Showing papers in "Journal of The Chemical Society A: Inorganic, Physical, Theoretical in 1968"

Hydroformylation of alkenes by use of rhodium complex catalysts

Abstract: The use of complexes of rhodium of the type trans-RhX(CO)(PR3)2, (X = halogen, R = aryl) as hydroformylation catalysts for alkenes is studied. It is shown that an inhibition period is removed by addition of hydrogen halide acceptors and that the halide complex undergoes hydrogenolysis to form a hydrido-species. The hydrido-species is only one of several complexes in equilibrium but it appears that the principal active catalytic species is RhH(CO)2(PPh3)2. This species is formed by addition of carbon monoxide to the monocarbonyl complex RhH(CO)(PPh3)2. The latter is also formed by dissociation when the stable crystalline complex RhH(CO)(PPh3)3 is dissolved in benzene or other solvents. With RhH(CO)(PPh3)3 as catalyst, alkenes undergo rapid hydroformylation even at 25°/1 atm.; with alk-1-enes the ratio of straight- to branched-chain aldehyde formed is considerably higher than the ratios normally found in hydroformylation reactions, being ca. 20 at 25°. Hydrogen atom exchange and isomerisation reactions of alkenes with RhH(CO)(PPh3)3 are described.

The electronic properties and stereochemistry of the copper(II) ion. Part I. Bis(ethylenediamine)copper(II) complexes

Abstract: The electronic properties and i.r. spectra of a series of bis(ethylenediamine)copper(II) complexes are reported. From a gaussian analysis of the electronic spectra, measured at room temperature and at the temperature of liquid nitrogen, of the seven complexes of known crystal structure, and three transitions 2A1gâ†�2B1g, 2B2gâ†�2B1g, and 2Egâ†�2B1g in D4h symmetry are tentatively assigned. From the e.s.r. spectra of polycrystalline samples of the complexes, which yield tetragonal spectra, the values of (g‖– 2)/(g⊥– 2) have been determined. Where the ratio is 4·0 the observed g-values are considered to reflect approximately the local copper(II) ion g-values. In the latter case the g-values have been combined with the appropriate electronic transitions and the orbital reduction factors k⊥ and k‖ evaluated. From the i.r. spectra of the polyanions, an infrared criterion is established for recognising the presence of weakly co-ordinated polyanions in the long tetragonal positions above and below the [Cu en2]2+ cation. The term semi-co-ordination is introduced to describe this structural situation.

The chemistry of pernitrites. Part I. Kinetics of decomposition of pernitrous acid

Abstract: The kinetics of decomposition of pernitrite in excess of alkali have been studies at several temperatures. These show that decomposition occurs through the pernitrous acid molecule, HO·ONO, with ΔH‡= 12·5 kcal. mole–1 and ΔS‡= 26 e.u. The value of ΔH‡ is not consistent with the accepted view that pernitrous acid decomposes via homolytic fission of the O–O link. This problem is discussed and other, non-homolytic, mechanisms suggested. An upper limit for the pKA of pernitrous acid at 2° of 8·3 has been calculated. The first isolation of a solid pernitrite is reported. The extinction coefficient of the pernitrite anion at 302 mµ(λmax.) has been redetermined as 1670 ± 50.

Crystal structure of β-copper phthalocyanine

Abstract: The crystal structure of the β-polymorph of copper phthalocyanine has been determined from three-dimensional X-ray diffraction data. A total of 1691 structure amplitudes was used in the refinement which resulted in R= 7·3% and standard deviation of bond lengths of 0·005 A. The structure is isomorphous with those of the metal-free1 and nickel2 phthalocyanines.

