Post on 06-Jan-2016
description
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