This ppt contains nitrides, phosphides, oxides and sulfides of transition metals. Contain its synthesis, structure, uses and application etc.

1. Inorganic Materials 1
Pranav N K
MSc. Chemistry

2. Structural variety properties & implication of
 Transition Metal Nitrides
 Transition Metal Oxides
 Transition Metal Phosphide
 Transition Metal Sulfides
Overview

3. Transition metal nitrides(TMNs)
 TMNs are a class of interstitial compounds in which the nitrogen atoms are
integrated into the interstitial sites of the parent metals, possessing the
properties of covalent bonds, ionic crystals and transition metals.
Or
 Complex metal nitrides are materials containing the N 3- anion.
 They have different crystal structures, such as face-centered cubic, hexagonal-
closed packed, and simple hexagonal.
 They have many remarkable properties, such as,
 high melting points,
 hardness,
 electrical conductivity,
 thermal stability and
 sometimes superconductivity.
 They have many potential applications in energy storage, electrocatalysis,
photocatalysis, and other fields.

4. Preparation
1. Powder metallurgical method
Direct reaction of metal or metal
hydride with nitrogen yield metal
nitride (Laboratory method ).
This method is used to prepare pure
compounds.
Very high temperature and pure
vacuum condition are generally
required.

5. 2. Ambient and low pressure synthesis approaches
I. Physical vapour deposition (PVD) and ion implantation techniques
result in thin films of materials including nitrides.
II. Chemical vapour deposition (CVD) and atomic layer deposition
(ALD) techniques are well developed for metal nitride thin films.
3. The ammonolysis of oxides (the dehydrogenation of NH3 by oxides with
the formation of water as a byproduct) provides a convenient route to some
nitrides.

6. Bonding
The bonding in metal nitrides depends on the type of metal and nitrogen
involved.
The bonding in transition metal and nitrides can be described as a mixture of
metallic, covalent, and ionic components.
• Ionic bonding: This occurs when metals of group I and group II form nitrides with
nitrogen atoms. For example, Li 3 N has an ionic bond and shows excellent ionic
conductivity.
• Covalent bonding: This occurs when metals of group III and group IV form
nitrides with nitrogen atoms. For example, BN, AlN, and Si 3 N 4 have covalent bonds
and show high hardness and thermal stability.

7. • Metallic bonding: This occurs when transition metals form nitrides with
nitrogen atoms occupying interstitial sites of the metal lattice. For example, TiN,
ZrN, and CrN have metallic bonds and show high electrical conductivity and
sometimes superconductivity. The bonding in these nitrides is due to the mixing of
d-orbitals of metal and p-orbitals of nitrogen.
o The bonding in transition metal nitrides can also be influenced by the addition
of other elements, such as carbon, oxygen, or other metals

9. • Face-centered cubic (fcc): This structure is adopted by nitrides of group
IVB metals (Ti, Zr, Hf) and some group VB metals (V, Nb, Ta) with a 1:1
stoichiometry. The metal atoms form a fcc lattice and the nitrogen atoms
occupy half of the octahedral interstices. For example, TiN, ZrN, and VN
have this structure.
• Hexagonal-closed packed (hcp): This structure is adopted by nitrides of
group VIB metals (Cr, Mo, W) and some group VB metals (V, Nb, Ta) with
a 1:1 stoichiometry. The metal atoms form a hcp lattice and the nitrogen
atoms occupy half of the octahedral interstices. For example, CrN, MoN,
and WN have this structure.
• Simple hexagonal: This structure is adopted by nitrides of group IIIA
metals (Sc, Y) and some lanthanides with a 1:2 stoichiometry. The metal
atoms form a simple hexagonal lattice and the nitrogen atoms form linear
N 2 units that occupy the trigonal prismatic interstices. For example, ScN
2 , YN 2 , and LaN 2 have this structure.

