Chemistry of Titanium

An excellent site for finding the properties of the elements, including Titanium is at Start WebElements

For the chapter on Titanium chemistry from the Elsevier text "Chemistry of the Elements" by Greenwood and Earnshaw see On-Line Metals Based Surveys

History

The discovery of titanium in 1791 is attributed to William Gregor, a Cornish vicar and amateur chemist. He isolated an impure oxide from ilmenite (FeTiO3) by treatment with HCl and H2SO4.

Introduction

Titanium is the second most abundant transition metal on Earth (6320 ppm) and plays a vital role as a material of construction because of its:
For example, when it's alloyed with 6% aluminum and 4% vanadium, titanium has half the weight of steel and up to four times the strength.

Whilst a biological function in man is not known, it has excellent biocompatibility--that is the ability to be ignored by the human body's immune system--and an extreme resistance to corrosion. Titanium is now the metal of choice for hip and knee replacements.

Occurrence

The International Centre for Environmental and Nuclear Sciences (ICENS) has an on-going programme of mapping the geochemical content of Jamaica. 'A Geochemical Atlas of Jamaica' was published in 1995 and is available from Amazon or ICENS.
The results found for Titanium are shown below (courtesy of Prof G.C. Lalor).
ICENS Ti data
Properties of titanium

An excellent site for finding the properties of the elements, including titanium is at Start WebElements


Extraction of Titanium - the Kroll process

Wilhelm J. Kroll
Born November 24, 1889 - Died March 30, 1973
He developed the process in Luxemburg around the mid 1930's and then after moving to the USA extended it to enable the extraction of Zirconium as well.

Titanium ores, mainly rutile (TiO2) and ilmentite (FeTiO3), are treated with carbon and chlorine gas to produce titanium tetrachloride.

TiO2 + Cl2 ->TiCl4 + CO2

Fractionation
Titanium tetrachloride is purified by distillation (BP 136.4) to remove iron chloride.

Reduction
Purified titanium tetrachloride is reacted with molten magnesium under argon to produce a porous “titanium sponge”.

TiCl4 + 2Mg -> Ti + 2MgCl2

Melting
Titanium sponge is melted under argon to produce ingots.


Kroll processThe Kroll process (ISIS Draw .skc file)

Titanium Halides
Titanium(IV) Halides
Formula Colour MP BP Structure
TiF4 white -  284 fluoride bridged 
TiCl4 colourless -24 136.4 -
TiBr4 yellow  38  233.5 hcp I- but essentially monomeric cf. SnI4
TiI4 violet-black 155 377 hcp I- but essentially monomeric cf. SnI4
Preparations:

They can all be prepared by direct reaction of Ti with halogen gas (X2). All are readily hydrolysed.
They are all expected to be diamagnetic.

Titanium(III) halides
Formula Colour MP BP m (BM) Structure
TiF3 blue 950d - 1.75 -
TiCl3 violet 450d - - BiI3
TiBr3 violet - - - BiI3
TiI3 violet-black - - - -
Preparations:

They can be prepared by reduction of TiX4 with H2.

Titanium Oxides and Aqueous Chemistry

Titanium oxides
Formula Colour MP m (BM) Structure
TiO2 white  1892 diam. rutile - Refractive Index 2.61-2.90 cf. Diamond 2.42

Preparations:

obtained from hydrolysis of TiX4 or Ti(III) salts.

TiO2 reacts with acids and bases.
In Acid:
TiOSO4 formed in H2SO4 (Titanyl sulfate)
In Base:
MTiO3 metatitanates (eg Perovskite, CaTiO3 and ilmenite, FeTiO3)
M2TiO4 orthotitanates.

Peroxides are highly coloured and can be used for colourimetric analysis.
pH <1         [TiO2(OH)(H2O)x]+
pH 1-2        [(O2)Ti-O-Ti(O2)](OH) x2-x; x=1-6

[Ti(H2O)6]3+ -> [Ti(OH)(H2O)5]2+ + [H+] pK=1.4
TiO2+ + 2H+ + e- -> Ti3+ + H2O E=0.1V

Representative complexes

TiCl4 is a good Lewis acid and forms adducts on reaction with Lewis bases such as;

                2PEt3           ->      TiCl4(PEt3)2
                2MeCN           ->      TiCl4(MeCN)2
                bipy            ->      TiCl4(bipy)
Solvolysis can occur if ionisable protons are present in the ligand;
                2NH3            ->      TiCl2(NH2)2     +       2HCl
                4H2O            ->      TiO2.aq         +       4HCl
                2EtOH           ->      TiCl2(OEt)2     +       2HCl
TiCl3 has less Lewis acid strength but can form adducts also;
                3pyr            ->      TiCl3pyr3
References:

"Complexes and First-Row Transition Elements", D. Nicholls
"Basic Inorganic Chemistry", F.A. Cotton, G. Wilkinson and P.L. Gaus
"Advanced Inorganic Chemistry", F.A. Cotton, G. Wilkinson, C. A. Murillo, and M. Bochmann
"Chemistry of the Elements", Greenwood and Earnshaw

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Created and maintained by Prof. Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.

Created October 2001. Links checked and/or last modified 14th November 2007.
URL http://wwwchem.uwimona.edu.jm/courses/titanium.html