CHM 501

Homework 4

Due May 2, 2016



1. Mo(pyr)2(CO)4 (pyr = pyridine) has two isomers. Predict the number of IR allowed CO stretching vibrations for each isomer. Based on this, would IR spectroscopy be a useful method to distinguish the two isomers? Why or why not?

2. CoCl2 reacts with DMSO to give the compound [Co(DMSO)6][CoCl4], which is dark blue and has a magnetic moment of 4.6 μB. Account for the color and magnetic moment. Does the O or the S bond to the cobalt? Use a Lewis structure to justify your answer.

3. One synthetic method to prepare substituted chromium carbonyl complexes is photochemical:

Cr(CO)6 + L + hν → Cr(CO)5L + CO

Explain why this is an effective synthetic method using an appropriate bonding theory.

4. [Cr(ox)3]3– has an absorption spectrum with the following bands and molar absorption coefficients:

λmax (cm–1)

ε (L·M–1cm–1)

14,500

2.6

15,300

2.0

17,500

40

20,700

0.3

23,700

67

Find 10Dq and B. Hint: Be sure your response is consistent with the Tanabe-Sugano diagram.