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The title compound, [Mo(C5H7O2)2O2] or cis-[MoO2(acac)2] (acac is acetylacetonate), contains a molybdenum(VI) atom coordinated by two acetylacetonate ligands and two doubly bonded oxido ligands in a distorted octahedral shape. The molecule is chiral and the asymmetric unit contains two independent molecules (one Δ, one Λ). Extensive C—H...O contacts are present throughout the structure. Data were collected at 100 K, providing higher precision of unit-cell parameters and atomic positions than previous determinations [Kamenar et al. (1973). Cryst. Struct. Commun. 2, 41–44.; Krasochka et al. (1975). Zh. Strukt. Khim. 16, 696–698].

Synthetic complexes containing a cis-[MoO2]2+ core are well-established models for the molybdenum co-factor (Moco). Here we report the crystal structure of such a model complex bearing a tetradentate amine bis(phenolate) ligand with fluorine substituents on the phenolate rings, namely, [2,2′-({[2-(dimethylamino)ethyl]azanediyl}bis(methylene))bis(4,6-difluorophenolato)]dioxidomolybdenum(VI)), [Mo(C18H18F4N2O2)O2]. Distortion from idealized octahedral symmetry about the Mo center is evident in the large O=Mo=O angle [108.54 (4)°] and the small N–Mo–Ophenolate angles [79.79 (4), 81.21 (3), 77.83 (3), and 84.59 (3)°]. The dihedral angle between the phenolate rings is 60.06 (4)°, and π–π stacking is observed between aromatic rings related by inversion (1 − x, 1 − y, 1 − z). The lower data-collection temperature of 150 K vs room-temperature data collection reported previously [KOWXIF; Cao et al. (2014). Transit. Met. Chem. 39, 933–937] and larger 2θ range for data collection (5.8–66.6° versus 6–54.96°) led to a structure with lower R1 and ωR2 values (0.019 and 0.049 vs 0.0310 and 0.0566 for KOWXIF). Comparison of the metrical parameters with KOWXIF suggests that this dataset offers a more realistic depiction of bonding within the MoVI=O moiety.

In this research, the density functional theory (DFT) calculations were carried out for investigation non-bonded interaction between the anticancer drug Fludarabine (Fludara) with sugar molecule (2S,3R,4S,5S)-2-(hydroxymethyl)-3,5-dimethyloxolane-3,4-diol (OXO) by using B3LYP/6-311+G* level of theory in the solvent water. The electronic spectra of the Fludara drug and Fludara/OXO complex in solvent water were calculated by time dependent density functional theory (TD-DFT) for the study of intermolecular interaction effect. The non-bonded interaction effects of the Fludara drug with OXO on the electronic properties, natural charges and chemical shift tensors have been also detected. The results display the change in title parameters after interaction process. According to the natural bond orbital (NBO) results, the Fludara molecule and OXO play as both electron donor and acceptor at the Fludara/OXO complex. On the other hand, the charge transfer is occurred between the bonding, antibonding or nonbonding orbitals in two molecules drug and OXO. [ABSTRACT FROM AUTHOR]

Dimeric [CrL]2, where L is the conjugate base of bis‐pyrazolyl pyridine, is evaluated for its ability to undergo inner sphere and outer sphere redox chemistry. It reacts with Cp2Fe+ to give [Cr4(HL)4(μ4‐O)]2+, still containing divalent Cr. Reduction (KC8) of [CrL]2 by two electrons gives [K2(THF)3Cr3L3(μ3‐O)], and by four electrons gives [K4(THF)10Cr2L2(μ‐O)], each of which has scavenged (hydr)oxide from glass surface because of the electrophilicity of the underligated Cr. [K4(THF)10Cr2L2(μ‐O)], is shown by comprehensive DFT calculations and analysis of intra‐ligand bond lengths to contain a pyridyl radical L3− and CrII, illustrating that this pincer is proton‐responsive, redox active, and a versatile donor to associated K+ ions here. The K+ electrophiles interact with electron‐rich oxo, but do not significantly (>5 kcal mol−1) alter spin state energies. Inner sphere oxidation of [CrL]2 with a quinone gives [Cr2L2(semiquinone)2], while pre‐reduced [CrL]22− reacts with quinone to give [K3(THF)3Cr2L2(catecholate)2(μ‐OH)], a product of capture of two undercoordinated LCr(catecholate)1− by hydroxide. [ABSTRACT FROM AUTHOR]

