Redistribution reactions in the ion source of a mass spectrometer of complexes of titanium (iv), tin (iv) and germanium (iv) with 8-quinolinolato and halo or ethoxy ligands

The relative intensities of peaks in the mass spectra of the compounds MX_4?nox_n (oxH = 8-quinolinol; n = 2; M = Ti; X = F, Cl, Br or OEt; M = Sn; X = F, Cl, Br or I; M = Ge; X = Cl or Br; n = 1; M = Ti; X = OEt) depend on the insertion temperature and the residence time of the sample in the mass spectrometer. In most cases ions which cannot arise by fragmentation of the respective molecular ions are observed. These ions arise from the ionisation and fragmentation of species which are due to redistribution reactions in the mass spectrometer. The fragmentation pattern of the compounds MX₂ox₂ (X = halogen), mainly involving loss of ligand radicals, is related to the common oxidation states of the metals and reflects the metal-halogen bond strength. The molecular ions of the compounds Ti(OEt)_4?nox_n (n = 0, 1 or 2) fragment by loss of intact ligand radicals.     

Synthesis of titanium(iv) 3,6-di-tert-butylcatecholate complexes

Russian Chemical Bulletin - Two synthetic approaches were used for the synthesis of 3,6-di-tert-butylcatecholate derivatives of titanium(iv). These approaches are based on the exchange reaction...     

Complexes of oxovanadium(IV) with cyclic nitrogen-containing ligands

Summary Five complexes were prepared containing VOSO₄ and the ligands 4-aminopyridine (4-APY), 3-aminopyridine (3-APY), 2-aminopyridine (2-APY), 2-aminopyrimidine (2-APYM), and aniline (AN). Complexes of 4-APY and AN did not react with orthophenanthroline (o-phen) and dipyridyl (dipy); the others did react, however, giving similar products. Spectroscopic evidence shows that bonding occurs preferably through an endocyclic nitrogen whenever the ligand possesses more than one type of nitrogen atom.The shift in (VO) upon complexation seems to depend both on the basicity of the ligands as well as on the coordination number of the metal atom. The electronic spectra show two absorptions for the complexes with monodentate ligands and three absorptions for those with bidentate ligands. The former are thought to haveC ₁ symmetry whereas the latter are likely to beC _s species.     

Synthesis,spectroscopic and structural characterisation of vanadium(IV) and oxovanadium(IV) complexes with arsenic donor ligands

The reaction of o-C₆H₄(AsMe₂)₂ with VCl₄ in anhydrous CCl₄ produces orange eight-coordinate [VCl₄{o-C₆H₄(AsMe₂)₂}₂], whilst in CH₂Cl₂ the product is the brown, six-coordinate [VCl₄{o-C₆H₄(AsMe₂)₂}]. In dilute CH₂Cl₂ solution slow decomposition occurs to form the V^III complex [V₂Cl₆{o-C₆H₄(AsMe₂)₂}₂]. Six-coordination is also found in [VCl₄{MeC(CH₂AsMe₂)₃}] and [VCl₄{Et₃As)₂]. Hydrolysis of these complexes occurs readily to form vanadyl (VO²⁺) species, pure samples of which are obtained by reaction of [VOCl₂(thf)₂(H₂O)] with the arsines to form green [VOCl₂{o-C₆H₄(AsMe₂)₂}], [VOCl₂{MeC(CH₂AsMe₂)₃}(H₂O)] and [VOCl₂(Et₃As)₂]. Green [VOCl₂(o-C₆H₄(PMe₂)₂}] is formed from [VOCl₂(thf)₂(H₂O)] and the ligand. The [VOCl₂{o-C₆H₄(PMe₂)₂}] decomposes in thf solution open to air to form the diphosphine dioxide complex [VO{o-C₆H₄(P(O)Me₂)₂}₂(H₂O)]Cl₂, but in contrast, the products formed from similar treatment of [VCl₄{o-C₆H₄(AsMe₂)₂}_x] or [VOCl₂{o-C₆H₄(AsMe₂)₂}] contain the novel arsenic(V) cation [o-C₆H₄(AsMe₂Cl)(μ-O)(AsMe₂)]⁺. X-ray crystal structures are reported for [V₂Cl₆{o-C₆H₄(AsMe₂)₂}₂], [VO(H₂O){o-C₆H₄(P(O)Me₂)₂}₂]Cl₂, [o-C₆H₄(AsMe₂Cl)(μ-O)(AsMe₂)]Cl·[VO(H₂O)₃Cl₂] and powder neutron diffraction data for [VCl₄{o-C₆H₄(AsMe₂)₂}₂].     

