Synthesis and Reactions of Ferrocenyl-capped Long-chain Alkynes

We had recently used a series of ferrocenyl-capped linear oligomethylene systems Fc-(CH2)n-Fc (1; with n = 4, 8, 14, 18) to form self-assembled highly ordered monolayers on “Highly Ordered Pyrolytic Graphite” (HOPG) [1]. The assemblies were all characterised by structures where the polar organometallic “head groups” were found close to each other and the long oligomethylene chains oriented parallel. It was found that the individual patterns showed a structural dependency of the length of the bridging chain and that they resembled specific planar cuts through the threedimensional structures of these compounds as they were determined by X-ray diffraction. There seemed to be a relationship between the three-dimensional crystal structures and the two-dimensional surface structure of these specific compounds. The systems 1 were either prepared by the straight forward reaction of the α ,ω-dibromoalkanes with ferrocenyllithium or by olefin-metathesis routes followed by hydrogenation. The respective mono-unsaturated analogues 2 (Fc(CH2)x–CH=CH–(CH2)x-Fc) were also investigated with regard to their surface assembly behaviour. We have now prepared the correspondingmonoand di-acetylene compounds (3, 4). We used them for the preparation of examples of 1 (hydrogenation) and have begun to investigate their specific surface chemistry. In this account we wish to report on the preparation of these ferrocenyl-capped acetylenes and diacetylenes, show their structural and coordination chemistry properties, and describe the catalytic trimerisation of one