Showing papers on "Denticity published in 1988"

The discovery of crown ethers.

Abstract: The discovery of the crown ethers stemmed from efforts to control the catalytic activity of vanadium and copper by complexation with multidentate ligands. The first crown ether, 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclo-octadeca-2,11-diene, was obtained in 0.4% yield during an attempt to prepare a phenolic ligand from catechol and bis(2-chloroethyl)ether. This compound, which complexed with the sodium cation, was the first compound known to display such activity and became known as dibenzo-18-crown-6, an 18-atom heterocycle containing 6 oxygen atoms. Some 60 related compounds were made involving heterocyclic rings containing 12 to 60 atoms including 4 and 10 oxygen atoms. There are optimum polyether ring sizes for the different alkali metal cations: 15 to 18 for sodium, 18 for potassium, and 18 to 21 for cesium. Complexes having polyether to cation ratios of 1:1, 3:2, and 2:1 were prepared. Solubilization of inorganic salts in aprotic solvents, especially by saturated crown ethers, was demonstrated.

Cobalt(II), nickel(II) and copper(II) complexes of bidentate bibenzimidazoles

Abstract: Complexes of cobalt(II), nickel(II) and copper(II) with novel bidentate bibenzimidazoles, [M(L-L)Cl2], where L-L are methylenebis(1, 1′-benzimidazole), methylenebis(2, 2′-benzimidazole) and dimethylenebis(2, 2′-benzimidazole) are described and characterized by different physical measurements. The four coordinate complexes have distorted tetrahedral or square coplanar structures. The bridging entity between the two donor groups apparently influences the ligand field strength and the ligands occupy a higher position than that of benzimidazole in the spectrochemical series.

Spectroscopic studies on copper(II) complexes derived from a substituted 2-acetylpyridine thiosemicarbazone

Abstract: Copper(II) complexes of general formula [Cu(L4A)X] (where L4A is the deprotonated ligand, 1 H-hexahydroazepine-1-thiocarboxylic acid-2-[1-(2-pyridinyl)ethylidene]hydrazide and X=Cl, Br, I, NCS, NO3 and OAc) and [Cu(HL4A)(L4A)]ClO4 have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r. spectra, electronic spectra, conductivity measurements and e.s.r. spectra in the polycrystalline state and in chloroform solution. For all complexes, except the perchlorate salt, coordination occurs via imine nitrogen, pyridine nitrogen and thione sulphur. For the perchlorate salt, L4A is tridentate, while HL4A is monodentate via imine nitrogen. Electronic spectra suggest planar geometry for all the complexes. The calculated e.s.r parameters suggest coordination through sulphur in agreement with the i.r. results.

Infrared absorbent comprising a metal complex compound containing two thiolato bidentate ligands

Abstract: The present invention relates to a metal complex compound useful in an infrared absorbent prepared by coordinating two bidentate ligands of the following formula (iii): ##STR1## wherein R 1 and R 2 each independently represents a hydrogen atom, a cyano group, or a substituted or unsubstituted alkyl, aryl or heterocyclic group, which may be the same or different. The present invention is further directed to an infrared absorbing composition comprising a metal complex compound prepared by coordinating two bidentate ligands of formula (iii) above to a center metal and neutralizing a complex ion with a cation. The present invention is also directed to an infrared absorbing article which comprises a metal complex compound prepared by coordinating two bidentate ligands of formula (iii) above to a center metal and neutralizing such a complex with a phosphonium cation.

Heat of reaction of (norbornadiene)molybdenum tetracarbonyl with monodentate and bidentate ligands : solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4

Abstract: Enthalpie de la reaction de (NBD)Mo(CO) 4 avec un certain nombre de coordinats monodentes et bidentes formant cis−L 2 Mo(CO) 4 . Influences des facteurs steriques et electroniques dans la determination de la force de la liaison Mo−L

Copper(II) and zinc(II) co-ordination compounds of tridentate bis(benzimidazole)pyridine ligands. Crystal and molecular structures of bis[2,6-bis(1′-methylbenzimidazol-2′-yl)pyridine]copper(II) diperchlorate monohydrate and (acetonitrile)[2,6-bis(benzimidazol-2′-yl)pyridine](perchlorato)copper(II) perchlorate

