Showing papers in "Polyhedron in 1984"

Abstract: INTRODUCTION 1037 1. CYCLOMETALLATION 1038 1.1 General introduction 1038 1.2 Synthesis of cyclometallated species. 1038 1.3 Mechanistic considerations. 1040 1.4 Theligands 1040

Abstract: Etude de la double liaison dans des composes tels que: les disilenes, diphosphenes, digermenes, distannenes, phosphaarsenes, diarsenes, a partir des spectres IR, RMN, electroniques et des calculs d'orbitales moleculaires

Abstract: A method is described for constructing qualitatively the molecular orbitals of an approximately spherical cluster of boron or transition-metal atoms. The method gives a way of understanding the electron-counting rules for such clusters, the preference for deltahedral structures, the relationship between closo boranes on the one hand and nido and arachno boranes on the other, and Mingos' capping and condensation principles for transition-metal clusters.

Abstract: Some five- and six-coordinated di and tri-n-butyl tin(IV) semi- and thio-semi carbazates have been synthesized. The characterization of these complexes, by IR, NMR (1H, 13C, 119Sn), 119Sn), 119Sn Mossbauer and Mass spectroscopies along with X-ray diffraction, reveals that complexes of biionic ligands of the type Bu2Sn L″ are five-coordinated having trigonal bipyramidal geometry. However, complexes of monoionic ligands of the type Bu2SnL′2 are six-coordinated in a distorted cis-octahedral geometry and Bu3SnL′ are five-coordinated with a trigonal bipyramidal structure. X-ray structural studies on the compound Bu2Sn(O.C6H4.CH:N.N.CS.NH2), show that it crystallizes in a monoclinic lattice with a = 16.90 A, b = 9.71 A, c = 8.60 A, and β = 103°45′.

Abstract: New complexes of lanthanide nitrates with 4N-(2′-hydroxy benzylidene)-aminoantipyrine (HBAAP) having the general formula [Ln(HBAAP) 2 (NO 3 ) 3 ] (where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y) have been prepared and characterized. Conductance studies indicate non-electrolytic behaviour for these complexes. Their infrared spectra show that both the ligand and the nitrate group are bound to the metal ion in a bidentate fashion. Electronic spectra indicate weak covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to ∼200°C and undergo complete decomposition in the range 200–550° resulting in the formation of the stable lanthanide oxides.

Abstract: Dissolution of HgO or PbO in methanolic solutions of NaSPh yields homogeneous solutions from which highly crystalline [NBun4][Hg(SPh)3] (1) or [NPrn4][PB(SPh)3] (2) can be isolated on addition of appropriate quaternary ammonium salts. 1 crystallizes in monoclinic space group P21/a with a = 20.663(7), b = 16.812(6), c = 9.757(3) A, β = 95.52(2)° and Z = 4. The anion consists of a rare example of trigonal planar coordinated Hg; there are no weaker, intermolecular Hg ... S axial interactions. 2 crystallizes in triclinic space group Pl with a = 12.689(7), b = 11.255(6), c = 12.046(7) A, α = 107.93(3), β = 109.64(3), γ = 86.01(3)°, and Z = 2. The anion consists of a trigonal pyramidal coordinated PbS3 unit. The structures were solved using data collected at approx. − 160°C and refined to conventional R values of 5.7 and 4.6%, respectively for 1 and 2.

Abstract: Recently a number of high nuclearity gold cluster compounds of the type [Au(AuPR3)n]x+ have been synthesised and structurally characterised using single crystal X-ray crystallographic measurements. The structures and properties of these compounds are contrasted with those of comparable high nuclearity metal carbonyl cluster compounds. In order to account for the structures of [Au(AuPR3)n]x+ in the solid state and in solution it has proved necessary to develop a flexible bonding model which emphasises the topologies of the clusters rather than their detailed geometries. In this fashion the observed stereochemical non-rigidity of these compounds in solution is readily accounted for. In the solid state the structures of the higher nuclearity cluster cations can be derived either from the centred chair [Au(AuPR3)6], or the centred crown [Au(AuPR3)8] by adding edge or face capping AuPR3 fragments. The bonding in heterometallic clusters containing the AuPR3 fragment is also considered.

