The crystal structure of (NH4)2[Mo2(S2)6].8/3H2

The black crystal of (NH₄)[Mo₂(S₂)₆]* 8/3 H₂O belongs to the orthorhombic system, space group D³₂-P22₁2₁, with a = 12.064(6), b = 12.534(4), c = 19.558(9)Å, V =2957(3)ų, Z = 4 and D_c = 2.23g.cm^?3. The intensity data were collected on a Syntex R3 four-circle diffractometer. The structure was solved by Patterson method and direct method, the light atoms (except H atoms) were obtained from ΔF syntheses. The structure was refined by least-squares with anisotropic thermal parameters. The values of R and R_w were 0.092 and 0.072 respectively. The crystal structure contains discrete dimeric cluster [Mo₂(S₂)₆]^2? ions, NH₄⁺ cations and H₂O molecules. There are two crystallographically independent [Mo₂S₂)₆]^2? ions in the crystal, one locates on general position [Figure 1(a)], the other locates on two-fold axis [Figure 1(b)]. It contains one and a half [Mo₂S₂)₆]^2? ions in an asymmetric unit. In [Mo₂S₂)₆]^2? each Mo is coordinated side on by four S₂^2? groups in a distorted dodecahedral arrangement, two of which are bridging and the other two are terminal. The Mo? S bond length is 2.441 Å (mean), and S? S is 2.049 Å (mean). The Mo? Mo distance is 2.784 Å (mean), which is to be regarded as a single bond length. The formal oxidation state of Mo is five, it is probably a mixed valence Mo^IV? Mo^VI, and so shows a remarkable deep colour.     

Einfache Darstellungsmethoden des einzigen bekannten Perthiometallats [(S2)2 Mo(S2)2Mo(S2)2]2−. Zur Kenntnis der Einheit {Mo2(S2)2}6+

Simple Preparation Methods of the Only Known Perthiometallate [(S₂)₂(Mo)S₂)₂ Mo(S₂)₂]^2? · On the Moiety {Mo₂(S₂)₂}⁶⁺ Different aspects of the preparation of the only known perthiometallate [(S₂)₂Mo(S₂)₂Mo(S₂)₂]^2? (a compound with the unusual coordination number (9) have been discussed. Simple preparation methods could be developed. A discussion of the properties of the stabilising central moiety {Mo(S₂)₂}⁶⁺ containing a metal-metal bond follows.     

On the preparation of binuclear S,S bridged molybdenum(V) complexes crystal and molecular structure of [Mo2S4(Et2dtc)2]

MoO₄^2? is reduced by diethyldithiocarbamate (Et₂dtc^?) on prolonged digestion in aqueous medium whereby the complex [Mo₂^VO₂S₂(Et₂dtc)₂] is formed. The central moiety Mo₂O₂S₂²⁺ has a high formation tendency. When [Mo₂^V(S₂)₆]^2? is refluxed with Et₂dtc^? in ethanol, [Mo₂^VS (Et₂dtc)₂] is formed, the X-ray crystal structure of which has been determined (space group P2₁2₁2₁, a = 10.550(2) Å, b = 13.820(5) Å, c = 14.723(12) Å, d_c = 1.90 g · cm^3?, Z = 4). The Mo? Mo distance of the diamagnetic compound is 2.817(2) Å and the average Mo=S_t distance 2.099(4) Å.     

On the studies of the vibrational spectra of cluster [Mo2O2S2(S2)2]2-

IR and Raman spectra of [Mo₂O₂S₂(S₂)₂]^2- were reported. The resonance Raman spectra and the depolarization ratios in CH₃CN solution were measured. By using the data of crystal structure, the simplified normal coordinate calculation of the stretching vibrations for anion [Mo₂O₂S₂(S₂)₂]^2- was performed. The results obtained are useful to assign the vibrational bands of some Mo-Fe-S clusters.     

