Magnetic double resonance studies of trimethyltin chalcogenides

NMR parameters for bis(trimethyltin) oxide, sulphide, selenide and telluride have been measured by ¹H{¹³C}, ¹H{⁷⁷Se}, ¹H{¹¹⁹Sn}, ¹H{¹²⁵Te}, and ¹H{¹¹⁷Sn} double resonance. Theories of ¹¹⁹Sn magnetic shielding and one-bond coupling constants are summarised and discussed in terms of the measured parameters. It is concluded that theoretical approximate expressions often used to estimate these parameters are inadequate when the tin atom is bound to selenium or tellurium.     

Ligand isotope studies of Zeise's salt derivatives (and their CO analogues)with some aza-heterocycles and their N-oxides. I: Full infrared spectral assignments (4000-50 cm−1)

Detailed infrared assignments (4000-50 cm⁻¹) are made of 41 π-acid complexes of the type cis-[Pt(bipyO₂H)(A)X₂]X and trans-[PtL(A)X₂] (A = C₂H₄, CO; X = Cl, Br; L = pyridazine {pdz}, pyrazine N-oxide {pzO}, quinoline {quin}, quinoline N-oxide {quinO}, 2,2′-bipyridine {bipy}, 1,10-phenanthroline {phen}) and their deuterated L and C₂D₄ analogues. Slight coupling between νPt-C₂ or νPt-CO and νPt-L is observed for some complexes. The question of the uncertainty in the assignments of νPt-O (aromatic N-oxides) is raised, and strong coupling between νPt-N (aza-nitrogen) and νPt-Br is demonstrated.     

Ligand isotope studies of Zeise's salt derivatives (and their CO analogues) with some aza-heterocycles and their N-oxides. II : Their preparation,characterisation, and use in developing 1H nmr and infrared spectra as a diagnostic tool

Forty-one π-acid complexes of the type cis-[Pt(bipyO₂H)(A)X₂]X and trans-[PtL(A)X₂] (A = C₂H₄, CO; X = Cl, Br; L = pyridazine {pdz}, pyrazine N-oxide {pzO}, quinoline {quin}, quinoline N-oxide {quinO}, 2,2′-bipyridine {bipy}, 1,10-phenanthroline {phen}) and their deuterated L and C₂D₄ analogues have been characterised employing infrared and ¹H nmr spectroscopy. The employment of v₁₂ (CH₂ scissors ∼1460 cm⁻¹) of η²-ethene as a diagnostic probe in distinguishing between 4- and 5-coordination is proposed, while the summed percentage decrease of v₂+v₃ (vC=C/δCH₂) may be used to distinguish between N- and O-coordination. The use of chemical shifts (¹H nmr spectroscopy) is confirmed as a suitable means to distinguish between 4- and 5-coordination and is also shown to be suitable for distinction between N- and O-coordination in four coordinate Pt(II) η²-ethene complexes. In contradiction of previous reports, it is found that J_Pt-H cannot be employed to determine the coordination number.     

Preparation and structural studies on dibutyltin(IV) complexes with pyridine mono- and dicarboxylic acids

A number of organotin(IV) complexes with pyridine mono- and dicarboxylic acids (containing ligating -COOH group(s) and aromatic {N} atoms) were prepared in the solid state. The bonding sites of the ligands were determined by means of FT-IR spectroscopic measurements. It was found that in most cases the -COO⁻ groups form bridges between two central {Sn} atoms, thereby leading to polymeric (oligomeric) complexes. On this basis, the experimental ¹¹⁹Sn Mössbauer spectroscopic data were treated with partial quadrupole splitting approximations. The calculations predicted the existence of complexes with octahedral (oh) and trigonal-bipyramidal (tbp) structures, but the formation of complexes with pentagonal-bipyramidal (pbp) structures could not be ruled out. Single-crystals of 2-picolinic and pyridine-2,6-dicarboxylic acid Bu₂Sn(IV)²⁺ complexes were obtained. The X-ray diffraction studies revealed that the central {Sn} atoms are in a pbp environment with bond distances characteristic of organotin(IV) compounds. The two butyl groups are located in axial positions. ¹¹⁹Sn NMR measurements in dmso solution and in the solid state indicated that the polymeric structures of the complexes are not retained in solution. The results of the solid-state ¹¹⁹Sn NMR measurements for compounds 1a, 2a and 6a are in agreement with the structures predicted by Mössbauer spectroscopy and revealed by X-ray diffraction.     