12. Some examples of transition metal nitrides are:
• Titanium nitride (TiN): This is a hard and wear-resistant material that has a face-
centered cubic structure. It is used as a coating for cutting tools, implants, and jewelry.
• Vanadium nitride (VN): This is a superconducting material that has a face-centered
cubic structure. It has a high critical temperature of 17.5 K and a high upper critical
field of 25 T2.
• Chromium nitride (CrN): This is a corrosion-resistant material that has a
hexagonal-closed packed structure. It is used as a coating for stainless steel,
aluminum, and titanium alloys.
• Molybdenum nitride (MoN): This is an electrocatalytic material that has a
hexagonal-closed packed structure. It can catalyze the hydrogen evolution reaction
and the nitrogen reduction reaction.
• Tantalum nitride (TaN): This is a refractory material that has a face-centered
cubic structure. It can withstand high temperatures and has good electrical
conductivity. It is used as a diffusion barrier and a resistor in microelectronics.

13. • Zirconium nitride (ZrN): This is a golden-yellow material that has a face-centered
cubic structure. It is used as a coating for surgical instruments, jewelry, and optical
devices.
• Iron nitride (FeN): This is a magnetic material that has a hexagonal-closed packed
structure. It is used as a soft magnetic material and a catalyst for ammonia synthesis.
• Tungsten nitride (WN): This is a metallic material that has a hexagonal-closed packed
structure. It is used as a diffusion barrier and a contact material in microelectronics.
• Platinum nitride (PtN): This is a rare material that has a simple hexagonal structure. It
contains N 2 units that are bonded to platinum atoms. It is used as a catalyst for
nitrogen fixation.
• Niobium nitride (NbN): This is a superconducting material that has a face-centered
cubic structure. It has a high critical temperature of 16 K and a high critical current
density. It is used as a superconducting wire and a detector for terahertz radiation.

14. Physical properties
 High melting points: Transition metal nitrides have high lattice energy and strong
metal-nitrogen bonds that make them refractory materials. They can withstand high
temperatures and thermal shocks.
 High density: Transition metal nitrides have high atomic mass and close-packed
crystal structures that make them dense materials. They can be used as heavy metal
substitutes and radiation shielding materials.
 Optical properties: Transition metal nitrides have metallic or semiconducting
properties that make them reflect or absorb light. They can be used as optical coatings
and photonic devices.
 Magnetic properties: Some transition metal nitrides, such as FeN, CrN, and MnN,
exhibit magnetic properties due to the unpaired electrons in the d-orbitals of metal and
p-orbitals of nitrogen. They can be used as magnetic materials and spintronic devices.

15. Chemical properties
• High stability: Transition metal nitrides have strong metal-nitrogen bonds that make
them resistant to oxidation, corrosion, and decomposition at high temperatures.
• High hardness: Transition metal nitrides have high lattice energy and high Young’s
modulus that make them hard and wear-resistant materials. They can be used as
coatings for cutting tools and other applications.
• High conductivity: Transition metal nitrides have metallic or semiconducting
properties that make them good electrical conductors. They can be used as contact
materials and diffusion barriers in microelectronics.
• Superconductivity: Some transition metal nitrides, such as VN, TiN, NbN, and MoN,
exhibit superconductivity at low temperatures. They have high critical temperatures
and high critical fields that make them attractive for superconducting devices.
• Electrocatalysis: Transition metal nitrides have high electrochemical activity and
stability that make them suitable for electrocatalytic reactions, such as hydrogen
evolution, oxygen evolution, oxygen reduction, and nitrogen reduction.

16. Application
 Used in refractories, cerments and laboratory crucible, when applied
using the physical vapour deposition(PVD) coating process. It is commonly
used to coat medical devices,
 Water-resistant surfaces,
 In super conducting devices,
 Used in microelectronics as a contact materials,
 Nano crystalline vanadium nitride has been claimed to have potential for
use in super-capacitor,
 Some are used in coloring agent and
 TMNs are use as catalyst.

