Ian A. Oxton

Vibrational frequencies associated with the inter-stitial carbon atoms in the large metal cluster complexes (NMe4)2[Os10C(CO)24] and H2Os10C(CO)24

Abstract Determination of the vibrational frequencies of the interstitial carbon atoms in the metal clusters [Os 10 C(CO) 24 ] 2− and H 2 Os 10 C(CO) 24 , confirmed in the latter by 13 C enrichment, shows that the protonated cluster species exhibits considerable deviation from pseudo-cubic symmetry in the crystal, in contrast to the dianion.

Vibrational spectra of perovskite-type layer compounds. Bis(propylammonium) tetrachloromanganate and -cadmate

Abstract Infrared spectra of the phases of (PrNH 3 ) 2 MnCl 4 and (PrNH 3 ) 2 CdCl 4 occurring at room temperature and below have been measured and are discussed in terms of the structural characteristics of the salts. The lowest-temperature phase of the cadmium salt was found to possess an unusually complex spectrum and possible reasons for this are suggested.

Metal–hydrogen stretching frequencies in metal cluster complexes. The first reported νMH for an interstitial hydrogen ligand

Metal–hydrogen stretching absorptions have been observed in the i.r. spectra of the ions [HRu6(CO)18]– and [DRu6(CO)18]– near 825 and 600 cm–1, respectively, constituting the first reported observation of νMH for an interstitial hydrogen ligand.

Vibrational spectra of perovskite-type layer compounds. Bis(ethylammonium) tetrachlorocadmate and propylenediammonium tetrachlorocadmate

Abstract The infrared spectra of the perovskite-type layer compounds (CH3CH2NH3)2CdCl4 and (NH3CH2CH2CH2NH3)CdCl4 have been measured at temperatures between ambient and 77 K. The first-order phase transition at 216 K in the former salt was observed and appeared to be associated with changes in hydrogen-bond strength and molecular motions. It is shown, in conjunction with the results of earlier studies, that vibrational spectra of alkylammonium perovskite-layer compounds are determined by factor-group symmetry whilst those of the alkylenediammonium salts are simply dependent upon site-group symmetry.

Infrared spectra of crystalline methylsilanes and methylgermanes

Abstract Infrared spectra of polycrystalline CH 3 SiH 3 , CH 3 SiD 3 , CH 3 GeH 3 , CD 3 GeH 3 and CH 3 GeD 3 have been measured at 77 K. Vibrational assignments are in agreement with previous gas-phase studies of these species. The use of isotopically isolated species in the above matrices has shown that the molecular symmetry in each case is C s , and it is suggested that methylsilane and methylgermane are isostructural. Spectra of three of the species were, in addition, obtained in argon matrices. The antisymmetric methyl deformation mode of methylsilane is shown to be involved in Fermi resonance in the gas phase, the crystal and the matrix-isolated form. No firm assignment involving the torsional modes in these species, in the crystal, could be made.

Vibrational frequencies of μ2-bridging carbonyl liganos in metal cluster complexes

Abstract The infrared spectra of a number of metal cluster complexes containing the μ 2 -bridging carbonyl ligand have been measured, and assignments proposed for the lower-frequency modes of this ligand.

Vibrational spectra of halomethylidynetricobalt nonacarbonyl complexes

Abstract Infrared and Raman spectra (1400-100 cm −1 ) are reported for the metal cluster complexes (μ 3 - YC)CO 3 (CO) 9 ; YF, Cl and Br, and vibrational assignments for the YCCo 3 groupings proposed. Approximate force fields have been calculated for these groups and the results are compared with those derived in earlier work on related systems. The unusually high frequencies attributed to carbon-halogen stretching modes in these complexes are shown to result from appreciable coupling of these modes with the symmetric CoC stretching mode.

Vibrational frequencies associated with the μ3-bridging sulphur ligand in some cluster complexes of first-row metals

Abstract Vibrational frequencies of the μ3-bridging sulphur atom in a number of first-row metal cluster complexes have been determined by infrared spectroscopy. the metal-sulphur stretching modes have frequencies in the 350–200 cm-1 spectra region for the sulphur ligand in these complexes. The infrared absorptions associated with these modes are of generally low intensity.

Ammonium ion symmetry in phases II–V of ammonium nitrate

Abstract An existing method for determining the molecular symmetry of the ammonium ion in crystals, formerly limited to low-temperature, i.r. spectroscopy, has been extended by the use of Raman spectroscopy at ambient temperatures and above. The molecular symmetry of the ammonium ion has been deduced in phases II–V of ammonium nitrate, the results for phase II being inconsistent with the site symmetries proposed in diffraction studies.

Vibrational spectra of metal cluster complexes containing the methylidyne ligand. H3Ru3(μ3-CH)(CO)9 and H3Ru3(μ-CCl)(CO)9

Abstract Vibrational spectra of the metal cluster complexes H 3 Ru 3 (μ 3 -CH)(CO) 9 and H 3 Ru 3 (μ 3 -CCl)(CO) 9 have been measured and the vibrations of the central (μ 3 -CY)Ru 3 groupings assigned. The spectra are consistent with approximate C 3 v symmetry of the cluster units in the crystal. Approximate normal-coordinate analyses have been carried out for the (μ 3 -CY)Ru 3 molecular fragments and the derived force constant values are compared with those obtained in similar analyses of the analogous cobalt cluster species.