final not yet

- Transition metals and refractory metals (Cr, Mo, W).

- Wide oxidation states.

- Include:

Chromium (Cr) Molybdenum (Mo) Tungsten (W)

and Seaborgium (Sg).

GROUP VIB - INTRODUCTION1) Overview:

GROUP VIB - INTRODUCTION1) Overview:

Tungsten:

• Lowest coefficient of thermal expansion

• High melting point

• Strength of tungsten are due to strong covalent bonds

Highest meltingpoint

GROUP VIB - INTRODUCTION2) Natural resouces:

Chromium

Crocoite (PbCrO4) Chromite (FeCr2O4)

https://en.wikipedia.org/wiki/Crocoite

https://en.wikipedia.org/wiki/Chromite

2) Natural resouces:

GROUP VIB - INTRODUCTION

Molybdenum

Molybdenum:

Wulfenite ( PbMoO4 )

Powellite (CaMoO4 )

Molybdenite ( MoS2)2

2) Natural resouces:

GROUP VIB - INTRODUCTION

Wolframite (Fe,Mn)WO4

Scheelite (CaWO4),

Hübnerite (MnWO4).

Tungsten :

GROUP VIB – PHYSICAL PROPERTIES

• White metal silver shiny

• Heavy metals

• Good electrical conductivity

Thermal conductivity

• Highest melting point

GROUP VIB – PHYSICAL PROPERTIES

Chromium Molybdenum Tungsten

Atomic number 24 42 74

Electron configuration [Ar] 3d54s1 [Kr] 4d55s1 [Xe] 4f145d46s2

Melting point 1907°C 2622°C 3414°C

Boiling point 2671°C 4639°C 5555°C

Relative atomic mass 51.996 95.95 183.84

Key isotopes 52Cr, 53Cr and 54Cr 95Mo, 96Mo, 98Mo 182W, 184W, 186W

GROUP VIB – CHEMICAL PROPERTIES

• Sustained with air, moisture and carbon dioxide

• Reacts with oxygen at high temperatures

4Cr (s) + 3O2 (g) → 2Cr2O3 (s) ( in 300oC, ∆Ho = -1141 kJ/mol )

2Mo (s) + 3O2 (g) → 2MoO3 (s) ( in 600oC, ∆Ho = -745 kJ/mol )

2W (s) + 3O2 (g) → 2WO3 (s) ( in 600oC, ∆Ho = -842 kJ/mol )


• Reacts with fluorine gas at room temperature

2Cr(s) + 5F2(g) → 2CrF5(s) [red]

• Chromium reacts with fluorine, F2, at 400°C and 200-300 atm

Cr(s) + 3F2(g) → CrF6(s) [yellow]

2Cr(s) + 3F2(g) → 2CrF3(s) [green]

2Cr(s) + 3Cl2(g) → 2CrCl3(s) [red-violet]

2Cr(s) + 3Br2(g) → 2CrBr3(s) [very dark green]

2Cr(s) + 3I2(g) → 2CrI3(s) [very dark green]


. In high temperature, Cr, Mo, W react with others halogen.


• React with non-metallic elements in high temperature

W + N2 → WN2 ( 2000oC – 2500oC )

Mo + C → MoC ( > 800oC )

W + C → WC (> 1400oC )

• No effect with hydrogen


• React with water at high temperatures

2Cr + 3H2O → Cr2O3 + 3H2 Mo + 2H2O → MoO2 + 2H2 W + 2H2O → WO2 + 2H2

• Chromium can dissolve in dilute solution of HCl and H2SO4

Cr + 2HCl → CrCl2 + H2 ( Eo Cr

2+/Cr = -0.91V )

• Mo and W are not effective with HCl and H2SO4


W + 8HF +2HNO3 → H2WF8 + 2NO + 4H2O

Mo + Na2CO3 + 3NaNO3 → Na2MoO4 + 3NaNO2 + CO2

Ionic Radius

0.87 Å Cr2+ coordination number = 6; low spin0.94 Å Cr2+ coordination number = 6; high spin

0.755 Å Cr3+ coordination number = 60.55 Å Cr4+ coordination number = 40.69 Å Cr4+ coordination number = 60.40 Å Cr6+ coordination number = 40.58 Å Cr6+ coordination number = 6


In coordination compound


• The metal also forms many compounds of intense colour:

