Topic 7: Introduction to Transition Metal Complexes

Question 1

3 d-block elements that don’t always behave as transition metals and why

Answer 1

No partially filled d-subshell

Sc: electron configuration is [Ar] 3d^1 4s^2. It exists as Sc^3+: electron configuration is [Ar] 3d^0 4s^0 so behaves as an f-block element

Zn, electron configuration is [Ar] 3d^10 4s^2. It exists as Zn^2+: electron configuration is [Ar] 3d^10 4s^0

Au
electron configuration is [Xe] 4f^14 5d^10 6s^1. It exists as Au^+: electron configuration is [Xe] 4f^14 5d^10 6s^0 (not a transition metal) and Au^3+: [Xe] 4f^14 5d^8 6s^0 (is a transition metal)

Question 2

What makes a d-block element a tradition element?

Answer 2

Form stable ions with partially filled d-subshell

Question 3

Which orbital is filled first, 3d or 4s in transition metals + what are the exceptions?
Does this differ on transition complexes/compounds

Answer 3

4s as lower in energy here

Cr: [Ar] 3d^5 4s^1 (prefers to have 1 electron in each d orbital than paired in 4s) and Cu: [Ar] 3d^10 4s^1 (prefers to pair all 3d electrons over 4s)

Yes, 3d filled first as lower in energy here

Question 4

Calculate d^n

Answer 4

number of outer s + d electrons (group number)

Question 5

Requirement for colourless transition metal complexes in terms of d-electrons

Answer 5

Entirely empty or entirely full d-subshells

Question 6

Source of colour in transition metal complexes

Answer 6

d-electrons (unpaired) moving between d-orbitals and absorbing energy (light in visible region of spectrum)

Ligand –> metal / metal –> ligand charge transfer (movement of electrons)

Question 7

diamagnetic compounds contain … and are … from a magnetic field

Answer 7

only paired electrons
repelled

Question 8

paramagnetic compounds contain … and are … from a magnetic field

Answer 8

unpaired electron(s)
attracted

Question 9

Do paramagnetic or diamagnetic effects dominate?

Answer 9

paramagnetic

Question 10

u eff =

Answer 10

root (n (n + 2))
n= dumber of unpaired electrons in d-subshell

Question 11

Sc to Mn have …

Answer 11

increasing oxidation states + increased number of oxidation states

Question 12

Fn to Zn have …

Answer 12

lower oxidation states + fewer possible oxidation states

Question 13

High oxidation state complexes are … agents

Answer 13

oxidising

Question 14

Low oxidation state complexes are … agents

Answer 14

reducing

Question 15

Why is it energetically favourable to form ions from transition elements when it requires energy to remove electrons?

Answer 15

Solvation energy or lattice energy is more negative than the ionisation energy is positive.
Overall release of energy

Question 16

Why can’t all ions achieve high oxidation states e.g. Fe^+7

Answer 16

Energetically unfavourable
Solvation energy or lattice energy is less negative than the ionisation energy is positive

Question 17

dative bond

Answer 17

ligand donates pair of electrons to the central atom/ion

Question 18

Pauling’s electroneutrality principle

Answer 18

Change of an atom or ion can only be +/-1 |z|>/= 1
So any charges higher, are very attracted to that change forming a bond, charge is then spread to ligands

e.g. A metal with 2+ charge and bonded to 6 water will spread charge to Os and each will have an average charge of 1/3+. They will on average donate 1/3 of electron to 2+metal centre. This will continue to Hs, each having 1/6+ while the central metals and O will have a charge of 0

Question 19

Transition metal complexes can be …

Answer 19

acidic

Question 20

Electronegativity of … is …
The range of metals is … to …

Answer 20

1.7
50% covalent and 50% ionic character
1.4
2.0

Question 21

In higher oxidation states of the metal, bonds become more … because …

Answer 21

covalent
the ligands have to donate more electron density to the ligand to satisfy Pauling’s

Question 22

What metal charge is the most acidic?
What coordinates

Answer 22

3^+
hydroxides instead of water

Question 23

Ligands can be … such as, … such as … and occasionally … such as …
They all donate …

Answer 23

neutral
NH3 CO H2O PR3 SR2
anionic
CN^- Me^- NH2^- Cl- I-
cationic NO^+
2 electrons

Question 24

cisplatin is

Answer 24

[Pt(NH3)2(Cl)2]

Question 25

Inner sphere ligands are …

Answer 25

atoms bonded directly to central metal ions

Question 26

Outer sphere ligands are …

Answer 26

ligands associated with the inner sphere complex (outside square brackets)

Question 27

Ambidentate ligands have …

Answer 27

more than one potential donor atom that could coordinate (1 coordinates and occupies 1 coordination site)

Question 28

Bidentate and multidentate ligands

Answer 28

bidentate have 2 donor atoms that bind to the same metal at the same time (they occupy 2 coordinate site)

Same principle for more than 2 doctor atoms in multidentate

Question 29

Most complexes with 4 ligands form … complexes and others form … complexes

Answer 29

tetrahedral
square planar

Question 30

Isomers of square planar complexes

Answer 30

2 geometric isomers: cis and trans

Question 31

Isomers of octahedral complexes

Answer 31

geometric isomers: cis and trans geometric isomers: fac and mer
optical isomers (mirror image)