Thiokomplexe des Molybdäns Kristallstruktur eines Mischkristalls (PPh3Me)2[Mo2Br6(NO)4]/(PPh3Me)2[Mo2Br6S2(NO)2]

Thiocomplexes of Molybdenum. Crystal Structure of a Mixed Single Crystal (PPh₃Me)₂[Mo₂Br₆(NO)₄]/(PPh₃Me)₂[Mo₂Br₆S₂(NO)₂] The reactions of (PPh₄)₂MoS₄ with MoBr₄ and MoBr₂(NO)₂ resp. lead to the binuclear complexes (PPh₄)₂[S₂MoS₂MoBr₃(SMe₂)] and (PPh₄)[S₂MoS₂MoBr₂(NO)₂], in which the molybdenum atoms are linked by sulfido bridges. The preparation of (PPh₃Me)₂S₆ and (AsPh₄)₂S₇ from Na₂S₄ and PPh₃MeBr, and AsPh₄Cl, respectively, in ethanol solution is described. Disulfido briges are a feature of (AsPh₄)₂[Mo₂Br₆(S₂)₂(SMe₂)₂], which is obtained from MoBr₄(SMe₂)₂ and (AsPh₄)₂S₇. Mixed single crystals containing 2/3 (PPh₃Me)₂[Mo₂Br₆(NO)₄] and 1/3 (PPh₃Me)₂[Mo₂Br₆S₂(NO)₂] are formed in the reaction of MoBr₂(NO)₂ with (PPh₃Me)₂S₆, as shown by X-ray single crystal structure determination. The compound crystallizes monoclinic in the space group C2/c (Internat. Tab. Nr. 15) with four formula units per unit cell (2351 independent observed reflexions, R_w = 0.037). The cell parameters are a = 1603 pm, b = 1549 pm, c = 1863 pm; β = 92.2°. The complexes consist of PPh₃Me^⊕ cations and the dimeric anions [Mo₂Br₆(NO)₄]^2? and [Mo₂Br₆S₂(NO)₂]^2? which occur in the ratio 2:1. In these the molybdenum atoms are connected via MoBr₂Mo bridges of slightly different lengths (Mo? Br 265 pm and 267 pm) forming a controsymmetric double octahedron. All molybdenum atoms have two terminal bromo ligands with Mo? Br bond lengths of 258 pm and 260 pm; in the [Mo₂Br₆(NO)₄]^2? ion each molybdenum has two covalently bonded nitrosyl groups on cis-position with Mo? N bond lengths of 183 pm. In the [Mo₂Br₆S₂(NO)₂]^2? ion one of the two nitrosyl groups at each metal atom is substituted by a terminal sulfido ligand with a Mo? S bond length of 240 pm. The i.r. spectra are reported.     

The Electron Transfer Series [MoIII(bpy)3]n (n=3+, 2+, 1+, 0, 1−), and the Dinuclear Species [{MoIIICl(Mebpy)2}2(μ2‐O)]Cl2 and [{MoIV(tpy.)2}2(μ2‐MoO4)](PF6)2⋅4 MeCN

The electronic structures of the five members of the electron transfer series [Mo(bpy)₃]ⁿ (n=3+, 2+, 1+, 0, 1?) are determined through a combination of techniques: electro‐ and magnetochemistry, UV/Vis and EPR spectroscopies, and X‐ray crystallography. The mono‐ and dication are prepared and isolated as PF₆ salts for the first time. It is shown that all species contain a central Mo^III ion (4d³). The successive one‐electron reductions/oxidations within the series are all ligand‐based, involving neutral (bpy⁰), the π‐radical anion (bpy^.)^1?, and the diamagnetic dianion (bpy^2?)^2?: [Mo^III(bpy⁰)₃]³⁺ (S=3/2), [Mo^III(bpy^.)(bpy⁰)₂]²⁺ (S=1), [Mo^III(bpy^.)₂(bpy⁰)]¹⁺ (S=1/2), [Mo^III(bpy^.)₃] (S=0), and [Mo^III(bpy^.)₂(bpy^2?)]^1? (S=1/2). The previously described diamagnetic dication “[Mo^II(bpy⁰)₃](BF₄)₂” is proposed to be a diamagnetic dinuclear species [{Mo(bpy)₃}₂(μ₂‐O)](BF₄)₄. Two new polynuclear complexes are prepared and structurally characterized: [{Mo^IIICl(^Mebpy⁰)₂}₂(μ₂‐O)]Cl₂ and [{Mo^IV(tpy^.)₂}₂(μ₂‐Mo^VIO₄)](PF₆)₂?4 MeCN.     

