Showing papers in "Journal of The Chemical Society-dalton Transactions in 1972"
TL;DR: In this article, an attempt is made to assess the value of the electronic properties of polycrystalline samples of copper(II) complexes of unknown crystal structure to predict the stereochemistry of the local copper ion environment.
Abstract: An attempt is made to assess the value of the electronic properties of polycrystalline samples of copper(II) complexes of unknown crystal structure to predict the stereochemistry of the local copper(II) ion environment. The value of obtaining complementary data, namely, magnetic moments, e.s.r., and electronic spectra, is emphasised in order to produce the most reliable prediction of stereochemistry and is applied to systems containing the CuN4–6 chromophore.
250 citations
TL;DR: In this paper, the authors used 27AI and 1H n.m.r. and showed that only the first two species exist when hydrated aluminium(III) chloride is dissolved in water whereas the highly polymeric species appear only after considerable hydrolysis has occurred at higher pH.
Abstract: The hydrolysis of aluminium salt solutions has been studied using 27AI and 1H n.m.r. and this has led to reliable values for the concentrations of the species of AI(H2O)63+, AI2(OH)2(H2O)84+, and AI13O4(OH)24(H2O)127+ at different degrees of hydrolysis. These ions do not account for all the aluminium in solution and another species, probably Al8(OH)20(H2O)x4+ is thought to be present. It is shown that previous controversy over the constitution of these solutions arose because of the different methods used for preparing the solutions: only the first two species exist when hydrated aluminium(III) chloride is dissolved in water whereas the highly polymeric species appear only after considerable hydrolysis has occurred at higher pH. The cations, particularly the dimer, may also be more hydrolysed than the above formulae indicate and this has probably confused the previous interpretation of the potentiometric results.
167 citations
TL;DR: In this article, the electronic, e.s.r., and i.r. spectra of a series of polycrystalline Cu(dien)XY,zH2O and Cu(din)βX2 type complexes are reported.
Abstract: The electronic, e.s.r., and i.r. spectra of a series of polycrystalline Cu(dien)XY,zH2O and Cu(dien)βX2 type complexes are reported, where X and Y are various anions and β= ammonia, ethylenediamine, 2,2′-bipyridyl, and diethylenetriamine. From a correlation of the three types of spectral data a tentative prediction is made of the local molecular copper(II) ion environment present in the different complexes.
106 citations
TL;DR: The crystal and molecular structure and absolute configuration of the title compound have been determined from three-dimensional X-ray data collected by counter methods, and refined by least squares to R 0·034 for 1959 independent reflections as discussed by the authors.
Abstract: The crystal and molecular structure and the absolute configuration of the title compound have been determined from three-dimensional X-ray data collected by counter methods, and refined by least squares to R 0·034 for 1959 independent reflections. The crystals are in space-group R3, with unit-cell dimensions a= 15·96(2)A, α= 108·4(1)°, and Z= 1. The molecular unit possesses C3 symmetry. The metal-atom cluster derives from a centred icosahedron, in which one triangular face has been substituted by a single gold atom. Au–Au Interactions are: mean centre-to-periphery 2·68 A, peripheral distances 2·836(4)–3·187(3)A, mean 2·98 A. There are three independent classes of Au–P bonds, in the range 2·21(1)–2·29(1)A. The Au–l distances are 2·600(5)A. The packing is discussed with reference to the disordered structure of Au11l3[P(p-ClC6H4)3]7.
90 citations
TL;DR: In this article, improved routes to the binuclear complex (π-C5H5)2TiCl]2L′2 were described, and with the ligands L2=αα′-bipyridyl, ethylenediamine, or sym-dimethylethylenedienine, they gave the complexes.
Abstract: Improved routes to the dimer [(π-C5H5)2TiCl]2 are described. With the ligands L = NH3, NH2R, py, Me2PhP, and MePh2P the dimer gives the complexes (π-C5H5)2TiClL. The ligands L2=αα′-bipyridyl, ethylenediamine, or sym-dimethylethylenediamine give the complexes [(π-C5H5)2TiL2]+A– and with L2′= Ph2P·CH2·CH2·PPh2 the binuclear complex [(π-C5H5)2TiCl]2L′2 is isolated.
81 citations
TL;DR: In this paper, a general method of characterising simple binary carbonyls produced under matrix isolation conditions, where i.r. spectroscopy is often the only means of detection, is presented.
