Showing papers on "Denticity published in 1978"

Direct electrochemical synthesis of some metal chelate complexes

Abstract: A convenient electrochemical synthesis of various ML2, ML3, ML4 and MOL2 complexes (M = Ti, Zr,Hf, V,Cr, Mn,Fe, Co,Ni, Cu,In; L = acetylacetonate anion, 3-hydroxy-2-methyl-4-pyronate anion, 2-acetylpyrrolate anion, and other bidentate ligands) is described. The metal, as the anode of simple cell, is oxidised in the presence of the parent compound of the ligand (HL) in an organic solvent mixture. Gram quantities of complex can be produced in a few hours; other advantages of this method are discussed. Current efficiency measurements serve to identify the reaction mechanism.

Comparison of 8-methylquinoline and benzo[h]quinoline complexes of palladium(II) with those of related ligands. Crystal and molecular structure of aqua(benzo[h]quinoline)[2-(dimethylaminomethyl)phenyl-N]palladium(II) perchlorate

Abstract: Benzo[h]quinoline (bquin) does not cleave the chloride bridge of [{Pd(dmp)Cl}2][dmp = 2-(dimethylaminomethyl)phenyl-N], 8-methylquinoline (8Me-quin) does so if in large excess, while other ligands L (pyridine, 2-methylpyridine, or 7-methylquinoline) give monomeric [Pd(dmp)Cl(L)] quantitatively. Measured equilibrium constants for the bridge-cleavage reaction indicate that the Pd⋯H–C interactions in bquin and 8Me-quin complexes are strongly destabilising. Rotations about the Pd–N bonds in [Pd(dmp)Cl(L)] are slow and no faster than equilibria involving dissociation to [{Pd(dmp)Cl}2]. Stable complexes of bquin and of 8Me-quin can, however, be readily formed if the strongly bridging chloride ligands are replaced by nitrate or perchlorate. For example, stoicheiometric addition of bquin to an acetone solution derived by addition of Ag[ClO4] to [{Pd(dmp)Cl}2] gives the title complex, [Pd(dmp)(bquin)(OH2)][ClO4], the crystal and molecular structure of which has been determined by single-crystal X-ray diffraction. The crystals are triclinic, a= 11.050(4), b= 9.808(4), c= 11.412(5)A, α= 77.04(4), β= 110.90(4), γ= 97.00(3)°, and Z= 2, space group P. The structure was solved by standard heavy-atom methods and refined by least squares, using 1976 observed data, to R 0.053. The co-ordination is essentially square planar with mutually trans nitrogen atoms. The most notable feature is the short H10(bquin)⋯Pd distance [2.09(6)A], but consistent with this being a non-bonding interaction is the ca. 10° tilt of the bquin (Pd–N–C 111 and 131°) in a direction that lessens this clash. From a comparison of 1,10-phenanthroline and other authentic bidentate ligands with 8Me-quin and bquin, it is concluded that the latter ligands are unidentate.

Cobalt exchange in horse liver alcohol dehydrogenase.

Abstract: The preparation of metal hybrid species of horse liver alcohol dehydrogenase is made possible by the development of carefully delineated systems of metal in equilibrium metal exchange employing equilibrium dialysis The conditions which are optimal for the site-specific replacement of the catalytic and/or noncatalytic zinc atoms of the native enzyme by cobalt are not identical with those which are utilized for substitution with 65Zn Thus, while certain 65Zn hybrids can be prepared by exploiting the differential effects of buffer anions, the cobalt hybrids are generated by critical adjustments in the pH of the dialysate Factors which may determine the mechanism of metal replacement reactions include acid-assisted, ligand-assisted, and metal-assisted dechelation, steric restriction, and ligand denticity as well as physicochemical properties of the enzyme itself The spectral characteristics of the catalytic and noncatalytic cobalt atoms reflect both the geometry of the coordination complexes and the nature of the ligands and serve as sensitive probes of these loci in the enzyme

Über 3,3,6,9,9‐Pentamethyl‐2,10‐diaza‐bicyclo‐[4.4.0]‐1‐decen und einige seiner Derivate. Über synthetische Methoden. 13. Mitteilung