A cluster-ligand is disclosed in the form of [Ru 3 (CN) 3 (CO) 9 ] 3- ([ 1 ] 3- ). Produced by simple reaction of [Ru 3 (CO) 12 ] with cyanide, [ 1 ] 3- serves as a precursor to a series of μ-CN cages. When treated with [Ru 3 (CO) 12 ], it readily forms the prism [Ru 6 (μ-CN) 3 (CO) 18 ] 3- . With 1.5 equiv of [Cu(MeCN) 4 ] + [ 1 ] 3- reacts to give the expanded prism {Cu 3 [Ru 3 (μ-CN) 3 (CO) 9 ] 2 } 3- , which features three two-coordinate Cu(I) centers. Sources of Ni 2+ and Fe 2+ bind two equivalents of [ 1 ] 3- , giving the double cages {M[Ru 3 (μ-CN) 3 (CO) 9 ] 2 } 4- (M = Ni, Fe) wherein the central metal is octahedral. The 1:1 reaction using [Fe(H 2 O) 6 ] 2+ gave the interpenetrated super-tetrahedrane {Fe 4 (μ 4 -O)[Ru 3 (μ-CN) 3 (CO) 9 ] 4 } 4- ., Competing Interests: Conflicts of interest There are no conflicts to declare.

This review focuses on the design, synthesis, and reactivity of low-coordinate base transition metal complexes supported by bulky alkoxide ligands. The unique electronic features of alkoxide ligands result in strongly electrophilic character at the metal centers, which enhances reactivity of metal-bound substrates and facilitates their transformation. However, insufficiently bulky alkoxide ligands tend to form oligomeric and polymeric aggregates, thus circumventing well-defined reactivity at isolated metal centers. This review examines first the requirements for the attainment of mononuclear complexes in alkoxide ligand environments. Coordination chemistry of the most prominent alkoxide ligands [OCR3] is discussed, with particular emphasis on the impact of the R group on the nuclearity of the resulting complex and the number of alkoxide ligands bound to it. Next, the behavior of such complexes in group transfer chemistry and ensuing reactivity is examined. While several previously synthesized alkoxide ligands are discussed, the major focus of this review is on the recent chemistry of the “asymmetric” alkoxide ligands [OCtBu2Me] and [OCtBu2Ph] with the middle and late 3d metals. [ABSTRACT FROM PUBLISHER]

Quantum chemical calculations using the B3LYP/6-311++G(d,p) method were performed to determine the affinity of the [Ca(H 2 O) 5 ] 2+ cation for several monofunctional ligands. Four sets of ligands were studied: with oxygen binding atom (phosphoryl, amide, carboxylic acid, ketone, aldehyde, ether, alcohol, enol), nitrogen (imine, thiocyanic acid, nitrile, amine and ammonia), sulfur (thiocarbonyl, thioether and thioalcohol) and phosphorous (phosphine) binding atom. Compounds that bind via a double bonded oxygen atom have the strongest metal–ligand interaction, followed by compounds binding via nitrogen, singly bonded oxygen atom, sulfur and phosphine. The ligand with the strongest interaction, phosphine oxide, has an ionic resonance form with a negative charge on the binding oxygen atom that highly contributes to the hybrid geometry, what favors the interaction. The Energy Decomposition Analysis (EDA) of the interaction energy between the [Ca(H 2 O) 5 ] 2+ cation and the ligand shows that the electrostatic term is the major component of the interaction and represents at least 43.66% of the total interaction energy. The covalent component represents at least 28.09% of the total interaction energy. Along the set of compounds studied, the electrostatic component varies more than twice the covalent term. The repulsive and the dispersion components are roughly constant in all complexes. [ABSTRACT FROM AUTHOR]

A tetranuclear CeIV oxo cluster compound containing the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]− (LOEt−) has been synthesized and its reactions with H2O2, CO2, NO, and Brønsted acids have been studied. The treatment of [Ce(LOEt)(NO3)3] with Et4NOH in acetonitrile afforded the tetranuclear CeIV oxo cluster [Ce4(LOEt)4O7H2] ( 1) containing an adamantane-like {Ce4(μ2-O)6} core with a μ4-oxo ligand at the center. The reaction of 1 with H2O2 resulted in the formation of the peroxo cluster [Ce4(LOEt)4(μ4-O)(μ2-O2)4(μ2-OH)2] ( 2). The treatment of 1 with CO2 and NO led to isolation of [Ce(LOEt)2(CO3)] and [Ce(LOEt)(NO3)3], respectively. The protonation of 1 with HCl, ROH (R=2,4,6-trichlorophenyl), and Ph3SiOH yielded [Ce(LOEt)Cl3] ( 3), [Ce(LOEt)(OR)3] ( 4), and [Ce(LOEt)(OSiPh3)3] ( 5), respectively. The chloride ligands in 3 are labile and can be abstracted by silver(I) salts. The treatment of 3 with AgOTs (OTs−=tosylate) and Ag2O afforded [Ce(LOEt)(OTs)3] ( 6) and 1, respectively. The electrochemistry of the Ce-LOEt complexes has been studied by using cyclic voltammetry. The crystal structures of complexes 1- 5 have been determined. [ABSTRACT FROM AUTHOR]