Abstract: Detailed spectroscopic and scattering investigations of isopoly-molybdate and -tungstate solutions as a function of concentration and pH were made. From scattering results the apparent molecular weights were determined as a function of time and concentration. We find that the results agree with the aggregation scheme of simple + hepta + octa + (Mo,O,,A -8 + protonated polymeric species, for molybdate solutions. Tungstate solutions aggregate according to simple - Y-polytungstate - paratungstate-A - paratungstate-B - Ik-metatungstate. The molybdate solutions ex- hibited very rapid equilibration, but the tungstate solutions required several days to reach equilibrium. From the discrete changes in the Raman spectra of both systems we find that the formation of isopoly anions is not a continuous process and that only certain species are present in solution. Our results do not rule out the formation of significant quantities of the octamolybdate anion as suggested by previous investigators.

Abstract: The structures of dicyclohexyl-(18-crown-6) uranyl perchlorate, [(C20H36O6)UO2] (ClO4)2 (complex I) and of dicyclohexyl-(18-crown-6) uranyl hydroxyperchlorate [C20H36O6]3 [(UO2)2(H2O)6] · (ClO4)2, CH3CN, (complex II) have been determined from three dimension X-ray diffraction data. The uranyl group is directly coordinated to the oxygen atoms of the polyether ring in complex I; its hydrolysis (complex II) leads to a dimerization of the uranyl ions by sharing two OH groups with an U-U distance of only 3.827(8) A. The polyether molecules are connected by hydrogen bonds with the dimeric ion [(UO2)2 (OH)2 (H2O)6]2+.

Abstract: The title organic ligands (Hsip) gave, by reaction with d10-metal acetates, complexes of the type M(sip)2 (M = Zn, Cd, Hg), in which the ligand behaved as terdentate, producing a distorted octahedral environment around the metal. The 1H and 13C chemical shifts found for these complexes in DMSO are compared with the corresponding ones of the free ligand. The crystal structure of the zinc derivative has been determined from diffractometer data to R = 0.072 for 1086 independent reflections. Crystals are monoclinic, space group C2/c, with unit-cell dimensions a = 18.193(2), b = 24.532(6), c = 11.535(2) A,β = 103.71(1)° and Z = 8. Coordination occurs through the carbonyl oxygens (Zn−O = 2.10, 2.16(1) A), the azomethine nitrogens (Zn−N = 2.04, 2.07(1) A) and the pyridine nitrogen s(Zn−N = 2.24, 2.26(1) A).

Abstract: Preparations are described of several monometallic complexes (bipym)PtR 2 [bipym = 2,2′-bipyrimidyl; R = Me, CF 3 , Ph, 1-adamantylmethyl (adme); R 2 = (CH 2 ) 4 ] and bimetallic analogues R 2 Pt(μ-bipym)PtR′ 2 [R = R′ = CH 3 , C 6 H 5 , adme; R = CH 3 , R′ = Ph, adme, CF 3 ]. IR, 1 H NMR and UV/visible spectroscopic characteristics of the two modes of bipyrimidyl coordination are discussed.

Abstract: A series of Cu(II) complexes of the thiosemicarbazone, 3-azabicyclo[3.2.2]-nonene-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide(HL) and the corresponding N-oxide (HLO) have been prepared and characterized. Both ligands undergo deprotonation and appear to coordinate via the thione sulfur, the imine nitrogen and the pyridyl nitrogen (or N-oxide oxygen). A single anionic ligand such as Cl−, Br−, NCS− and N−3 completes the bonding to the Cu(II) center of these 4-coordinate complexes. When the complexes are prepared using Cu(II) perchlorate, the solids isolated contain a neutral thiosemicarbazone ligand as well as the deprotonated ligand. The solids are primarily characterized by IR, electronic and electron spin resonance spectroscopy. In addition, electronic and ESR spectra of their chloroform solutions were recorded. Most of the solids (except the nitrates) were unaltered upon dissolution. Simulation of the solution ESR spectra was used to estimate the coupling constants of the various coordinated nuclei.

Abstract: p -Anisaldehyde thiosemicarbazone (PAT) has been used to isolate the complex compounds of the general formula [M(PAT)X 2 ]H 2 O where M(II) = Zn, Hg, Cd and Cu, and X = Cl or 1 2 SO 4 . Probable structures for the complex compounds have been proposed on the basis of elemental analysis, conductometric, spectral and magnetic susceptibility data. The toxicity of the isolated complexes and ligand has been evaluated on pathogenic fungus.

