Coordination Of Metal Atoms Research Articles

Synthetic, Structural and Vibrational Spectroscopic Studies in Bismuth(III) Halide/N,N ′-Aromatic Bidentate Base Systems. III Some Novel Bismuth(III) Halide/N,N ′-Bidentate Ligand (1 : 1)

Syntheses and single-crystal room-temperature X-ray structure determinations are recorded for a number of adducts obtained by the crystallization of bismuth(III) halides with 2,2′-bipyridine (bpy) or 1,10- phenanthroline (phen) from dimethyl sulfoxide (dmso) solution. [(phen)BiX3(O-dmso)2].dmso, X = Cl, Br, are triclinic, P-1,a ≈ 14·6, b ≈ 9·7, c ≈ 9·5 Å, α ≈ 96, β ≈ 96, γ ≈ 98°, Z = 2; conventional R on | F| were 0·057, 0·037 for No 5775, 4847 independent ‘observed’ (I > 3σ(I)) reflections respectively. The metal atom coordination environments are seven-coordinate pentagonal bipyramidal with axial halides and the two O-dmso ligands cis in the equatorial plane. BiI3/phen/dmso (1 : 1 : 1 ) is orthorhombic, Pmc21, a 12·745(3), b 9·697(3), c 18·335(5) Å, Z = 4, R 0·049 for No 2012. The complex is ionic [(phen)BiI2(O-dmso)3]+[(phen)BiI4]-, the halide atoms being axial in a pentagonal bipyramidal array about the metal in the cation, with a quasi-octahedral coordination environment in the anion. With bpy, by contrast, BiI3/bpy/dmso (1 : 1 : 1) is obtained, orthorhombic, Pnma, a 17·86(2), b 12·87(1), c 8·47(1) Å, Z = 4, R 0·058 for No 1194, a neutral mononuclear complex [(bpy)BiI3(O-dmso)] with a six-coordinate array about the metal, O-dmso trans to an iodine atom. Bands in the far-infrared and Raman spectra due to the vibrations of the O2N2BiX3 cores in [(phen)BiX3(O-dmso)2] (X = Cl, Br) are assigned, and discussed in relation to the structures of the complexes.

Determination of structural parameters for the half-sandwich compounds cyclopentadienyl thallium and cyclopentadienyl indium and indium quadrupole coupling for cyclopentadienyl indium using microwave spectroscopy

Microwave rotational transitions for J′←J=2←1 and 3←2 were measured in the 7–11 GHz range for three isotopomers of (C5H5)In. Similar transitions (up to J′←J=5←4) for eight isotopomers of (C5H5)Tl were measured in the 5–15 GHz range. The rotational constants of the most abundant isotopomers are B(Cp 203Tl)=1467.9730(11) MHz, B(Cp 205Tl) =1465.0723(14) MHz, B(Cp 113In)=1809.9785(30) MHz, and B(Cp 115In)=1800.8199(18) MHz (Cp=C5H5). The quadrupole coupling strengths for the indium compounds are eQq(Cp 113In)=−118.397(69) MHz and eQq(Cp 115In)=−119.981(31) MHz. Spectra for single-substitution C13 isotopomers were seen in natural abundance. Deuterated samples of CpTl were prepared to obtain spectra for deuterium-substituted isotopomers. Analysis of the spectra allowed the determination of the following structural parameters; for (C5H5)Tl, r(Tl–C5)=2.413(3) Å, r(C–C)=1.421(10) Å, r(C–H)=1.082(9) Å and ∠C5–H=0.9(2)° (C5 represents the planar, 5-carbon ring of C5H5), and for (C5H5)In, r(In–C5)=2.314(4) Å and r(C–C)=1.426(6) Å. A Kraitchman analysis was performed on the available isotopomers for comparison of r0 and rs values. Both structural analyses indicate that the hydrogen atoms in (C5H5)Tl are bent slightly out of the carbon plane away from the coordinated metal atom.