Abstract: This paper is concerned with a general method of characterising simple binary carbonyls produced under matrix isolation conditions, where i.r. spectroscopy is often the only means of detection. I.r. band frequency and intensity patterns are calculated for a number of isotopically mixed carbonyls, and in particular, it is shown that if one were to use a mixture of C16O and C18O in the metal-atom synthesis of these compounds, then the species MCO, M(CO)2, M(CO)3(D3h), M(CO)4(D4h or Td), and M(CO)6(Oh) would each give rise to a characteristic frequency and intensity pattern. These patterns not only reveal the stoicheiometry and symmetry of the species, but also yield the appropriate Cotton–Kraihanzel force constants. The calculations are displayed as line spectra and cover a wide range of force constants.
80 citations
TL;DR: In this article, the interaction of chlorides of V, Cr, Mo, and W with the lithium or Grignard reagents derived from chloromethyltrimethylsilane produces thermally stable alkyls of formula V(CH2SiMe3)4, VO(CH 2SiMe 3)3, Cr(Ch2SiMo3) 4, and M2(M = Mo or W).
Abstract: The interaction of chlorides of V, Cr, Mo, and W with the lithium or Grignard reagents derived from chloromethyltrimethylsilane produces thermally stable alkyls of formula V(CH2SiMe3)4, VO(CH2SiMe3)3, Cr(CH2SiMe3)4, and M2(CH2SiMe3)6(M = Mo or W). The compounds have been investigated, where feasible, by i.r., Raman, electronic, e.s.r., and n.m.r. spectroscopy and the various spectral assignments are discussed in terms of proposed structures for the compounds.
78 citations
TL;DR: In this paper, a trigonally co-ordinated transition metal series has been characterized by analysis, molecular weight determination, and mass spectra, and the compounds M[N(SiMe3)2]3, where M = Sc, Ti, V, Cr, and Fe, have been prepared by reactions involving metal chloride complexes and the lithium derivative of hexamethyldisilazane.
Abstract: The compounds M[N(SiMe3)2]3, where M = Sc, Ti, V, Cr, and Fe, have been prepared by reactions involving metal chloride complexes and the lithium derivative of hexamethyldisilazane. The compounds have been characterized by analysis, molecular weight determination, i.r., and mass spectra. They are members of a trigonally co-ordinated transition metal series.
71 citations
TL;DR: The semi-empirical, SCF-MO theory using the approximation of CNDO is parameterized for the prediction of potential surfaces for both open and closed shell molecules and ions as mentioned in this paper.
Abstract: The semiempirical, SCF–MO theory, using the approximation of CNDO is parameterized for the prediction of potential surfaces for both open and closed shell molecules and ions. It is designated CNDO/BW. Empirical examination of the importance of core repulsion leads to the introduction of an expression for the core repulsion energy which results in the simultaneous prediction of relatively good equilibrium geometries and bonding energies for a variety of molecules. The importance of several of the CNDO parameters is examined in this context.
71 citations
TL;DR: The vibrational spectra of a number of transition metal tetra-oxo-complexes are reported for the first time, including those of salts containing the anions [RuO4] and [MO4]2] as mentioned in this paper.
Abstract: The vibrational spectra of a number of transition metal tetra-oxo-complexes are reported for the first time, including those of salts containing the anions [RuO4]–; [MO4]2–(M = Mn, Fe, or Ru); [MO4]3–(M = Cr, Mn, Re, or Fe); and [MO4]4–(M = Ti, V, Cr, Mo, W, Fe, or Co). From these measurements and published data on the fundamental frequencies of other such ions we calculate force constants for most of the known transition-metal tetra-oxoanions. Raman data on [Cr18O4]2– and [W18O4]2– are also presented
70 citations
TL;DR: In this article, a single-stage synthesisation method for important hydride, carbonyl, and nitrosyl containing triphenylphosphine complexes of the platinum group metals has been described.
Abstract: Previously reported, convenient, single-stage syntheses for important hydride, carbonyl, and nitrosyl containing triphenylphosphine complexes of the platinum group metals have been further improved by use of ethanolic potassium hydroxide or triethylamine in place of sodium borohydride as basic reducing agent. The technique has also been extended to include convenient new syntheses for the ruthenium and osmium triphenylphosphine derivatives. cis-RuCl2(CO)2(PPh3)2, OsHCl(CO)(PPh3)3, OsH2(CO)(PPh3)3, and OsH2(CO)2(PPh3)2. The stereochemistry of these last-named complexes is discussed. Attempts to extend this mode of synthesis to include derivatives of other triarylphosphines are described. New complexes synthesised include Rh(NO)L3[L = P(p-C6H4Cl)3 and P(p-C6H4Me)3] and Ru(CO)3L2[L = P(p-C6H4Me)3 and P(p-C6H4OMe)3].