A tetranuclear CeIV oxo cluster compound containing the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]− (LOEt−) has been synthesized and its reactions with H2O2, CO2, NO, and Brønsted acids have been studied. The treatment of [Ce(LOEt)(NO3)3] with Et4NOH in acetonitrile afforded the tetranuclear CeIV oxo cluster [Ce4(LOEt)4O7H2] ( 1) containing an adamantane-like {Ce4(μ2-O)6} core with a μ4-oxo ligand at the center. The reaction of 1 with H2O2 resulted in the formation of the peroxo cluster [Ce4(LOEt)4(μ4-O)(μ2-O2)4(μ2-OH)2] ( 2). The treatment of 1 with CO2 and NO led to isolation of [Ce(LOEt)2(CO3)] and [Ce(LOEt)(NO3)3], respectively. The protonation of 1 with HCl, ROH (R=2,4,6-trichlorophenyl), and Ph3SiOH yielded [Ce(LOEt)Cl3] ( 3), [Ce(LOEt)(OR)3] ( 4), and [Ce(LOEt)(OSiPh3)3] ( 5), respectively. The chloride ligands in 3 are labile and can be abstracted by silver(I) salts. The treatment of 3 with AgOTs (OTs−=tosylate) and Ag2O afforded [Ce(LOEt)(OTs)3] ( 6) and 1, respectively. The electrochemistry of the Ce-LOEt complexes has been studied by using cyclic voltammetry. The crystal structures of complexes 1- 5 have been determined. [ABSTRACT FROM AUTHOR]

Heterometallic yellow compound Ba3[Fe(C2O4)3]2(H2O)12 (1) with mononuclear anion [Fe(C2O4)3³-] can be transformed to heterometallic red compound Ba4.5[Fe4O(OH)3(C2O4)8](H2O)19 (2) with OH/O bridged tetranuclear anion [Fe4O(OH)3(C2O4)89-] in the mother liquor. Ba2+ and Fe3+ form three-dimensional networks thorough oxalate anion and H2O molecules in 1 and 2. 1 is a paramagnet and a strong antiferromagnetic interaction as the ground state S = 0 exists in 2. [ABSTRACT FROM AUTHOR]

The reaction between cis-[RevO2I(PPh3)2] and H3duo (N-(2-hydroxybenzylidene)-5-amino-1,3-dimethyl uracil) led to the formation of the oxofree, imido compound, trans-[Rev(ddd)(Hduo)(PPh3)2]I (1) (H2ddd=5,6-diamino-1,3-dimethyluracil). An oxo V complex, cis-[Rev (bcp)OCl2(PPh3)](2) [Hbcp = N-(2-hydroxybenzylidene)-benzothiazole] was isolated from the reaction of trans-[ReO vCl3(PPh3)2] with Hbcp. The crystal structures of the compounds were determined by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of uranium tetrachloride, UCl4, with sodium N,N-dimethylaminodiboranate, Na(H3BNMe2BH3), in refluxing 1,2-dimethoxyethane (dme) yields small amounts of a new complex, which we formulate as (μ-oxo)hexakis(tetrahydroborato)bis(1,2-dimethoxyethane)diuranium(IV), toluene solvate, U2(μ-O)(BH4)6(dme)2·C7H8, 1. Most likely, the formation of BH4 − groups from H3BNMe2BH3 − occurs with the elimination of [Me2NBH2]2, and the formation of the oxo group involves adventitious hydrolysis. Each uranium center in 1 adopts a fac octahedral geometry (counting the BH4 − groups as occupying one coordination site); the bridging oxygen atom and the two coordinated oxygen atoms of the dme ligand occupy positions trans to the three BH4 − groups. The hydrogen atom positions were located in the electron density difference maps and reveal that all three BH4 − groups are bound in a κ3 H fashion. The U⋯B distances to the two BH4 − groups that are cis to the bridging oxygen atom are 2.574(6) and 2.584(6)Å, whereas the U⋯B distance of 2.635(7)Å to the BH4 − group that is trans to the bridging oxygen is distinctly longer. Thus, the bridging oxygen atom exerts a noticeable trans influence. The crystallographic and 1H NMR data strongly suggest that the previously reported uranium hydride complex U2(μ-H)2(BH4)6(dme)2 should be reformulated as this oxo complex U2(μ-O)(BH4)6(dme)2. [Copyright &y& Elsevier]

