IR‐spektren und kraftkonstanten von molybdän‐ und wolframhalogenverbindungen mit M₆X₈‐gruppen

Abstract

Die Infrarotspektren einer Reihe von Verbindungen des Typs M6X8L4 (M = Mo, W; X = Cl, Br; L = Cl, Br, J) wurden im Bereich von 450 bis 33 cm−1 untersucht. Eine Normal‐koordinatenanalyse ermöglichte eine eindeutige und vollständige Zuordnung. Dabei wurden Kraftkonstanten für die einzelnen Bindungen erhalten. Die Kraftkonstante der Metall—Metall‐Bindung beträgt 0,3 mdyn/Å.

Preparation and Spectroscopic Investigations of Mixed Octahedral Complexes and Clusters

“…As already demonstrated for mononuclear octahedral mixed-fluoro complexes, 19 F NMR spectroscopy is a very specific, sensitive, and high-resolution method for the elucidation of reactions, the structures of the reaction products and the distribution of the individual species within a series (see section II.D). Therefore the application of this technique to the more complicated mixed hexanuclear metal halide clusters was very obvious, because these systems could not be completely analyzed in previous studies. ,,, The respective terminal members of possible series, [(M 6 X i 12 )Y a 4 ] or [(M 6 X i 12 )Y a 6 ] 4- and [(M 6 X i 8 )Y a 4 ] or [(M 6 X i 8 )Y a 6 ] 2- , Y = X or Y ≠ X, have been studied extensively by X-ray structure analyses 372-379 and by electronic and vibrational spectroscopy. , Apart from the condition Y ≠ X, the three cluster units of [(M 6 X i 8 )Y a 6 ] 2- are known from Mo and W (see Figure c) and present three opportunities for systematic variations. Firstly, the outer octahedral coordination sphere Y a 6 can be a mix of two ligands, which results in 10 species, where, preferentially, one of the outer sphere ligands is F to allow for 19 F NMR spectroscopy.…”

Vibrational spectra of intra- and inter-metal and semimetal bonds

“…Relatively low-frequency infrared-active KMo-Mo) assignments have also been made for Mo6C18C14 (99 cm-1), Mo6Cl8Br4 (99 cm-1), and Mo6Br8Br4 (85 cm-1) with the Mo-Mo stretching force constant given as 0.3 mdyn/A for each of these compounds. 238 Infrared spectra have been reported for the series W6X8Y6-n"-2 (X = Cl, Br, I; Y = F, Cl, Br, I; = 0, 2).239…”

“…In another Raman study, a band at 124 cm-1 is assigned to the v(Mo-Mo) mode of Cs2(Mo6C18C16). 238 The sample used in this study, however, was in the solid state and no polarization data are reported. Some of the assignments made in the previous studies241-243 have been questioned recently since it is felt that definite assignments cannot be made without normal coordinate calculations which take into account the mixing of normal vibrations and which are based on more complete vibrational data, including Raman spectra.…”

Study of some hexanuclear mixed-metal cluster compounds containing tantalum and molybdenum

“…As a precedent for this contention. Mattes (63) has noted from his own work and references (57,59, Further examination of the data in Table 4 …”