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.     

Ligandenaustauschreaktionen von Bis(acetylacetonato)dioxo-molybdän(VI). Kristallstrukturen von [Salicylaldehyd-benzoylhydrazonato(2–)]dioxo-methanol-molybdän(VI) und [Benzoylaceton-benzoylhydrazonato(2–)] dioxo-triphenylphosphanoxid-molybdän(VI)

Ligand Exchange Reactions of Bis(acetylacetonato)dioxo-molybdenum(VI). Crystal Structures of [Salicylaldehyde-benzoylhydrazonato(2–)]dioxo-methanol-molybdenum(VI) and [Benzoylacetone-benzoylhydrazonato(2–)]dioxo-triphenylphosphaneoxide-molybdenum(VI) The products of ligand exchange reactions between bis(acetylacetonato)dioxo-molybdenum(VI) and tridentate diacidic ligands H₂L in the presence of triphenylphosphane were found by mass spectrometry to be complexes of the type MoO₂L. In the case of salicylaldehyde 2-hydroxyanil MoL₂ could also be identified. The compounds MoO₂L were crystallized as complexes with methanol or triphenylphosphane oxide. Crystallographic data see “Inhaltsübersicht”.     

Chemical,electrochemical and structural studies of some cis -dioxomolybdenum(VI) complexes of two tridentate ONS chelating ligands

Several cis-dioxomolybdenum complexes of two tridentate ONS chelating ligands H₂L¹ and H₂L² (obtained by condensation of S-benzyl and S-methyl dithiocarbazates with 2-hydroxyacetophenone) have been prepared and characterized. Complexes 1 and 2 are found to be of the form MoO₂ (CH₃OH) L¹?·?CH₃OH and MoO₂L, respectively, (where L^2–?=?dianion of H₂L¹ and H₂L²). The sixth coordination site of the complexes acts as a binding site for various neutral monodentate Lewis bases, B, forming complexes 3–10 of the type MoO₂LB (where B?=?γ-picoline, imidazole, thiophene, THF). The complexes were characterized by elemental analyses, various spectroscopic techniques, (UV-Vis, IR and ¹H NMR), measurement of magnetic susceptibility at room temperature, molar conductivity in solution and by cyclic voltammetry. Two of the complexes MoO₂(CH₃OH) L¹?·?CH₃OH (1) and MoO₂L¹(imz) (5) were structurally characterized by single crystal X-ray diffraction. Oxo abstruction reactions of 1 and 5 led to formation of oxomolybdenum(IV) complex of the MoOL type.     

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.     

Dinuclear Molybdenum(II) Complexes with Thioether Functionalized Silylamide Ligands

Treatment of molybdenum(II) acetate with thioether functionalized silylamides R₂Si(NLi-C₆H₄–2-SR')₂ leads to the formation of dinuclear Mo^II complexes [Mo₂{R₂Si(NC₆H₄-2-SR')₂}₂]. According to X-ray crystal structure analyses the complexes [Mo₂{Me₂Si(NC₆H₄-2-SMe)₂}₂] and [Mo₂{Ph₂Si(NC₆H₄-2-SPh)₂}₂] comprise a Mo₂-unit which is coordinated by two μ-κ-N,N' silylamide ligands. The coordination sphere around the molybdenum atoms consists of two amide nitrogen atoms and two thioether sulfur atoms in a distorted square-planar arrangement. The Mo-Mo distances are 211.0(1) and 211.7(1) pm, resp. In the complex [Mo₂{Ph₂Si(NC₆H₄-2-SMe)₂}₂] the silyl amide units act as tetradentate κ-N,N',S,S'chelating ligands and the Mo-Mo distance is 218.6(1) pm.     

