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in electric field:

induced d. moment µ*= α E E – electric filed intensity (strength) α – polarisability (C2m2J-1)

polarisable volume (m3)

Induced dipole moment, polarisability

Also polar molecules can be additionally polarised 2

Van der Waals forces

Intermolecular forces other than covalent bonds or other than electrostatic interactions of ions

Johannes van der Waals Dutch, 1837-1923 Nobel Prize-1910, Physics

interactions: Electrostatic: ion-ion; ion-dipole

vdW: dipole-dipole dipole-induced dipole

induced dipole-induced dipole + higher multipoles

Energy ~ 100 – 101 kJ/mol

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Hydrogen bond:

atractive interaction of a (bond) hydrogen atom with an electronegative atom (N, O, F) of a different bond

- stronger than v. d. Waals - weaker than a covalent or ionic - directional

electronegative atom donates an lone pair

Bond energy: ~ 101 – 1.5x102 kJ/mol

δ+ δ-

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Intermolecular hydrogen bond:

Intramolecular hydrogen bond:

Dimers of carboxylic acids

acetylacetone

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Typical energies and lengths of hydrogen bonds:

F—H...:F 155 kJ/mol (40 kcal/mol)

O—H...:N 29 kJ/mol (6.9 kcal/mol)

O—H...:O 21 kJ/mol (5.0 kcal/mol)

N—H...:N 13 kJ/mol (3.1 kcal/mol)

N—H...:O 8 kJ/mol (1.9 kcal/mol)

Pola

rizá

cia

X–H

X—H...........Y

~110 ~160-200 length/pm

h. bond donor h. bond acceptor

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σ-hole bond :

counter-intuitive bond, energies similar as for H-onds

-

+

σ-hole

With elements of 14-18 groups

Halogen bond

σ-hole bonding

- X Gr. 17 -halogen bond (F, Cl, Br, I)

= E Gr. 16 - chalcogen bond (S, Se, Te)

≡ Pn Gr. 15 - pnictogen bond (P, As, Sb)

- T Gr. 14 - tetrel bond (Si, Ge, Sn)

- A Gr. 18 – aerogen bond (Kr, Xe)

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σ-hole – dictates the bond direction

AsCl3 -150 kJ/mol

.

0.05264

-­0.0107

0.00197

SbCl3…hexamethylbenzene ∆E -57 kJ/mol

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complex: used by chemists for compounds that consist of (several) other compounds that can exist separately

Coordination compounds (complex)

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ligands

central atom

coordination sphere (inner)

acceptor

donor

Lewis base

Lewis acid

No. of donors exceeds the

value of oxidation number

usually (poly-nuclear) ions + counterions

Coordination compounds (complex)

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Some of further basic concepts

Coordination number: number of donor atoms coordinated in the inner sphere

Ligands: monodentate – a single donor atom (H2O, CN-, F- … )

polydentate – their geometry enables to occupy (bi-, tri- ...) more than a single coordination position several donor atoms (chelate agents) (e.g. ethylendiamin H2N-CH2-CH2-NH2)

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chelate complexes

Ethylendiamin (en)

EDTA

bridging ligands

Ethylendiamintetraacetate(4-)

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Coordination compounds: bonds/structure

Alfred Werner, Swiss, 1866-1919, Nobel Prize 1913

Showed that transition metals create complexes with square, tertrahedral, octahedral structure

e.g. cis-[PtCl2(NH3)2] trans-[PtCl2(NH3)2] diammin-dichloridoplatinum(II) complex

geometrical isomers

cis-

trans-

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Typical space structures of complexes

Trigonálny dodekaéder Trojnásobne zastrešená

trigonálna prizma

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Geometrical isomerism for octahedral structures

cis- trans- mer- fac-

Info: Optical isomerism: mirror image – enatiomers

chirality, chiral molecules 16

Valence bond theory with hybrid AO in most cases enables explanation of the structure

coord. No. form of coord. sphere examples 2 – SP linear [CuCl2]- [Ag(S2O3)2]3-

4 – SP3 [Co(NCS)4]2- [NiCl4]2- D3S tetrahedron [BF3(NH3)]

4 – DSP2 [Mn(H2O)4]2+ [PdCl4]2- SP2D square [Pd(NH3)4] 2+ Ni(CN)4]2-

6 – D2SP3 [Fe(H2O)6]2+ SP3D2 octahedron [Fe(CN)6]3- [FeF6]3- [PdCl6]2-

Coordination compounds: bonds/structure

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paramagnetic [NiCl4]2- unpaired electrons

Ni(II) -[NiCl4]2–

Ni2+

sp3

17

28Ni 3d 4s 4p

High-spin complex

diamagnetic [Ni(CN)4]2- paired electrons

Ni(II) -[Ni(CN)4]2–

Ni 3d 4s 4p

Ni2+

dsp2

18

Ni2+ valence

Low-spin complex

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metal-ligand bond is weaker than „usual“ covalent b.

??????

Some complexes use inner „d“ orbitals others use outer „d“ orbitals

Transition metal complexes use to be intensively colored

MO theory

simplified approximations

Coordination compounds: bonds/structure

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Crystal field theory Central atom in electrostatic field

of (ionic) ligands (as point charges) (electrostatic theory of ligand field)

Splitting of „d“ levels: octahedral complex

d

Ene

rgy Δ

Ligand field

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Why the transition metal complexes are colored?

d-d transitions

eg

t2g

splitting of „d“ levels: tetrahedral complex

d

Ene

rgy Δ

t2

e

Ene

rgy

octahedral

complex is violet

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low and high-spin complexes [Fe(CN)6]3- [FeF6]3-

Fe3+

[Fe(CN)6]3-

5d Fe0

4s

Δ

[FeF6]3-

Ene

rgy

Δ

t2g

eg

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Relative ligand field strengths

High-spin complexes Low-spin complexes

Spectrochemical series