18. Transition Metal oxides
Transition metal oxides are compounds composed of oxygen atoms bound to
transition metals.
They have partially filled 3d-shells for the positive metallic cations.
Some examples of transition metal oxides are,
• monoxide(NiO),
• di-oxide(MnO2),
• perovskite(LaNiO3),
• spinel(NiCo2O4),
• titanium dioxide (TiO2),
• ruthenium oxide (RuO2),
• manganese oxide (MnO2),
• cerium oxide (CeO2),
• vanadium pentoxide (V2O5),
• nickel oxide (NiO),and
• cobalt oxide (Co2O3)

19. The nature of bonding in TMOs is determined by the oxidation state
of metal.
Metal oxides with lower oxidation state tend to be more ionic.
Metal oxides with higher oxidation state tend to be more covalent.
Acidity increases with increasing oxidation state of metal.
Eg: MnO is least acidic and Mn2O7 is most acidic.
Oxides of metals having +4 state is amphoteric.
Generally they are not soluble in water.

20. Synthesis
The oxides of the first transition series can be prepared by heating the metals in air.
These oxides are Sc2O3, TiO2, V2O5, Cr2O3, Mn3O4, Fe3O4, Co3O4, NiO, and CuO.
Alternatively, these oxides and other oxides (with the metals in different oxidation states)
can be produced by heating the corresponding hydroxides, carbonates, or oxalates in an
inert atmosphere. Iron(II) oxide can be prepared by heating iron(II) oxalate, and cobalt(II)
oxide is produced by heating cobalt(II) hydroxide:
FeC2O4(s)⟶FeO(s)+CO(g)+CO2
Co(OH)2(s)⟶CoO(s)+H2O(g)
They can react with acids and, in a few cases, with bases. Basic metal oxides at a low
oxidation state react with aqueous acids to form solutions of salts and water. Examples
include the reaction of cobalt(II) oxide accepting protons from nitric acid, and
scandium(III) oxide accepting protons from hydrochloric acid:

21. CoO(s)+2HNO3(aq)⟶Co(NO3)2(aq)+H2O(l)
Sc2O3(s)+6HCl(aq)⟶2ScCl3(aq)+3H2O(l)
The oxides of metals with oxidation states of 4+ are amphoteric, and most are not
soluble in either acids or bases.
Vanadium(V) oxide, chromium(VI) oxide, and manganese(VII) oxide are acidic.
They react with solutions of hydroxides to form salts of the oxyanions VO3−4
MnO−4 .
For example, the complete ionic equation for the reaction of chromium(VI) oxide
with a strong base is given by:

22. Bonding varies from essentially
 ionic (e.g., NiO , CoO) to
 essentially covalent (e.g., Os04 , Ru04 ) , and
 the metallic bond also occurs (e.g., TiO, NbO and Re03 ) .
Bonding
The nature of bonding in oxides of the transition elements
is determined by the oxidation state of the metal.
Oxides with low oxidation states tend to be more ionic, whereas
those with higher oxidation states are more covalent

23. Structures
 The crystal structures range from cubic to triclinic symmetry.
 Simple binary oxides of composition MO usually have the rock-salt structure
and those of type M02 the fluorite, rutile, distorted rutile or still more complex
structures.
 many sesqui-oxides, M203 , have the corundum structure.
 There are also important ternary oxides having the perovskite, spinel, bronze
or garnet structures.

24. Transition metal oxides can have different structures depending on the coordination
and oxidation state of the metal atoms and the arrangement of the oxygen atoms.
Some of the common structures are:
• Monoxide structure: This structure has a metal atom surrounded by six oxygen
atoms in an octahedral geometry. The oxygen atoms form a close-packed cubic or
hexagonal lattice. Examples of transition metal oxides with this structure are NiO,
FeO, CoO, etc.
• Dioxide structure: This structure has a metal atom surrounded by four oxygen
atoms in a tetrahedral geometry. The oxygen atoms form a close-packed cubic or
hexagonal lattice. Examples of transition metal oxides with this structure are TiO2,
SnO2, ZnO, etc.
• Perovskite structure: This structure has a metal atom surrounded by six oxygen
atoms in an octahedral geometry. The oxygen atoms form a cubic lattice with
another metal atom occupying the center of each cube. Examples of transition
metal oxides with this structure are LaNiO3, BaTiO3, SrFeO3, etc.