Binuclear oxovanadium(IV) complexes of phthalazine hydrazone ligands

Summary The oxovanadium(IV) complexes [(VOSO₄·H₂O)₂L] and [(VO)₂L¹(-SO₄)] (L = hydrazone ligands derived from 1,4-dihydrazinophthalazine and benzaldehyde, 4-chlorobenzaldehyde, 4-methoxybenzaldehyde or acetophenone; L ¹H₂ = hydrazone ligands derived from 1,4-dihydrazinophthalazine and salicylaldehyde, 2-hydroxyacetophenone or 2-hydroxynaphthaldehyde) have been prepared and characterized by elemental analyses, electrical conductance, magnetic moments and spectral data. Reduced magnetic moments are observed for all sulfato-bridged derivatives, indicating antiferromagnetically coupled vanadium(IV) centres. The vanadium(IV) centres appear to have five-coordinated stereochemistries in the systems which involve two metals bound to each ligand. The thermal behaviour of the complexes was investigated by t.g. and d.t.g. techniques. The antifungal and antiviral activities of the hydrazones and their corresponding complexes were also investigated. The screening results have been correlated with the structural features of the tested compounds.     

Ferromagnetic oxovanadium(IV) complexes chelated with tetrahalosalen ligands

Five oxovanadium(IV) complexes [VO(X₄salen)] have been prepared and characterized, where each benzene ring was substituted with two halogen atoms in salen (H₂salen = N,N′-disalicylideneethylenediamine). The X-ray diffraction study on 3,3′,5,5′-tetrachloro-, 3,3′,5,5′-tetrabromo-, and 4,4′,6,6′-tetrachlorosalen derivatives clarified their polymeric structure with the (-VO-)_n repeating unit. The interatomic V···V distances are 3.710(3), 3.695(3), and 3.749(3) Å, respectively, being shorter than that of known [VO(salpn)] (3.83 Å; H₂salpn = N,N′-disalicylidenepropylenediamine). The exchange coupling parameters (J) were determined by fitting the magnetic susceptibility data to the one-dimensional ferromagnetic model, giving 2J/k_B = 8.2-16 K, which are the largest in the [VO(salen)] and [VO(salpn)] family.     

Synthesis and characterization of oxovanadium(IV), vanadium(IV) and oxovanadium(V) complexes of tetradentate Schiff bases. Attempted preparation of vanadium-carbon bonded compounds through desilylation

Condensation of 1,3-diaminopropane-2-ol with diacetylmonoxime, acetylacetone, salicylaldehyde and orthohydroxyacetophenone yielded the tetradentate Schiff bases N,N′-(2-hydroxy)propylenebis{(2-imino-3-oximino)butane} (H₂dampnol), N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (H₂acacpnol), N,N′-(2-hydroxy)propylenebis-(salicyalaldimine) (H₂salpnol) and N,N′-(2-hydroxy)propylenebis(7-methylsalicylaldimine) (H₂ohacpnol), respectively. The ligands form complexes with oxovanadium(IV), vanadium(IV) and oxovanadium(V) salts. Some mixed ligand complexes involving σ-bonded phenyl and benzyl radical along with tetradentate ligand, H₂L (where, H₂L stands for H₂dampnol, H₂acacpnol, H₂salpnol or H₂ohacpnol) of the types [(L)V(C₆H₅)₂]CH₃OH and [(L)V(CH₂Ph)₂]CH₃OH have been synthesized, characterized and also provide the syntheses of some new organovanadium(IV) complexes. Silylation coupled with desilylation have been employed as a route to new organovanadium(IV) complexes. All the complexes have been characterized with the help of elemental analyses, molar conductance values, molecular weights, magnetic moments and spectroscopic (IR, UV-Vis, ESR) data.     

Thermal decomposition of oxovanadium(IV) complexes with substituted pyridines

The kinetics of decomposition of solid complexes of bis(dibenzoylmethanato) oxovanadium(IV) with pyridine and several methyl, dimethyl and aminopyridines has been studied using differential scanning calorimetry. Activation energies have been determined and, in general show an increase with increasing basicity of the ligands. A linear relationship exists between pK_b values of the bases and the temperatures for the decomposition, except for the complexes obtained with 4 aminopyridine and 4 methylpyridine. These complexes are less stable than expected from the basicity of the ligands. These observations are discussed in terms of the nature of the metalligand bond.     