Abstract: Yellow (Et4N)[Cu5(SBut)6] crystallises from solutions prepared from Cu(II), ButSH, Et3N and Et4NBr in acetone/ethanol, while (Et3NH)[Cu5(SBut)6] crystallises from solutions of CuSBut and ButSH in Et3N. Crystal structure determinations reveal that both compounds contain the molecular cage [Cu5(μ-SBut)6]−, in which two copper atoms are three-coordinate (Cutrig), three copper atoms are two-coordinate (Cudig), and all thiolate ligands are doubly-bridging. The polyhedral stereochemistry of the core is trigonal bipyramido-Cu5-trigonal antiprismo-S6. The complete [Cu5(μ-SBut)6]− cage in the Et4N+ compound closely approaches D3 symmetry, but in the Et3NH+ compound one SBut ligand is inverted at the sulphur bridge, causing angular distortions in the cage. Two structural features, the antiprismatic twist of the S6 polyhedron and the bending of Cudig towards the cage centroid (S-Cudig-S = 171(1)°), provide evidence for weak Cu-Cu attractive interactions within the cage. Infrared data are discussed. Crystal data: (Et4N)[Cu5(SBut)6], C32H74Cu5NS6, a = 45.500 (3), b = 11.805(1), c = 20.168(2) A, β = 117.81 (1)°, C2/c, Z = 8, R = 0.078 (2953 observed F); (Et3NH)[Cu5(SBut)6], C30H70Cu5NS6, a = 10.519(1), b = 21.457(1), c = 20.065(1), β = 95.11(1), P21/c, Z = 4, R = 0.072 (3093 observed F). (Et4N)[Ag5(SBut)6] is isostructural with (Et4N)[Cu5(SBut)6].

Abstract: The synthesis and characterization of a number of cis -dioxomolybdenum(VI) coordination complexes involving tridentate (ONS) ligands is described. The Schiff base ligands were obtained by condensation of 5-substituted salicylaldehydes with o -aminobenzenethiol or 2-aminoethanethiol. The chemical properties of these molybdenum complexes are compared with those having tridentate ligands with the ONO donor atom set. Cyclic voltammetry was used to obtain cathodic reduction potentials ( E p c ) for the irreversible reduction of the Mo(VI) complexes. Although the reductions are irreversible, trends are observed in E p c both within each series and when different series are compared. Cathodic reduction potentials for the four series examined span the range from −1.53 to −1.05 V versus NHE. There are three ligand features whose effect systematically alters the Mo(VI) cathodic reduction potentials. These include (1) the X-substituent on the salicylaldehyde portion of each ligand; (2) the degree of ligand delocalization; and (3) the substitution of a sulphur donor atom for an oxygen donor atom. Each of these effects is considered separately with regard to the Mo(VI) cathodic reduction potentials and then their cumulative effect is described.

Abstract: The crystal and molecular structures of the title compound have been determined by single crystal X-ray diffraction methods. In the spiro molecule, the metal atom has a geometry very close to tetrahedral, with OTiO angles of 107.9–111.0(2)° and very short TiO bonds of length 1.777–1.791(5)A. The two TiO5Si4 rings have different, ill-defined conformations; the SiO bond lengths and SiOSi angles are similar to those in (SiO)n rings.

Abstract: New copper(II) complexes of general formula, Cu(ONS)B (ONS = the di-negatively charged Schiff base, S-benzyl-β-N-(2-hydroxyphenyl) methylendithiocarbazate; B = pyridine, 2,2′-dipyridyl or 1,10-phenanthroline) have been synthesized and characterised by magnetic and spectroscopic measurements. The complex, Cu(ONS)py is four-coordinate and square-planar. Magnetic and spectroscopic data support a five-coordinate, presumably, a trigonal-bipyramidal structure for the [Cu(ONS)dipy] and (Cu(ONS)phen] complexes

Abstract: This paper considers whether satisfactory localized 2- and 3-centre bond schemes may be devized for real or hypothetical clusters BnHnc− (c = 0, 2 or 4; n = 4 → 12) or isoelectronic analogues thereof, with closo deltahedral shapes. As expected, localized bond schemes can be devized for all the species that would be predicted, using MO approaches, to have closed shell electronic configurations: these include species BnH2− (n = 5 → 12) and BnHnc− (c = 0 or 4; n = 4, 8, 9 or 11). There is also generally good agreement with MO treatments as to which systems are not expected to be stable: these include B4H42− and BnHnc− (c = 0 or 4; n = 5, 7 or 10). Localized bond treatments have value for estimating the bond orders of cluster bonds in species BnHn and BnHn2−, though they overestimate the bond orders in species BnHn4− (except when n = 4). They are misleading, when applied to octahedral and icosahedral systems, in indicating the former shape to be feasible for hypothetical species B6H6 and B6H64−, and the latter shape to be feasible for hypothetical species B12H12 and B12H124−.

