Terminal Oxo Ligands Research Articles

Heterometallic carbonyl cluster oxide. Formation, structure and reactivity of WRe2 oxo-acetylide cluster compounds

Cluster [WRe2(C5Me5)(O)(CO)8(CCPh)]1a possessing a terminal oxo ligand is prepared by treatment of the acetylide cluster [WRe2(C5Me5)(CO)9(CCPh)] with O2 or N2O; hydrogenation of 1a affords three isolable clusters, showing an example of oxo-ligand mediated sequential conversion of acetylide to alkenyl and alkylidene.

Sulfurization and Selenization of the Halfsandwich Nitrosylmetal Complexes Cp*M(CO)2NO (M = Cr, Mo) and Cp*M(NO)I2 (M = Mo, W)

The photo-induced decarbonylation of Cp*Cr(CO)2NO in acetonitrile solution in the presence of excess sulfur leads to the cyclo-pentasulfido complex Cp*Cr(NO)(S5) (1 a), while in the case of limited sulfur supply the binuclear bis(µ-disulfido) complex Cp*2Cr2(NO)2(µ-S2)2 (4a) is formed preferentially. The corresponding reaction with elemental selenium produces Cp*2Cr2(NO)2(µ-Se2)2 (4b), irrespective of the available amount of selenium. Photodecarbonylation of Cp*Mo(CO)2NO gives only the binuclear derivates Cp*2Mo2(NO)2(µ-E2) (E = S (5a), Se (5b)) which are also obtained by treating Cp*Mo(NO)I2 with H2S or H2Se, respectively. Nitrosyl loss predominates if the tungsten complex Cp*W(NO)I2 is reacted with H2S; in an argon atmosphere the products are Cp*W(S)(S2)(I) (7a) and Cp*2W2(S)2(µ-S)2 (8a), while in air some Cp*W(NO)(S5) (3a) and the oxo compounds Cp*W(O)(S2)I (7c), Cp*2W2(O)2(µ-S)2 (8c) and Cp*2W2(S)(O)(µ-S)2 (8d) are formed. The analogous reaction with H2Se leads to Cp*W(NO)(Se5) (3b), Cp*2W2(O)2(µ-Se)2 (9c) and Cp*2W2(Se)(O)(µ-Se)2 (9d), respectively. The binuclear tungsten complexes 8a,c,d and 9c,d contain a central W(µ-E)2W framework (E = S or Se) which is unaffected by air, while terminal sulfido and selenido ligands are quantitatively converted into the corresponding terminal oxo ligands in the presence of air in CH2C12 or THF solution. With the preparation of Cp*2W2(O)2(µ-E)2 (E = S (8c) and Se (9c)), the series of dioxo complexes containing a pair of monochalcogen bridges (E = O, S, Se, Te) has become complete. The new complexes have been characterized by their IR (v(NO)), 1H and 13C NMR (Cp*) spectra as well as by electron-impact mass spectrometry. According to the X-ray structure analyses, the binuclear compounds Cp*2Cr2(NO)2(µ-S2)2 (4a) and Cp*2Mo2(NO)2(µ-Se2)2 (5b) contain two 14-electron [Cp*M(NO)2] fragments which are connected by a pair of dichalcogen (η1,η2-E2) bridging ligands (M = Cr or Mo, E = S or Se). The central M2E2 four-membered ring is not planar, and the binuclear molecules are chiral.

Oxygen atom transfer in the reaction between hexakis(dimethyl-tert-butylsiloxy)ditungsten and nitric oxide. A remarkable difference in the reactivity of the tungsten-tungsten triple bond as a function of the attendant ligands: Bu tO versus Bu tMe 2SiO

