Binuclear molybdenum(V) complexes with morpholin carbamate

Summary Novel oxo-and sulphido-bridged molybdenum(V) complexes with morpholin carbamate as ligand, have been prepared, identified by i.r., electronic spectra, magnetic susceptibility and analytical data and assigned the formulae [Mo₂O₃(LL)₄], [Mo₂O₄(LL)₂], [Mo₂O₂S₂(LL)₂] and [Mo₂O₃S(LL)₂]. The spectra are modified by introduction of sulphur atoms into the bridge system. The low magnetic moments are thought be due, at least in part, to intramolecular metal-metal interactions. A comparison of the spectra of these complexes with those of analogous morpholin dithiocarbamate compounds has been made.     

Molybdenum(V) dimeric complexes with dialkyl carbamates

Syntheses are reported for a number of novel oxo and sulphido bridged molybdenum(V) complexes with N-methyl-N-cyclohexyl carbamate and N,N-dicyclohexyl carbamate as ligands, and we have compared these complexes with the molybdenum(V) complexes with dialkyldithiocarbamates as ligands. These complexes were identified by IR and electronic spectra, magnetic susceptibility and analytical data, and were assigned the formulae [Mo₂O₃(LL)₄], [Mo₂O₄(LL)₂], [Mo₂O₂S₂(LL)₂] and [Mo₂O₃S(LL)₂]. IR and electronic spectra of these compounds are sensitive to substitution of sulphur atoms into the bridge system. It is suggested that the low magnetic moments observed are due, at least in part, to intramolecular metal-metal interactions.     

Hydroxamic acid dinuclear complexes of molybdenum(V) and molybdenum(III)

Summary Molybdenum(V) and molybdenum(III) complexes [Mo₂O₃L₄] and [Mo₂L₆] derived from hydroxamic acids (HL) were prepared and identified by Raman, i.r., e.s.r., electronic spectra and analytical data. The low magnetic moments of the dinuclear complexes are due to in part to intramolecular interactions. Electronic spectra and vibrational studies indicate the presence of a Mo₂O₃ core in the molybdenum(V) complexes. The relative intensities of the, main and satellite peaks in e.s.r. spectra indicate the dinulcear nature of molybdenum(III) hydroxamates.     

Oxomolybdenum(VI) and oxomolybdenum(V) thiocarbohydrazone complexes

Summary Dioxomolybdenum(VI) complexes [MoO₂L]H₂O and oxomolybdenum(V) complexes [Mo₂O₃L₂]H₂O and [Mo₂O₃(LH)₂(OH)₂(H₂O)₂] (where LH₂=thiocarbohydrazones derived from thiocarbohydrazide with salicylaldehyde, 5-methyl-, 5-chloro-, 5-bromo-, 3-methoxysalicylaldehyde and 2-hydroxy-1-naphthaldehyde) have been prepared and characterised by elemental analysis, conductivity, magnetic moment, i.r., u.v-vis, e.p.r. and thermal studies. The data suggests that molybdenum(VI) complexes are non electrolytes, diamagnetic, monomeric and have distorted octahedral geometry, whereas the molybdenum(V) complexes are non electrolytes, paramagnetic and have distorted octahedral structures with possible metal intereaction via oxo bridging.     

Synthesis and characterization of oligomeric molybdenum complexes of N-alkylphenothiazines

Summary Polynuclear molybdenum(IV/V) oxide - phenothiazine complexes which are oligomeric in nature have been prepared. The complexes were characterized by elemental analyses and spectroscopic data. The molecular formulae of the new complexes are [Mo₄O₉(OH₂)₂(PTZ)₂], PTZ = chlorpromazine or promethazine, [Mo_{4 8}(OH₂)₂(TR)₂], TR = thioridazine, [Mo₅O₁₀(OH_O2)₂(EP)₂], EP = ethopropazine, and [Mo₆O₁₂(OH₂)₂(TF)₂], TF = trifluoperazine. Tentative structures are proposed.     

