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PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN

©2014 W. H. FREEMAN D COMPANY

Inorganic Chemistry Sixth Edition

Chapter 7- An

Introduction toCoordination Compounds

PART A

INORGANIC CHEMISTRY 6E| SHRIVER| WELLER| OVERTON | ROURKE | ARMSTRONG©2014 W. H. FREEMAN AND COMPANY

Modified By Dr. Cheng-Yu Lai

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Transition Metal Complexes Structures-A

The structures, nomenclature and isomers of coordination compounds

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Introduction to Coordination Compounds

Any compound containing a metal atom or ion

with one or more ligands is called a coordination

compound or complex. The ligands donate

electrons to the metal via coordinate covalent

bonds.

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The structures of these compounds was

not always evident. Ions or molecules might

be directly bonded to the metal, or serve as a

counter ion for an ionic salt.

[Mn(OH2)6] SO4 sulfate ion is outer sphere

[Mn(OH2)5 SO4].H2O sulfate ion is inner sphere


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The coordination number is the number of donor atoms bonded tothe central metal atom/ion.


Some Coordination Complexes

example molecularformula

Lewisbase/ligand

Lewis acid donor atom coordinationnumber

[Ag(NH3)2]+ NH3 Ag

+ N 2

[Zn(CN)4]2- CN- Zn2+ C 4

[Ni(CN)4]2- CN- Ni2+ C 4

[PtCl6]2- Cl- Pt4+ Cl 6

[Ni(NH3)6]2+ NH3 Ni

2+ N 6

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Name of Common Ligands

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Nomenclature of Coordination Compounds

There is a separate system for naming

coordination compounds:

prefix indicating + ligand name + metal + (oxidation #

# of ligands in romannumerals)

or

“ “ “ + “ “ “ + “ “ “ + (charge of complex)

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1. If ionic, the positive ion is named first, then

the negative ion.

2. The inner coordination sphere is indicated by

square brackets. In the formula, the metal is

written first, followed by the ligands. In

naming, the ligands are named first, then the

metal.

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3. Prefixes: If the ligand itself contains a prefix in its

name (ex. dimethyl amine), then the prefix to indicate

the number of ligands changes, and the ligand name is

placed in parenthesis.

2 di or bis 5 penta or pentakis 8 octa or octakis

3 tri or tris 6 hexa or hexakis 9 nona or nonakis4 tetra or tetrakis7 hepta or heptakis 10 deca or decakis

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4. Ligands are listed in alphabetical order (ignoring anyprefixes). Most ligands have special names, with all

negatively charged ligands ending in the letter “o”.

Most neutral ligands retain their usual names, with

the following common exceptions:NH3 ammine H2O aqua CO carbonyl

5. Ligands that bridge two metal centres are denoted by a

prefix μ (mu) added to the name of the relevant ligand

μ-oxido-bis(pentamminecobalt(III))

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5. There are two systems for indicating the oxidation

number of the metal. The more commonly used system

indicates the oxidation number in Roman numerals in

parentheses after the name of the metal.The other system puts the charge of the coordination

complex in Arabic numbers in parentheses after the

metal.

[Cr(H2O)5Cl]2+

is pentaaquachlorochromium(III) or,pentaaquachlorochromium(2+).

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6. Using either system, if the transition metal complexis negative in charge, the name of the metal ends inate.

For example, [Pt(NH3)2Cl4]2- is nameddiamminetetrachloroplatinate(II).

For metals with Latin names, the negativelycharge complex uses:

ferrate (for Fe) argentate (for Ag)plumbate (for Pb) stannate (for Sn)

aurate (for Au) cuprate (for Cu)

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7. The complete name of the complex must also

indicate the presence of geometric isomers. Prefixes

such as cis, trans, mer , and fac are used to indicate

the relative positions of similar ligands.

In addition, stereoisomers are also possible with

tetrahedral and octahedral geometries, and optical

isomers are indicated with the prefixes ∆ and Λ.

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Names of Common Ligands

Formula NameBr- bromo

CO32- carbonato

Cl- chloro

CN- cyano

H- hydrido

OH- hydroxo

O2- oxo

prefix indicating + ligand name + metal + (oxidation ## of ligands in roman numerals)

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Polydentate Ligands

Formula Name

NH2CH2CH2NH2 ethylenediamine (en)

Both amines of the

ligand can attach at the

metal forming a ring.

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Polydentate Ligands

ethylenediaminetetraacetate (EDTA)

EDTA is a hexadentate ligand.

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EDTA

EDTA can wrap

around a metal ion

to coordinate at 6

(octahedral) sites.

Ligands that bind to

more than one site

are called chelatingagents.