Abstract: Compounds are described of general formulae Cu(L1)X2, Cu(L1)2X2, Cu(L2)X2, and Cu(L2)2X2 with L1= 2,6-bis(benzimidazol-2′-yl)pyridine, L2= 2,6-bis(1′-methylbenzimidazol-2′-yl)pyridine, and X = Cl, Br, or ClO4. For comparison also a few zinc(II) halides were prepared and characterized. The compounds were structurally characterized by i.r., ligand-field, and e.s.r. spectra and for two representative cases [Cu(L1)(CH3CN)(ClO4)][ClO4](1) and [Cu(L2)2][ClO4]2·H2O (2) also by X-ray diffraction techniques. Compound (1) crystallizes in space group P21/c with a= 14.061(1), b= 20.638(1), c= 8.273(1)A, β= 101.119(8), and Z= 4; R= 0.0366 for 4 265 observed reflections with I > 2σ(I). Compound (2) crystallizes in space group P21/c with a= 8.4824(22), b= 29.1965(29), c= 16.7393(24)A, β= 95.836(17)°, and Z= 4; R= 0.062 for 3 165 observed reflections with I > 3σ(I). The structure of (1) consists of one tridentate chelating L1 ligand and CH3CN, co-ordinated in a square-planar geometry (Cu–N 1.96–2.03 A) with a perchlorato oxygen at 2.40 A, thereby completing a five-co-ordinate geometry. A sixth ligand at 2.8 A(from another perchlorate oxygen) is considered to be semico-ordinating. The structure of (2) consists of one tridentate and one bidentate L2, chelating in a five-co-ordinate geometry, again tetragonal pyramidal, with the apical ligand (Cu–N 2.51 A) coming from the bidentate chelating L2. The sixth donor atom, again from a perchlorate oxygen, at 2.70 A is considered to be semi-co-ordinating. Spectroscopic and magnetic data have been used to deduce structures for the other copper(II) compounds based on these two X-ray structures.

New multidentate ligands. 29. Stabilities of metal complexes of the binucleating macrocyclic ligand BISBAMP and dioxygen affinity of its dinuclear cobalt(II) complex.

Abstract: Preparation des composes macrocycliques, synthese des complexus de cobalt(II), etude de la protonation des amines du macrocycle et du complexe dioxygene obtenu en milieu basique. Titrages potentiometriques

Coordination Chemistry of the Calixarenes. II. Europium(III) and p-t-Butyl Calix[6]arene

Abstract: The possible nature of p-t-butyl-calix [6] arene complexes of lanthanide elements has been explored by determination of the single-crystal X-ray structure of a complex with a 1:2 europium/ ligand ratio, obtained from dimethylformamide (dmf ≡ Me2NCHO) solution. This complex is formulated as [ Eu (LH4)(Me2NCHO)6(OH)].LH6.~4Me2NCHO (LH6 = p-t-butyl-calix [6] arene) on the basis of the structure determination. Crystals are monoclinic, P21/n, a 36.11(3), b 23.35(2), c 21.85(2)Ǻ, β 97.46(6)°, Z = 4 formula units; R was 0.11 for 8488 'observed' reflections. The complex is remarkable in that the only interaction of either of the two calixarene ligands (one presumably doubly or triply deprotonated ) with the eight-coordinate europium atom is by way of one behaving as monodentate, the other having no interaction. Eu -O( calix ) is 2.35(1) Ǻ; Eu -O( dmf )6 range from 2.38(2) to 2.49(2)Ǻ, and Eu -O(H ½?) is 2.49(2)Ǻ.

Technetium(V)–nitrido complexes of dithiocarbazic acid derivatives. Reactivity of [TcN]2+ core towards Schiff bases derived from S-methyl dithiocarbazate. Crystal structures of [S-methyl 3-(2-hydroxyphenylmethylene)dithiocarbazato]nitrido(triphenylphosphine)technetium(V) and bis(S-methyl 3-isopropylidenedithiocarbazato)nitridotechnetium(V)