Chromates (e.g. Na2CrO4, PbCrO4) – Yellow

sodium chromate

Dichromates (e.g K2Cr2O7) ............. Orange-red

potassium Dichromate


Chromic acid, CrO3 .......................... Red

Chromic acid

Chromium(III) oxide, Cr2O3 .............. Green

Chromium(III) oxide

GROUP VIB – BIOLOGYCAL ROLE

• Chromium is trace element

• Biologically active form of chromium (III) might play a role in the insulin signaling pathway

Chromium


Molybdenum

• The reaction that nitrogenase enzymes perform is:

N2 + 8H+ +8e- + 16ATP + 16H2O → 2 NH3 + H2 + 16 ADP + 16Pi

• Molybdenum is cofactor enzymes


• Human dietary intake and deficiency

People deficient molybdenum are prone to toxic reactions to sulfites in foods

Molybdenum is also present within human tooth enamel and may help prevent its decay.

Pork, lamb, and beef liver, include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers and cereal grain.


• Related diseases

Congenital molybdenum cofactor deficiency disease, seen in infants

Neurological damage.


• Used by some bacteria, but not in eukaryotes

Tungsten

• Tungsten-using enzymes reduce carboxylic acids to aldehydes.

• Tungsten has been studied as a biological copper metabolic antagonist

GROUP VIB – APPLICATION IN LIFE

Chromium

• Metallurgy


Dye and pigment

Wood preservative

Tanning

Refractory material

Catalysts


Alloys

Molybdenum

Used as a fertilizer for some plants

Certain low voltage X-ray sources


Tungsten

Hard materials

Alloys

Armaments

Niche uses

Gold substitution

Electronics

GROUP VIB – GROUP VIB – CHROMIUM COMPOUNDS

• Chromium(II) oxide (CrO) is a black powder

• Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide

H3PO2 + 2 Cr2O3 → 4 CrO + H3PO4

• CrO is a basic oxide : CrO + 2HCl -> CrCl2 + H2O

• CrO is a reducing agent: CrO + 4HNO3 c Cr(NO3)3 + NO2 + 2H2O

Chromium(II)

GROUP VIB – CHROMIUM COMPOUNDS

Chromium(III) oxide

• One of principal oxides of chromium

Cr2O3

• Used as a pigment

• Occurs as the rare mineral eskolaite

eskolaite


• Chromium(III) oxide is amphoteric . It dissolves in concentrated alkali to yield chromite ions.

Cr2O3 + 6HCl -> 2CrCl3 + 3H2O

Cr2O3 + 2NaOHc + 3H2O -> 2Na[Cr(OH)4]

https://en.wikipedia.org/wiki/Amphoteric


Preparation

• Potassium dichromate with sulfur at high temperatures

K2Cr2O7 + S Cr2O3 + K2SO4

• Decomposition of chromium salts

(NH4)2Cr2O7 N2 + Cr2O3 + 4H2O


Chromium(VI) oxide

• Has chromium in its +6 oxidation state

• It is a dark red crystalline solid used in cleaning glass

https://simple.wikipedia.org/wiki/Chromium

https://simple.wikipedia.org/wiki/Oxidation_state

https://simple.wikipedia.org/wiki/Crystalline


• Properties

It is a strong oxidizing agent

Can ignite alcohol

Very toxic and irritates skin.

Chromium(VI) oxide

https://simple.wikipedia.org/wiki/Oxidizing_agent

https://simple.wikipedia.org/wiki/Oxidizing_agent

https://simple.wikipedia.org/wiki/Burn

https://simple.wikipedia.org/wiki/Alcohol

https://simple.wikipedia.org/wiki/Toxic

Stronger oxidizing agent than chromate

It dissolves in water to make chromic acid and dichromic acid :

CrO3 + H2O -> H2CrO4

2CrO3 + H2O -> H2Cr2O7

Reacts with strong bases to make chromates :

CrO3 + 2NaOH -> Na2CrO4 + H2O

GROUP VIB – CHROMIUM COMPOUNDS Chromium(VI) oxide

https://simple.wikipedia.org/wiki/Solution

https://simple.wikipedia.org/wiki/Chromic_acid

https://simple.wikipedia.org/wiki/Base_(chemistry)


• Preparation

Normally made by reacting sodium chromate or potassium chromate with sulfuric acid

Chromium(VI) oxide

https://simple.wikipedia.org/wiki/Sodium_chromate

https://simple.wikipedia.org/wiki/Potassium_chromate

https://simple.wikipedia.org/wiki/Sulfuric_acid


Application

Application

• Used to clean glass

• Used to plate chromate on things.

