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2006 Sevagram Enterprises

NOMENCLATURE IV

This supplement deals with complexes. In general, a complex is recognizable because square brackets

[ ] enclose the formula. The square brackets are omitted when the actual structure of the complex is

uncertain.

A complex is composed of a central atom, normally a metal, surrounded by atoms or groups of atoms

called ligands. Below is one way of illustrating the formation of a complex:

Ni2+

+ 6 H2O[Ni(H2O)6]2+

In this reaction, the metal behaves as a Lewis acid and accepts a pair of electrons from the Lewis base(ligand). In this case, the ligand is water with the oxygen atom donating one of its lone pairs to the

nickel. The oxygen atom is the donor atom. In this complex, there are six total donor atoms.

A complex may be ionic or neutral. An ionic complex is a complex ion. A neutral complex is a type

of coordination compound. The only difference in naming coordination compounds or complex ionsis that anionic complex ions have an -ate suffix.

A coordination compound may contain more than one complex ion or material that is not part of the

complex. A coordination compound must have an overall neutral charge. Examples of coordination

compounds are: [Pt(NH3)2Cl2], K2[Mn(C2O4)3], and [Ni(H2O)6]SO4.

When writing formulas the metal (central atom) is always first within the brackets. However, when

writing names the metal name is always last. Name any material not listed within the bracketsseparately.

Examples:

[Ru(NH3)5(N2)]Cl2 Coordination compound

[Ru(NH3)5(N2)]2+

Complex ion (cationic)[PtNH3Cl2(C5H5N)] Coordination compound

[IF6]- Complex ion (anionic) (the name must end in -ate)

K[IF6] Coordination compound (same -ate ending)

If everything in the formula is within one set of bracket, the entire name will be one word. If there is

material outside the brackets, this outside material has a separate name.

As with simpler compounds, cation names are always before anion names. Thus a cationic complex

would be the first word in the name, and an anionic complex would be the last word in a name (with

an -ate ending).

Examples:

[Ni(H2O)4Cl2] tetraaquadichloronickel(II)[Co(NH3)6]Cl3 hexaamminecobalt(III) chloride

K2[PtCl4] potassium tetrachloroplatinate(II)

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When writing the name a complex, or when writing the formula for a complex, list the ligands

alphabetically. Again, do not forget metals are first in the formula and last in the name.

Names of anionic ligands always end in an -o. Neutral ligands are unchanged. Two common

exceptions in the case of neutral ligands are NH3= ammine (note the double m), and H2O = aqua.

Other common ligands and their names are in the following list:

Those with more than one donor atom may be chelating.

Ligand Formula Ligand Name Donor atoms

(or abbreviation)

Azide ion N3- azido 1

Bromide ion Br- bromo 1

Carbonate ion CO32-

carbonato 1

Chloride ion Cl- chloro 1

Cyanide ion CN- cyano 1

Ethylenediaminetetraacetate EDTA

4-

ethylenediaminetetraacetato 6Fluoride ion F- fluoro 1

Hydride ion H- hydrido 1

Hydrogen sulfide ion HS- mercapto 1

Hydroxide ion OH- hydroxo 1

Iodide ion I- iodo 1

Nitrite ion NO2- nitrito 1*

Oxalate ion C2O42-

oxalato 2

Oxide ion O2-

oxo 1Peroxide ion O2

2- peroxo 1

Sulfide ion S2-

thio 1Thiocyanate ion SCN

- thiocyanato 1*

Ammonia NH3 ammine 1

Bipyridine bipy bipyridine 2Carbon monoxide CO carbonyl 1

Dinitrogen N2 dinitrogen 1

Dioxygen O2 dioxygen 1

Ethylenediamine en ethylenediamine 2Nitric oxide NO nitrosyl 1

ortho-phenanthroline o-phen ortho-phenanthroline 2

Phosphine PH3 phosphine 1Pyridine C5H5N or py pyridine 1

Water H2O aqua 1

* May form linkage isomers.

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Multiple identical ligands have prefixes added to designate the number of such ligands:

2 di- 5 penta- 8 octa-

3 tri- 6 hexa- 9 nona-

4 tetra- 7 hepta- 10 deca-Examples:

[Co(NH3)6]Cl3 Hexamminecobalt(III) chloride[Cr(NO)4] Tetranitrosylchromium(0)

If the ligand name contains a prefix or begins with a vowel (except ammine and aqua), alternateprefixes are necessary:

2 bis- 5 pentakis- 8 octakis-3 tris- 6 hexakis- 9 nonakis-

4 tetrakis- 7 heptakis- 10 decakis-

When using the alternate prefixes, it is common practice to enclose the name of the ligand withinparentheses. Add either type of prefix after the ligands have been alphabetized.

