The solution behavior of the cationic complexes [Pd(
3-allyl)(P-N)]
+ (P-N =
o-(PPh
2)C
6H
4CH=NR (R = C
6H
4OMe-4, Me, CMe
3, (
R)-bornyl); allyl = propenyl (
1a-
4a) and 3-methyl-2-butenyl (
1b-
4b)) consists essentially of three dynamic processes: (i) a very fastconformational change of the P-N chelate ring, which moves above and below the P-Pd-Ncoordination plane, (ii) a relatively fast
3-
1-
3 interconversion which brings about a
syn-
anti exchange only for the allylic protons
cis to phosphorus; (iii) a slower apparent rotationof the
3-allyl ligand around its bond axis. For
1b-
3b, two geometrical isomers are observed,the predominant one having the allyl CMe
2 group
trans to phosphorus. The complexes
4aand
4b, containing the chiral (
R)-bornyl group, are present in solution with two and fourdiastereomeric species, respectively. The X-ray structural analysis of
4b(ClO
4) shows thepresence of two diastereomeric molecules in the unit cell, both having distorted-square-planar coordination geometries, characterized by rather elongated Pd-CMe
2 bonds
trans tophosphorus and by a marked distortion of the allyl ligand, which is rotated away from thePPh
2 group. The complexes [Pd(
3-allyl)(P-N)]
+ react with secondary amines HY in thepresence of fumaronitrile, yielding [Pd(
2-fn)(P-N)] and allylamines. Under pseudo-first-order conditions the amination rates obey the laws
kobs =
k2[HY] +
k3[HY]
2 for
1a-
4a and
kobs =
k2[HY] for
1b,
3b, and
4b. The
k2 term is related to direct bimolecular attack on aterminal allyl carbon of the substrate, whereas the
k3 term is ascribed to parallel attack bya further amine molecule on the intermediate [Pd(allyl)(P-N)(HY)]
+. The
k2 values increasewith increasing basicity and decreasing steric hindrance of the amine, and with increasingelectron-withdrawing ability and increasing bulkiness of the P-N nitrogen substituent. Thehigher amination rates for [Pd(
3-allyl)(P-N)]
+, compared to [Pd(
3-allyl)(
![](/images/gifchars/alpha.gif)
-diimine)]
+, areessentially due to lack of displacement equilibria of the P-N ligand by amines.