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Geometry of Molecules & Ions T- 1-855-694-8886 Email- [email protected] By iTutor.com

Geometry of Molecules & Ions

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Page 1: Geometry of Molecules & Ions

Geometry of Molecules & Ions T- 1-855-694-8886

Email- [email protected]

By iTutor.com

Page 2: Geometry of Molecules & Ions

Complexes

A central metal atom bonded to a group of molecules or ions is a metal complex.If the complex bears a charge, it is a complex ion.Compounds containing complexes are coordination compounds.

Page 3: Geometry of Molecules & Ions

The molecules or ions coordinating to the metal are the ligands.They are usually anions or polar molecules.

Complexes

Page 4: Geometry of Molecules & Ions

Structure & isomerization

Three categories of isomerization1. Structural isomers: atoms connected in

different ways1. Coordination isomers2. Linkage isomers

2. Geometric isomers: ligands have different spatial arrangement1. Cis-trans isomers2. Octahedral complex isomers

3. Optical isomers: nonsuperimposable mirror-images (enantiomers)

Page 5: Geometry of Molecules & Ions

Structural isomerism: coordination isomers

Coordination isomersCoordination ligand exchanges places w/uncoordinated counter-ion

Ex: [Co(NH3)5Br]Cl vs. [Co(NH3)5Cl]Br

Page 6: Geometry of Molecules & Ions

Structural isomerism: linkage isomers

Either one of atoms in NO2- can bond to

metalWhen O, nitrito: ONO-

When N, nitro: NO2-

Different color compounds

Page 7: Geometry of Molecules & Ions

Geometric isomerism: cis-trans isomers

Occurs in sq-planar: MA2B2

And octahedral complexes: MA4B2

Page 8: Geometry of Molecules & Ions

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Geometric isomerism: octahedral complex isomers

MX3Y3

Fac (facial) isomerThree identical ligands at corners of a triangular face of octahedron

Mer (meridian) isomerThree identical ligands at corners of a triangular meridian (inside octahedron)

Page 9: Geometry of Molecules & Ions

complex Ion colorAbsorbs all colors-but- the one you see orReflects most colors but absorbs the complimentary

Page 10: Geometry of Molecules & Ions

Complex Ion Color and Crystal Field Strength

The colors of complex ions are due to electronic transitions between the split d sublevel orbitals

The wavelength of maximum absorbance can be used to determine the size of the energy gap between the split d sublevel orbitals

Ephoton = hn = hc/l = D

Page 11: Geometry of Molecules & Ions

Ligand and Crystal Field Strength

The strength of the crystal field depends in large part on the ligands

strong field ligands include: CN─ > NO2─ > en

> NH3

weak field ligands include: H2O > OH─ > F─ > Cl─ > Br─ > I─

crystal field strength increases as the charge on the metal cation increases

Page 12: Geometry of Molecules & Ions

Magnetic Properties and Crystal Field Strength

The electron configuration of the metal ion with split d orbitals depends on the strength of the crystal fieldThe 4th and 5th electrons will go into the higher energy dx2-y2 and dz2 if the field is weak and the energy gap is small – leading to unpaired electrons and a paramagnetic complexThe 4th thru 6th electrons will pair the electrons in the dxy, dyz and dxz if the field is strong and the energy gap is large – leading to paired electrons and a diamagnetic complex

Page 13: Geometry of Molecules & Ions

Low Spin & High Spin Complexes

paramagnetic

high-spin complex

diamagnetic

low-spin complex

Only electron configurations d4, d5, d6, or d7 can have low or high spin

Page 14: Geometry of Molecules & Ions

Tetrahedral Geometry &Crystal Field Splitting

Because the ligand approach interacts more strongly with the planar orbitals in the tetrahedral geometry, their energies are raisedMost high-spin complexes

Page 15: Geometry of Molecules & Ions

Square Planar Geometry & Crystal Field Splitting

d8 metalsThe most complex splitting patternMost are low-spin complexes

Page 16: Geometry of Molecules & Ions

Occurs when polar molecules are attracted to each other.

Dipole interaction happens in waterpositive region of one molecule attracts the negative region of another molecule.

Dipole interactions

Page 17: Geometry of Molecules & Ions

Dipole interactions

Occur when polar molecules are attracted to each other.Slightly stronger than dispersion forces.Opposites attract, but not completely hooked like in ionic solids.

H Fd+ d-

H Fd+ d-

Page 18: Geometry of Molecules & Ions

d+

d-

d+ d-

d+ d -

d+ d-

d+ d -

d+

d-

d + d

-d+

d-

Dipole interactions

Page 19: Geometry of Molecules & Ions

The End

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