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Insertion Reactions into Palladium–Carbon Bonds of Complexes Containing Terdentate Nitrogen Ligands; Experimental and Ab initio MO Studies
Author(s) -
Groen Johannes H.,
de Zwart Annemieke,
Vlaar Mark J. M.,
Ernsting Jan M.,
van Leeuwen Piet W. N. M.,
Vrieze Kees,
Kooijman Huub,
Smeets Wilberth J. J.,
Spek Anthony L.,
Budzelaar Peter H. M.,
Xiang Qin,
Thummel Randolph P.
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199808)1998:8<1129::aid-ejic1129>3.0.co;2-y
Subject(s) - chemistry , ligand (biochemistry) , palladium , norbornadiene , oxidative addition , moiety , migratory insertion , denticity , stereochemistry , reactivity (psychology) , dissociation (chemistry) , medicinal chemistry , crystallography , photochemistry , crystal structure , organic chemistry , catalysis , medicine , biochemistry , receptor , alternative medicine , pathology
Abstract Novel methyl complexes [Pd(Me)(N‐N‐N)]X (N‐N‐N = flexible or rigid terdentate nitrogen ligand, X = Cl, SO 3 CF 3 , BAr′ 4 ) have been synthesized and fully characterized. All complexes readily underwent insertion of carbon monoxide resulting in the quantitative formation of complexes [Pd{C(O)Me}(N‐N‐N)]X [X = Cl ( 1d – 6d ), BAr′ 4 ( 1e – 6e )]. Subsequently, complexes 2e – 6e underwent quantitative insertion of norbornadiene, resulting in complexes [Pd{C 7 H 8 C(O)Me}(N‐N‐N)]BAr′ 4 ( 2f – 6f ). Unexpectedly, these complexes, including even those containing rigid terdentate nitrogen ligands, possess a structure in which the nitrogen ligand is coordinated in a bidentate fashion. A kinetic study of the reaction of norbornadiene with complexes 1e – 6e revealed that the reactivity of complexes 1e – 6e toward norbornadiene increases with increasing rigidity of the terdentate ligand, i.e. with increasing strain in the PdN 3 moiety, which indicates that insertion very likely occurs via a mechanism involving nitrogen dissociation. This is fully supported by ab initio MO calculations on CO and ethylene insertion into carbon–palladium bonds of cationic model systems containing a rigid terdentate nitrogen ligand, which showed that the lowest‐energy pathway for both insertion reactions consists of substitution of one of the distal nitrogen atoms of the rigid terdentate nitrogen ligand by the substrate, followed by a rate‐determining migratory insertion of the substrate into the carbon–palladium bond.