The siloxy complex W 2(OSiMe 2Bu t) 6 ( I) and NO react in hydrocarbon solvents in the presence of pyridine (py) to give the oxo tungsten compounds W(O)(OSiMe 2Bu t) 4(py) ( II), W 2(O) 4(OSiMe 2Bu t) 4(py) 2 ( III) and W(NO)(OSiMe 2Bu t) 3(py) 2 ( IV). The relative amounts of the oxo compounds II and III to the nitrosyl complex IV depends upon the reaction temperature with low temperatures (−72 °C) favoring the nitrosyl derivative IV. An intermediate in the reaction is formulated as W 2(μ-O)(OSiMe 2Bu t) 6(py) 2 and is formed along with N 2O after the coupling of two nitrosyl ligands. The N 2O liberated in the reaction is then also active in oxygen atom transfer to yield II and III along with N 2. Compounds II, III and IV are inert with respect to further reactions with NO and N 2O under the conditions leading to their formation. An alternative synthesis of IV involves the reaction between W(NO)(OBu t) 3(py) and Bu tMe 2SiOH (3 equiv.) in the presence of pyridine. Compounds II, III and IV have been characterized by single crystal X-ray crystallography, 1H and 13C NMR spectroscopy, IR spectroscopy and elemental analysis. Reactions employing 15N 18O have been monitored by 15N NMR spectroscopy and the products analyzed by mass spectrometry and IR spectroscopy. Compound II contains a distorted octahedral geometry about tungsten with trans oxo and pyridine ligands: WO=1.68(1), WO(siloxide)=1.90(1) (av.), WN=2.44(1) Å. Compound III involves an edge-shared bioctahedron with terminal and bridging oxo ligands: WO(oxo)=1.72(1), Wμ-oxo=1.95(1) (av.), WO(siloxide)=1.89(1) (av.) and WN=2.42(1) Å. Compound IV is pseudo-octahedral with trans nitrosyl and pyridine ligands: WN(nitrosyl)=1.74(1), WN(pyridine- trans)=2.34(1), WN(pyridine- cis)=2.29(1), WO=1.59(1) (av.) Å. A derivative of the intermediate W 2(μ-O)(OSiMe 2Bu t) 6(py) 2 was characterized by X-ray crystallography as W 2(μ-O)(μ-OBu t)(OSiMe 2Bu t) 5(py) 2 ( V). Compound V contains bridging oxo and t-butoxide ligands that span a formal tungsten-tungsten double bond, WW=2.488(1) Å. In contrast to the above Mo 2(OSiMe 2Bu t) 6 ( VI) (made by the addition of Bu tMe 2SiOH (6 equiv.) to Mo 2(OBu t) 6) and NO (>2 equiv.) react in hydrocarbon solutions to give [Mo(NO)(OSiMe 2Bu t) 3] 2 ( VII), an analogue of the previously structurally characterized compound [Mo(NO)(OBu t) 3] 2 that contains a centrosymmetric (ON)(O 2M(μ- O) 2MO 2(NO) skeleton with a linear MNO moiety and no MM bond. Crystallographic data for the compounds: II: space group P 1 , a=17.414(5), b=22.679(7), c=11.519(3) Å, α=99.77(2), β=102.15(2), γ=108.13(1)°, V=4089.00 Å 3, Z=4; III: space group P 1 , a=10.708(3), b=12.469(4), c=10.185(3) Å, α=107.44(1), β=111.56(1), γ=90.53(2)°, V=1195.75 Å 3, Z=1; IV: space group P2 1/ c, a=14.049(3), b=10.832(2), c=24.807(5) Å, β=102.00(1)°, V=3692.74 Å 3, Z=4; V: space group P 1 , a=14.881(3), b=17.245(3), c=12.830 Å, α=91.20(1), β=102.23(1), γ=76.34(1)°, V=3125.26 Å 3, Z=2.

