ADVANCED INORGANIC CHEMISTRY QUIZ 5 and FINAL December 18, 2012 INSTRUCTIONS: PRINT YOUR NAME > NAME. QUIZ 5 : Work 4 of 1-5 (The lowest problem will be dropped) FINAL: #6 (10 points ) Work 6 of 7 to 14 (15 points each, the lowest two problem will be dropped) USE THE CORRECT NUMBER OF SIGNIFICANT FIGURES YOUR SUPPPLEMENTAL MATERIALS CONTAIN: A PERIODIC TABLE POINT GROUP FLOW CHART An Oh POINT GROUP CHARACTER TABLE Quiz 5 R = 0.08206 lit-atm/mol-k 1 (25) R = 8.3145 J/mol-K 2 (25) 3 (25) c = 2.9979 X 10 8 m/s 4 (25) h = 6.626 X 10-34 J-s TOTAL(100) 5 (25) Final J = (kg-m 2 )/s 2 6 (10) 7 (15) 8 (15) 9 (15) 10 (15) 11 (15) 12 (15) 13 (15) 14 (15) TOTAL(100)
1. Give a short answer to the following: (a) What are the four most common geometries for coordination numbers 4, 5, and 6? (one coordination number has two answers) (b) What is the most common reason for very low coordination numbers (1,2 or 3)? (c) Define linkage isomerization and give one example of a ligand that can form linkage isomers. (d) Draw all the possible isomers of [Co(NH 3 ) 3 Cl 2 Br]. There are three isomers. Make sure that each isomer is unique and can not be rotated into another. Draw your structures in the orientation of the template provided. (e) Explain why a tris chelate such as [Co(en) 3 ] 3+ is chiral.
2. Give a short answer to the following: (a) Describe the approach of the three main theories of transition metal complex electronic structure: Short answers please. Valence bond Crystal field - Ligand field- (b) Explain why d 8 complexes are most commonly square planar. (c) The ΔG of formation for two complexes of Ni 2+ are given below: [Ni(NH 3 ) 6 ] 3+ ΔG f = -49.2 kj/mol [Ni(en) 3 ] 3+ ΔG f = -104.4kJ/mol en = H 2 N-CH 2 -CH 2 -NH 2 Why does [Ni(en) 3 ] 3+ a much more stable complex? (d) Why are there no high spin tetrahedral complexes? (e) Explain how a π acceptorr ligand (high energy empty π orbitals) increase the value of Δ o
3. Ni 2+ forms four coordinate complexes with chloride and cyanide ligands. [NiCl 4 ] 2+ has a magnetic moment corresponding to two unpaired electrons.. [Ni(CN) 4 ] 2- is found to be diamagnetic. Assign the geometries to these two complexes. 4. We did not consider the orbitals for a trigonal bipyramidal transition metal complex (D 3 h) The sigma only orbitals create a reducible representation E 2C 3 (z) 3C 2 h (xy) 2S 3 3 v Γ = 5 2 1 3 0 3 This reduces to 2A 1 + E + A 2 Using the D 3 h character table, determine which d orbitals interact with the sigma group orbitals and which if any are non-bonding. 2A 1 E A 2 nonbonding Sketch the d orbital splitting labeled with the name of the d orbital and the symmetry. The ligand lone pairs are of lower energy than the d orbitals so any d orbitals that interact will move in an anti-bonding direction. D 3 h splitting d orebitals
5 In the molecular orbital treatment of an octahedral complex metal we found that the d orbitals split in the presence of the ligands into two sets with the following energy level order: e g t 2g The size of the splitting is determined by the ligands. Ligands like H 2 O and F -, Cl -, Br -. And I -. tend to cause small splittings (they are weak field ligands) Ligands like CN -, CO, of NH 3 tend to cause large splittings (they are strong field ligands). For a tetrahedral complex the order of the energies of the d orbitals is reversed t 2 e Determine the orbital occupancies for the following species, and the number of unpaired electrons Orbital occupancies # unpaired electrons? (a) [Fe(H 2 O) 6 ] 2+ (b) [Cr(CN) 6 ] 4- (c) [Cr(OH 2 ) 6 ] 2+ (d) [Co(NH 3 ) 6 ] 3+ (e) [Ni(NH 3 ) 4 ] 2+
6 Give a short answer for the following: (a) Write the electron configuration for th following atoms or ions: P Re Se 2- Zr 4+ Mn 2+ (b) For the quantum mechanical particle in a box of length a. V = infinity for x < 0 and x > a and V = 0 when x is between 0 and a 0 > x > a. Sketch the wavefunction ( the square of the wavefunction ( 2 ) for n = 4 (c) What are the conditions for a molecule to be chirtal
