Mo=O stretching frequencies

The various sulfinate isomers are usually distinguishable by the S-O stretching frequencies Although O- and 0,0 -sulfinate isomers are generally isolated from SO2 insertion reactions with non-transition and early transition metals such as Ti and Zr for the mid and late transition elements S-sulfinates predominate. However, exceptions exist, e.g. the O-sulfinate compound [Ni(02SCH3)(p3)](BPh4) . Work by Wojcicki and others has proven that many (if not all) SO2 insertions with Mo, Mn, and Re complexes proceed via O-sulfinate intermediates, which can subsequently rearrange to more stable... 

Which compound should exhibit the higher C—O stretching frequencies (7t-C5H5)Mo(CO)3H or (tc-C5H5Mo(CO)2NO ... 

The infra-red spectrum of Mo(CO)3[P(OCH3)3]3 (VIII) shows three absorption bands at 1993,1919, and 1890 cm-1 in the region in which CO stretching frequencies usually appear. But Cr(CO)3(CNCH)3 (IX) has two absorption bands in the C—O stretch region at 1942 and 1860 cm-1. Octahedral ML3(CO)3 complexes can exist in either the mer or fac isomeric forms (Figure 9.2). Assign the structures of the above two molecules. How many bands would you expect to see in the vibrational Raman spectra of these two molecules, and for which of these bands would the scattered Raman radiation be polarized ... 

The ketonic description of the C-O bond is supported by its length and stretching frequency but the M-C bonds should not be seen as simple a bonds. An MO description involving three-centre bonding is required, and it is noteworthy that a carbonyl bridge between two atoms always involves a direct M-M bond. One, two or three CO molecules may bridge two M atoms, as shown in the examples below ... 

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