1) Provide explanations for the number of intense perchlorate Cl-O stretching vibrational modes observed in the IR of the following three silver(I) complexes.
a) The perchlorate anion in Ag(NH3)2(ClO4) has a single intense Cl-O stretching vibrational mode observed by IR at 1170cm-1.
b) The IR of Ag(NH3)ClO4 has three Cl-O stretching vibrational modes at 1220 cm-1,1130 cm-1and 920 cm-1 observed in the IR .
c) The IR of AgClO4 has four Cl-O stretching vibrational modes at 1210 cm-1,1140 cm-1 , 1040 and 910 cm-1 observed in the IR .
2) The gas phase cobalt(II) free ion has a 4F ground term which in an octahedral ligand field splits into 4T1g (-0.6 Δo – CI) , 4T2g(+0 .2 Δo) and 4A2g (+1,2 Δo ) electronic states.
a) How many micro states are contained in the 4F ground term of gas phase cobalt(II) free ion and the4T2g electronic state for an octahedral cobalt(II) complex ?
b) What is the ground state for a tetrahedral cobalt(II) complex ?
c) Provide an explanation for the difference in effective magnetic moments between K2[CoCl4] (μeff(298K) = 3.9 β) and K4[CoCl6] (μeff (298K)= 5.0β) . (β = electron Bohr Magneton)
d) What are the Δo and CI values for an octahedral Co(II) complex that has ligand field transitions at Δν1 =7,400cm-1 (4T2g ←4T1g) and Δν2 =15,400cm-1 (4A2g ←4T1g) ?
3 Vanadium tetrachloride (VCl4 ) is a bright red colored liquid with a vapor pressure of 5×10-2 torr at 298K.
a) Briefly discuss why the standard state of VCl4 is a liquid and VCl2 is an ionic solid?
b) How many microstates are in the gas phase V4+ free ion ground term and the V4+ free ion ground J state ?
c) How many microstates are present in the ground electron configuration and ground electronic state for VCl4 assuming tetrahedral symmetry ?
d) State the Jahn Teller Theorem and briefly discuss whether or not VCl4(g) is expected to manifest a Jahn Teller effect .
e) What is the expected orbital angular momentum in the ground
state of VCl4(g) ?
f) The molar magnetic susceptibility (χm) at 298K is +1130×10-6 cm3mol-1 .
What is the effective magnetic moment for VCl4 at 298K and does this μeff fulfill the expectations for VCl4 ground state in Td symmetry ?
g) Use the electric dipole transition selection rules to show whether or not the ligand field ( d→d ) transition(s) for VCl4 are spin and orbitally allowed as pure electric dipole transitions assuming Td symmetry.
h) Write down the irreducible representations for VCl4(g) translations , rotations and vibrations assuming Td symmetry.
3) Provide brief well focused responses to the following questions.
a) Why is Δo for the [Cr(CN)6]3- anion very much larger than Δo for [CrCl6]3-?
b) Qualitatively compare the expected μeff (298K) values for the octahedral complex anions [CrCl6]3- and [Cr(CN)6]3- .
c) The [CoCl4]2- anion is intensely blue colored and [CoCl6]4- is a lightly colored pink.
d) Why is the method of descending symmetry needed to derive an mo diagram for acetylene (ethyne), but not needed for diazene((NH)2)?
e) Why is IR spectroscopy an ineffective method for vibrational studies of homo-nuclear diatomic molecules in the gas phase ?