Synthese und Kristallstruktur von (PPh4)2[Mo2(S2)2Cl8] · 2 CH3CN und seine topotaktische Umwandlung zu (PPh4)2[Mo2(S2)2Cl8]

Synthesis and Crystal Structure of (PPh₄)₂[Mo₂(S₂)₂Cl₈] · 2 CH₃CN and its Topotactic Transformation to (PPh₄)₂[Mo₂(S₂)₂Cl₈] MoS₂Cl₃ was prepared from molybdenum and S₂Cl₂ at 200 °C. Its reaction with PPh₄Cl in acetonitrile yielded (PPh₄)₂[Mo₂(S₂)₂Cl₈] · 2 CH₃CN. In vacuum or upon warming, it loses the acetronitrile without degradation of the crystals. According to the X-ray crystal structure determinations both compounds, with and without acetonitrile, are triclinic. They contain the same [Cl₄Mo(μ-S₂)₂MoCl₄]^2– ions, in which the Mo atoms are joined by two disulfido groups and an Mo–Mo bond. Details of the crystal packings and their topotactic transformation are given.     

Periphere Anbindung von Quecksilber(II)-iodid an dreikernige Molybdän-Schwefel-Dithiophosphinatocluster: [Mo3S4(R2PS2)4HgI2] (R = Et,Pr)

Peripheral Bonding of Mercury(II) Iodide to Trinuclear Molybdenum-Sulfur-Dithiophosphinato Clusters: [Mo₃S₄(R₂PS₂)₄HgI₂] (R = Et, Pr) Reaction of Mo₃S₄(R₂PS₂)₄ 1 (a : R = Et, b : R = Pr) with HgI₂ in THF yields the diamagnetic title complexes [Mo₃S₄(R₂PS₂)₄HgI₂] 3 . The crystal structure of [ 3a (H₂O)] · 2 CH₂Cl₂ shows the complexes to consist of a triangular array of Mo atoms which are bridged by μ₂? S atoms and capped by a μ₃? S atom. Each of the Mo atoms is chelated by a dithiophosphinato ligand Et₂PS₂^? and in addition two Mo atoms are bridged by a Et₂PS₂^? ligand while the H₂O molecule is bonded weakly to the third Mo atom. Thus, all Mo atoms reveal a distorted octahedral coordination sphere. HgI₂ is ?peripherally”? bonded to the cluster via two S atoms, one of which belongs to a chelating ligand and the other one to the bridging ligand. Space group P1 , lattice constants a = 12.157(2), b = 15.284(3), c = 16.049(3) Å, α = 115.56(1), β = 107.35(1), and γ = 94.62(1)°; Z = 2, d_calc = 2.23 mg/mm³; 4 236 observed reflections, R = 0.068. In organic solvents complexes 3 are strong electrolytes. VT-³¹P NMR data suggest a stepwise dissociation of 3 with formation of [Mo₃S₄(R₂PS₂)₃] ⁺[(R₂PS₂)HgI₂]^? and elimination of the bridging ligand from the cluster.     