25. • Spinel structure: This structure has two types of metal
atoms surrounded by four or six oxygen atoms in tetrahedral
or octahedral geometries. The oxygen atoms form a close-
packed cubic lattice with one type of metal atom occupying
one-eighth of the tetrahedral sites and another type of metal
atom occupying half of the octahedral sites. Examples of
transition metal oxides with this structure are NiCo2O4,
MgAl2O4, Fe3O4, etc.
There are also other structures such as layered, tunnel, and
hollow structures that can be formed by transition metal oxides
with different morphologies and compositions.

26. Monoxide spinel

27. Rutile
TiO2 Perovskite structure

28. Chemical properties
• Variable oxidation states: Transition metal oxides can have different oxidation states for the
same metal atom due to the involvement of both s and d electrons in bonding. For example,
manganese can form oxides with oxidation states ranging from +2 to +7, such as MnO,
Mn2O3, MnO2, Mn2O7, etc.
• Colored compounds: Transition metal oxides can have different colors due to the presence
of partially filled d orbitals that can undergo electronic transitions when exposed to visible light.
For example, iron oxides can have colors ranging from pale green (Fe(OH)2) to orange-brown
(Fe(OH)3) to red-brown (Fe2O3).
• Catalytic activity: Transition metal oxides can act as catalysts for various chemical reactions
due to their ability to change their oxidation states and provide active sites for adsorption and
activation of reactants. For example, iron oxide is used as a catalyst in the Haber process for
ammonia synthesis, and manganese oxide is used as a catalyst for the decomposition of
hydrogen peroxide.
• Magnetic properties: Transition metal oxides can exhibit different types of magnetism due to
the presence of unpaired d electrons that can align or interact with external magnetic fields.
For example, iron oxide is ferromagnetic (permanent magnetism), nickel oxide is
antiferromagnetic (opposite alignment of neighboring magnetic moments), and cobalt oxide is
ferrimagnetic (unequal alignment of neighboring magnetic moments).

29. Physical properties
•High melting and boiling points: Transition metal oxides have strong ionic or covalent bonds
between the metal and oxygen atoms, which require high amounts of energy to break. For
example, iron oxide (Fe2O3) has a melting point of 1565 °C and a boiling point of 2750 °C.
•High density and hardness: Transition metal oxides have closely packed crystal structures
with high atomic masses, which result in high density and hardness. For example, titanium oxide
(TiO2) has a density of 4.23 g/cm3 and a hardness of 6.5 on the Mohs scale.
•High electrical conductivity: Transition metal oxides can have metallic or semiconducting
behavior due to the presence of partially filled d orbitals that can facilitate electron transport. For
example, copper oxide (CuO) is a p-type semiconductor with an electrical conductivity of 10−5
S/cm at room temperature.
•Optical properties: Transition metal oxides can have different optical properties such as
transparency, reflectivity, absorption, emission, etc. due to the presence of partially filled d
orbitals that can interact with electromagnetic radiation. For example, zinc oxide (ZnO) is a
transparent material that can emit visible light when excited by UV light.

30. Applications
 Transition metal oxides have a wide range of applications in various fields due to their
unique physical and chemical properties.
• Optoelectronics: Transition metal oxides can be used as transparent conductors,
light-emitting diodes, photodetectors, solar cells, etc. due to their high optical
transparency, tunable band gap, and electrical conductivity.
• Sensors: Transition metal oxides can be used as gas sensors, biosensors, humidity
sensors, etc. due to their high surface area, sensitivity, selectivity, and stability.
• Magnetic storage devices: Transition metal oxides can be used as magnetic
materials, spintronics, and multiferroics due to their high magnetization, spin
polarization, and coupling between electric and magnetic properties.

