Showing papers in "Transition Metal Chemistry in 1994"

2-thiouracil-based cobalt(II), nickel(II) and copper(II) complexes

Abstract: Cobalt(II), nickel(II) and copper(II) complexes of 2-thiouracil and its arylazo derivatives were prepared. The elemental analysis suggest a range of 1∶1, 2∶1 and 1∶3 stoichiometries. Electronic spectra and magnetic susceptibility measurements were used to infer the structures and the i.r. spectra of the ligands and their complexes to identify the type of bonding.

Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo[3.2.2]nonylthiosemicarbazones

Abstract: Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo-[3.2.2]nonylthiosemicarbazones were prepared and characterized spectroscopically. 1H and 13C n.m.r. spectra of the thiosemicarbazones and a diamagnetic nickel(II) complex are reported, together with i.r., electronic and e.s.r. spectra of the metal complexes. The thiosemicarbazones and their copper(II) and nickel(II) complexes exhibit considerable growth inhibitory activity against Paecilomyces variotii, but show minimal activity against Aspergillus niger.

Synthesis, structure and electrochemical behaviour of cobalt(II) complexes with 2,6-bis(benzimidazol-2′-yl) pyridine

Abstract: The complexes Co(BBP)Cl2, Co(BBP)2SO4·H2O, Co(BBP)2(NO3)2·H2O, Co(BBP)2(ClO4)2 and Co(BBP−H)2· 2H2O, where BBP is 2,6-bis(benzimidazol-2′-yl) pyridine, were prepared and characterized by elemental analysis, electrical conductance, i.r. and electronic spectra. The electrochemical behaviour of the complexes was recorded and the X-ray crystal structure of Co(BBP)Cl2(MeOH)2 was determined. The geometry about cobalt is a distorted octahedron.

Kinetics of osmium(VIII) catalysis of periodate oxidation of DMF in aqueous alkaline medium

Abstract: The osmium(VIII) catalysed IO4 − oxidation of DMF in aqueous alkaline medium follows the rate law: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbiqaaaRfcqGHsi% slcaqGKbWaamWaaeaacaqGjbGaae4tamaaDaaaleaacaaI0aaabaGa% eyOeI0caaaGccaGLBbGaayzxaaGaai4laiaabsgaieGacaWF0bGaa8% xpamaalaaabaGaa83Aaiaa-TeadaWgaaWcbaacbaGaa4NmaaqabaGc% caWGlbWaaSbaaSqaaiaaiodaaeqaaOGaai4waiaabseacaqGnbGaae% Oraiaac2facaGGBbGaae4taiaabIeadaahaaWcbeqaaiabgkHiTaaa% kiaac2facaGGBbGaae4taiaabohadaahaaWcbeqaaiaabAfacaqGjb% GaaeysaiaabMeaaaGccaGGDbWaaSbaaSqaaiaa+rfaaeqaaaGcbaGa% aGymaiabgUcaRiaa-TeadaWgaaWcbaGaa4NmaaqabaGccaWGlbWaaS% baaSqaaiaaiodaaeqaaOGaai4waiaabseacaqGnbGaaeOraiaac2fa% caGGBbGaae4taiaabIeadaahaaWcbeqaaiabgkHiTaaakiaac2facq% GHRaWkcaWFlbWaaSbaaSqaaiaa+jdaaeqaaOGaai4waiaab+eacaqG% ibWaaWbaaSqabeaacqGHsislaaGccaGGDbaaaaaa!6B43! $$ - {\text{d}}\left[ {{\text{IO}}_4^ - } \right]/{\text{d}}t = \frac{{kK_2 K_3 [{\text{DMF}}][{\text{OH}}^ - ][{\text{Os}}^{{\text{VIII}}} ]_T }}{{1 + K_2 K_3 [{\text{DMF}}][{\text{OH}}^ - ] + K_2 [{\text{OH}}^ - ]}}$$ where K 2 is the equilibrium constant of the reaction [OsO4(OH)2]2− + OH− ⇌ [OsO5(OH)]3− + H2O K 3 is the formation constant for the complex between DMF and [OsO5(OH)]3− and k is the decomposition rate constant. The data suggest that the oxidation of DMF proceeds via the formation of a complex between DMF and osmium(VIII) which decomposes slowly, followed by a fast reaction between the reduced osmium(VI) species and IO4 −. The reaction constants involved in the mechanism are derived.

