Showing papers in "Journal of Coordination Chemistry in 1982"
TL;DR: In this article, it was shown that the conversion of the bis-napthaldehyde complex to the Schiff-base complexes is accompanied by an inversion of the eπ∗ and b 1∗ energy levels.
Abstract: Oxovanadium(IV) complexes of 2-hydroxy-1-naphthaldehyde and the Schiff-base complexes [VO{OC10H8CH=N—CR1R2—(CH2) n–1—N=CHC10H8O}] where n = 2 (R1 = R2 = H or CH3) and n = 3–8 (R1 = R2 = H) along with the corresponding ligands have been synthesised and characterised by elemental analysis, i.r. and electronic spectral and magnetic susceptibility measurements. There is evidence that the conversion of the bis-napthaldehyde complex to the Schiff-base complexes is accompanied by an inversion of the eπ∗ and b 1∗ energy levels. Moreover, the introduction of a second phenyl ring results in a reduction of the in-plane ligand field. The v(V=O) frequencies suggest that the complexes are five-coordinate, except VO(naph2-tn) which is likely to be six-coordinate and polymeric. Although the magnetic moments at room temperature for the complexes vary between 1.59 and 1.77 B.M. the variation of the moments with temperature is not appreciable.
31 citations
TL;DR: In this paper, the distortions of a number of bipyridine complexes with the trans geometry are analyzed and found to fall into two categories, bowed or twisted, and the two complexes of this report were found to have a bowed conformation.
Abstract: The cation trans -[Ru(bpy) 2 (PPh 3 ) 2 ] 2+ and trans -[Ru(Me 2 bpy 2 ) 2 (py) 2 ] 2+ both contain bipyridine ligands which are distorted because of the crowding of the two chelate units. The hexafluorophosphate salt of the first cation crystallizers in space group P2 1 /n, with a = 11.630(1), b = 20.245(2), c = 11.299(1)A, β = 103.99(1)°, and Z = 2. R = 0.047 for 2396 observed reflections. The hexafluorophosphate salt of the second cation crystallizers in space group C2/m, with a = 18.392(2), b = 11.265(1), c = 13.383(1)A, β = 139.42(2)°, and Z = 2. R = 0.047 for 1403 observed reflections. The Ru of the first cation lies on an inversion center and the Ru of the second cation lies on a special position of 2/m symmetry. The distortions of a number of bipyridine complexes with the trans geometry are analyzed and found to fall into two categories, bowed or twisted. The two complexes of this report were found to have a bowed conformation.
22 citations
TL;DR: In this paper, the position of the vanadium atom was determined on the basis of the distribution of Patterson function, coordinates of the other atoms were determined by Fourier synthesis, and absorption spectra of the ammonium and ligand were calculated from the measured reflectance spectra by the application of Kubelka-Munk theory.
Abstract: Crystals of ammonium (salicylaldehyde S-methylthiosemicarbazonato)dioxovanadate(V)monohydrate, NH4[VO2L]·H2O were synthesized from ammonia–ethanol solution of VCl3 and salicylaldehyde S-methylthiosemicarbazone (H2L). They belong to the monocyclic system, space group P21/c, a, = 5.864(2), b = 16.382(7), c = 13.931(5)A, β = 97.60(3)°, Dm = 1.62, Dc = 1.63. The position of the vanadium atom was determined on the basis of the distribution of Patterson function, coordinates of the other atoms on the basis of Fourier synthesis. Vanadium occurs in the complex within the VO2 + group, lacking d-electrons. The coordination polyhedron has the form of a deformed square pyramid. The bands in infrared spectrum indicate the existence of valence oscillations of O=V=O group. Absorption spectra of the complex and ligand were calculated from the measured reflectance spectra by the application of Kubelka-Munk theory. Two out of the seven absorption maxima in the spectrum, result from intraligand transitions and the ...
20 citations
TL;DR: In this paper, the synthesis and characterization of mixed ligand complexes of platinum(II) with amino acids as primary ligands and purine and pyrimidine bases as secondary ligands are reported.
Abstract: The synthesis and characterization of mixed ligand complexes of platinum(II) with amino acids as primary ligands and purine and pyrimidine bases as secondary ligands are reported. The interaction of platinum(II) glycine and alanine complexes with purine and pyrimidine, carried out in a 1 : 1 ratio resulted in the formation of mixed ligand complexes. In these complexes adenine and guanine are coordinated to the metal ion through N(7) whereas hypoxanthine acts as a bridging ligand coordinating through N(3) and N(9). The pyrimidines are coordinated to the metal ion through N(3). In all the mixed ligand complexes the amino acids behave as monodentate ligands coordinating through amino nitrogen.