Synthesis and Characterization of trans‐PdII Trimethylsilylchalcogenolates

The trans‐bis(trimethylsilyl)chalcogenolate palladium complexes, trans‐[Pd(ESiMe₃)₂(PnBu₃)₂] [E = S ( 1 ) and Se ( 2 )] were synthesized in good yields and high purity by reacting trans‐[PdCl₂(PBu₃)₂] with LiESiMe₃ (E = S, Se), respectively. These complexes were characterized by ¹H, ¹³C{¹H}, ³¹P{¹H} (and ⁷⁷Se{¹H}) NMR spectroscopy and single‐crystal X‐ray analysis. The reaction of 2 with propionyl chloride led to the formation of trans‐[Pd(SeC(O)CH₂CH₃)₂(PnBu₃)₂] ( 3 ), a trans‐bis(selenocarboxylato) palladium complex and thus established a new method for the formation of this type of complex. Complex 3 was characterized by ¹H, ¹³C{¹H}, ³¹P{¹H} and ⁷⁷Se{¹H} NMR spectroscopy and a single‐crystal X‐ray structure analysis.     

Synthesis,characterization, biological activity,and corrosion inhibition in acid medium of unsymmetrical tetradentate N2O2 Schiff base complexes

Four divalent metal(II) complexes, namely [Co(II)L(H₂O)Cl]·2H₂O, [Ni(II)L(H₂O)Cl]·4H₂O, [Cu(II)L(H₂O)Cl]·3H₂O, and [Zn(II)L(H₂O)Cl]·5H₂O, {L = 2‐furan‐2‐ylmethyleneamino‐phenyl‐iminomethylphenol}, were synthesized and characterized by several techniques. The molar conductance measurement of all analyzed complexes in DMSO showed their non‐electrolytic nature. The new Schiff base ligand (HL) acts as tetradentate ligand, coordinated through deprotonated phenolic oxygen, furan ring oxygen, and two azomethine nitrogen atoms. The ligand field parameters were measured for the metal complexes, which were found to be in the range notified for an octahedral structure. The molecular structural parameters of the synthesized HL ligand and its related metal(II) complexes were calculated and correlated with the experimental parameters such as infrared (IR) data. The investigated ligand and metal complexes were screened for their in vitro antimicrobial activities against different types of fungal and bacterial strains. The resulting data confirmed the examined compounds as a highly promising bactericides and fungicides. The antitumor activities of all inspected compounds were evaluated against colon carcinoma (HCT‐116) and mouse myelogenous leukemia carcinoma (M‐NFS‐60) cell lines. The inhibition effect of HL ligand and its isolated complexes on the corrosion carbon in the form of a rod of area 0.35 cm² in HCl was investigated by measuring the weight loss at 25 °C.     

Reactions of coordinated molecules: XLIX. Carboncarbond bond formation between the donor atoms of adjacent acyl and alkenyl ligands

When the ferraenolate anion, (η-C₅H₅)(CO)₂FeC(O)CH₂⁻, is treated sequentially with methyllithium/TMEDA and benzoyl chloride, the known η³-allyl complex, (η-C₅H₅)(OC)Fe{η³-CH₂C[OC(O)Ph]C[OC(O)Ph](CH₃}, is isolated in 36% yield. When the neutral alkenyl complexes, (η-C₅H₅)(CO)₂Fe[C(Me)CH₂] and (η-C₅H₅)(OC)₂Fe{C(OMe)CH₂], were treated sequentially with methyllithium and benzoyl chloride, the η³-allyl complexes, (η-C₅H₅)(OC)Fe{η³-CH₂C(Me)C[OC(O)Ph](Me) and (η-C₅H₅)(OC)Fe{η³-CH₂C(OMe)C[OC(O)Ph](Me) are isolated in 8 and 11% yield, respectively. These η³-allyl ligands are presumably formed via CC coupling of the donor atoms of the formal acyl and alkenyl ligands in the intermediate complexes.     

Synthesis and reactivity of new methylallylpalladium(II) complexes with bidentate 2-(methylthio-N-benzylidene)anilines

