d-block

Question 1

what is the structure of a coordination compound?

Answer 1

central metal ion + shell of ligands

Question 2

what are the 4 types of ligands?

Answer 2

sigma donor, sigma acceptor, pi donor, pi acceptor

Question 3

what do sigma and pi donor/acceptor ligands consist of?

Answer 3

sigma: electron density donated/accepted from s or sp hybrid orbitals

pi: electron density donated/accepted from p orbitals only

Question 4

what is the name for a ligand that can have 2 sites that could possibly bind to the metal ion? give an example and how to determine which part of the molecule binds to the metal ion

Answer 4

ambidentate ligand
- thiocyanate

binding site depends on the identity of the metal ion (soft or hard)

Question 5

what is hapticity and denticity in coordination chemistry? + draw out the symbols

Answer 5

describes how the ligands bind to the metal center

hapticity (eta): n, number of neighbouring atoms of the same ligand that are simultaneously coordinated to the metal center

denticity (kappa): k, number of non-neighbouring atoms of the same ligand that are coordinated to the metal ion

Question 6

what is the equation for the formation constant?

Answer 6

k = [concentration for each product] / [concentration for each reactant]

Question 7

what is the overall formation constant equation?

Answer 7

beta = multiplying all the equilibrium constants for each ligand added

or [MLn] / [M] x [L]^n

or logbetan = logK1 + logK2… + logKn

Question 8

why would a K value for adding a ligand suddenly increase again?

Answer 8

change in geometry can stabilize the coordination compound making the addition of a ligand more favourable

Question 9

what does it mean if logK is reaching 0

Answer 9

that means K is reaching 1 which is close to equilibrium

Question 10

what is the trend with increasing the no. of ligands on metal ion?

Answer 10

decrease in logK (progressively in favour of reactants) because of steric or electronic (repulsion) reasons

Question 11

what is the relationship between ion size and stability of the complexes it forms? and why? - for s,p,f block

Answer 11

stability decreases as size of ion increases because of less effective nuclear charge and weaker metal ligand bonding

Question 12

how does the HSAB principle relate to metal complexes? why is the opposite not favoured?

Answer 12

hard ligands form more stable bases with hard cations (same with soft)

hard-soft combinations are not favoured as there is not enough energy to overcome the high solvation energy of a hard species

Question 13

define hard/soft acids/bases

Answer 13

hard acid: small monocations (highly charged) Ti4+

soft acids: less electropositive metals that are more polarisable (low charge to radius ratio)

hard bases: small, non polarizable donor atoms (NOF)

soft bases: larger relatively polarisable donor atoms (PSI)

Question 14

why are polydentate ligands in general more stable than monodentate ligands?

Answer 14

1. polydentate ligand is less likely to be displaced than monodentate ligands
2. chelation + sterics prevents attack from other ligands
3. entropy is higher if you replace monodentate with polydentate ligands thus favourable (IMPORTANT POINT) -> entropic drive
   -> positive s is favoured = more stable complex

Question 15

what are the 2 types of coordination in tridentate ligands and how are they coordinated?

Answer 15

meridional (mer-): through the metal ligand

facial (fac-): not through the metal ligand -> looks like a face

Question 16

what are the coordination modes for tetradentates?

Answer 16

cisalpha, cisbeta, trans

Question 17

what are the 3 types of tetradentate ligands

Answer 17

open chain (unbranched), tripodal (branched), macrocyclic

Question 18

what are famous molecules for pentadentate and hexadentate coordination? what are its applications?

Answer 18

EDTA 3-
EDTA 4-

descale boilers (clean corrosion deposits)
treatment of Hg and Pb poisoning + removing excess iron from the body

Question 19

what is the effect of Hg and Pb poisoning on the body?

Answer 19

displace sulfur in amino acids and also displace Zn which is important for muscle contraction

Question 20

what are some of the functions of macrocyclic ligands? + how are they named?

Answer 20

no. of total atoms in cycle-crown - no. of hetero atom

uses: haemoglobin (2 anionic and 2 neutral nitrogens in the porphyrin compound coordinating with the iron), vitamin B12 (cobalt) -> formation of RBC and function of brain and CNS

Question 21

what is the trend d orbital stability down a group?

Answer 21

increasing stability (due to less experienced nuclear charge) therefore preference towards filling d orbitals

Question 22

what is the equation for d occupancy?

Answer 22

group number - oxidation state

Question 23

what is the trend in oxidation stats down the group?