Self‐Assembly of Copper(I) Halide Networks Containing Tetra‐ or Pentameric Ethylcycloarsoxane (C2H5AsO)n (m = 4,5) as a flexible Bridging Unit

AbstractIn complexes of ethylcycloarsoxane (C2H3AsO)n, the oligomer size n is influenced by the coordinated metal atom. Cyclic tetramers are observed in the porous sheet structures of ∞2[Cu2Br2{cyclo‐(C2H5AsO)4}3] (1) and 2∞ [Cu3I3{cyclo‐(C2H5As0)4)2] (2), prepared by the reaction of the appropriate copper(I) halide with (C2H5AsO)n in acetonitrile. Both complexes contain μ1κAs1:2κAs3‐coordinated (C2H5AsO)4 ligands as molecular bridging units between individual copper(I) centres leading to large respectively 36‐ and 40‐membered rings. An analogous bridging mode is found in the cyclic oligomers [cyclo‐(ReBr(CO)3{μ‐[cyclo‐(C2H5AsO)}}4](3) formed by reacting {ReBr(CO)5] with (C2H5AsO)n in refluxing toluene. – In contrast both [(NH4){cyclo‐ (C2H5AsO)5}2][Ag(SCN)]2 (4) and 2∞[(Cs(cyclo‐(C2H5‐AsO)3]2} Cu2(μ‐I)I2] (5) contain pentamers (C2H5AsO)5, which coordinate the NH+4 and Cs+ cations κ5O in a pentagonal antiprismatic fashion. In 5, prepared by self‐assembly from CsI, CuI, and (C2H5AsO)n in acetonitrile, [Cs[cyclo‐{C2H5AsO}5)2]+ sandwich cations are linked thorough μ‐1κAs1:2κAs2‐coordinated [Cu2l3]− units into polymeric chains. This coordination pattern reflects the unique ring size adaptability of the ambidentate (C2J5AsO)n ligand.

Syntheses and structural characterizations of novel tungsten and molybdenum complexes of fullerene [M(η2-C60)(CO)2(phen)(dbm)]· 2C6H6·C5H12 (M = W or Mo, phen = 1,10-phenanthroline, dbm = dibutyl maleate)

Novel tungsten and molybdenum complexes of fullerene [M(η2-C60)(CO)2(phen)(dbm)]·C6H6·C5H12 (M = W 1 or Mo 2; dbm = dibutyl maleate; phen = 1,10-phenanthroline) have been synthesized by heating a solution of C60 with [M(CO)4(phen)] and dbm in toluene followed by chromatography over silica gel. They have been characterized by chemical analysis, IR, UV/VIS, 1H and 13C NMR spectroscopy and single-crystal X-ray diffraction analysis. The complexes are isomorphous. The metal atom co-ordination is distorted octahedral with the two CO groups and phen in the equatorial plane and the metal binds in an η2 fashion to C–C bonds of C60 and dbm. Both complexes are remarkably stable in air and have unusually good solubility.

The surface chemistry of metal-oxygen interactions: a first-principles study of O:Rh(110)

We report on a computational study of the clean and oxygen-covered Rh(110) surface, based on density-functional theory within the local-density approximation. We have used plane-wave basis sets and Vanderbilt ultra-soft pseudopotentials. For the clean surface, we present results for the equilibrium structure, surface energy and surface stress of the unreconstructed and (1 × 2) reconstructed structures. For the oxygen-covered surface we have performed a geometry optimization at 0.5, 1, and 2 monolayer oxygen coverages, and we present results for the equilibrium configurations, workfunctions and oxygen chemisorption energies. At half monolayer coverage, we find that oxygen induces a (1 × 2) reconstruction of the surface, while at one monolayer coverage the chemisorption energy is highest for the unreconstructed surface. Our results are rationalized by a simple tight-binding description of the interaction between the O 2p orbitals and the metal valence states. The resulting bonds are stronger when established with low coordinated metal atoms, and give rise to an effective adsorbate-adsorbate interaction when two oxygen atoms are bound to the same metal orbital.

