Six topics with the average lecture time indicated in brackets.
Wave Mechanics and Spectroscopy(12) - Bourne
Inorganic bonding(10) -Egan
Introduction to liquids(10)-Venter
Crystal structure analysis(9)-Oliver
Inorganic Reaction Mechanism(8)-Jackson
Inorganic complex equilibra (8)-Jackson
D electrons : 3d^x-z ,x= group number z= charge TrendsIonization energy-increases from left to right , the changes are small due atomic size decrease from left to right.=D oribtals are furtheraway from the nuclues,(less effective nuclear pull) and thus are more effectively shielded than s and p oribtals.Ionic radii Innic size depends on charge of ion and magnetic propertise.M(2+) is >>M(3+)
Ligand-Base-A pair of electron donor
Metal-Acid-A pair f elctron acceptor
Lewis bases-Bronsted-Lowery bases
Not all lewis bases are sig. Bronsted-Lowery
Exception;CO,CN even though they are organic moclues which have relatively high pka they form coordinative complexes
Metal-ligand=Lewis Acid-Lewis base
Ligand-A proton acceptor
Metal-A proton donor
Exceptions Cl,Br,I and CO not sig.bronsted lowey bases but for complexes.
Metal-ligand=Lewis Acid-Lewis base
A Electrostatic model
uses ligands to create a electric field around the metal centre
Ligands are treated as negative point charges which are attracted to postive charged metal.
The ligand electrons and metal electrons repel one another.
There is no metal-ligand covalent interaction
What do we use this theory for?
Colour-which is due the presence of d--d transtions in electronic spectra of complexes.
Magnetic propertise of complexes
High spin/Low spin---Metals with the same d count can give complexes with different number of unpaireed electrons.
since CFT-ignores covalent interaction,one must take into account in advanced ligand filed theory (Jackson)
Since the distribution of ligands around the metal is not spherically symmetrical ,there are electrons which are more stable than others.
Those which point along the dx2y2 and dz2 are less stable than those in the dxy,dxz,dyz.
Thus if it were spherical the energies of 5 oribtals would be risen (destablized by the same amount) however this is not the case.
Replusion of electrons from 6 ligands spilt the d complex into:
1.doubly degenerate (eg)
2.Triple degenerate (t2g)
Octahedreal and square planar complexes are centrosymmetric while tetragonal and teterahedral are not.
1.-dz2 and dx2-dy2 have subscript g =gerade=even
if they have n centre of iversion=ungendree=uneven
The energy seperation between the energy levels is delta oct
An electron in one of this oribtals is stablized by 2/5 delta oct called ligand field stabalization energy(LFSE)
CFSE- a measure of the net energy of occupation of the d oribtals realitive to the mean energy
Formula: CFSE=-(0.4X+0.6Y)delta oct
The reason we see colour is because of the delat oct value which carries the right energy to oxlate electrons from t2g-eg levels .
The E of the visible peak max corresponds to delta oct.
If the lower t2g levels are filled and the upper eg levels are vacant or partially vacant .
you have a energy jump from the lower level to the higher level =d-d transitions.
colour dependency is on the the change of energy-change of wavelength.
must have a spin state change from (+0.5-0.5)
Caption: : see worked example
Worked example - Page 23
Answerif wavelength=493nm the v=1/493=20283.97cm^-1thenhv=delta oct =20284cm^-1 convert to kj.mol^-1 =243.4kj.mol^-1
Variations in the Crystal splitting Field
Nature of the ligand Small degree of splitting- small delta value-weak ligand.Large degree of splitting-large delta value-strong ligand .
Weak ligands-LHS and vice versa
For a ligand colour depends on the oxidation state of metal.For a given metal colour depends on the ligandWeaker field-smaller delta-longer wavelength and vice versa
Oxidation state of metal Delta values increase with oxidation state of the metal ion for a given metal and given ligand.For a given metal and given ligand delta oct increases down the group .Remember high oxidation state-Smaller ion , Shorter M-L bond.Mn(2)NB Delta Oct /tet=determined by strength of crystal field.THE AMOUNT OF CRYSTAL SPILITING IS DETERMINED BY STRENGTH OF THE LIGAND
if delta oct(spilting of d oribtals)
Forumla for HS: CFSE=nt2g*-0.4delta oct +(ng*0.6)deltaoct
LS:CFSE:nt2g*-.04delta oct +neg*0.6delta oct
LS-STRONG FIELD LIGAND ,HS-weak field ligand(Given metal,Given ligand) and it is metal dependant
How do we show we have HS/LS?
vIa magnetic measurements using magnetic susceotibility .Achieved through spin-only magnetic momentfancy u=(n(n+2))^1/2 fancy ub