The complexes [MCl
2(
2-N~N')] (N~N' = 2-C
5H
4N-CH
2-NHAr; Ar = 4-MeC
6H
4,
a; 2,6-Me
2C
6H
3,
b; 4-MeOC
6H
4,
c; 4-CF
3C
6H
4,
d; M = Pd,
1a-d; Pt,
2a-d) have been prepared and fully stereochemically characterized both inthe solid state and in solution. Their behavior in DMSO-
d6 solution is dependent on the substituents of the arylgroup and on the metal. Complexes of palladium with substituents at the
para position (
1a,
1c,
1d) display adynamic
1H NMR pattern when the solutions are heated. An enantiomeric exchange
S![](/images/gifchars/lambda.gif)
/
R![](/images/gifchars/delta.gif)
is suggested to explainsuch behavior. On the basis of the calculated negative
S![](/images/entities/thermod.gif)
values, an associative mechanism involving the solventis proposed. Under the same conditions, analogous complexes of platinum (
2a,
2c,
2d) proved to be unstable, andrelease of the N~N' ligand was observed. Complexes
1b and
2b show temperature-variable
1H NMR spectrawithout any evidence accounting for enantiomeric exchange or decoordination. DFT calculations on models of
1aand
1b show that diastereomeric exchange
S![](/images/gifchars/delta.gif)
/
S![](/images/gifchars/lambda.gif)
is a process where the complex with the higher sterical hindrance,
1b, has a lower energy barrier.