TL;DR: In this paper, the Bleaney-Bowers model was applied to the available experimental data on some 140 binuclear copper(II) carboxylates and the results indicated that the trends in the σ- and δ-exchange integrals are of the opposite sense.
Abstract: The singlet–triplet–singlet model describing the anomalous magnetic properties of binuclear copper(II) carboxylates is applied to the available experimental data on some 140 compounds. About one-sixth of the data was eventually rejected because of the poor fit with both this and the Bleaney–Bowers model. The trend in |J|, the singlet–triplet separation, parallels the trend in Δ, the singlet–singlet separation, when the terminal ligand is varied. This indicates that the trends in the σ- and δ-exchange integrals are of the opposite sense. All the exchange integrals are increased nephelauxetically by better bonding of terminal or bridging groups, but, because of the unique geometry of the system, the small component of σ-bonding is decreased overall by radial dispersal of dz2‘holes’ onto the terminal ligands. This component of σ-bonding is of a direct nature, but no firm conclusions as to the nature of the δ-interaction may be drawn.
TL;DR: The green complex formed on treating commercial ruthenium trichloride hydrate with acetic acid and sodium acetate in ethanol is shown to be of the basic acetate oxo-centred triangular type with the formula [Ru3O(CO2Me)6-(H2O)3] as mentioned in this paper.
Abstract: The green complex formed on treating commercial ruthenium trichloride hydrate with acetic acid and sodium acetate in ethanol is shown to be of the basic acetate oxo-centred triangular type with the formula [Ru3O(CO2Me)6-(H2O)3](CO2Me). The complex may be cationic, neutral, or anionic depending on the pH of the solution, owing to ionisation of co-ordinated water. The water molecules may be replaced by pyridine to give [Ru3O(CO2Me)6py3]+. Both the aquo and pyridine complexes undergo successive one and two electron reductions to give complexes in which the metal atoms are in formal oxidation states + 2 ⅔ or (III, III, II) and +2 or (II, II, II) respectively. The reduction to the latter state involves loss of the central oxygen atom from the triangle of metal atoms; this atom may be reinserted using molecular oxygen, or more specifically by use of a reagent such as pyridine-N-oxide. In the presence of triphenylphosphine, [Ru3O(CO2Me)(H2O)3]+ gives the reduced species Ru3O(CO2Me)6(PPh3)3. The potentials and reversibility of the redox reactions have been studied electrochemically. Analogous complexes of other carboxylic acids are described. N.m.r., i.r., and electronic absorption spectra of the species are reported.
TL;DR: In this paper, double-resonance experiments have been used to determine selenium chemical shifts in 80 organoselenium compounds containing 77Se in natural abundance, and the shifts cover a range of over 1500 p.p.m.
Abstract: 1 H–{77Se} Double-resonance experiments have been used to determine selenium chemical shifts in 80 organoselenium compounds containing 77Se in natural abundance. The shifts cover a range of over 1500 p.p.m. and are relatively insensitive to solvent effects. Electronegative substituents give shifts to low field, and in general the shifts parallel those found in similar phosphorus compounds, but are several times larger for a given electronic change. Correlations are found with the extent of α-chain branching in alkyl derivatives, and with Hammett σ-constants in substituted aryl derivatives. The chemical shifts show greater promise as diagnostic tools than do coupling constants involving selenium.
TL;DR: In this article, the crystal and molecular structure of the title complex was determined by X-ray photographic methods and the structure was solved by conventional Patterson and Fourier methods, and was refined by least-squares to R 0·15 for 2043 unique reflections.
