CH3)2], have been synthesized by the addition of [Mo(CO)6] to a refluxing solution of [PPN][OR] in different alcohol solvents under a CO atmosphere. In the absence of CO, metal alkoxide complexes [Mo(CO)5(OR)]− (R=CH2CH3 and CH(CH3)2) were formed. These new alkoxycarbonyl complexes were characterized by IR, 1H and 13C NMR spectroscopy, melting point and elemental analysis. When the CH3CN solution of the compounds [PPN][Mo(CO)5(COOCH(CH3)2)] and [PPN][Mo(CO)5(OCH(CH3)2)] were exposed to UV light the compounds decomposed to form the cluster compound [PPN]2[Mo6O19]. The tetraethylammonium derivative, [Et4N][Mo(CO)5(COOCH3)], prepared from [Et4N][OCH3] and Mo(CO)6 in methanolic solution also decomposed in CH3CN to form the new dark brown crystalline molybdenum oxo-cluster [Et4N]2[Mo4O13]. The compound crystallizes in the monoclinic form with a space group of P 21/n. Addition of [Ph4As][OCH(CH3)2] to Mo(CO)6 in a ratio of 4:1 results in the formation of the bis(alkoxycarbonyl) complex, [Ph4As]2[Mo(CO)4{(COOCH(CH3)2)2}]. The reaction of the methoxycarbonyl complex, [PPN][Mo(CO)5(COOCH3)] with synthesis gas in methanol at 125°C gave methyl formate, formic acid and Mo(CO)6. The same reaction as above in THF yielded methyl formate, methanol and formic acid. [Copyright &y& Elsevier]

Abstract: Treatment of with the trimetaphosphate salt (acetonitrile, gave the trimetaphosphate-molybdenum complex in 91% isolated yield. was also obtained in 77% isolated yield by directly treating with in refluxing acetonitrile, presumably by generating in situ. Reported herein is the full characterization and structural determination of and comparison to synthesized and calculated (M=group 6–9) complexes. [Copyright &y& Elsevier]

Abstract: A series of heterobimetallic polymeric complexes of manganese, cobalt, zinc, cadmium and nickel, [M(Mo2O5L2)(MeOH)2(H2O)2] n ·nH2O {M=Mn (2), n =1, Co (3), n =0, Zn (4), n =1 and Cd (5), n =1} and [Ni(Mo2O5L2)(MeOH)(H2O)3] n ·2H2O·MeOH (6) have been synthesized form the reaction of [{Na4(H2O)4(μ-H2O)2}⊂(Mo2O5L2)2] (1) {LH2 =2-(3,5-di-tert-butyl-2-hydroxybenzylamino)acetic acid} with the corresponding metal salts. The complexes have been structurally characterized. The Complexes, 3 and 6 undergo thermal decomposition to afford mixed oxides of the type, MMoO4·MoO3 {M=Co or Ni}. [Copyright &y& Elsevier]

Abstract: The reaction of anhydrous molybdenum-based heteropolyacids with diethylmethyl silane has been studied and the reaction products were characterized by various physicochemical methods such as infrared and Raman spectroscopies, XPS and solid-state NMR. The reaction leads to the evolution of hydrogen which reduces partly the polyacid, and to the formation of a [Et2MeSi] species interacting weakly with the polyoxometalate. Upon reaction with oxygen insertion of oxygen into the Si–C bonds is observed, even at low temperature. [Copyright &y& Elsevier]

Abstract: Reaction of solutions of [Mo2P2S3] (1; =η5-C5Me5) in CH2Cl2 with solutions of CuHal (Hal=Cl, Br, I) in CH3CN gave after slow diffusion the novel coordination polymers [Mo2P2S3(CuCl)4] (2), [Mo2P2S3(CuBr)3] (3) and [Mo2P2S3(CuI)3] (4). The products were characterized by elemental analysis, 31P magic angle spinning (MAS) NMR spectroscopy and single-crystal X-ray crystallography. The solid-state structures of 2 and 3 are composed of two-dimensional polymeric networks, whereas that of 4 contains parallel stacks of one-dimensional ribbons. In all cases the planar cyclo-P2S3 middle deck of the organometallic building block 1 provides one or two P atoms of the PS dumbbells along with the singly bridging sulfur atom as coordination sites for the various copper halide subunits. The assignment of P atoms follows from the correlation of 31P MAS NMR spectra with X-ray crystallographic data. In all compounds the distribution of main group atoms in the cyclo-P2S3 middle deck is different from that previously found in the starting material 1. [Copyright &y& Elsevier]