Abstract: Heating [WO2(S2CNBui 2)2] with a slight excess of ArNCO (Ar=Ph, p-tolyl) results in the rapid formation of imido-ureato complexes [W(NAr){κ2-ArNC(O)NAr}(S2CNBui 2)2], a transformation believed to occur via the bis(imido) intermediates [W(NAr)2(S2CNBui 2)2]. The ureato ligand is easily removed (as the urea) upon addition of gaseous HCl to afford the dichloride [W(NAr)Cl2(S2CNBui 2)2]. While bis(imido) complexes are unavailable from the direct reaction of isocyanates (or amines) with [WO2(S2CNBui 2)2], they can be prepared upon addition of dithiocarbamate salts to [W(NBut)2(NHBut)2] addition of two equivalents of [NH2Bui 2][Bui 2NCS2] affording [W(NBut)2(S2CNBui 2)2] in which both imido groups are linear. [Copyright &y& Elsevier]

Abstract: Pyrolysis of an in-situ generated intermediate, produced in the reaction of [Cp∗MoCl4], 1, (Cp∗ =η5-C5Me5) with [LiBH4·THF], with an excess of difuryl ditelluride in toluene at 90°C yielded syn and anti isomers of [Cp∗Mo(O)(μ-Te)]2 (2, 3) and [Cp∗ 2Mo2O2(μ-O)(μ-Te)] (4, 5). In a similar fashion, dibenzyl diselenide yielded syn and anti isomers of [Cp∗Mo(O)(μ-Se)]2 (6, 7), along with the known nido-[(Cp∗Mo)2B4H8Se2]. Note that in parallel with 2–7, [(Cp∗Mo)2B5H9] was isolated as the major product in both cases. Compounds 2–7 have been isolated in modest yield as orange to brown crystalline solids. All the new compounds have been characterized in solution by mass, IR, 1H, 13C, 77Se and 125Te NMR spectroscopy, and the structural types were unequivocally established by crystallographic analysis of 2–4 and 7. [Copyright &y& Elsevier]

Terminal oxo and sulfido complexes in the form of (nacnac) V=E(Ntol2) (nacnac = [ArNC(CH3)]2CH−, Ar=2,6-(CHMe2)2C6H3, Ntol2 = −N(C6H4-4-Me), E = O (1), S (2)) were isolated from treatment of the masked three-coordinate vanadium(II) complex, (nacnac)V(Ntol2), with C5H5NO and S8, respectively. Both vanadium(IV) species, 1 and 2, have been characterized by room temperature X-band EPR spectroscopic studies, and in the case of complex 1, a single crystal molecular structure confirmed the presence of a terminal oxo moiety. Moreover, reaction of (nacnac)V(Ntol2) with diphenyl–disulfide and diphenyl–diselenide results in the reductive cleavage of these compounds to produce the vanadium(III) complexes (nacnac)V(XPh)(Ntol2) (X = S, (3), Se (4)). A molecular structure of the phenylsulfide complex, 3, confirmed formation of the d2 complex resulting from reductive cleavage of the S–S bond. [Copyright &y& Elsevier]

Abstract: Coordination complexes containing extended metal–oxygen frameworks have been studied for a number of applications, including catalysis and as optical materials; however, very few neutral complexes that contain extended metal–oxygen frameworks have been characterized. The new hexanuclear, mixed-valence MoV/MoVI coordination complex Mo6O13(Hsal)2(sal)2(acac)2 has been synthesized by direct reaction of salicylic acid (2-HOC6H4CO2H; H2sal) with Mo(O)2(acac)2. The mixed-valence compound is composed of two edge-sharing Mo4(μ-O)4 rings, in which four Mo atoms are MoVI and two are MoV. The tetranuclear complex Mo4O10(acac)4 was obtained from residual washings of the same reaction and is composed of a single Mo4(μ-O)4 ring having only MoVI atoms. XPS studies confirmed that the hexanuclear complex contains both MoV and MoVI. Magnetic measurements reveal that the hexanuclear complex is diamagnetic suggesting an electron–electron coupling between the two MoV centers through an oxo-bridge. [Copyright &y& Elsevier]

Abstract: New and improved procedures are reported for the synthesis of [M(DBCOT)(μ-Cl)]2 (M=Rh, Ir; DBCOT=dibenzo[a,e]cyclooctatetraene) from MCl3(H2O) x or [M(COD)(μ-Cl)]2 and DBCOT. Treatment of [M(DBCOT)(μ-Cl)]2 with [(LAu)3(μ-O)]BF4(L=PPh3, P t Bu3) yields the mixed-metal oxo complexes [M(DBCOT)(μ4-O)(AuL)2]2(BF4)2. Dimeric [Rh(DBCOT)(μ-OH)]2 is obtained from the reaction of [M(DBCOT)(μ-Cl)]2 with KOH in EtOH/H2O. All complexes except [Rh(DBCOT)(μ-Cl)]2 have been structurally characterized by single crystal X-ray diffraction. [Copyright &y& Elsevier]