Collision-Induced Decomposition (CID) of Triangular [Mo3S7-xSex]4+ Complexes (x = 0,3,7). A liquid SIMS and FTMS/MS study of [Mo3S7-xSex(Et2NCS2)3] +

[Mo₃S(S₂)₃(dtc)₃]I, [Mo₃S(SeS)₃(dtc)₃](dtc), and [Mo₃Se(Se₂)₃(dtc)₃](dtc) (dtc = N,N-diethyldithiocarbamate) were investigated by liquid SIMS-FTMS. The fragmentation pathways were essentially the same for the three compounds and can be explained by two types of fragmentation processes: stepwise abstraction of S/Se atoms as exemplified by the series [Mo₃X_z(dtc)₃]⁺ (4 ? z ? 7, X = S, Se), and ligand dissociation, as indicated by the generation of [Mo₃X_z(dtc)₂]⁺ (5 ? z ? 7, X = S, Se). The exclusive elimination of the Se-atoms from [Mo₃S(S_ax-Se_eq)₃(dtc)₃]⁺ confirmed the inequivalent reactivity of the bridging atoms in axial and equatorial position as observed in previous studies. Collision-induced decomposition (CID) of [Mo₃S₇(dtc)₃]⁺ ( 1 ), [Mo₃S₆(dtc)₃]⁺ ( 2 ), [Mo₃S(S_ax–Se_eq)₃(dtc)₃]⁺ ( 3 ), and [Mo₃Se₇(dtc)₃]⁺ ( 4 ) revealed distinctly different fragmentation reactions for the SIMS and CID mode. CID of 1, 3 , and 4 resulted in a two-step reaction with the exclusive elimination of diatomic molecules XY (X,Y = S/Se). In the case of 3 , the selective elimination of Se₂ indicated the abstraction of two Se-atoms located in equatorial positions of two different bridging groups. This result is discussed in terms of mechanisms, based on labile M? X_eq and inert M? X_ax bonds with an intramolecular formation of a X₄ fragment prior to the elimination of X₂.     

[Mo4O4(μ-S)4(μ-OH)2(μ-H2O)(H2O)2(pba)]2−: An Original Coordination Mode for the Ligand 1,3-Propylenebis(Oxamate)

The novel polyoxothioanion [Mo₄S₄O₄(OH)₂(OH₂)₃pba]^2? where pba^4? ligand is the 1,3-propylenebis(oxamate), was prepared by reacting Mo₁₂S₁₂O₁₂(OH)₁₂(OH₂)₆ ring with [Cu-pba]^2? in aqueous medium. NaK[Mo₄O₄(μ-S)₄(μ-OH)₂(μ-H₂O)(H₂O)₂(pba)] ·7H₂O was isolated in the solid state and fully characterized by X-ray diffraction study (tetragonal, P4(2)/m [a=20.4962(4) Å; b=20.4962(4) Å; c=14.7013(5) Å). The molecular structure consists of an arc cycle shape tetranuclear enchainment {Mo₄S₄O₄(OH)₂ (OH₂)₃} closed by a pba^4? ligand. The 3-D packing, resulting from the connection between K⁺ and Na⁺ and the coordination complex {Mo₄-pba]^2? is described. The ¹H-NMR characterization of the complex in aqueous solution is given. The ¹H-NMR spectrum exhibits four signals assigned to four enantiotopic protons of the alkyl chain of the pba^4? ligand and is in agreement with crystal structure of the complex [Mo₄-pba]^2?. The compound was also characterized by infrared spectroscopy.     

Syntheses and crystal structures of quadruply bridged Mo2Se4 complexes containing functionalized cyclopentadienyl ligands: trans/anti − (η5-CH3O2CC5H4)2Mo2(μ-Se)2(μ-SeCH2Ph)(μ-SePh) and trans/syn-(η5-C2H5O2CC5H4)2Mo2(μ-Se)2(μ-SePh)2

Two quadruply bridged Mo₂Se₄ complexes trans/anti-(η⁵-CH₃O₂CC₅H₄)₂Mo₂(μ-Se)₂(μ-SeCH₂Ph)(μ-SePh) (1) from reaction of (η⁵-CH₃O₂CC₅H₄)₂Mo₂(CO)₄ with dibenzyldiselenide and trans/syn-(η⁵-C₂H₅O₂ CC₅H₄)₂Mo₂(μ-Se)₂(μ-SePh)₂ (2) from reaction of (η⁵-C₂H₅O₂CC₅H₄)₂Mo₂(CO)₂(μ-SePh)₂ with elemental selenium have been synthesized and characterized by elemental analyses, ¹H NMR and IR spectroscopy and their crystal structures have been unequivocally determined by x-ray diffraction analyses.     