The reaction of hydridocarbonyltris(triphenylphosphine)rhodium with carbon monoxide, and of the reaction products, hydridodicarbonylbis(triphenylphosphine)rhodium and dimeric species, with hydrogen

Abstract: A detailed study has been made, using infrared and nuclear magnetic resonance techniques, of the interaction of carbon monoxide and hydridocarbonyltris(triphenylphosphine)rhodium(I), RhH(CO)(PPh3)3. The latter, which dissociates in solution to the square complex trans-RhH(CO)PPh3)2, initially forms the dicarbonyl complex RhH(CO)2(PPh3)2; in the presence of CO, this species loses hydrogen to give a yellow dimeric complex (Ph3P)2(CO)Rh(CO)2Rh(CO)(PPh3)2. These reactions are reversed by hydrogen to re-form RhH(CO)(PPh3)2. By sweeping with an inert gas, the yellow dimer loses carbon monoxide to form a red, solvated dimer, (Ph3P)2(S)Rh(CO)2Rh(S)(PPh3)2, which reacts with carbon monoxide to re-form the yellow dimer.

The preparation and reactions of hydridochlorotris(triphenylphosphine)ruthenium(II) including homogeneous catalytic hydrogenation of alk-1-enes

Abstract: The complex hydridochlorotris(triphenylphosphine)ruthenium(II) as a benzene solvate, RuClH(PPh3)3,C6H6, has been obtained by the interaction of the dichloride, RuCl2(PPh3)3, with molecular hydrogen at ambient temperature pressure in the presence of a base such as triethylamine; other preparative methods are described. The corresponding bromide, RuBrH(PPh3)3,C6H6, has been prepared. From the chloride by interaction with norbornadiene and 2,2′-bipyridyl, the complexes RuClH(C7H8)(PPh3)2 and [RuClH(bipyr)(PPh3)2]2 respectively have been obtained; the complex RuH2(CO)(PPh3)3 has also been prepared.The complex RuClH(PPh3)3 is the most active catalyst yet discovered for the homogeneous hydrogenation of alk-1-enes in benzene or toluene solution. The interaction is highly specific and rates for other types of alkene are slower by a factor of at least 2 × 103. The inherent difficulties of the system however preclude detailed kinetic study and it is shown that slow poisoning of the catalyst occurs under hydrogenation conditions.N.m.r. studies of the hydrido-complex and its deuteride have allowed hydrogen atom exchange studies to be made. Isomerisation of alkenes is studied. The slow exchange between molecular hydrogen and the α-proton of a phenyl group on the phosphine is demonstrated.

Reactions of gases in solution. Part III. Some reactions of nitrous oxide with transition-metal complexes

Abstract: Nitrous oxide reacts rapidly in solution at room temperature and at atmospheric pressure with a number of transition-metal complexes. It reacts with the cobalt(I) corrin, vitamin B12s, in aqueous solution according to the stoicheiometry 2CoI+ N2O → 2CoII+ N2 and with [CoI(Ph2P·CH2·CH2·PPh2)2]Br in benzene or ethanol according to the stoicheiometry 2CoI+ N2O → N2. The cobalt dimethylglyoxime, bipyridyl, and corrin complexes act as catalysts for the reduction of N2O to N2 by borohydride. In contrast to previous reports we find that acidified aqueous solutions of TiCl3 do not reduce N2O.

Exchange reactions of oxides. Part IX

Abstract: The kinetics of exchange of oxygen-18 between enriched oxygen gas and 38 inorganic oxides and 1 oxy-acid salt has been examined in detail. Most of the exchange reactions occur by a dissociative atomic mechanism confined to the surface layer of oxygen ions. For these there is a strong compensation effect between A0 and E in the rate expression: E shows a systematic fall with increasing size of the unit-crystal cell and related crystal parameters: the plots separate the oxides into structure-dependent groups. The slow stage is the desorption of oxygen. The oxides PbO, PdO, AgO, and CuO exchange the surface layer by a molecular reaction which also occurs to an appreciable extent, together with the atomic mechanism, on a number of other oxides. Na2WO4, V2O5, MoO3, and WO3 exchange the whole of the bulk oxygen with the gas phase by a combination of both mechanisms. SiO2 and GeO2 are inactive. Possible mechanisms for the two main reactions are discussed.

Complexes of osmium, ruthenium, rhenium, and iridium halides with some tertiary monophosphines and monoarsines

Abstract: The preparation and some physical properties of complexes of the types [MX3L3] where M = Re, Ru, or Os and [MX4L2] where M = Re, Os, or Ir and L = tertiary monophosphines are described. A few tertiary monoarsine analogues are also included.