Abstract: The complexes Ni6(MPDMA)12, [Ni6(MPDMAH)12]X12 X = (I, ClO4) and Pd2(MPDMA)2Cl2 (MPDMA = t-S(CH2)3N(CH3)2) have been prepared and characterized. An X-ray diffraction study shows that the structure of [Ni6(MPDMAH)12] (ClO4)12 consists of a cyclic hexanuclear array of nickel atoms linked by sulphur bridging ligands. Infrared and electronic spectra show that there is no chelation in any of the nickel complexes. However, coordination through the nitrogen atoms occurs in the palladium complex. This behaviour differs from that of the homologous β-mercaptoamine, which forms monomeric chelate complexes with both nickel and palladium.

Abstract: Yellow oxo(diperoxo)bipyridylmolybdenum(VI), C10H8MoN2O5, Mr = 332.1 crystallizes in the monoclinic space group P21/n, a = 6.261(3), b = 12.726(1) c = 13.752(3)A, β = 91.84(2)°, V = 1095.2(5)A3, Z = 4, Dc = 2.014(1) g/cm3, MoKα(λ = 0.7107A), μ = 11.8 cm−1, T = 22(1)°C, R = 0.034, ωR = 0.040, number of reflections in least squares (F0 > 2σ(F0)) = 1125. The molybdenum coordination (distorted trigonal bipyramidal) is as in the corresponding chromium complex, C10H8CrN2O5 which has closely similar bond angles but is not isomorphous. The difference in MoNapex and MoNeq bond distances (2.312(5) and 2.199(5)A) is similar to that in the CrNapex and CrNeq distances (2.23(2) and 2.11(2)A). The MO distances for each peroxo ligand (ave. 1.910(2) and 1.950(2)A) are significantly different and slightly longer than those in the chromium complex as is the OO distance of 1.459(6)A. The latter is indicative of greater negative charge on the O2 ligands, approaching that of O2−2 in the molybdenum complex.

Abstract: New nickel(II), copper(II), cobalt(III) and rohdium(III) complexes of two Schiff base ligands formed by condensation of furfural and benzil with S-benzyldithiocarbazate have been synthesized and characterized by elemental analysis and magnetic and spectroscopic measurements. The nickel(II) complexes, Ni(NS)2 and Ni(ONS)2 (NS and ONS stand for the uninegatively charged furfural and benzil Schiff bases, respectively) are square-planar and octahedral, respectively. The Cu(NS)Cl complex is paramagnetic with a magnetic moment fo 1.73 B.M. A halogen-bridged dimeric structure is proposed for this complex. The copper(II) complex, Cu(ONS)Cl is diamagnetic, suggesting strong antiferromagnetic interactions between a pair of copper(II) ions in a thiolo sulphur-bridged dimeric or polymeric structure. Cobalt(II) ions are oxidized in the presence of the Schiff bases with the concomitant formation of cobalt(III) complexes of empirical formulae, Co(NS)3, Co(ONS)2ClO4 and Co(ONS)2Cl, respectively, which are spin-paired and octahedral. The rhodium(III) complex of the furfural Schiff base, Rh(NS)2Cl is tentatively assigned a halogen-bridged dimeric structre.

Abstract: The synthesis of 1,4-dimethyl-2,3,5,6-tetra- n -alkyl-1,4-diboracyclohexa-2,5-dienes from the reaction of di- n -alkylacetylenes with the methylborylene-generating system 2C 8 K/MeBBr 2 is described. A mechanism for these reactions is proposed. The addition of methylborylene to di- t -butylacetylene results in the formation of 1-methyl-2,3-di- t -butylborirene and of 1,3-dimethyl-2,4-di- t -butyl-1,3-diboretene.

Abstract: On various types of heteropolyanion (HPA) and isopolyanion (IPA), there are some closed loops, each of which is formed by a junction of M ion and bridging oxygens (edge-sharing and/or corner-sharing). By using the structural stability index defined as the number of loops per MO6 octahedral unit, the relative stability, the degree of condensation, the interconversion, and the formation of heteropoly blue anions of HPA and IPA can be clarified.

