Fundamental study of (ferrocenylethynyl)phosphines: Correlation of steric and electronic effects in C,C cross-coupling reactions

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• 作者：Bianca Milde ; Dieter Schaarschmidt ; Petra Ecorchard ; Heinrich Lang ; ^{heinrich.lang@chemie.tu-chemnitz.de}
• 关键词：(Ferrocenylethynyl)phosphine ; Palladium ; Seleno phosphine ; (Spectro-) electrochemistry ; Tolman cone angle ; C ; C cross-coupling
• 刊名：Journal of Organometallic Chemistry
• 出版年：2012
• 期刊代码：64_0022328x
• 类别：ch
• 出版时间：1 June, 2012
• 卷：706-707
• 期：Complete
• 页码：52-65
• 文件大小：912 K

摘要

Complexes [Pd(Cl)(渭-Cl)(P(CCFc)R₂)]₂ (Fc聽=聽(畏⁵-C₅H₄)(畏⁵-C₅H₅); 6e, R聽=聽^tBu; 6f, R聽=聽^cC₆H₁₁) and [PdCl₂(P(CCFc)R₂)₂] (7a, R聽=聽C₆H₅; 7b, R聽=聽2-MeC₆H₄; 7c, R聽=聽2,4,6-Me₃C₆H₂; 7d, R聽=聽^cC₄H₃O; 7e, R聽=聽^tBu; 7f, R聽=聽^cC₆H₁₁) are accessible by the reaction of P(CCFc)R₂ (3a-f) with either [PdCl₂(cod)] (5) (cod聽=聽cyclo-1,5-octadiene) or [PdCl₂(SEt₂)₂] (8). The spectroscopic, mass-spectrometric and cyclovoltammetric data of 6 and 7 were investigated and the structures of four complexes (6e, 6f, 7b, 7c) in the solid state determined. Complexes 7a-f are mononuclear with palladium in a square-planar environment and show a cis- (7b) or trans-configuration (7c) with linear FcCCP moieties in the solid state. In contrast, 6e and 6f are forming dimers with a planar Pd₂P₂Cl₂(渭-Cl)₂ core with the ferrocenylethynyl ligands positioned above and below this plane. Electrochemical studies of phosphines 3a-3f and the appropriate seleno phosphines 4a-4f show after oxidation follow-up reactions, while a reversible behavior is found for the corresponding palladium complexes 6 and 7. UV-Vis/NIR and IR spectro-electrochemical measurements of 7f indicate moderate electronic interactions between the ferrocenyl units. All complexes are catalytically active in Heck (reaction of iodo benzene with tert-butyl acrylate) and Suzuki (2-bromo toluene or 4鈥?chloro acetophenone with phenyl boronic acid) C,C cross-couplings. The influence of the electronic (¹J(³¹P-⁷⁷Se)) and the steric (Tolman cone angle) properties of the phosphine ligands on the activity of the respective palladium catalysts will be discussed.