Solvent effects on the energy of electronic transitions: experimental observations and applications to structural problems of excited molecules

Abstract: Experimental observations about solvent shifts of absorption bands are reviewed, and correlations with various solvent properties are discussed. The theory is treated according to the Onsager model of dielectrics which shows how data like dipole moments and polarizabilities of excited states can be obtained from solvent-shift experiments. Shifts resulting from dispersion interaction and from specific solvent–solute interaction, in particular hydrogen bonding, are considered. Possible improvements in the theory of solvent shifts are briefly discussed.

Prototropic equilibria of electronically excited molecules. Part II. 3-, 6-, and 7-Hydroxyquinoline

Abstract: The absorption and the emission spectra of the four ionic species formed by 3-, 6-, and 7-hydroxyquinoline in aqueous solution have been measured, and the constants governing the prototropic equilibria between the ionic forms of each compound in the lowest singlet excited state have been estimated theoretically from the transition energies and experimentally from the change in fluorescence spectrum with hydrogen-ion concentration. It is found that the phenolic group of the hydroxyquinolines is more acidic, and the ring nitrogen atom more basic, in the excited than in the ground electronic state, as expected from the theoretical electronic charge redistribution on excitation derived from a corresponding-carbanion model. The overall velocity of the two-stage prototropic change in the excited state from the neutral molecule to the zwitterion of the hydroxyquinolines in ethanol or neutral aqueous solution is found to be slower than the rate of emission, but the corresponding one-stage processes in acid or alkaline solution are comparable in rate or faster.

Amido-derivatives of metals and metalloids. Part VI. Reactions of titanium(IV), zirconium(IV), and hafnium(IV) amides with protic compounds

Abstract: The reactions of metal (Ti, Zr, or Hf) dialkylamides with acidic hydrocarbons (such as C5H6), hexamethyldisilazane, alcohols, and thiols are reported. In this way, numerous π-organometallic derivatives, such as CpTi(NMe2)3 and (π-C5H5)2Zr(NMe2)2, silylamides, alkoxides, and thiolates have been prepared. Noteworthy are (a) differences (possibly steric in origin), with regard to the number of groups displaced, between Ti amides and amides of either Zr or Hf, (b) the displacement order NR2 > SR > Cp ≫ OR, and (c) the monomeric nature of all the products. Reactions between decaborane and either Ti(NMe2)4 or Me3SnNMe2 afforded Ti(NMe2)4,2B10H14 and Me3SnNMe2,B10H14, which are probably best formulated as [Ti(NMe2)2]2+[B10H13,Me2NH]2– and [Me3Sn]+[B10H13,Me2NH]–, respectively.

Reaction of metal ion complexes with hydrocarbons. Part I. ‘Palladation’ and some other new electrophilic substitution reactions. The preparation of palladium(I)

Abstract: A survey has been made to identify those metal ions that will displace hydrogen ions from benzene with formation of arylmetal complexes. Certain stable complexes were isolated while the formation of thermally unstable complexes was detected by the appearance of biphenyl. An isotopic tracer method was used to seek hydrolytically unstable complexes. Gold(III), mercury(II), and thallium(III) react with benzene in aqueous acid solution while gold(III), mercury(II), palladium(II), platinum(II), and thallium(III) react in acetic acid solution. Reactivity is associated with ‘class b’ character. A more detailed study of the reaction of diacetatopalladium with benzene and toluene in 0·5N-perchloric acid in acetic acid was made. It appears to be an electrophilic substitution that yields arylpalladium complexes. These decompose by a concerted mechanism to give biaryls and either palladium metal or a univalent palladium complex depending on temperature. An explosive purple complex, [Pd(C6H6)(H2O)ClO4]n has been isolated. The ultraviolet absorption of this compound at 380 and 550 mµ has been used to determine its rate of appearance in solution during the reaction of benzene with diacetato-palladium in perchloric acid–acetic acid at 50°. The kinetic data are consistent with a second-order reaction between benzene and monomeric palladium(II)(k2= 4·6 × 10–4l.mole–1sec.–1) followed by fast decomposition. For deuteriobenzene, a large primary isotope effect (kH/kD= 5·0) was found.

