Insertion reactions into palladium–carbon bonds of complexes containing new rigid bidentate nitrogen ligands
The neutral complexes Pd(Me)Cl(DPIA) ( 3) and Pd(Me)Cl(DQIA) ( 4), containing the novel rigid bidentate nitrogen ligands (5,6-dihydro-[1]pyrindin-7-ylidene)-isopropylamine (DPIA) and (6,7-dihydro-5 H-quinolin-8-ylidene)-isopropylamine (DQIA), respectively, have been synthesized. Complexes 3 and 4 re...
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| Published in: | Journal of organometallic chemistry Vol. 551; no. 1; pp. 67 - 79 |
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| Main Authors: | , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier B.V
30-01-1998
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | The neutral complexes Pd(Me)Cl(DPIA) (
3) and Pd(Me)Cl(DQIA) (
4), containing the novel rigid bidentate nitrogen ligands (5,6-dihydro-[1]pyrindin-7-ylidene)-isopropylamine (DPIA) and (6,7-dihydro-5
H-quinolin-8-ylidene)-isopropylamine (DQIA), respectively, have been synthesized. Complexes
3 and
4 react quantitatively with CO to give the neutral acylpalladium complexes Pd(C(O)Me)Cl(DPIA) (
6) and Pd(C(O)Me)Cl(DQIA) (
7), respectively. Complexes
3,
4,
6, and
7, which were present as mixtures of the
cis and
trans isomers, were fully characterized, and in the case of complexes
6 and
7 single crystal X-ray structures have been determined. The molecular structure of
6 and
7 show a square planar geometry with the
α-diimine ligands coordinated in a bidentate fashion with comparable bite angles of about 78°. The acylpalladium complexes
6,
7, and Pd(C(O)Me)Cl(
iPr–PyCa) (
5), containing the nitrogen ligand 2-(
N-2-propanecarbaldimino)pyridine (
iPr–PyCa), which is the flexible analogue of DPIA and DQIA, react with norbornadiene to yield the ionic alkyl complexes [Pd(C
7H
8C(O)Me)(DPIA)]Cl (
9a), [Pd(C
7H
8C(O)Me)(DQIA)]Cl (
10a), and [Pd(C
7H
8C(O)Me)(
iPr–PyCa)]Cl (
8a), respectively. Interestingly, the nature of the
α-diimine ligand influences the reaction rate of the norbornadiene insertion in the order N–N=DQIA≪
iPr–PyCa<DPIA. Competition experiments and comparison of the crystal data from
6 and
7 indicate that the complexation strength of the
α-diimine ligand is exactly opposite to the reactivity of the corresponding acylpalladium complexes toward norbornadiene, which suggest a mechanism via intermediates containing a unidentate coordinated
α-diimine ligand. |
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| ISSN: | 0022-328X 1872-8561 |
| DOI: | 10.1016/S0022-328X(97)00348-3 |