This work describes the synthesis, characterisation and reactivity of new methylallyl Pd(II) complexes that contain bidentate 2-(methylthio-N-benzylidene)anilines as ligands. The reaction of the binuclear complex [(η³-Me-allyl)Pd(μ-Cl)₂] with AgBF₄ causes the total abstraction of the chloride bridges, with the subsequent formation of an intermediary fragment of Pd(II). This fragment in turn reacts with neutral bidentate 2-(methylthio-N-benzylidene)anilines to give cationic complexes of Pd(II) of general formula [(η³-Me-allyl)Pd(η²-S,N-MeSC₆H₄NCHC₆H₄(X)Y)]BF₄ [X=H, Y=H (1); X=F, Y=H (2); X=Me, Y=H (3); X=H, Y=Cl (4); X=H, Y=Me₂N (5); X=H, Y=NO₂ (6)]. The new complexes were characterised by means of elemental analysis, IR, NMR [¹H, ¹⁹F{¹H}, ¹³C{¹H}, ³¹P{¹H}, Dept, ¹H-¹H-COSY, HSQC, HMBC] and mass spectroscopies. The reaction of the Pd(II) complexes with nucleophiles such as NaI, (EtO)₂PS₂K, KCN, KSCN or NaH lead to the deco-ordination of the bidentate ligands to give dimeric or polymeric complexes of Pd(II). The reactivity pattern observed is discussed by a theoretical analysis based on Fukui functions.     

Coordination behavior of the carboxylate group in organotin(IV) derivatives of 2-[(2′,4′,6′-tribromophenylamido)]benzoic acid and 3-[(2′,4′,6′-tribromophenylamido)]propenoic acid: Spectroscopic studies

The complexes of two organic carboxylates (containing {O,O}-donor atoms) with Me₂Sn^(IV)Cl₂, n-Bu₂Sn^(IV)Cl₂, Bz₂Sn^(IV)Cl₂, Oct₂Sn^(IV)O, Me₃Sn^(IV)Cl, n-Bu₃Sn^(IV)Cl, Ph₃Sn^(IV)Cl, Ph₃Sn^(IV)Cl, and Bz₃Sn^(IV)Cl having ligand-to-metal ratios of 1: 2 and 1: 1 were prepared by two different methods. The FT-IR spectra clearly demonstrated that organotin(IV) moieties react with {O,O}-atoms of the ligands. It was found that in all cases the COO⁻ group was acting as bidentate in the solid state. The ¹¹⁹Sn NMR data revealed that the organotin(IV) moiety has a tetrahedral geometry in non-coordinating solvents. The biological activity of these compounds was compared with that of their precursors, and all the synthesized compounds show significant antibacterial activity. The antifungal activity of the complexes against six plant pathogens has been estimated. The complexes display marked toxicity against these fungi and are more fungitoxic than free acids. The compounds have also shown significant cytotoxicity against Brine Shrimp (Artemia salina). The article was submitted by the authors in English.     

Kinetic isotope effects for oxidation reaction of olefins by p-quinones in water-acetonitrile solutions of cationic and chloride anionic palladium complexes

Kinetic isotope effects for oxidation reactions of ethylene and cyclohexene in solutions of cationic palladium(ii) complexes in MeCN-H₂O(D₂O) systems, were measured. It was established that the ratio of the initial reaction rates ${{R_0^{H_2 O} } \mathord{\left/ {\vphantom {{R_0^{H_2 O} } {R_0^{D_2 O} }}} \right. \kern-0em} {R_0^{D_2 O} }} $ is equal to 1 for both reactions with the use of cationic complexes of the type Pd(MeCN) _x (H₂O)_4?x ²⁺, which differs from oxidation reactions catalyzed by chloride palladium complexes in the same solutions, where the ratio ${{R_0^{H_2 O} } \mathord{\left/ {\vphantom {{R_0^{H_2 O} } {R_0^{D_2 O} }}} \right. \kern-0em} {R_0^{D_2 O} }} $ = 5.0±0.16 and 4.73±0.14 at H⁺ molar fraction of 0.48 and 0.16, respectively (H⁺ molar fraction was calculated based on the sum of [H⁺] and [D⁺]).     

Mono- and dinuclear Zn(II) complexes of Schiff-base ligands: syntheses,characterization and studies of photoluminescence

Six Schiff-bases HL¹-HL⁴, L⁵ and L⁶ [HL¹ = 2,6-bis[1-(2-aminoethyl)pyrolidine-iminomethyl]-4-methyl-phenol, HL² = 2,6-bis[1-(2-aminoethyl)piperidine-iminomethyl]-4-methyl-phenol, HL³ = N-{1-(2-aminoethyl)pyrolidine}salicylideneimine, HL⁴ = N-{1-(2-aminoethyl)piperidine}salicylideneimine, L⁵ = 2-benzoyl pyridine-N-{1-(2-aminoethyl)pyrolidine}, L⁶ = 2-benzoylpyridine-N-{1-(2-aminoethyl)piperidine}] have been synthesized and characterized. Zn(II) complexes of those ligands have been prepared by conventional sequential route as well as by template synthesis. The same complexes are obtained from the two routes as evident from routine physicochemical characterizations. All the Schiff-bases exhibit photoluminescence originating from intraligand (π–π*) transitions. Metal mediated fluorescence enhancement is observed on complexation of HL¹-HL⁴ with Zn(II), whereas metal mediated fluorescence quenching occurs in Zn(II) complexes of L⁵ and L⁶.     

