INORGANIC CHEMISTRY 413/571 FINAL EXAMINATION 12/17/93. DR. J. SHERIDAN Write all answers in the answer book. WRITE NEATLY. This will help me to understand your answers and maybe get you a few more points! Show all work where appropriate and give detailed explanations for full credit. TOTAL POSSIBLE SCORE = 200 points. Section 1. Main Group Chemistry Multiple Choice. Choose the best answer. (2 points each) 1. Chemically, a sapphire is a) KAl(SO 4 ) 2 12H 2 O. b) aluminum chloride that contains trace amounts of BeCl 2. c) aluminum oxide that contains some transition metal ions. d) NaAl(OH) 4. 2. Which halide ion is most readily polarized? a) F - b) I - c) Cl - d) Br - 3. Except for fluorine, the halogens show four positive oxidation numbers. What are those oxidation numbers? a) +1, +3, +4, +6 b) +1, +3, +5, +6 c) +3, +4, +5, +6 d) +1, +3, +5, +7 4. When the equation is balanced for the preparation of antimony pentafluoride from fluorine and the metal, what is the sum of the coefficients in the balanced equation? a) 10 b) 8 c) 7 d) 9 5. When forming interhalogen compounds, what determines which halogen will be the central atom? a) The smaller of the two halogens is the central atom. b) The halogen with the higher first ionization energy is the central atom. c) The less electronegative of the two halogens is the central atom. d) The halogen with the higher standard reduction potential is the central atom.
6. How many phosphorus atoms are present in the white phosphorus molecule? a) 6 b) 4 c) 2 d) 8 7. Phosphine, PH 3, is the phosphorus analog of ammonia, but it is a much weaker base. The K b of PH 3 is about 10-26 while the K b of NH 3 is 10-5. What does this suggest about the occurrence of phosphonium (PH 4 + ) salts? a) The weak base means that PH 4 + ions are common and therefore many salts are known. b) The occurrence of PH 4 + ions is not related to the base constant K b. c) Such salts should be rare since there is little tendency for phosphine to form PH 4 + ions. d) Phosphonium salts are very stable. 8. How many acidic hydrogens does phosphorous acid, H 3 PO 3 have? a) 1 b) 2 c) 3 9. What are the products of the "water gas" reaction? a) CO 2 and H 2 O b) CO 2 and H 2 c) C and H 2 d) CO and H 2 10. Although silicon dioxide has the empirical formula SiO 2, it is a network solid that is based on interconnecting a) cubes. b) hexagons. c) tetrahedra. d) octahedra. Section 2. Symmetry and M.O. Theory 11. (a) Draw a molecular orbital diagram for bis(benzene)chromium (0). (4 points) (b) Indicate carefully which ligand group orbitals interact with the metal atomic orbitals by means of two or three simple orbital drawings. (6 points) (c) Explain why the benzene ligands in [(η-c 6 H 6 ) 2 Cr] are referred to as π donor ligands. (4 points) (d) Give two other examples of π donor ligands and one example of a complex containing each of these ligands. (6 points)
12. Determine the point group symmetry of the following. Show all work, guesses will receive NO CREDIT! (5 points each) (a) Ferrocene (staggered) Fe (b) Fe (c) (d) Cl (e) Dichloroallene (f) Borazine (planar) H H H H H C C C N N Cl Cl H N H H Section 3. Organometallic Chemistry. 13.Give the oxidation state of the metal, the d n electron configuration, and number of valence electrons in the following compounds.(3 points each) (a) Na[Re(CO) 5 ] (b) bromodihydrido(methylisocyanide)bis(triphenylphosphite)rhodium (III) (c) [(η-c 5 H 5 )Mn(CO) 3 ] (d) [Co(η-C 5 H 5 ) 2 ] (e) [V(η-C 5 5 )Cl 4 ] 14. Draw a simple diagram to show how a NO ligand bonds to a transition metal center. (5 points)
15. A transition metal carbonyl complex A reacts with Br 2 to give B. In turn complex B was reacted with toluene in the presence of AlCl 3 as catalyst to form a stable cationic complex C. Complex A also reacted with 2 equivalents of Na to form an anionic species D. D reacts with water to give E. Given the data below identify compounds A through E. (20 points) A Formula weight 652.4. IR shows terminal CO ligands only. B IR shows complex contains 5 terminal CO ligands. C IR shows terminal CO's. 1 H NMR shows 5H signal typical of a π-bonded arene and a 3H singlet for a methyl group. D IR shows terminal CO's but at lower wavenumbers than A. E IR shows terminal CO's at higher wavenumber than D. 1 H NMR indicates 1H signal at -9 p.p.m. relative to tetramethylsilane. Formula weight from Mass Spectrum = 327. 16. For each of the following metal ligand combinations, formulate the simplest neutral compound that conforms to the 18-electron rule. Draw a reasonable structure for each compound.(2 points each) (a) Ni, CO. (b) Fe, CO, COT = cyclooctatetraene. (c) Co, CO, Cp = cyclopentadienyl. (d) Cp, Co, NO. (e) Mn, CO, H. Section 4. chanism and Reactions in Inorganic Chemistry. 17. Why is the rate of attack by Y on Co(III) complexes independent of Y, except when Y is OH -. (5 points) Suggest a complex of Co(III) that would not show any relationship between hydroxide concentration and rate of substitution. (5 points) 18. Predict the products of the following reactions, (3 points each) (i) [Pt(PR 3 ) 4 ] 2+ + 2Cl -. (ii) [PtCl 4 ] 2- + 2PR 3. (iii) [Mo(CO) 6 ] + 3CH 3 CN 19. Which of the following are INERT and which are LABILE? Give reasons for your choice. (a) [Mo(CO) 6 ] (b) [Mn(H 2 O) 6 ] 2+ (c) [V(H 2 O) 6 ] 3+ (d) [Mn(CN) 6 ] 4- (e) [Cr(NH 3 ) 6 ] 3+ (2 points each)
Section 5. General Inorganic Chemistry 20. Draw the following Inorganic compounds. Show stereochemistry where appropriate. A 3D structure is necessary for full credit. (3 points each) (a) Sodium tetrachloronickelate(ii). (b) mer-trihydridotris(triphenylphosphine)iridium(iii). (c) TeCl 4. (d) Bis[dicarbonyl(η-cyclopentadienyl)iron(I)]. (e) Sodium tetrabromoargentate(iii). 21. Determine which of the following boranes are closo-, nido-, or arachno structures. (3 points each) (a) [B 5 H 5 ] 2- (b) B 5 H 11 (c) [B 6 H 6 ] 2- (d) C 2 B 4 H 6 22. How many isomers are there of C 2 B 10 H 12. (4 points) 23. Draw how you would expect the d orbitals of a transition metal ion to be split in the following ligand fields.label the orbitals. (4 points each) For example:- Octahedral would be as shown below. (a) Tetrahedral. (c) Tetragonal (z in) (b) Square Planar (c) Tetragonal (z out) 24. Why are second and third row transition metal complexes always low spin? (4 points)