Pathways for water oxidation catalyzed by the (.mu.-oxo)bis[aquabis(bipyridine)ruthenium](4+) ion

Resonance Raman (RR) spectra of the ({mu}-oxo)bis(cis-aquabis(2,2{prime}-bipyridine)ruthenium(III)) ion and its congeners in thermodynamically accessible III-IV, IV-V, and V-V higher oxidation states have been obtained in aqueous solutions under a wide range of medium conditions. The RR spectra were dominated by single bands at 370-403 cm{sup {minus}1}, assignable to the Ru-O-Ru symmetric stretching mode ({nu}{sub s}) on the basis of their {sup 18}O-isotope induced shifts. From the magnitudes of the shifts, the Ru-O-Ru angles were calculated to be 155-180{degree} for the various oxidation states. A band appearing at 812 cm{sup {minus}1} in the V-V ion which shifted to {approximately} 780 cm{sup {minus}1} in ({sup 18}O)H{sub 2}O was assigned to a Ru{double bond}O stretching mode of a terminal oxo ligand. Below pH 0.3 the bridging {mu}-oxo atom became protonated; for the other ions, hydrogen bonding to the bridge was indicated by D{sub 2}O-induced solvent shifts in {nu}{sub s}(Ru-O-Ru). An {sup 18}O-isotope labeling study of the water oxidation reaction established the existence of a pathway in which one atom of O{sub 2} was obtained from an aqua ligand. These results combined with published rate data suggest that this pathway involves solvent nucleophilic attack of a terminal oxo atom as the critical oxygen-oxygen bondmore » forming step, with the bridging oxygen atom serving the essential role of activating and/or orienting the reactant H{sub 2}O through formation of a strong hydrogen bond. A second major pathway, for which both O atoms were derived from solvent, was also identified, but no definitive evidence was obtained for a pathway for which both O atoms originated in coordinated H{sub 2}O.« less

Chemistry of molybdenum. Part 8. Syntheses, spectroscopy and electrochemical properties of molybdenum complexes containing dithioacid ligands

Complexes cis-[MoVIO2(aacda)2][aacda = 2-(alkylamino)cyclopent-1-ene-1-carbodithioate; alkyl = propyl (pacda) or butyl (bacda)] react with acids HX (X = BF4 or PF6) to form species [MoVIO(aacda)3]X 1a–1d, which contain an MoVIO core. Reactivity of the terminal oxo ligand of this core towards electron-donor reagents has been investigated. Non-oxo monomeric molybdenum(V) compounds [MoV(acda)(aacda)3]BF42a, 2b and [MoV(abt)(aacda)3]BF42c, 2d can be obtained when 2-aminocyclopent-1-ene-1-carbodithioic acid (Hacda) and o-aminobenzenethiol (Habt) are used for oxygen abstraction. With triphenylphosphine, however, the products are non-oxo molybdenum(IV) compounds [MoIV(PPh3)(aacda)3]BF43a, 3b. In frozen solution [dimethylformamide–MeCN (1 : 10 v/v), 140 K], compounds 2a–2d show ESR spectra with axial symmetry. The g and A tensor parameters (g∥≈ 1.977, g⊥≈ 1.975, A∥≈ 51.5 × 10–4 cm–1 and A⊥≈ 19.5 × 10–4 cm–1) for this series of molybdenum(V) compounds are very similar to each other indicating that the unpaired electron is located in a metal-centred orbital of essentially identical composition. Complexes 2a and 2b display two consecutive reversible one-electron waves in their cyclic voltammograms at E½=–0.24 and –0.45 V vs. saturated calomel electrode (SCE), which correspond to MoV–MoIV and MoIV–MoIII redox couples respectively. The molybdenum(IV) compounds 3a and 3b are seven-co-ordinate with a spin-triplet ground state (µeff, 2.48 and 2.53) and show two distinct redox waves due to the interconversion of the three [Mo(PPh3)(aacda)3]z(z=+1, 0 or –1) species. Half-wave potentials, E1/2, for these processes are at –0.36 (MoIV–MoIII) and –0.90 V (MoIII–MoII)vs. SCE. The presence of the strongly π-acceptor phosphine ligand facilitates the electrochemical generation of relatively scarce molybdenum(II) species.