Stereoselectivity in Diphos Addition to Molybdenum Complex with Pyridine‐2‐thionate (pyS) and η3‐Methallyl Coordinated Ligands

The conformational isomers endo‐ and exo‐[Mo{η³‐C₃H₄(CH₃)}(η²‐pyS)(CO)(η²‐diphos)] (diphos: dppm = {bis(diphenylphosphino)methane}, 2 ; dppe = {1,2‐bis(diphenylphosphino)ethane}, 3 ) are prepared by reacting the double‐bridged pyridine‐2‐thionate (pyS) complex [Mo{η³‐C₃H₄(CH₃)}(CO)₂]₂(η¹:η²:μ‐pyS)₂, 1 with diphos in refluxing acetonitrile. Stereoselectivity of the methallyl, C₃H₄(CH₃), ligand improves the formation of the exo‐conformation of 2 and 3 . Orientations and spectroscopy of these complexes are discussed.     

Thermodynamic Model for ThO<Subscript>2</Subscript>(am) Solubility in Isosaccharinate Solutions

Extensive studies on ThO₂(am) solubility were carried out as functions of a wide range of isosaccharinate concentrations (0.0002 to 0.2 mol⋅kg⁻¹) at fixed pH values of about 6 and 12, and varying pH (ranging from 4.5 to 12) at fixed aqueous isosaccharinate concentrations of 0.008 mol⋅kg⁻¹ or 0.08 mol⋅kg⁻¹, to determine the aqueous complexes of isosaccharinate with Th(IV). The samples were equilibrated over periods ranging up to 69 days, and the data showed that, in most cases, steady-state concentrations were reached in <15 days. The data were interpreted using the SIT model, and required the inclusion of mixed hydroxy-ISA complexes of Th(IV) [Th(OH)ISA²⁺, Th(OH)₃(ISA)₂^-_{2}^{-}, and Th(OH)₄(ISA)₂^2-]_{2}^{2-}] with log ₁₀ K ⁰=12.5±0.5,4.4±0.5 and −3.2±0.5 for the reactions:

Chemie polyfunktioneller Moleküle, 126 Mitt. Synthese, Struktur und Tautomerie von 5-Fluor-N(1), N(3)-bis(diphenylphosphanyl)-uracil

Summary 5-Fluoro-uracil (1) reacts with chloro-diphenylphosphane to 5-fluoro-N(1), N(3)-bis(diphenylphosphanyl)uracil (3) which was characterized by X-ray crystallography, IR, and mass spectra.¹⁹F,³¹P{¹H},¹³C{¹H}, and¹H NMR spectra indicate that3 rearranges inTHF solution to some extent to the tautomeric 5-fluoro-O(2), O(4)-bis(diphenylphosphanyl)uracil (4). If the solvent contains traces of water, Ph₂P(O)-PPh₂ (6) and uracil derivatives are formed by hydrolysis.

Herrn Professor Dr.Walter Siebert zum 60. Geburtstag gewidmet.     

Comparative structural and fungicidal studies of Mono-methyl phthalate and its Tin(IV) derivatives

The results of an investigation into the fungicidal properties of some organotin(IV) compounds with Mono-methyl phthalate are reported. The compounds were characterized by various spectroscopic techniques including ¹H-¹³C-¹¹⁹Sn-NMR, FT-IR, and ¹¹⁹Sn Mössbauer studies. On the basis of these techniques, all the complexes show penta coordination with a trigonal bipyramidal environment around the tin. The synthesized compounds were tested against a number of plant pathogenic fungi. The fungicidal data reveal that the tri-phenyltin(IV) compound proves to be a powerful fungicide. Comparison between the fungicidal activity of the trialkyltin(IV) compounds shows that the tri-phenyl tin(IV) complex is most active against all plant pathogens; the rest of the complexes also exhibit significant antifungal activity but less than the former one.     

