Preparation, properties, and reactions of metal-containing heterocycles, 101 - Inclusion of copper(I) into a novel bipyridine-containing tetraphosphadiplatinacyclophane

The 5,5'-bis(hydroxyalkyl)-2,2'-bipyridines 4a-c (Scheme 1) were prepared e ither in one step (4b, 4c) or in four steps (4a) starting with 5,5'-dimethy l-2,2'-bipyridine in each case. Reaction of 4a-c with mesyl chloride afford ed the bis(mesylates) [-C5H3N-(CH2)(n)-CH2-OSO2Me](2) 5a-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)(2 )Pt(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)(2)-PPh2-(CH2)(3)-C5H3N -](2) (8b, 9b) (8b: R = H, 9b: R = tBu), respectively (Scheme 2). The molec ular structures of 8b and 9b were elucidated by X-ray structural analyses. The noncoordinated bipyridine moieties in 8b were employed to encapsulate c opper(I) to give the host/guest complex 10b (Scheme 3), which was investiga ted by FAB-MS, NMR spectroscopy, and cyclovoltammetry. 10b exhibited a quas i-reversible oxidation at E-1/2 = -0.31 V and an electrodeposition-redissol ution redox system at E-1/2 = -0.79 V, owing to the formation of copper at the surface of the working electrode.