The chemistry of co-ordinated ligands. Part II. Iron tricarbonyl complexes of some cyclohexadienes

Abstract: Some cyclohexa-1,4-dienes substituted by methyl and/or methoxyl groups react with iron carbonyls to give mixtures of tricarbonylcyclohexa-1,3-dieneiron complexes, whose compositions have been investigated. These complexes react with triphenylmethyl fluoroborate to give tricarbonyl-π-cyclohexadienyliron fluoroborates, whose reactions with nucleophiles are described. Certain of these salts, derived from methoxy-substituted cyclohexadiene complexes, are readily hydrolysed to tricarbonylcyclohexa-2,4-dienoneiron and substituted derivatives of this compound. Spectra are discussed in relation to structural assignments.

Chemistry of soil minerals. Part V. Low temperature hydrothermal transformations of kaolinite

Abstract: Raw kaolinite has been investigated as a possible starting material for low-temperature hydrothermal growth of zeolites and felspathoids. It proved to be convenient and versatile in this role, being readily transformed into a range of known and new zeolites and salt-inclusion felspathoids with a Si/Al ratio around 1·0, some of which have novel properties. Experiments were conducted at 80° using aqueous solutions of lithium, sodium, potassium, rubidium, and caesium hydroxides, sometimes in the presence of additional alkali-stable anions. Some quantitative aspects of the recrystallization reactions are discussed, as are the chemical and physical properties of representative compounds of each type synthesized.

Viscosity B-coefficients between 5° and 20° for glycolamide, glycine, and N-methylated glycines in aqueous solution

Abstract: The significance of viscosity B-coefficients for solutions of dipolar ions and non-electrolytes in water is discussed in the light of hydrodynamic theories of viscosity and the usefulness of the ratio B/Φ°2(Φ°2 is the limiting apparent molar volume of the solute) is stressed. Viscosity and density measurements have been made at 5°, 10°, 15°, and 20° on aqueous solutions of glycolamide, glycine, sarcosine, dimethyglycine, and betaine. Apparent molal volumes and viscosity B-coefficients have been calculated from these data. The results suggest that a charged nitrogen atom bearing 3 or 2 hydrogen atoms interacts strongly with the solvent water to form a primary solvation sheath. Substitution of two of the three hydrogen atoms, as in dimethylglycine, leads to a considerable reduction in solvation, and complete substitution, as in betaine, seems to prevent it entirely.

cis-Dioxo- and trioxo-complexes

Abstract: Raman and infrared spectra have been measured of a number of transition-metal complexes of the form [MO2X4]n–(M = MoVI, WVI, or VV; X = F, Cl, or ½ Ox), and a cis configuration of the oxygen ligands has been found for these d0-species. The results are compared with those obtained for trans-dioxo-complexes and the differences explained in terms of the oxygen–metal bonding involved. The vibrational spectra of a number of trioxo-species and some polymeric oxyfluorides have also been measured.

The electronic properties and stereochemistry of the copper(II) ion. Part III. Some penta-ammine complexes

Abstract: The polarised single-crystal electronic spectra and e.s.r. spectra of six tetra-amminecopper(II) complexes of known crystal structure have been examined. In the two tetragonal octahedral complexes the order of the one-electron orbital energy levels is established as dx2–y2 > dz2 > dxy > dxz,dyz. In the strictly square coplanar complex Na4 Cu(NH3)4[Cu(S2O3)2], the order of the dxy and dxz,dyz levels may be inverted. The energy of the dz2â†�dx2–y2 transition can be used as a measure of the relative tetragonal distortion present and is correlated with the in-plane copper–nitrogen bond lengths. From the single-crystal e.s.r. spectra and the electronic energy levels the orbital reduction parameters are estimated.

