Alloyed Tetranuclear Metal Chains of Pd4?nPtn (n=0–3) Scaffolded by a New Linear Tetraphosphine Containing a PNP Bridge |
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Authors: | Prof Tomoaki Tanase Miho Tanaka Mami Hamada Yuka Morita Dr Kanako Nakamae Prof Yasuyuki Ura Prof Takayuki Nakajima |
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Institution: | Department of Chemistry, Faculty of Science, Nara Women's University, Kitauoya-nishi-machi, Nara, 630-8506 Japan |
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Abstract: | A new linear tetraphosphine containing a PNP phosphazane bridge, rac-bis(diphenylphosphinomethyl)phenylphosphino]phenylamine (rac-dpmppan), was synthesized and utilized to support a series of Pd/Pt mixed metal tetranuclear chains, Pd4?nPtn(μ-rac-dpmppan)2(XylNC)2](PF6)2 (XylNC=xylyl isocyanide; n=0: Pd4 ( 1 ), 1: PtPd3 ( 2 ), 2: PtPd2Pt ( 3 ), 2: Pt2Pd2 ( 4 ), 3: Pt2PdPt ( 5 )), in which the number and positions of additional Pt atoms were successfully controlled depending on the respective synthetic procedures using transformations from 1 to 3 through 2 and from 4 to 5 by redox-coupled exchange reactions. The 31P{1H} NMR and ESI mass spectra and X-ray diffraction analyses revealed almost identical tetranuclear structures, with slight contraction of metal-metal bonds according to incorporation of Pt atoms. The electronic absorption spectra of 1 – 5 exhibited characteristic bands at 635–510 nm with an energy propensity depending on the number and positions of Pt centres, which were assigned to HOMO (dσ*σσ*) to LUMO (dσ*σ*σ*) transition by theoretical calculations. The present results demonstrated that the electronic structures of Pd/Pt mixed-metal tetranuclear complexes are finely tuned as orbital-overlapping alloyed metal chains by atomically precise Pt incorporation in the Pd4 chain. |
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Keywords: | alloyed metal chain EMAC PdPt mixed metal complex PNP bridged tetraphosphine tetranuclear complexes |
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