BY:HELLINE & DORITHY (6AS’10)

CHEMISTRYAN INTRODUCTION TO THE

CHEMISTRY OF d-BLOCK ELEMENTS

INTRODUCTION

1st row of d-Block elements consist 10 elements

All except scandium & zinc are transition elements.

E.g: Sc ([Ar]3d 14s 2 ) → Sc3+ ([Ar]3d 04s

0) Zn([Ar]3d 104s 2) → Zn2+ ([Ar]3d

104s 0)

GENERAL CHEMICAL PROPERTIES OF THE TRANSITION ELEMENTS Exhibit variable oxidation states in

their compounds Form complex ions Form coloured compounds Show catalytic properties

VARIABLE OXIDATION STATES

Ti V Cr Mn Fe Co Ni Cu

+1

+2 +2 +2 +2 +2 +2 +2 +2

+3 +3 +3 +3 +3 +3 +3

+4 +4 +4 +4 +4 +4 +4

+5 +5 +5 +5 +5

+6 +6 +6

+7

HIGHER OXIDATION STATES OF TRANSITION ELEMENTS

Ti TiO2+(+4)

V VO2+ (+4);VO+ (+5)

Cr CrO42- (+6) ;Cr2O7

2- (+6)

Mn MnO42- (+6);MnO4

- (+7)

Fe FeO42- (+6)

COMPLEX IONS FORMATION

Ions which are formed when a metallic or ions (ligands) by datives bonds.

E.g,oxygen atom (in H2O) known as donor atoms

Central metal ions (lewis acids) must have high charge density and empty orbitals to accept the lone pair of electrons from the ligands

CLASSIFICATIONS OF LIGANDS Monodentate ligand -one donor

atom can form one dative bond. E.g, F- (fluoro) ,Cl- (chloro),NO2

- (nitro)

Bidentate ligand-one donor atom can multiple datives bond. E.g,ethanedioate ion

Hexadentate ligand-number of datives bonds that can be formed by the ligands. E.g,EDTA(ethylenediaminettetracetate)

NAMING OF COMPLEXES

Precedes the name of the central metal ion

Neutral or cationic complexes-normal name

Anionic complex-named as its salt Named as one word without space

between ligands and metals ions Prefix bis,tris and tetrakis-replaced

the prefixes of di,tri and tetra

THE GEOMETRY OF COMPLEXES ION Depends on the number of datives bonds

formed between the central ion and the ligands

Complexes with coordination no.of:2-linear

e.g. diamminesilver(I)4-either tetrahedral or square planar

e.g. tetraamminecopper (II)6-octahedral

e.g. hexaaquairon (II)

TETRACARBONYLNICKEL OCTAHEDRAL

COLOUR OF COMPLEXES

Most are coloured Depends on:

-the nature of the central metal ion -the oxidation state of the metal ion -the type of ligand

E.g: Mangnase:MnO42- (green),

MnO4- (purple)

Aqueous transition metal cations are usually coloured

CATALYTIC PROPERTIES

Are important catalysts especially in commercial processes

Due to ability to exhibit variable oxidation states or have empty orbitals in their valence shell

REACTIONS THAT ARE CATALYSED BY TRANSITION ELEMENTS UR COMPOUND

PROCESS REACTION CATALYST

CONTACT 2 SO2(g) + O2(g) ⇌ 2 SO3(g) V2O5(s)

HABER N2 (g) + 3H2(g) ⇌ 2 NH3(g) Fe(s)

HYDROGENATION

CH3 −CH = CH2 (g) →CH3 −CH2 CH3

(g)Ni(s)

THERMAL DECOMPOSITION

2KClO 3 (s) → 2KCl (s) + 3O2 (g) MnO2 (s)

OXIDATION 2I- (aq) +S2O82- (aq) → I2 (aq) + 2

SO42- (aq)

Fe3+ (aq) or Fe2+ (aq)

HOMOGENOUS CATALYST

Catalyst+reactants are in the same physical state

E.g: 2I- (aq) +S2O82-(aq) → I2 (aq) +

2 SO42-(aq)

2KClO 3(s) → 2KCl (s) + 3O2 (g)

HETEROGENEOUS CATALYSTS

Catalyst is in different physical state from the reactants

E.g: H2 (g) + I 2 (g) ⇌ 2HI (g) (catalyst=solid nickel)

N2 (g) + 3H2(g) ⇌ 2 NH3(g) (catalyst=solid ferum)

ISOMERISM IN COMPLEXES

ISOMERISM-the existence of 2 or more different compounds havind the same molecular formula

3 types:-geometrical-optical-structural

GEOMETRICAL ISOMERISM Shown by:

a.square planar complexes with the formula of Ma2b2b.octahedral complexes with the formula of Ma4b2 and Ma3b3c.octahedral complexes with the formula of M(x-x)2b2

Where a and b are monodentate ligands and (x-x) are bidentate ligands

OPTICAL ISOMERISM Occurs in octahedral complexes which

do not have a plane of symmetry E.g. EDTA complexes:

Structural isomerism Occurs in complexes having the same

molecular formula but different with respect to the type of ligands that are bonded to the central ion

An interesting example-chromium having the molecular formula of CrCl3.6H2O

There are 3 compounds-dark green,light green and purple

Can be differentiate by the num of moles of silver chloride precipitated when excess aqueous silver nitate is added

USES OF d-BLOCK ELEMENTS & THEIR COMPOUNDS

TITANIUM CHROMIUM COBALT AND MANGANESE

THE USES OFCHROMIUM TITANIUM COBALT

PARAMAGNETISM Weakly attracted by a magnetic field Caused by the presence of unpaired

electronsPARAMAGNETIC-transition metal ions that

have unpaired electronsFERROMAGNETIC-substance that are

strongly attracted by a magnetic fielde.g: iron,nickel and cobalt

DIAGMAGNETIC substances-have a slight tendency to be repelled by a magnetic field and contain no unpaired electrons

Thank you…

QUESTIONS…

1. Cisplatine is the cis isomer of the Pt(NH 3) 2Cl 2 complex that is used as anti –tumor agent.

a. Give the IUPAC name for cisplatine

b.Draw the structure of cisplatine

2. Bis (ethylenediamine)dichlorocobalt (III) is an example of a complex ion that exhibits stereoisomerism.

a. Draw the structure of all the stereoisomers of bis (ethylenediamine)dichlorocobalt (III)

b. Write the valence shell electronic configuration of the cobalt(III) ion in the bis (ethylenediamine)dichlorocobalt (III) complex.