Download Nomenclature of metal complexes

CHM 511 Special Topics: Nomenclature
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Nomenclature of metal complexes
What is a complex?
Complex: a metal atom surrounded by ligands
Ligand: an ion or molecule that can have an independent existence
Coordination compound: a neutral complex or an ionic compound in which at least one of the
ions is a complex
Complex
Ligand
CC?
CC possibility?
Ag(NH3)2+
AgCl2Fe(H2O)63+
Ni(CO)4
With complexes, we can discuss the inner coordination sphere versus the outer coordination sphere.
EX. FeCl3∙6H2O
EX. CoCl2∙6H2O
From Shriver and Atkins, Inorganic Chemistry, 4th edition
CHM 511 Special Topics: Nomenclature
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Extra notes:
1. acac is acetylacetonate
2. NH3 = ammine
3. CN-, attaches through C (usually)
4. NCO-, N attachment is the isocyanato ligand
5. SCN-, S attachment is the thiocyanato ligand
6. SCN-, N attachment is the isothiocyanato ligand
7. NO2-, nitro if N attachment
8. NO2-, nitrito if O attachment
IUPAC suggestion
Disclaimer on nomenclature rules: There are at least two systems (IUPAC and everyone else)
and though there is general agreement on the “big” issues, sometimes the details are slightly
different. I am presenting the most common system seen by ACS journals.
1. Writing formulas: write cation, then anion (just like simple salts)
2. The inner coordination sphere is enclosed in [ ]. Within the coordination sphere the ligands are
named before the metal, but the metal ion is written first in a formula, followed by anionic
ligands, followed by neutral or cationic ligands. Ligands are sometimes written to point out their
attachment sites.
3. The number of ligands is indicated with Greek prefixes. If the ligand name includes a Greek
prefix or is complicated, it is set off with parentheses and the second set of prefixes is used.
1. mono
6. hexa......hexakis
2. di.......bis
7. hepta.....heptakis
3. tri.......tris
8. octa......octakis
4. tetra.....tetrakis
9. nona.....nonakis
5. penta......pentakis
10. deca......decakis
EX. [X(NH3)2]n+ versus [X(CH3NH2)2]n+
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4. Ligand endings:
Anionic ligands are given an "o" suffix
Neutral or cationic ligands retain their name
Coordinated water is "aqua" (not aquo!)
EX. Name the following ligands
Cl-
H2O
Br-
CH3NH2
SO42-
NH3
C2O42-
CO
5. Write ligand names alphabetically (ignoring Greek prefixes), with no spaces between parts of
names. Avoid abbreviations in the name.
EX. [Cu(NH3)4]2+
[Cu(NH3)4]SO4
[Co(NH3)6]Cl3
[CoCl2(NH3)4]+
a complex with ethylenediamine (en), [CoCl2(NH2CH2CH2NH2)2]+
a complex with 2,2’-bipyridine (bipy), [Fe(C5H4N-C5H4N)3]2+
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6. Two ways to designate charge or oxidation number
(a) Stock system: use a Roman numeral in parentheses to indicate the oxidation # of metal
(b) Ewens-Bassett system:1 use an Arabic numeral in parentheses (with a + or -) indicating the
overall charge of a complex. Numbers are written as (2+), (3-), (1+), etc.
Here’s a statement from Inorganic Chemical Nomenclature by B.P. Block, W. H. Powell, and
W. C. Fernelius (ACS Reference book, 1990), pg 40-41, “The use in the Stock system of 0 for an
oxidation number of zero (because there is no Roman numeral for zero) precludes the use of 0 as
a Ewens-Basset number for neutral coordination entities. Normally this causes no confusion.”
So...? If a complex has no overall charge, don’t use the EB system!
In either case, if the complex is negative, add "-ate" to the name of the coordination sphere.
EX. [Pt(NH3)4]2+
[PtCl4]2[PtCl6]2[Re2Cl8]27. cis- and trans- prefixes designate adjacent or opposite geometric locations
EX. [PtCl2(NH3)2]
[CoCl2(NH3)4]+
1
This footnote comes from a journal article (Kauffman, G. B.; Jørgensen, C. K.; J. Chem. Ed. 1985, 62, 474-476.) probing the
history of the E-B system. “Ronald Victor George Ewens was born in 1913, was educated at Queen Elizabeth's Hospital, Bristol,
and received his doctorate in 1938 from Lincoln College, Oxford University as a pupil of Nevil Vincent Sidgwick. After a year's
investigation of the inhibition of fermentation and glycolysis by snake venom at the Sir William Dunn School of Pathology,
Oxford, he became Demonstrator and later (1948) Reader in chemistry at Guy's Hospital Medical School. His primary research
interest was metal carbonyls and nitrosyls. As Bassett told Fernelius, the 35-year-old Ewens committed suicide by throwing
himself in front of a subway train on September 21, 1948, in the year preceding the publication of the paper. He left behind a
widow and a young daughter.
Henry Bassett (1881-1965). PhD. Munich; DSc, London; was Assistant Lecturer, Liverpool University; Professor and Head of
the Department of Chemistry, University College, Reading and Reading University; and Emeritus Fellow, University College,
London. He was primarily interested in double salts and solid ammoniates and was the author of "Theory of Qualitative
Analysis" and "Chemical Laboratory for Beginners".”
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8. fac- and mer- prefixes used for MX3Y3 octahedral complexes
EX. [Co(NO2)3(NH3)3]
9. Bridging ligands between two metal centers have the prefix
EX. [(NH3)5Cr-O-Cr(NH3)5]4+
EX. [(NH3)4Co(-OH-)2Co(NH3)4]4+
EX. [(NH3)4Co(-NH2-)(-OH-)Co(NH3)4]4+
What is the formula of tri-μ-iodo-bis(tricarbonylrhenium)?
(mu)
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10. When the complex is negatively charged, a Latin name for the element is often used, but not
always (see highlighted section). Otherwise, use this list.
iron
silver
antimony
lead
tin
gold
copper
tungsten
ferrate
argentate
stibate
plumbate
stannate
aurate
cuprate
tungstate
EX. K3[Fe(CN)6]
mercury
scandium
titanium
chromium
manganese
cobalt
nickel
zirconium
mercurate
scandate
titanate
chromate
manganate
cobaltate
nickelate
zirconate
niobium
ruthenium
rhodium
palladium
rhenium
molybdenum
tantalum
platinum
niobate
ruthenate
rhodate
palladate
rhenate
molybdate
tantalate
platinate
EX. Na[AgCl2]
Chelating ligands
Chelate: a complex in which a polydentate ligand forms a ring that includes the metal atom
EX. [Co(ox)(OH2)4]+
This can sometimes lead to strain and can distort an octahedral complex. Measure the ligand's
"bite angle".
Other polydentate ligands you recall (perhaps from CHEM 321?)
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Chirality
A chiral complex is not superimposable on its own mirror image.
Two mirror images = enantiomeric pair
How to determine if something is achiral:
look for a mirror plane
look for a center of inversion
EX. trans-[FeCl2(OH2)4]
[Cr(edta)]-
trans-[CoCl(en)2(OH2)]2+
[Ru(bipy)3]2+
cis-[CoCl2(en)2]+
[PtCl(dien)]+
(dien = diethylenetriamine)
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Designations of chiral Oh complexes
Instead of R and S designations, use and (delta and lambda)
Original designation viewed rotation through a 3-fold axis, but see article attached for easier
method.
See article from Journal of Chemical Education 72(12) 1995, 1065-1066.
EX. [Co(en)]3+ can occur with two non-superimposable mirror images