Structures,DNA binding,DNA cleavage,and antitumor investigations of a series of molybdenum(VI) complexes with some N(4) methyl and ethyl thiosemicarbazone ligands

Four dioxomolybdenum(VI) complexes were synthesized by reaction of [MoO₂(acac)₂] with thiosemicarbazones derived from 5-allyl-2-hydroxy-3-methoxybenzaldehyde (1), 2-hydroxynaphthaldehyde (2), 2,3-dihydroxybenzaldehyde (3), or 5-tert-butyl-2-hydroxybenzaldehyde (4). The ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography showed that the distorted octahedral coordination of molybdenum is completed by methanol (D) in 1a, 3a, and 4a or H₂O in 2a. The molecular structures of 1, 3, and 4, and the complexes were determined by single-crystal X-ray crystallography. Binding of the ligand and complexes with calf thymus DNA were investigated by UV, fluorescence titrations, and viscosity measurements. Gel electrophoresis revealed that all the complexes can cleave pBR322 plasmid DNA. The cytotoxic properties of the complexes against human colorectal (HCT 116) cell line showed strong antiproliferative activities in relative order 4a?>?3a?>?1a?>?2a with IC₅₀ values of 1.6, 4.0, 4.8, and 6.7?μM, respectively. The complexes exhibited more activity than the standard reference drug, 5-fluorouracil (IC₅₀ 7.3?μM). These studies show that dioxomolybdenum(VI) complexes have potential use in chemotherapy.     

Synthesis and structures of silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)2Mo(CH2EMe3)2 (E = Si, Ge, Sn)

New silicon-, germanium-, and tin-containing imido-alkyl molybdenum complexes (ArN)₂Mo(CH₂EMe₃)₂ (Ar is 2,6-diisopropylphenyl; E = Si (1), Ge (2), Sn (3)) were prepared in the crystalline state in 58–66% yields by the reactions of the (ArN)₂MoCl₂(DME) complex with alkyllithium derivatives Me₃ECH₂Li (E = Si or Ge) or the Grignard reagents Me₃ECH₂MgCl (E = Ge or Sn). The structures of complexes 1–3 and the known analog (ArN)₂Mo(CH₂Bu^t)₂ (4) were established by X-ray diffraction analysis. Complexes 1–3 were found to be isostructural. The coordination environment about the Mo atom can be described as a distorted tetrahedron. Complex 4 has a similar structure. The Mo-C distance tends to decrease with increasing electron donating ability of the EMe₃ group.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 597–600, March, 2005.     

1,3-Dipolar cycloaddition of diazomethane and diazocyclopropane to 2-fluoro-3-methylbutadiene and thermal transformations of fluorine-containing vinylpyrazolines and vinylcyclopropanes

Reactions of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15 °C and with diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K₂CO₃ in CH₂Cl₂ at –10 °C selectively involve the double bond at the methyl group to give 3-(1-fluorovinyl)-3-methylpyrazolines. Thermal dediazotization of the latter at 250 °C yields 1-(1-fluorovinyl)-1-methylcyclopropane and -spiropentane 5, which are capable of isomerizing, under more severe conditions (400—600 °C), into 1-fluoro-2-methylcyclopent-1-ene and 5-fluoro-4-methylspiro[2.4]hept-4-ene (7), respectively. Spiropentane derivative 5 partially isomerizes into 1-fluoro-2-methyl-3-methylidenecyclohex-1-ene. In a similar way, thermolysis of 6-(2,3,3-trifluorocyclobut-1-enyl)-4,5-diazaspiro[2.4]hept-4-ene at 400 °C gives a mixture of 1-(spiropentyl)-2,3,3-trifluorocyclobut-1-ene and 2,3,3-trifluoro-1-(2-methylidenecyclobutyl)cyclobut-1-ene. Thermolysis of 1-cyclopropyl-2,3,3-trifluorocyclobut-1-ene at 550—620 °C affords a mixture of 1-(trifluorovinyl)cyclopentene and 2,3-difluorotoluene.     

