Portal de Periódicos da CAPES

Darstellung und spektroskopische Charakterisierung von Hexachloroosmat(V) / Preparation and Spectroscopical Characterisation of Hexachloroosmate(V)

1983; De Gruyter; Volume: 38; Issue: 6 Linguagem: Inglês

10.1515/znb-1983-0604

1865-7117

W. Preetz, Michael Bruns,

Organometallic Compounds Synthesis and Characterization

Abstract (TEA)[O S Cl 6 ] is formed quantitatively by heating solid trans-(TEA)[OsX 4 (CO) 2 ] (X = Br, I) in a stream of chlorine at 120 °C, and can be purified by recrystallisation from CH 2 Cl 2 without decomposition. It is reduced immediately by acetone, methanol, Cl - , Br - , I - to give [OsCl 6 ] 2- . The standard potential [OsCl 6 ]-/[OsCl 6 ] 2- in acetonitrile referred to the saturated mercury-mercurous sulphate electrode is 0.840 V. The IR and Ra bands of (TEA)[OsCl 6 ], assigned according to point group Oh, are shifted to higher frequencies compared with (TEA)2[OsCl 6 ]. The excitation at 488.0 nm gives a resonance Raman spectrum exhibiting 6 overtones of vi and combination tones up to 4ν 1 + v 5 . The electronic absorption spectrum shows five spin-forbidden intraconfigurational transitions coupled with odd vibrational modes in the near infrared region. The spin-allowed 4 A 2g → 4 T 2g , 4 T 1g -transitions are observed at 347 and 305 nm. The excited levels can be fitted with the parameters ⊿ = 28500 cm -1 , B = 340 cm -1 , ξ = 2500 cm -1 , allowing to calculate the nephelauxetic ratio β 55 to 0.47. In the visible region extensive charge transfer transitions are observed. Based on the strong oxidizing character of Os(V) there is a bathochromic shift of corresponding bands of [OsCl 6 ]- in relation to [OsCl 6 ] 2- of about 6600 cm -1 and to the isoelectronic [ReCl 6 ] 2- of about 13700 cm -1 , respectively. From πt 1u →dt 2g the optical electronegativity is calculated to X opt (Os v ) = 2.49.