Copper(II) complexes of 6-methyl-2-formylpyridine 4N-substituted thiosemicarbazones

Abstract: Copper(II) complexes of 6-methyl-2-formylpyridine thiosemicarbazone, and its 4N-methyl-, 4N-ethyl-, 4N-phenyl-,4 N-dimethyl-, 4N-diethyl-, 4N-dipropyl-, 3-pyrrolidinyl, 3-piperidinyl- and 3-hexamethyleneiminylthiosemicarbazone derivatives were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as 1H and 13C n.m.r. spectra of the thiosemicarbazones, were obtained. The thiosemicarbazones and their copper(II) complexes show either modest or no growth inhibitory activity against Aspergillus niger, but the 4N-dialkyl- and 3-azacyclo-derivatives exhibit considerable activity against Paecilomyces variotii.

Six-coordinate dinuclear hexaazamacrocyclic complexes of nickel(II), copper(II) and zinc(II) with tetraamide group ligands

Abstract: A series of 20–24 membered macrocyclic dinuclear transition metal complexes [M2L1X4]-[M2L4X4] (M = NiII, CuII or ZnII; X = Cl or NO3) have been synthesized by template condensation of diethylenetriamine with dicarboxylic acids. The bonding and stereochemistry of the complexes have been characterized by i.r.,1H-n.m.r., e.p.r. and electronic spectral studies, magnetic susceptibility and conductivity measurements. The Ni and Zn complexes exhibit octahedral geometry around the metal ion, whereas the Cu complexes possess a distorted octahedral geometry. Each metal ion is coordinated by two amide nitrogens and two secondary nitrogens of the diethylenetriamine moiety; the fifth and sixth coordination sites are occupied by the anions.

Catalytic activities of Schiff base aquocomplexes of copper(II) towards hydrolysis of amino acid esters

Abstract: Solid aquo CuII complexes of Schiff bases derived from amino acids have been prepared and characterized. Using a pH-stat method, the kinetics of base hydrolysis of the amino acid esters H2NCH2CO2Me·HCl (GE), (HO)-C6H4CH2(NH2)CO2Me·HCl (TE), MeS(CH2)2CH(NH2)-CO2Me·HCl (ME), HSCH2CH(NH2)CO2Et·HCl (CE), C3H3N2CH2CH(NH2)CO2Me·2HCl (HE) and [—SCH2-CH(NH2)CO2Me]2·2HCl (CysE) have been studied. The complexes enhanced the rate of hydrolysis substantially, the values of the second-order rate constants being some 10–50 times greater than those obtained in the presence of the simple CuII ion.

Kinetics of the interaction of ninhydrin with a [Cr(histidine)(H2O)3]2+ complex

Abstract: The composition of the N-diketohydrindylidene histidinato chromium(III) complex formed by interaction of ninhydrin with the [Cr(histidine)(H2O)3]2+ complex has been determined using Job's method of continuous variations. The reaction is slow and the kinetic studies were carried out under varying conditions of pH, temperature and [ninhydrin]. The observed pseudo-first order rate constant under these conditions follow the rate equation: $${1 \mathord{\left/ {\vphantom {1 k}} \right. \kern- ulldelimiterspace} k}_{obs} = {1 \mathord{\left/ {\vphantom {1 {\left\{ {K_t k_3 [N]} \right\} + {1 \mathord{\left/ {\vphantom {1 {k_3 }}} \right. \kern- ulldelimiterspace} {k_3 }}}}} \right. \kern- ulldelimiterspace} {\left\{ {K_t k_3 [N]} \right\} + {1 \mathord{\left/ {\vphantom {1 {k_3 }}} \right. \kern- ulldelimiterspace} {k_3 }}}}$$ The reaction has the features of a template mechanism which proceeds through coordination of ninhydrin to the [Cr(histidine)]2+ complex. The reaction is expected to involve the combination of two ligands (ninhydrin and histidine) attached to the same CrIII (CLAM reaction). The CrIII ion provides a better opportunity for the reaction of ninhydrin and histidine by assembling their reactive groups together. On the basis of the observed data the probable mechanism has been proposed.