Abstract: The structures of the [Mo6(μ3-Cl)8(OMe)6]2− and [Mo6(μ3-OMe)8(OMe)6]2− anions have been determined and reveal interesting comparisons of MM and MO distances with related Mo6(μ3-X)84+ containing compounds and polynuclear alkoxides of molybdenum.

Abstract: The compounds [Ir(CO)2(η-C5Me5)] and [Pt(C2H4)3] in diethylether at 0°C react to give the cluster complex [Ir3Pt3(μ-CO)3(CO)3(η-C5Me5)3] in quantitative yield. The structure of the hexanuclear metal species was established by X-ray diffraction. The main feature is a near-planar array of metal atoms with a central triangle of platinum atoms [PtPt (mean), 2.703(3) A] each edge-bridged by an iridium atom [IrPt (mean) 2.667(3) A]. The iridium atoms are each ligated by an η5-C5Me5 group and by two CO ligands. Three of the latter are essentially terminally bound to Ir and lie approximately orthogonal to the Ir3Pt3 plane, and three bridge between Pt and Ir and lie close to the hexametal plane. The 13C-{1H&} NMR data for the cluster reveal that the carbonyl groups and η5-C5Me5 ligands undergo dynamic behaviour in solution and possible mechanisms for ligand site exchange are discussed.

Abstract: The covalent derivatives [Et2M-PEt2]3 (M = Ga, In) have been prepared from Lewis acid-base complexes, R3M.PHEt2, by alkane elimination and characterized by elemental analyses, IR, 1H and 31P NMR spectroscopy. Features of the mass spectra reveal a trimeric form and the strength of the [M-P]n ring. For the compound [ClMeGa-PEt2]n, spectral data are consistent with a weakening of the [Ga-P]n chain, in good agreement with the pyrolysis results.

Abstract: O,O-Alkylenedithiophosphates of diorganotin(IV) of the type R2Sn[SP(S)O2G]2 (R = Me, Et, n-Bu, Ph; G = CH2CMe2CH2, CMe2CMe2, CMe2CH2CHMe) have been synthesized by the reactions of diorganotin(IV) dichlorides with ammonium O,O-alkylenedithiophosphates or that of diorganotin(IV) oxides with O,O-alkylenedithiophosphoric acids in 1:2 molar ratio in benzene. These new complexes are white solids which are soluble in common organic solvents and are monomeric in refluxing benzene; and they have been characterized by elemental analysis and by different spectroscopic (IR, 1H, 13C, 31P and 119Sn NMR) studies, on the basis of which a six coordinated octahedral structure has been suggested in solution.

Abstract: Tris(alkylenedithiophosphates) of arsenic(III), antimony(III) and bismuth(III), have been synthesized by the reactions of alkylenedithiophosphoric acids with metal oxides and chlorides and of their ammonium salts with metal chlorides in suitable solvents Mixed chloride alkylenedithiophosphates of arsenic(III) and antimony(III), have been obtained by the reactions of metal chlorides with ammonium alkylenedithiophosphates at 1 : 1 and 1 : 2 molar ratios or alternatively by the co-disproportionations reactions of metal chlorides with metal tris(alkylenedithiophosphates) at different (2 : 1 and 1 : 2) molar ratios These new compounds have been characterized by elemental analyses, molecular weight measurements and spectroscopic (IR, and 1H and 31P NMR) data Chelated structures with bidentate alkylenedithiophosphate groups have been proposed for all these derivatives

Abstract: Several complexes of 5,8-diethyl-7-hydroxy-6-dodecanone oxime [H 2 L] with Cu(II) and Ni(II) have been synthesized and characterized by means of a number of techniques including elemental analysis, IR spectra, magnetic susceptibility measurements, electronic absorption spectra, NMR spectra, and mass spectra. The results indicate that Cu(II) and Ni(II) generally form analogous, isomorphous complexes, although no bis-[H 2 L] complex with Cu(II) has been isolated. [Cu(L)] n and [Ni(L)] n are oligomeric complexes with pseudo-octahedral geometry. [Ni(HL) 2 ] is cis -square-planar (C 2ν ) with bifurcated hydrogen bridges. [Ni(H 2 L) 3 SO 4 ] and [Cu(H 2 L) 3 SO 4 ] have octahedral symmetry in which the sulphate is coordinated as a unidentate ligand and the oxime is functioning as a neutral ligand.