• Reacts with metals to make a metal chromate

https://simple.wikipedia.org/wiki/Glass


Safety

• A dangerous hazard to the environment.

• A carcinogen and can cause mutations

• Chromium(VI) oxide is very toxic and irritating

https://simple.wikipedia.org/wiki/Carcinogen

https://simple.wikipedia.org/wiki/Carcinogen

https://simple.wikipedia.org/wiki/Mutation


Chromate and Dichromate

• Chromate, CrO42-, is a salt of chromic acid

• Yellow color in basic conditions.

A sample of potassium chromate



• Dichromate, Cr2O72-, is a salt of dichromic acid

• Strong orange color in acidic conditions.

A sample of potassium dichromate


• Strong oxidizing agent but it is a bad precipitating agent.

• Used as a precipitating agent but it is a poor oxidizing agent.


2CrO42− (s) + 2H+(aq) H⇌ 2O(l) + Cr2O7

2− (aq) Kc=3.2×1014

• In acidic solution, the forward reaction is favored. In basic solution, the reverse reaction is favored.

GROUP VIB – CHROMIUM COMPOUNDS Chromate and Dichromate

2Na2CrO4 + H2SO4 -> Na2Cr2O7 + Na2SO4 + H2O

Na2Cr2O7 + 2NaOH -> 2Na2CrO4 + H2O

GROUP VIB – CHROMIUM COMPOUNDS Chromate and Dichromate

6FeSO4 + K2Cr2O7 + 7H2SO4 -> 3Fe2(SO4)3 + K2SO4 + Cr2(SO4)3 + 7H2O

• In acidic environment, salts of chromate and dichromate are strong oxidizing agents:

GROUP VIIB - INTRODUCTION1) Overview:

MANGANESE (Mn) TECHNETIUM (Tc) RHENIUM (Re)

GROUP VIIB – PHYSICAL PROPERTIES

• Manganese

- Hard metal - Lustrous silver-blue - Mp: 1519 / Bp: 2235

• Technetium

- Silver - Mp=2430, Bp = 5150

• Rhenium

- Silver, - Often encoutered as grey powder, - Mp = 3459, Bp = 5900.

GROUP VIIB – PHYSICAL PROPERTIESSources

Manganese:

• The 5th most abundant metal in Earth’s crust.

• Pyrolusite (MnO2) and rhodochrosite (MnCO3).

Pyrolusite (MnO2) rhodochrosite (MnCO3)

GROUP VIIB – CHEMICAL PROPERTIES

Technetium

• Uranium nuclear fuel reaction.

Rhenium

• In platinum ores.

uranium ores.

platinum ores

Sources

• Doesn’t accur in nature as uncombined

GROUP VIIB – CHEMICAL PROPERTIESManganese

1. With O2:

3Mn(s) + 2O2(g) → Mn3O4(s)

2. With halogen:

Mn(s) + Cl2(g) → MnCl2(s)

Mn(s) + Br2(g) → MnBr2(s)

Mn(s) + I2(g) → MnI2(s)

- Moderately active metal

3. With nitrogen

3Mn(s) + N2(g) → Mn3N2(s)

GROUP VIIB – CHEMICAL PROPERTIES

5. In water, Mn slowly attack with H2O

6. In the first row of d-block metal, Mn has the widest range of oxidation states, from II to VII.

4. React with Oxygen

4Tc + 7O2 → 2Tc2O74Tc + 7O2 → 2Tc2O7

GROUP VIIB – COMPOUNDS Manganese (II) [3d5]

• Manganese (II) oxide MnO (green solid):

Basic oxide Insoluble in water Soluble in acids, give pink solution, contain

[Mn(H2O)6]2+

Manganese (II) oxide

GROUP VIIB – COMPOUNDS

• Ion Mn2+ is easy to be oxidize.• Mn(OH)2 : white, rapidly dark in air as the reaction

4Mn(OH)2 + O2 2Mn2O3 + 4H2O

• Mostly salts of Mn is soluble in water. MnSO4 is very stable, MnPO4 and MnCO3 are sparingly soluble.