Spectral and biological studies of copper(II) complexes of 2-acetyl-pyridine thiosemicarbazones with bulky 4N-substituents

Abstract: Copper(II) complexes of a large number of 2-acetylpyridine 4N-alkyl thiosemicarbazones were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as 1H and 13C n.m.r. spectra of the thiosemicarbazones, were obtained. Both the thiosemicarbazones and their complexes show either modest or no growth inhibitory activity against Aspergillus niger, but many have considerable activity against Paecilomyces variotii. There is a relationship between the antifungal activity and size of the 4N-substituent for both the thiosemicarbazones and their copper(II) complexes.

Multi-dimensional crystal engineering of metal complexes based on complementary hydrogen bonding

Abstract: Controlling molecular assembly at the molecular and supramolecular level is currently attracting appreciable interest worldwidd ~'2). Attempts to construct predictable crystal structures have exploited the directional intermolecular interactions associated with hydrogenbonding (a'4). The design of organic molecular solids utilizing the self-assembly of molecules which contain complementary hydrogen-bonding groups is evident in the research of Whitesides and co-workers (5), Lehn and co-workers(6), Etter and co-workers ~7) and Hamilton and co-workers ~s). The approach has also been used to design materials for non-linear optics(9), for inducing supramolecular mesophases (a~ and the directed assembly of liquid crystalline polymers (a ~). This paper describes the extension of these principles for the first time to transition metal coordination compounds. Specifically, the bidentate ligand dithiobiuret (Hdtb) forms neutral S,S'-coordinated complexes ~12) with nickel, palladium and platinum, which possess an arrangement of hydrogen-bond donor and acceptor sites analogous to melamine and are capable of interacting with molecules with complementary hydrogenbonding capabilities. Through the judicious choice of the properties of the complementary organic molecule, e.g. in terms of steric bulk, additional H-bonding sites, aromaticity, etc., the dimensionalities of the intermolecular interactions have been varied. Scheme 1 illustrates how

The preparation and electrochemistry of gold(III), palladium(II) and platinum(II) complexes with 2-(diphenylphosphino)thiobenzene: X-ray crystal structure of [Au(Ph2PC6H4S)(Ph2][BPh4]

Abstract: Tetrachloroaurate(III) reacts with two equivalents of the bidentate (1-) mixed phosphinothiol ligand 2-(diphenylphosphino)benzenethiol (DPPBTH) in mildly alkaline MeOH to give a cation that can be precipitated from solution as the tetraphenylborate salt, the title complex [Au(DPPBT)2][BPh4] (1). The X-ray crystal structure of the complex shows it has a square planar geometry. K2[PtCl4] or PtCl4 react with DPPBTH in mildly alkaline MeOH to give the 16 electron platinum(II) complex [Pt(DPPBT)2] (2), whilst reaction of Na2[PdCl4] with DPPBTH under similar conditions gives the 16 electron palladium complex [Pd(DPPBT)2] (3). The complexes have been studied by u.v., i.r. and n.m.r. The electrochemical behaviour of complex (1) was also investigated.

Electrochemical synthesis of benzoylglycine and ethylphthaloyl-glycine complexes of transition metal ions

Abstract: The direct electrochemical oxidation of metallic iron, cobalt, nickel and copper in Me2CO solution of benzoylglycine and/or ethylphthaloylglycine gave products with high yields. For each of the complexes, the electrochemical efficiency is commensurate with the metals being divalent. Conventional physical and chemical studies were used to characterize the isolated complexes and octahedral geometry was suggested for them on the basis of magnetic and electronic spectral studies. The i.r. spectra show that the ligands coordinate in a bidentate fashion; the carboxylate ion is monodentate. The molar conductances agree with the complexes being non-electrolytes.