20 citations
TL;DR: In this article, the infrared data of three isomeric compounds of the composition Cu(II)-NCO−-3,4,5-trimethylpyrazole (tmpz) system were isolated.
Abstract: From the Cu(II)-NCO−-3,4,5-trimethylpyrazole (tmpz) system three isomeric compounds of the composition Cu(NCO)2.2tmpz and one compound of the composition Cu(NCO)2.tmpz were isolated. According to the infrared data two of the 1 : 1 compounds consist of Cu(tmpz.NCO)2 complexes, comprising 3,4,5-trimethyl-1-carbamoylpyrazolate anions as chelate ligands, while the third represents the cyanato complex Cu(NCO)2(tmpz)2. This type of isomerism might be designated as coligand isomersm. The 1 : 1 compound exhibits terminally bonded as well as bridging NCO ligands. The ligand field spectra indicate that one of the compounds Cu(tmpz.NCO)2 shows a square-planar configuration while the second differs by axial interactions between the basic structure units. Cu(NCO)2(tmpz)2 shows a molecular pseudotetrahedral structure and Cu(NCO)2(tmpz) has also a pseudotetrahedral but polymeric structure. The g values from the ESR spectra strongly support the above structure conclusions.
16 citations
TL;DR: In this paper, the authors reported the electronic absorption and CD spectra for the sexidentate [Rh(1,3-pdta)]− complex and assigned the A configuration by comparison of its CD spectrum to that of trans(O5)-[Rh(S, S-edds)]− known to have the α configuration from the stereospecificity of the S, Sedds ligand.
Abstract: Electronic absorption and CD spectra are reported for the sexidentate [Rh(1,3-pdta)]− complex (1,3-pdta = 1,3-propanediaminetetraacetate ion). The (-)D isomer of the [Rh(1,3-pdta)]− complex is assigned the A configuration by comparison of its CD spectrum to that of trans(O5)-[Rh(S, S-edds)]− known to have the A configuration from the stereospecificity of the S, S-edds ligand (S, S-edds = (S, S)-ethylenediamine-N, N-disuccinate ion).
7 citations
TL;DR: In this article, the formation of violurato complexes of Cr(III) has been studied in aqueous solution, and the acidity constants of this species have been determined: pKa1 = 3.32, pKa2 = 4.25,pKa3 =4.83 and pKa4 =6.99.
Abstract: The formation of violurato complexes of Cr(III) has been studied in aqueous solution. Two compounds, [Cr(H2V)3].5H2O and Na[Cr(H2V)2(OH)2].4H2O have been synthesized and characterized. [Cr(H2V)3] behaves in aqueous solution as a triprotic acid but it can also add a proton yielding [Cr(H2V)2(H3V)]+. The acidity constants of this species have been determined: pKa1 =3.32, pKa2 =4.25, pKa3 =4.83 and pKa4 =6.99 (25°C, 0.1 M NaC1O4). [Cr(H2V)2(OH)2]− undergoes a deprotonation of the two H2V− ligands and a protonation of the hydroxo ligands. The acidity constants of [Cr(H2V)2(H2O)2]+ have been also determined: pKa1 =3.5, pKa2 =4.6, pKa3 =7.1 and pKa4 =9.2 (25°C, 0.1 M NaC1O4). The coordination of a violuric acid molecule as a neutral ligand is reported for the first time.
7 citations
TL;DR: Several iron(II, III) complexes of N, N-di(2-)pyridyl thiourea have been synthesized as discussed by the authors, and the Moumlssbauer, electronic and infrared spectra of these complexes have been measured.
Abstract: Several iron(II, III) complexes of N, N'-di(2-)pyridyl thiourea have been synthesized. The preparation of the complexes from iron(III) salts proceeds through a reduction of iron(III) to iron(II) followed by a subsequent reoxidation. The Moumlssbauer, electronic and infrared spectra of these complexes have been measured. The results are concordant with the coordination of pyridine nitrogens and thiocarbonyl sulfur yielding polymeric complexes. A variable temperature NMR study of the free ligand shows that two conformation are accessible for it in solution at subambient temperatures.
7 citations
TL;DR: In this article, the EPR spectra of a catalytic solution of cobalt dimethyl glyoxime dihydrate with amines were measured and the presence of nitrobenzene considerably alters the spectra, and it was shown that electron transfer from cobaloximes to TCNE is only possible in the case of PhNO2.