Manganese (II) [3d5]

→

• Manganese (III) oxide Mn2O3

MnO2 |1070K| Mn2O3

• Ion Mn3+ is less unstable in the presece of high concentration of Mn2+ or H+ ion

2Mn3+ + 2H2O Mn2+ +MnO2 + 4H+

GROUP VIIB – COMPOUNDS Manganese (III) [3d4]

→

→

• Manganese dioxide MnO2

Inert in most acids except when heating, but not dissolve to give Mn4+ (cause of the oxidizing characteristic)

MnO2 + 4HCl MnCl2 + Cl2 +2H2O

• With H2SO4 in 110°C:

2MnO2 + 2H2SO4 2MnSO4 + O2 + H2O

+ With KOH in high temperature

4KOH + O2 + 2MnO2 2K2MnO4 + 2H2O

GROUP VIIB – COMPOUNDS Manganese (IV): [3d3]

→

→

→

• The only oxohalide is MnOCl3

• In moist air, MnOCl3 hydrolyses to [MnO4]3-

• Salt of [MnO4]3- is blue and moisture-sensitive and easily react with H+ even H2O

2[MnO4]3- + 2H2O [MnO4]2- + MnO2 + 4[OH]-3[MnO4]3- + 8H+ [MnO4]- + 2MnO2 + 4H2O

GROUP VIIB – COMPOUNDS Manganese (V) [3d2]

→

→

• Ion MnO42- have deep green color and is unstable in acid medium, even in H2CO3:

3MnO42- + 4H+ 2MnO4- + MnO2 + 2H2O

• K2MnO4 is a powerful oxidizing agent, usually used in organic chemistry experiment.

GROUP VIIB – COMPOUNDS Manganese (VI): [3d1]

→

GROUP VIIB – COMPOUNDS

Most common is KMnO4: purple, strong oxidizing

4MnO4- + 4H+ 3O2 + MnO2 + 2H2O

Manganese (VII): [3d0]

→

• Oxide:

* Re2O7 is a yellow volatile oxide, hygroscopic compound.It dissolves in water as the reaction:

Re2O7 + H2O 2HReO4

• Halogenide:

ReCl5 + 3Cl2O ReO3Cl + 5Cl2

Tc2O7 + 4HF 2TcO3F + H3O+ + [HF2]-

GROUP VIIB – COMPOUNDS Compound of Technetium and Rhenium

→

→

→

GROUP VIIB –

The equilibrium constants for the formation od Mn(II) complexes are relatively low as Mn2+ ion has no ligand field stabilization energy. However, chelating ligand (ox, en, EDTA4-), form complexes isolable form aqueous solution. Some ex: [MnX4]2-, [MnCl6]4- (salt of Na and K).

Only very strong ligand fields give rise to spin pairing as in the ion [Mn(CN)6]4- and [Mn(CNR)6]2+

which have only one unpaired electron.

Mananese (II):

Coordination compound

GROUP VIIB –

Complexes are probably important in photosynthesis, where oxygen evolution depend on Mn.

Mn (III) and Mn (IV)

Coordination compound

GROUP VIIB – Coordination compound

In HCl solution, ReO4- is reduced by hypophosphite, partically to the chloro complexe ion [ReCl6]2- partically to [Re2Cl8]2- ion.

Technetium and Rhenium

GROUP VIIB – APPLICATION IN LIFE

• Essential element in all living things.Many type of enzyme contain Mn

• In human body:+ Our body contain about 12 mgs of Mn.+ We need to take 4 mgs Mn per day, from nuts, bran, wholegrain cereals, tea and parsley.+ Without Mn, bones grow spongier and break more easily.+ Essential for utilisation vitamin B1.

Manganese


Manganese


• The gamma – gray Tc is widely used for medical diagnostic studies.

• Corrosion inhibitor for steel.

• Using limited to close systems as Te radio.

Technetium


• Used for oven filaments and x-ray machines.

• Used as an electrical contact material.

• Used in nickel alloys to make single-crystal turbine blades.

Rhenium


• In steel production : Steel with 1% Manganese : stronger, improve

workability and resistance to wear. Steel with 13% Manganese : very strong and

used for railway, prison bar…• MnO2: used as catalyst, a rubber addition and

to decolourise glass that is green by ion impurities.

