A binuclear palladium(I) hydride. Formation, reactions, and catalysis

Moshe Portnoy, David Milstein

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

(dippp)Pd(Ph)Cl (3) reacts with methanol to yield the novel hydrido Pd(I) dimer {[(dippp)-Pd]2(μ-H)(μ-CO)}+Cl- (1), (dippp)PdCl2 (4), H2, benzene, and formaldehyde. In the presence of NEt3, HNEt3 +Cl- is formed instead of 4. 1 can also be formed in a reaction of Pd(dippp)2, HCl, and CO. Labeling studies and modeling reactions indicate that the novel transformation of 3 into 1 involves methanolysis of 3 followed by a β-H elimination from a methoxo intermediate to yield formaldehyde, benzene, and the 14e transient (dippp)Pd (7). Formaldehyde decarbonylation, coupling of the palladium carbonyl complex with 7, and protonation lead to 1. Alternatively, 1 can be formed by electrophilic attack of protonated 7, on the carbonyl complex (dippp)Pd(CO). A number of reactivity modes have been identified for 1. Reaction with acetylenes results in bridge-splitting to form (dippp)Pd(η2-acetylene) and in hydropalladation of the acetylene to form a vinyl complex. The hydropalladation process exhibits high regio- and stereoselectivity, resulting in cis addition and attachment of the Pd atom to the more hindered carbon, indicating electronic control. 1 undergoes exchange of the hydride for deuteride in CD3COCD3, most likely via an enol insertion into Pd-H. In the presence of an olefin, such as cyclooctene or ethyl vinyl ether, catalytic transfer deuteration takes place. α-Deuteration of the latter is preferred, indicating anti-Markovnikov Pd-H addition. The integrity of 1 is maintained during this process. With norbornene, bridge-splitting to form (dippp)Pd(norbornyl) (17) and its CO-insertion product 18 takes place. No H/D exchange catalysis is observed in this case with acetone-d6. 1 behaves as a Pd(O) complex and exhibits oxidative addition reactivity with chlorobenzene or benzyl chloride, yielding (dippp)Pd(R)Cl. The relevance of this reactivity to Pd-catalyzed reactions is discussed.

Original languageEnglish
Pages (from-to)600-609
Number of pages10
JournalOrganometallics
Volume13
Issue number2
Publication statusPublished - 1994

Fingerprint

Palladium
Carbon Monoxide
Hydrides
Catalysis
hydrides
catalysis
palladium
formaldehyde
acetylene
Formaldehyde
Acetylene
reactivity
Benzene
insertion
benzene
deuterides
Stereoselectivity
Regioselectivity
electronic control
chlorobenzenes

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

A binuclear palladium(I) hydride. Formation, reactions, and catalysis. / Portnoy, Moshe; Milstein, David.

In: Organometallics, Vol. 13, No. 2, 1994, p. 600-609.

Research output: Contribution to journalArticle

@article{be60a2efddde42eb8f0c06a3b5832ab6,
title = "A binuclear palladium(I) hydride. Formation, reactions, and catalysis",
abstract = "(dippp)Pd(Ph)Cl (3) reacts with methanol to yield the novel hydrido Pd(I) dimer {[(dippp)-Pd]2(μ-H)(μ-CO)}+Cl- (1), (dippp)PdCl2 (4), H2, benzene, and formaldehyde. In the presence of NEt3, HNEt3 +Cl- is formed instead of 4. 1 can also be formed in a reaction of Pd(dippp)2, HCl, and CO. Labeling studies and modeling reactions indicate that the novel transformation of 3 into 1 involves methanolysis of 3 followed by a β-H elimination from a methoxo intermediate to yield formaldehyde, benzene, and the 14e transient (dippp)Pd (7). Formaldehyde decarbonylation, coupling of the palladium carbonyl complex with 7, and protonation lead to 1. Alternatively, 1 can be formed by electrophilic attack of protonated 7, on the carbonyl complex (dippp)Pd(CO). A number of reactivity modes have been identified for 1. Reaction with acetylenes results in bridge-splitting to form (dippp)Pd(η2-acetylene) and in hydropalladation of the acetylene to form a vinyl complex. The hydropalladation process exhibits high regio- and stereoselectivity, resulting in cis addition and attachment of the Pd atom to the more hindered carbon, indicating electronic control. 1 undergoes exchange of the hydride for deuteride in CD3COCD3, most likely via an enol insertion into Pd-H. In the presence of an olefin, such as cyclooctene or ethyl vinyl ether, catalytic transfer deuteration takes place. α-Deuteration of the latter is preferred, indicating anti-Markovnikov Pd-H addition. The integrity of 1 is maintained during this process. With norbornene, bridge-splitting to form (dippp)Pd(norbornyl) (17) and its CO-insertion product 18 takes place. No H/D exchange catalysis is observed in this case with acetone-d6. 1 behaves as a Pd(O) complex and exhibits oxidative addition reactivity with chlorobenzene or benzyl chloride, yielding (dippp)Pd(R)Cl. The relevance of this reactivity to Pd-catalyzed reactions is discussed.",
author = "Moshe Portnoy and David Milstein",
year = "1994",
language = "English",
volume = "13",
pages = "600--609",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "2",

