For Catalysis Flashcards
Which types of d orbitals are often low spin and so are likely to be soft?
4d and 5d
What ligands must Ni have to be square planar? What shape is it with the other type?
Strong field ligands, tetrahedral with weak field
What field strength is Cl as a ligand?
Weak field = pi-donor
What field strength is PPh3 as a ligand?
Weak field
What are the isomers for square planar always?
Cis and trans
What is a high spin orbital?
Half filled with e-
What are the isomers for a metal of 2 ligands with 3 of each?
Fac and mer
How is a mer isomer positioned?
180deg between the two ligands furthest away from each other (similar to trans)
How is fac isomer positioned?
All of the ligands of the same type are on the same face (similar to cis)
What are the isomers for a metal with 2 of one ligand and 4 of another ligand?
Cis and trans
What is the en ligand?
BIDENTATE
What is the difference between enantiomers and isomers?
Enantiomers = optical with the different shaped bonds
Isomers = position of atoms
Eq for metal oxidation state?
Overall charge on the complex - total formal charge on the ligands
What makes a ligand soft?
Large ionic radii as they’re further down the periodic table and less electronegative
What makes a ligand hard?
Very electronegative and 3d
Are hard-soft or hard-hard/soft-soft interactions favoured?
Two of the same
When are e- paired vs promoted?
Paired = large deltaOct
Promoted = small deltaOct
What makes deltaOct small?
Weak field ligands
What makes deltaOct big?
Strong field ligands
What is the orbital distortion for d1?
dxy and dx^2-y^2 move down in energy and the electron goes in dxy
Compression
What is the orbital distortion for d3?
No distortion bc all 3e- are at the same energy level anyway
What is the distortion for high spin d5?
No distortion bc high spin so all orbitals are half filled
What is the distortion for low spin d7?
Compression
dz^2 and dx^2-y^2 go down,
What is the distortion for high spin d7?
Elongation
dz^2 goes down and dxy goes up
What field type is H2O ligand?
Weak field
What is the distortion for d8?
No distortion bc pairing so e- paired at the bottom
What colour is high spin d5 and why?
Colourless bc all d-orbitals are filled with an unpaired e-
Colour is disallowed if the spin of an e- would need to be changed upon promotion
When is a complex diamagnetic?
All e- are paired - the spins cancel out so no magnetism
What colour is d0?
Colourless bc no e- to promote and so no d<->d transitions
What makes something paramagnetic?
Unpaired e- so complex has colour bc d<->d transition can occur upon promotion
What makes something high spin?
Weak field ligand
What shape does d3 favour?
Octahedral
What arrangement are Pd(II) complexes nearly always?
Square planar
What gives something a higher pKa?
1) More neutral ligands (e.g. CO) to stabilise the negative charge when a proton leaves and the most stable conjugate base gives a stronger acid
2) A more protic/electronegative metal so the proton is removed more readily
3) If the COMPLEX is negatively charged as it will be unfavourable for it to become more negatively charged by removal of a proton, so the eqm will lie towards this species (acidic)
Why do tetrahedral Ni complexes appear blue?
Bc deltaTet is small so the adsorption bands are in the red region of the UV spectrum
Are there any isomers for MA2B2 complexes?
No
What does a large deltaOct mean?
Small p = paired e- (low spin)
What does small deltaOct mean?
P is big so high spin (promoted e-)
What is elongation?
z components to down in energy
x and y components go up in energy
What is compression?
z components go up in energy
x and y components go down in energy
spin only formula
S = ¬n(n+2)
where n = no. of unpaired e-
S = total unpaired e- spin
what are reduction and oxidation in terms of e-
reduction = addition of e-
oxidation = removal of e-
how do pi donors and acceptors affect the value for deltaOct?
pi acceptor = increases deltaOct
pi donor = decreases deltaOCt
how do hard/soft ligands affect deltaOct?
hard = increases deltaOct
soft = decreases deltaOCt
why are d4, high spin d6, and d9 complexes dissociative?
bc they have longer axial bonds which means that the ligands in the dissociative positions dissociate/ are more readily displaced
what mechanism is given by negative entropy (S)?
associative