Abstract: Reaction of cobalt dimethylglyoxime dihydrate with amines gives rise to a catalyst for hydrogenation of nitrobenzene. Solutions of this catalyst in acetone are paramagnetic and EPR spectra of these solutions were measured. The presence of nitrobenzene considerably alters the EPR spectra. It was also observed that electron transfer from cobaloximes to TCNE is only possible in the presence of PhNO2. Changes of the EPR spectra during catalytic process were observed and interpreted.
5 citations
TL;DR: In this article, a 1 : 3, 1 : 2 and 1 : 1 metal ion to ligand ratios have been obtained for bidentate and coordination occurs through carbonyl oxygen and terminal nitrogen.
Abstract: Cr(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pd(II) complexes have been prepared with formylhydrazide employing the chloride, bromide, iodide, sulphate, perchlorate, thiocyanate and nitrate salts. Complexes having 1 : 3, 1 : 2 and 1 : 1 metal ion to ligand ratios have been isolated. Characterization has been accomplished by elemental analyses, magnetic moment, conductance and spectra (visible, i.r. and far-i.r.). The ligand is bidentate and coordination occurs through carbonyl oxygen and terminal nitrogen.
5 citations
TL;DR: In this article, the thermodynamic and kinetic condition of complex formation with 3d5-3d10 transition metal ions and structural features of the resulting complexes are investigated. But although ligands such as phenylalanine contain aromatic substituent groups that appear to interact with metal ions, particularly copper ion, they do not promote significant stereoselectivity in simple binary complexes.
Abstract: The coordination chemistry of amino acids and peptides is of considerable interest, due to its biological importance. In the case of glycine and phenylalanine, extensive studies have been made of the thermodynamic and kinetic condition of complex formation with 3d5-3d10 transition metal ions and of structural features of the resulting complexes.1–6 Fairly abundant knowledge is available on the complexes of glycylphenylalanine with transition metal ions, primarily, copper(II), zinc(II) and nickel(II).1,7–9 Because of their roles in the storage and transport in the neurotransmitters,10 attention has been focused on the study of the interactions with transition metal ions.11 It is interesting to note that although ligands such as phenylalanine, glycyl-phenylalanine and glycyl-tyrosine contain aromatic substituent groups that appear to interact with metal ions, particularly copper ion, they do not promote significant stereoselectivity in simple binary complexes.11,12 However, there is evidence that i...
TL;DR: A copper core of two histidines, a cysteine and a methionine is proposed for rusticyanin with a tighter chelate loop structure in the C-terminal region than is found in plastocyanin and azurin.
Abstract: The copper-binding regions of plastocyanins and azurins are examined by the Chou-Fasman method. Similar structural features are found in the proposed copper-binding site for stellacyanin. These structural features are related to the copper-ligand bond lengths and to the reduction potentials of the blue copper proteins. The range of reduction potentials observed in these proteins is considered to be a function of the chelating peptide loop sizes and of the nature of the amino acid side chains in the loop region. A copper core of two histidines, a cysteine and a methionine is proposed for rusticyanin with a tighter chelate loop structure in the C-terminal region than is found in plastocyanin and azurin.
TL;DR: In this article, the anation of β-cis-[Co(trien)(OH2)2]3+ ion by oxalic acid, bioxalate anion and oxalate dianion has been studied at 30-45°C and I = 1.0 M (KNO3).
Abstract: The anation of β-cis-[Co(trien)(OH2)2]3+ ion by oxalic acid, bioxalate anion and oxalate dianion has been studied at 30–45°C and I = 1.0 M (KNO3). The common anation rate constant, k 0, of {β-cis-[Co(trien)(OH2)2]3+, H2C2O4} and {β-cis-[Co(trien)(OH2)2]3+, HC2O4 −} ion-pairs is found to be 6.7 × 10−5 sec−1 at 40°C. The observed anation rate constant levels off to a limiting value (7.0 (·0.8) X 10−3, sec−1) at 40°C, pH = 4.00 (·0.05) and [C2O4 2-] ± 0.15 M, which is characteristic of the anation rate constant (k 1) of the oxalate dianion ion-pair. Activation enthalpy and entropy for the k 0 and k 1, paths are 24.5 K.cal mole−1, 0.8 cal. deg−1 mole−1 and 28.9 K.cal mole−1, 24.0 cal. deg−1 mole−1, respectively. The temperature independent ion-pair equilibrium constant for H2C2O4 ion-pair was found to be 6.8 (·1.2) M−1. The anation of {β-cis-[Co(trien)(OH2)2]3+-X} ion pairs (X = H2C2O4, HC2O4 − or C2C4 2-) is believed to involve an ‘Id’ mechanism.