• MnSO4: make a fungicide.• MnO: powerful oxidizing agent used in

quantitative analysis.• Used in water purification and economical

bleaching.

Manganese

• MnO2: used as catalyst, a rubber addition and to decolourise glass that is green by ion impurities.

• MnSO4: make a fungicide.

• MnO: powerful oxidizing agent used in quantitative analysis.

• Used in water purification and economical bleaching.


Manganese

Iron (Fe) Cobalt (Co) Nickel (Ni)

GROUP VIII - INTRODUCTION1) Overview:

Ruthenium (Ru) Rhodium (Rh) Palladium (Pd)

Osmium (Os) Iridium (Ir) Platinum (Pt)

PlatinumGroupMetals(PGMs)


Iron:

• Fourth most abundant element in the Earth’s crust

• 3 allotropes of iron is: α-iron (alpha-iron); γ-iron (gamma-iron); and δ-iron (delta-iron).

• Iron is used since prehistoric ages.


Cobalt:

• The name in German is ‘kobalt’, which is goblin.

• It is the 30th most abundant in crustal rocks.


Nickel:

• Is frequently used in coinage in nickel-copper alloys.

• It is the 22nd most abundant in crustal rocks.

• Raney Nickel, an alloy of Aluminum and Nickel, is an important catalyst in organic chemistry.


Platinum Group Metals (PGMs)

• PGMs are often used in jewelry• Catalytic prperties of PGMs are well-known


Platinum Group Metals (PGMs)

• Catalytic properties are important in organic chemistry

GROUP VIII - INTRODUCTION2) Natural resouces:

Iron:

Hematite (Fe2O3) Magnetite (Fe3O4)

Limonite (Fe,Ni)O(OH) Siderite (FeCO3)


Cobalt:

Cobaltite (CoAsS) Skutterudite ((Co,Ni,Fe)As3)

Erythrite (Co3(AsO4) 8H2O)


Nickel:

Garnierite (Ni, Mg)3Si2O5(OH)4)

Limonite (Fe,Ni)O(OH)

Pentlandite ((Ni, Fe)9S8)

GROUP VIII – PHYSICAL PROPERTIES

Iron

White, lustrous metal

Magnetic

Conductorial

Refractory

GROUP VIII – CHEMICAL PROPERTIES

Iron:• Reaction with air to form

various oxide and hydroxide compounds.

• Fe is pyrophoric in air, but the bulk metal is oxidized only when heated.

• Iron reacts on mild heating with a variety of other non – metals (halogens, S, P, B, C, Si)

2Fe + 3X2 → 2FeX3 (X = F, Cl, Br)Fe + 2S → FeS2 (Fool’s gold)


Iron:• Ferrous halides react with binary halogen acid:

Fe + 2 HX → FeX2 + H2

• Reaction with acids:2Fe + 6H2SO4conc → Fe2(SO4)3 + 3SO2 + 6H2O

• Fe also takes part in replacing reactions.Fe + 2AgNO3 deficiency → Fe(NO3)2 + 2Ag

• At high temperature, Fe reduces steam: 3Fe + 4H2O → Fe3O4 + 4H2 (<570oC)

Fe + H2O → FeO + H2 (>570oC)


Iron VI, V and VI:• The highest oxidation states of iron are found in

compounds of [FeO4 ]2- , [FeO4]3- , [FeO4]4- and [FeO3]2-

• Ferrate(VI) is a powerful oxidant.[FeO4]2- + 8H+ + 3e- → Fe3+ + 4H2O

• The reaction of K2FeO4 with KOH in O2 at 1000 K gives K3FeO4, a rare example of an Fe(V) salt.

• Iron(IV) ferrates include Na4FeO4 (made from Na2O2 and FeSO4), Sr2FeO4 (prepared by heating Fe2O3 and SrO in the presence of O2) and Ba2FeO4 (made from BaO2 and FeSO4).


Iron III• Name is ferric

• Iron (III) halides are made by heating iron with halogens.

• Iron (III) oxide is insoluble in water, but dissolves in acid.

• Iron (III) salts and oxide creates Fe2O3.H2O (also written as Fe(O)OH) but often mistaken as Fe(OH)3.

FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl

Iron II• Common name is ferrous.