Chromium (III) halide complexes with isoxazole and substituted isoxazoles as ligands

Complexes of chromium (III) with isoxazole, 3,5-dimethylisoxazole, 3-methyl, 5-phenylisoxazole and 3,5-diphenylisoxazole have been prepared and characterized by magnetic and spectroscopic techniques. lie stereochemistries of the complexes are discussed with emphasis on their i.r. spectra. The complexes CrL₃X₃ involve unidentate ligands, are neutral, monomeric and hexacoordinate. The complex [Cr₂(3-Me,5-Phisox)₃Br₆]·6H₂O is a polymeric structure with terminal halides and bridging N- and O-bonded ligands. The ligand field parameters for the complexes have been calculated and compared with similar complexes containing CrO₃X₃ and CrN₃X₃ chromophores.     

Mixed-ligand oxovanadium(V) complexes incorporating bidentate salicylaldehyde and tridentate aldimine ligands

Summary Mixed-ligand oxovanadium(V) complexes, [V^VO(L)-(sal)], containing salicylaldimine ligands of -amino acids H₂L [(1);R = Me, i-Pr and CH₂Ph] and salicylaldehyde (Hsal) have been synthesized. The coordination sphere of the complexes is of the VO(ONO)(OO) type, where O atoms are phenolic, carboxylic and aldehydic, and N is of the azomethine type. The complexes are diamagnetic and exhibit only one LMCT band at ca. 490 nm. They display quasi-reversible one-electron reduction peaks in a CH₂Cl₂-MeCN (21v/v) mixture in the 0.07–0.13V versus s.c.e. range. A trend in the redox potential data has been rationalized on the basis of conventional normal substituent effects.     

Urease inhibition of oxovanadium(V) complexes with hydrazone and hydroxamate ligands

Two new oxovanadium(V) complexes, [VOL¹(SHA)] (I) and [VOL²(BHA)] (II), were prepared by the reaction of [VO(Acac)₂] (Acac = acetylacetonate) with N′-(2-hydroxybenzylidene)isonicotinohydrazide (H₂L¹) and salicylhydroxamic acid (HSHA) and 4-chloro-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H₂L²) and benzohydroxamic acid (HBHA), respectively, in methanol. Crystal and molecular structures of the complexes were determined by elemental analysis, infrared spectra and single crystal X-ray diffraction (CIF file CCDC nos. 978238 (I) and 978392 (II)). The V atoms are in octahedral coordination. Thermal stability and the inhibition of urease of the complexes were studied.     

Nano-sized, ternary oxovanadium(IV) complexes containing electron-rich oxygen-based ligands

Some mononuclear mixed-carboxylato ??-diketonato oxovanadium(IV) complexes of the general formula [VO(??-dike)(RCOO)] (where H??-dike?=?acetylacetone; benzoylacetone or dibenzoylmethane, R?=?C₁₅H₃₁ or C₁₇H₃₅) have been synthesized from VO(acac)₂ by stepwise substitutions of acetylacetonate ion with straight chain fatty acids (RCOOH) and ??-diketones in p-xylene under reflux. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. These were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, ¹H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance values indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of ??-diketonate and carboxylate ligands in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with ⁵¹V nucleus (I?=?7/2). Cyclic voltammograms of all the complexes displayed one-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Powder XRD and transmission electron microscopy (TEM) studies indicated the particles of these were lying in the nano-size range. The synthesized complexes are a new type of mixed-ligand complexes in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes.     

Vanadium(IV) and vanadium(V) complexes of salicyladimine ligands

The synthesis and characterization of a V(IV) and a V(V) complex of the salicyladimine ligand system are described. The reaction of salicylaldehyde and 1,3-diaminohydroxypropane with vanadyl sulfate produced a monomer (VOL1) which, upon heating in methanol, crystallized as a V(V) complex (VO(2)L1). The reaction of 3-methoxysalicylaldehyde, 1,3-diaminohydroxypropane, and vanadyl sulfate resulted in a binuclear complex held together by hydrogen bonding (VOL2). VOL1 was determined to catalyze the epoxidation of cyclohexene better than VOL2. The synthesis and characterization of VOL1, VOL2, and VO(2)L1 are described. The role of each complex as a catalyst for the epoxidation of cyclohexene is investigated. Results indicate that the V(V) complex performs better than either of the V(IV) complexes.     