Structural studies of new group 6 complexes of salicylidene-2-aminopyridine

Interaction of salicylidene-2-aminopyridine (Hsap) with [M(CO)₆], M = Cr, Mo and W, in THF under sunlight resulted in formation of dinuclear complexes [Cr₂O₄(sap)], 1, [Mo₂O₄(sap)], 2, and [W₂O₅(sap)₂], 3. Elemental analysis, spectroscopic and magnetic studies of the reported complexes revealed the proposed structures. Magnetic studies of 1 and 2 suggested that the two metal centers have +3 and +6 formal oxidation states, while the tungsten complex 3 has +6 formal oxidation state with d⁰ electron configuration. The thermal properties of the complexes were investigated by thermogravimetry.     

Oxomolybdenum(V) complexes of 2-benzothiazolyl hydrazones

Summary Oxomolybdenum(V) complexes of general formulae [Mo₂O₃L₂Cl₂]H₂O and [Mo₂O₃L₂(OH)₂(H₂O)₂] (LH = hydrazones derived from 2-hydrazinobenzothiazole with salicyladehyde, 5-methyl-, 5-chloro-, 5-bromo-, 3-methoxysalicyldehyde and 2-hydroxy-1-naphthaldehyde) have been prepared and characterized by elemental analysis, conductivities, magnetic moments, thermal studies, and i.r., u.v.-vis. and e.p.r. spectra. The data suggest that the complexes are non-electrolytes, paramagnetic and have distorted octahedral structures with possible metal-metal interactions via oxo bridging.     

Synthesis and characterization of potassium 1,3-bis(N-methylpiperazino)propan-2-O-xanthate and the complexes of Co(II), Ni(II) and Cu(I) ions

Potassium 1,3-bis(N-methyl piperazino)propan-2-O-xanthate (LK), and its complexes with Co(II), Ni(II) and Cu(I) ions have been prepared and characterized as [CoL₂(H₂O)₂], [NiL₂(H₂O)₂]·2H₂O and CuL·2H₂O by FT-IR, ¹H and ¹³C?NMR spectroscopies, elemental analyses, magnetic susceptibility and TGA techniques.     

Reactions of molybdenum(III) with macrocyclic polythiaethers

Reactions of MoCl₃(THF)₃ and MoCl₃(PrCN)₃ with the macrocyclic polythiaethers: 1,4,8,11-tetrathiacyclotetradecane (TTP) and 1,4,7,10,13,16-hexathiacyclooctadecane (HTO) were studied. The type of reaction and the complexes formed depend on reactant concentration and nature of the solvent. The complexes: [MoCl₃(HTO)], [(MoCl₃)₂(HTO)(THF)₃], [MoCl₃(TTP)(THF)] and [MoCl₃(TTP)] in which the macrocyclic polythiaethers are coordinated to the molybdenum through sulphur atoms were isolated. Some new mixed-valence complexes were formed in reactions where a partial change in the molybdenum oxidation state and a cleavage of the macrocyclic ring took place. The following complexes were isolated: [Mo₃Cl₉(PHT)₂(PrCN)]·CH₂Cl₂, [Mo₃Cl₉(PHT)₂(THF)] · CH₂Cl₂, [Mo₂Cl₆ (PHT)] · CH₂Cl₂, [Mo₃Cl₉(TTT)₂(THF)] · CH₂Cl₂, where PHT = 3,6,9,12,15-pentathiaheptadec- 16-ene-1-thiolato(1-) and TTT = 4,7,11-trithiatridec-12-ene-1-thiolato(1-). The complexes were characterized on the basis of elemental analyses, magnetic measurements, IR, ¹H NMR, ¹³C NMR and mass spectra.     