31. • Light-induced catalysis: Transition metal oxides can be used as
photocatalysts for water splitting, organic synthesis, pollutant degradation,
etc. due to their ability to absorb visible light and generate reactive oxygen
species.
• Water treatment: Transition metal oxides can be used as adsorbents,
coagulants, flocculants, etc. for removing organic and inorganic contaminants
from water due to their high adsorption capacity, surface charge, and redox
activity.
• Energy conversion and storage: Transition metal oxides can be used as
electrodes for lithium-ion batteries, supercapacitors, fuel cells, etc. due to their
high specific capacity, rate capability, cycling stability, and electrocatalytic
activity.

33. Transition Metal Phosphides(TMPs)
Transition metal phosphides (TMPs) are a type of compounds that consist
of transition metals and phosphorus.
They have excellent
o mechanical strength,
o electrical conductivity, and
o chemical stability.
They are also widely used in various fields, especially as catalysts for
electrocatalytic reactions such as hydrogen evolution.
Phosphorous can adopt any oxidation state between zero and three.

34. Some of the examples,
RuP2, PdP3, and NiP3, Ni2P, Co2P, MoP, and WP, and Ni12P5, CoP, MoP2 , and WP2.
These are different types of phosphides that vary in their phosphorus-to-metal ratio
and structure.
The most frequently used elements are Fe, Co, Ni, Mo.
Classification
1. Metal rich phosphides: Ni2P
2. Mono-phosphides: WP
3. Phosphorous rich phosphides: NiP2

35.  Metal rich phosphides resemble properties of metals.
 TMP eliminates the electron delocalisation around the metal
atom due to slightly higher electronegativity of phosphorous.
 In metal rich phosphides electrons do not fully surround the
phosphorous atom ,so intensive M-M interactions can be
developed.
 Phosphorus rich phosphides do not have M-M Bonding,Most
of the phosphorus atoms can exist in the form of oligomeric
chains and clusters.
 At high temperature decompose to elemental phosphorous

39. Hydrogen Evolution Reaction(HER)
The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for
producing hydrogen gas .
The HER involves hydrogen adsorption at the electrode surface and as the adsorption
energy depends on the nature of electrode materials used so does the kinetics of HER.
Oxygen Evolution Reaction(OER)
The oxygen evolution reaction (OER) is a chemical reaction that produces molecular
oxygen (O 2) from water or other sources of protons and electrons.
Both these reactions are catalyzed by TMPs

41. Applications
Transition metal phosphides have various applications in electrocatalysis,
which is the use of catalysts to facilitate electrochemical reactions. Some
examples of electrocatalytic reactions are:
• Water splitting: the use of electricity to split water into hydrogen and
oxygen, which can be used as clean fuels or stored for later use.
• Carbon dioxide reduction: the use of electricity to reduce carbon
dioxide into useful chemicals, such as methane, methanol, formic acid,
or carbon monoxide.

42. • Nitrogen fixation: the use of electricity to convert nitrogen
into ammonia, which can be used as a fertilizer or a hydrogen carrier
• Fuel cell reactions: the use of electricity to convert fuels, such as
hydrogen, methanol, or ethanol, into electricity and water.
Transition metal phosphides are attractive electrocatalysts because
they have high activity, stability, conductivity, and abundance
compared to noble metals.
They can also be tuned by changing the metal or the phosphorus
content to optimize their performance for different reactions.

45. Transition Metal Sulfides(TMS)
Transition metal sulfides are compounds that contain one or more transition metals (such
as iron, nickel, cobalt, etc.) and sulfur.
There are many examples of transition metal sulfides, depending on the type and number of
transition metals and the ratio of sulfur atoms. Some common examples are:
• Iron sulfide (FeS): a black solid that occurs as the mineral pyrrhotite and is used in the
production of sulfuric acid.
• Cobalt sulfide (CoS): a gray-black solid that occurs as the mineral troilite and is used as a
catalyst for hydrodesulfurization.
• Nickel sulfide (NiS): a black solid that occurs as the mineral millerite and is used as a
precursor for nickel nanoparticles.
• Copper sulfide (CuS): a dark brown solid that occurs as the mineral covellite and is used as a
pigment and a semiconductor.
• Zinc sulfide (ZnS): a white or yellow solid that occurs as the minerals sphalerite and wurtzite
and is used as a phosphor and an optical material.