Abstract: The crystal and molecular structure of the title complex has been determined by X-ray photographic methods. The unit cell is trigonal, with a=b= 18·05(1), c= 7·25(1)A, space-group P, and Z= 2. The structure was solved by conventional Patterson and Fourier methods, and was refined by least-squares to R 0·15 for 2043 unique reflections. Only a few of the water molecules of crystallization could be located. The crystal is composed of trinuclear units of copper atoms each centred about a three-fold crystallographic axis so that the three copper atoms fall at the corners of an exact equilateral triangle of side 3·22 A. The copper atoms are held together by three distinct bridging systems: (i) the oxygen atom of the hydroxy-group, situated on the three-fold axis, is bonded to all three copper atoms with Cu–O 1·98 A, (ii) a sulphato-group, also on the three-fold axis, acts as a tripod bridge, bonding to all three copper atoms through three of its oxygen atoms, and (iii) three symmetry-related pyridine-2-carbaldehyde oximato-groups each functioning both as a bidentate chelate to one of the copper atoms (via both N atoms) and as a Cu–Cu bridging group (via oxime N and O). The trimer units are stacked in continuous columns parallel to the c axis and adjacent units are held together by hydrogen bonding. These columns are arranged such that a large almost cylindrically shaped hole (diameter ca. 10 A) is formed, running along the length of the c axis, and containing the molecules of water of crystallization; these are not held in fixed positions but appear to be somewhat mobile. The structure of the complex confirms a prediction made on the basis of the observed temperature-independent magnetic moment of 1·0 B.M. per copper atom.
TL;DR: In this article, it is shown that the partial field gradient associated with a given ligand is different for tetrahedral, trigonal-bipyramidal-apical, triconnective-equatorial, and octahedral co-ordination positions.
Abstract: Mossbauer quadrupole splitting in organotin(IV) compounds is interpreted in terms of the additive approximation, in which the total electric field gradient at the 119Sn nucleus is written as a sum of partial field gradient tensors. Localized orbitals are shown to provide the natural framework for discussion of additive electric field gradients, and it is conjectured that the existence of a suitable localization transformation is a necessary condition for additivity. It is shown that the partial field gradient associated with a given ligand is different for tetrahedral, trigonal-bipyramidal-apical, trigonal-bipyramidal-equatorial, and octahedral co-ordination positions. In particular, the partial field gradient for octahedral co-ordination is about 70%(experiment indicates 75%) of that for tetrahedral. Absolute numerical values for partial field gradient parameters cannot be obtained from experiment for any of the above co-ordination positions, but the evaluation of relative parameters is discussed, and working values are given for a variety of ligands in tetrahedral or octahedral structures. Quadrupole splittings calculated by use of these values agree with observed splittings to within 0·4 mm s–1 or better. Alternatively, disagreement may be used as evidence of large distortions or incorrect assignment of structure. It is shown that a literal'point-charge' treatment of the effect of distortions from idealized geometry cannot be justified in molecular-orbital terms. Illustrative calculations are performed for tetrahedral systems, but experimental data indicates that it is better to ignore small distortions in quantitative discussion of the magnitude of quadrupole splitting. Extension of the model to octahedral complexes of low-spin Fe(II) is briefly discussed.
TL;DR: The structure of the title compound has been determined as mentioned in this paper, which is monoclinic with a= 15·362, b= 9·483, c= 20·054 A, β= 95° 6′, Z= 4, space group C2.
Abstract: The structure of the title compound has been determined. The crystals are monoclinic with a= 15·362, b= 9·483, c= 20·054 A, β= 95° 6′, Z= 4, space group C2. 3292 Visually estimated X-ray reflections were refined to R 8·88%. There are two crystallographically independent molecules, each possessing a two-fold axis. The PCP angle is 143·8° in one of these molecules and 130·1° in the other. The results are compared with those obtained for related species, including the isoelectronic cation Ph3PNPPh3 and the cumulene ylides.
TL;DR: The crystal structure of the title compound was determined from photographic data and solved by direct methods as discussed by the authors, and unique reflections were refined by least-squares methods to R 0·104.
Abstract: The crystal structure of the title compound was determined from photographic data and solved by direct methods. 598 Unique reflections were refined by least-squares methods to R 0·104. Crystals are monoclinic, space-group C2/c, with a= 9·957, b= 9·335, c= 8·889 A, β= 102·48°, Z= 4. The molecules possess D2d(2m) symmetry within experimental error. Mean bond lengths and angles are: As–As 2·593, As–S 2·243 A S–As–As 99·1, S–As–S 94·4, and As–S–As 101·2°. The Raman spectra of α- and β-As4S4 are presented; the molecules may polymerise on prolonged laser irradiation.
TL;DR: In this article, the structure of the title compound was determined from diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0·028 for 1292 observed reflexions.