Thiosemicarbazone Complexes of Uranium

Acetylpyridine thiosemicarbazone, HAPTSC ( 1 ), reacts with uranyl nitrate in MeOH under formation of (H₂APTSC)[UO₂(NO₃)₂(μ‐OH)]₂ ( 2 ) or [ UO₂(APTSC)(MeOH)(MeO)]₂ ( 3 ) depending on the experimental conditions applied. Protonation of 1 and precipitation of the [UO₂(NO₃)₂(μ‐OH)]₂^2— dianion as acetylpyridinium thiosemicarbazone salt is observed when the reaction is performed without the addition of a base. The metal atoms are situated in the centres of distorted hexagonal bipyramids. The U—U distance is 3.892(1)Å. Addition of triethylamine results in deprotonation of HAPTSC and the formation of 3 which is an unusual dimer with four methanol/methanolato ligands of two metal sites sharing two protons. The U—U distance in this dimer is 5.313(1)Å. (Bu₄N)[UO(APTSC)Cl₂] ( 4 ) is obtained when (Bu₄N)₂[UO₂Cl₄] is used as precursor. The uranium atoms in 3 and 4 are seven co‐ordinate. Their co‐ordination polyhedra can best be described as pentagonal bipyramids. Compounds 3 and 4 represent the first examples of thiosemicarbazone complexes with actinide elements which haven been studied by X‐ray analysis.     

Synthesis, structure studies and electrochemistry of molybdenum(VI) Schiff base complexes in the presence of different donor solvent molecules

The reactions between bis(acetylacetonato)dioxomolybdenum(VI) and Schiff base ligands derived from 5-chlorosalicylaldehyde or 3-ethoxy-salicylaldehye, and 3-methoxy-benzoic hydrazide (m-anisic hydrazide), 2-furoic hydrazide or 2,4-dihydroxy-benzoic hydrazide in the presence of donor solvents yielded cis-dioxomolybdenum(VI) complexes with the general formula MoO₂L(D), where L = tridentate Schiff base ligand and D = dimethylsulfoxide, hexamethylphosphoramide, dimethylformamide, imidazole or methanol. The complexes were characterized by elemental analysis, electronic spectra, IR, ¹H and ¹³C NMR spectroscopies, thermogravimetric analysis, cyclic voltammetry, and the molecular structures of five of the dioxomolybdenum complexes were elucidated by single crystal X-ray diffractometion studies. In general, the complexes adopt an octahedral environment around the Mo center with a cis-oxo configuration. The other coordination sites are occupied by the imino nitrogen, phenoxyl oxygen, hydroxyl oxygen of the tridentate Schiff base and the donor atom of the solvent molecule. The structural data revealed that the labile coordination site, which is occupied by N or O atoms from the donor solvents, has a longer Mo-O or Mo-N bond distance.     

Synthesis and Structure of a Series of New Molybdenum(VI) Complexes with the Esters of 2‐Mercaptonicotinic Acid

The novel dioxomolybdenum(VI) complexes with methyl ( 1 ), ethyl ( 2 ), n‐propyl ( 3 ), i‐propyl ( 4 ), n‐butyl ( 5 ) and cyclohexyl ( 6 ) ester of 2‐mercaptonicotinic acid have been prepared in the reactions of MoO₂Cl₂ and MoO₂(acac)₂ (acac = 2,4‐pentandionate) with mercaptonicotinic acid in corresponding alcohol. The esterification reaction was catalyzed by Mo^V originated from the reduction of Mo^VI with mercaptonicotinic ‐SH group with simultaneous formation of S–S bond resulting from the condensation of two 2‐mercaptonicotinic molecules. The presence of Mo^V was proved by ESR spectra. The molecular and crystal structures of 1 , 2 , 3 and 4 as well as of the by‐products 1,1′‐dithio‐2,2′‐n‐butylnicotinoate ( 7 ) and tetramethylammonium hexachloromolybdate(V) ( 8 ) have been determined by a X‐ray single crystal diffraction. The complexes 1 – 4 contain MoO₂²⁺ core with octahedral coordination of each molybdenum atom complexed by two 2‐mercaptonicotinato N and S donor atoms.     