Abstract: 3,3,6,9,9-Pentamethyl-2,10-diaza-bicyclo[4.4.0]-1-decen and some of its derivatives A simple synthesis for the bicyclic amidine 1 (Scheme 3) is described. This base and the salts which were prepared from it show solubility characteristics which make the amidine a potentially useful reagent for salt formation of carboxylic acids and related proton complexes of bidentate ligands. Among the derivatives made from 1 are the sterically strongly hindered N-alkylated amidines 11, 12 and 14 (Scheme 5), as well as the stable crystalline N1-oxidoamidine-N2-oxyl radical 2 (Scheme 6). The ability of the latter to serve as a paramagnetic chelating ligand for metal ions is illustrated by the preparation of a corresponding nickel(II) complex. The radical is also a source for the α-nitronyl-nitrosonium cation 4 which shows in its reactivity towards conjugated dienes and olefines some of the expected resemblance to singlet oxygen.

The Crystal and Molecular Structure of Dichlorobis(2-pyridinethiolato)tin(IV)

Abstract: The crystal and molecular structures of dichlorobis(2-pyridinethiolato)tin(IV) have been determined by X-ray analysis. The crystal belongs to the triclinic system: a=8.340(8), b=12.456(7), c=7.178(3) A, α=86.46(4), β=111.06(5), γ=99.18(6)°, space group P\bar1 with Z=2. The structure was determined by the heavy atom method and refined by the block-diagonal least-squares method (R=0.058). The complex is a distorted octahedral complex in which 2-pyridinethiolato ligands act as bidentate ligands, two four-membered (Sn, S, C, and N) chelate rings being present. Two Sn–Cl bonds are cis, two Sn–N bonds are cis, and two Sn–S bonds are trans configuration.

Stabilized catalyst complex of rhodium metal, bidentate ligand and monodentate ligand

Abstract: This invention provides a catalyst and process for achieving highly selective straight chain aldehyde formation from alpha-olefins under hydroformylation conditions. The improved hydroformylation results are obtained under mild conditions of temperature and pressure in the presence of a stabilized catalyst complex of rhodium metal, bidentate ligand and monodentate ligand represented by the formula: ##STR1## Illustrative of a preferred bidentate ligand is trans 1,2-bis-(diphenylphosphinomethyl)cyclobutane. Illustrative of a preferred monodentate ligand is diphenylethylphosphine. It is an essential feature of the invention process that the monodentate ligand is provided in a molar excess with respect to the rhodium metal in the stabilized catalyst complex.

Polymer bound multidentate complexes

Abstract: Polymer bound multidentate complexes are prepared by reacting pendant benzyl chloride and benzyl iodide groups on a variety of polymer supports, including crosslinked polystyrene, with 3,3'-iminodiproprionitrile and reducing the nitrile groups by treatment with, for example, a boron hydride-tetrahydrofuran complex to form the amine. The amine is a precursor for other ligand systems; for example, the primary amine groups formed condense with an aldehyde or ketone to yield five coordinate Schiff base ligands. The polydentate amine ligand systems are useful for synthesis of chelating agents for sequestering metal ions from solution for purification or concentration purposes. Metal complexes of these ligands with manganese, iron, cobalt, nickel, copper, and zinc can be prepared which are useful as heterogeneous oxidation catalysts.

Nickel(II) and copper(II) complexes of 2,5-dimethyl-1,3,4-thiadiazole

Abstract: Nickel(II) and copper(II) complexes of 2,5-dimethyl-1,3,4-thiadiazole Ni(DTZ)X2 (X = Cl or Br) and M(DTZ)2X2 (M = Ni, X = 1 or N03; M = Cu, X = Cl, Br or NO3) have been prepared. The i.r. spectra show that in all the complexes the ligand is N,N- or N-bonded to the metal while the sulfur atom does not participate in coordination, and that the halide ions are coordinated forming terminal M-X bonds. The NO 3 - group is coordinated in both the nitrato complexes. Magnetic moments of 3.07–3.29 B.M. for the nickel(II) and 1.86–1.92 B.M. for the copper(II) complexes were observed. The Ni(DTZ)X2 complexes have a pseudo-tetrahedral [N2X2] coordination with N,N-bridging ligand molecules. The Ni(DTZ)2X2 and Cu(DTZ)2X2 complexes, with predominantly monodentate ligand, involve six-coordinate metal atoms with strong equatorial [N2X2] bonds and weaker axial bonds.

