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Chemistry Of The Elements > d-block > Flashcards

d-block Flashcards

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1
Q

what is the structure of a coordination compound?

A

central metal ion + shell of ligands

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2
Q

what are the 4 types of ligands?

A

sigma donor, sigma acceptor, pi donor, pi acceptor

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3
Q

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

A

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

pi: electron density donated/accepted from p orbitals only

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4
Q

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

A

ambidentate ligand
- thiocyanate

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

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5
Q

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

A

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

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6
Q

what is the equation for the formation constant?

A

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

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7
Q

what is the overall formation constant equation?

A

beta = multiplying all the equilibrium constants for each ligand added

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

or logbetan = logK1 + logK2… + logKn

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8
Q

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

A

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

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9
Q

what does it mean if logK is reaching 0

A

that means K is reaching 1 which is close to equilibrium

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10
Q

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

A

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

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11
Q

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

A

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

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12
Q

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

A

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

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13
Q

define hard/soft acids/bases

A

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)

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14
Q

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

A
  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
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15
Q

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

A

meridional (mer-): through the metal ligand

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

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16
Q

what are the coordination modes for tetradentates?

A

cisalpha, cisbeta, trans

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17
Q

what are the 3 types of tetradentate ligands

A

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

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18
Q

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

A

EDTA 3-
EDTA 4-

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

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19
Q

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

A

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

20
Q

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

A

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

21
Q

what is the trend d orbital stability down a group?

A

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

22
Q

what is the equation for d occupancy?

A

group number - oxidation state

23
Q

what is the trend in oxidation stats down the group?

A

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

24
Q

what is the kepert model for coordination geometry?

A

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

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

25
Q

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

A

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

26
Q

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

A

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

27
Q

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

A

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

28
Q

why is the only 1 signal for trigonal bipyramidal?

A

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

29
Q

what are the 2 geometries for 6 coordination metal complexes?

A

octahedral and trigonal prismatic

30
Q

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

A

different ligands, jahn-teller effect (electronic related)

31
Q

what are inner and outer sphere complexes?

A

inner: anion as a ligand directly bound to the metal centre (primary coordination sphere)

outer: counterion esque, bound to the positive metal complex electrostatically

32
Q

what is nuclearity?

A

how many metal complexes is the ligand bound to (eg. ligand bridging)

or metal-metal bond

mononuclear, dinculear, trinuclear -> polynuclear

33
Q

what are polynuclear complexes?

A

multiple metal centers within a complex

34
Q

what is the sequence of naming a metal complex

A

[ 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)
35
Q

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

A

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

36
Q

what is the suffix for anionic complexes?

A

ligand metal name -ate

37
Q

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

A
  1. oxidation state of the metal ion
  2. overall charge of the metal complex (metal oxidation state - total charge from ligands)
38
Q

what are the 2 types of isomers in coordination chemistry?

A

constitutional isomers: same empirical formula but different atom connectivity

stereoisomers: same connectivity but individual atoms are arranged differently in space

39
Q

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

A

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)

40
Q

what are inner sphere outer sphere isomers called?

A

ionisation isomerism (switch between the counterion and a ligand)

or hydrate isomerism (which includes water)

41
Q

what is coordination isomerism?

A

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

42
Q

what is an example of geometric isomerism?

A
  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

43
Q

what is ligand isomerism?

A

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

43
Q

what is conformational isomerism and what is an example?

A

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)

43
Q

what are the requirements for optical isomerism

A

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

44
Q

what is polymerisation isomerism?

A

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

Chemistry Of The Elements (7 decks)

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