The coordination environment of Ag and Cu in ternary chalcogenide glasses

An analysis is made of the information provided by the method of isotopic substitution in neutron diffraction on the metal atom coordination environment in M-A-X glasses, where M denotes Ag or Cu, A a Group IVB or VB element, and X a chalcogen. It is found that the M-X coordination number is low (~ 3–4) but there is no clear correlation between its precise value and whether the material is a semiconductor or fast-ion conductor. When the concentration of M is high it is possible to measure the M-M partial pair distribution function g M-M(r) . In those systems for which results are available it is found that, irrespective of the electrical conductivity mechanism, short M-M nearest-neighbour distances are present. However, the first peak in g M-M(r) is more clearly defined in the case of semiconducting glasses.

Ab-initio X-ray powder diffraction structural characterization of co-ordination compounds: polymeric [{MX2(bipy)}n] complexes (M = Ni or Cu; X = Cl or Br; bipy = 4,4′-bipyridyl)

In the absence of crystals of suitable quality, the crystal structures of five [MX2(bipy)](M = Ni or Cu; X = Cl or Br; bipy = 4,4′-bipyridyl) phases were determined, ab initio, from powder diffraction data. The nickel compounds contain symmetrically bridging halides and trans-D4h octahedrally co-ordinated metal atoms; on the contrary, the co-ordination about the copper atoms in [CuBr2(bipy)] is square planar, with long Cu ⋯ Br contacts in the axial direction, due to Jahn–Teller distortion. Interestingly, [CuCl2(bipy)] is dimorphic; both in the orthorhombic and in the monoclinic phases, the copper co-ordination is substantially square planar as in the bromide analogue, but none of the two phases is isomorphous to it.

The structure of aurichalcite, (Cu,Zn)5(OH)6(CO3)2, determined from a microcrystal

Synchrotron radiation has allowed structure detn. by single-crystal methods using a flake of material 5 ?m thick from a specimen of the natural mineral, Pima County Arizona. The crystals are monoclinic and twinned. As in the related mineral hydrozincite, Zn5(OH)6(CO3)2 [Ghose ,1964], there are double layers of close-packed O atoms, with metal atoms in octahedral holes, as well as tetrahedrally coordinated metal atoms. In contrast to hydrozincite, there are also five-coordinate metal atoms. Alternate layers are linked only by hydrogen bonds and the metal coordination octahedra show strong tetragonal distortion. The tetrahedral sites are probably occupied by zinc, the other sites by zinc and copper. [on SciFinder(R)]

In situ NMR studies of hydrogen interaction with supported Ru-Group Ib bimetallic catalysts

An in situ NMR technique was employed to study hydrogen adsorption on silica supported Ru-Group Ib bimetallic catalysts at pressures up to one atmosphere. Two different hydrogen-on-metal resonances, α and β, were observed. Addition of silver to Ru was found to greatly diminish the relative amount of the weakly bound β hydrogen. Since silver preferentially populates edge, corner and other defect-like sites, the weakly bound β was correlated with low coordinated metal atoms. The total hydrogen population on the catalyst remains approximately the same with the addition of copper. The difference in catalytic behavior of Ru, Ru-Cu and Ru-Ag is postulated to be due to the surface segregation induced structure sensitivity of the weakly bound β hydrogen.

Synthesis and characterization of (Zn,M) 2P 2O 7 (M = Mn,Cu)

Characterization of powder samples of Zn 2− x M x P 2O 7 (M = Mn, Cu; x = 0–2) shows that substitution of small amounts of Cu or Mn into low temperature or α-Zn 2P 2O 7 stabilizes a solid form isostructural with β-Zn 2P 2O 7, the high temperature form. Single crystal X-ray analysis of ZnCuP 2O 7; monoclinic space group C2/ m, a = 6.741(5), b = 8.190(4), c = 4.542(3), β = 107.72(5)°, D calc = 4.210 g cm −3, Z = 2, R = 6.6% for 353 observed reflections; shows mixed metal sites with 50% occupancy each of Zn and Cu. Octahedrally coordinated metal atoms lie on planes in hexagonal array with two oxygen atoms bridging adjacent metal sites. Magnetic susceptibility measurements of ZnMP 2O 7, M = Mn, Cu show antiferromagnetic interactions between cations which are stronger for M = Cu.

