Inorganic Chemistry of the Transition Elements Volume 6

A Review of the Literature Published Between October 1975 and September 1976

By B. F. G. Johnson

The Royal Society of Chemistry

Copyright © 1978 The Chemical Society
All rights reserved.
ISBN: 978-0-85186-550-8

Contents

Chapter 1 The Early Transition Metals, 1,
Chapter 2 Elements of the First Transitional Period, 166,
Chapter 3 The Noble Metals, 304,
Chapter 4 Zinc, Cadmium, and Mercury By J. A. S. Howell and P. Wyeth, 395,
Chapter 5 Scandium, Yttrium, the Lanthanides, and the Actinides By F. J. Berry, 433,
Author Index, 460,

CHAPTER 1

The Early Transition Metals

BY F. L. BOWDEN, P. F. HEVELDT, AND D. J. WATSON

PART I: Titanium, Zirconium, Hafnium, Vanadium, Niobium, and Tantalum

by F. L. Bowden

1 Titanium

Introduction. — Reviews have appeared on the structural, organometallic, and general chemistry of titanium. The organometallic chemistry of titanium is included in a text published this year." A new measurement of the natural abundances of the titanium isotopes gives 47.875285 as the atomic weight of titanium (C = 12).

Titanium compounds containing sulphide and amino-groups have been extracted from plant cells by acetone extraction. The reducing activity of the titanium compounds isolated from cells kept in the dark is higher than that after photosynthesis.

Vapour deposition experiments on titanium have shown that on increasing the rate of titanium deposition at constant argon deposition rate, three new absorptions were observed in the spectrum of the matrix in addition to those due to matrix-isolated atoms. These absorptions have been attributed to the dititanium species for which MO calculations indicate a strong 4s–4s σ-interaction.

Reduction of Cp2TiCl2 with A1 in THF under 1 atm CO is the most efficient, giving the red crystalline Cp2Ti(CO)2 in quantitative yields (cf. 80 % with Na-Hg as reducing agent). The carbonyl can also be obtained from Cp2TiBH4 and CO in the presence of Et3N. Reduction of CpTiCl3 with Mg in the presence of C7H7 gives CpTiC7H7. Derivatives of this compound, ([FORMULA NOT REPRODUCIBLE IN ASCII], or indenyl) and (η7-C7H6C6H5)(η5- C5H5)Ti, have been prepared. Their mass spectra indicate the occurrence of CH or CR migrations affording π-C6H6Ti species. Similar fragmentation patterns in the mass spectrum of the green product from CpTiCl3 or CoTiCl2 and C9H9Li are cited in support of a [FORMULA NOT REPRODUCIBLE IN ASCII] structure.

Hydrolysis of titanocene produces the complex [Cp(C5H4)TiOH]2; X-ray crystallography has established that this has the fulvalene structure (1) characteristic of the titanocene molecule (Vol. 4, FORMULA p. 2) and that the titanium atoms are bridged by the two hydroxy-groups.

Oxidative coupling of the PhC [equivalent to] C fragment occurs in the reaction between PhC [equivalent to] CNa and [FORMULA NOT REPRODUCIBLE IN ASCII] to afford [FORMULA NOT REPRODUCIBLE IN ASCII] (2). The η5-C5H5 analogue of (2) has been obtained directly from (η5-C5H5)2Ti and 1,4-diphenylbuta-1,3-diyne. A purple intermediate found in the oxidative coupling reaction has v(C [equivalent to] C) at ca. 2045 cm-1 and was assigned the σ, π-bridged structure (3).

The electronic configuration of dicyclo-octatetranyltitanium has been derived on the basis of C8v local symmetry for the metal. The overall molecular symmetry is much lower than this with one C8H8 ring symmetrically bound (C8v) and the other one unsymmetrically bound (Cs). Vibrational spectroscopic data indicated the former to be the most firmly bound.

Binary Compounds and Related Systems —Halides and Oxyhalides. The heat capacity of TiF4 has been determined. The peculiar temperature dependence of the magnetic susceptibility of β-TiCl3 is attributed to the presence of two kinds of chain-end site. The kinetics of disproportionation of TiCl3 have been measured over the temperature range 873 — 1373 K.

Molecular force constants for TiCl4 have been calculated from i.r. data on the isotopic species 48TiCl4 and Ti35Cl4 in argon matrices, and 48Ti35Cl4 in the gas phase. MO calculations of the ground state of TiCl4 show that as expected, the higher filled MOs are mainly chlorine 3p in character. A formal metal charge of only 1.0 + indicates a considerable deviation from the simple d° description of the molecule. The energy levels of TiCl4 have been calculated by the CNDO method. The existence of long-lived negatively charged molecular ions in the mass spectra of several titanium compounds including TiCl4, is an indication that these compounds have positive electron affinities.

