week 11

Question 1

What does diamagnetic mean?

Answer 1

a substance that contains no unpaired electrons and, thus, is not attracted to a magnetic field

Question 2

What is an effective magnetic moment?

Answer 2

the magnitude of paramagnetism expressed by a substance

Question 3

What is a Guoy balance?

Answer 3

a device used to measure the magnetic properties of a sample

Question 4

What is Δoct a measure of?

Answer 4

It is a measure of the electrostatic repulsion between the d-electrons of the metal and the ‘point charge’ ligands

Question 5

Ligands that cause large Δoct ar called what?

Answer 5

Strong field ligands

Question 6

True or False: The size of Δoct affects which orbitals are occupied

Answer 6

True - Δoct determines whether a high- or low-spin configuration is more likely

Question 7

Ions with how many d-electrons have a low-spin configuration?

Answer 7

4-7 d-electrons

Question 8

Why do strong-field ligands have a larger splitting energy?

Answer 8

They bind to the metal ion more strongly increasing the amount of ligand-electron repulsion. This means that they are more likely to exist in a low-spin configuration

Question 9

Which configuration are weak-field ligands likely to exist in?

Answer 9

High-spin

Question 10

What determines the colour of metal complexes?

Answer 10

The colour a complex appears is the complementary colour to the one that it absorbs (i.e. absorbs red, looks green). It is the energy difference between the two non-equivalent orbital sets

Question 11

Which d-orbitals are included in the eg orbital?

Answer 11

dx^2-y^2 and dz^2

Question 12

dxy, dxz, and dyz make up which overall orbital when the d-orbitals are non-degenerate?

Answer 12

t2g

Question 13

What do we use to measure the effective magnetic moment of a substance?

Answer 13

Guoy balance

Question 14

How do we calculate the spin-only magnetic moment?

Answer 14

√n(n+2)

n = number of unpaired electrons

Question 15

True or False: In general, a larger ∆ indicates that lower energy photons are absorbed

Answer 15

False - a larger ∆ indicates that higher energy photons are absorbed, and the solution appears further to the right on the EM spectrum

Question 16

strong field ligands

properties +example

Answer 16

strong field ligands generally bind to the metal ion more strongly and therefore cause greater ligand to metal electron repulsion, causing Δoct to be large and leading to the complex having fewer unpaired electrons and being “low spin”. An example of this is the cyanide ligand (CN-).

Question 17

weak field ligands

properties+example

Answer 17

weak field ligands bind weakly to the metal centre, create less ligand to metal electronic repulsion, and thus cause smaller splittings between d orbitals.

This leads to smaller values Δoct, more unpaired electrons and “high spin” electronic states. An example of this is the chloride ion (Cl-).

Question 18

To use the colour wheel, you first need to

Answer 18

know the wavelength of light which is being absorbed (λmax). The colour observed is then the colour on the opposite side of the wheel. For example, if green light is absorbed (e.g. λmax = 520 nm) then the complex will appear red.

Question 19

what is the orgin of colour in trasitntion metal complexes

Answer 19

The splitting of d-orbitals into different energies due to the arrangement of ligands around a metal ion, as described by crystal field theory, leads to d-orbitals of different energies

f an electron in a lower energy d-orbital absorbs sufficient energy, it can move into a higher energy d-orbital
This energy can be provided by light,

Question 20

what is delta oct

Answer 20

The energy of the photon the electron needs to absorb is that of the energy gap between the t2g and eg orbitals - i.e. Δoct.

Question 21

how to claucte the enegry a e- needs to jump obritals

Answer 21

The energy is in turn related to the frequency (ν) or the wavelength (λ) of the light as follows:

Δ Eelectron = Ephoton (delta oct) = h𝜈 = hc/𝜆

where h = Planck’s constant (6.626 x 10-34 J.s) and c = the speed of light (3 x 108 m.s-1). In the case of [Ti(OH2)6]3+, the energy required corresponds to a max of ~ 490 nm,

Question 22

The colours of metal complexes are related to the energy gaps between the non-degenerate d-orbitals

These will lead to

Answer 22

These will lead to large energy splittings (e.g. large Δoct),
meaning electrons will need to absorb a relatively large amount of energy to make the d-d transition.
this leads to absorption of light at lower wavelengths.

Conversely,
ligands that interact weakly with the metal d-orbitals (weak field ligands) will lead to smaller splittings (e.g. small Δoct), meaning electrons need to absorb smaller energy packets to make the d-d transition (i.e. light at higher wavelengths).

E = h𝝂 or E=hc/𝝀

Question 23

if all obrtials fully filled

Answer 23

no light absobed no e- jump no colour

Question 23

what affects size of CFSE

Answer 23

OX STATE higher = larger splitting lowver = smaller splitting ligands strong felid = bind to metal strongly = larger splitting energy = great ligand electron repulsion= low spin weak feild bind to metal weakly = smaller splitting energy = less e- ligand replusion = high spin

Question 23

left had side of spectrochemical series

Answer 23

weak field ligands weak binding smaller delta oct transtion at longer wavlength max EG Cl- F- oh-

Question 24

right hand side of the spectrochemical series

Answer 24

strong feild ligands strong binding larger delta oct tanstion at shorter wavemax eg CO CN- en NH3

Question 25

Large values of Δoct will result in.. (talking about pairing)

Answer 25

maximum amount of pairing of electrons before filling eg orbitals; this is the low spin configuration.

Question 26

small values of Δoct will give

Answer 26

spin configurations - single electrons are placed in every orbital first, before pairing up any remaining electrons

Question 28

calc spin only mag moment

Answer 28

uso = sqrt(n(n+2) n= no. of total unpair electron depends if high or low spin