Abstract: Crystals of the title compound are orthorhombic, a= 8·690(2), b= 11·920(2), c= 8·100(2)A, Z= 4, space-group P212121. The structure was determined from diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0·028 for 1292 observed reflexions. The cadmium is co-ordinated to seven oxygen atoms; the co-ordination is best described by a distorted square base-trigonal cap geometry. Both acetate groups are bidentate, although the oxygen atom, O(1), of one of them, is also in a bridging position forming a continuous cadmium–oxygen spiral around the two-fold screw axis parallel to c. There are two distinct Cd–O distances, involving both acetate groups : Cd–O(2) 2·294(4), Cd–O(1) 2·597(4), Cd–O(3) 2·304(4), and Cd–O(4) 2·546(4)A. This may be expected for the acetate group containing the bridging oxygen, O(1), but it is somewhat surprising to find long and short Cd–O bonds in the acetate not having a bridging oxygen. There is an extensive hydrogen-bonding network which reinforces the Cd–O spiral and also links spirals.
TL;DR: A series of four and five-coordinate iridium(I) salts have been prepared from the reactions of [C8H12lrCl]2 with L. The 1H n.m. spectra of these salts are discussed in this article.
Abstract: A series of four- and five-co-ordinate iridium(I) salts of the type [C8H12lrL2]X, [C8H12lrL3]X, [lrL4]X, and [lrL5]X, (L = tertiary phosphite, phosphine, or arsine; X = BPh4, PF6, or ClO4) have been prepared from the reactions of [C8H12lrCl]2 with L. For L = PMe2Ph the dioxygen adduct [lr(O2)L4]BPh4 has been characterised. The corresponding dioxygen adduct [Ir(O2)(AsMe2Ph)4]BPh4 has also been prepared. The reactions of [C8H12IrCl]2 with L (L = PEt2Ph and PBun3) have given the cis-dihydride, cis-[IrH2L4]BPh4. A new olefin hydride of iridium(III), namely [(C8H14)2IrHCl2]2, has been isolated. The reaction of this hydride with AsMe2Ph gave trans-[IrHCl(AsMe2Ph)4]PF6. The 1H n.m.r. spectra of these salts are discussed.
TL;DR: In this article, the Mossbauer spectra of rapidly quenched samples of nonstoicheiometric Fe1-xO (0·053 < x < 0·109) show an envelope of overlapping resonances which, for small values of x, can be resolved into five broad Lorentzian peaks assignable to a series of Fe2+ quadrupole doublets and an Fe3+ doublet at a lower velocity.
Abstract: Room-temperature Mossbauer spectra of rapidly quenched samples of nonstoicheiometric Fe1–xO (0·053 < x < 0·109) show an envelope of overlapping resonances which, for small values of x, can be resolved into five broad Lorentzian peaks assignable to a series of Fe2+ quadrupole doublets and an Fe3+ doublet at a lower velocity. As the phase deviates further from stoicheiometry the range of site symmetries produces a more complicated envelope which cannot be resolved into the sum of a small number of Lorentzian peaks. The influence of initial temperature and of quench rate have also been studied over the full range of composition and variations correlated with the known phase diagram for the system. Samples of Fe0·947O which had been most rapidly quenched from 1520 K into water showed negligible disproportionation during quenching. Their spectra, when compared with those predicted for various possible defect structures, suggested the presence of clusters of four vacant cation sites around a tetrahedral Fe3+. Changes in the spectra as the Fe3+ content was increased reflected the increase in the defect cluster size towards that previously proposed for Fe0·90O (13 vacant cation sites with 4 tetrahedral Fe3+). Fe3+ was present as a quadrupole doublet and no evidence was found for electron hopping between Fe2+ and Fe3+. Spectra of the magnetically ordered oxide phases at 77 K were consistent with this interpretation.
TL;DR: In this article, the structure of the title compound was solved by Patterson and electronic-density syntheses by use of three-dimensional counter data, and refined by least-squares to R 0·076 for 1833 reflections.
Abstract: Crystals of the title compound are monoclinic, a= 10·68, b= 9·38, c= 12·85, β= 96° 27′, Z= 4, space group C2/c. The structure was solved by Patterson and electronic-density syntheses by use of three-dimensional counter data, and refined by least-squares to R 0·076 for 1833 reflections. The uranium(VI) atom is in an eight-coordinate distorted hexagonal environment. The linear uranyl group is perpendicular to the equatorial plane in which three carbonate groups are chelated. The NH4+ groups which fill holes in the structure link the anions through hydrogen bonding.