Five complexes [WO(NCS)4L-L] (where L-L = benzoic acid[1-(Furan-2-yl)methylene]hydrazide(BFMH), benzoic acid[(thiophen-2-yl)methylene]hydrazide(BTMH), benzoic acid[1-(thiophen-2-yl)ethylidene]hydrazide(BTEH), benzoic acid(phenylmethylene)hydrazide(BPMH) and benzoic acid[1-(anisol-3-yl) methylene]hydrazide(BAMH)) have been prepared by reaction of ammonium tetraisothiocyanatodioxotungstate(VI) with the corresponding ligand in aqueous medium in the presence of hydrochloric acid. The complexes have been characterized by elemental analysis, molar conductivity, magnetic moment measurements, IR, electronic spectra, thermogravimetric analysis TGA/DTA and 1H NMR. [ABSTRACT FROM AUTHOR]

Abstract: This review summarizes the kinetics and mechanisms of the oxidation of various inorganic and organic substrates by trans-dioxoruthenium(VI) complexes containing macrocyclic tertiary amine ligands during the period 1993–2006. [Copyright &y& Elsevier]

Abstract: The antimony aryloxide compound may be readily obtained via the reaction of Sb(OEt)3 with tris(3,5-di-t-butyl-2-hydroxybenzyl)amine, . forms the adduct upon treatment with Me2SO, and comparison of the molecular structure of with that of [κ4-N(o-C6H4O)3]Sb(OSMe2) demonstrates that the Sb–OSMe2 bond length in the former complex is significantly longer than that in the latter. This observation indicates that the ligand engenders a less Lewis acidic antimony center than does . exhibits diverse reactivity. For example, treatment of with AcOH cleaves one of the Sb–O bonds to give , Br2 undergoes oxidative addition to give , while Me3NO·2H2O yields the oxo and hydroxo complexes , , and . [Copyright &y& Elsevier]

Abstract: The synthesis of an unusual cyclometallated amido lithium-tetra-zinc complex, (μ4-oxo)-pentakis(μ2-diethylamido)-bis(N(ethyl)CHCH2)-lithium-tetrazinc, was achieved in reasonable yield by the reaction of zinc chloride and lithium diethylamide. The new complex was characterised and an X-ray crystal structure was reported. [Copyright &y& Elsevier]

Abstract: The results of density functional theory (DFT) calculations are analyzed to investigate the thermodynamic and kinetic feasibility of nickel-mediated group transfer (E=CH2, NH, PH) to ethylene to form three-membered ring products. From the results of DFT geometry optimizations it is concluded that the (dhpe)Nir is unstable, dhpe=1,2-bis-(dihydrophosphino)ethane, rearranging to a phosphine oxide. With respect to the calculated enthalpies of the individual reaction steps, as well as their enthalpic barriers, the (dhpe)Ni system is a potent system for heterogroup transfer to olefins to synthesize cyclic organics, i.e., aziridines, cyclopropanes and phosphiranes. The individual mechanistic steps and overall reaction are calculated to be highly exothermic for all transfer groups investigated: nitrene, carbene and phosphinidene. Furthermore, the calculated [2π +2π] transition states entail the dissociation of one of the Ni–P bonds of dhpe; when the [2+2] products are subsequently formed, dhpe reverts to η2 coordination. The calculated results suggest that reductive elimination from the four-membered metallaheterobutane intermediate is the rate-determining step of the group transfer mechanism for all E. The greater kinetic barrier for E–C reductive elimination relative to [2π +2π] addition correlates with the greater thermodynamic driving force for the latter. [Copyright &y& Elsevier]

Abstract: Reactions of Zr(O i Pr)4(Pr i OH) with di- and trichloroacetic acid in 1:1 molar ratio in toluene gave the products Zr2(μ-O i Pr)2(μ-OOCCHCl2)(O i Pr)4(OOCCHCl2)(HO i Pr) (1) and Zr2(μ-O i Pr)2(μOOCCCl3)(O i Pr)4(OOCCCl3)(HO i Pr) (2), respectively, in quantitative yields. The molecular geometry of both (1) and (2) is constituted by a slightly distorted edge-shared bioctahedron and both have almost similar bond dimensions. Addition of dichloroacetic acid in 1:2 molar ratio to Zr(O i Pr)4(HO i Pr) in toluene although yielded the bis-substituted crude product Zr(O i Pr)2(OOCCHCl2)2(HO i Pr) (3) but its solution in toluene left for crystallization formed a tri-nuclear oxo product Zr3(μ3-O)(μ-O i Pr)2(μ-OOCCHCl2)3(η-OOCCHCl2)2(O i Pr)3 (3a). The three zirconium atoms in the structure of (3) are forming an isosceles triangle with a triply bridged oxo moiety at its center. [Copyright &y& Elsevier]