}

TY - JOUR

T1 - A binuclear palladium(I) hydride. Formation, reactions, and catalysis

AU - Portnoy, Moshe

AU - Milstein, David

PY - 1994

Y1 - 1994

N2 - (dippp)Pd(Ph)Cl (3) reacts with methanol to yield the novel hydrido Pd(I) dimer {[(dippp)-Pd]2(μ-H)(μ-CO)}+Cl- (1), (dippp)PdCl2 (4), H2, benzene, and formaldehyde. In the presence of NEt3, HNEt3 +Cl- is formed instead of 4. 1 can also be formed in a reaction of Pd(dippp)2, HCl, and CO. Labeling studies and modeling reactions indicate that the novel transformation of 3 into 1 involves methanolysis of 3 followed by a β-H elimination from a methoxo intermediate to yield formaldehyde, benzene, and the 14e transient (dippp)Pd (7). Formaldehyde decarbonylation, coupling of the palladium carbonyl complex with 7, and protonation lead to 1. Alternatively, 1 can be formed by electrophilic attack of protonated 7, on the carbonyl complex (dippp)Pd(CO). A number of reactivity modes have been identified for 1. Reaction with acetylenes results in bridge-splitting to form (dippp)Pd(η2-acetylene) and in hydropalladation of the acetylene to form a vinyl complex. The hydropalladation process exhibits high regio- and stereoselectivity, resulting in cis addition and attachment of the Pd atom to the more hindered carbon, indicating electronic control. 1 undergoes exchange of the hydride for deuteride in CD3COCD3, most likely via an enol insertion into Pd-H. In the presence of an olefin, such as cyclooctene or ethyl vinyl ether, catalytic transfer deuteration takes place. α-Deuteration of the latter is preferred, indicating anti-Markovnikov Pd-H addition. The integrity of 1 is maintained during this process. With norbornene, bridge-splitting to form (dippp)Pd(norbornyl) (17) and its CO-insertion product 18 takes place. No H/D exchange catalysis is observed in this case with acetone-d6. 1 behaves as a Pd(O) complex and exhibits oxidative addition reactivity with chlorobenzene or benzyl chloride, yielding (dippp)Pd(R)Cl. The relevance of this reactivity to Pd-catalyzed reactions is discussed.

AB - (dippp)Pd(Ph)Cl (3) reacts with methanol to yield the novel hydrido Pd(I) dimer {[(dippp)-Pd]2(μ-H)(μ-CO)}+Cl- (1), (dippp)PdCl2 (4), H2, benzene, and formaldehyde. In the presence of NEt3, HNEt3 +Cl- is formed instead of 4. 1 can also be formed in a reaction of Pd(dippp)2, HCl, and CO. Labeling studies and modeling reactions indicate that the novel transformation of 3 into 1 involves methanolysis of 3 followed by a β-H elimination from a methoxo intermediate to yield formaldehyde, benzene, and the 14e transient (dippp)Pd (7). Formaldehyde decarbonylation, coupling of the palladium carbonyl complex with 7, and protonation lead to 1. Alternatively, 1 can be formed by electrophilic attack of protonated 7, on the carbonyl complex (dippp)Pd(CO). A number of reactivity modes have been identified for 1. Reaction with acetylenes results in bridge-splitting to form (dippp)Pd(η2-acetylene) and in hydropalladation of the acetylene to form a vinyl complex. The hydropalladation process exhibits high regio- and stereoselectivity, resulting in cis addition and attachment of the Pd atom to the more hindered carbon, indicating electronic control. 1 undergoes exchange of the hydride for deuteride in CD3COCD3, most likely via an enol insertion into Pd-H. In the presence of an olefin, such as cyclooctene or ethyl vinyl ether, catalytic transfer deuteration takes place. α-Deuteration of the latter is preferred, indicating anti-Markovnikov Pd-H addition. The integrity of 1 is maintained during this process. With norbornene, bridge-splitting to form (dippp)Pd(norbornyl) (17) and its CO-insertion product 18 takes place. No H/D exchange catalysis is observed in this case with acetone-d6. 1 behaves as a Pd(O) complex and exhibits oxidative addition reactivity with chlorobenzene or benzyl chloride, yielding (dippp)Pd(R)Cl. The relevance of this reactivity to Pd-catalyzed reactions is discussed.

UR - http://www.scopus.com/inward/record.url?scp=0000916635&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000916635&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000916635

VL - 13

SP - 600

EP - 609

JO - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 2

ER -