Chem 416 Problem Set 1 Due Start of Class Wed Oct 3, 2012 – Open Books, Open Notes, Internet only
for Problem 6; 100 points total.
Problem 1 (10 points). Cyanate and fulminate are two anions with the same general formula [CNO]−.
There are three possible linear arrangements of these three atoms.
a) Draw the Lewis dot structure, complete with formal charges and any relevant resonance structures,
for the anion with the arrangement [CNO]−, rank the resonance structures in order of importance.
b) Repeat part a) for the anion with the arrangement [CON]−.
c) Repeat part a) for the anion with the arrangement [OCN]−.
d) Salts of cyanate are stable and commercially available (e.g. potassium cyanate). Fulminate salts are
known but they are unstable and therefore explosive. Salts of the third arrangement of atoms are
unknown. Based on the Lewis structure you drew in parts a) – c), which do you think is which? Explain.
e) Mercury fulminate was first prepared in 1800 and extremely explosive. Despite the ease of its
preparation, the crystal structure of this compound was obtained just recently in 2007. Using VSEPR
theory and your assignment of fulminate in part d, what geometry would you expect mercury(II)
fulminate to have? This compound was highlighted in the TV show, Breaking Bad – you can watch a clip
here: http://www.youtube.com/watch?v=sGN3SBVIjjA. Fun times with inorganic chemistry. Don’t try
this at home!
Problem 2 (16 points). For each of the following, divide the complex into a metal ion and ligands (with
each ligand having a closed shell (octet) configuration). In each case, give (i) the formal oxidation state
of the central metal and (ii) the number of d electrons on the metal in this oxidation state. For example:
Cu(H2O)62+ and CuCl42− both formally contain Cu2+, d9.
(b) Ni(H2O)62+
(d) Ir(CO)(Cl)(PPh3)2
(f) Hf(NMe2)4
(a) Cr(NH3)3Cl3
(c) Ru(py)62+
(e) Fe(CO)5
(g)
(h)
OH2
O
H2
N
O
H2
N
H2 N
Cu
N
H2
3+
NH2
Co
O
O
OH2
Ligand abbreviations: Me, methyl, CH3; py, pyridine, :
H2 N
N
H2
NH2
; Ph, phenyl, C6H5; :NH3 is ammonia; :PPh3 is
triphenylphosphine; CO is carbon monoxide, which binds through carbon, :C≡O.
Problem 3 (16 points). Assuming that each ligand counts as a two-electron donor to the metal center,
calculate the total number of electrons about the metal for each compound in problem 2. Taking CuCl42−
as an example, Cu2+ is d9 and each chloride ligand contributes two electrons, so the total electron count
is 9 + 4 × 2 = 17. Show your work.
Problem 4 (20 points). A) On-board storage of hydrogen is a major obstacle for the use of hydrogen as a
clean-burning transportation fuel. Ammonia-borane is an appealing candidate for chemical hydrogenstorage applications. Amine-borane adducts can be readily synthesized from free amines and boranes.
Thermal decomposition of ammonia-borane adducts yields hydrogen and a mixture of aminoborane and
borazine products. Give the point group for ALL of the reactants and products shown below except
polyborazylene (don’t forget H2!).
B) Using the equation below calculate the hydrogen capacity (wt%) of ammonia-borane. Be sure to show
how you arrived at your answer for full credit.
[cat]
X H3B-NH3 → 3X H2 + (BN)x
C) An alternative material for hydrogen storage is based on microporous metal-organic frameworks
(MOFs). Metal-organic frameworks consist of metal ions or clusters connected through organic bridging
ligands into extended one-, two-, or three-dimensional networks. The high surface area and porous
nature of these new materials make them particularly promising candidates for high capacity (wt%)
hydrogen storage materials. The crystal structures shown below are portions of metal organic
frameworks that have been used for hydrogen storage. Assign point groups to each of the crystal
structures and identify the number of different kinds of Mn atoms for each structure.
Problem 5 (28 points). A) In each of the following reactions, determine the oxidation state of all atoms
involved and show that the reaction is balanced with respect to oxidation states (sums of oxidation
states of reactants and products are the same). Indicate which atoms are the formal oxidants (accept
electrons) and reductants (provide electrons). Note: S in FeS2 is found as the [S2]2− anion.
