Inclusion of Copper(I) into a Novel Bipyridine-Containing Tetraphosphadiplatinacyclophane

Abstract

The 5,5′-bis(hydroxyalkyl)-2,2′-bipyridines 4a–c (Scheme 1) were prepared either in one step (4b, 4c) or in four steps (4a) starting with 5,5′-dimethyl-2,2′-bipyridine in each case. Reaction of 4a–c with mesyl chloride afforded the bis(mesylates) [–C5H3N–(CH2)n–CH2–OSO2Me]25a–c [n = 1 (a), 2 (b), 3 (c)], which could easily be transformed into the diphosphanes 6a–c by reaction with LiPPh2. Treatment of 6c, 6b with Cl2Pt(NCPh)2 and (RC6H4)2Pt(COD) according to the high-dilution method resulted in the formation of the tetraphosphadiplatinacyclophanes [–C5H3N–(CH2)4–PPh2PtCl2PPh2–(CH2)4–C5H3N–]2 (7c) and [–C5H3N–(CH2)3–PPh2Pt(C6H4R)2PPh2–(CH2)3–C5H3N–]2 (8b, 9b) (8b: R = H, 9b: R = tBu), respectively (Scheme 2). The molecular structures of 8b and 9b were elucidated by X-ray structural analyses. The noncoordinated bipyridine moieties in 8b were employed to encapsulate copper(I) to give the host/guest complex 10b (Scheme 3), which was investigated by FAB-MS, NMR spectroscopy, and cyclovoltammetry. 10b exhibited a quasi-reversible oxidation at E1/2 = –0.31 V and an electrodeposition-redissolution redox system at E1/2 = –0.79 V, owing to the formation of copper at the surface of the working electrode.