The synthesis and crystal structure of a novel cubane-like complex of the MoAgS series: {MoAg 3S 3Cl}(PPh 3) 3O

A novel MoAgS cubane-like complex, {MoAg 3S 3Cl}(PPh 3) 3O, has been synthesized from AgCl, PPh 3 and Mo 2O 2S(S 2) 4 2− in appropriate conditions, and its X-ray crystal structure determined. The complex comprises one cubane-like cluster core {MoAg 3S 3Cl} 2+, three PPh 3 ligands attached to each silver atom and one terminal oxo ligand attached to the molybdenum atom [1.67(1) Å]. The mean distance of the molybdenum and silver atoms is 2.980(2) Å, which is too long to effectively bond. The bond lengths of the three AgCl bonds are in the same range and average to 2.810(4) Å.

Über Pterinchemie. 90. Mitteilung. Synthese und Kristallstruktur des ersten chinoiden Dihydropterinmolybdän (IV)-Komplexes

Synthesis and Crystal Structure of the First Quinoid Dihydropterinmolybdenum (IV) Complex The first molybdenum(IV) complex with a quinoid dihydropterin, i.e.2, was isolated and characterized by IR, UV and NMR data and single-crystal X-ray diffraction. The reaction of MoVIO2Cl2 with the biologically important 6β-5,6,7,8-tetrahydro-L-biopterin(2) (7) in MeOH gave almost quantitatively trichloro(1,5-quinoid-7,8-dihydro-6H-L-biopterin)oxomolybdenLim(IV) (2). The complex crystallizes with one molecule of MeOH in the noncentrosymmetric orthorhombic space group P212121 (No. 19) with unit cell dimensions a = 1009.3(3), b = 1104.7(3), and c = 1484.5(4) pm and Z = 4. The Mo-atom has a distorted octahedral geometry (Fig.1). It is coordinated by N(5) and O(4) of the pterin ligand. The distance of the Mo–N(5) bond (202 pm) is unusually short compared to similar complexes. O(4) is located trans to a terminal oxo ligand. The octahedral coordination is completed by three Cl-atoms in a meridional arrangement. Complex 2, with the Mo-atom in the enzyme-relevant oxidation state +IV and the pterin in the intermediate quinoid dihydro form, should lead to an extension of the proposed ‘common molybdenum cofactor’ model.

Dimolybdenum oxo-imido complexes: crystal structures of [(MeC 5H 4) 2Mo 2O 2(μ-O)(μ-NPh)] and [(MeC 5H 4)MoO(μ-NPh)] 2

Oxidation of [(MeC 5H 4)Mo(CO) 3] 2 ( 1) by nitrobenzene in refluxing toluene affords three dimolybdenum oxo-imido complexes [(MeC 5H 4) 2Mo 2O 2(μ-O)(μ-NPh)] ( 2), [(MeC 5H 4)MoO(μ-NPh) 2 ( 3), and [(MeC 5H 4) 2Mo 2O(NPh)(μ-O)(μ-NPh)] ( 4). Complexes 3 and 4 are isomers but do not interconvert. Complex 4 undergoes facile hydrolysis in hydrocarbonsolvents giving 2 and aniline. The X-ray crystal structures of compounds 2 and 3 have been determined. Both structures display a trans-disposition of methylcyclopentadienyl ligands and terminal oxo ligands. The Mo 2 (μ-X) 2 metallacore geometries are rigorously planar with the phenyl substituent(s) of the imido ligands being titled slightly out of this plane. The MoMo distances correspond to normal single bonds.

.mu.-Oxo-bis(oxo) dinuclear complexes of technetium(V) with amine phenol ligands: syntheses, characterization, and x-ray crystal structures

Technetium(V) complexes of three amine phenol ligands prepared by reducing Schiff bases derived from salicylaldehyde and 1,3-diaminopropane, 2,2-dimethyl-1,3-diaminopropane, and 1,4-diaminobutane have been synthesized. {sup 1}H and proton-decoupled {sup 13}C nuclear magnetic resonance spectra of the complexes have been recorded and compared with those of the parent ligands. The complexes have been characterized by infrared spectroscopy, visible-UV spectrophotometry, and x-ray crystallography. X-ray crystal structures show all three complexes are dinuclear with a {mu}-oxo-bis(oxo) (O{double bond}Tc-O-Tc{double bond}O) backbone. The distorted octahedral coordination of Tc(V) is completed by a tetradentate diamine diphenolate ligand. Neutrality of the complexes is achieved by deprotonation of the phenols and by terminal and bridging oxo ligands. The technetium complexes have either a true crystallographic center of symmetry or an approximate center at the bridging oxygen. 16 refs., 4 figs., 10 tabs.