The oxidation of the sulphide ion at very low concentrations in aqueous solutions

Abstract: The oxidation, by oxygen, of the sulphide ion at very low concentrations in aqueous solutions has been studied at various temperatures and hydrogen ion concentrations. Under all conditions the reaction was close to first order with respect to the sulphide ion when other variables were constant. The rate of oxidation was enhanced by an increase of pH and temperature, and by increasing the oxygen:nitrogen ratio in the gas mixture. The overall reaction is summarized as follows HS–+ O2→ SO32–+ H+, SO32–+½ O2→ SO42–, SO32–+ HS–+½ O2→ S2O32–+ OH–, S2O32–+½ O2→ SO42–+ S. The first reaction is the initial rate-determining step, followed by the rapid removal of SO32– ion from solution as SO42– and S2O32–, and finally the slow oxidation of the S2O32– ion and elementary sulphur to SO42–.

Cobalt–molybdenum–alumina hydrodesulphurisation catalysts. Part I. A spectroscopic and magnetic study of the fresh catalyst and model compounds

Abstract: The u.v., visible, and i.r. spectra of the following compounds containing cobalt, molybdenum, and aluminium in tetrahedral and octahedral co-ordination in oxide lattices, and the magnetic susceptibilities over the temperature range 80–380°K of the first four compounds are reported: hydrated cobalt molybdate, calcined cobalt molybdate (CoMoO4), cobalt(II) molybdenum(IV) oxide (Co2Mo3O8), cobalt aluminate, cobalt(II) oxide, cobalt(II,III) oxide (Co3O4), sodium molybdate, ammonium paramolybdate, molybdenum trioxide, and γ-alumina. The spectroscopic and magnetic properties of a fresh (i.e., unsulphided) cobalt–molybdenum–alumina hydrodesulphurisation catalyst are reported and compared with the properties of the above compounds in order to determine the chemical and structural environment of cobalt and molybdenum in the catalyst. Cobalt is present as cobalt(II), approximately 50% in octahedral co-ordination and 50% in tetrahedral co-ordination by oxide. There is very little magnetic interaction between the cobalt ions which are well dispersed in the catalyst. Molybdenum is present as molybdenum(VI) in tetrahedral co-ordination by oxide. There is no evidence for the presence in the catalyst of Co3O4 or any well defined compound of cobalt, molybdenum, or aluminium. The relevance of the results to the preparation of the catalyst is discussed.

Structure and stability of carboxylate complexes. Part I. The crystal and molecular structures of copper(II) glycollate, DL-lactate, 2-hydroxy-2-methylpropionate, methoxyacetate, and phenoxyacetate

Abstract: The crystal structures of bis(glycollato)copper(II), aquobis-(DL-lactato)copper(II) hemihydrate, diaquobis-(2-hydroxy-2-methylpropionato)copper(II), diaquobis(methoxyacetato)copper(II), and diaquobis(phenoxyacetato)copper(II) have been determined by three-dimensional X-ray structure analysis. All the complexes contain trans-chelate rings, which, apart from the bow-shaped lactate, are coplanar. The copper ions are in elongated tetragonally distorted octahedral environments with two exceptions: in the lactate, copper ions are in a nearly square-pyramidal five-co-ordinate environment; in the methoxyacetate, the octahedron is compressed. Details of the structures may be rationalised in terms of Jahn–Teller distortions and hydrogen-bonding.

Selective homogeneous hydrogenation of alk-1-enes using hydridocarbonyltris(triphenylphosphine)rhodium(I) as catalyst

Abstract: The complex hydridocarbonyltris(triphenylphosphine)rhodium(I), RhH(CO)(PPh3)3, has been shown to be an efficient catalyst for the homogeneous hydrogenation of unsaturated compounds of the formula RCHCH2. For hex-1-ene and dec-1-ene in benzene solution, the rate law has been found to be: Rate =k1K1c[S][A]/(1 +K1[S]) where [S] and [A] are the concentrations of alk-1-ene and catalyst respectively, c is the concentration of hydrogen in solution, K1 is the formation constant for an alkene intermediate complex, and k1 is the rate constant for the rate determining, hydrogen activation step. The high selectivity for the reduction of alk-1-ene is attributed to steric factors caused by the bulky triphenylphosphine groups.