Kinetic study of the reaction betweentrans-aquanitridotetra-cyanorhenate(V) and different cyanide species

Abstract: The kinetics of the reaction between [ReN(H2O) (CN)4]2− and cyanide has been studied in the ca. pH 8–14 range. The aqua ligand in the [ReN(H2O)(CN)4]2− complex is substituted by both CN− ions and HCN according to the following reaction: $$[ReN(H_2 O)(CN)_4 ]^{2 - } + CN^ - /HCN(L)\underset{{K_{ - L} }}{\overset{{K_L - k_L }}{\longleftrightarrow}} [ReN(L)(CN)_4 ]^{m - } + H_2 O$$ At 25° C and μ = 1.0 (KNO3), the equilibrium, forward and reverse rate constants of the reaction with CN− ions were determined as 601(69)m−1, 7214(411)m−1 s−1 and 12(6) s−1, respectively, and the forward rate constant for HCN as 3.9(7) × 104m−1s−1. A dissociative activation is proposed.

Kinetic studies of the oxidation of chromium(III) by N-bromosuccinimide

Abstract: A kinetic study of the oxidation of chromium(III) by N-bromosuccinimide (NBS) in aqueous solutions and H2O-MeOH solvent mixtures were performed. The kinetics in aqueous solutions obeyed the rate law: d[CrVI]/dt = {k4KhK2[NBS][CrIII]T}/[+]{1 + Kh/[H+] + (K1 + KhK2/[H+][NBS])} where Kh, K1 and K2 are the hydrolysis constant of [CrIII(H2O)6]3+, and pre-equilibrium formation constants for the protonated and deprotonated precursor complexes, respectively. An innersphere mechanism is proposed. An argument based on isokinetic correlations among activation parameters for the oxidation of a series of cobalt(II) and chromium(III) complexes including [Cr(H2O)6]3+ is presented in support of a common mechanism for these reactions.

Five coordination modes of 4-aminopyrimidine with N-hydroxy-ethylethylenediaminetriacetatoruthenate(II)

Abstract: The complex [RuII(hedta)(4NH2pym)]−, hedta3− = N-hydroxyethylethylenediaminetriacetate, 4NH2pym = 4-aminopyrimidine, exists at pH 7 as five different coordination isomers, which are most readily distinguished by their electrochemical waves in comparison with the 2-aminopyridine (2NH2py) complex. The 2NH2py complex exhibits N(1) (pyridine bound), exo-NH2 (amine bound) and N(1), NH2-chelated species. The 4NH2pym complex forms N(1), exo-amine and N(3), NH2-chelated isomers analogues to the 2NH2py species, but also engages in η2 (olefin bound) coordination of the dearomatized 4NH2pym ring in C(5)–C(6), and another η2 type of complex involving electron density between N(1) and N(3) of the ring (η3 form). N(1), η2 and η3 isomers have also been detected for unsubstituted pyrimidine (pym), 4-methylprimidine (4CH3pym) and 2-aminopyrimidine (2NH2pym). Electrochemical waves (V versus NHE) for the five isomers are assigned as follows: (RuII/III) exo-NH2 (0.06 V), N(1) (0.29 V), η2 (0.49 V); (RuII/III) η3 (0.76 V); N(3), NH2-chelated (1.09 V).

Physicochemical studies of (o-vanillin thiosemicarbazonato)-nickel(ii) chelate

Abstract: Five- and six-membered rings result from the chelation of nickel(II) by the dibasic tridentate Schiff base ligand, o-vanillin thiosemicarbazone(o-VTSC), a new chelate prepared and characterized. The structural results are discussed in the light of spectroscopic and other data.

