Heterotrinuclear Complexes with Palladium, Rhodium, and Iridium Ions Assembled by Conformational Switching of a Tetraphosphine Ligand around a Palladium Center

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• 作者：Akiko Yoshii ; Hiroe Takenaka ; Hiroko Nagata ; Sayo Noda ; Kanako Nakamae ; Bunsho Kure ; Takayuki Nakajima ; Tomoaki Tanase
• 刊名：Organometallics
• 出版年：2012
• 出版时间：January 9, 2012
• 年：2012
• 卷：31
• 期：1
• 页码：133-143
• 全文大小：517K
• 年卷期：v.31,no.1(January 9, 2012)
• ISSN：1520-6041

文摘

Reaction of [PdCl₂(cod)] with a tetraphosphine, meso-bis[((diphenylphosphino)methyl)phenylphosphino]methane (dpmppm), afforded the mononuclear Pd^II complexes [PdCl(dpmppm-魏³)]X (X = Cl (1a), PF₆ (1b)); the pincer-type dpmppm ligand coordinates to the Pd atom with two outer and one inner phosphorus atom to form fused six- and four-membered chelate rings. The remaining inner phosphine is uncoordinated and readily reacts with [Cp*MCl₂]₂ to give the heterodimetallic complexes [PdCl(Cp*MCl₂)(渭-dpmppm-魏³,魏¹)]X (X = Cl, M = Rh (21a), Ir (21b); X = PF₆, M = Rh (23a), Ir (23b)). Attachment of the second metal fragment to the uncoordinated phosphine caused a crucial conformational change of the six-membered chelate ring from a stable chair conformation to a twist-boat structure, which concomitantly destabilizes the four-membered ring for its opening reactions. Complexes 21 (X = Cl) were converted to [PdCl₂(Cp*MCl₂)(dpmppm鈺怬)], in which the terminal P atom is dissociated and oxidized as Ph₂P(鈺怬)CH₂P(Ph)CH₂P(Ph)CH₂PPh₂ (dpmppm鈺怬), and in the presence of another 1 equiv of [Cp*M鈥睠l₂]₂, complexes 21 were readily transformed into the heterotrinuclear complexes [PdCl₂(Cp*M鈥睠l₂)(Cp*MCl₂)(渭-dpmppm-魏²,魏¹,魏¹)] (M = M鈥?= Rh (31a), Ir, (31b); M = Ir, M鈥?= Rh (31c)), where the third metal M鈥?is trapped by the terminal P atom with its four-membered-ring opening. Complexes 23 also reacted with another 1 equiv of [Cp*M鈥睠l₂]₂ to afford the heterotrinuclear complexes [PdCl(渭-Cl)(Cp*M鈥睠l)(Cp*MCl₂)(渭-dpmppm-魏²,魏¹,魏¹)]PF₆ (M = M鈥?= Rh (32a), Ir, (32b); M = Ir, M鈥?= Rh (32c), M = Rh, M鈥?= Ir (32d)); the additional metal M鈥?is ligated by the terminal phosphine and is further connected to the Pd atom via a chloride bridge, resulting in a rather electron-deficient M鈥?center on the basis of cyclic voltammetry. These results exhibited that the addition of a bulky metal fragment to the uncoordinated phosphine of 1 brings about a conformational switch around the Pd center to promote the ring-opening reaction of the four-membered chelate ring, which leads to an incorporation of the third metal fragment to construct heterotrinuclear structures.