The hydrolysis of monochlorophosphine and monochloroarsine complexes of platinum(II): bridging phosphinato- and arsinato-groups

Abstract: The hydrolysis of complexes of the type cis-[PtX2(MR2Cl)(M′R′3)](I)(X = Cl, Br, or I; M = P or As; M′= P or As; R and R′= alkyl or phenyl group) is described. The first hydrolysis products are cis-[PtX2(MR2OH)(M′R′3)](II) which exist as strongly hydrogen-bonded dimers especially when M = P. These readily lose HCl by further hydrolysis to form binuclear phosphinato- or arsinato-bridged complexes [(M′R′3)XPt(R2MO)2PtX(M′R′3)](III). The arsinato-bridged compound can be hydrolysed no further, but the phosphinato-bridged complexes hydrolyse readily to give two isomeric hydroxides α- and β-[(M′R′3)(OH)Pt(R2PO)2Pt(OH)(M′R′3)](IV). By treatment with concentrated hydrohalic acid, the phosphinato-bridged complexes revert to (II; M = P) and the arsinato-bridged compounds to (I; M = As). (III) and (IV) react with NaSEt to form thio-bridged complexes with terminal [R2MO]– groups. The structures were determined by 1H n.m.r. and infrared spectra, and the P–O stretching frequency was correlated with its position in the complex; ν(P–OH)terminalca. 880, ν(P–O)bridgeca. 1010, and ν(P–O)terminalca. 1103 cm.–1. The phosphinato-bridged platinum(II) system is stronger than the iodidobridge, but weaker than the ethylthio-bridge.It is shown that diphenylhydroxyphosphine exists in equilibrium with diphenylphosphine oxide in sufficient concentration to react in the hydroxy-form with [Pt2Cl4(PEt3)2], to form (II; M = M′= P; R = Ph, R′= Et].The Pt(R2PO)2Pt ring behaves as if both oxygen and phosphorus have an equal and high trans-influence, similar to that of the diphenylphosphido-bridge, suggesting considerable conjugation around the ring. This would be in accord with the peculiar stability of the dihydroxide (IV). The only other proven example of a hydroxyplatinum(II) complex, trans-[Pt(OH)(GePh3)(PEt3)2], also has a group of high trans-influence trans to hydroxide.

Some acetato–amine complexes of nickel(II), copper(II), and zinc(II)

Abstract: Preparations of the compounds [{Ni(1,3-pn)2}2C2O4](ClO4)2,H2O, [{Ni(dpt)H2O}2C2O4](ClO4)2, [{Cu(dien)}2C2O4](ClO4)2(and hydrate), [{Cu(dpt)}2C2O4](ClO4)2, [{Zn(en)2}2C2O4](ClO4)2, [{Zn(dpt)}2C2O4](ClO4)2, and [{Zn(trien)}2C2O4](ClO4)2, considered to have dimeric structures with bridging bichelate oxalate ions, are described. The pairs of compounds [{M(en)2}2C2O4](ClO4)2 and [{M(trien)}2C2O4](ClO4)2[M = Ni(II) or Zn(II)] are isostructural, whereas the pair [{M(dpt)}2C2O4](ClO4)2[M = Cu(II) or Zn(II)] are not isostructural. The racemic isomer of the cyclic tetramine 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane forms an analogous compound, [{Ni(tet b)}2C2O4](ClO4)2, whereas the meso-isomer forms only a simple oxalate, Ni(tet a)C2O4, and its trihydrate, considered to have polymeric structures with bridging, bi-unidentate oxalate ions. The compounds [Zn(1,3-pn)2](ClO4)2 and [Zn3(trien)4](ClO4)6 were also prepared. Infrared spectra and magnetic susceptibilities (µeff∼ 3 B.M. for the nickel compounds and ∼1·8 B.M. for the copper compounds) are reported (en = diaminoethane; 1,3-pn = 1,3-diaminopropane; dien = diethylenetriamine; dpt = dipropylenetriamine; trien = triethylenetetramine).

