Peter J. Jones

The interaction of some metal dichlorides (Ca, Cr, Mn, Fe, Co, Ni, Zn) with dinitrogen

Abstract The dichlorides of Ca, Cr, Mn, Fe, Co, Ni and Zn have been isolated in argon and nitrogen matrices and examined by infrared spectroscopy in the range 4000-200 cm −1 . The results obtained are discussed in relation to the behaviour of the difluorides and the monoxides. Both CoCl 2 and NiCl 2 show anomalous shifts in the frequency of v 3 between argon and nitrogen matrices. Isotopic substitution shows that these molecules are strongly bent in nitrogen matrices, in contrast to their behaviour in argon matrices. It is likely that the primary interaction between the host nitrogen matrix and the guest dichloride is ion—induced-dipole rather than the formation of a discrete MCl 2 ·N 2 species.

A quantitative study of the aluminium trichloride–acetonitrile system using X-ray crystallography, electrical conductivity, aluminium-27 and chlorine-35 nuclear magnetic resonance and Raman spectroscopy. The characterization of the pentakis(acetonitrile)chloroaluminium(III) ion in the solid state and in solution

The compounds MCl3(M = Al, Ga, or In) yield electrically conducting solutions in acetonitrile. Boron trichloride gives non-conducting solutions and, contrary to previous work, this is interpreted as due to the presence of a molecular solute BCl3·MeCN. The electrical-conductivity data for AlCl3 in acetonitrile are discussed in detail and it is shown that from the results obtained it is not possible to differentiate between 1 : 1 and 1 : 2 electrolyte behaviour. Quantitative Raman and 27Al n.m.r. spectra demonstrate that ca. 70% of the aluminium in solutions of AlCl3 in acetonitrile is present in the form of [AlCl4]–. An X-ray single-crystal study of the solid adduct AlCl3·2MeCN crystallizing from such a solution shows that this adduct is correctly formulated as the auto-complex [AlCl(NCMe)5]2+2[AlCl4]–·MeCN. Further 27Al n.m.r. studies on solutions of Al[ClO4]3 in acetonitrile and of the solute AlCl[ClO4]2, in conjunction with the work on AlCl3 demonstrate that [AlCl(NCMe)5]2+ is the major cationic constituent of aluminium trichloride solutions in acetonitrile. The electrical-conductivity, Raman, and n.m.r. data on these solutions are all satisfactorily interpreted by the principal ionization scheme [AlCl(NCMe)5]2+2[AlCl4]– which is the formulation found for the crystal. The ionization of AlCl3, but the non-ionization of BCl3, in solution in acetonitrile is attributed principally to the ability of aluminium to adopt a co-ordination number of greater than four in ions such as [AlCl(NCMe)5]2+.

Nickel dichloride: A nonlinear molecule in a nitrogen matrix? Implications for structure determinations in cryogenic matrices

Nickel dichloride is found to be a strongly bent molecule (bond angle c. 130°) in a nitrogen matrix using 58/60Ni and 35/37Cl isotopic data on v 3 coupled with the harmonic approximation. In the case of the 35Cl/37Cl experiment the intense central component of the triplet in a 1:1 enrichment is effectively eliminated by a novel vaporization technique. These results demonstrate a change in shape with matrix gas and cast doubt on structural determinations in matrices, notably for co-ordinatively unsaturated molecules or where bonding forces are not highly directional.

Coordination chemistry of higher oxidation states. 10 [1]. Oxofluoroanions of osmium(VIII) [OsO4F2]2− and [OsO3F3]−

Abstract Trioxotrifluoroosmates(VIII) M[OsO 3 F 3 ] (M = Cs, Rb, K) have been prepared by direct combination of OsO 3 F 2 and the appropriate alkali fluoride MF. The reaction of OsO 4 with M′F (M′ = Cs, Rb) in aqueous solution produces the tetraoxodifluoroosmates(VIII) M′ 2 [OsO 4 F 2 ]. On the basis of their vibrational spectra the assignment of a fac (C 3v ) structure to [OsO 3 F 3 ] − and a cis (C 2v ) to [OsO 4 F 2 ] 2− is proposed. The electronic spectra of the anions have been recorded and are interpreted using the optical electronegativity concept.

