D-block Metal Chem.

7/28/2019 D-block Metal Chem.

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Ground state electronic configurations

Electroneutrality principle

Kepert Model

Coordination Numbers

Chapter 20

d-block metal chemistry:

general considerations


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CrCr

MnMn

FeFe


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Reactivity of MetalsReactivity of MetalsReactivity of Metals

42 OsOO2Os +

FeSSFe +

3)nI,Br,X4;nCl,X5;nF,(XVXX2

V n2 ======+n

CuSO45H2OMnCO3

NiSO4

CoCl2CoCl26H2O CrK(SO4)212H2O

K3Fe(CN)6

O6H][CoCl4Cl])[Co(OH 22

4

2

62 +++

pink dark blue


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Oxidation StatesOxidation StatesOxidation States


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Coordination compound a compound in which a smallnumber of molecules or ions called ligands surround acentral metal atom or ion.

Ligand atom or ion that bonds to the central atom. Eachligand shares a pair of its electrons with the metal.

Coordinate-covalent bond L: M (both electrons arefrom the ligand.

Coordination number The number of ligands around ametal atom or ion.

Coordination sphere The collection of ligandssurrounding the metal atom, typically enclosed inbrackets in the formula.

[ML6]Xn

Coordination ChemistryCoordination ChemistryCoordination Chemistry


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NH3Ammonia has a lone pair ofelectrons that may be sharedwith a metal atom or ions.

This type of ligand, capable of sharing 1 pair of electrons, is referredto as a monodentate ligand.

Ethylenediamine (1,2 diaminoethane)has two lone pair of electrons thatmay be shared with a metal atom orions.

This type of ligand, capable of sharing 2 pairs of electrons, isreferred to as a bidentate ligand.

M

LigandsLigandsLigands

O t h e r t y p e s o f l ig a n d s

Bridging ligands: contain two pairs of electrons that areshared with two metal atoms or ions simultaneously

M:L:M

Common bridging ligands include amide (NH2-), cyanide (CN-),

hydroxide (OH-), nitrite (NO2-), peroxide (O2

2-), thiocyanate (SCN-)

Ambidentate ligands: can use one of two different atoms to share apair of electrons with a metal atoms or ions simultaneously

M:AB: OR :AB:M

Common ambidentate ligands include cyanide (CN-), nitrite (NO2-),

thiocyanate (SCN-).


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Nomenclature of Inorganic CompoundsNomenclature of Inorganic Compounds

1. Anionic Ligands end in o

NCS- isothiocyanatoCH3COO- acetatoC2O4

2- oxalatoO2- oxo

SCN- thiocyanatoClO3- chloratoCO3

2- carbonatoI- iodo

NC- isocyanoS2O32- thiosulfatoNO3

- nitratoBr- bromo

CN- cyanoSO42- sulfatoONO- nitritoCl- chloro

OH- hydroxoSO32- sulfitoNO2- nitroF- fluoro

2. Neutral Ligands are named as the neutral molecule.

CH3NH2 methylamineNH2CH2CH2NH2 ethylenediamine

(C6H5)3P triphenylphosphineC2H4 ethylene

3. Special (historical) names for neutral ligands.

NO nitrosylNH3 ammine

CO carbonylH2O aqua

Nomenclature of Inorganic CompoundsNomenclature of Inorganic Compounds

4. Cationic ligands end in -ium.

NH2NH3+ hydrazanium

5. Ambidentate ligands are indicated by:

Using special names for the two forms e.g.

a.) nitro and nitrito for NO2- and ONO-, respectively.

b.) placing a symbol of the coordinating atom in front of thename of the ligand, for example, S-thiocyanato and N-

thiocyanato for SCN- and -NCS-

6. Bridging ligands are indicated by placing a - before thename of the ligand.


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Nomenclature of Inorganic CompoundsNomenclature of Inorganic Compounds1. First name the cation, then the anion.

2. List the ligands alphabetically.

3. Indicate the number (2, 3, 4, 5, 6) of each type of ligand by:

a) The prefixes di-, tri-, tetra-, penta-, hexa- for:

1) All monatomic ligands

2) Polyatomic ligands with short names

3) Neutral ligands with special names

b) The prefixes bis-, tris-, tetrakis-, pentakis-, hexakis- for:

1) Ligands whose names contain a prefix of the first type. (di-, tri-etc.)

2) Neutral ligands without special names

3) Ionic ligands with particularly long names

4. If the anion is complex, add the suffix ate to the name of the metal (insome cases remove ium from the metal e.g. ruthenate). Some metals,Cu, Fe, Au, Ag become cuprate, ferrate, aurate, and argentate.