Structure of the microporous titanosilicate ETS-10

INORGANIC microporous framework solids such as zeolites are of considerable technological importance as shape-selective catalysts, ion-exchange materials and molecular sieves1. Most microporous materials known until recently were silicates, aluminosilicates1 or aluminophosphates2–4, all of which contain tetrahedrally coordinated metal atoms. In 1989, a family of microporous titanosilicates (generically denoted ETS) was discovered in which the metal atoms (Ti4+) are octahedrally coordinated5–8. A full understanding of the potential of any microporous solid to act as a molecular sieve and selective catalyst, and of the nature of the catalytic centres, requires that its structure be known. But that of the ETS materials has proved elusive because of the considerable degree of disorder that they contain. Using a combination of high-resolution electron microscopy, electron and powder X-ray diffraction, solid-state NMR, molecular modelling and chemical analysis, we have now been able to solve the structure of a prominent member of this family, ETS-10. This structure comprises corner-sharing SiO4 tetrahedra and TiO6 octahedra linked through bridging oxygen atoms. The pore system contains 12-membered rings and displays a considerable degree of disorder. Many ordered variants of ETS-10 exist, some of which are chiral.

Synthesis and Crystal Structure of Cd(H2O)2Ni(CN)4 · 4H2O

Single crystals of Cd(H2O)2Ni(CN)4 · 4H2O have been synthesized and characterized by single-crystal X-ray diffraction. The crystallographic data are as follows: orthorhombic space group Pnma , a = 12.393(2) Å, b = 14.278(5) Å, c = 7.427(1) Å, Z = 4; R = 0.033, wR = 0.042 for 949 reflections. This material is similar to the Hofmann-type clathrates; it is structurally composed of two-dimensional sheets of alternating square planar and octahedrally coordinated metal atoms bridged by cyanide ligands. However, unlike Hofmann-type clathrates for which structures have been reported, this material does not contain ammonia, amines, or a clathrated aromatic molecule between the metal tetracyanonickelate sheets. Instead, the interlayer regions are filled by a distorted hexagonal hydrogen-bonded net of water molecules.

Base hydrolysis of aqueous chromium(III) solutions: on the existence of [Cr(OH)4]–, and speculation regarding a new chromium polyoxocation

The base hydrolysis of chromium(III) aqueous solutions was investigated in an attempt to determine whether a [CrO4Cr12(OH)24(H2O)12]7+ polyoxocation (i.e. Cr13) analogous to the tridecameric aluminium and gallium ions (Al13 and Ga13) is formed. Clay mineral intercalation studies showed that a species formed during base hydrolysis of aqueous solutions of Cr3+ has approximately the same height, relativer to the phyllosilicate sheets, as that of the Ga13 polyoxocations. Gel permeation chromatography of the hydrolysed solution revealed that a chromium species was eluted at exactly the same volume as were the other tridecameric ions, under analoguous conditions. These results indicate that a chromium ion similar in size to that of the know [GaO4Ga12(OH)24(H2O)12]7+ does form during base hydrolysis. Quantitative pillaring studies also suggested that the chromium species has a similar charge. Infrared studies of sulfate salts formed from the chromium-containing cations present in the hydrolysed solutions indicated that no tetrahedrally coordinated chromium was present; this implies that the chromium species cannot be analoguous to the Al13 and Ga13 polyoxocations as they both contain a central tetrahedrally co-ordinated metal atom. Since this tetrahedral central atom in the tridecamers has been postulated to arise because of the existence of [M(OH)4]x– ions in solution at high pH, its apparent absence in the case of chromium led to an investigation of whether or not [Cr(OH)4]– ions, the formation of which has generally been assumed, really exist. Through ultraviolet-visible and near-infrared spectroscopic studes, as well as the analysis of titration curves, it is concluded that no [Cr(OH)4]– ions are formated upon hydrolysis of solutions of Cr3+ to OH–:Cr3+ mole ratios of 4:1. For these reasons it is speculated that the large species present in hydrolysed chromium solutions may be [Cr12(OH)28(H2O)12]8+ ions in which the central tetrahedral position is vacant.