Reactivity of [Mo(NHNRPh)(NNRPh)(acac)X2] (R=Ph,Me; X=Br,I) toward tertiary phosphines

The reactivity of mixed [organohydrazido(1-)][organohydrazido(2-)]molybdenum(VI) complexes [Mo(NHNRPh)(NNRPh)(acac)X₂] {R?=?Ph, X?=?Br (1); R?=?Ph, X?=?I (2) and R?=?Me; X?=?I (3)} with tertiary phosphines as PPh₃, PMePh₂ and PMe₂Ph are examined. The syntheses of [Mo(NNPh₂)₂Br₂(PPh₃)] (4), [Mo(NNPh₂)₂Br₂(PMePh₂)₂] (5), [Mo(NNPh₂)₂Br₂(PMe₂Ph)₂] (6), [Mo(NNPh₂)₂(acac)I(PPh₃)] (7), [Mo(NNPh₂)₂(acac)(PMePh₂)₂]⁺I^? (8) and [Mo(NNMePh)₂(acac)(PMePh₂)₂]⁺I^? (9) are reported. All complexes were characterized by elemental analysis, UV-visible, IR, ¹H and ³¹P{H} NMR spectroscopy.     

121,123Sb NQR investigation of chlorofluoroantimonates(III) M2SbCl3F2 (M = Rb. Cs,and NH4)

Antimony(m) chlorofluoride complexes M₂SbCl₃F₂ (M = Rb, Cs, or NH₄) were studied by the^121,123Sb NQR method. A temperature range (77–285 K) with anomalous change in the NQR parameters and a second-order phase transition at 250–280 K for (NH₄)₂SbCl₃F₂ were found.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 382–385, February, 1996     

Synthesis,structural characterization and catalytic potential of oxidovanadium(IV) and dioxidovanadium(V) complexes with thiazole-derived NNN-donor ligand

Reaction between the tridentate NNN donor ligand, (E)-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)benzo[d]thiazole (HL), and V₂O₅ in ethanol gave a new vanadium(V) complex, [VO₂L] (1), while the similar reaction by using [V^IVO(acac)₂] as the metal source gave two different types of crystals related to compounds [VO₂L] (1) and [V^IVO(acac)L] (2). The molecular structures of the complexes were determined by single-crystal X-ray diffraction and spectroscopic characterization was carried out by means of FT-IR, UV–vis and NMR experiments as well as elemental analysis. The oxidovanadium(IV) and dioxidovanadium(V) species were used as catalyst precursors for olefin oxidation in the presence of hydrogen peroxide (H₂O₂) as an oxidant. Under similar experimental conditions, the presence of 1 resulted in higher oxidation conversion than 2.     

Gold(III)pentafluorophenylarylazoimidazole: Synthesis and spectral (H, C, COSY, HMQC NMR) characterisation

Reaction of [Au^III(C₆F₅)₃(tht)] with RaaiR′ in dichloromethane medium leads to [Au^III(C₆F₅)₃ (RaaiR′)] [RaaiR′=p-R-C₆H₄-N=N-C₃H₂-NN-l-R′, (1-3), R = H (a), Me (b), Cl (c) and R′= Me (1), CH₂CH₃ (2), CH₂Ph (3), tht is tetrahydrothiophen]. The nine new complexes are characterised by ES/MS as well as FAB, IR and multinuclear NMR (¹H,¹³C,¹⁹F) spectroscopic studies. In addition to dimensional NMR studies as¹H,¹H COSY and¹H¹³C HMQC permit complete assignment of the complexes in the solution phase.     