Cobalt(II) complexes with aminopolycarboxylate 1,3-pdta-type ligands: synthesis and characterization of trans(O6)-[Mg(H2O)6][CoII(1,3-pddadp)]·H2O

Starting from Ba₂(1,3-pddadp)·8H₂O (1,3-pddadp=1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) and CoSO₄, a new hexadentate [Co^II(1,3-pddadp)]²⁻ complex has been prepared. The trans(O₆) geometry of this complex was confirmed by comparison of its i.r. and u.v.–vis. spectra with those of [Co^II(1,3-pdta)]²⁻ (1,3-pdta is the 1,3-propanediaminetetraacetate ion) and trans(O₆)-[Co^III(1,3-pddadp)]⁻ complexes of known X-ray crystal structure. Magnetic and electrolytic conductivity properties of these complexes have also been discussed.     

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.     

Synthesis,Structure and Characterization of Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo₂^VO₃L₂] [L = thiosemicarbazonato ligand: C₆H₄(O)CH:NN:C(S)NHR′ and C₁₀H₆(O)CH:NN:C(S)NHR′; R′ = H, CH₃, C₆H₅) were obtained either by oxygen atom abstraction from Mo^VIO₂L with triphenylphosphine or by using [Mo₂O₃(acac)₄] in the reaction with the corresponding ligands H₂L. Crystal and molecular structure of [Mo₂O₃{C₆H₄(O)CH:NN:C(S)NHC₆H₅}₂] · CH₃CN has been determined by the single‐crystal X‐ray diffraction method.     

Synthesis of homobimetallic molybdenum(VI) complex of bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone and its reaction with electron and proton bases

The diamagnetic dioxomolybdenum(VI) complex [(MoO₂)₂(CH₂L)(H₂O)₂]H₂O (1) has been isolated in solid state from reaction of MoO₂(acac)₂ with bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH₂LH₄) in 3:1 molar ratio in ethanol at higher temperature. The reaction of the complex (1) with electron donor bases gives diamagnetic molybdenum(VI) complexes having composition [Mo₂O₅(CH₂LH₂)]·2A·2H₂O (where A = pyridine (py, 2), 2-picoline (2-pic, 3), 3-picoline (3-pic, 4), 4-picoline (4-pic, 5)). Further, when the complex (1) is allowed to react with protonic bases such as isonicotinoylhydrazine (inhH₃) and salicyloylhydrazine (slhH₃), reduction of molybdenum(VI) centre occurs leading to isolation of homobimetallic molybdenum(V) complexes [Mo₂(CH₂L)(inh)₂(H₂O)₂] (6) and [Mo₂(CH₂L)(slh)₂] (7), respectively. The composition of the complexes has been established by analytical, thermo-analytical and molecular weight data. The structure of the molybdenum(VI) complexes (1)–(5) has been established by electronic, IR, ¹H NMR and ¹³C NMR spectral studies while those of the complexes (6) and (7) by magnetic moment, electronic, IR and EPR spectral studies. The dihydrazone is coordinated to the metal centres in staggered configuration in complex (1) while in anti-cis configuration in complexes (2)–(7). The complexes (6) and (7) possess magnetic moment of 2.95 and 3.06 BM, respectively, indicating presence of two magnetic centre in the complexes per molecule each with one unpaired electron on each metal centre without any metal–metal interaction. The electronic spectra of the complexes are dominated by strong charge transfer bands. All of the complexes involve six coordinated molybdenum centre with octahedral arrangement of donor atoms except in the complex (6), in which the molybdenum centre has rhombic arrangement of ligand donor atoms. The probable mechanism for generation of oxo-group in the complexes (2)–(5) involving coordinated water molecule has been proposed.     

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.     