46. • Molybdenum sulfide (MoS2): a black solid that occurs as the mineral
molybdenite and is used as a lubricant and a catalyst for hydrogen evolution
reaction.
• Tungsten sulfide (WS2): a gray solid that occurs as the mineral tungstenite
and is used as a lubricant and a catalyst for hydrogen evolution reaction.
• Titanium sulfide (TiS2): a golden solid that is used as an electrode
material for lithium-ion batteries and sodium-ion batteries.

47.  Pyrite is a naturally occurring form of iron disulphide(FeS2)-
Fool’s Gold is one of the three largest commercial source
of elemental sulphur.
 Sphalerite(ZnS) and cinnabar(HgS) are the largest sources
of Zn and Hg,
 Molybdenite (MoS2) is the principal ore of Mo.
 Sulphide minerals are the source of world’s non ferrous
metals.

48. Synthesis

49. Exfoliation
 It is of two types:
- Mechanical
-Liquid phase
 In mechanical exfoliation bulk TMs materials with layered structures are applied as starting
materials and parts are peeled off using adhesive tape and then transferred on to target surface.
 Liquid phase exfoliation is an efficient method for exfoliating TMs in solution. Here the process
involving are sonication, stirring, grinding, shearing etc.
Ball Milling
 TMs powder particles undergo severe mechanical deformation due to collisions with stainless
steel balls and inert gas atmosphere used to protect TMs powder from oxidation.

50. Hydrothermal Method
 It is a chemical reaction in water at both high temperature and under high pressure, usually
happened in a sealed pressurized vessel.
Solvothermal
 Similar to hydrothermal method. Here organic solution applied as precursor.
Example :MoS2 nanoparticles on reduced graphene oxide sheets produced by solvothermal
reaction of (NH4)2MoS4 and hydrazine.(NH4)2MoS4 reduced to MoS2 nanoparticles and laid
uniformly on reduced graphene oxide.
Chemical vapour deposition
 Deposition of solid materials on to heated substrate from the vapour phase after several
chemical reactions.
 It is well suited to TMs thin films with high crystallinity.

51. Types
1. Based on number of sulfide atoms,
• Mono-sulfides: FeS, CoS, NiS
• Disulfides: FeS2, CoS2, NiS
• Trisulfides: FeS3, CoS3, NiS3
• Polysulfides: FeS4, CoS4, NiS4
2. Based on layers
• Layered: These are compounds that have a layered structure, where the atoms in the same layer
are connected by strong covalent bonds and adjacent layers are held together by weak van der
Waals forces.
• Non-layered: These are compounds that have a layered structure, where the atoms in the same
layer are connected by strong covalent bonds and adjacent layers are held together by weak van
der Waals forces

52. Structures
 NiAs (B8) structure: This structure contains hexagonally close-packed anions with metal atoms
occupying half of the octahedral holes. CN-6
 Pyrite (B7) structure: This structure contains cubic close-packed anions with metal atoms
occupying half of the octahedral holes and sulfur atoms forming pairs in some of the tetrahedral
holes. CN-4
 MoS2 structure: This structure consists of layers of hexagonally arranged metal and sulfur atoms,
with each metal atom sandwiched between two sulfur atoms. CN-6,CN(3)
 Rock salt (B1) structure: This structure contains cubic close-packed anions with metal atoms
occupying all of the octahedral holes. CN-6 Both

54. Applications
 Electrochemical energy storage
 Electrocatalysis
 Sensors
 Photocatalysis
 Batteries