Organotransition-metal metallacarboranes. 30. Tetradecker metallacarborane sandwiches: synthesis via double-decker stacking and structural characterization of Co-Co-Co, cobalt-nickel-cobalt, and cobalt-ruthenium-cobalt complexes

Stacking reactions of the bridge-deprotonated Cp*Co(2,3-Et[sub 2]C[sub 2]B[sub 3]H[sub 3]-5X)[sup [minus]] complexes (X = Cl, Br, CH[sub 3], C(O)CH[sub 3], CH[sub 2]C[triple bond]CCH[sub 3], H; Cp* = [eta][sup 5]-C[sub 5]Me[sub 5]) with cobalt(II) and nickel(II) halides in THF gave, respectively, diamagnetic [Cp*Co[sup III](Et[sub 2]C[sub 2]B[sub 3]H[sub 2]X)][sub 2]Ni[sup IV] and paramagnetic [Cp*Co[sup III](Et[sub 2]C[sub 2]B[sub 3]H[sub x]X)][sub 2]Co[sup IV] tetradecker sandwich complexes. A similar reaction of the B(5)-chloro reagent using RuCl[sub 2] gave the diamagnetic trichloro complex (Cp*Co)[sub 2](2,3-Et[sub 2]C[sub 2]B[sub 3]H[sub 2]-5-Cl)(2,3-Et[sub 2]C[sub 2]B[sub 3]H-4,5[5,6]-Cl[sub 2])Ru. In all cases except the Co-Co-Co compound (X = H), the products were isolated as dark crystalline solids via chromatography on silica; decomposes on silica and was isolated via fractional crystallization from a cold solution. All of the tetradeckers are air-stable in the solid state and in solution except 3f, which is stable only as a solid. Characterization of these compounds was based on [sup 1]H, [sup 11]B, and [sup 13]C NMR (for diamagnetic species), UV-visible, and mass spectra, supported by x-ray crystallographic data on the Co-Ni-Co and Co-Co-Co dichloro compounds, the Co-Ni-Co diacetyl complex, and the Co-Ru-Co sandwich. The structurally characterized compounds are tetradecker sandwiches, slightly bent in the middle (8-15[degree]) butmore » exhibiting no significant ring slippage relative to the coordinated metal atoms. The carborane rings in these sandwiches are mutually rotated by 27-89[degree]. The electronic spectra exhibit intense absorption bands between 350 and 440 nm with extinction coefficients between 28,000 and 43,000 M[sup [minus]1] cm[sup [minus]1].« less

Synthesis, structure, and magnetic properties of diphenylphosphinates of cobalt(II) and manganese(II). The crystal and molecular structures of the γ forms of poly-bis(μ-diphenylphosphinato)cobalt(II) and manganese(II)