L-Edge spectroscopy of molybdenum compounds and enzymes

Spectra at the molybdenum L{sub 2} and L{sub 3} edges have been recorded by use of synchrotron radiation and analyzed in terms of ligand field theory. Four distinct p {yields} d transitions were observed in the derivative spectra of molybdenum oxychloride complexes. Comparison with optical data for the same compounds, as well as for Tc analogues, showed that L{sub 2,3}-edge spectra qualitatively reflect the unfilled Mo d-level splittings. A semiempirical correlation scheme, using Racah parameters to correct for exchange and Coulomb interactions, predicted optical splittings with an accuracy of better than 5%. This capability was used to reject certain interpretations of the MoO{sub 4}{sup 2{minus}}, MoOCl{sub 4}(H{sub 2}O){sup {minus}}, and MoOCl{sub 5}{sup {minus}} spectra. Single-crystal spectra for (N(Et){sub 4})(MoOCl{sub 4}(H{sub 2}O)) helped confirm the assignments. Chemical effects on Mo L-edge spectra were surveyed for LMoOXY compounds, where L represents hydrotris(3,5-dimethyl-1-pyrazolyl)borate and X and Y are various ligands. Spectral sensitivity to oxidation state, terminal oxo vs terminal sulfido ligands, and different halide ions are also compared.

Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand

Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand

Multiple bonds between main group elements and transition metals: LXIX. Condensation reactions of methyltrioxorhenim with 8-hydroxyquinoline and 2-hydroxyaniline: new rhenium(VII) chelate complexes

The title compound methyltrioxorhenium, (CH 3ReO 3, 1), reacts with 8-hydroxyquinoline at room temperature to give the dinuclear Re VII complex [CH 3Re(O) 2(8-oxyquinoline)] 2O ( 2) in 90% yield. A single crystal X-ray diffraction study has shown that 2 has a dimeric octahedral structure with a total of four terminal oxo ligands and one bridging oxygen atom. By contrast, the more complex condensation reaction of 1 with 2-hydroxyaniline gives the mononuclear Re VII compound CH 3Re(O)(2-OC 6H 4NH) 2 ( 3) in 60% yield.

The crystal structure of tetraphenylphosphonium tetracyanohydroxooxorhenium(V)

The crystal structure of (PPh4)2[ReO(OH)(CN)4]·5H2O has been determined from three-dimensional x-ray diffraction data. The light brown crystals are monoclinic, space group P21/n, with cell dimensionsa=16.753(2),b=19.928(2),c=15.338(2) A and β=101,894(1)°,z=4, Dm=1.45(1) g cm−3. The anisotropic refinement of the 6088 observed reflections converged to R=0.077. The [ReO(OH)(CN)4]2− ion has a distorted octahedral geometry. Bond distances: Re =1.70(1), Re−OH=1.90(1) and ReℑCav=2.12(2) A. The Re atom is displaced by 0.08 A out of the plane formed by the four carbon atoms towards the terminal oxo ligand.

Why Are There No Terminal Oxo Complexes of the Late Transition Metals? or The Importance of Metal–Ligand π Antibonding Interactions

Abstract π antibonding interactions result from the overlap of a filled π symmetry ligand orbital with a filled metal d orbital. This antibonding plays an important role in the chemistry of π donor ligands such as oxo and alkoxide. It is in large part responsible for the lack of late transition metal complexes with terminal oxo ligands, and can explain some of the unusual chemistry of late metal alkoxide complexes.