Gas phase and solution state stability of complexes L…M, where M = Cu, Ni, or Zn and L = R−C(O)NHOH (R = H, NH2, CH3, CF3, or Phenyl)

The structure and gas-phase metal affinities (M = Cu²⁺, Ni²⁺, and Zn²⁺) of formohydroxamic acid derivatives R–C(O)NHOH (R = H, NH₂, CH₃, CF₃ and Phenyl) were studied using the B3LYP/6-311+G(d,p) method of DFT theory. In order to evaluate the conformational behavior of these systems in water, we carried out CPCM-SCRF optimization calculations at the B3LYP/6-311+G(d,p) levels of theory. The obtained optimized geometries and interaction affinities of the gas and solution phase were compared. The following order of stability was found for ionic complexes of the transition metals: Cu²⁺ > Ni(t)²⁺ > Zn²⁺. The same stability order would be expected according to the Irving–Williams order of stability constants. The high-spin complexes of the Ni²⁺ were more stable than the low-spin complexes. The solvent effect reduced the observed relative stability of individual metallic complexes of substituted hydroxamic acids.     

Reactions of germanium(II), tin(II), and antimony(III) chlorides with acenaphthene-1,2-diimines

Reactions of diimines dtb-BIAN and dph-BIAN with GeCl₂ afford germanium(II) complexes with radical-anionic ligands, (dtb-BIAN)GeCl (5) and (dph-BIAN)GeCl (6a), respectively, where dtb-BIAN is 1,2-bis[(2,5-di-tert-butylphenyl)imino]acenaphthene and dph-BIAN is 1,2-bis[(2-biphenyl)imino]acenaphthene. The latter reaction gives 6a along with [(dph-BIAN)GeCl]⁺[GeCl₃]⁻ (6b). The reactions of tin(II) and antimony(III) chlorides with dtb-BIAN and dpp-BIAN produce complexes of these halides with neutral coordinated diimines, viz., (dtb-BIAN)SnCl₂ (7) and (dpp-BIAN)SbCl₃ (8) (dpp-BIAN is 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene). Paramagnetic complexes 5 and 6a were studied by ESR spectroscopy. Diamagnetic compounds 7 and 8 were characterized by ¹H NMR spectroscopy. The structures of complexes 5, 6a,b, 7, 8, and (dpp-BIAN)Ge (9) were established by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 71–80, January, 2006.     

Synthesis,structure, and reactivity of siloxides and germyloxides of iron(ii) and cobalt(ii)

Iron and cobalt siloxides and germyloxides [(Me₃Si)₃SiO]₂M (M = Fe (1), Co (2)), (Me₅Si₂O)₂Fe (3), (Prⁱ ₃SiO)₂M (M = Fe (4), Co (5)), (Prⁱ ₃GeO)₂Fe (6), (Ph₃SiO)₂Fe (7), (Me₃SiO)₂Fe (8), (Prⁱ ₃GeO)₂Fe(bpy) (9), and [(Me₃Si)₂NFe(-OSi₂Me₅)₂]₂Fe·C₆H₆ (10) were synthesized by the reactions of metal silylamides [(Me₃Si)₂N]₂M (M = Fe, Co) with the corresponding silanols or triisopropylgermanol. The reaction of pentamethyldisilanol with iron(ii) silylamide affords either polymeric complex 3 or coordination oligomer 10, depending on the ratio of the reactants. The structures of complexes 9 and 10 were established by X-ray diffraction analysis. The interaction of the prepared compounds with carbon oxides was studied. Low-coordination cobalt siloxide is the only among all prepared compounds that absorbs CO (2 mol) at room temperature and under 1 atm to form an unstable cluster. Compounds 1, 2, and 4—8 react with CO₂ to form carbonate complexes, and their reactivity decreases with a decrease in the electron-donating ability of the substituents at the central atom: (Me₃Si)₃SiO > Prⁱ ₃GeO Prⁱ ₃SiO > Me₃SiO Ph₃SiO.     

