252019-29-7Relevant academic research and scientific papers
Synthesis and reactions of mono- and dipalladium complexes containing 2-thienyl and 2,5 (or 2,5′) -bridged thienylene (or dithienylene) ligand: New dipalladium complex formation connected by thioketene part via C-S bond cleavage of thiophene
Kim, Yong-Joo,Lee, Sang-Chul,Cho, Moon Hwan,Lee, Soon-W.
, p. 268 - 277 (1999)
Oxidative addition reactions of 2-iodothiophene, 2-bromothiophene, and 2,5-dibromothiophene with equimolar Pd(CH2=CHPh)L2 (L=PMe3 and PEt3) at room temperature in THF produce mononuclear σ-thienyl palladium(II) complexes trans-(2-C4H3S)PdX(PMe3)2 (X=I, 1; X=Br, 2) and trans-(5-Br(2-C4H2S))PdBrL2 (L=PMe3, 3; L=PEt3, 4). Reactions using 2,5-dibromothiophene, 2,5-diiodothiophene, and 5,5-dibromo-2,2′-bithiophene under 2:1 molar ratio in THF give thienylene (or dithienylene) bridged dipalladium complexes trans,trans-L2XPd(μ-2,5-C4H2S)PdXL 2 (L=PMe3; X=I, 5; Br, 6; L=PEt3; X=Br, 7) and trans,trans-(Me3P)2BrPd(μ-2,5′-C 4H2S-C4H2S)PdBr(PMe 3)2 (8), in high yields. However, the equimolar reaction of 2,5-dibromothiophene with the Pd(0) complex results in formation of a dinuclear complex cis,trans-[(Me3P)2Pd(η 2-S=C=CH-CH=CBr)PdBr(PMe3)2 (9), in 56% yield via C-S bond cleavage of the thiophene ring. All the complexes provided satisfactory IR and NMR (1H, 31P{1H}, and 13C{1H}) spectra as well as elemental analyses. Molecular structures of 1, 7, and 9 were confirmed by X-ray crystallography. Treatment of 5 and 7 with CO (1 atm) results in CO insertion into one of the Pd-C bonds to give trans,trans-(Me3P)2IPdC(O)C4H 2SPdI(PMe3)2 (10) in 94% and trans,trans-(Et3P)2BrPdC(O)C4H 2SPdBr(PEt3)2 (11) in 23%, respectively. Also, treatments of 5 with n-butyl, tert-butyl, and cyclohexyl isocyanides result in its insertion into both of the Pd-C bonds to form iminoacyl Pd complexes trans,trans-(Me3P)2IPd-C(=N-R)C4H 2SC(=N-R)-PdI(PMe3)2 (R=n-Bu, 12; t-Bu, 13; cyclohexyl, 14), respectively.
