9. You come across a flask in the laboratory containing a red foul-smelling liqu
ID: 1083839 • Letter: 9
Question
9. You come across a flask in the laboratory containing a red foul-smelling liquid. A label found on the floor nearby has the formula Fe(CO)s written on it, but you are unsure if this label goes with this flask. You are concerned about safe storage of the liquid, and so you collect its IR spectrum, finding two bands at 2000 and 2022 cm-1 (a) What is the idealized molecular geometry and point group of Fe(CO)%? (2 pts) (assume only CO groups around iron) (b) How many bands do you predict in vibrational spectroscopy for the C-O stretches? What are the symmetry species designations for each? Which ones will be IR active? Raman active? Both? Do any of the bands contain degenerate contributions? (11 points)Explanation / Answer
(a)The idealized molecular geometry of Fe(CO)5 is trigonal bipyramidal having D3h point group.
(b)The vibrational spectroscopy for the C-O stretch will have two bands. The symmetry designations are A2'' and E'.
A2'' is only IR active whereas E' is both IR and Raman active. Yes, only E' contains degenerates contribution.
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