TL;DR: In this paper, the ESR spectra of seventeen oxovanadium(IV) β-diketonates in chloroform solution have been examined in order to study the effect of various substituents.
Abstract: The ESR spectra of seventeen oxovanadium(IV) β-diketonates in chloroform solution have been examined in order to study the effect of various substituents. Bis[4,4,4-trifluoro-1-(3-pyridyl)-1,3-butanedionato]oxovadium(IV) which is tetrameric in chloroform solution gave an ESR spectrum suggestive of a species with a long rotation correlation time. Both 3-chloro and 3-methyl substituents increase the in-plane ligand field in VO(3-Clacac)2 and VO(3-CH3acac)2 while p-methoxyphenyl substituent which has the highest possible mesomeric interaction among the substituents gave the lowest isotropic splitting factor.
TL;DR: In this paper, the acid dissociation constant of sulphadiazene and the stability constants of the chelates have been determined, and the thermodynamic parameters of the complexes have been calculated.
Abstract: pH-Metric studies of the Coordination complexes of sulphadiazene with Cd(II), Co(II), Cu(II), Mn(II), Ni(II) and Pb(II) have been made. The acid dissociation constant of sulphadiazene and the stability constants of the chelates have been determined. The thermodynamic parameters of the complexes have been calculated.
TL;DR: The term ligand was first proposed by Alfred Stock (1876-1946) in the published version of a lecture on the hydrides of silicon presented at Berlin on November 27,1916 before the Kaiser-Wilhelm-Institut fur Chemie.
Abstract: The term ligand, which occurs so frequently in the pages of this journal, was first proposed by Alfred Stock (1876–1946) in the published version of a lecture on the hydrides of silicon presented at Berlin on November 27,1916 before the Kaiser-Wilhelm-Institut fur Chemie.
TL;DR: In this paper, the isolation of 1 : 2 manganese(I1) chloride and thiocyanate complexes with 4-cyanopyridine N-oxide (4-CPO) which are shown from room temperature magnetic moments, electronic spectral, ligand field parameters and i.r.
Abstract: Although high-spin and some low-spin octahedrally coordinated anionic and neutral complexes of manganese(I1) are common, tetrahedral coordination manganese(11) is mainly exhibited' in anionic species [MnX4l2-, X =CI, Br, CN, NCO, NCS or NCSe. Whereas manganese(I1) bromide is known to form neutral four-coordinated structures1 MnL, Br, L =Me, NO, C5H5N0, Ph, PO or Ph3As0, four-coordinated tetrahedral manganese(II) complexes as neutral species involving coordinated chloro- and thiocyanato-groups, MnL2X2 (L =a monodentate ligand, and X =C1 or NCS) are rather unknown. We report the isolation of 1 : 2 manganese(I1) chloride and thiocyanate complexes with 4-cyanopyridine N-oxide (4-CPO) which are shown from room temperature magnetic moments, electronic spectral, ligand field parameters and i.r. spectral studies down to 200 cm-' as neutral species exhibiting four-coordinated high-spin, monomeric tetrahedral environments around manganese(II) containing coordinated chloro- and thiocyanato- groups in the so...
TL;DR: The synthesis of functionally substituted (OMe, -NMe2, -SMe) organobismuthine ligands is described in this article, where the 1H nmr and mass spectra of these ligands are reported and discussed.
Abstract: The synthesis of functionally substituted (OMe, -NMe2, -SMe) organobismuthine ligands -specifically (o-MeOC6H4)3Bi, (o-MeSC6H4)3Bi, (o-Me2NC6H4)3Bi, (o-MeOC6H4)Ph2Bi, (o-MeSC6H4)Ph2Bi, (o-Me2NC6H4)Ph2Bi, is described. (o-Chlorophenyl)diphenylbismuthine reacts with sodium diphenylstibide (NaSbPh2) to give (o-diphenylstibinophenyl)diphenylbismuthine o-C6H4(SbPh2)(BiPh2). The 1H nmr and mass spectra of these ligands, and of (o-MeC6H4)3Bi and (p-MeC6H4)3Bi are reported and discussed.