Synthesis,structure and spectral studies on mixed ligand copper(II) complexes of diimines and acetylacetonate

Two new mixed ligand complexes of copper(II) with acetylacetonate (acac), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) belonging to the class of cytotoxic and antineoplastic compounds known as CASIOPEINAS^® were synthesized and structurally characterized. Crystals of both complexes [Cu(acac)(bpy)(H₂O)]NO₃ · H₂O (1), [Cu(acac)(phen)Br] (2) contain square pyramidal Cu(II) complex species. In frozen solution both compounds give well resolved EPR spectra with very similar parameters.     

Reactions between germylenes (silylenes) and phosphaalkenes: an experimental and theoretical study. Preparation of the first representative of germaphosphacyclopropanes

Reactions of a number of germylenes and dimethylsilylene with a phosphaalkene, 2,2-bis(trimethylsilyl)-1-phenyl-1-phosphaethene (1), were studied. The reaction of short-lived dimethylgermylene with 1 produced a phosphagermirane 3 (the first representative of a new class of heterocyclic compounds). Compound 3 was characterized in solution by ¹H, ¹³C, ³¹P, and ²⁹Si NMR spectroscopy. Subsequent reaction of 3 with dimethylgermylene results in 2,2,3,3-tetramethyl-4,4-bis(trimethylsilyl)-1-phenyl-2,3-digerma-1-phosphacyclobutane 4, which has not been reported so far. In order to rationalize different reactivities of germylenes towards alkenes and phosphaalkenes, the addition products of GeH₂ to ethylene and phosphaethene (HP=CH₂) were studied using the G2 computational scheme and DFT PBE technique. The adducts of GeMe₂ (GeCl₂) with HP=CH₂ and of GeMe₂ with PhP=C(SiH₃)₂ were also calculated by the DFT PBE method. According to calculations, the exothermicity, DE, of cycloaddition of GeH₂ and GeMe₂ to the phosphaalkenes HP=CH₂ and PhP=C(SiH₃)₂ (43.5—39.7 kcal mol^–1) is nearly twice as high as the exothermicity of cycloaddition of these germylenes to ethylene. In addition to the minimum corresponding to the three-membered cycle, a number of minima corresponding to quite stable donor-acceptor complexes in which the Ge atom is coordinated by the lone electron pair of the P atom in the phosphaalkene molecule were located on the potential energy surface of the germylene—phosphaalkene system. The complexation energy of the complex of GeH₂ (GeMe₂) with phosphaethene is 25.0 (16.9) kcal mol^–1. For GeCl₂, the exothermicity of cycloaddition to HP=CH₂ decreases to 7.6 kcal mol^–1 and the complexation energy decreases to 8.2 kcal mol^–1.     

Synthesis,structural characterization,and thermal properties of monomeric (Mn,Co, Ni,and Zn) and polymeric (Cd) complexes of thiocyanates with benzyl carbazate as an ancillary ligand

Abstract

Five complexes [M(NCS)₂(bc)₂] M?=?Mn (1), Co (2), Ni (3), Zn (4), and [Cd(NCS)₂(bc)]_n (5), (bc) = benzyl carbazate (benzyl hydrazinecarboxylate), have been synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of all five complexes have been confirmed by X-ray structural analysis. These results confirm that 1–4 are isotypes, and all four are centrosymmetric, with two mutually trans N,O chelating (bc) ligands in equatorial positions and a pair of trans-thiocyanate anions in the axial positions. The cadmium complex (5) is a coordination polymer. The asymmetric unit contains a square planar CdN₂OS core, in which the (bc) ligand adopts an N, O bidentate coordination mode together with N and S bound thiocyanato anions. Polymer expansion increases the coordination number to six with the N and S bound thiocyanate ligands linking two adjacent complexes. This expansion results in double layers of cadmium octahedra propagating along the c axis direction. The thermal analyses of these compounds show endothermic decomposition processes to give respective metal thiocyanates as intermediates. For the Mn, Co, Ni, and Zn compounds these intermediates decompose exothermically to form metal oxides, whereas the Cd complex forms cadmium sulfide as the end product.     

