Ques to find point groups in group theory chemistry
Answers
Find the point groups for:
(a) trans-PtCl2(NH3)2 (square planar Pt; ignore the H's)
(b) cis-[CrCl2(H2O)4]
+
(octahedral Cr; ignore the H's)
(c) XeF2 (d) XeF4
M
H2N
N
H2
N
N
NH2
NH2
H
H
M
Br
Cl Cl
Br
Cl
or Br M
H2N
H2N
H2
N
N
H2
NH2
NH2
g)
or
For e, f, and g, it will help to build the molecules; you may need to build two
models of each one, so you can confirm that a symmetry operation doesn't
change the structure. If you don't have enough atoms in your kit, do it with a
classmate. Assume the ligand N~N has CH2 linkers, as shown. To see the
symmetry of (e) more conveniently, play with paper and scissors as on the next
page.
(h) ferrocene (eclipsed conformation)
(i) ferrocene (staggered conformation) See the text pp. 124-125 for helpful
pictures.
3. Give the symmetry designations of the s, p, and d metal orbitals for each
molecule in problem 2, parts a-i. [Hint, look in the character tables!]
Give the point groups of these molecules, using VSEPR to find their structure
if needed.
i. benzene ii. chlorobenzene
iii. 1,2-dichlorobenzene iv. 1,4-dichlorobenzene
v. 1,3,5-trichlorobenzene vi. 1,3-dichlorobenzene
vii. B2Cl4 (planar, with a B-B bond) viii. [InCl5]
2–
ix. [SnCl3]–
x. cis and trans N2F2 (planar, with N-N double bonds)
xi. NSF xii. I3+ and I3–
5. (a) Consider the square pyramidal complex [VOCl4]
2-. Using a vector placed
along the V-O bond, determine the symmetry of the V-O stretching vibration.