TL;DR: In this article, low-temperature hydrothermal reactions of metakaolinite have been investigated, with and without additions of silica, by use of the bases LiOH, NaOH, RbOH, and CsOH and also the mixtures NaOH + LiHO, NaHO + KHO, KOH+LiHO, and NaOH+Me4NOH.
Abstract: Low-temperature hydrothermal reactions of metakaolinite have been investigated, with and without additions of silica, by use of the bases LiOH, NaOH, RbOH, and CsOH and also the mixtures NaOH + LiOH, NaOH + KOH, KOH + LiOH, and NaOH + Me4NOH. Over certain temperature and composition ranges reproducible crystallisation fields have been obtained for all the above bases and pairs of bases. Two hydrated non-zeolites were formed (nepheline hydrate I and a near-hectorite), and also a group of anhydrous phases. However under the conditions employed zeolitisation reactions were dominant, which are largely but not fully paralleled by similar reactions with aqueous alkaline aluminosilicate gels. A number of the products have been characterised by X-ray, d.t.a., t.g.a., and sorption studies, and in other ways. The most frequently occurring zeolite phases were those related to phillipsite, gismondite, gmelinite, chabazite, faujasite, Linde A type, sodalite and cancrinite hydrates, and two lithium zeolites and a sodium tetramethylammonium zeolite without natural counterparts.
TL;DR: In this article, the preparation of trinuclear ruthenium complexes of the type Ru3(CO)12 −nLn(L = tertiary phosphine or arsine; n= 1-4) is described.
Abstract: The preparation of trinuclear ruthenium complexes of the type Ru3(CO)12 –nLn(L = tertiary phosphine or arsine; n= 1–4) is described. Their i.r. and 1H n.m.r. spectra are discussed and possible structures suggested.The complexes Ru3(CO)9L3[L = PPh3, P(m-C6H4Me)3, P(p-C6H4Me)3 or PMePh2] undergo controlled pyrolytic reactions in boiling decalin, affording complexes of the type Ru2(CO)6(PAr2)2(Ar = Ph or m-MeC6H4),Ru2(CO)6[PPhR(C6H4)](PPhR)(R = Ph or Me), Ru2(CO)6[PPh2(C6H4)]2, and Ru3(CO)7(PAr3)(PAr2)(Ar = Ph, m-MeC6H4, or p-MeC6H4). Spectroscopic data suggest structures containing bridging phosphido-ligands, and ortho-metallated phenyl rings.
TL;DR: The interaction of a variety of chloro-complexes of rhenium with dithiocarbamates leads to the compounds [Re(NPh)(S2CNEt2)2]2] 2O, Re(N Ph(S 2 CNEt 2 )2], ReN(S2 CNE t2 )3, and ReCl2(SNEt t2)(PPh3)2 ].
Abstract: Dithiocarbamate complexes of oxorhenium(V) such as ReOCl2(S2CNEt2)(PPh3), ReOCl(S2CNR2)2, and Re2O3-(S2CNR2)4 have been prepared from ReOCl3(PPh3)2.The interaction of a variety of chloro-complexes of rhenium with dithiocarbamates leads to the compounds [Re(NPh)(S2CNEt2)2]2O, Re(NPh) Cl(S2CNEt2)2, ReN(S2CNEt2)3, and ReCl2(S2CNEt2)(PPh3)2. The properties and infrared spectra are reported.
TL;DR: In this paper, a theoretical investigation of the Cossee mechanism for Ziegler-type catalysis has been made by use of the all valence electron self-consistent field method.
Abstract: A theoretical investigation of the Cossee mechanism for Ziegler-type catalysis has been made by use of the all valence electron self-consistent field method. The electronic structure of a titanium–aluminium–ethylene complex was studied, as well as the sequence of steps in which ethylene inserts into a titanium–methyl bond. The study of the olefin complex reveals that (a) the titanium–olefin bond has no retrodative character and the antibonding π* orbital of ethylene acquires little stability as a result of interaction with the titanium d orbitals; (b) the titanium–methyl σ-bond is localised almost completely in the highest bonding level of the olefin complex and the contribution to it from the metal atom is almost pure d in character; (c) the > AIR2 group in a molecular catalyst seems merely to function as a substrate which maintains a high co-ordination number at the titanium site. Calculations on the reaction co-ordinate show that the methyl group can migrate from its site to join the ethylene molecule without becoming detached from the titanium atom and that the dyz orbital functions as a ‘transfer agent’. This, and a study of the total energy changes over the co-ordinate, lead to a new rationale of the mechanism of catalysis and the existence of vacant sites.