Two Supramolecular Nickel(II) Complexes: Syntheses,Crystal Structures and Solvent Effects

Two nickel(II) complexes, namely {[NiL(MeOH)(μ‐OAc)]₂Ni} · 2CH₂Cl₂ · 2MeOH ( 1 ) and {[NiL(EtOH)(μ‐OAc)]₂Ni} · 2EtOH ( 2 ) {H₂L = 5, 5′‐dimethoxy‐2, 2′‐[(ethylene)dioxybis(nitrilomethylidyne)]diphenol}, were synthesized and structurally characterized. Two trinuclear Ni^II complexes are both hexacoordinate around the central Ni^II atoms, showing octahedral coordination arrangements, and each complex comprises three divalent Ni^II atoms, two deprotonated L^2– ligands, in which four μ‐phenoxo oxygen atoms forming two [NiL(X)] (X = MeOH or EtOH) units, and coordinated and non‐coordinated solvent molecules. Complex 1 exhibits a 2D supramolecular network through intermolecular O–H ··· O, C–H ··· O and C–H ··· π interactions, whereas complex 2 forms an infinite 1D chain by intermolecular C–H ··· O hydrogen bonding interactions.     

The Homoleptic U(NCSe)84– Anion in (Pr4N)4U(NCSe)8·2CFCl3 and Th(NCSe)4(OP(NMe2)3)4·0.5CH3CN·0.5H2O: First Structurally Characterised Actinide Isoselenocyanates

The neutral thorium complex Th(NCSe)₄(OP(NMe₂)₃)₄ and homoleptic octa(isoselenocyanato)uranate anion U(NCSe)₈^4– in (Pr₄N)₄U(NCSe)₈·2CFCl₃ ( 1 ) were synthesised and structurally characterised. (Pr₄N)₄U(NCSe)₈·2CFCl₃ contains the U^IV anion U(NCSe)₈^4– and was characterised using IR spectroscopy and single‐crystal X‐ray diffraction. Th(NCSe)₄(OP(N(CH₃)₂)₃)₄·0.5CH₃CN·0.5H₂O ( 2 ) was characterised using IR and Raman spectroscopy, as well as ³¹P{¹H}, ¹⁵N{¹H}, ¹⁴N{¹H}, ¹³C{¹H}, ¹H and ⁷⁷Se NMR spectroscopy and structurally characterised using single‐crystal X‐ray diffraction. The U(NCSe)₈^4– anion and Th(NCSe)₄(OP(N(CH₃)₂)₃)₄·0.5CH₃CN·0.5H₂O complex are the first structurally characterised actinide‐isoselenocyanates. The crystal structures shows an approximate square antiprismatic arrangement of the ligands around the actinide(IV) atoms.     

Dioxygen Activation by Redox-Active Bis(aldimine) Ligand Bridged Diruthenium Complex Possessing Singlet Ground State

The unexplored ‘actor’ behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac)₂} (acac= acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2⁻), and bis(carboxamido) (L3²⁻)-bridged isovalent {Ru^II(μ-L1)Ru^II}, 1/ {Ru^III(μ-L3²⁻)Ru^III}, 3 and mixed-valent {Ru^II(μ-L2⁻)Ru^III}, 2 . Authentication of the complexes along with the redox non-innocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for ³O₂ activation despite of the closed shell configuration of 1 (S=0) to give carboxamido derived 2 / 3 .     

Diorganotin complexes of carboxylates: synthesis and characterization

Diorganotin complexes of monoisopropyl and monomethyl nadiate, succinate, and phthalate were synthesized and characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR spectroscopic techniques. The spectroscopic investigation demonstrated that carboxylate is bidentate in the diorganotin complexes. On the basis of ¹ J(¹¹⁹Sn–¹³C) and ² J(¹¹⁹Sn–¹H) values, C–Sn–C bond angles were also calculated. The newly synthesized complexes were also screened for their antibacterial activities against Gram-positive and Gram-negative pathogenic strains of bacteria.     

Synthesis and characterization of monomeric palladium(II) pyridine-2-chalcogenolate complexes

Mononuclear palladium(II) complexes of the type [Pd(Epy)(S^∩S)(PPh₃)] [E=S or Se; S^∩S=S₂CNEt₂, S₂P(OR)₂ (R=Et, Prⁿ, Prⁱ)] have been prepared. All the complexes have been characterized by elemental analysis and NMR (¹H, ³¹P{¹H}, ⁷⁷Se{¹H}) spectral data. The NMR data indicate that there are two species in solution, i.e. one with chelating S^∩S ligand predominates (∼95%) while the other with chelating Epy and monodentate S^∩S existing in ∼5% concentration. The X-ray crystal structure of [Pd(Spy){S₂P(OPrⁱ)₂}(PPh₃)] has been determined. The square planar palladium atom is coordinated to asymmetrically chelated (PrⁱO)₂PS₂⁻ ligand, PPh₃ and pyS⁻ groups.