7. Using Slater s Rules for calculating S, (Shielding) listed below: 1. The electronic structure of the atom is written in groupings as follows: (1s) (2s, 2p) (3s, 3p) (3d) (4s, 4p) (4d) (4f) (5s, 5p), and so on. 2. Electrons in higher orbitals (to the right in the list above) do not shield those in lower orbitals. 3. For ns or np valence electrons: a. Electrons in the same ns, np level contribute 0.35, except the 1s, where 0.30 works better. b. Electrons in the n-1 level contribute 0.85. c. Electrons in the n-2 or lower levels contribute 1.00. 4. For nd and nf valence electrons: a. Electrons in the same nd or nf level contribute 0.35. b. Electrons in groupings to the left contribute 1.00. (a) Calculate the Z* for the 2s electron in Co (b) Calculate Z* for a 4s electron in Co. (b) Calculate Z* for a 4s electron in V. (c) The first ionization energies for are V = 650 kj/mol and for Co = 760 kj/mol. Does your calculations in (b) and (c) support or oppose these values. Why?
8. Answer the following: (a) Why does Al have a large radii than B? (b) Why does F have a larger first ionization energy than B? (c) Why is a sulfide ion, S 2-, have a larger radii the sulfur, S, atom? (d) How does the description of the electron differ in the Bohr model and the quantum mechanical model of the atom? (e) Why is the 2 nd ionization energy always higher the the 1 st ionization energy? 9Draw a valid Lewis structure and determine the shape of the following molecules or ions using the VSEPR theory. Assign formal charges to the atoms of the species that are ions.. WRITE THE NAME OF THE SHAPE (a) SF 2 (b) SO 2 - (c) TeF 4 2- (d)clo 3 - (e) CO 3 2- (f) SF 4
10. There are several possible structures for the thiocarbonate ion, SOCN(CH 3 ) 2 -, whose skeletal structure is shown below. Draw three resonance structure for this ion. Assign formal changes to S, O, N and the non-methyl C atom. Determoine the best resonance structure and explain why. The order of electronegativity is: C = S < N < O 2.5 2.5 3.0 3.5 11 Assign point group to the following molecules or ions. (a) Ignore H (b) (c) CO 3 2- Bonds are equivalent (d) PF 3 (e) HCN (f) BrF 5 (g)allene
12 This problem does the total vibrational analysis for hydrazine, N 2 H 4 (point group C 2 v). (a) A reducible representation may be generated by performing the symmetry operations on the molecule with a coordinate system attached to each atom. If a vector remains in the same place it contributes +1 to the character. If a vector goes to the negative of itself, it contribute -1 to the character. If an atom is move in space by the symmetry operation, it contributes 0 to the character. The view of the molecule show is down the z axis. The N atoms are in the plane of the page and the H atoms are below the page. The coordinate system on each atom is z is pointing straight at you (the z vectors are not shown), x points to the right, and y points up the page from the bottom to the top. The coordinate system of the point group is shown with bold arrows. The z axis is shown as a circle. It is pointing at you. You must determine the character each symmetry operation. Do not forget the z vector on each atom. They are not shown oin the figure, but must be included in the count. E C 2 z v(xz) v(yz) = _18 BRING IT TO ME TO GRADE BEFORE CONTINUING TO PART (B)
12. (continued) (b) Reduce the reducible representation. C 2v E C 2 (z) v(xz) v(yz) linear, rotations quadratic cubic A 1 +1 +1 +1 +1 z x 2, y 2, z 2 z 3, x 2 z, y 2 z A 2 +1 +1-1 -1 R z xy xyz B 1 +1-1 +1-1 x, R y xz xz 2, x 3, xy 2 B 2 +1-1 -1 +1 y, R x yz yz 2, y 3, x 2 y (c) Determine the symmetry of the vibrational modes of the molecule by subtracting out the translations and rotations. (d) Confirm that you found the expected number of vibrations based on the number of atoms. (e) Which modes are IR active? Which are Raman active? Which are neither?.