• Iron (II) halides are made by dissolving the metal in binary halogenic acid. Fe + 2HX → FeX2 + H2


Cobalt:• Reaction with air:

3Co(s) + 4O2(g) → 2Co3O4(s)2Co(s) + O2(g) → 2CoO(s)

• With oxygen with steam as a catalyst:2Co(s) + O2(g) → 2CoO(s)

• With halogens: Co(s) + Br2(l) → CoBr2(s) [green]

• With acids:Co(s) + H2SO4(aq) → Co2+(aq) + SO4

2-(aq) + H2(g)


Cobalt compounds:• With aqua and halogen ligands:

[Co(H2O)6]2+ + 2NH3→[Co(H2O)4(OH)2] (pink) +2NH4+

[Co(H2O)6]2+ + 6NH3→[Co(NH3)6]2+ (brown) + 6H2O

[Co(H2O)6]2+ (pink) + 4Cl− ⇌ [CoCl4]2− (blue) + 6H2O

• With halides: - Anhydrous cobalt dichloride is blue, but the hydrate form is red.


Nickel:• With acids:

Ni + HCl → NiCl2 + H2

Nickel is passive in concentrated HNO3

• Nickel doesn’t react with aqueous alkalis.

• With air: they react with each other in high temperature.Ni + H2O → H2 + NiO

• With halogens: Nickel forms Ni(II) halides with halogens,But with F2, the halide layer prevent further attack.

Nickel compounds:• Organometallic species: usually in low oxidation states.

Nickel is passive in concentrated HNO3

• Ni(II) compounds are important species:

[Ni(NH3)6]2+ [Ni(en)]2+ [NiCl4]2− [Ni(H2O)6]2+

Green Ni(OH)2 is used in NiCd batteries

• Ni(IV) compounds are formed under influence of really strong oxidants. Ex: KNiO6 is formed under oxidation of [Ni(H2O)6]2+ by [S2O8]2- with [IO4]-

• Ni(I) is uncommon: ex [Ni2(CN)6]4-


Iron:• Making steel.• Hemoglobin in blood and myoglobin in

muscle• Essential for energy production

(respiratory chain)• DNA Replication• Glucose Metabolism• Enzyme systems

GROUP VIII – APPLICATIONS

Cobalt:• Making magnets and batteries• Other alloys of cobalt are used in jet

turbines and gas turbine generators• Used in electroplating• Cobalt salts produce brilliant blue colours

for many uses.

Roles (in Biology)• Trace element Part of the active site of

vitamin B12 • Cancer treatment and preserve food

(Radioactive 60Co)• Correct mineral deficiencies (animals)


Nickel:

• It is used in coinage, plating, alloys.• A trace mineral in human and animal body.• Low nickel: reduced growth, decreased life

expectancy, reduced iron absorption leads to anaemia.

• Low nickel in human body can interrupt absorption of calcium into the skeleton.

• Key component in hydrogenase biosynthetic processes.

• Nickel is found in urease – an enzyme that assist plant hydrolyse urea.


GROUP VIIIB – NATURAL RESOURCESIRON:

Iron is the second cheapest most abundant metal Nearly 5.6% of Earth’s crust. Major iron ores are hematite, Fe2O3, magnetite,

Fe3O4, limonite, FeO(OH), and siderite, FeCO3. Pure iron is almost never found in nature.

GROUP VIIIB – NATURAL RESOURCESRUTHENIUM:

Ru is found in nature with the other platinum group. Commercially, it is obtained from pentlandite (a sulfide of iron and nickel) with contains small quantities of ruthenium.

OSMIUM: Osmium occurs uncombined in nature and also in

the mineral osmiridium (an alloy with iridium). Most osmium is obtained commercially from the wastes of nickel refining.

GROUP VIIIB – CHEMICAL PROPERTIESRUTHENIUM & OSMIUM

React with O2:Ru + O2 (>870) RuO2 (non-volatile)Os+ O2 (>870) OsO4 (volatile) Reacte with F2 and Cl2 when heated.

Attacked by mixtures of HCl and oxidizing agents, and by molten alkalis.

Metals:


Ruthenium(VIII) oxide RuO4 and Osmium(VIII) oxide OsO4 is unstable and also a very powerful oxidant.