Synthese und Kristallstruktur von (PPh4)2[Mo2NCl9]2, einem μ-Nitridokomplex mit Molybdän(V), und -(VI)

Synthesis and Crystal Structure of (PPh₄)₂[Mo₂NCl₉]₂, a μ-Nitrido Complex with Molybdenum (V) and (VI) The title compound is formed as a by-product in the partial oxidation of Mo₂NCl₇ with chlorine in POCl₃ solution, when the reaction mixture is treated with PPh₄Cl. The crystals, which are sensitive to moisture, are black in reflectance and red in transmittance. A more effective synthesis is the direct reaction of PPh₄[MoNCl₄] with MoCl₅ in dichloro methane. (PPh₄)₂[Mo₂NCl₉]₂ was characterized by the i.r. spectrum and by a structural analysis with X-ray data. The compound crystallizes triclinic in the space group P1 with two formula units per unit cell (9225 independent observed reflexions, R = 0.058). The cell parameters are (20°C): a = 1144 pm, b = 1517 pm, c = 2000 pm, α = 79.8°, β = 80.1°, γ = 72.1°. (PPh₄)₂[Mo₂NCl₉]₂ consists of PPh₄⊕ cations and the anions [Mo₂NCl₉]₂^22?, which dimerize via chloro bridges with Mo? Cl bons lengths of 243 pm and 287 pm. In the [Mo₂NCl₉]₂^2? units the molybdenum atoms are linked by Mo^VI?N? Mo^V bridges (bond angles 179° and 174°, resp.) with Mo? N bond lengths of 167 pm and 212 pm.     

A new class of 30-molybdo complexes: Formation,structure and electrochemical properties of bisselenitopyrophosphatotriacontamolybdate, [(SeO3)2(P2O7)Mo30O90]8−, and bispyrophosphatotriacontamolybdate, [(P2O7)2Mo30O90]8−

The tetrapropylammonium (Pr₄N⁺) salt of [(SeO₃)₂(P₂O₇)Mo₃₀O₉₀]^8? was prepared from a 75 mM Mo^VI–2.8 mM P₂O₇^4?–5.6 mM SeO₃^2?–0.95 M HCl–60% (v/v) CH₃CN system, where [(P₂O₇)Mo₁₈O₅₄]^4? and [H₆(SeO₃)₂Mo₁₅O₄₈]^4? are first formed, then being spontaneously fused into [(SeO₃)₂(P₂O₇)Mo₃₀O₉₀]^8?. The [(SeO₃)₂(P₂O₇)Mo₃₀O₉₀]^8? anion may be isotypic with [(HPO₃)₂(P₂O₇)Mo₃₀O₉₀]^8?, in which each side of a (P₂O₇)Mo₁₂O₄₂ fragment is capped by a B-type (HPO₃)Mo₉O₂₄ unit derived from [H₆(HPO₃)₂Mo₁₅O₄₈]^4?. [(XO₃)₂(P₂O₇)Mo₃₀O₉₀]^8? (X = HP, Se) have the same type of 30-molybdo framework as [(P₂O₇)₂Mo₃₀O₉₀]^8?, previously isolated by Koltz. These three 30-molybdo complexes with the same ionic charge of ?8 constitute a new class of polyoxometallates and have common properties of undergoing a two-electron reduction in the absence of H⁺.     

