Metal-Ligand Bonding Flashcards
What is the Electropositive trend of the transition metals?
Electropositivity increases from right to left and down a group
What is hapticity η?
The number of contiguous atoms of a ligand attached to a metal
What is denticity κ?
The number of non-contiguous atoms coordinating from a ligand (often a. chelating ligand)
What is µ?
Number of metal atoms bridged by a ligand
How do you find the oxidation state?
Oxidation state = Charge on the complex - Sum of the charges of the ligands
What charge does a linear NO ligand have and how many electrons does it donate?
+1 (NO+)
donates 3 electrons
What charge does bent NO ligand have and how many electrons does it donate?
-1 (NO-)
Donates 1 electron
How can you work out the ligand charge?
Determine how many H+ to add until the molecule is neutral
What is the electroneutrality principle?
The formal charge is not the actual charge distribution. No atom will have an actual charge greater than + or - 1
How do you find the d-electron count?
d-electron count = group number - oxidation state
How do you find the Total Valence Electron Count (TVEC)?
TVEC = d-electron count + electrons donated by ligands
What is the ionic formalism?
M-L -> M+ + L-
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What is the trend of coordination numbers for early groups in transition metals?
In general, coordination numbers are greater for earlier TM groups (4-7). Coordination numbers for lanthanides are generally greater than TMs
What area the steric limit for number of ligands on transition metals and lanthanides?
TM - 6 ligands
Lanthanides - 9 Ligands
What are the 3 requirements of the orbitals for a bond to form?
1) Must have appropriate symmetry
2) Must overlap
3) Must be similar energy
What is a sigma donor?
Has a lone pair of electrons to donate to the metal
What is a Sigma donor, Pi acceptor?
Has lone pair to donate to met, aswell as another empty orbital to accept electron density from metal
What is a sigma donor, pi donor?
Has multiple lone pairs to donate to the metal
How can you find the ordering of the d-orbitals?
Crystal Field Theory
What orbitals are the bonding to a metal determined by?
HOMO/LUMO
What does the greater electronegativity around a carbon atom in CO do for the bonding and why?
Creates better overlap for the sigma donation via carbon atom to happen
What can occupying the antibonding orbitals do to the bond?
Break the bond
How can you decide whether the NO is bent or linear?
Work out the TVEC of the complex without the NO, and see if you need to add 3 (linear) or 1 (bent) electron to make the TVEC upto 18
What is required for a pi donor interaction in terms of orbitals?
empty d orbitals
Why don’t pi donor systems always obey the 18 electron rule?
The pi donor ligands and the t2g orbitals are now pi antibonding and is therefore less energrtically favourible to fill them
What is the spectrochemical series?
A list of ligands in order of increasing field strength.
What are examples of pi-acceptor ligands in order of increasing field strength?
CO > CN- > PPh3
What are examples of sigma-only ligands in order of increasing field strength?
NH3 > H2O > OH- > F-
What are examples of pi-donor ligands in order of increasing field strength?
Cl- > S2- > Br- > I-
Put these in order of increasing field strength:
pi-acceptors
sigma only
pi-donors
pi-acceptor > sigma only > pi-donors
why is the eg to eg transfer in an octahedral field a large change in bomd lentgh? and how does this effect speed ov electron transfer and overlap?
In an Oh field eg is sigma star
less overlap
slower speed of electron transfer
why is the t2g to t2g transfer in an octahedral field a small change in bond length? and how does this effect speed of electron transfer and overlap?
t2g in an octahedral is pi/pi star/ non bonding
faster elcetron transfer
more overlap
how does large bond length change effect speed of reaction?
slows reaction with larger bond length change
In an electron transfer do you relax the bomd first or transfer the elctron first?
relax the bonds and then transfer the electrons
why not transfer electron and then relax bonds? and what could be used to make it happen?
you cannot just spontaneously transfer electrons as it violates the conservation of energy
a photon could be used for vertical transition
what is delta r?
Metal - Ligand bond length difference between the oxidant and reductant
how do you find the delta G from a delta r diagram
the distance between the starting delta r and the intersection pf the 2 parabolas
What does the intersection of 2 parabolas in a reaction coordinat transition state diagram show?
the requirement of equal orbital energies is met, and this allows the possibility of electron transfer
hiw can you determine the probability of a reaction?
draw the 2 parabolas but without the intersectuon (looksmlike a normal reaction coordinate) and the size of the gap (delta Ec) determines probability (larger the more probable)
in the normal region what is ghe relation between activation energy (delta G dagger) and driving force (delta G o)?
delta G dagger is proportional to 1/delta G o squared
what is the relation between delta G dagger (activation energy) and delta r?
delta G dagger proportional to delta r squared
bigger changes im bind lengths equals bigger delta G ( activation energy) so slower reaction
are reactions fast or slow if they have simmilar bond lengths?
fast
go over the equation on page 57
lololololol
rate gets slower if activation energy increases
learn the activation enrrgy and lander rules (there is 3)
trollolololol
how does rate (k) relate to thermodynamic driving force (delta G o) in the inverted region?
rate (k) decreases as the thermodynamic driving force increases (inverted region)