Abstract: New technetium(V)–nitrido complexes with bi- and tri-dentate Schiff bases, derived from the condensation of various aldehydes and acetone with the methyl ester of dithiocarbazic acid, NH2NHC(S)SCH3, were prepared by substitution or substitution–reduction reactions on the square-pyramidal complexes [TcVNCl2(PPh3)2] and [TcVINCl4]–. The final complexes all maintain the square-pyramidal geometry of the starting compounds with the TcN group in an apical position. The bidentate ligands give rise to mono- and di-substituted complexes, in which they are co-ordinated to the metal through the β-nitrogen atom and the thiol sulphur atom; in monosubstituted complexes, the remaining two positions in the plane of the square pyramid are occupied by triphenylphosphine (PPh3) and Cl– groups. The tridentate Schiff bases co-ordinate to the metal, in the basal plane, as doubly negatively charged ligands through the phenolic oxygen atom, the β-nitrogen atom, and the thiol sulphur atom, the fourth position being occupied by the phosphorus atom of a PPh3 group. The crystal structures of [TcNL1(PPh3)](1)[H2L1=S-methyl 3-(2-hydroxyphenylmethylene)dithiocarbazate] and [TcN(L12)2](2)(HL12=S-methyl 3-isopropylidenedithiocarbazate) have been determined. Relevant crystal data for (1) are: refined from 5 008 reflections with I 3σ(I) to a final R of 0.029, crystals are triclinic, space group P, with unit-cell dimensions a= 8.309(1), b= 12.294(1), c= 13.308(3)A, α= 96.22(1), β= 95.07(1), γ= 101.34(1), and Z= 2; for (2): refined from 1 756 reflections with I 3σ(I) to a final R of 0.023, crystals are monoclinic, space group I2/a, with unit-cell dimensions a= 16.707(3), b= 8.838(1), c= 12.514(2)A, β= 106.85(1)°, and Z= 4. In both complexes, the co-ordination around Tc is distorted square pyramidal with an apical multiply bonded nitrogen atom [TcN 1.611(3)A in (1) and 1.613(3)A in (2)] and the basal ligands bent away from the nitrido group.

Preparation and crystal structures of [AsPh4]4[Tc4N4O2(ox)6] and [AsPh4]2[TcO(ox)2(Hox)]·3H2O: technetium complexes containing quadridentate or unidentate oxalato ligands

Abstract: The reaction of oxalic acid (H2ox) with [AsPh4][TcNCl4] and [NBu4][TcOCl4] in aqueous acetone yields crystals of [AsPh4]4[Tc4N4O2(ox)6](1) and, after precipitation with AsPh4Cl, [AsPh4]2[TcO(ox)2(Hox)]·3H2O (2) respectively. Complex (1) crystallises in the monoclinic space group P21/n with cell parameters a= 14.433(1), b= 13.229(1), c= 27.020(1)A, β= 92.90(1)°, and Z= 4. Refinement with data measured with Cu-Kα radiation converged at R= 0.069 for 3 076 observed reflections. The anion in (1) is a cyclic tetranuclear complex, [Tc4N4O2(ox)6]4–, with Ci point symmetry. Each technetium(VI) atom is co-ordinated by five oxygen atoms and one nitrogen atom to give a distorted octahedron. In each half of the anion, a quadridentate oxalato ligand forms a bridge between the two octahedra, each of which is also linked to an adjacent octahedron by the corner sharing of an oxo ligand. Two oxygen atoms of a bidentate oxalato ligand and a nitrido nitrogen complete the octahedral co-ordination in each polyhedron. The Tc ⋯ Tc spacings of 3.586(2) and 5.756(3)A preclude any Tc–Tc bonding. The monoclinic crystals of complex (2) belong to the space group P21/c with a= 16.495(3), b= 14.802(2), c= 21.805(4)A, β= 98.76(1)°, and Z= 4. Refinement with 5 099 observed data measured with Mo-Kα radiation converged at R= 0.059. The technetium(V) atom is co-ordinated by six oxygen atoms to give a distorted octahedron. The structure of the anion is unusual in that it contains a protonated unidentate oxalato ligand and that there is no appreciable lengthening of the Tc–O bond trans to the oxo ligand.