Solvothermal synthesis and crystal structure of the Mo(VI)-bridged helical chain containing Mo2(V) dimers: (C4H12N2)2[(MoV2O4)(MoVIO4)(C2O4)2]·2H2O

A new molybdenum complex (C₄H₁₂N₂)₂[(Mo^V₂O₄)(Mo^VIO₄)(C₂O₄)₂]·2H₂O, was solvothermally synthesized and characterized by single-crystal X-ray diffraction. The structure of the compound consists of oxalate acid-coordinated mixed-valent [Mo^V₂O₄][Mo^VIO₄] helical chains and protonated piperazine cations. The helical chains are built up from the [Mo^V₂O₄] units and [Mo^VIO₄] tetrahedral. The central axis about helical chain is a 2-fold screw axis. The compound crystallizes in the space group P2₁/n of monoclinic system with a = 11.396(2) Å, b = 14.107(3) Å, c = 15.805(3) Å, β = 102.09(3)°, V = 2484.6(9) Å³, Z = 4. Other characterizations by elemental analysis, IR, and thermal analysis for this compound are also given.     

Thiochloroanionen von Molybdän(IV). Die Kristallstruktur von (NEt4)3[Mo3(μ3-S)(μ-S2)3Cl6]Cl · CH2Cl2 Kristallstruktur,EPR-Spektrum und magnetische Eigenschaften von (NEt4)2[Mo2(μ-S2)(μ-Cl)2Cl6]

Thiochloro Anions of Molybdenum (IV). Crystal Structure of (NEt₄)₃[Mo₃(μ₃-S)(μ-S₂)₃Cl₆]Cl μ CH₂Cl₂. Crystal Structure, Magnetic Properties, and EPR-Spectrum of (NEt₄)₂ [Mo₂(μ-S₂)(μ-Cl)₂Cl₆] From molybdenum pentachloride and tetraethylammonium hydrogensulfide in CH₂Cl₂ an insoluble product of composition (NEt₄)₂[Mo₂S₃Cl₉] was obtained along with a brown solution, from which (NEt₄)₂[Mo₂(S₂)Cl₈] was crystallized. The insoluble product and NEt₄Cl react in CH₂Cl₂ to yield, among others, (NEt₄)₃[Mo₃(S)(S₂)₃Cl₆]Cl · CH₂Cl₂. The latter crystallizes in the orthorhombic space group Pnma, a = 2495.8, b = 1501.2, c = 1295.6 pm, Z = 4. According to the crystal structure determination (3070 observed reflexions, R = 0.049) the [Mo₃(S)(S₂)₃Cl₆]^2? ion consists of an Mo₃ triangle with Mo? Mo bonds, each side of the triangle is bridged by disulfido groups and one sulfur atom is capped over the Mo₃ triangle; the single chloride ion is looseley associated to three S atoms. (NEt₄)₂[Mo₂(S₂)Cl₈] also crystallizes in the space group Pnma, a = 1425.6, b = 1129.9, c = 2004.7 pm, Z = 4; structure determination with 1703 observed reflexions, R = 0.061. In the [Mo₂(S₂)Cl₈]^2? ion the Mo atoms are bridged via one disulfido group and two chlorine atoms. There is a Mo? Mo bond, but according to the magnetic properties and the EPR spectrum each Mo atom still possesses one unpaired electron.     

Two novel windmill-like tetrasupporting heteropolyoxometalates: [MoVI7MoVVIV8O40(PO4)][M(phen)2(OH)]2[M(phen)2(OEt)]2 (M=Co,Ni)

Two interesting neutral tetrasupporting heteropolyoxometalates: [Mo^VI₇Mo^VV^IV₈O₄₀(PO₄)][M(phen)₂(OH)]₂[M(phen)₂(OEt)]₂·xH₂O (phen=1,10-phenanthroline, EtOH=ethanol, M=Co, x=7, 1; M=Ni, x=6, 2) were hydrothermally prepared and structurally characterized. The mixed molybdenum–vanadium polyoxoanion [Mo^VI₇Mo^VV^IV₈O₄₀(PO₄)]⁴⁻ exist in both two complexes, which acts as a bridge to covalently link two pairs of transition metal complex fragments, generating neutral windmill-like trimetallic nanocluster polyoxometalates. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 reveal that antiferromagnetic exchange interaction exists in this type of trimetallic tetrasupporting heteropolyoxometalates.     