Preparation and Characterization of SiO2-MxOy(M = V, Sn, Sb) Thin Films from Silicic Acid and Metal Chlorides

The preparation of SiO₂-M _x O _y (M = V, Sn, Sb) binary oxide thin films by sol-gel method was investigated. The reaction of silicic acid with metal chloride (M = Sn and Sb) or oxychloride (M = V) formed homogeneous solutions. The dip-coating of slide glass and silicon wafer followed by heat treatment gave oxide films having Si—O—M bond. The changes of FT-IR spectra as a function of heat treatment temperature and molar composition confirmed the Si—O—M bonds. The sheet resistance of films increased with an increase on heat treatment temperature and decrease in the content of metal oxide M _x O _y . X-ray diffraction peaks were observed for the SiO₂-V₂O₅ films with high V₂O₅ contents and heat-treated above 250°C, while the others were amorphous. Oxide films heat treated at 500°C had a thickness between 340–470 nm.     

Synthesis,crystal structures,and biological activity of oxovanadium(V) complexes with similar tridentate hydrazone ligands

Two new oxovanadium(V) complexes, [VOL¹(OEt)(EtOH)] (1) and [VOL²(OMe)(MeOH)] (2), were prepared by reaction of [VO(acac)₂] (where acac?=?acetylacetonate) with N′-(3-bromo-2-hydroxybenzylidene)-4-methylbenzohydrazide (H₂L¹) in ethanol and N′-(3-bromo-2-hydroxybenzylidene)-4-methoxybenzohydrazide (H₂L²) in methanol, respectively. Crystal and molecular structures of the complexes were determined by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. The V ions have octahedral coordination. Thermal stability and the inhibition of urease of the complexes were studied.     

Synthesis and structure of N-salicylidene-o-aminophenolato gallium(III) complexes

The reactions of Ga(acac)₃ with N-salicylidene-o-aminophenol (saphH₂) and its 5-methyl (5MesaphH₂) and 5-bromo (5BrsaphH₂) derivatives in alcohols afforded the complexes [Ga(acac)(saph)(EtOH)] (1), [Ga(acac)(5Mesaph)(MeOH)] (2) and [Ga(acac)(5Brsaph)(EtOH)] (3), respectively, in good yields. The crystal structures of 1 and 2 have been solved by single-crystal X-ray crystallography. All three complexes are mononuclear with the Ga^III atoms being surrounded by a dianionic tridentate Schiff base ligand, one bidentate acac⁻ ligand and a terminal alcohol molecule. Characteristic IR data are discussed in terms of the nature of bonding and the structures of the three complexes.     

Synthesis and structures of the dinuclear tin(II) complexes [R = Ph, X(Z) = CPh; R = SiMe3, X(Z) = PPh2] and of related compounds

Tin(II) compounds containing the ligands [CH(C₆H₃Me₂-2,5)C(Bu^t)NSiMe₃]⁻ (≡ L¹), [CH(Ph)C(Ph)NSiMe₃]⁻ (≡L²), [CH(SiMe₃)P(Ph)₂NSiMe₃]⁻ (≡ L³),

Full-size image (3K)

(≡ L⁴), [C(Ph)C(Ph)NSiMe₃]²⁻ (≡ L⁵), and [C(SiMe₃)P(Ph)₂NSiMe₃]²⁻ (≡ L⁶) are reported: the transient SnBr(L¹) (1) and SnBr(L²) (2), Sn(L¹)₂ (3) [P.B. Hitchcock, J. Hu, M.F. Lappert, M. Layh, J.R. Severn, J. Chem. Soc., Chem. Commun. (1997) 1189], the labile Sn(L²)₂ (4), [Sn(L⁵)]₂ (5), SnCl(L³) (6), Sn(L³)₂ (7), [Sn(L⁶)]₂ (8), Sn(L⁴)₂ (9) and Pb(L⁴)₂ (10). They were prepared from (i) SnBr₂ and K(L¹) (1, 3) or K(L²) (2, 4, 5); (ii) SnCl₂ and Li(L³) (6–9); or (iii) PbCl₂ and Li(L⁴) (10). Each of 1, 3 and 5–10 has been characterised by multinuclear NMR spectra; 3, 5, 6, 8, 9 and 10 by EI-mass spectra, but only 3, 5, 8, 9 and 10 were isolated pure and furnished X-ray quality crystals. Of greatest novelty are the title binuclear fused tricyclic ladder-like compounds 5 and 8. Quantum chemical calculations, on alternative pathways to 5 from 2 and to 8 from 7, are reported.     