Abstract: (Cp*=C5Me5) is obtained via reaction of MoCl5 with a mixture of Cp*K and NaBH4 followed by treatment with CHCl3. provides access to a large variety of other permethylmolybdenocene complexes which include (E=S, Se, Te), (E=S, Se, Te), (E=S, Se), , and . [Copyright &y& Elsevier]

Abstract: Compound MoO2Cl2(THF)2 reacts with two equivalents of 1,3-dialkyl substituted 4,5-dimethylimidazol-2-ylidenes to give the dioxomolybdenum(VI) complexes MoO2Cl2(LR)2 [R=Me (1), i-Pr (2)]. Treatment of MoO2Cl2(THF)2 with one equivalent of the N-heterocyclic carbenes LMe, L i-Pr and C1L n-Bu (LMe =1,3,4,5-tetramethylimidazol-2-ylidene, L i-Pr =1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, and C1L n-Bu =1,3-dibutyl-4,5-dichloroimidazol-2-ylidene) affords the monocarbene adducts MoO2Cl2(LR) [R=Me (3), i-Pr (4)] and MoO2Cl2(C1L n-Bu) (5), respectively. Decomposition of complexes 1–5 affords a molybdenum oxychloride anion [Mo2O5Cl4]2− as an imidazolium salt. [Copyright &y& Elsevier]

Abstract: 17O NMR spectroscopy of oxo ligand of oxo metalloporphyrin can be considered as an excellent means to derive information about structure, electronic state, and reactivity of the metal bound oxo ligand. To show the utility of 17O NMR spectroscopy of oxo ligand of oxo metalloporphyrin, 17O NMR spectra of oxo ligands of dioxo ruthenium(VI), oxo chromium(IV), and oxo titanium(IV) porphyrins are measured. For all oxo metalloporphyrins, well-resolved 17O NMR signals are detected in far high frequency region. The 17O NMR signal of the metal bound oxo ligand shifts high frequency in order of Ru(VI)

Abstract: Addition of trifluoroacetic acid to syn-[MoO(μ-N-o-tol)(S2CNEt2)]2 in chloroform affords tetranuclear [{Mo2O(S2CNEt2)(η1-O2CCF3)(μ-N-o-tol)2}2(μ-O)(μ-O2CCF3)2] which has been crystallographically characterised. It consists of four molybdenum(V) centres linked via bridging imido, trifluoroacetate and oxo ligands and results from replacement of a dithiocarbamate by two trifluoroacetate ligands. [Copyright &y& Elsevier]

Abstract: Addition of Na(silox) (silox=OSi t Bu3) to Cl4WO afforded (silox)2Cl2WO (3), and subsequent alkylation with appropriate Grignard reagents yielded (silox)2R2WO (4-R; R=Me, Et, n Pr, n Bu). 4-R adopt distorted trigonal bipyramidal structures with axial silox groups, as implied by the X-ray crystal structure of 4- n Bu. New metathetical procedures were utilized in the preparation of (silox)2M(O)2 (M=Mo, 6; W, 7); the addition of Na(silox) to (DME)Cl2M(O)2 (M=Mo, W) in THF afforded the dioxo species. None of the oxo complexes exhibited oxygen atom transfer (OAT) to PMe3. The thermolysis of 4-Et and 4- n Bu afforded olefin derivatives (silox)2(ole)WO (5-ole; ole=C2H4, C4H8) as the primary products. Thermal degradation of (silox)2(CD3CH2)2WO (4-CH2CD3) revealed H/D-scrambling among α- and β-positions indicative of reversible β-H-elimination prior to alkane loss. A brief discussion of the lack of OAT is presented. [Copyright &y& Elsevier]

Abstract: 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 (≈0.03Å) 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. [Copyright &y& Elsevier]

Studies on organometallic oxo complexes have intensified in recent years due to their implications in catalytic oxidations or as reagents in the oxidation of organic molecules. Synthesis of such complexes containing a hydrocarbon ligand besides the carbonyl and oxo provides an opportunity to obtain complexes with both low oxidation state metal carbonyl fragment and high oxidation state metal oxide fragment in the same molecule. Our attention has been focused on oxo incorporated metal acetylide complexes, in particular, to understand how oxo ligands bond to the metal atoms. Synthetic strategy, structural behavior and reactivity of oxo acetylide metal complexes and clusters are reviewed. [ABSTRACT FROM AUTHOR]