All the binary halides RuX3 are known but for Os, only OsCl3 and OsI3 have been established; OsF4 is the lowest fluoride of Os.

Binary halides of Ru(II) and Os(II) are not well characterized and there are no oxides

Compounds:


Most of the chemistry of Ru(II) and Os(II) concerns complexes: diamagnetic, low-spin d6, octahedral.

Many low oxidation state complexes of Ru and Os including those of Ru(II) and Os(II) are stabilized by PR3 ( -acceptor) ligands.π

Complexes:

GROUP VIIIB – BIOLOGICAL ROLEIRON:

In biological systems, these oxidation states are limited primarily to the ferrous (+2), ferric (+3) and ferryl (+4) states. Iron required for Hemoglobin in blood Needed for Myoglobin in muscle Essential for energy production (respiratory chain) DNA Replication Glucose Metabolism Enzyme systems in the body that use iron include

Mono - and Di – Oxygenases, protective Peroxidases like catalase and Myeloperoxidase and Several Oxidoreductases.

Foods contain Fe:

GROUP VIIIB – BIOLOGICAL ROLERUTHENIUM:

Ruthenium has no known biological role. Ruthenium(IV) oxide is highly toxic.

OSMIUM: Osmium has no known biological role. The metal is

not toxic, but its oxide is volatile and very toxic, causing lung, skin and eye damage.

GROUP VIIIB – APPLICATIONIRON:

In industry: - Be used to make steel.- Be the manufacture of tools and weapons.In medicine: Iron is usually administered orally to a patient as iron supplement tablets containing an Fe(II) or Fe(III) salt. Iron(II) salts are more typical because they exhibit better solubilities than Fe(III) salts at physiological pH, but Fe(III) has the advantage that, unlike Fe(II), it is not susceptible to oxidation in aqueous solution.

GROUP VIIIB – APPLICATIONRUTHENIUM: Used in electronics industry for chip resistors and

electrical contacts. Used for catalysts for ammonia and acetic acid

production. Used in solar cells, which turn light energy into

electrical energy. Used in some jewellery as an alloy with platinum.

OSMIUM:

Used to produce very hard alloys for fountain pen tips, instrument pivots, needles and electrical contacts

Used in the chemical industry as a catalyst.

GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Metals:

Resistant to corrosion. Pt is more inactive than Pd. Pd reacts with O2, F2 and Cl2 at high temperature. Both can be attacked by aqua regia and molten alkali

metal oxide. Pt + 2 HNO3+ 6 HCl + Cl2 → + 3 H2O + 1/2 O2 +

H2PtCl6 (chloroplatinic acid) + 2 NOCl M(II) and M(IV) are two common oxidation state.

GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds – M(IV) compounds:

All the M(IV) halides are known M + 2X2 MX4 M(IV) is stable for Pt than Pd. Chloroplatinic acid is a great starting material

GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds – M(II) compounds:

Halides of Pd(II) and Pt(II) except PtF2 are known. M(Cl)2 is the precursor for preparation of other

compounds. MCl2 + F2 -> MF¬4 Cisplatin is an anticancer chemical

GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds:

+4 and +5 are the highest oxidation numbers for the two metals.

MBr3 and other M(III) species are mixed-valence compounds.

GROUP VIIIB – BIOLOGICAL ROLENICKEL:

A trace mineral.(Low nickel: reduced growth, decreased life expectancy, reduced iron absorption leads to anaemia. Low nickel in human body can interrupt absorption of calcium into the skeleton.) Key component in hydrogenase biosynthetic

processes. Nickel is found in urease – an enzyme that assist

plant hydrolyse urea.

GROUP VIIIB – BIOLOGICAL ROLE

PALADIUM: Toxic???

PLATINUM: Beside Cisplatin and Carboplatin, Oxaliplatin is also

used in chemotherapy. Platinum salts can be carcinogens, or cause allergy,

deafness, stimulation to dangerous chemicals in human body, such as selenium.

GROUP VIIIB – APPLICATIONNICKEL:

Used to plate other metals to protect them. Used in making alloys such as stainless steel Used in toasters and electric ovens. Nickel is used in batteries. Used as a catalyst for hydrogenating vegetable oils.

Adding nickel to glass gives it a green colour.

GROUP VIIIB – APPLICATIONPALADIUM:

PLATINUM:

final not yet

Science