Dinuclear oxovanadium(IV) thiolate complexes with ferromagnetically coupled interaction between vanadium centers

Two dinuclear oxovanadium(IV) thiolate complexes, [N(C5H11)4]2[VOL1]2 (1) and [N(C4H9)4][(VOL2)2(mu-OCH3)] (2) (where L1 = [(CH3)SiO(C6H4-2-S)2]3- and L2 = [(C6H5)PO(C6H4-2-S)2]2-), have been synthesized and characterized. The geometry of the anion in 1 can be classified to an edge-sharing bi-square-pyramid with a syn-orthogonal configuration. The one in 2 can be view as a face-sharing bioctahedron with two oxo groups in syn positions. Of note, these two complexes display intramolecular ferromagnetic interaction between two metal centers.     

Binary and ternary complexes of oxovanadium(IV) and homobinuclear double-bridged oxovanadium(IV) complexes

Summary Binary and ternary complexes of oxovanadium(IV) with salicylaldehyde and/or 2-hydroxy-1-naphthaldehyde were prepared and additional homobinuclear doublybridged oxovanadium(IV) complexes were obtained from the reaction products ofmeta-orpara-phenylenediamine withortho-hydroxy aromatic aldehydes (bridging Schiff base). The complexes were characterised by elemental analysis, and by spectral and magnetic studies.     

Synthesis and spectroscopic characterization of cationic mononuclear oxovanadium(IV) complexes with tetradentate Schiff bases as ligands

New tetradentate Schiff-base oxovanadium(IV) complexes [VOL']SO4 (where L' = tetradentate ligands derived from 2,4-dihydroxy 5-acetyl acetophenone and substituted diamines) were prepared and characterized by physico-chemical techniques. All the complexes are monomeric in nature and a square-pyramidal geometry is proposed. Various ligand-field and molecular-orbital parameters have been calculated.     

Crystal structures of new isostructural oxovanadium(V) complexes with hydrazone ligands

Two new isostructural methoxide-bridged dimeric oxovanadium(V) complexes [VO(L¹)(OMe)]₂ (1) and [VO(L²)(OMe)]₂ (2), where L¹ and L² are the deprotonated forms of 3-bromo-N′-[1-(2-hydroxyphenyl)×ethylidene]benzohydrazide (H₂L¹) and 3-chloro-N′-[1-(2-hydroxyphenyl)ethylidene]benzohydrazide (H₂L²) respectively, are synthesized and characterized by elemental analyses, IR spectra, and single crystal X-ray determination. Both crystals crystallize in the triclinic space group P-1. For 1, a = 7.5237(15) Å, b = 10.846(3) Å, c = 11.195(3) Å, α = 84.143(3)°, β = 72.244(3)°, γ = 77.869(3)°, V = 849.9(4) ų, Z = 1, R ₁ = 0.0634, wR ₂ = 0.1373. For 2, a = 7.493(2) Å, b = 10.740(3) Å, c = 11.109(3) Å, α = 84.569(2)°, β = 71.783(2)°, γ = 79.822(2)°, V = 835.0(4) ų, Z = 1, R ₁ = 0.0511, wR ₂ = 0.1076. Each V atom in the complexes is octahedrally coordinated.     

Vanadium (III), oxovanadium (IV) and oxovanadium (V) trifluoro-methanesulfonates

V(SO₃CF₃)₃, VO(SO₃CF₃)₂ and VO(SO₃CF₃)₃ have been prepared by reacting V(O₂CCF₃)₃, VO(O₂CCF₃)₂ and VOC1₃ with HSO₃CF₃. The i.r. data suggest a bridging bidentate nature for SO₃CF₃ groups. The diffuse reflectance spectrum of V(SO₃CF₃)₃ suggests hexacoordination of vanadium, whilst that of VO(SO₃CF₃)₂ is comparable to either five or six coordinated oxovanadium (IV) systems. The magnetic moments of V(SO₃CF₃)₃ and VO(SO₃CF₃)₂ are slightly lower than the spin-only values. Thermal decomposition of these triflates is simple. All the three triflates form coordination complexes with pyridine, 2, 2′-bipyridyl and triphenylphosphine oxide.