1. (10pts)Two partial molecular orbital diagrams (A&B) are shown- one is for [Co(F)6]3-
and the other for [Co(PH3)3]3+.
Assign a compound to each diagram.
Do is labeled on each one- what accounts for the difference in energies for the two?
2. (5) NH3, NF3, N(CH3)3, etc. are all trigonal pyramidal, sp3 hybridized compounds.
Phosphines are often much closer to trigonal planar, sp2 hybridization. What
structural AND electronic reasons can you give for this difference in bonding and
3. (5) Phosphines, PR3, can act as weak p acids when coordinated to a transition
metal, whereas alkylamines, NR3, never act as p acids. What can explain this
difference in reactivity? (to clarify- an acid, like H+ is an acid, is an e- acceptor)
4. (15pts) The spectra of [Ti(H2O)6]3+ and [Fe(H2O)6]2+ are shown below.
Both are octahedral complexes.
a) Draw the d-orbital splitting diagram for Oh symmetry. You only need to consider
the d manifold.
b) How many unpaired electrons does each complex have?
c) What is the crystal field stabilization energy in units of 10Dq (or D) for each?
Given that 960 nm is equivalent to 10,550 cm-1 and 525 nm ~ 19,280 cm-1
d) What is the energy of a d-d transition in kJ/mol for one or the other complex, you
may also need E=ln, E=hn or E=hc/l.
e) Calculate the spin-only contribution to the magnetic moment in Bohr Magnetons
(BH) for both complexes.
5. (5pts) Which of the following complexes has most likely not a low-spin electron
a) [Os(H2O)6]2+ b) [Co(H2O)4Cl2] c) [RhCl6]3– d) [Mn(CN)6]4–
6. (5pts) Which of the following complexes do you expect to have the greatest ligand
field stabilization energy?
a) [CoBr4]2– b) [MnCl6]4- c) [ReCl6]4– d) [CdBr6]4–
7. (5pts) For which of the following complexes do you expect Δoct to be the greatest?
a) [Ir(CN)6]4– b) [Rh(CN)6]4– c) [Rh(CN)6]3– d) [Ir(CN)6]3
(the spectrochemical series is: I− < Br− < S2− < SCN− < Cl− < NO3− < N3− < F− < OH− <
C2O42− ≈ H2O < NCS− < CH3CN < NH3 < en (ethylenediamine) < phen < NO2− <
PPh3 < CN− ≈ CO). You might also want to look up the nephelauxetic series.)
8. (12 pts) Which of the following electronic transitions will be more intense?
a) 3A2g à 3T2g in [NiCl6]4- or 3T1 à 3T2 in [NiCl4]2-
b) 3A2 à 1E in [Ni(en)3]2+ or 3A2 à 3A2 in [Ni(en)3]2+
c) The most intense d-d band in [CoCl4]2- or in [MnCl4]2-
d) 1A1gà 1T2g in [Co(NH3)6]3+ or 1A1 à 1T2 in [Co(en)3]2+