Komplexbildung mit Aminophosphinen. IX. Vier- und fünffach koordinierte Komplexverbindungen des Nickels mit N, N-Bis(diphenylphosphino)anilin†

Abstract: Die Synthese des leicht zuganglichen Diphosphinoanilins, PhN(PPh2)2, und verschiedene Typen seiner Chelatkomplexe mit Nickel(II) werden beschrieben. Der Ligand (NP2) bildet planare Komplexe [(NP2)NiX2] (X = Cl, Br, I, NCS) und [Ni(NP2)2](ClO4)2 sowie die funffach koordinierten Verbindungen [(NP2)2NiX]ClO4. Fur die letzteren wird eine quadratisch-pyramidale Struktur angenommen. Complex Formation with Aminophosphines. IX. Fourfold and Fivefold Coordinated Nickel(II) Complexes of the Bidentate N, N-Bis(diphenylphosphino)phenylamine The preparation and characterization of the ligand PhN(PPh2)2 and some of its nickel complexes are reported. The ligand (NP2) forms stable planar complexes [(NP2)NiX2] (X = Cl, Br, I, NCS) and [Ni(NP2)2](ClO4)2, and the pentacoordinated, square-pyramidal complexes [(NP2)2NiX]ClO4.

The crystal structure of cis-chlorobis(triethylphosphine)-1,8-naphthyridineplatinum(II) tetrafluoroborate, [PtCl(PEt3)2(naph)]BF4, a complex containing a monodentate 1,8-naphthyridine ligand

Abstract: The crystal structure of cis-chlorobis(triethylphosphine)-1,8-naphthyridineplatinum(II) tetrafluoroborate has been determined by single crystal X-ray diffraction and refined to an R-value of 0.063. The cell dimensions are a = 1.4246, b = 1.2676, c = 1.6530 nm, β = 115.66°. The space group is P21/c with 4 molecules per unit cell, and the measured density is 1.665 g cm−3. The structure is essentially a 4-coordinate square planar platinum(II) complex containing monodentate 1,8-naphthyridine. Interatomic distances to platinum are: Pt—Cl, 236.6(4); Pt—P(1), 225.4(4); Pt—P(2), 225.2(4); Pt—N(1), 208.3(11); and Pt—N(2), 304.5(14) pm. The structure is discussed in relation to variable temperature nmr studies of solutions, which indicate fluxional behaviour of the heterocyclic ligand.

Complexes of cobalt(II), nickel(II) and copper(II) with 4-amino-3,5-dimethylisoxazole

Abstract: Complexes of the type M(4-ADI)nX2 · mH2O (where 4-ADI = 4-amino-3,5-dimethylisoxazole; n = 1–4; X = Cl, Br, I, SCN, ClO4; m = 1–4) have been studied by i.r. and electronic spectroscopy, magnetic and conductivity measurements. The ligand behaves as a monodentate -NH2 bonded species in monomeric complexes, but as a bridging ligand-NH2 and -N(ring) bonded species in polymeric complexes. All the compounds have an octahedral stereochemistry, except Co(4-ADI)2X2 (X = Cl, Br, I) complexes, which are tetrahedral.