Diazabutadiene cobalt(II) complexes

Summary Studies on the chelates of cobalt(II) with the bidentate ligands 1,4-diphenyl(2,3-dimethyl-1,4-diazabutadiene) (PMB) and 1,4-di(p-methoxyphenyl)-2,3-dimethyl-1,4-diazabutadiene (MPMB) have been carried out. On the basis of elemental analyses, the complexes are [Co(PMB)Cl₂], [Co(PMB)₂(C1O₄)₂], [Co(MPMB)Cl₂] and [Co(MPMB)₂(ClO₄)₂].Both ligands are bidentatevia nitrogen atoms in all the complexes. The magnetic susceptibility and i.r. and u.v.-visible spectra are reported and discussed. The chloro-compounds involving two chlorine ligands and, in the perchlorate compounds, the ClO ₄ ^– groups are bound to the cobalt(II) centre.     

New Molybdenum(V) Complexes Prepared by the Oxidation of Dinuclear Quadruply-Bonded Molybdenum(II) Monothiocarboxylates

Oxidation of molybdenum(II) thiopivalate and thiobenzoate in the presence of -picoline or pyridine results in the formation of dinuclear molybdenum(V) complexes of the general formulae [Mo₂O₂(-O)₂(-SO₄)L₄] with L = -picoline or pyridine and [Mo₂O₂(-O)(-S)(-SO₄)L₄] with L = -picoline. As determined by X-ray structure analysis, two complexes with -picoline differ in their bridging cores: In one complex, two Mo atoms are doubly bridged through two oxygen atoms; in the other, one Mo atom is doubly bridged through oxygen and sulfur atoms. However, they both crystallize together. The product is solvated with -picoline and water molecules. Molybdenum atoms exhibit distorted octahedral coordinations. The same complexes were prepared also through direct reactions of [Mo₂O₃(O₂CCH₃)₄] with thiopivalic and thiobenzoic acid in the presence of -picoline or pyridine. The appearance of the oxo-oxygens and sulfido-sulfur as well as sulfato ligand is explained by the molybdenum-catalyzed oxidation of thiocarboxylates.     

Dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines and their interactions with L-cysteine and L-histidine

Six new dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines having the general formula M₂O₄(L)₂(H₂O)₂ [where M = molybdenum or tungsten and L = N-alkylphenothiazines] have been synthesised. The complexes have been characterised on the basis of analytical, molar conductance, magnetic susceptibility, spectral data, TGA and DTA. The low magnetic moments for the complexes are due to spin-spin interaction or metal-metal bonding. The interactions of these complexes with some biologically important amino acids have been studied.     

Synthesis and spectroscopic properties of novel polynuclear molybdenum(VI) peroxo complexes containing amino acids

The interaction of an aqueous MoO₃ solution with H₂O₂, and glycine, serine, lysine, histidine or methionine, results in the precipitation of mononuclear MoO(O₂)₂LH₂O (L = glycine), dinuclear Mo₂O₄(O₂)₂L(H₂O)₄ (L = methionine, serine) and trinuclear Mo₃O₇(O₂)₂L(H₂O)₆ (L = lysine, histidine) species. A detailed analysis of the electronic spectra has been performed using the digital filter method. It was found that the polynuclear complexes preserve the individuality of the molybdenum oxo peroxo core.     

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.     

Dimeric copper(II) trimethylsilyl­acetate adducts with pyridine, 2‐­methylpyridine, 3‐methylpyridine and quinoline,and a polymeric copper(II) trimethylsilylacetate

In the crystals of bis(pyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₅H₅N)₂], (I), the dinuclear Cu^II complexes have cage structures with Cu?Cu distances of 2.632 (1) and 2.635 (1) Å. In the crystals of bis(2‐­methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (II), bis­(3‐methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (III), and bis(quinoline‐N)­tetrakis(μ‐­trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₉H₇N)₂], (IV), the centrosymmetric dinuclear Cu^II complexes have a cage structure with Cu?Cu distances of 2.664 (1), 2.638 (3) and 2.665 (1) Å, respectively. In the crystals of catena‐poly­[tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II)], [Cu₂(C₅H₁₁O₂Si)₄]_n, (V), the dinuclear Cu^II units of a cage structure are linked by the cyclic Cu—O bonds at the apical positions to form a linear chain by use of a glide translation.