Examples:

[Cr(en)3]Cl3 Tris(ethylenediamine)chromium(III) chloride

K2[Ge(C2O4)3] Potassium tris(oxalato)germanate

Anionic complexes always have names ending in -ate. This will require a change in the name of themetal. Thus, aluminum would become aluminate, and zinc would become zincate. The only

exceptions to this are some of the metals whose symbols are from Latin or Greek names. These

exceptions are:

Metal (Greek

or Latin Name) Symbol Anionic Name

Copper (Cuprum) Cu cuprate

Silver (Argentum) Ag argentate

Gold (Aurum) Au aurateIron (Ferrum) Fe ferrate

Tin (Stannum) Sn stannate

Lead (Plumbum) Pb plumbate

Examples:

K[Au(CN)4] Potassium tetracyanoaurate(III)

(NH4)2[PbCl6] Ammonium hexachloroplumbate(IV)

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If the metal ion may exist in more than one oxidation state, it is necessary to list this oxidation state, in

Roman numerals, immediately after the name of the metal ion. Enclose the Roman numeral inparentheses and considered the Roman numeral and parentheses part of the same word, and not a

separate grouping. If the metal only occurs in one oxidation state, no such indicator is used. The use

of Roman numerals is the Stock system.

In many cases, complexes may occur as isomers. Isomers are compounds with the same composition,

but different structures. The difference in the structures causes differences in their properties.

Coordination isomers involve placing different ligands within the coordination sphere. Linkageisomers are those with ligands such as the nitrite ion, which may change donor atoms. Different

optical isomers affect light differently. Geometric isomers involve different positions of the bonded

ligands. In most cases, only minor changes are present in the nomenclatures of the different isomers.

There are no new rules for coordination isomers. The new ligands in the coordination sphere about the

central atom simply replace the original ligands in the name.

Linkage isomers require some indication of the donor atom. Some ligands may use different donoratoms. Two common examples are the nitrite ion and the thiocyanate ion. Either the nitrogen or one

of the oxygen atoms may serve as the donor atom from the nitrite ion. In the formula, if the nitrogenis the donor, it appears as -NO2, and if one of the oxygens is the donor, it appears as -ONO. In a

similar manner the thiocyanate ion may donate through the sulfur (-SCN) or the nitrogen (-NCS). At

one time the different means of donating electrons were indicated by different names (-NO2= nitro; -ONO = nitrito; -SCN = thiocyanato; and -NCS = isothiocyanato), now the preferred method is to

include the donor atom in the name to give -NO2= nitrito-N; -ONO = nitrito-O; -SCN = thiocyanato-

S; and -NCS = thiocyanato-N.

Examples:

[Zn(NCS)4]2+ Tetrathiocyanato-N-zinc ion

[Cd(SCN)4]2+

Tetrathiocyanato-S-cadmium ion

There will be no discussion of optical isomers in this discussion other than to say that various letters

before the name of the complex indicate that it is an optical isomer.

The two basic types of geometric isomers are cis/trans and fac/mer pairs. Cis/trans isomers may occur

in square planar or octahedral complexes. In the cis isomer, identical ligands are adjacent to each

other, while in the trans isomers they are on opposite sides. The designation cis- or trans- precedes thename of the complex. Octahedral complexes may also occur in fac/mer pairs. Fac is an abbreviation

for facial, which is the isomer where three identical ligands occupy the corners of a face of the

octahedron. Mer is short for meridinal, which is the isomer where three identical ligands are not onthe corners of a face of the octahedron. As with cis/trans isomers, the terms fac- or mer- precedes the

name of the complex.

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Name or give the formula for each of the following: (Answers on the next page)

a. Dichlorobis(ortho-phenanthroline)iron(III) perchlorate ________________________

b. Dibromobis(ethylenediamine)platinum(IV) bromide___________________________

c. Bis(ethylenediamine)zinc tetraiodomercurate(II) _____________________________

d. Hexaamminenickel(II) tris(oxalato)chromate(III) _____________________________

e. Hexaamminechromium(III) nitrate _____________________________

f. Pentaaquabromomanganese(III) sulfate _____________________________

g. Potassium diaquatetrabromovanadate(III) _____________________________

h. Sodium tetrabromo(ethylenediamine)cobaltate(II) _____________________________

i. Tetraamminecarbonatocobalt(III) sulfate _____________________________

j. Tris(bipyridine)ruthenium(II) nitrate _____________________________

a. [AlCl4]- _______________________________________________

b. [Ag(CN)2]- _______________________________________________

c. cis-[Co(en)2(NO2)2]+ _______________________________________________

d. [Co(NH3)2Br2(en)]Cl _______________________________________________

e. trans-[Cr(NH3)4(H2O)2]3+

_______________________________________________

f. K3[Fe(C2O4)3] _______________________________________________

g. K3[IrCl5(S2O3)] _______________________________________________

h. [Pd(en)2][Cr(NH3)2Br4]2 _______________________________________________

i. [PtCl4(en)] _______________________________________________

j. trans-[Pt(NH3)2(Br)H] _______________________________________________

k. [Ru(H2O)Cl5]2-

_______________________________________________

l. [Zn(NH3)4]2+

_______________________________________________

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Answers to the nomenclature problem from the preceding page.

