IUPAC Nomenclature (A-46 to A-77, HW Ch. 11:1,2) (See Handout regarding the Essentials) Week 4-1
The cation is first, then the anion follows. [Co(NH3)6]Cl3
hexaammine cobalt(III) chloride (or cobaltic)
Remember that –ic is higher ox. state and –ous is lower ox. state. ferrous, ferric, cuprous, cupric K3[Fe(CN)6]
potassium hexacyano iron(III)
-o and -ate indicate anionic ligand and complex. Bromo-, iodo-, chloro(NH4)[Cr(NCS)4(NH3)2] ammonium diammoniumtetrakis(isothi diammoniumtetrakis(isothiocyanato)chromium(III) ocyanato)chromium(III) The order of the ligands is alphabetical (w/o prefix) use di, tri, etc. for first, second etc. anion but use but use bis, tris, etc if the anion is organic. This lessens the confusion on what part of the complex is ligand and what is part of the t he overall complex. cis-[PtCl2(PEt3)2]
cis-dichlorobis(triethyl cis-dichlorobis(triethyl phosphine) platinium (II)
the cis indicates the config. of the sq. planar complex.
[Co(en)3]2(SO4)3
tris(ethylenediamine)cobalt(III) tris(ethylenediamine)cobalt(III) sulfate
en is a common abbrev. of a common ligand. Et-ethyl, py-pyridine, Cp-cyclopentadienyl
Common ligands and their Abbreviations: Week 4-2
NO- nitrosyl
CO- carbonyl
en-
im-
ethylene diamine
imidazole HN
H2N
NH2
py-
pyridine
bipy-
bi-pyridine
N
N
phen-
1,10-phenanthroline
N
ox-
acac-
O
N
oxalate
O
O
O
O-
N
acetyl acetone
O
edta- ethylenediaminetetracetato HOOC
-
N
COOH N
HOOC
N
COOH
H
H H M
H H
Allyl bonds1
(eta)- sigma ligation Week 4-3
3
-pi ligation
5
-pi ligation
bis-(
5
-cyclopentadienyl)iron(II)
Hg bis-(
1
-cyclopentadienyl)mercury(II)
Bridging bonds- µ (mu) [(NH3)5Cr3+-OH-Cr3+(NH3)5]Cl5 -hydroxo-bis(pentamminechromium(III)) Bis(dithiooxalato-o-o’) nickelate(II)-bound thru oxygens -
S
S
O
O-
-
Ni(II)
O
O
S
S-
Pt(II)
Bis(dithiooxalato-S-S’)platinate(II)-bound thru sulfurs Na3[Al(C2O4)3]
sodium tris(oxalato) aluminate (III)
[Cr(NH3)2(H2O)3OH](NO3)2 diamminetriaquahydroxochromium(III) nitrate
VSEPR Theory (pgs. 203-218, HW Ch. 6; 1,2,9) Week 4-4
Only need to study Valence shell electron pair repulsion theory This is important because it helps us predict the shapes of simple molecules Bonds repulse other bonds but lone pairs repulse more.
The CH4 is 109.5 degrees. NH3 is 107 degrees. OH2 is 104.5 degrees.
How to calculate the number of lone pairs present? Week 4-5
Use Lewis dot theory. ICl4I Complex Charge 4-Cl4-bonds lone pair e
= = = = =
+7e- total +1 e +4e- for charge -8 e+4 e - so 2 lone pairs
Predict the shape of BrF 3, ICl4-, SF4, ICl2-, TeF5Lone pair next to 3-90º bonds versus next to 2-90º bonds.
Two lone pairs next to 6-90º bonds versus next to 4-90º bonds.
F F
Br F
F
Br
F F
Week 4-6
Double Bonds repulse more than single bonds
F 115 deg. F
F
S F
98 deg.
O 98 deg.
Explain these angle differences. Week 4-7
PF3,
PCl3,
PBr3,
PI3
97.8
100.3
101.5
102
Note: This can not be explained by halogen size because bond length increases as well as atom size. However the bond becomes more ionic with more electronegative atoms. Therefore, there is less electron density close to the phosphorus with PF3 so the lone pair and bonding orbitals come closer together.
Acid and Bases Chemistry: (Chapter 9, 344-355 pgs, HW 4,6,7,19,22) Week 4-8
Hard and Soft acid base theory Hard-hard interactions are more ionic in character. Soft-soft are more covalent in character, share electrons and pi-interactions.
See article J. Chem Ed 1968, 45, 581-643 for more information.
General trends: As element loses electrons it becomes harder Week 4-9
Ti+ Soft
Ti +2
Ti +3
Ti+4 hard
Hardness decreases as you go down a column (Li + versus Cs+) Question: Will this reaction proceed? CsI + Soft:soft
LiF Hard:hard
= LiI + CsF
The reation will not proceed due to hard/soft rules. WARNING!! Do not mix up strong/weak acids with hard/soft Ligands. Example: SO3-2 +
HF =
HSO3-
+
F-
Tricky reaction because F- is hard and SO 3-2 is softer so the hard H+ should stay with F-. However, F- is a weaker base than SO3-2 so the hard H+ goes onto the SO 3-2 due to acidity with a K eq = 104 Biological Relevance: Antibuse use soft/soft rules to become an aldehyde oxidase inhibitor. CH3CH2OH is converted to CH3CHO by alcohol dehydrogenase (ADH).
ADH is a Zn(II) enzyme that positions the alcohol for oxidation by NAD +
Week 4-10
Then CH3CHO is oxidized to CH3COOH by aldehyde oxidase. Aldehyde oxidase is a Mo(VI) enzyme that is reduced to Mo(IV) by the aldehyde. Disulfram (antibuse) is a soft ligand which binds to Mo(IV) thru the thiocarbonyls.
Et2N
S
S
S
NEt2 S
Mo(IV) The person gets sick because the aldehyde accumulates and this is what gives you a hangover. Toxic Metals: Many toxic metals such as Cd 2+, Hg2+, and Pb2+ are soft and bind to important cysteines amino acids in essential proteins.
Metallothionein (Mt) is a protein that is induced when a person is exposed to toxic metals. Mt has many cysteines which chelate Cd2+, Hg2+, and Pb2+ and make them harmless.
Sterics can affect strength of a ligand as well Week 4-11
For amines, large bulky groups change the hybridization from sp3 to sp2 and p orbitals.
The sp3 is more open to acids and thus is a stronger base. For example: Pyridine (sp 2) is a weaker base than aniline (sp 3) Proton sponge
pKb = 1.9 compared to 4.74 for NH 3 However, only pulls one proton, sterics hinder the diprotonation. Indeed in 98% H2SO4 only 50% is di-protonated. This is the end of material for Exam 1, Yeah!!