The synthesis of the β and γ forms of M(Ph2PO2)2 where M = Co and Mn are described and the compounds are characterized by infrared spectroscopy, differential scanning calorimetry, X-ray powder diffraction, and low-temperature (2–80 K) magnetic susceptibility studies. Single crystal X-ray diffraction studies are reported on the γ forms. Crystals of the γ forms of poly-bis(μ-diphenylphosphinato)cobalt(II) and poly-bis(μ-diphenylphosphinato)manganese(II) are isomorphous, crystallizing with 4 formula units per unit-cell in the monoclinic space group P21/c. Lattice constants are a = 8.080(2), 8.161(1), b = 23.550(6), 23.751(1), c = 11.726(3), 11.6946(6) Ǻ, and β = 92.88(2), 93.026(8)° for the Co and Mn derivatives respectively. The structures were solved by heavy atom methods and were refined by full-matrix least-squares procedures to R = 0.039 and 0.045 for 4041 and 2878 reflections with I ≥ 3σ(I), respectively. Both crystal structures consist of double phosphinate-bridged chain polymers containing tetrahedrally coordinated metal atoms: Co—O = 1.950(2)–1.963(2) Ǻ, O—Co—O = 104.81(8)–117.77(9)°, Mn—O = 2.016(3)–2.033(3) Ǻ, O—Mn—O = 103.2(1)–114.7(1)°. All four compounds exhibit antiferromagnetic coupling and magnetic susceptibilities have been analyzed according to two Heisenberg models for linear chains of metal ions with S = 3/2 for cobalt and S = 5/2 for manganese. The Weng model (with values for the Wagner and Friedberg model in parentheses) gives –J = 0.25 (0.26) cm−1 and 0.55 (0.60) cm−1 for the β and γ forms, respectively, of Co(Ph2PO2)2, and 0.34 (0.36) cm−1 and 0.17 (0.17) cm−1 for the β and γ forms, respectively, of Mn(Ph2PO2)2. Key words: crystal structure, diphenylphosphinates of cobalt(II) and manganese(II), magnetic properties.

Preparation and characterization of new transition metal complexes of nitroimidazoles. X-Ray crystal structures of two copper complexes: bis-[(μ-chloro)chloro-bis-(1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole)copper(II)] and dichloro-bis-(2-methyl-s-nitroimidazole)copper(II). First observation of nitro group coordination to the metal ion in these heterocycles

2-Methyl-5-nitroimidazole [MNIH, ( 1)] forms the complexes Cu(MNIH) 2X 2 [X = Cl ( 1a), Br ( 1b), NO 3 ( 1C), OH ( 1d)] and Co(MNIH) 2X 2 [X = Cl ( 1e), OAc ( 1f)]. X-ray crystal structure of 1a shows a distorted octahedral geometry for the copper(II) ion bonded to two chlorine atoms and two nitroimidazole molecules through N(1) and with a trans diaxial coordination to one of the oxygen atoms of the nitro groups. This is the first example of nitroimidazole derivatives in which the nitro group occupies a coordination site. Spectroscopic evidence suggests that for compounds 1b–1f the preferred coordination site for the metal ion is N(1), with interaction of the nitro group adjacent to it, giving extra stability to the complexes. The copper complexes, 1b and 1c, contain six coordinated metal atoms, while 1e is tetrahedral and 1f is a carboxylate-bridged dimer. The other ligand, 1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole [metronidazole, HEMNI ( 2)] forms the complexes Cu(HEMNI) 2X 2[X = Cl ( 2a, 2b), Br ( 2c), OAc ( 2d)] and Co(HEMNI) 2Cl 2 ( 2e). An X-ray crystal structure determination on Cu(HEMNI) 2Cl 2 ( 2a shows a centrosymmetric chlorobridged dimer. The coordination geometry around each copper atom is trigonal bipyramidal with three equatorial chlorine atoms and two axial imidazole molecules. The rest of the metronidazole complexes obtained were shown to be a dimeric compound with bridging acetates, 2d, two monomeric octahedral (X = Cl, Br) copper compounds, 2b and 2c, and a tetrahedral cobalt compound, 2e.