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Constitution and GeometryThree factors govern the coordination number of a complex:

1. The size of the central atom or ion.2. The steric interactions between the ligands.

3. Electronic interactions between the central atom or ion and the ligands.

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Intermediate coordination numbersComplexes of metal ions with the intermediate coordination numbers

four, five, and six are the most important class of complex

T d symmetry

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K3[Fe(CN)6]

K2[PtCl4]

Na2[Fe(CO)4]

[Co(H2O)2(NH3)4]Cl3

[Ni(H2O)(NH3)4]SO4

Na2[OsCl5N]

[CoCl(NO2)(NH3)4]Cl

[CoCl(NH2)(en)2]NO3

[FeH(CO)3(NO)]

[PtCl(NH2CH3)(NH3)]Cl

NOW some for you to try!!!

Potassium hexacyanoferrate(III)

Potassium tetrachloroplatinate(II)

Sodium Tetracarbonylferrate(II)

Tetraammindiaquacobalt(III) chloride

Tetraaminediaquanickel(II) sulfate

Sodium pentachloronitridoosmate(VI)

Tetraaminechloronitritocobalt(III) chloride

Amidochlorobis(ethylenediamine)cobalt(III) chloride

Tricarbonylhydridonitrosyliron(I) ?(II)??

Amminchloro(methylamine) platinum(II) chloride

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Isomerism

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http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Coordinatio

n_Chemistry/Isomers/Structural_Isomers_in_Inorganic_Mole

cules

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Stereoisomerism

Stereoisomers have the sameconnectivities but different spatialarrangements.

In geometric isomers, the ligands havedifferent spatial arrangements about themetal ion.

Optical isomers are compounds withnon-superimposable mirror images.

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Geometric Isomerism

Geometric isomers differ in the geometric

arrangement of the ligands around the central

metal.

Common examples are square planar complexes such as [Pt(NH3)2Cl2].

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Geometric Isomerism

In octahedral complexes, the prefixes cis andtrans are used for complexes of the form

[MX4Y2]

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Octahedral ComplexesFor complexes with the formula

[MX3Y3], there are two spatial

arrangements of the ligands.

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Octahedral Complexes

fac stands for facial, and mer stands for

meridian.

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Chirality

Both four-coordinate and six-coordinatecomplexes exhibit chirality. Chiral molecules have

either no symmetry elements (other than identity),

or only a Cn axis.

Tetrahedral complexes can be chiral in the

same way that organic compounds are: they may

have four different ligands. They may also have

unsymmetrical chelating ligands.

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Chirality

Square-planar

complexes can

also be chiral,as seen in

these

compounds of

platinum(II) andpalladium(II).

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EXAMPLE 7.5 Recognizing chirality

Which of the complexes (a) [Cr(edta)], (b) [Ru(en)3]2, (c)

[Pt(dien)Cl] are chiral? Answer If a complex has either a mirror plane or centre of

inversion, it cannot be chiral. If we look at the schematic

complexes in (74), (75), and (76), we can see that neither (74)

nor (75) has a mirror plane or a centre of inversion; so both

are chiral (they also have no higher Sn axis). Conversely, (76)has a plane of symmetry and hence is achiral. (Although the

CH2 groups in a dien ligand are not in the mirror plane, they

oscillate rapidly above and below it.)

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Optical Isomers

Octahedral complexes containing

polydentate ligands can form optical

isomers. Complexes with three rings,

such as [Co(en)3]3+, can be viewed like a

propeller with three blades. The structure

can be either left or right handed, with

non-superimposable mirror images.

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Optical Isomers

The upper isomer

is right handed, and the

lower one is left

handed.

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Optical Isomers

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Optical Isomers

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Optical Isomers

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Optical Isomers

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Optical Isomers

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Optical Isomers

The right-handed

isomer requires going

clockwise to get from

the upper triangle tothe lower one. The

prefix for this isomer

is ∆.

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Optical Isomers

The left-handed

isomer requires going

counterclockwise to

get from the upper triangle to the lower

one. The prefix for

this isomer is Λ.

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http://www.people.carleton.edu/~mcass/TrisChelates/Index.html

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Isomers

• Co(III) and ethylenediamine react to form

several products. cis[CoCl2(en)2]+ is

violet, and the trans isomer is green. The

reaction also forms a yellow product,

[Co(en)3]3+. Determine the number of

isomers of each of the products. Label

any enantiomers with the proper prefix (∆or Λ).

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Isomer Problem

The yellow product is [Co(en)3]+3. It

exists as an enantiomeric pair.

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Isomer Problem

The violet product consists of a pair of optical

isomers. The green product is not optically

active, as it has a mirror plane.

d i i h b k l f hi f

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•Hydrate isomerism: the best known example of this occurs for

chromium chloride "CrCl3.6H2O" which may contain 4, 5, or 6

coordinated water molecules.[CrCl

2

(H2

O)4

]Cl.2H2

O bright-green

[CrCl(H2O)5]Cl2.H2O grey-green

[Cr(H2O)6]Cl3 violet

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Naming

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Summary

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Summary

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DSU 2015 -IC-Ch7-5