PbO2 + Pb + 2 H2SO4 → 2 PbSO4 + 2 H2O
4 FeS2 + 11 O2 → 2 Fe2O3 + 8 SO2
B) Draw acceptable Lewis structures for all compounds in the following equations. Provide one
resonance structure that requires involvement of d orbitals at sulfur (clearly label it) and two resonance
structures that obey the octet rule. Include formal charge, electron count, and oxidation state for each
atom. Using VSEPR theory, predict the structures of these molecules. Indicate predicted bond angles (for
example: “ < 90° ” or “ > 45° ”) and discuss how you arrived at that prediction. Assign point groups for
the predicted geometries. For the reaction(s) involving an oxidation state change, indicate which atoms
are the formal oxidants and reductants.
SF6 + 3 H2O → SO3 + 6 HF
2 SF5Cl + H2 → S2F10 + 2 HCl
−
3[SOF3] + H2O → 2 [HF2]− + [SO2F]− + 2 SO2
SO2 + [N3]− → [N3SO2]−
Problem 6 (10 points). Download the article “Synthetic Approaches to (smif)2Ti (smif = 1,3-di-(2pyridyl)-2-azaallyl) Reveal Redox Non-Innocence and C-C Bond Formation” by B. A. Frazier, P. T.
Wolczanski, I. Keresztes, S. DeBeer, E. B. Lobkovsky, A. W. Pierpont, and T. R. Cundari Inorganic
Chemistry 2012, 51, 8177-8186. The reference format is Journal Name Publication Year, Volume, page
numbers. Inorganic Chemistry is typically abbreviated Inorg. Chem. The author(s) with the * are the
ones “to whom correspondence should be addressed,” typically the lead professors or group leaders.
The other authors are students or collaborators. This article is a short “communication,” which is
traditionally a preliminary report prior to a more complete (longer) “article.”
In the old days you would have to read a paper copy of this article in the library (the Natural Sciences
library in Suzallo/Allen), but now (almost) everything is online and many journals aren’t even producing
paper versions. The UW has purchased on-line subscriptions to many journals, including all of the
American Chemical Society (ACS) journals such as this one (your tuition $ and my grant overhead $ at
work). You can access ACS journals at http://pubs.acs.org/. You can also look up Inorg. Chem. in the
“Journals” section of the UW libraries catalog and find the “Full text” link, or you can just
Google/Bing/whatever Inorganic Chemistry. At the top of the search page, the “Citation” tab enables
you to select which ACS journal you want (Inorg. Chem. in this case) and enter the volume and starting
page number. You can also search the full text of the journals from this page. Once the citation is
shown, you can either select the paper in xml format, in pdf format with links, or in pdf format that
looks like a printed page.
The simplest way to do this is from a UW computer, otherwise the site won’t know that you are a
subscriber and you won’t be able to download the article. If you want to connect from a non-UW
computer, follow the instructions at: http://www.lib.washington.edu/help/connect.html.
(a) In one sentence, what are the main findings reported in this paper?
(b) What is a “redox noninnocent” ligand?
(c) Look at Figure 1, the results of an X-ray crystal structure. X-ray crystallography is the most important
form of structural characterization of pure solids; if you can grow a single crystal (with all the molecules
lined up in an ordered fashion), larger than about 0.03 mm on each side, this experiment can in most
cases give accurate positions and identities of all the atoms in the material (strictly speaking, the atoms
in the repeating unit in the crystalline solid, the ‘unit cell’). What is the oxidation state of the titanium in
this compound? What is antiferromagnetic coupling? Why is it relevant in assigning the oxidation state
of this molecule?
(d) Why do you suppose the authors use the abbreviation “smif” for their azaallyl ligand? This is extra
credit 
Note the sentence: “While a ‘back of the envelope’ depiction of a Ti(III) d1 complex would surely be
(dxy)1, the covalency in the complex reveals the metal d-character to be smeared between dxy and dxz;
the other electron is localized on the smif, rendering it a dianion.” This will show up again in a few
weeks. Keep it in the back of your mind!