Synthesis of conformational isomers, thermally induced isomerism, and crystal structure of cis-di-isothiocyanatobis(N-methylpropane-1,3-diamine)nickel(II)

Two isomers, (1) and (1a), of [NiL2(NCS)2](L =N-methylpropane-1,3-diamine) have been synthesised. Isomer (1) undergoes an irreversible endothermic solid-state phase transition (383–413 K, ΔH= 8.1 kJ mol–1) transforming into species (1a). This isomerisation also takes place on crystallisation from methanol, ethanol, chloroform, or acetonitrile. Species (1a) has been characterised by X-ray crystallography. The crystals are monoclinic, space group P21/c with four formula units in a unit cell of dimensions a= 8.136(2), b= 13.057(2), c= 15.235(3)A, and β= 90.75(1)°. The structure has been solved by Patterson and successive Fourier syntheses and refined by block-diagonal least-squares calculations to R= 0.048 and R′= 0.061 for 2 311 reflections. The metal atom co-ordination is nearly octahedral with the two thiocyanate groups in cis position. The overall configuration and conformation of the complex molecule is Λpp(two chairs fold in the same rotational direction). Isomer (1) probably exists in the Λpa form (two chairs fold apart from each other).

Synthesis and molecular structure of a bis[di(alkyl)alanyl]methane; R 2ALCH 2AIR 2 [R = CH(SiMe 3) 2

Reaction of Cl 2AlCH 2AlCl 2 with lithium-bis(trimethylsilyl)methyl in n-pentane yields [(Me 3Si) 2CH] 2AlCH 2Al[CH(SiMe 3) 2] 2 ( 1), the first stable organometallic derivative of the starting tetrahalide. The crystal structure of 1 shows monomeric molecules with two trigonal planar coordinated metal atoms. The coordination sphere of the central carbon atom deviates significantly from tetrahedral geometry with an AlCAl angle of 129.6°. Further experiments for the synthesis of methylene bridged dialanes were not successful with R = mesityl, tert-butyl, tris(trimethylsilyl)methyl and trimethylsilyl.

Tetraphenylphosphonium-hexachlorodizinkat und -hexachlorodicadmat, (PPh4)2Zn2Cl6 und (PPh4)2Cd2Cl6 / Tetraphenylphosphonium Hexachlorodizincate and Hexachlorodicadmate, (PPh4)2Zn2Cl6 and (PPh4)2Cd2Cl6

The title compounds were obtained by the reactions of PPh4Cl, HCl and ZnS or CdS in CH2Cl2. Their crystal structures were determined by X-ray diffraction. (PPh4)2Zn2Cl6: a = 973.6(1). b = 982.6(2), c = 1296.7(3) pm, α = 107.93(2), β = 94.50(2), γ = 100.91(2)°, R = 0.036 for 2237 unique observed reflexions. (PPh4)2Cd2Cl6: a = 977.1(2), b = 997.5(3). c = 1306.6(3) pm. α = 108.81(2), β = 94.18(2), γ = 100.24(2)°, R = 0.050 for 1921 reflexions. Both compounds are isotypic in the triclinic space group P1̄ and consist of PPh4 + ions and dimeric, centrosymmetric M2Cl6 - ions in which the tetrahedrally coordinated metal atoms are linked via chloro bridges.

Multinuclear magnetic resonance studies of the hydrolysis of aluminium(III). Part 9. Prolonged hydrolysis with aluminium metal monitored at very high magnetic field

Aluminium(III) salt solutions hydrolysed by boiling with aluminium metal over extended periods of time have been examined by 27Al n.m.r. spectroscopy and, after drying and redissolution in acetone, by 1H n.m.r. spectroscopy, both at very high magnetic field. At low hydrolysis ratios, m⩽ 1.4(where m is defined by the stoicheiometric formula AlX3–m(OH)m, X being the coanion), the solutions contain the oligomer species observed in base hydrolysis. There are three minor components and one major one whose spectroscopic properties suggest it is the 3,8 trimeric species [Al3O2(OH)4(H2O)8]+. The fully hydrolysed solutions (m= 2.5) have complex proton spectra which differ between preparations and it is concluded that they contain a hierarchy of species whose structures are related to that of the tridecameric cation but many of which lack the tetrahedrally co-ordinated metal atom. It is not possible to suggest a structure for any individual species but it is made clear for the first time that a wide range of products are formed in these solutions.