5. Put the oxidation state in Roman numerals in parenthesis after the nameof the central metal.

Complex FormationComplex FormationComplex Formation

Electroneutrality principle is an approximate method of estimating the

charge distribution on molecules and complex ions. It states that the

distribution of charge in a molecule or ion is such that the charge on a single

atom is within the range +1 to -1 (ideally close to zero).


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Coordination numbers and geometries

Kepert Model

Coordination numbers and geometriesCoordination numbers and geometries

KepertKepert ModelModelRationalizes the shape of the d-block metal ions [MLn], [MLn]m+, or [MLn]m-. by

considering the repulsions between groups L. Lone pairs of electrons are ignored.

Coordination Number = 1

M

Very rare, but known for organometallic compounds of the typeCuC6H2(C6H5)3 and AgC6H2(C6H5)3.

The ligand 1,3,5-triphenylbenzene is highly sterically hindered.


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Linear

Bent (rare)

Ag[NH3]2+

[Hg(CH3)2]

[CuCl2]-



HgI3-

CuBr(P(C6H5)3)2 tris(triphenylphospine) gold(I) cation

[AgTe[AgTe77]]33--

[Fe{N(SiMe[Fe{N(SiMe33))22}}33]]BF3


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Square Planar Coordination

Square planar coordination compounds are most common for d8 metalssuch as Ni(II), Pd(II), Pt(II), Au(III) and d9 metals such as Cu(II).

Only one isomer is possible for MA3B.

Two possible isomers for MA2B2 and MA2BC

cis-diamminedichloroplatinum(II) and trans-diamminedichloroplatinum(II)


Tetrahedral Coordination Spheres

Two ways to generate a chiral tetrahedral structure

A

B

C

D

1)

M

2)

A

B

B

M

A

Difficult to synthesize. Using an asymmetricchelating ligand.



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Coordination Number = 4, 5


Two possible geometries for C.N. = 5Trigonal Bipyramidal Square pyramidal

Berry mechanism for the interconversionof trigonal bipyramidal and square planarforms of Fe(CO5)

Small difference inenergy between thetwo geometries.

In some cases,interconversionoccurs very rapidly.


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+

trans-tetraamminedichlorocobalt(III) cation

+

cis-tetraamminedichlorocobalt(III) cation

MA4B2 two possible geometric isomers

MA3B3 two possible geometric isomers

fac-triamminetrichlorocobalt(III)

Co(NH3)3Cl3

mer-triamminetrichlorocobalt(III)


1

2

34

5

6

In complex octahedral molecules, a numbering system may be

utilized to simplify naming.

For more information on naming, see The Rulesof Inorganic Nomenclature (the 'Red Book'),first published in 1958 by the IUPAC

Available for free on Google Books

OH2

OH2

CNH3N

H3N

CN

R/S-1,2-diammine-3,4-diaqua-5,6-dicyanocobalt(III)

Start numbering by ligandalphabetically, noting that 1,6must be trans to each other.



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Compounds with chelating ligands (multidentate)

acetylacetonate

[CH3COCHCOCH3]-

R/S-tris(aceyltacetonato)chromate(III) ion

Resembles a propeller (chiral)


Compounds with chelating ligands (multidentate)



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Pentagonal BipyramidalCapped Trigonal PrismaticCapped Octahedral

ZrF73-[W(CO)4Br3]

- [NbF7]2-


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Square Antiprism

[Zr(ox)4]4-

[Zr(C2O4)4]4-

Triangular-faced dodecahedron

[Mo(CN)8]3-



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Tricapped trigonal prism

ReH92-



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Structures of Coordination CompoundsStructures of Coordination Compounds

Isomers: Chemical species having the same number andtypes of atoms but different properties.

Stereoisomers: Isomers that havethe same number and types ofchemical bonds but differing in thespatial arrangement of thosebonds.

Structural isomers: Isomersthat have a differing numbersand types of chemical bonds.

1) Optical isomers (enantiomers):Contain different spatialarrangements that give chirality;

possess nonsuperimposable mirrorimages.

2) Geometric isomers: Isomers withdiffering spatial arrangements thatresult in different geometries.

1) Coordination isomers: Isomersthat differ due to an interchange ofligands among coordinationspheres.

2) Ionization isomers: Isomers

that differ by interchange ofgroups between coordinationspheres and countercations.

3) Linkage isomers:

Isomers that differ by the bondingsite used by an ambidentate ligand.


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D-block Metal Chem.

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