Synthesis,spectral characterization and crystal structure studies of a new hydrazone Schiff base and its dioxomolybdenum(VI) complex

A new hydrazone Schiff base, (E)-N′-(3-ethoxy-2-hydroxybenzylidene)isonicotinohydrazide (H₂L), has been prepared and characterized by elemental analyses, spectroscopic methods, and single-crystal X-ray diffraction. The corresponding dioxomolybdenum(VI) complex [Mo(O)₂(L)(CH₃OH)] was synthesized and characterized by spectroscopic methods and by single-crystal X-ray diffraction. The hydrazone ligand coordinates to Mo through the phenolate O, imine N, and enolic O. The Mo center displays a distorted octahedral geometry with the three donors of the ligands and an oxo defining the equatorial plane, and one methanol and another oxo occupying the axial positions.     

Coordinative Behaviour of Tridentate NS2‐Donor Ligands with Cadmium: Synthesis and Crystal Structures of New Complexes

The reaction of cadmium salts with various amounts of the tridentate NS₂‐chelating ligands 1‐(2‐mercapto‐acetophenone)‐4‐triphenylmethylthiosemicarbazone (H₂L¹) and 1‐(5‐mercapto‐3‐methyl‐1‐phenylpyrazole‐4‐carboxaldehyde)‐4‐triphenyl‐methylthiosemicarbazone (H₂L²) in the presence of bases like N‐methylimidazole (N–MeIm), pyridine (py) or triethylamine (Et₃N) provided a series of novel mono‐, di‐, tri‐ and heptanuclear cadmium complexes. They are of the general formulas [CdL¹(N–MeIm)]₂ ( 1 ), [CdL¹(py)]₂ ( 2 ), [CdL²(N–MeIm)]₂ ( 3 ), [CdL²(py)₃] · 0.25 C₆H₁₄ · 0.5 py ( 4 ), [Et₃NH]₂[Cd₃L ] · 7 MeOH ( 5 ), [Et₃NH]₂[Cd₃L ] ( 6 ) and [Et₃NH]₂[Cd₇L ] · 14 MeOH ( 7 ). The compounds were characterized by elemental analysis, IR‐ and ¹H‐NMR‐spectroscopy. Single‐crystal X‐ray structure analyses are reported for the complexes 2 , 4 , 5 and 7 . While 2 has a dimeric structure where each cadmium ion is pentacoordinated in a N₂S₃‐environment, 4 consists of a monomeric cadmium center with distorted octahedral N₄S₂‐coordination. The complexes 5 and 7 exhibit new structural types for tri‐ and heptanuclear cadmium compounds. It is shown that sulfur bridging might proceed via arylthiolates, iminothiolates or even both functions of the ligand. Aggregation is influenced by various factors like solvents, counterions and ligand properties.     

Syntheses, Characterization and Crystal Structures of New Nickel Complexes with 2,6-Bis(imino)pyridyl Ligands

Introduction In the past decade, the imino-complexes based on late transition metal have received significantly increasing attention for their excellent performance in the olefin polymerization area since Brookhart et al.[1-8]     

Syntheses, Characterization and Crystal Structures of New Nickel Complexes with 2,6-Bis （ imino ） pyridyl Ligands

In the past decade, the imino-complexes based on late transition metal have received significantly increasing attention for their excellent performance in the olefin polymerization area since Brookhart et al. demonstrated that the Ni( Ⅱ ) complexes incorporating with sterically hindered α-diimine ligands could be used in the polymerization of ethylene to form high molecular weight polymers.     