Oxides. Ti2O3 has been investigated by X-ray spectroscopy and by e.p.r. spectroscopy and magnetic susceptibility measurements; there has been an improved MO calculation of its band structure. A band model has been proposed to account for the origin of the magnetic moment and metallic transition of vanadium-doped Ti2O3. According to e.p.r. measurements the Ti3+ ions in mixed valence phases of the system TinO2n-1 have D2h symmetry; the rhombic field splitting parameters were determined.

Chalcogenides. Vapour pressure measurements on sulphur in equilibrium with TixS2 (1.11 >x > 1.00) at 773 — 973 K have provided thermodynamic data on which to base a preparation of TixS2 crystals with well-defined Ti: S ratios, and in addition have confirmed the existence of stoicheiometric TiS2. This has been confirmed independently by intercalation ratios, electron microscopy, and by measurements of electron transport and magnetic susceptibilities. TiS2 has nearly ideal octahedral co-ordination of the metal in a hexagonal laminar structure with an interlayer S — S distance of 3.462(5) Å. Titanium oxides and oxide-carbon mixtures undergo a two-stage sulphidization with H2S at 773 — 1773 K, affording non-stoicheiometric Ti1.25S2.

The structure of 12R-Ti8S1 2 has been refined to an R index of 2.8%, and the structures of a new poly-type 24R of TiS1.80±0.02 and TiS3 have been determined. n-Butyl-lithium in hexane has been found to be a mild but highly efficient reagent for the intercalation of lithium into layered chalcogenides; reaction with chalco-genides of Group IVB is sufficiently exothermic to cause the hexane to boil. This method avoids the problems of decomposition and partial intercalation experienced with high-temperature methods and also avoids the intercalation of ammonia when solutions of lithium in liquid ammonia are used. Moreover, the limiting stoicheiometry LiMX2 (M = Ti or Zr) can be achieved which represents more lithium than can be intercalated by either of the other methods. The view that intercalation involves electron transfer from the (Bun)- anion and intercalation of the Li+ cation to balance the charge is in keeping with the results of an n.m.r. study of LixTiS2 which indicate the donation of an appreciable fraction of the Li 2s electron to the TiS2 layers, the fraction decreasing as x increases. The reaction between TiS2 an alkali-metal halide and H2S at 1073 — 1273 K affords A0.5TiS2 (A = Li, Na, K, Rb, or Cs), whereas TiS2 and sodium naphthalenide afford a product Na0.8TiS2, with a higher alkali-metal concentration.

Two families of copper titanium sulphides have been prepared; they are: [FORMULA...

Inorganic Chemistry of the Transition Elements Volume 5

A Review of the Literature Published Between October 1974 and September 1975

By B. F. G. Johnson

The Royal Society of Chemistry

Copyright © 1977 The Chemical Society
All rights reserved.
ISBN: 978-0-85186-540-9

Contents

Chapter 1 The Early Transition Metals, 1,
Chapter 2 Elements of the First Transitional Period, 149,
Chapter 3 The Noble Metals, 302,
Chapter 4 Zinc, Cadmium, and Mercury By J. A. S. Howell and P. Wyeth, 402,
Chapter 5 Scandium, Yttrium, the Lanthanides, and the Actinides By J. A. McCleverty, 448,
Author Index, 483,

CHAPTER 1

The Early Transition Metals

BY F. L. BOWDEN, K. GRUNDY, AND B. E. REICHERT

PART I: Titanium, Zirconium, Hafnium, Vanadium, Niobium and Tantalum

by F. L. Bowden

1 Titanium

Introduction. — Various aspects of titanium chemistry are described in books published this year. Reviews have dealt with sandwich compounds of titanium and with its general, industrial, geological, and structural chemistry. The annual survey for 1972 of the organometallic compounds of titanium has appeared. Further interest in a possible biological role for titanium has been generated by the detection of up to 2 percent of the element in the red (Ahnfeltia plicata), brown (Laminaria japonica), and green (Ulva tenestrata) seaweeds. The titanium is thought to be present in combination with substances similar to 4'-phosphopantetheine or its derivatives.

Titanium atoms formed by evaporation from the metal using an electron beam technique have been co-condensed with benzene, toluene, and mesitylene to give the red di-η-arene-titanium compounds Ar2Ti, (Ar = C6H6, MeC6H5, and Me3C6H3). These compounds decompose into their constituents on heating. The titanium atoms produced in this way showed no catalytic activity in the oligomerization of butadiene, but catalytically active species resulted from the treatment of the di-η-arene compounds with organochloroaluminium reagents, or from condensates of titanium, aluminium, and organic halide vapours.

