Preparation, structural characterization, and reactions of tantalum-alkyne complexes TaCl3(R1C≡CR2)L2 (L2 = DME, Bipy, and TMEDA; L = Py)

Toshiyuki Oshiki, Kouji Tanaka, Jun Yamada, Takaya Ishiyama, Yasutaka Kataoka, Kazushi Mashima, Kazuhide Tani, Kazuhiko Takai

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Abstract

Tantalum-alkyne complexes with the general formula TaCl3(R1C≡CR2)(dme) (1a, R1 = R2 = Et; 1b, R1 = R2 = n-C5H11; 1c, R1 = Ph, R2 = Me; 1d, R1 = R2 = Ph; DME = 1,2-dimethoxyethane) were synthesized by treatment of the corresponding alkynes with a low-valent tantalum derived by reduction of tantalum pentachloride with zinc powder in a mixed solvent of toluene and DME. The DME ligand can be replaced by 2 equiv of pyridine to afford the corresponding dipyridine complexes TaCl3(R1C≡CR2)(py)2 (2a, R1 = R2 = Et; 2b, R1 = R2 = n-C5H11; 2c, R1 = Ph, R2 = Me; 2d, R1 = R2 = Ph). Additionally, the reaction of 1a with the bidentate nitrogen ligands bipyridine and N,N,N′,N′-tetramethyethylenediamine (= TMEDA) gave TaCl3(EtC≡CEt)(bipy) (3) and TaCl3(EtC≡CEt)(tmedia) (4), respectively. The η2- and 4e-coordination mode of an alkyne with a large contribution of a metalacyclopropene canonical structure was revealed by spectroscopic methods (NMR and IR) and crystallographic analyses of 1a, 1c, 2a, and 4. The reactivies of the tantalum-3-hexyne complexes 1a, 2a, 3, and 4 toward 3-phenylpropanal were investigated. Only the pyridine complex 2a reacted with a stoichiometric amount of the aldehyde to afford the corresponding allylic alcohol in 77% yield upon hydrolysis. The reaction proceeded via an oxatantalacyclopentene species.

Original languageEnglish
Pages (from-to)464-472
Number of pages9
JournalOrganometallics
Volume22
Issue number3
DOIs
Publication statusPublished - Feb 3 2003

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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