Answer 23

higher oxidation states become more common due to lower effective nuclear change meaning that ionization energies are much lower as the atom size gets bigger

Question 24

what is the kepert model for coordination geometry?

Answer 24

lone pairs are ignored and only considers repulsion between groups/ligands

no. of d electrons does not effect the shape of the metal complex

Question 25

what are association and dissociation reactions? what is its reversibility?

Answer 25

association is irreversible: adding ligands to product a new geometry (eg. square planar to octahedral) dissociation is reversible: taking away ligands but depends on the strength the ligands bind to the metal ion

Question 26

why do metals such as copper, silver and gold have lower coordination numbers to ligands?

Answer 26

they already have a lot of electrons so do not need to bind to ligands for electron donation

Question 27

what are the 2 coordination geometries for 5 ligands and what are the energy differences between them?

Answer 27

trigonalbipyramidal and square based pyramid which have a very small energy difference thus can interconvert

Question 28

why is the only 1 signal for trigonal bipyramidal?

Answer 28

fluxionality of axial and equatorial ligands makes them indistinguishable (rapid interchange same NMR spec)

Question 29

what are the 2 geometries for 6 coordination metal complexes?

Answer 29

octahedral and trigonal prismatic

Question 30

what are the 2 reasons for distortion of the perfect octahedral shape complex

Answer 30

different ligands, jahn-teller effect (electronic related)

Question 31

what are inner and outer sphere complexes?

Answer 31

inner: anion as a ligand directly bound to the metal centre (primary coordination sphere) outer: counterion esque, bound to the positive metal complex electrostatically

Question 32

what is nuclearity?

Answer 32

how many metal complexes is the ligand bound to (eg. ligand bridging) or metal-metal bond mononuclear, dinculear, trinuclear -> polynuclear

Question 33

what are polynuclear complexes?

Answer 33

multiple metal centers within a complex

Question 34

what is the sequence of naming a metal complex

Answer 34

[ metal ion, ligands in alphabetical order]oxidation state of metal complex counter ion - if there is a hydride it comes first - if there are things within the square brackets that need brackets {} are used instead -for neutral atoms the donor atom would be the closest to the metal ligand (eg. OH2 rather than H2O)

Question 35

what is the naming system for no. of ligands in a complex

Answer 35

within a ligand: di, tri, tetra.. no. of that ligand in a metal complex (if the ligand itself contains a di,tri,tetra): bis, tris, tetrakis, pentakis if there is a numerical value associated with the ligand (eg. methyl), then the other form is included

Question 36

what is the suffix for anionic complexes?

Answer 36

ligand metal name -ate

Question 37

what are the 2 numbers that you can write after naming the metal complex?

Answer 37

1. oxidation state of the metal ion 2. overall charge of the metal complex (metal oxidation state - total charge from ligands)

Question 38

what are the 2 types of isomers in coordination chemistry?

Answer 38

constitutional isomers: same empirical formula but different atom connectivity stereoisomers: same connectivity but individual atoms are arranged differently in space

Question 39

what are linkage isomers and how can you interchange between them?

Answer 39

the metal complexes that form when the same ligand uses a different atom to coordinate with the metal complex change them photochemically or with heat (has colour changes)

Question 40

what are inner sphere outer sphere isomers called?

Answer 40

ionisation isomerism (switch between the counterion and a ligand) or hydrate isomerism (which includes water)

Question 41

what is coordination isomerism?

Answer 41

ligands that have the same empirical formula but the metal centers are switched (or switching of ligands between metal ions) -> can also have some ligands switch between ions to change its oxidation state check L10 S64 for examples

Question 42

what is an example of geometric isomerism?

Answer 42

1. cis and trans organisation of ligands in a sqaure planar metal complex 2. if the ligands are being detattched from equatorial to axial etc. arises from detaching ligands and reattaching them in a different way the angle between a certain set of ligands changes due to detachment

Question 43

what is ligand isomerism?

Answer 43

ligands in different isomeric forms (different connectivity within the ligand itself but should not effect bonding to metal ion)

Question 43

what is conformational isomerism and what is an example?

Answer 43

more than one known stereochemistry for a coordination number (eg. trigonal bipyramidal and square planar for 5 coordinate OR square planar and tetrahedral for 4 coordinate)

Question 43

what are the requirements for optical isomerism

Answer 43

chirality but doesn't have to be all different substituents mirrored non-superimposable images

Question 44

what is polymerisation isomerism?

Answer 44

same molecular formula but they 2 metal ligands can join together to create a different molecular weight metal complex