Syntheses and Characterization of Molybdenum Complexes with the (1,3-Dithioliumyl)diphenylphosphine Containing Ligands

Treatment of [Et₄N][Mo(CO)₅(PPh₂CS₂)], 1 with unsaturated organic halides afforded the neutral complexes Mo(CO)₅(PPh₂CS₂R) (R = CH₂CN, 2 ; R = CH₂C≡CH, 3 ). Alkylation reactions take place at the sulfur atom. Protonation of complex 2 and 3 with HBF₄ produced the intramolecular cyclization products [Mo(CO)₅(PPh₂CS₂C₂H₃N)][BF₄], 4 and [Mo(CO)₅(PPh₂CS₂C₃H₄)][BF₄], 5 , respectively. In complex 4 and 5 , two five-membered 1,3-dithiolium rings formed. Protonation of 3 to 5 is not reversible, but deprotonation of 4 by n-BuLi or PPh₃ gave 2 quantitatively. Treatment of 4 with n-Bu₄NF yielded complex Mo(CO)₅PPh₂F, 6 and 2 with 1:1 ratio, but in the reaction of 5 and n-Bu₄NF only compound 6 was formed. All of these complexes are identified by spectroscopic methods.     

8-Aminoquinoline as a new bidentate ligand for cis-MoO2: synthesis and characterization of a dioxomolybdenum(VI) amide [MoO2(NHC9H6N)2]

The reaction of (Bu₄N)₂[Mo₆O₁₉] with 8-aminoquinoline in the presence of DCC (N,N′-dicyclohexylcarbodiimide) afforded the cis-dioxo-Mo(VI) amide [MoO₂(NHC₉H₆N)₂], which was characterized by spectroscopy, mass spectrometry, ¹H NMR, and single-crystal X-ray analysis. X-ray crystallography shows that the complex exhibits a distorted octahedral geometry with each oxo ligand trans to the quinolyl nitrogen and the amido ligands are bound to the metal in an N,N-chelating fashion. The molecules form zigzag chains via C–H?···?O hydrogen bonds and the chains are connected into networks through interchain N–H?···?O hydrogen bonds.     

Conformation of the Dimethyl Maleate Ligands in a Molybdenum(0) Complex. Crystal Structure of d6 trans-Bis(Dimethyl Maleate)-Dicarbonyl-O-Phenylenediaminemolybdenum(O)

The solid-state structure of Mo(CO)₂(DMMA)₂(PDA) (DMMA = dimethyl maleate, PDA = o-phenylenediamine) was determined by X-ray diffraction of single crystal. The complex crystallizes in the hexagonal space group P₆122 with a = 11.085(5), b = 11.085(5), c = 33.653(21) Å, γ = 120°, and Z = 6. The geometry of this bis(DMMA) complex is distorted octahedral with the two CO groups cis to each other and trans to the PDA ligand and the two DMMA ligands trans to each other and cis to the two CO ligands. The orientations of the two trans DMMA ligands are mutually perpendicular and each DMMA ligand eclipses an N-Mo-CO vector. The carbon-carbon double bond of DMMA is bonded to molybdenum unsymmetrically with the olefin carbon adjacent to a coordinated amino group closer to the metal than that adjacent to a carbonyl group. The conformation of each DMMA is that the two ester groups attached to DMMA lie in the regions described by N-Mo-C and N-Mo-N. Bond-distance calculations indicate that each keto oxygen of the ester groups in the region described by N-Mo-C forms a hydrogen bond with an amino hydrogen on the PDA ligand; this hydrogen bonding is responsible for the observed conformation of the complex. The conformalion of this complex in the solid-state is in agreement with the results in solution predicted according to ¹H NMR spectral data.     

Zinc(II) and Cadmium(II) Metal Complexes with Bis(tetrazole) Ligands: Synthesis and Crystal Structures

Two new metal complexes [Zn( L¹ )]_n ( 1 ) and [Cd₃( L² )₂Cl₂(H2O)6]_n ( 2 ) (H₂ L¹ = 1,5‐bis(tetrazol‐5‐yl)‐3‐oxapentane, H₂ L² = bis(tetrazol‐5‐yl)methane) have been synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction analysis. Complex 1 was a 2‐D sheet constructed by L¹ and Zn(II) center, further assembled to form a three‐dimensional (3‐D) supramolecular networks through weak hydrogen‐bonding interactions. In the complex 2 , there were two unequivalent Cd(II) centers, and some of ligands L² adopted chelate coordination mode, and others adopted bridge coordination mode linking the Cd1 center and simultaneously bridging the Cd2 center, the Cl^‐ anions adopted μ₂ bridging mode, ligands L² and the Cl^‐ anions linked the Cd(II) centers to form a 3‐D supramolecular networks.     