Reactions of Tin(II) and Tin(IV) Xanthates: Crystal Structure of Tetrakis(O-ethylxanthato)tin(IV)

Abstract: Tin(II) xanthates form adducts with donor molecules and react with excess xanthate to form the tris-xanthato ion, Sn(EtOCS2)3-. No such reactions are observed with tin(IV) xanthates. Reaction of quinolin-8- ol with tin(IV) ethylxanthate results in the replacement of two xanthate moieties by two oxinato ions. The crystal structure of [Sn(EtOCS2)4] has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.038 for 2378 'observed' reflections. The tin(IV) coordination environment resembles that observed in the N,N- diethyldithiocarbamate analogue, two of the xanthate ligands being monodentate and coordinating cis [Sn-S, 2.488(2), 2.499(2) Ǻ] in the six-coordinate coordination sphere while the other two ligands are bidentate, the Sn-S distances trans to the monodentate ligands being slightly longer [2.617(2), 2.627(2)Ǻ] than the other two [2.562(2), 2.539(2)Ǻ]. Crystals are monoclinic, P21/c, a 10.341(5), b 10.465(4), c 21.88(1) Ǻ, β 98.36(4)°, Z 4.

Complexes of dichlorobis(halosulphato)titanium(IV) with pyridine, quinoline, dimethyl sulphoxide and acetylacetone

Abstract: The position of the various infrared bands in the spectra of dichlorobis-(halosulphato) titanium(IV), TiCl 2 (SO 3 X) 2 with X = F, Cl, indicates the bidentate nature of the halosulphate groups. They form 1:1 adducts with pyridine, quinoline and dimethyl sulphoxide. The infrared spectra of these complexes indicate the monodentate nature of the halosulphate groups. The infrared spectra of TiCl 2 (SO 3 X) 2 ·DMSO indicate that the coordination of dimethyl sulphoxide is through its oxygen atom and not through the sulphur atom. Acetylacetone reacts with dichlorobis(halosulphato)titanium(IV) giving Ti(acac) 2 (SO 3 X) 2 which have also been characterized from their infrared spectra.

Palladium(II) complexes with primary thioamides

Abstract: Palladium(II) complexes of thioacetamide, thiooxamide,N o,N o-dimethylthiooxamide and ethyl thiooxamidate have been prepared and investigated by electronic and i.r. spectroscopy. It is concluded that the ligands always act as monodentate sulphur donors, and that planar [PdL4]X2 (X = Cl, Br or ClO4) compounds are formed. Theν(PdS) frequencies and the ligand field strengths are enhanced by electron donor groups and lowered by electron withdrawing groups.

Fluxional Behavior of Palladium(II) and Platinum(II) Complexes Containing both a Metal–Aryl Bond and a Pyrazole-derived Ligand

Abstract: New (acetophenone oximato, 2-C,N)- and (benzophenone oximato, 2-C,N)palladium(II) complexes containing poly(1-pyrazolyl)borato ligand (BPz4 or HBPz3, Pz=1-pyrazolyl) or poly(1-pyrazolyl)methane (CPz4 or HCPz3) were prepared and investigated by means of 1H-NMR spectroscopy. For the BPz4 complexes, the tumbling motion of the BPz4 ligand averaged the environments of all four pyrazolyl groups to give spectroscopic equivalence above 65 °C, and was virtually frozen at ca. −9°C. With regard to the HBPz3, CPz4, and HCPz3 complexes, all pyrazolyl groups were equivalent at high temperature exhibiting stereochemical nonrigidity. The well-defined slow-exchange limiting spectra were not obtained at ca. −34 °C. In addition, new (acetophenone oximato, 2-C,N)platinum(II) complexes involving the BPz4 or HBPz3 ligand were prepared. The bidentate coordination of the BPz4 ligand in the BPz4 platinum(II) complex was stereochemically rigid in the range of 29 to 110 °C in DMSO-d6. Three pyrazolyl groups in the HBPz3 platinum(II...

X-Ray crystal structure of a cryptate complex of lanthanum nitrate

Abstract: An X-ray crystal structure determination shows that the complex cations in [La(NO3)2{N(CH2CH2OCH2CH2OCH2CH2)3N}]3[La(NO3)6] contain a lanthanum ion co-ordinated to eight cryptate donor atoms together with two bidentate nitrate ions, the cryptate ligand being somewhat distorted to accommodate the latter.

