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ADVANCED INORGANIC CHEMISTRY December 6, 2006 INSTRUCTIONS: PRINT YOUR NAME ————> NAME QUIZ 4 . WORK ALL 5 TOTAL = 100 SHOW YOUR WORK FOR PARTIAL CREDIT USE THE CORRECT NUMBER OF SIGNIFICANT FIGURES THE LAST TWO PAGES ARE A PERIODIC TABLE AND A SCRATCH SHEET QUIZ 4 R = 0.08206 lit-atm/mol-K R = 8.3145 J/mol-K h = 6.626 X 10-34 J-s 1 2 10 15 3 25 c = 2.9979 X 108 m/s 4 25 5 25 J = (kg-m2)/s2 TOTAL(100) QUIZ 5 R = 0.08206 lit-atm/mol-K R = 8.3145 J/mol-K h = 6.626 X 10-34 J-s 1 2 25 25 3 25 c = 2.9979 X 108 m/s 4 J = (kg-m2)/s2 TOTAL(100) 25 25 1. Several species of diatomic molecules and ion are formed between C and N. The molecular orbital diagram is that for diatomic with s-p mixing. Consider the following species CN+, CN, and CN-. (a) Draw the molecular orbital diagram that is appropriate for these species. You only need to draw one diagram showing the energy levels, but label the orbitals with σ, σ∗, π, and π∗ (b) Draw the shape of the lowest σ orbital. Which atom contributes the greatest character to this orbital? (c) Draw the shape of one of the π* orbitals. Which atom contributes the greatest character to this orbital? (d) Calculate the bond order of the three species. CN+ CN CN-. (e) which species has the longest bond distance? _____________ Which has the greatest bond energy?____________________ 2. Suggest an appropriate hybridization scheme for the central atom of the following molecules of ions: (a) PF5 (b) XeF4 (d) OCN- (e) H2CO (C atom is central (C atom is central (c) PF3 (f) O2 3. The bonding in the molecule PF5 (D3h point group) can be described by molecular orbital theory. (This problem goes over two pages) z Location of symmetry elements F F C3 S3 – z axis F C2 – along each P-F bond (x axis is one) P F x σh – xy plane σv - plane of 2 axial F’s and one equatorial F (xz plane is one) F y If we consider only the sigma bonding we can use the s orbitals on F to form a reducible representation to form group orbitals. Fill in the table for the reducible representation, Γ, below by performing the symmetry operations and counting the number of s orbitals that do not move. I have filled in the first value. (Hint when you sum all the characters the total is 14) Transfer reducible representation to the next page. P (x axis coincident with C'2 axis) 2C3 (z) 3C'2 A'1 +1 +1 +1 +1 +1 +1 - x2+y2, z2 A'2 +1 +1 -1 +1 +1 -1 Rz - E' +2 -1 0 +2 -1 0 (x, y) (x2-y2, 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 (Rx, Ry) (xz, yz) E 2C3 (z) 3C'2 2S3 3 D3h 5 h h(xy) 3 quadrati c functions E D3h (xy) 2S3 linear functions, rotations v v 3. (continued) 2C3 (z) 3C'2 A'1 +1 +1 +1 +1 +1 +1 - x2+y2, z2 A'2 +1 +1 -1 +1 +1 -1 Rz - E' +2 -1 0 +2 -1 0 (x, y) (x2-y2, 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 (Rx, Ry) (xz, yz) E 2C3 (z) 3C'2 2S3 3 h h(xy) 3 quadrati c functions E D3h (xy) 2S3 linear functions, rotations v v D3h 5 Reduce this representation to a sum of irreducible representations of the point group. Do not forget the number of symmetry operators in each term. 4. Identify which possible atomic orbitals (s and the three p orbitals and five d orbitals) on P interact with the group orbitals with the symmetries that you found in problem # 3. 3 quadrati c functions 2C3 (z) 3C'2 A'1 +1 +1 +1 +1 +1 +1 - x2+y2, z2 A'2 +1 +1 -1 +1 +1 -1 Rz - h (xy) 2S3 linear functions, rotations E D3h v E' +2 -1 0 +2 -1 0 (x, y) (x2-y2, 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 (Rx, Ry) (xz, yz) E 2C3 (z) 3C'2 2S3 3 D3h 5 h(xy) v 5. The following two ligand orbitals can be used to form a π bonds to the central atomic orbitals on the P atom in PF5. P A B Orbital A is one of two orbitals that belong to the E’’ irreducible representation. Orbital B belongs to the A’’2 irreducible representation. 3 quadratic functions 2C3 (z) 3C'2 A'1 +1 +1 +1 +1 +1 +1 - x2+y2, z2 A'2 +1 +1 -1 +1 +1 -1 Rz - E' +2 -1 0 +2 -1 0 (x, y) (x2-y2, 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 (Rx, Ry) (xz, yz) h (xy) 2S3 linear functions, rotations E D3h v (a) Which d orbital on P does group orbital A interact with? Draw the bonding and antibonding combinations. Although theoretically possible, these orbitals are not important in bonding. (a) Which p orbital on P does group orbital B interact with? Draw the bonding and antibonding combination. Useful Data about ligands Weak field ligands - F-, Cl-, Br-, I-, H2O Strong Field Ligands- NH3, CN-, NO2-, en = (H2N-CH2-CH2-NH2 , bind through both N atoms) Structural Isomer types Ionization – Interchange of an anionic ligand bound to the central metal with in one in the crystal Hydration – Interchange of a water molecule bound to the central metal with another ligand in the crystal Coordination – Both cation and anoin are complex ions. The two metals interchange at least one ligand Linkage – A ligand is bound to the metal through different bonding modes Steroisomerl Isomer types Geometrical – The connectivity to ligand is the same, but the arrangement in space differs (For example cis and trans isomers) Optical – Isomers that are not superimmposable of their mirror image. 1. Draw the structures of the following compounds. Species outside the brackets are not bound to the central metal, but are in the crystal. (b) [Co(NH3)3Cl3](NO2)3 (a) [Co(NH3)6] [Cr(NO2)6] mer isomer (c) [Co(NH3)3(NO2)3] (Cl3) mer isomer (e) [Cr(NH3)6] [Co(NO2)6] (d) [Cr(NH3)3(H2O)3] (NO2)3 fac isomer (f) [Cr(NH3)3(H2O)3] (NO2)3 mer isomer (g) (a) [Cr(NH3)3(NO2) 3] ·3 (H2O) any isomer (f) Identify the types of isomers for the following pairs from (a)-(g). (a) and (e) ________________ (d) and (f)______________ (b) and (c) ________________ (d) and (g)______________ (f) aqnd (g) ________________ 2. 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: ______ _____ eg ______ ______ ________ t2g Determine the orbital occupancies for the following species, and the number of unpaired electrons Orbital occupancies ______ _____ (a) [Co(H2O)6]2+ ______ ______ ________ ______ _____ 3- (b) [Fe(CN)6] ______ ______ ________ ______ _____ 3+ (c) [Cr(NH3)6] ______ ______ ________ ______ _____ (d) [Co(en)3]3+ ______ ______ ________ ______ _____ (d) [Mn(CN)6]3______ ______ ________ # unpaired electrons? estimate µ (spi only) 3. (a) Briefly define or describe crystal (or ligand) field stabilization energy. (b) Calculate the crystal (or ligand) field stabilization energies for a d6 complex in terms of ∆o for both the low spin and high spin cases. (c) What is the deciding factor according to your calculation in (b) as to whether a complex will be high spin or low spin? (d) Why are there no low spin tetrahedral complexes. (the answers in (c) and (d) are related.)