A Quest for Atropisomerism in Cojoined Square-Planar Metal Complexes: Synthesis and Structures of Sterically Congested Diplatinum Ethynediyl Adducts

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• 作者：Tianyi Zhang ; Nattamai Bhuvanesh and John A. Gladysz
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2017
• 出版时间：February 10, 2017
• 年：2017
• 卷：2017
• 期：6
• 页码：1017-1025
• 全文大小：2531K
• ISSN：1099-0682c

文摘

The reaction of trans-[(C₆F₅)(p-tol₃P)₂Pt(Cl)] and Me₂PhP (4 equiv.) afforded trans-[(C₆F₅)(Me₂PhP)(p-tol₃P)Pt(Cl)] (2, 68 %), which is combined with HC≡CSiEt₃ in HNEt₂ in the presence of CuI (cat., –45 °C) to yield trans-[(C₆F₅)(Me₂PhP)(p-tol₃P)Pt(C≡CSiEt₃)] (3, 62 %). The reaction of 2 and 3 in HNEt₂ in the presence of nBu₄NF/CuCl (cat., –45 °C) gave a series of PtC≡CPt complexes in which the two phosphine ligands have scrambled over all four positions. Preparative TLC afforded the target complex trans,trans-[(C₆F₅)(p-tol₃P)(Me₂PhP)Pt(C≡C)Pt(PPhMe₂)(Pp-tol₃)(C₆F₅)] (4, 2.3 %) as well as trans,trans-[(C₆F₅)(Me₂PhP)₂Pt(C≡C)Pt(PPhMe₂)(Pp-tol₃)(C₆F₅)] (5, 5.6 %). The crystal structures of 2, 4, and 5 were determined. The last two show much congestion about the PtC≡CPt linkage, and various geometrical features have been analyzed. Low-temperature ¹H NMR spectra of 4 were recorded with the goal of observing separate signals for the Me₂PhP groups. This would indicate a diastereotopic relationship and provide strong evidence for the first atropisomers based upon cojoined square-planar complexes. However, no decoalescence was observed (CD₂Cl₂/–95 °C, CDFCl₂/–100 °C). Together with other data, this suggests that interconversion of the putative atropisomers remains rapid on the NMR timescale at temperatures below –95 °C.