- Time-of-flight neutron powder diffraction study on the third row transition metal hexafluorides WF6, OsF6, and PtF6
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A neutron diffraction study on the third-row transition metal hexafluorides MF6 (M≡W, Os, Pt) has been performed using the high resolution neutron powder diffractometer (HRPD) at the spallation source ISIS, England. The previously unknown structures of the low-temperature phases of OsF6 and PtF6 are reported. WF6, OsF6, and PtF6, which exhibit a (5dt2g)0, (5dt2g)2, and (5dt2g)4 electronic configuration, respectively, are found to be isostructural and crystallize in the UF6 structure, space group Pmnb, (No. 62). The geometry of the MF6 molecules is to good approximation octahedral for each compound, the mean M-F bond length increasing only slightly from 182.5 (W) to 185.0 (Pt). For WF6 deviations from ideal octahedral geometry are only marginally significant [181.8(2) to 183.2(2) pm] and may be interpreted on the basis of packing effects. Deviations for the d2 complex OsF6 are somewhat larger [181.5(2) to 184.4(3) pm] and may be assumed to be caused by packing effects essentially the same as for WF6, in addition to a first-order Jahn-Teller effect arising from the (5dt2g)2 electronic configuration. While eliminating the effects of packing by a comparison of individual M-F bond lengths for WF6 and OsF6, the OsF6 molecule shows to have D4h symmetry with two apical M-F bonds about 1.8 pm longer than the four equatorial bonds as a result of the Jahn-Teller distortion. Only small deviations from ideal octahedral geometry [184.4(3) to 185.8(3) pm] are found for the d4 complex PtF6. Within the series W to Pt a substantial shortening of the F...F van der Waals contact distances is observed. This shortening more than compensates for the increase in the M-F bond lengths and leads to unit cell volumes and cell parameters decreasing continuously from W to Pt. The variation of F...F contact distances and M-F bond lengths may be rationalized in terms of polarization of the F-ligands in the field of the highly charged nuclei of the central atoms which are only incompletely shielded by the 5 d electrons.
- Marx,Seppelt,Ibberson
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- Preparation and crystal structures of ruthenium and osmium oxide tetrahalides
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RuOF4 as the highest valence oxide fluoride exist as a molecular compound (a = 606.0(1), b = 836.1(1), c = 626.3(1) pm, β = 91.637(3), Z = 4; P21/n) as well as fluorine bridged polymer (a = 547.7(2), b = 928.5(3), c = 1252.4(3) pm, Z = 8, P212121). A reproducible method for pure, deep blue OsOF4 is given. Pure OsOF4-I is isostructural to the fluorine bridged polymeric RuOF 4 (a = 554.6(1), b = 955.4(2), c = 1278.4(2), Z = 8, P2 12121). OsOF4-II is also a fluorine bridged polymer (a = 537.8(2), b = 1274.8(4), c = 555.2(2), β = 117.716(6)°, Z = 4, P21/c). OsOCl4 again is a molecular species (a = 938.9(2), b = 561.3(1), c = 1192.0(2), β = 109.944(4)°, Z = 4, P21/c).
- Shorafa, Hashem,Seppelt, Konrad
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- Plasmachemical synthesis of the binary hexafluorides of Mo, Os, Ir, Te, and U
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Starting from the respective metal, we have synthesized the binary hexafluorides MF6 of M = Mo, Os, Ir, Te, and U by the use of a remote fluorine plasma source using a mixture of Ar and NF3 as the feed gas. The formation of the binary hexafluorides was confirmed by several different spectroscopic methods including IR, Raman, UV/VIS, and NMR spectroscopy.
- Buchner, M. R.,Chemnitz, T.,Kraus, F.,Petry, W.
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- Osmium(VII) fluorine compounds
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Of the four published osmium fluorine compounds in the oxidation state +7, OsO3F, OsO2F3, OsOF5, and OsF 7, only one (OsOF5) is a real Os(VII) compound. OsO 3F has obviously been OsO4. OsO2F3 in its two modifications is a mixed-valence Os(VI)/Os(VIII) compound, whereas a new compound Os2O3F7 is a mixed-valence OsV/Os(VIII) compound. The molecular structures of OsO3F, OsO 2F3, and OsO3F2 are calculated. OsO3F2 seems to exist in two forms, with D3h and Cs symmetry. The original preparation of OsF7 could not be reproduced, only OsF6 has been obtained.
- Shorafa, Hashem,Seppelt, Konrad
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p. 7929 - 7934
(2008/10/09)
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- Spectroscopic Studies on the Hexafluorides of Rhenium, Osmium, Iridium, and Platinum isolated in Low-temperature Matrices
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The compounds ReF6, OsF6, IrF6, and PtF6 have been isolated as monomeric species in inert-gas matrices at low temperatures, and characterised by i.r. spectroscopy.Subsequent u.v.-visible studies reveal a complex pattern of electronic absorptions, and a detailed assignment of these in terms of charge transfer, d-d, and intra-configurational transitions is presented.
- Holloway, John H.,Stanger, Gillian,Hope, Eric G.,Levason, William,Ogden, J. Steven
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p. 1341 - 1346
(2007/10/02)
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