Abstract: The oxo-rhenium complexes [Re2O7] (1), [ReMeO3] (2), [Re(η5-C5H5)O3] (3), [ReO2Cl(DMSO)2] (4), [ReO2Me(PhCe:bold>5), and [ReOCl3(PPh3)2] (6) catalyze the hydrosilylation of aliphatic and aromatic aldehydes with dimethylphenylsilane in C6D6 solutions. Compound 1 catalyzes the hydrosilylation of aldehydes at room temperature, affording the corresponding silyl ethers in good yield, but is ineffective as ketone hydrosilylation catalyst. The reactions of aldehydes and ketones with dimethylphenylsilane using compounds 2–6 as catalysts, require heating at 80°C. The scope of rhenium oxides-mediated hydrosilylation with a variety of aldehydes and ketones has been studied. Methyltrioxorhenium(VII) (2) and oxotrichlorobis(triphenylphosphine)rhenium(V) (6) shown to be the most active and versatile catalysts for the hydrosilylation of aliphatic and aromatic aldehydes and also ketones. The dioxo-rhenium derivatives [ReO2Me(PhC [ReO2Cl(DMSO)2] also catalyze the reaction of dimethylphenylsilane and aldehydes, although longer reaction times were required. [Copyright &y& Elsevier]

Oxo‐ or hydroxo‐bridged diiron centers are ubiquitous in metalloenzymes such as hemerythrin (Hr), ribonucleotide reductase, methane monooxygenase, and rubrerythrin. In each enzyme the diiron core plays a central role in the highly specific reaction. To elucidate mechanisms of these reactions, many experimental studies have been carried out, and bioinorganic model compounds have also been synthesized for the purpose. In this study electronic structures of diiron centers for Hr model compounds are investigated from the viewpoint of magnetic interactions. To this end, the Hubbard model for the three‐center four‐electron bond is analytically solved to elucidate an important role of electron correlation and the resulting superexchange interaction between localized spins. The hybrid density functional theory (DFT) calculations also are performed for Hr model compounds to provide the natural orbitals and their occupation numbers, which are crucial for computations of several chemical indices, such as effective bond order, information entropy, and unpaired electron density. These indices are useful for characterization and understanding of chemical bonds in FeOFe cores. The calculated effective exchange integrals (Jab) are wholly consistent with the available experiments. The orbital interactions in the FeOFe cores are reconsidered in relation to recent work by other groups. It is found that magnetic interactions are sensitive to the hydrogen bonds in the systems and are related to effective regulation of the activity. Implications of the calculated results are discussed in relation to the nature of chemical bonds in the FeOFe cores of several biological systems. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 [ABSTRACT FROM AUTHOR]

The [ReOX3(OAsPh3)(AsPh3)] complexes react with pyrazole in dry tetrahudrofuran to give new monomeric oxo rhenium(V) complexes – [ReOX3(OAsPh3)(pzH)]. This paper presents synthesis and spectroscopic characterisation of [ReOX3(OAsPh3)(pzH)] compounds and X-ray structure of the bromine analogue. [Copyright &y& Elsevier]

The reaction of the tetramethylcyclopentadiene-silyl substituted derivative C5Me4(SiMe3)(SiMe2Cl) with MCl4 afforded the trichloro mono-tetramethylcyclopentadienyl complexes M(η5-C5Me4SiMe2Cl)Cl3 [M=Ti (1), Zr (2)] with selective elimination of SiMe3Cl. Compound 1 reacts with deoxygenated water in methylene chloride, with the evolution of HCl, to give the dinuclear titanium compound {Ti[μ-(η5-C5Me4SiMe2O-κO)]Cl2}2 (3), which was converted into the μ-oxo complex {Ti[μ-(η5-C5Me4SiMe2O-κO)]Cl}2(μ-O) (4) by a further hydrolysis reaction which occurred when a solution of 3 in toluene was refluxed for a long period of time in the air. Depending on the size of the alkyl ligand, reactions of the mononuclear compound 1 with an appropriate alkylating reagent rendered the peralkylated Ti(η5-C5Me4SiMe2R)R3 [R=Me (5), CH2Ph (6)] or partially alkylated {Ti[(η5-C5Me4SiMe2(CH2SiMe3)]Cl(CH2SiMe3)2} (7) compounds by a salt metathesis route. Attempts to synthesise a partially methylated or benzylated complex were unsuccessful. Treatment of the dinuclear compound 3 with four equivalents of MgClMe yielded the tetramethyl derivative {Ti[μ-(η5-C5Me4SiMe2O-κO)]Me2}2 (8), while the same reaction carried out with MgCl(CH2Ph) or Mg(CH2Ph)2·2THF gave the chloro-benzyl derivative {Ti[μ-(η5-C5Me4SiMe2O-κO)]Cl(CH2Ph)}2 (9) as an equimolar mixture of diastereomers, regardless of the molar ratio of the alkylating reagent used. All of the new compounds were characterised by elemental analysis and NMR spectroscopy. [Copyright &y& Elsevier]

