Chemistry Reference
In-Depth Information
l
Chelate-ring puckering
d
Chelate-ring puckering
H
H
Me
Me
N
N
N
N
Me
Me
Pt
Pt
H
H
(
S,R,R
,S)-
Me
2
dab
-Pt
(
R,S,S,R
)-
Me
2
dab
-Pt
H
H
N
N
N
N
Pt
Pt
H
H
(
S,R,R
,
S
)-
bip
-Pt
(
R,S,S,R
)-
bip
-Pt
H
H
H
N
N
N
N
H
Pt
Pt
H
H
(
S,R
)-
pipen
-Pt
(
R,S
)-
pipen
-Pt
Me
Me
Me
Me
N
N
N
N
Me
Me
Pt
Pt
Me
Me
(
R,R
)-
Me
4
dach
-Pt
(
S,S
)-
Me
4
dach
-Pt
Me
Me
Me
Me
N
N
N
N
Me
Me
Pt
Pt
Me
Me
(
R,R
)-
Me
4
dab
-Pt
(
S,S
)-
Me
4
dab
-Pt
Figure 5.5
Me
2
dab, bip, pipen, Me
4
dach, and Me
4
dab ligands with in-plane bulk used to
slow-down rotation about the Pt-N7 bonds in
cis
-A
2
PtG
2
compounds
- dimethyl - 2,3 - diaminobutane (Me
2
dab) was the fi rst carrier ligand used in
such a detailed NMR retro model study.
78,82,83
Me
2
dab differs from Me
2
en in having
an additional methyl substituent on each carbon atom of the ethylene chain bridging
the two nitrogens. These two methyl substituents not only increase the overall steric
rigidity of the ligand, but also, by asymmetric induction, infl uence the confi guration
of the adjacent amine groups. Each N and each C in the ring is a centre of asym-
metry. The Me
2
dab retro models provided the opportunity to defi ne the solution
structure of conformers by NMR methods, allowing us to identify the HH form of
a
cis
- A
2
PtG
2
adduct for the fi rst time
105
and also allowing us to use the known
N,N
′
