Experimental and Computational Studies of the Metal−Metal Stretching Vibration in X3M⋮MX3 Compounds (X = Alkoxide, Alkyl, Amide)

• Published in: Inorganic chemistry 2004-03, Vol.43 (5), p.1762-1769
• Main Authors: Gilbert, Thomas M, Littrell, John C, Talley, Chad E, Vance, Michael A, Dallinger, Richard F, Rogers, Robin D
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic030246f

Raman spectra of a number of triply bonded M2X6 (M = Mo, W; X = alkoxide, alkyl) compounds have been obtained. Several exhibit a band assignable to the metal−metal stretching vibration νM ⋮ M. This band was not identified in earlier studies of the M2(NMe2)6 compounds. We have attempted to correlate the Raman vibrational data with structural data from single-crystal X-ray diffraction studies. Diffraction studies of the M2(O-1-4-pentyl[2.2.2]bicyclooctyl)6 species show a crowded environment around the dimetal core, but the M−M−O angles differ substantially from 90°. Thus, this angle does not solely determine the extent to which the metal−metal and ligand-based vibrational modes couple and, in turn, our ability to observe νM ⋮ M. Computational studies of model systems confirm the assignment of the band as being νM ⋮ M, although the predicted vibrational energies are consistently too high by ca. 7%. The computational results suggest that a νM ⋮ M band may be present in the published spectra of the M2(NMe2)6 pair.