13 (a) Sketch the energy levels diagram for diatomic molecules both s-p mixing and without s-p mixing. Label the orbitals with σ π σ* and π* (b) Using the appropriate diagram populate the energy levels with electrons for B 2 in one diagram and O 2 in the other diagram. (c) Calculate the bond order for each species (d) Which if any of the three species is paramagnetic? (e) Sketch the one of the π and π* orbitals.
14. The first step in the molecular orbital treatment of NO - 2 is the formation of the group molecular orbitals from the atomic orbitals on oxygen. Separate group orbitals can be formed from the pairs of s, px, py and pz orbitals on the oxygens. The moleculae has C 2 v symmetry. The molecule lies in the xz plane. C 2v E C 2 (z) v(xz) v(yz) linear, rotations quadratic cubic A 1 +1 +1 +1 +1 z x 2, y 2, z 2 z 3, x 2 z, y 2 z A 2 +1 +1-1 -1 R z xy xyz B 1 +1-1 +1-1 x, R y xz xz 2, x 3, xy 2 B 2 +1-1 -1 +1 y, R x yz yz 2, y 3, x 2 y Carry out the symmetry operations on the orbitals below to create reducible representations. SETs 1, 2, and 3 have the same reducible representation. Set 4 is different. Treat the orbitals on oxygen as two separate atomic orbitals. If an orbital moves it contributes 0 to the reducible representation. If it stays in place and is the same it contributes 1 to the character. If it stays in place and goes to the negative of itself it contributes -1 to the character. Hint: The only possible characters are 0, 2, and -2. I have done set 1 and 2 z y E C 2 z xz yz x 1 2 same as SET 1 3 same as SET 1 4
5(cont) Reduce your four representations to irreducible representations and determine which atomic orbitals on N go with each symmetry of the group orbitals.. You can probably do the reduction by inspection. C 2v E C 2 (z) v(xz) v(yz) linear, rotations quadratic cubic A 1 +1 +1 +1 +1 z x 2, y 2, z 2 z 3, x 2 z, y 2 z A 2 +1 +1-1 -1 R z xy xyz B 1 +1-1 +1-1 x, R y xz xz 2, x 3, xy 2 B 2 +1-1 -1 +1 y, R x yz yz 2, y 3, x 2 y SET 1 or 2 o 3 reduces to and interacts with atomic orbital on N SET 4 reduces to and interacts with atomic orbital on N Set 1 forms two groups orbitals analogous the hydrogen group orbitals in water. Sketch the bonding and antibonding interactions of these two groups orbitals Orbital 1 Orbital 1 Bonding Antibonding Orbital 2 Orbital 2 Bonding Antibonding Interaction of SET 3 orbitals with N are very weak, why?
(x axis coincident with C' 2 axis) D 3h E 2C 3 (z) 3C' 2 h (xy) 2S 3 3 v linear, rotations quadratic A' 1 +1 +1 +1 +1 +1 +1 - x 2 +y 2, z 2 A' 2 +1 +1-1 +1 +1-1 R z - E' +2-1 0 +2-1 0 (x, y) (x 2 -y 2, xy) A'' 1 +1 +1 +1-1 -1-1 - - A'' 2 +1 +1-1 -1-1 +1 Z - E'' +2-1 0-2 +1 0 (R x, R y ) (xz, yz) C 2v E C 2 (z) v(xz) v(yz) linear, rotations quadratic cubic A 1 +1 +1 +1 +1 z x 2, y 2, z 2 z 3, x 2 z, y 2 z A 2 +1 +1-1 -1 R z xy xyz B 1 +1-1 +1-1 x, R y xz xz 2, x 3, xy 2 B 2 +1-1 -1 +1 y, R x yz yz 2, y 3, x 2 y