کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1323570 977295 2007 6 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Rapid geometrical equilibrium of palladium(II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine disulfide and diselenide and their catalytic activity for Suzuki coupling reaction
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی معدنی
پیش نمایش صفحه اول مقاله
Rapid geometrical equilibrium of palladium(II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine disulfide and diselenide and their catalytic activity for Suzuki coupling reaction
چکیده انگلیسی

Palladium(II) complexes with a tetradentate pseudo-tripodal ligand having two phosphino groups and two phosphine sulfide or selenide groups, pp3X2 (pp3 = tris[2-(diphenylphosphino)ethyl]phosphine, X = S (1) or Se (2)), were prepared from [PdCl(pp3)]Cl. Both of these phosphine chalcogenide complexes 1 and 2 showed rapid equilibrium between the five-coordinate [PdCl(pp3X2)]Cl with two bound phosphine chalcogenide groups and four-coordinate [PdCl2(pp3X2)] with two dissociated pendant ones in chloroform. The thermodynamic parameters for the reaction, [PdCl(pp3X2)]+ + Cl−⇄[PdCl2(pp3X2)], were obtained by low-temperature 31P NMR as follows: K298 = 3.7 × 103 and 5.4 × 102 mol−1, ΔH∘ = 11.3 ± 0.3 and 13.4 ± 0.4 kJ mol−1, and ΔS∘ = 106 ± 2 and 97 ± 2 J mol−1 K−1 for 1 and 2, respectively. The rate for the geometrical change at 246.7 K for 1 was appreciably faster than that for 2. These thermodynamic and kinetic results indicate that the phosphine selenide Se atoms can stabilize the five-coordinate structure by effective π-back donation from Pd(II) compared with the phosphine sulfide S atoms. Difference in retention of the catalytic activity for Suzuki coupling, 2 > 1 > [PdCl(pp3 or p3)]Cl, was explained by difference in the π-accepting ability that stabilizes the catalytically active Pd(0) species. Considering the rapid dissociation-coordination equilibrium of the phosphine chalcogenide groups on Pd(II), it is probable that the oxidative addition and the subsequent transmetallation of the Pd(II) species are hardly blocked by the phosphine chalcogenide groups.

Palladium(II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine disulfide and diselenide showed rapid equilibrium between the five- and four-coordinate structures in chloroform. Their retentive catalytic activity for Suzuki coupling is attributed to the π-accepting ability of the phosphine chalcogenide groups, which stabilize the catalytically active Pd(0) species.Figure optionsDownload as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Organometallic Chemistry - Volume 692, Issue 4, 15 January 2007, Pages 813–818
نویسندگان
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