Synthesis and properties of (η3-1-methylallyl)palladium(II) formates as models of intermediates in the palladium-catalyzed reductive cleavage of allylic carboxylates and carbonates with formic acid

Masato Oshima, Toshiaki Sakamoto, Yooichiroh Maruyama, Fumiyuki Ozawa, Isao Shimizu, Akio Yamamoto

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Abstract

In order to gain insight into the mechanism of the regioselective formation of alkenes in the palladium-catalyzed reductive cleavage of allylic carboxylates or carbonates with formic acid, two types of (η3-1- methylallyl)palladium formates (P1 and P2 types) have been prepared as simple models of catalytic intermediates. The P1 type is a neutral complex coordinated with one tertiary phosphine ligand and a formato ligand: [Pd(η3-MeCHCHCH2)(O2CH)(L)] (L = PMePh2, PMe2Ph, PMe3, P(o-tolyl)3); the P2 type is a cationic complex bearing two tertiary phosphine ligands and a formate counter anion: [Pd(η3-MeCHCHCH2)L2]+CO2H- (L = PMePh2, PMe2Ph, PMe3). The structures and dynamic behavior of the complexes in solution have been examined in detail by NMR spectroscopy. Studies on the thermolysis of the P1 and P2- type complexes have clearly provided the following mechanistic viewpoints: (1) 1-butene and 2-butene are formed from the PI species; (2) butadiene is liberated from the P2 species; (3) the ratio of 1-butene to 2-butene increases as the bulkiness of phosphine ligand increases. A mechanism involving two geometrical isomers of [Pd(η3- MeCHCHCH2)(H)(L)], which are formed by decarboxylation of the P1-type complexes, has been proposed for the formation of butenes.

Original languageEnglish
Pages (from-to)453-464
Number of pages12
JournalBulletin of the Chemical Society of Japan
Volume73
Issue number2
DOIs
Publication statusPublished - 2000 Feb

ASJC Scopus subject areas

  • Chemistry(all)

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