S4

C3

S6

H2N

Si

NH2

NH2

H2N

Si

NH2

NH2

etc.

pz, (dxz, dyz)

s A’1(px , py): E’pz: A”2

(dx2 – y2, dxy): E’(dxz, dyz): E’’dz2: A’1

3 0 -1 -3 0 1

f) Now shift to the C3vpoint group and obtain the irreducible reps to which the pi bonding NH2 unit orbitals belong.

E 2C3 3v

3 0 1

= A1 + E

^^

RRh

lP

jj

jj

A1

E1 E2

A1

E1 E2

On going from C3v to D3h maintain same behavior for the C3v operations (E, C3 and v). Thus A1 in C3v could be either A’1 or A’’2. Choose A2’’ since it is antisym for h.Likewise, E could be either E’ or E’’ Choose E’’ since it is antisym for h.Thus A”2 and E’

A2”

E” (1)E” (2)

Si Orbitalss A’1(px , py): E’Pz: A”2

(x2 – y2, xy): E’(xz, yz): E’’z2: A’1

i) Show bonding between the Si orbitals and the symmetry adapted NH2 orbitals

i x,z

E C2(y)

C2(y)

x,z i = C2(y)

i

E C2(y)

C2’(-xy)xy,z

C2’(-xy)

x,z

E C2(y)

C4 (z)xy,z

C2’(-xy)

C4 (z) C2 (z)

E C2(y)

xy,z

C2’(-xy)

C4 (z) C2 (z)

C2 (z)

xy,z

xy,z

E C2(y)

C2’(-xy)

C4 (z)

C2 (z)

h

xy,z

h

xy,z

C2’(-xy)

D4h

Coordination number 1

Very rare, bulky ligands, linear structures, no possible isomers

Coordination number 2

Also rare, typical of d10, linear structures, no possible isomers

Coordination number 3

Also typical of d10, trigonal planar structures (rarely T-shaped), no possible isomers

Coordination number 4

L4

L1

M

L3

L2

L2

M

L1 L2

L1

L1

M

L1 L2

L2

cis

transTetrahedral(2 enantiomers if all ligands different)

Square planar(2 geometrical isomer

for two types of ligands)typical of d8

Very common

Tetrahedral

Square planar

Coordination number 5

Trigonal bipyramidal (tbp) Square-based pyramidal sbp)

Very similar energies, they may easily interconvert in solution (fluxionality)

Le M

Le

Le

La

La

Lb

MLb Lb

Lb

La

Coordination number 6

M

Octahedralmost common

Trigonal prismless common

Some possible isomers in octahedral complexes

B

M

A B

B

A

B

B

M

B B

B

A

A

cis-MA2B4 trans-MA2B4

B

MB A

A

A

B

B

MB B

A

A

A

fac-MA3B3 mer-MA3B3

Some examples of trigonal prismatic structures

Coordination number 7

M M

Pentagonal bipyramidal

Capped octahedral Cappedtrigonal prismatic

M

Examples of coordination number 7