a. Dichlorobis(ortho-phenanthroline)iron(III) perchlorate [FeCl2(o-phen)2]ClO4

b. Dibromobis(ethylenediamine)platinum(IV) bromide [PtBr2(en)2]Br2

c. Bis(ethylenediamine)zinc tetraiodomercurate(II) [Zn(en)2][HgI4]

d. Hexaamminenickel(II) tris(oxalato)chromate(III) [Ni(NH3)6]3[Cr(C2O4)3]2

e. Hexaamminechromium(III) nitrate [Cr(NH3)6](NO3)3

f. Pentaaquabromomanganese(III) sulfate [Mn(H2O)5Br]SO4

g. Potassium diaquatetrabromovanadate(III) K[V(H2O)2Br4]

h. Sodium tetrabromo(ethylenediamine)cobaltate(II) Na2[CoBr4en]

i. Tetraamminecarbonatocobalt(III) sulfate [Co(NH3)4CO3]2SO4

j. Tris(bipyridine)ruthenium(II) nitrate [Ru(bipy)3](NO3)2

a. [AlCl4]- Tetrachloroaluminate ion

b. [Ag(CN)2]- Dicyanoargentate(I) ion

c. cis-[Co(en)2(NO2)2]+ cis-bis(ethylenediamine)dinitrito-N-cobalt(III) ion

d. [Co(NH3)2Br2(en)]Cl Diamminedibromoethylenediaminecobalt(III) chloride

e. trans-[Cr(NH3)4(H2O)2]3+

trans-tetraamminediaquachromium(III) ion

f. K3[Fe(C2O4)3] Potassium trisoxalatoferrate(III)

g. K3[IrCl5(S2O3)] Potassium pentachlorothiosulfatoiridate(IV)

h.[Pd(en)2][Cr(NH3)2Br4]2 Bis(ethylenediamine)palladium(II)diamminetretrabromochromate(III)

i. [PtCl4(en)] Tetrachloroethylenediamineplatinum(IV)

j. trans-[Pt(NH3)2(Br)H] trans-diamminebromohydridoplatinum(II)

k. [Ru(H2O)Cl5]2-

Aquapentachlororuthanate(III) ion

l. [Zn(NH3)4]2+

Tetraamminezinc ion

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PRACTICE SET IV-1

Name the following:

1. K3[Fe(CN)5(NO)] _______________________________________________

2. [CoCl(en)2(NO2)]Cl _______________________________________________

3. Na3[Al(C2O4)3] _______________________________________________

4. cis-[Pt(NH3)2Br2] _______________________________________________

5. [Ag(NH3)3]+ _______________________________________________

6. [Hg(CN)4]2-

_______________________________________________

7. Ba[BrF4]2 _______________________________________________

8. [Zn(OH)4]2-

_______________________________________________

9. Rb[Cr(CO)2(NCS)4] _______________________________________________

10. trans-[Pd(NH3)2Cl2] _______________________________________________

11. cis-[Mo(NH3)2Cl4] _______________________________________________

12. [NiNH3(Cl2)(C5H5N)] _______________________________________________

13. [CuCl4]2- _______________________________________________

14. [Mn(bipy)(en)2]3+

_______________________________________________

15. [V(CO3)3]3-

_______________________________________________

16. [SnI6]2-

_______________________________________________

17. [Cd(H2O)4]2+

_______________________________________________

18. [Hg(N3)4]2-

_______________________________________________

19. [Ru(NH3)5(N2)]2+

_______________________________________________

20. [Re(H)4(PH3)4]+ _______________________________________________

Re = Rhenium

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PRACTICE SET IV-2

Write formulas for each of the following:

1. cis-diamminetriaquahydroxochromium(III) nitrate_____________________________

2. Ammonium diphosphinetetrathiocyanato-S-chromate(III)_______________________

3. Chloronitrito-O-bis(ortho-phenanthroline)cobalt(III) ion________________________

4. Sodium dithiosulfatoargentate(I) _____________________________

5. Tetrapyridineplatinum(II) tetrachloroplatinate(II) _____________________________

6. Tetraiodonickelate(II) ion _____________________________

7. Ammonium hexachloroferrate(III) _____________________________

8. Pentacarbonyliodomanganese(I) _____________________________

9. Sodium hexachlorophosphate(V) _____________________________

10. Lithium tetrahydridoaluminate _____________________________

11. Pentammine(dinitrogen)ruthenium(II) chloride _____________________________

12. Carbonyldinitrosylnickel(0) _____________________________

13. Potassium hexacyanoferrate(II) _____________________________

14. Dichlorobis(ethylenediamine)cobalt(III) ion _____________________________

15. Tris(bipyridine)iron(II) ion _____________________________

16. Pentabromocuprate(II) ion _____________________________

17. Sodium pentafluorodioxouranate(VI) _____________________________

18. Ammonium nonahydridorhenate(VII) _____________________________

19. Pentamminethiocyanato-N-cobalt(III) chloride _____________________________

20. Potassium amminedicyanodioxoperoxochromate(VI)_____________________________

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