UV-visible and raman spectroscopic studies of the hydrolysis of the uranyl(VI) ion in neutral and basic solutions at 25°C, 0,1 MPa

The hydrothermal reaction of UO3, WO3, and CsIO4 leads to the formation of Cs6[(UO2)4(W5O21)(OH)2(H2O)2] and UO2(IO3)2(H2O). Cs6[(UO2)4(W5O21)(OH)2(H2O)2] is the first example of a hydrothermally synthesized uranyl tungstate. It's structure has been determined by single-crystal X-ray diffraction. Crystallographic data: tetragonal, space group I4 cm, a=15.959(2)Å, c=14.215(1)Å, Z=4, MoKα, λ=0.71073Å, R(F)=2.84% for 135 parameters with 2300 reflections with I>2σ(I). The structure is comprised of two-dimensional ∞2[(UO2)4(W5O21)(OH)2(H2O)2]6- anionic layers that are separated by Cs+ cations. The coordination polyhedra found in the novel layers consist of UO7 pentagonal bipyramids, WO6 distorted octahedra, and WO5 square pyramids. The UO7 polyhedra are formed from the binding of five equatorial oxygen atoms around a central uranyl, UO22+, unit. Both bridging and terminal oxo ligands are employed in forming the WO5 square pyramidal units, while oxo, hydroxo, and aqua ligands are found in the WO6 distorted octahedra. In the layers, four (UO2)O5 polyhedra corner share with equatorial oxygen atoms to form a U4O24 tetramer entity with a square site in the center; a tungsten atom populates the center of each of these sites to form a U4WO25 pentamer unit. The pentamer units that result are connected in two dimensions by edge-shared dimers of WO6 octahedra to form the two-dimensional ∞2[(UO2)4(W5O21)(OH)2(H2O)2]6– layers. The lack of inversion symmetry in Cs6[(UO2)4(W5O21)(OH)2(H2O)2] can be directly contributed to the WO5 square pyramids found in the pentamer units. In the structure, all of these polar polyhedra align their terminal oxygens in the same orientation, along the c axis, thus resulting in a polar compound.

ChemInform Abstract: Multiple Bonds Between Main‐Group Elements and Transition Metals. Part 29. Reductive Carbonylation of High‐Valent Oxorhenium Complexes ‐ a New Route to Low‐Valent Carbonylrhenium Compounds.

AbstractThe Re(V) complexes (I) and (III) (obtained from (VII) and diphenylketene or phenyl isocyanate via the binuclear complex ((C5Me5)ReO2)2) can be reduced under CO with cleavage of the terminal oxo ligand to give the chiral Re(III) derivatives (II) or (IV).

Magnetic Properties of Some Molybdenum(V) Dimeric Coordination Compounds with Terminal Oxo-Ligands and Di-μ-, Di-μ-sulfido-or μ-Oxo-μ-sulfido- Bridges

Abstract Magnetic susceptibilities and electron spin resonances of Mo(V) dimers, Cs2[Mo2O2S2(ox)2(H2O)2]·2H2O, Ba[Mo2O4(ox)2(H2O)2]·3H2O, (pyH)4[Mo2O2S2(NCS)6], (pyH)4[Mo2O4(NCS)6]·H2O and (pyH)4[Mo2O3S(NCS)6] were observed at temperatures from 2 K to room temperature. The paramagnetic part of the magnetic susceptibilities of these compounds was small and approached zero with decreasing temperature. Under an applied magnetic field strength of 40 kOe, the susceptibilities had temperature independent regions but the spin susceptibilities derived from the electron spin resonances, observed at a magnetic flux density of about 3000 G, showed temperature dependences like antiferromagnetic dimers. This discrepancy was explained by a quasi alternating linear chain antiferromagnetic model. The corrections of the diamagnetic susceptibilities are discussed.