The identification of InOH in the gas phase and determination of its geometric structure

The first gas phase observation of the species InOH is reported through the detection of its electronic spectrum in the near ultraviolet region, between 345 and 377 nm. The molecule was generated by the high temperature reaction between H2O and In metal or between H2 and In2O3, and cooled in a free jet expansion. Two separate electronic transitions have been identified and are tentatively assigned as α1A’←X1A’ and β1A‘←X1A’. Values for the vibrational wavenumbers ν2 (bending vibration) and ν3 (In–O stretching vibration) have been determined for InOH and InOD in all three electronic states involved. There is evidence that the molecule is quasilinear in its ground electronic state which somewhat complicates the values determined for ν2 in this state. Rotational structure was easily resolved at the lowest temperature achieved in this work (Trot≊12 K). Analysis of this structure shows that the molecule is bent in all of the electronic states studied, with a bond angle of about 132° in the X state and about...

Matrix-isolation infrared and ultraviolet-visible studies on some transition-metal pentachlorides and pentabromides

Samples of the solids NbCl5, NbBr5, TaCl5, TaBr5, ReCl5, ReBr5 and OsCl5 have been vaporised in vacuo, and the products characterised by mass spectrometry and IR and UV/VIS spectroscopy in low-temperature argon and nitrogen matrices. In particular it is shown that vaporisation of the d0 species leads to the production of simple monomers, which adopt a square-pyramidal shape in nitrogen and a variety of conformers in argon. Rhenium pentachloride vaporises as a monomer which exhibits D3h symmetry in both argon and nitrogen, but ReBr5 and OsCl5 decompose, the former to yield molecular Re3Br9.

THE INFRARED-SPECTRA OF MATRIX-ISOLATED THORIUM AND URANIUM TETRACHLORIDES - CHANGE OF SHAPE WITH MATRIX GAS

When thorium or uranium tetrachlorides are isolated in neon matrices, the spectra can be interpreted in terms of a Td molecule with a small site effect. Spectra obtained using sputtering techniques to generate ThCl4 in argon matrices agreed with those obtained previously using conventional vaporisation techniques. Detailed calculations of the i.r. spectra of isotopically enriched and natural abundance Th35/37Cl4 show that in krypton ThCl4 is not tetrahedral.

Spectroscopic studies on the higher binary fluorides of chromium: CrF4, CrF5, and CrF6, both in the solid state and isolated in inert gas matrices

Pure samples of CrF4, CrF5, and CrF6, together with the related salts CsCrF6, and Cs2CrF6, have been prepared, and a number of spectroscopic measurements made. In particular, the solid state i.r. and u.v.–visible spectra of CrF4 and CrF5 indicate fluorine-bridged polymeric structures, whilst CsCrF6 and Cs2CrF6 contain essentially discrete CrF6 units. Matrix isolation studies on CrF4 and CrF6 lead to the identification of molecular CrF4(Td) and CrF6(Oh) which are characterised by intense i.r. bands at 784.3 and 763.2 cm–1 respectively (argon matrices); the vaporisation of CrF5 is shown to yield CrF4+ CrF6 by disproportionation. The u.v.–visible spectrum of CrF6 contains prominent charge-transfer bands at ca. 38 450 and ca. 26 700 cm–1.

Notes. The infrared spectra of alkali metal hexafluorouranates(V). An example of dependence of molecular geometry on matrix gas

Potassium, rubidium, and caesium hexafluorouranates(V) are vaporised at temperatures of the order of 400 °C. The vapours are co-condensed with argon or nitrogen as matrix gases. Infrared spectra suggest a C3v symmetry for the species isolated in argon and a C2v symmetry in nitrogen. In the case of sodium hexafluorouranate(V) the spectra are complicated by decomposition reactions leading to uranium pentafluoride as one of the products.

Characterisation of chromium(VI) oxide tetrafluoride, CrOF4, and caesium pentafluoro-oxochromate(VI) Cs[CrOF5]

The title compounds have been characterised by elemental analyses, i.r. And u.v.–visible spectroscopy, and some of their reactions are described. Matrix isolation studies on CrOF4 show characteristic i.r. absorptions at 1 027.7 and 746.3,741.6 cm–1 in nitrogen matrices, which are assigned as the A1(CrO) and E(Cr–F) modes respectively of the C4v monomer. Chromium isotope fine structure and relative intensity estimates suggest a bond angle of ca. 106° for OCrF. The electronic spectrum of matrix-isolated CrOF4 shows prominent charge-transfer bands at 40 000 and 27 000 cm–1.