Studies of molybdenum thiolato-complexes. The crystal and molecular structures of two triply bridged Mo(V) dimers, [Bu 4 n N][Mo2O2Cl5(SPh)2] and [Mo2O3(SPh)2(S2CNMe2)2]

Summary The complex [Bu ₄ ⁿ N][Mo₂O₂Cl₅(SPh)₂] has been prepared by reaction of [Bu ₄ ⁿ N][MoO(SPh)₄] with stoichiometric amounts of HCl and characterised by single crystal X-ray structure analysis. The dimer is bridged by two oxo-groups and one chloride and each Mo has pseudo-octahedral co-ordination. The related compound [Mo₂O₃(SPh)₂(S₂CNMe₂)₂] was synthesised by reaction of [MoO₂(S₂CNMe₂)₂] with thiophenol in methanol and has also been characterised crystallographically. In this case the triple-bridge consists of two thiophenolate sulphurs and one oxo-group, each molybdenum having pseudo-octahedral geometry. These structures are compared with other triply-bridged species.     

Oxomolybdenum(V) complexes of bis-(2-benzimidazolyl) alkanes

Summary Oxomolybdenum(V) complexes of the type (LH₄) [MoOCl₅] (where LH₂ = dimethylene bis-2-benzimidazole or tetramethylene bis-2-benzimidazole), [MoOCl₃(LH₂)] (where LH₂ = tetramethylene bis-2-benzimidazole), [(Mo₂O₄Cl₂-(H₂O)₃)₂(LH₂)] (where LH₂ = dimethylene bis-2-benzimidazole, tetramethylene bis-2-benzimidazole or hexamethylene bis-2-benzimidazole) and [Mo₂O₃Cl₄(LH₂)₂] (where LH₂ = tetramethylene bis-5-nitro-2-benzimidazole) were prepared and characterised. The mononuclear complexes show u.v.-vis. absorptions characteristic of octahedral molybdenum(V). The dinuclear complexes do not absorb in the visible region, possibly due to the presence of an Mo₂O ₄ ^{2 +}} core, which is also indicated by their diamagnetic behaviour. The biological activities of the free ligands and their complexes have been studied.     

Synthesis and characterisation of binuclear oxo molybdenum(V) hypophosphite

Summary A binuclear oxo Mo^V hypophosphite of composition [Mo₂O₄(H₂PO₂)₂(H₂O)₂], is prepared by direct reduction of Mo^VI oxide hydrate (MoO₃·H₂O) with hypophosphorus acid in an argon atmosphere, and characterised by i.r., and electronic spectra, magnetic susceptibility and cyclic voltammetry measurements.¹H and³¹Pn.m.r., x-ray diffraction and thermal analysis data contribute to its molecular structure elucidation, and a dioxobridged dioxo Mo^V with bidentate hypophosphite ion and water molecule completing the octahedral coordination around each Mo atom is proposed.     

Über verschiedene Reaktionen der CO-verbrückten Komplexe [Mo(CO)3bipy]2 und [Mo(CO)3phen]2 (bipy = 2,2′-Bipyridyl,phen = 1,10-Phenanthrolin)

The interaction of [Mo(CO)₃bipy]₂ with various monodentate ligands L (L = NH₃, pyr, P(C₆H₅)₃, P(C₆H₅)Cl₂, CN^?, SO₂) yields, according to the reaction equation in ?Inhaltsübersicht”?, mixed tricarbonyl compounds Mo(CO)₃bipyL by cleavage of the CO bridges of the dimeric starting carbonyl. Oxidation of [Mo(CO)₃D]₂ (D = bipy, phen) by means of iodine, partly in the presence of free bipy or phen, leads to the covalent and ionic, respectively, compound types [Mo^II(CO)₃DI₂]₂, [Mo^I(CO)₂DI]₂, [Mo^II(CO)₂D₂I]I and [Mo^II(CO)₂D₂I]I₃.