Palladium(II) methylpyrazole complexes

Abstract: PdII complexes of the general formula PdL 2 n Cl2 [L1 = 3,4,5-trimethylpyrazole, L2 = l,3,4-trimethylpyrazole, L3 = 1,3,5-trimethylpyrazole, L4 = 1,4,5-trimethylpyrazole and L5 = 1,3,4,5-tetramethylpyrazole] (1)–(5) have been prepared and studied by elemental analyses, X-ray diffraction patterns, i.r., far-i.r. and n.m.r. spectroscopy, conductometry, magnetic and thermal measurements.

Magnetic measurements and spectral studies on copper(II) complexes of semicarbazones derived from isatin, benzoin and 2-hydroxy-naphthaldehyde

Abstract: The preparation and spectral properties of five copper(II) complexes of semicarbazones, derived from 2-hydroxy-naphthaldehyde (NPSCZ), benzoin (BZSCZ) and isatin (ISSCZ) are described. I.r., electronic, e.s.r. 1H and 13C n.m.r. spectra show that the semicarbazone's coordination is distorted trigonal bipyramidal for [Cu(BZSCZ-2H)(H2O)], distorted tetragonal pyramidal for [Cu(NPSCZ)2](ClO4)2 and dimeric for the other three complexes.

Nickel(II) and cobalt(II) complexes of 2,4-diaminothieno[2,3-d]-pyrimidines

Abstract: The reactions of methyl-2-amino-4-diethylamino thieno-[2,3-d]pyrimidine 6-carboxylate, methyl-2-amino-4-ethyl-phenylamine thieno-[2,3-d]pyrimidine-6-carboxylate) and methyl-2-amino, 4-morpholino-thieno-[2,3-d]pyrimidine-6-carboxylate with NiII and CoII halides produced complexes of the general formula ML2X2 (where L is thieno pyrimidine and X is Cl or Br). The complexes were characterized by elemental analyses, conductivity and magnetic susceptibility measurements and spectroscopy. All of the complexes were found to have pseudotetrahedral structures with the metal coordinated through the N(1) site of the thieno-[2,3-d]-pyrimidine.

Spectral and thermal properties of saccharin and saccharin metal complexes

Abstract: The photoacoustic spectra, i.r. spectra and d.t.a. curves of saccharin (o-sulphobenzoimide) and its transition metal complexes have been studied. It was found that saccharin, as a ligand, has three coordination modes (monodentate, η2-bridging or η2-chelating) and it can also act as a free anion without coordinating to the metal. The charge transfer spectra of saccharin and its complexes have also been studied; the results can be correlated with the coordination mode.

Rhodium(I) carbonyl complexes with sulphur and nitrogen donor ligands

Abstract: Rhodium(I) carbonyl complexes, namely [Rh(CO)2ClL] where L = thiourea (Tu), 1,3-diphenyl-2-thiourea (DTu), dithizone (Dtz), indole (Id), 3-chloropyridine (Clpy), 3-hydroxypyridine (HOpy), 3-methylpyridine (Mepy), 2,5-dimethylpyridine (Me2py) or 2,5-dichloropyridine (Cl2py)] were prepared. [Rh(CO)2Cl(Clpy)2] has also been isolated. In the (Tu) complex, ν(C-S) occurs at ca. 710cm-1, indicating the presence of a metal-sulphur bond. The carbonyl stretching frequencies in [Rh (CO)2ClL] and [Rh(CO)2CIL2] occur at ca. 2100−1990 and 1830−1800 cm-1, respectively. PPh3 reacts with the complexes to form trans-[Rh(CO)Cl(PPh3)2]. The complexes were characterized by elemental analyses, conductivity measurements and by their i.r. spectra.