Synthesis and Characterisation of Bis(π-cyclopentadienyl) N-aryl Substituted Dithiocarbamato Chloro Titanium (IV) Compounds

Abstract: Bis(π-cyclopentadienyl) N-aryl substituted dithio-carbamato chloro titanium(IV) compounds have been synthesised by the reaction of bis(π-cyclopentadienyl) titanium(IV) dichloride with ammonium (N-aryl substituted) dithiocarbamates in refluxing dichloromethane. Molecular weight, conductance and infrared studies point out that these complexes are monomeric non-electrolytes in which the dithiocarbamate ligands are bidentate. Therefore, a coordination number of ‘5’ may be assigned to the titanium(IV) atom in all the twelve complexes. Electronic spectra have also been obtained for these complexes

Synthesis of some diplatinum complexes, including bis-µ-[bis(diphenylphosphino)methane]-µ-methylene-dichlorodiplatinum, [Pt2Cl2(µ-CH2)(µ-Ph2PCH2PPh2)2], from [Pt2Cl2(µ-Ph2PCH2PPh2)]

Abstract: A number of diplatinum complexes including [Pt2Cl2(µ-CH2)(µ-dppm)2][dppm = bis(diphenylphosphino) methane], the first diplatinum complex containing a bridging CH2 group, and complexes [Pt2Cl2(µ-X)(µ-dppm)2](X = S and SO2) and [Pt2L2(µ-dppm)2][PF6]2(L = a monodentate ligand) have been prepared from [Pt2Cl2(µ-dppm)2].

Preparation and characterization of some ternary complexes of copper(II) with o-phenanthroline and oxygen donor ligands

Abstract: A series of eight ternary complexes, viz. [Cu(phen)(acac)] Cl and Cu(phen)L(H2O)n(phen = o-phenanthroline; L = a bidentate oxygen donor ligand; n = 0, 1 or 2), have been prepared and characterized by microanalysis, infrared spectral and electronic spectral measurements. The results indicate that the Cu(phen)2+ species has a great affinity for oxygen donor ligands resulting in chelate rings of varying sizes. Infrared spectral data indicate that the Cu-O bond weakens as the oxygen donor chelate ring increases in size; the Cu-N bond appears to be less sensitive to ring size. Tentative assignments for the electronic absorption bands have also been made.

Crystal and molecular structure of .eta.5-cyclopentadienyltris(N,N-dimethyldithiocarbamato)titanium(IV), a stereochemically rigid seven-coordinate chelate

Abstract: The crystal and molecular structure of the benzene solvate of ~5-cyclopentadienyltris(~,~-dimethyldithiocarbamato)titanium(IV), (q5-C5H5)Ti[S2CN(CH3)Zlj, has been determined by X-ray diffraction. The compound crystallizes in the monoclinic space group P21/c with four formula units in a cell having dimensions a = 10.154 (1) A, b = 11.444 (2) A, c = 22.411 (2) A, and /3 = 97.11 (6)' (pabsd = 1.44, pcalcd = 1.418 g ~ m ~ ) . Least-squares refinement, which employed 5072 independent diffractometer-recorded reflections having 2BZIoKai 5 54.83' and lFol > 1.580,, afforded residuals Rl = 0.077 and R2 = 0.079. Anisotropic thermal parameters were used for Ti, S, and the five C atoms of the cyclopentadienyl ligand; isotropic thermal parameters were employed for the remaining nonhydrogen atoms. The crystal contains discrete seven-coordinate molecules which have pentagonal-bipyramidal geometry and approximate symmetry C,-m. The v5cyclopentadienyl ligand occupies one axial position (Ti-C = 2.420-2.425 A), one bidentate dithiocarbamate ligand spans the other axial position and one equatorial position, and the other two bidentate dithiocarbamate ligands take the remaining equatorial positions. As expected, the TiS6C5 coordination group is extremely crowded, with all of the S-S and C-8 nonbonded contacts being less than the sum of the van der Waals radii. Because of the crowding, the Ti-§ bond distances are unusually long; the average Ti-S bond length of 2.611 A is 0.10 A longer than that in the closely related compound Ti[SzCN(CH3)2]3CI. Nonbonded repulsions are reduced, primarily, by expansion of the Ti-S bonds to the two equatorial ligands; these bonds average -0.07 8, longer than the Ti-S bonds to the spanning ligand.