Synthesis and characterization of six-coordinate ruthenium(II) complexes that contain trans spanning diphosphine ligands

Abstract: Preparation et modes de liaison des complexes [(trpy)Ru II (L)(Cl)](ClO 4 ) ou L=diphenyl-P-benzyl-N(Me) 2 -(CH 2 ) 6 -N(Me) 2 -benzyl-P-diphenyl

Organo–platinum–iron complexes containing one bridging Ph2PCH2PPh2 ligand. Crystal structures of [(OC)3Fe(µ-dppm)(µ-CO)Pt(PPh3)], [(OC)2Fe(µ-dppm){µ-C(O)C2H2}Pt(PPh3)], and [(OC)3Fe(µ-dppm)(µ-CMeCH2)Pt(PPh3)][BF4]

Abstract: Treatment of [Fe(CO)4(dppm-P)](dppm = Ph2PCH2PPh2) with [Pt(trans-PhCHCHPh)(PPh3)2] gave the bimetallic [(OC)3Fe(µ-dppm)(µ-CO)Pt(PPh3)](1) in 75% isolated yield. Complex (1) was also prepared by the sodium tetrahydroborate reduction of [(OC)3Fe(µ-dppm)(µ-CO)PtCl2] in the presence of PPh3. Its structure was established by X-ray crystallography: the crystals are triclinic, space group P, with a= 1 177.3(2), b= 1 198.4(1), c= 1 776.5(1) pm, α= 103.34(1), β= 107.81(1), γ= 91.76(1)°, and Z= 2; final R factor 0.0257 for 5 422 observed reflections. The structure shows that one of the carbonyl ligands is almost symmetrically bridging the Fe–Pt bond. Protonation of complex (1) with HBF4·OEt2 gave the hydride [(OC)4Fe(µ-dppm)PtH(PPh3)][BF4](4), 1H n.m.r. studies of which indicated the hydride ligand to be terminal on platinum. Ethyne reacted with (1) at 20 °C to give the complex [(OC)2Fe(µ-dppm){µ-C(O)C2H2}Pt(PPh3)](5), the structure of which was established by X-ray crystallography: the crystals are orthorhombic, space group Pbca, with a= 1 898.9(4), b= 1 828.3(3), c= 2 414.4(5) pm, and Z= 8; R 0.0381 for 4 163 observed reflections. The molecule contains a dimetallacyclopentenone ring in which the ethylenic bond is η2-bound to iron, so that the C(O)C2H2 moiety is σ-co-ordinated to platinum and η3-co-ordinated to iron. Unsymmetrical alkynes (MeCCH, PhCCH, 4-MeC6H4CCH, MeNHCH2CCH, HOMe2CCCH, and MeCO2CCH) also reacted with complex (1), at 80 °C, to give complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CRCH}Pt(PPh3)]. At 20 °C, MeCCH and 4-MeC6H4CCH reacted with (1) to give isolable complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CHCR}Pt(PPh3)] which isomerised in solution, at rates dependent on the steric bulk of R, to complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CRCH}Pt(PPh3)]. The mechanism of the alkyne-insertion reactions appears to involve an intermediate containing a monodentate dppm ligand co-ordinated to iron, formed by opening of the five-membered [graphic omitted]t ring in (1). Protonation of the alkyne complexes breaks the alkyne–CO link to give µ-vinyl cations of type [(OC)3Fe(µ-dppm)(µ-CRCH2)Pt(PPh3)]+(R = H, Me, or C6H4Me-4). The structure of [(OC)3Fe(µ-dppm)(µ-CMeCH2)Pt(PPh3)][BF4](16) has also been established by X-ray crystallography: the crystals are monoclinic, space group Cc, with a= 2 321.3(3), b= 1 091.2(2), c= 1 962.6(2) pm, β= 98.48(1)°, and Z= 4, R 0.0460 for 3 615 observed reflections. The structure shows that the µ-CMeCH2 moiety is σ-co-ordinated to platinum and η2-co-ordinated to iron. Treatment of complex (1) with MeO2CCCCO2Me displaced the PPh3 ligand to give [(OC)4Fe(µ-dppm)Pt(MeO2CCCCO2Me)](19). The complex [(OC)3Fe(µ-dppm)(µ-SO2)Pt(PPh3)](20) was formed in high yield when SO2 was bubbled through a dichloromethane solution of (1). In addition, analogues of many of the above complexes have been prepared with (Ph2P)2CCH2.