Salicylaldehyde Isonicotinoylhydrazone (SAIH) as a Specific Analytical Reagent for the Selective Extractive Spectrophotometric Determination of Molybdenum (VI) in Presence of Several Cations

Abstract

An extraction study of 36 cations with SAIH into isoamyl alcohol in the presence of EDTA, ascorbic acid and IN HC10₄ showed that only Mo(VI) gave a stable yellow colored complex extractable into the organic phase. This effect was used for the selective extractive spectrophotometric determination of Mo(VI) in the presence of other tested cations.     

Synthesis,structure and properties of eight novel molybdenum(VI) complexes of the types: [MoO2LD] and [{MoO2L}2D] (L = thiosemicarbazonato ligand,D = N-donor molecule)

Eight new molybdenum(VI) complexes with 4-(diethylamino)salicylaldehyde and 2-hydroxy-3-methoxybenzaldehyde thiosemicarbazones have been prepared. They were characterized as mononuclear [MoO₂LD] or dinuclear [{MoO₂L}₂D] complexes. In all the compounds the MoO₂²⁺ core is coordinated by a tridentate ONS thiosemicarbazonato ligand and by the N-donor molecule (imidazole, pyridine or γ-picoline). All the complexes were characterized by chemical analysis, IR spectroscopy and thermogravimetry. Three of the mononuclear complexes, dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(pyridine)]molybdenum(VI), dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(γ-picoline)]molybdenum(VI) and dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(imidazole)]molybdenum(VI) were also characterized by single-crystal X-ray structural analysis. A spectrophotometric method for the determination of molybdenum based on extraction of ion-pairs formed by the cationic surfactant and the [MoO(SCN)₄]⁻ anion is described.     

Determination of Molybdenum(VI) At Trace Levels by a Catalytic Polarographic Method

Abstract

ARSTRACT

A d.c. polarography method for molybdenum (VI) determination at trace levels has been developed. The reaction is catalytic between molybdenum, salicylaldoxime (SCAD) and bromate in acetic-acetate medium. The obtained peak is proportional to molybdenum (VI) concentrations in the range 1.08.10^?a to 1.37.10^?6 M. The proposed procedure is selective, the most serious interferents being W(VI), Pb(II) and Fe(II). It is applied to molybdenum determination in steel samples after iron extraction by ethyl ether.     

Structural and Spectral Study of Nickel(II) Complexes of Pyridyl bis{3‐piperidyl‐, bis{hexamethyleneiminyl‐, bis{N(4)‐diethyl‐, and bis{N(4)‐dipropylthiosemicarbazones}

Pyridyl bis(N(4)‐substituted thiosemicarbazones), in which the substituents replacing the NH₂ group on the thiosemicarbazone moieties are piperidyl, H₂Plpip; hexamethyleneiminyl, H₂Plhexim; diethylamino, H₂Pl4DE; and dipropylamino, H₂Pl4DP, have been synthesized. These bis(thiosemicarbazones) and their nickel(II) complexes have been characterized with IR, electronic, mass, and ¹H and ¹³C NMR spectra. Crystal structures have been solved for H₂Plpip and all four nickel(II) complexes. H₂Plpip does not possess hydrogen bonding between the thiosemicarbazone moieties, but is in the Z isomeric form with intramolecular hydrogen bonding from both thiosemicarbazone moieties to pyridine nitrogen atoms. The nickel(II) complexes possess square‐planar N₂S₂ (i. e., imine nitrogen and thiolato sulfur atoms) centers and the two pyridine ring nitrogen atoms are not coordinated.