Thermal properties of [MII(phen)3]2V4O12·phen·22H2O (M II=Co,Ni, Cu,phen=1,10-phenanthroline)

Thermal decomposition of three tetravanadates, [M^II(phen)₃]₂V₄O₁₂·phen·22H₂O, where M ^II is Co (1), Ni (2), Cu (3) and phen is 1,10-phenanthroline, was studied by dynamic method (for 1 and 2) or isothermally (for 3). The thermal decomposition of the studied compounds is a multi-step process which involve: discontinuous dehydration, release of uncoordinated, and of coordinated phenanthroline molecules. In course of the latter process, a phase transition of the cyclo-tetravanadates to polymeric metavanadates occurred. Metavanadates with chain structure of the anion were the final decomposition products of all tetravanadates studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

[Cu(X-salicylato)2(N,N-diethylnicotinamide)2(H2O)2] complexes: conformational polymorphism and its consequence in supramolecular hydrogen-bonding networks formation

Novel copper(II) X-salicylate complexes with N,N-diethylnicotinamide (dena) of the formula [Cu(RCOO)₂(dena)₂(H₂O)₂] (RCOO = 3-methylsalicylate anion (3-Mesal, 1), 4-methylsalicylate anion (4-Mesal, 2), 5-methylsalicylate anion (5-Mesal, 3), 5-methoxysalicylate anion (5-MeOsal, 4) or 4-methoxysalicylate anion (4-MeOsal, 5)), and complex [Cu(3-MeOsal)₂(dena)₂(H₂O)₂]∙2H₂O (3-MeOsal = 3-methoxysalicylate anion (6)) have been prepared in the crystalline forms and characterized by spectroscopic methods (IR, Vis–UV, EPR). All the compounds according to their composition (1–5) seem to possess octahedral copper(II) stereochemistry. The complex 1 has been prepared in two different forms. X-ray analyses of the complexes 1, 4, and 5 were carried out and they featured a tetragonal-bipyramidal geometry around the copper atoms. The tetragonal planes are created by X-salicylate anions bonded to the copper(II) atoms via unidentate carboxylate oxygen atoms and the pyridine ring nitrogen atoms of the neutral ligand N,N-diethylnicotinamide, while in axial positions are water molecules. The two forms of complex 1 present conformation polymorphs and supramolecular isomers.     

Analytical and thermal investigations of new solid Y(III) and La(III) complexes

New compounds with formulae Y(2,4′-bpy)_1.5Cl₃·8H₂O (I), Y(2,4′-bpy)_0.5Br₃·8H₂O (II), La(2,4′-bpy)Cl₃·5H₂O (III) and La(2,4′-bpy)_1.5Br₃·5H₂O (IV) were prepared and characterized by chemical and elemental analysis, IR spectroscopy and powder X-ray diffraction. The thermal properties of compounds in the solid state were studied using TG-DTA techniques under dry air atmosphere. The thermal behavior of investigated compounds was studied in the temperature range 298–1273 K. They are stable up to 323 K. The complexes decompose in several stages, accompanied by endo- and exothermic effects. In all cases, the first step of pyrolysis is partial or total dehydration. When the temperature rises, deamination takes place. The solid final products of decomposition are Y₂O₃ and La₂O₃, respectively. Additionally, for all complexes mass spectrometry was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis under dry air atmosphere.