Reactions of electron-rich arylpalladium complexes with olefins. Origin of the chelate effect in vinylation catalysis

M. Portnoy, Y. Ben-David, I. Rousso, David Milstein

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

Reaction of (dippp)Pd(Ph)Cl (1) with norbornene or styrene yields (dippp)PdCl2 (8) and (dippp)Pd(η2-olefin). Kinetic follow-up reveals fast formation of (dippp)Pd(phenylnorbornyl)-Cl (10), followed by its slow decomposition, with kinsertion = 0.50 × 10-3 L mol-1 s-1 and kdecomposition = 0.90 × 10-4 s-1. Phenylnorbornane and (with styrene) stilbenes are also formed. Faster reaction is observed with (dppp)Pd(Ph)Br (2) and faster still with (dippe)Pd(Cl (4) to yield, in the latter case, the stable (dippe)Pd(phenylnorbornyl)Cl (18). The rates of these reactions are strongly solvent dependent (DMF ≫ dioxane), are strongly retarded by added Cl-, and are unaffected by added phosphine, indicating that halide dissociation, followed by olefin coordination and rate-determining olefin insertion, are involved. In contrast, reaction of trans-(PiPr2 nBu)2Pd(Ph)X (X = Cl, 5; X = Br, 6) with norbornene (or styrene) involves phosphine dissociation and leads to formation of (PiPr2 nBu)2Pd(H)X. In the case of norbornene, β-carbon elimination of the unobserved intermediate phenylnorbornyl complexes followed by β-H elimination yields 1-methylene-2-phenylcyclohexenes. Complexes of the ligand dippb are unique in that both η1 and η2 coordination modes are easily accessible. While reaction products are similar to those obtained with dippp and dippe complexes, dependence of the reaction rate on reaction variables is intermediate between those observed for complexes of chelating and monodentate phosphines. The implications of these findings on catalysis are outlined.

Original languageEnglish
Pages (from-to)3465-3479
Number of pages15
JournalOrganometallics
Volume13
Issue number9
Publication statusPublished - 1994

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phosphine
Styrene
Alkenes
chelates
Catalysis
alkenes
catalysis
styrenes
phosphines
Electrons
Phosphines
Stilbenes
electrons
Chelation
elimination
Reaction products
Reaction rates
dissociation
Carbon
stilbene

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

Reactions of electron-rich arylpalladium complexes with olefins. Origin of the chelate effect in vinylation catalysis. / Portnoy, M.; Ben-David, Y.; Rousso, I.; Milstein, David.

In: Organometallics, Vol. 13, No. 9, 1994, p. 3465-3479.

Research output: Contribution to journalArticle

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N2 - Reaction of (dippp)Pd(Ph)Cl (1) with norbornene or styrene yields (dippp)PdCl2 (8) and (dippp)Pd(η2-olefin). Kinetic follow-up reveals fast formation of (dippp)Pd(phenylnorbornyl)-Cl (10), followed by its slow decomposition, with kinsertion = 0.50 × 10-3 L mol-1 s-1 and kdecomposition = 0.90 × 10-4 s-1. Phenylnorbornane and (with styrene) stilbenes are also formed. Faster reaction is observed with (dppp)Pd(Ph)Br (2) and faster still with (dippe)Pd(Cl (4) to yield, in the latter case, the stable (dippe)Pd(phenylnorbornyl)Cl (18). The rates of these reactions are strongly solvent dependent (DMF ≫ dioxane), are strongly retarded by added Cl-, and are unaffected by added phosphine, indicating that halide dissociation, followed by olefin coordination and rate-determining olefin insertion, are involved. In contrast, reaction of trans-(PiPr2 nBu)2Pd(Ph)X (X = Cl, 5; X = Br, 6) with norbornene (or styrene) involves phosphine dissociation and leads to formation of (PiPr2 nBu)2Pd(H)X. In the case of norbornene, β-carbon elimination of the unobserved intermediate phenylnorbornyl complexes followed by β-H elimination yields 1-methylene-2-phenylcyclohexenes. Complexes of the ligand dippb are unique in that both η1 and η2 coordination modes are easily accessible. While reaction products are similar to those obtained with dippp and dippe complexes, dependence of the reaction rate on reaction variables is intermediate between those observed for complexes of chelating and monodentate phosphines. The implications of these findings on catalysis are outlined.

AB - Reaction of (dippp)Pd(Ph)Cl (1) with norbornene or styrene yields (dippp)PdCl2 (8) and (dippp)Pd(η2-olefin). Kinetic follow-up reveals fast formation of (dippp)Pd(phenylnorbornyl)-Cl (10), followed by its slow decomposition, with kinsertion = 0.50 × 10-3 L mol-1 s-1 and kdecomposition = 0.90 × 10-4 s-1. Phenylnorbornane and (with styrene) stilbenes are also formed. Faster reaction is observed with (dppp)Pd(Ph)Br (2) and faster still with (dippe)Pd(Cl (4) to yield, in the latter case, the stable (dippe)Pd(phenylnorbornyl)Cl (18). The rates of these reactions are strongly solvent dependent (DMF ≫ dioxane), are strongly retarded by added Cl-, and are unaffected by added phosphine, indicating that halide dissociation, followed by olefin coordination and rate-determining olefin insertion, are involved. In contrast, reaction of trans-(PiPr2 nBu)2Pd(Ph)X (X = Cl, 5; X = Br, 6) with norbornene (or styrene) involves phosphine dissociation and leads to formation of (PiPr2 nBu)2Pd(H)X. In the case of norbornene, β-carbon elimination of the unobserved intermediate phenylnorbornyl complexes followed by β-H elimination yields 1-methylene-2-phenylcyclohexenes. Complexes of the ligand dippb are unique in that both η1 and η2 coordination modes are easily accessible. While reaction products are similar to those obtained with dippp and dippe complexes, dependence of the reaction rate on reaction variables is intermediate between those observed for complexes of chelating and monodentate phosphines. The implications of these findings on catalysis are outlined.

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