Synthesis of N-alkyl-3-hydroxy-2(1H)-pyridinones and coordination complexes with iron(III)

Abstract: The amidation of 2,5-dimethoxytetrahydrofuran-2-carboxylic acid methyl ester by primary alkylamines followed by acid-catalyzed rearrangements yields N-alkyl-3-hydroxy-2-pyridinones. The rearrangement reaction is promoted by the presence of metal ions, such as Fe/sup 3+/, Cu/sup 2+/, and Zn/sup 2+/, which have high affinities for the bidentate hydroxypyridinone binding group. The structures of N-butyl-3-hydroxy-2-pyridinone (HL') and its 3:1 complex with iron(III) (FeL'/sub 3//center dot/3H/sub 2/O) have been determined by x-ray crystallography. Bond lengths involving the pyridine ring indicate that a catechol-like aromatic resonance form is significant, particularly in the iron complex. The visible spectra for (FeL'/sub n/)/sup (3-n)+/ (n = 1-3) are virtually identical with those of previously characterized complexes of iron(III) and 3-hydroxy-2-(1H)-pyridinone (3,2-Hopo, HL). The log K/sub a/ (protonation constant) of HL' and log K/sub 3/ for formation of FeL'/sub 3/ (from FeL'/sub 2//sup +/ and (L')/sup /minus//) are higher by 0.5 log unit than those of the unsubstituted HL and FeL/sub 3/. Differences in equilibria at pH > 7 between solutions of FeL'/sub 3/ and those of FeL/sub 3/ have been studied by spectrophotometric titrations. The N-butyl derivative FeL'/sub 3/ hydrolyzes only above pH 10.5 in the presence of 3 mM excess HL', whereas three stepwise protonations (log K/sub a/ =more » 9.2, 10.6, 12) are observed in solutions of FeL/sub 3/ containing excess (several millimolar) HL. The contrasting behaviors of FeL'/sub 3/ and FeL/sub 3/ in alkaline solution are rationalized in terms of the absence or presence of a weakly acidic proton on the ligand nitrogen. 38 refs., 8 figs., 5 tabs.« less

Strukturelle Eigenschaften der Dicyanamid‐ und Tricyanmethanid‐Komplexe von Kupfer(II), Nickel(II) und Kobalt(II) mit Liganden des Pyrazol‐Typs Nukleophile Additionsreaktionen in einigen der untersuchten Systeme

Abstract: Aus den Systemen MIIX−L, mit M = Cu, Ni, Co; X = N(CN)2, C(CN)3; L = Pyrazol, 3(5)-Methylpyrazol, 3,5-Dimethylpyrazol, 3,4,5-Trimethylpyrazol, Indazol, wurde eine Reihe neuer Komplexe des Typs MX2L2 sowie auch die Verbindungen Cu{Indazol-N(CN)2}2 und Ni{Pyrazol-N(CN)2}2 isoliert. Die letztgenannten Komplexe enthalten anionische Chelat-Liganden, die durch nukleophile Addition des Pyrazol-Liganden an koordinativ gebundenes Dicyanamid entstanden sind. Diese Chelat-Liganden enthaltenden Komplexe bilden mit den entsprechenden Dicyanamid-Komplexen Coligandenisomeren-Paare. IR-, Elektronen oder auch ESR-Spektren zeigen an, das samtliche Komplexe Koordinationspolymere darstellen, mit einer Koordinationszahl sechs der Zentralatome. Diese wird ermoglicht durch eine in Bruckenfunktion wirkende Zweizahnigkeit der Dicyanamid- bzw. Tricyanmethanid-Liganden, oder uber eine ebenfalls in Bruckenfunktion wirkende Ligator-Funktion des Stickstoffs freier CN-Gruppen des Chelat-Liganden. Structure Properties of Dicyanamide and Tricyanmethanide Complexes of Copper(II), Nickel(II), and Cobalt(II) with Ligands of Pyrazole Type — Nucleophilic Addition Reaction in Some of the Studied Systems From the MIIX−L systems with M = Cu, Ni, Co; X = N(CN)2, C(CN)3; L = pyrazole, 3(5)-methylpyrazole, 3,5-dimethylpyrazole, 3,4,5-trimethylpyrazole, indazole, a series of new compounds of the type MX2L2, as well as the compounds Cu{indazole-N(CN)2}2 and Ni{pyrazole-N(CN)2}2 were isolated. The later compounds contain anionic chelate ligands which are formed by nucleophilic addition of the pyrazole ligand to dicyanamide bonded in the coordination sphere. These complexes of chelate ligands give with the corresponding dicyanamide complexes pairs of coligand isomers. The IR, electronic, or ESR spectra indicate that all complexes are polymeric in character, their central atoms showing a six coordination. This is made possible through bridging bidentate dicyanamide or tricyanmethanide ligands, and likewise through ligand function of the nitrogens from free CN groups of the chelate ligands participating also in some bridging function.