Continuing studies of charge distribution in sandwich compounds of low-valent titanium have revealed that CpTiC8H8 is more difficult to metallate than CpTiC7H7, and that methyl substitution of the metallated product occurs predominantly in the Cp ring. These chemical indications of decreased negative charge in the C8H8 ligand are substantiated by photoelectron spectroscopy, which shows the +0.4e charge on the titanium in CpTiC8H8 to be almost equal to that on the Cp ring, –0.3 to –0.4e, thus leaving the C8H8 ring almost neutral; this contrasts with charge of –0.7 to –0.8e for the C7H7 ring in C7H7TiCp.

Binary Compounds and Related Systems. — Halides and Oxyhalides. MO calculations on the TiF molecule have been performed. The equilibrium:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

is characterized by ΔH°(298 K) = –40.6 kcal mol-1, ΔS°(298 K) = 36.4 e.u., and ΔCp = 4 cal deg-1 mol-1. Negative ion electron impact studies of TiX4 (X = Cl, Br, or I) have allowed the electron affinities of TiX3 to be estimated as: 0.6 ± 0.2 (Cl), 0.8 ± 0.3 (Br), and >0.9 (I) eV. A distortion in layer-structured TiCl3 below 217 K has been revealed by far-i.r. spectroscopy; it is thought to arise from the formation of pairs of covalently bonded Ti3+ ions.

Methods for the production and purification of TiCl4 have been reviewed, and one method has been patented.

The energies of the higher filled molecular orbitals and lower excited states of TiCl4 calculated by the all-valence electron self-consistent MO method, are in good agreement with values obtained from photoelectron spectroscopy. Other spectroscopic studies include the detection by mass spectrometry of dimers in TiCl4 vapour; the assignment of i.r. absorption bands at 135, 83, and 64 cm-1, to the v modes of TiX4-(X = Cl, Br, or I); and the examination of the effects of organic solvents on the resonance Raman spectrum of TiI4. Vapour pressure measurements on TiI4 yield enthalpy values for sublimation, evaporation, and formation, of: 18.00 ± 0.05, 15.12 ± 0.01, and 2.88 ± 0.55 kcal mol-1, respectively.

An attempt to prepare TiOF2 from 40% aqueous HF and TiO2 gave material whose i.r. spectrum indicated the presence of hydroxy-groups.

Chalcogenides. Ternary phases [FORMULA NOT REPRODUCIBLE IN ASCII], having exchangeable cations, can be obtained by the electrochemical reduction of the binary M2X2 compounds or by chemical reduction with powerful reducing agents. Oxidation of the ternary phases yields the binary chalcogenides. Cation exchangeability and the degree of solvation are directly and mostly reversibly coupled with the redox state of the solid phases. The reaction between Cu2S, Ti2S3 or TiSx, and an excess of sulphur at 973 K, affords the spinels [FORMULA NOT REPRODUCIBLE IN ASCII]. Single crystals were obtained using I2 as transport agent. The temperature dependence of the magnetic susceptibility of these spinels indicated the existence of solid solutions deficient in copper. Optical, electrical, and heat-capacity studies have been carried out on the solid solutions TixTa1-xS2, and TixNb1- xSe2. An atomic absorption method has been developed for the determination of titanium in ternary sulphides of the type Fe1- xTixS(x ≤ 0.3). Intercalation of lithium or sodium into layer-structured TiS2 produces phases in which the alkali-metal cations are mobile in the midst of van der Waals forces, according to the results of an n.m.r. study; this study also confirms the formulation of the phases as xA+TiSx-2 and suggests that the structural type of the intercalation compounds of layered chalcogenides may be related to the ionicity of the A — S and M — S bonds. Two phases CaxTiS2 (0.03 <x<0.50) have been obtained from the reaction between calcium and TiS2 in liquid ammonia. The location of the nitrogen atoms mid-way between the TiS2 layers in TiS2,NH3 lends support to the inference from the observed anisotropy of the proton spin-lattice relaxation in solid TaS2,NH3 that the lone-pair orbitals lie parallel to the MS2 layers and not perpendicular as previously postulated. Cobalt occupies octahedral holes of the sulphur hexagonal close-packing in the empty metallic layers of the TiS2 structure. The sulphur octahedra are distorted and the occupancy ratio for octahedral holes varies from 0.21 to 0.41. The electrical, magnetic, and structural properties of the intercalation phases MxTiS2 (M = Fe, Co, or Ni) have been reported.

Carbides and Silicides. The preparation and structures of titanium carbide single crystals have been reviewed. High purity TiC has been obtained by heating together TiH2 and carbon in the presence of a fatty acid or fatty acid ester. Titanium carbides have been included in a study of solid-phase reactions of high-melting compounds with transition metals and graphite. TiO2 and CO2 are the final products of the oxidation of TiC in an excess of oxygen. The oxidation scale also contains Ti3O5, Ti2O3, and TiO. X-Ray diffraction has detected the presence of titanium oxycarbides at the interface between the TiC and the scale; this indicates the intermediacy of these compounds in the oxidation of the carbide. Substoicheiometric titanium carbides have been prepared from...