O,O′-Alkylene dithiophosphate derivatives of iron(II) and iron(III) and their reactions with nitrogen- and phosphorus-donor bases

Abstract: Solids of the stoichiometric formulae [Fe{S2P(OPr-n)2}3] and [Fe{S2PO2G}3] (G = —CH2CMe2CH2—, CMe2−CMe2— or —CH2CH2CHMe—) are precipitated from the reactions of FeCl3 with ammonium dithiophosphates in water. Soluble complexes of the type [Fe{S2PO2G}2], formed by the reactions of FeCl2 with NH4[{S2PO2G}] in MeOH, can be extracted with benzene. Adducts of the types [Fe{S2PO2G}2L] and [Fe{S2PO2G}2(PPh3)2] are formed by the reaction of [Fe{S2PO2G}2] with L (L = 2,2′-bipyridyl or 1,10-phenanthroline) and PPh3, respectively. All the compounds have been characterized by i.r. and u.v.-vis. spectroscopy and magnetic studies.

Oxomolybdenum(V) complexes of bis-(2-benzimidazolyl) alkanes

Abstract: Oxomolybdenum(V) complexes of the type (LH4) [MoOCl5] (where LH2 = dimethylene bis-2-benzimidazole or tetramethylene bis-2-benzimidazole), [MoOCl3(LH2)] (where LH2 = tetramethylene bis-2-benzimidazole), [(Mo2O4Cl2-(H2O)3)2(LH2)] (where LH2 = dimethylene bis-2-benzimidazole, tetramethylene bis-2-benzimidazole or hexamethylene bis-2-benzimidazole) and [Mo2O3Cl4(LH2)2] (where LH2 = tetramethylene bis-5-nitro-2-benzimidazole) were prepared and characterised. The mononuclear complexes show u.v.-vis. absorptions characteristic of octahedral molybdenum(V). The dinuclear complexes do not absorb in the visible region, possibly due to the presence of an Mo2O42+} core, which is also indicated by their diamagnetic behaviour. The biological activities of the free ligands and their complexes have been studied.

Mononuclear manganese(III) aquo complexes. Crystal and molecular structures of [Mn(phen)(OH2)Cl3] and [Mn(acac)2-(OH2)2]ClO4·2H2O (acacH = acetylacetone, phen = 1,10-phenanthroline)

Abstract: The crystal and molecular structures of [Mn(phen)-(OH2)Cl3] (1) and [Mn(acac)2(OH2)2]ClO4·2H2O (2) were determined. A comparison is made of the Jahn-Teller distortion in these compounds with those observed in other manganese(III) complexes with monodentate axial ligands.

Synthesis and physicochemical studies on S-methyl-β-N-(ferrocenyl)methylenedithiocarbazate and its rare earth complexes

Abstract: A new ferrocene-containing thio-Schiff base, S-methyl-β-N-(ferrocenyl)methylenedithiocarbazate (FTSBH), was prepared by the condensation of formylferrocene with S-methyldithiocarbazate. Its rare earth complexes [Ln-(FTSB)3] (Ln = lanthanide) were also obtained, by the reaction of LnCl3 with the thio-Schiff base derivative in EtOH. The ligand coordinates to lanthanide(III) in its thioenol form. The complexes are nonelectrolytes in DMF, and are more thermostable than the ligands due to the formation of chelate rings.

Novel coordination compounds of quinic acid. X-ray diffraction study of copper(II) complexes where the metal ion was a chiral centre

Abstract: The synthesis and characterization of the following coordination compounds derived from quinic acid (quin) (1): [Cu(quin)Cl(H2O)]n·(H2O)n(2); [Ni(quin)Cl(H2O)]n·(2H2O) n (3); [Co(quin) Cl(H2O)]n·(2H2O)n(4); [Cu(quin) (NO3)(H2O)]n·(2H2O)n(5); [Cu(quin)(AcO)(H2O)]n· (2H2O)n(6); [Cu(quin)H2O]2·2H2O(7); [Co(quin)2]n (8); [Zn(quin)2](9); [Cd(quin)2](10) and [Hg(quin)2]· 4H2O (11) is presented. All of the compounds were characterized by i.r. and u.v. spectroscopy; in addition, (9) and (10) were analysed by n.m.r., and (2), (5) and (7) by X-ray crystallography. Due to the polyfunctionality of quinic acid diverse structures were obtained: (2) –(6) and (8) were polymeric, (7) was dimeric and (9) –(11) were spiranic. In compound (2) the Cu had a distorted octahedral structure; it was a chiral centre with six different substituents and an optically active ligand. Only one stereoisomer (OC-6-25-A) of the 30 possible was observed in the crystal. Compound (5) was also polymeric, the hexacoordinated Cu atom was a chiral centre (OC-6-53C) and only one stereoisomer was observed. It was bonded to three quinic acid ligands in three different coordination modes and each quinic acid was in turn bonded to three different Cu atoms. Each chain was linked to another two chains giving a net structure. Compound (7) was a dimer with two square pyramidal Cu atoms. Two apical water molecules were found in acis arrangement. Each quinic acid ligand was bonded to two Cu atoms which were linked by two oxygen bridges and each Cu atom was bonded to two quinic acid moieties.