Chemistry of polynuclear compounds. Part XIII. The preparation and some reactions of dodecacarbonyltriosmium

Abstract: Dodecacarbonyltriosmium, Os3(CO)12, and a series of related trimeric derivatives, Os3(CO)10XY (X = H, Y = H, OH, or OMe; X = Y = OMe), have been prepared from the reaction of osmium tetroxide in methanol with carbon monoxide at moderate pressures and temperatures. Mass spectral, i.r. and n.m.r. data support a cyclic configuration for the compounds Os3(CO)10XY, possibly involving an OsOs double bond. The reactions of Os3(CO)12 with base and with halogens have been investigated and the compounds H2Os4(CO)13, H4Os4(CO)12, HOs3(CO)10(OH), and Os3(CO)12X2(X = Cl, Br, or I) isolated. The tetranuclear hydrides are similar to H2Ru4(CO)13 and β-H4Ru4(CO)12 reported previously. I.r. and mass spectral data for Os3(CO)12X2 favour a linear arrangement (X–Os–Os–Os–X) of the three metal atoms with an overall molecular symmetry D4h. Mass spectral evidence for the formation of Os2(CO)8X2 and Os2(CO)6X4 from the thermal decomposition of Os3(CO)12X2 is offered.

The crystal structure of ruthenium carbonyl, Ru3(CO)12

Abstract: An X-ray structural analysis of ruthenium carbonyl, Ru3(CO)12, has been completed using 936 independent reflexions in a least-squares refinement (R= 0·079). The molecule has essentially D3h symmetry with a mean Ru–Ru bond length of 2·848 A. The crystal structure is very similar to that of Os3(CO)12.

The preparation and magnetic properties of some Schiff base–iron(III) halide complexes

Abstract: The preparation and magnetic susceptibilities over the temperature range 80–300°K of eighteen iron(III)–Schiff base chloro- or bromo-complexes are reported. The complexes fall into two groups, uninuclear and binuclear. The magnetic data for the binuclear complexes have been interpreted by use of the dipolar coupling approach and values of the exchange integral, J, found to be in the range –6·5 to –8·0 cm.–1.

Studies on transition-metal peroxy-complexes. Part VI. Vibrational spectra and structure

Abstract: The Raman and infrared spectra have been measured of a range of transition-metal complexes involving bidentate or bridging peroxide groups, and also of those containing the hydroperoxide ligand or hydrogen peroxide of crystallisation. Assignments of fundamental modes are suggested; the results can be used to distinguish between the various types of peroxide complex.

Mössbauer effect studies on cubanite (CuFe2S3) and related iron sulphides

Abstract: The Mossbauer spectrum of the orthorhombic mineral cubanite (CuFe2S3) has been compared with those of related iron sulphides: KFeS2, CuFeS2, FeCr2S4, Feln2S4, and Cu2FeSnS4. Systematic trends of chemical isomer shift, quadrupole splitting, and hyperfine magnetic field with oxidation state and co-ordination number of the iron atoms were observed and these suggest that cubanite is Cu+Fe2+Fe3+S3 with rapid electron exchange between the ferrous and ferric ions; the hyperfine magnetic field is 332 kOe at room temperature. When cubanite is heated for two hours in vacuo at 370° a disordered cubic phase is produced which shows a broad non-magnetic Mossbauer spectrum at room temperature; this is consistent with the presence of equal numbers of non-interchanging ferrous and ferric ions in this phase.

Cobalt(II), nickel(II), and copper(II) complexes of 2-methylimidazole

Abstract: The preparation and spectral and magnetic properties are reported for complexes of cobalt(II), nickel(II), and copper(II) with 2-methylimidazole (Mlz). The complexes (Mlz)2CoX2(X = Cl, Br, or I), (Mlz)2NiX2(X = Br or I), and (Mlz)2CuX2(X = Cl or Br) have tetrahedral structures whereas (Mlz)2NiCl2 has a polymeric octahedral structure. The structures of the ‘inner’ complexes (Mlz′)2N (Mlz′= C4H5N2; N = Ni, Co, or Cu) together with that of (Mlz)4CuCl2 are described. The complexes are compared with those of 2-methylpyridine and the differences discussed in terms of steric hindrance and basicity.