Rhenium complexes with di- and tri-thiolate ligands. The synthesis and X-ray crystal structures of square pyramidal [PPh4][ReO(SCH2CH2S)2] and [NMe4][ReS(SCH2CH2S)2] and trigonal prismatic [PPh4][Re{(SCH2)3CCH3}2

The complexes [PPh4][ReO(SCH2CH2S)2](1), [NMe4][ReS(SCH2CH2S)2](3), and [PPh4][Re{(SCH2)3CCH3}2](5) have been synthesised by the reactions of K2[ReCl6] or [ReOCl3(PPh3)2] with the respective polythiol in the presence of triethylamine in methanol solution. Complex (1) crystallises in space group Pcab with a= 15.122(3), b= 18.685(4), c= 19.648(4)A, U= 5 542.02 A3, and Z= 4. Structure solution based on 2 072 independent reflections was refined to R= 0.063. Complex (3) crystallises in space group P21/c with a= 9.539(3), b= 15.123(4), c= 21.815(4)A, β= 93.58(1)°, U= 3 140.9 A3, and Z= 8. Structure solution based on 3 329 independent reflections was refined to R= 0.029. Complex (5) crystallises in space group P21/n with a= 11.506(3), b= 17.096(4), c= 18.115(4)A, β= 102.32(1)°, U= 3 488.9 A3, and Z= 4. Structure solution based on 2 380 independent reflections was refined to R= 0.0517. The [ReS(SCH2CH2S)2]– and [ReO(SCH2CH2S)2]– anions exhibit square pyramidal geometry with a terminal sulphido or oxo ligand in the apical position. The S2– ligand is derived from decomposition of the 1,2-ethanedithiolate anion with elimination of ethylene. The [Re{(SCH2)3CCH3}2]– anion has a six-co-ordinate Re atom in a trigonal prismatic co-ordination sphere. The factors responsible for the adoption of the trigonal prismatic structure are discussed.

Dialkylhydroxylamido(1—)-O,N Complexes of Tungsten(VI) with Terminal Oxo and Thio Ligands

The compounds cis -[WO2(R2NO)2] (R = Et, PhCH2, �C5H10) have been synthesized by the reaction of WO2Cl2 or [WO2(C5H7O2)2] with the respective N,N- dialkylhydroxylamines in the presence of Et3N. When heated with WO2Cl2 in refluxing MeCN , Et2NOH undergoes dealkylation and MeCN insertion to produce cis -[WO2(NH(Me)CN(Et)O)2] which features the bidentate N-ethyl-N- hydroxyacetamidinato (1-)-O,N′ ligand . cis - [WS2(R2NO)2] and cis -[WOS(C5H10NO)2] can be isolated in satisfactory yields by the reaction of [WO2(R2NO)2] with B2S3. The new compounds have been characterized by microanalysis, by infrared and elecronic spectroscopy and by 1H, 13C and 183W n.m.r.

Die Kristallstruktur von Di-μ-oxo-cis-dioxo-dichloro-bis(2,2′ -bipyridyl)- molybdän(V) (Mo–Mo)-Nitromethansolvat, Mo2O4Cl2(bipy)2 · CH3NO2/ Crystal Structure of Di-μ-oxo-cis-dioxo-dichloro-bis(2,2′-bipyridyl)- molybdenum(V) (Mo–Mo) Nitromethane Solvate, Mo2O4Cl2(bipy)2 ´ CH3NO2

Abstract Mo2O4Cl2(bipy)2 has been obtained by oxidation of MoCl4(bipy) with O2 in ethanol/H2O . The complex crystallizes from CH3NO2 with one solvent molecule per formula unit in the monoclinic space group P 21/n: a = 954.1(2), b = 1925.3(2), c = 1423.2(2) pm, β = 102.48(2)°, Z = 4. The characteristic unit Mo2O4 2+ of the dinuclear complex consists of two terminal oxo ligands in a cisarrangem ent and two bridging oxygen atoms forming a non-planar Mo2O2 ring. A strong Mo -Mo single bond is indicated by a short distance of 256.5 pm. The coordination of both Mo atoms is completed by a Cl atom and a chelating bipyridyl ligand.