Synthesis, spectroscopic and structural characterization of the mer isomer of ammonium bis(phenylpyruvic acid thiosemicarbazone)-cobalt(III) hemihydrate

Abstract: Phenyl pyruvate thiosemicarbazone (H2PPVATSC) coordinates in its binegative thiolate form to cobalt(III) in the complex isolated from basic medium. An X-ray structure determination of the resulting meridional isomer was found to contain mutually cis sulphur, trans nitrogen, and trans oxygen donor atoms, respectively. The two five-membered rings formed by each ligand are puckered towards each other, resulting in a distortion from regular octahedral geometry about the cobalt atom. The complex was found to exhibit only a metal-based one electron reversible reduction at -0.97 V, while the parent ligand yields a c.v. profile consisting of two irreversible reduction peaks at -0.75 and -1.05V respectively, the latter corresponding to the reduction of the azomethine group.

Synthesis, properties and structure of the vanadium(IV) Schiff base complex [VO(salphen)]· MeCN

Abstract: Et4NVO3 reacts with the Schiff baseN,N′-disalicylidene-o-phenylenediamine (salphenH2) in MeCN to afford [VO(salphen)]· MeCN, which has been characterized by elemental analysis, e.p.r., i.r. and electronic absorption spectra and conductance measurements. The X-ray single crystal structure revealed, that the metal was coordinated in a square pyramidal arrangement to the quadridentate ligand.

N -Ferrocenylcarbonyl- N ′-benzoylhydrazine and its transition metal(II) complexes

Abstract: A new ferrocene derivative, N-ferrocenylcarbonyl-N′-benzoylhydrazine (H2FB) and its transition metal complexes, [M(FB)]2·H2O (M = MnII, CoII, CuII, ZnII, CdII or HgII) and M(HFB)2·nH2O (M = MnII or CdII) were prepared by reacting H2FB with the metal(II) acetates and characterized by elemental analyses, i.r. and u.v. spectroscopy and t.g.a. H2FB appears to act as a tetradentate ligand, coordinating to the metal through the nitrogen enolic oxygen atoms.

Synthesis of novel heterobimetallic complexes of platinum(II) bridged by the mixed phosphine-phosphine oxide ligands Ph2P(CH2)2P(O)Ph2

Abstract: The mixed phosphine-phosphine oxides Ph2P(CH2)n-P(O)Ph2 (n = 1 or 2) react with K2PtCl4 to give cis-{PtCl2-η 1-Ph2P(CH2) n P(O)Ph2]2}. Treatment of the latter (n = 2) with transition metal chlorides MCl2·nH2O, or with Me2SnCl2, SnCl4·5H2O, Th(NO3)4·xH2O or UO2(NO3)2· 6H2O, gives novel heterobimetallic complexes identified as cis-{PtCl2[μ-Ph2P(CH2)2P(O)Ph2]2MX2}·nH2O. Attempts to prepare similar heterobimetallic complexes using the starting complexes {PtX2[η 1-Ph2PCH2P(O)-Ph2]2} (X = C1), cis- or CN, trans-] were unsuccessful. Possible reasons for this are discussed.