TL;DR: The crystal structure of the title compound has been determined by single-crystal X-ray diffraction methods from diffractometer data by Patterson and Fourier methods and refined by least squares to R 0·094 for 1051 independent observed intensities.
Abstract: The crystal structure of the title compound has been determined by single-crystal X-ray diffraction methods from diffractometer data by Patterson and Fourier methods and refined by least squares to R 0·094 for 1051 independent observed intensities. The crystals are trigonal, space group P1c with a= 16·112 and c= 8·556 A, Z= 2. The molecule has D3 symmetry, with an angle of 49·2° between the FeN3and NSi2 planes. The Fe–N bond, at 1·917(4)A is somewhat shorter than values found in other compounds. Bond lengths and angles involving the other atoms are normal.
TL;DR: In this paper, a rigorous method for fitting a straight line to a set of independent points subject to correlated errors is described, and expressions for the estimated standard deviations of the resultant parameters are given.
Abstract: A rigorous method is described for fitting a straight line to a set of independent points subject to correlated errors. The algoritham is briefly stated, and includes expressions for the estimated standard deviations of the resultant parameters. One application of this general method is detailed: the computation of stability constants from precise potentiometric data for systems of dibasic acids HA, H2A, and mononuclear metal-ion complexes BA, BA2. Some other applications are indicated.
TL;DR: In this paper, a series of isonitrile complexes, [(CO)6 −xM(CNR)x](x= 1-3; M = Cr, Mo; R = Me, Et, Pri, C6H11, But, p-tolyl, Ph, pClC6H4) is reported.
Abstract: The preparation of a series of isonitrile complexes, [(CO)6 –xM(CNR)x](x= 1–3; M = Cr, Mo; R = Me, Et, Pri, C6H11, But, p-tolyl, Ph, p-ClC6H4) is reported. The results of spectroscopic (i.r., u.v., mass, and n.m.r.— particularly aromatic solvent induced shifts) and electrochemical measurements are employed to assess the nature of the bonding in these systems. It is shown that the contribution of (d→π*)π-bonding is negligible and that variations in the donor strength of the isonitrile ligand are principally responsible for the changes observed. The compounds (RNC)Cr(CO)5 do not react with weak nucleophiles (amines, alcohols). Ketimine formation does not result from the reaction between (RNC)Cr(CO)5 and a silane in the presence of pyridine. The reaction between (RNC)2Cr(CO)4 and (Me2PCH2)2(dmpe) affords cis-(RNC)2(dmpe)Cr(CO)2 as the principal product, together with (dmpe)2Cr(CO)3.
TL;DR: In this article, the 8-peri-position of iridium trichloride with L in 2-methoxyethanol gives [IrCl2(P-C)L2], which with chlorine gives mer-[IrCl3L3] very rapidly.
Abstract: Dimethyl(1-naphthyl)phosphine (L) is readily metallated in the 8-(peri-)position by iridium (III), (C10H6PMe2 P–C). Thus iridium trichloride with L in 2-methoxyethanol gives [IrCl2(P–C)L2]. In the presence of a base and alcohol further metallation occurs to give [IrCl(P–C)2L] and then [IrH(P–C)2L], which on pyrolysis gives the trimetallated complex fac-[Ir(P–C)3]. [IrHCl2(cyclo-octa-1,5-diene)]2 reacts with L to give [IrHCl2L3], which with chlorine gives mer-[IrCl3L3]. mer-[IrCl3L3] is converted by boiling 2-methoxyethanol into [IrCl2(P–C)L2] very rapidly. [IrCl(cyclo-octa-1,5-diene)]2 reacts with L to give [IrHCl(P–C)L2], which, in boiling 2-methoxyethanol, is converted to [IrCl(P-C)2L]. The base-promoted metallations are readily reversed by HCl, e.g. [IrCl(P–C)2L] gives [IrCl2(P–C)L2] and [IrHCl(P–C)L2] gives [IrHCl2L3], etc. A few rhodium complexes were also prepared such as [RhCl2(P–C)L2] and [RhClL3]. The configurations of these complexes were determined by 1H and /or 31P n.m.r. spectroscopy. I.r. data are also recorded.