The reactivity of mer-[ReOBr3(bipy)] (1) (bipy=bipyridine) towards gaseous nitric oxide has been investigated. The reaction of 1 with NO in bromoform has afforded only starting material, but in the presence of an excess of triphenylphosphine, the [ReBr3(NO)(bipy)] (3) has been obtained. Refluxing of 1 and PPh3 in CHBr3 has led to the isolation of [ReBr4(bipy)] (2). The complexes 1, 2 and 3 were characterised by IR, UV–Vis and magnetical measurements. Crystal and molecular structures of 1 and 2 have been determined. [Copyright &y& Elsevier]

A new series of oxorhenium(V) complexes were prepared by reaction of 8,17-dimethyl-6,15-dioxo-5,7,14,16-tetrahydrodibenzo[a,h][ 14 ] annulene-2,11-dicarboxylic acid(H 4 L), alone or with addition of PPh 3 or NaSCN, with H 2 [ReOCl 5 ]. Mononuclear complexes, [ReO(H 4 L)Cl]Cl 2 , [ReO(H 4 L)(PPh 3 )]Cl 3 , and [ReO(H 4 L)- (SCN)]Cl 2 were obtained in 6 N HCl, while the binuclear complex, [Re 2 O 3 (H 4 L) 2 ]Cl 4 was obtained in 2 N HCl. Thermal studies on these complexes showed the possibility of obtaining new complexes pyrolytically, where the complexes decompose through several isolable as well as nonisolable, intermediates during heating. [Re 2 O 3 (H 2 L) 2 ], [ReO(H 2 L)Cl], [ReO(H 2 L)(PPh 3 )]Cl, and [ReO(H 2 L)(SCN)], were synthesized pyrolytically in the solid state from the respective precursor rhenium complexes. All of the prepared complexes and their thermal products have octahedral configurations. The ligand (H 4 L) behaves either as a neutral tetradentate or dianionic tetradentate ligand towards the oxorhenium ions in these complexes. The carboxylate groups are not coordinated to oxorhenium ions, which was checked by the acidity test and/or addition of metal ions such as Cu(II) and Ni(II), where a variety of new complexes coordinated via carboxylate groups were obtained. The screening of antibacterial and antifungal activities on the free ligand and all complexes, showed higher antifungal activities against Alternaria alternata than against Aspergillus fumigatus . The structures of all complexes and the corresponding thermal products were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, 1 H-NMR and TG-DSC measurements as well as by mass spectrometry. [ABSTRACT FROM AUTHOR]

X-ray diffraction studies on $$[{\text{pyr}}^{{\text{2,5}}--{\text{Ph}}_{\text{2}} } ]_2 $$ Zn(THF) and $$\{ [{\text{pyr}}^{{\text{2,5}}--{\text{Ph}}_{\text{2}} } ]{\text{Zn(THF)}}_{\text{2}} (\mu _3 - {\text{O}}){\text{Zn - [pyr}}^{{\text{2,5}}--{\text{Ph}}_{\text{2}} } {\text{]\} }}_{\text{2}} $$ provide the first structural data on zinc pyrrolyl complexes. The Zn–N bond lengths in these pyrrolyl complexes are longer than the corresponding values for dialkylamido derivatives, consistent with the notion that the pyrrolyl ligand is a poorer π-donor. The structure of $$\{ [{\text{pyr}}^{{\text{2,5}}--{\text{Ph}}_{\text{2}} } ]{\text{Zn(THF)}}_{\text{2}} (\mu _3 - {\text{O}}){\text{Zn[pyr}}^{{\text{2,5}}--{\text{Ph}}_{\text{2}} } {\text{]\} }}_{\text{2}} $$ demonstrates the presence of an unprecedented planar [Zn4O2] moiety in which each oxo ligand bridges three zinc centers with a μ3-motif that complements the previous reports of μ2- and μ4-oxo bridges. [ABSTRACT FROM AUTHOR]

The crystal and molecular structure of the title compound, VOCl(O 2 CCH 3 )(4-CH 3 C 5 H 4 N) 2 , has been determined by single-crystal X-ray diffraction. The material crystallizes in the space group $P \bar {1}(\# 2)}$ with a = 7.822(2), b = 8.023(1), c = 14.841(2) Å, α = 99.73(1)°, β = 91.41(1)°, and γ = 117.13(1)°. The coordination geometry around the vanadium is a highly distorted octahedron. The molecule is remarkable for being a monomeric oxovanadium(IV) carboxylate. A generalized synthetic strategy is proposed for the preparation of oxovanadium(IV) monomers. [ABSTRACT FROM AUTHOR]