Synthesis and characterisation of new oligoacetylenic silanes

Synthetic routes to a series of novel oligoacetylenic silanes with or without (hetero)aromatic bridges have been developed. The compound Me3SiC≡CSi(Ph)2C≡CSiMe3was first prepared, which was selectively desilylated with CaCO3in methanol at room temperature to afford the mono-protected bis(alkynyl) silane Me3SiC≡CSi(Ph)2C≡CH in moderate yield. Treatment of this mono-protected species withnBuLi, followed by silylation with Ph2SiCl2, gives a good yield of Me3SiC≡CSi(Ph)2C≡CSi(Ph)2C≡CSi(Ph)2C≡CSiMe3, with alternating silicon and acetylene units. A range of linear silicon-linked oligoalkynes containing phenylene, bithienylene and anthrylene rings, HC≡CRC≡CSi(Ph)2C≡CRC≡CH and HC≡CRC≡CSi(Ph)2C≡CRC≡CSi(Ph)2C≡CRC≡CH (R = 1,4-phenylene, 5,5′-bithienylene or 9,10-anthrylene), were synthesised by condensation reactions of Ph2SiCl2with the components obtained in situ from a HC≡CRC≡CH-nBuLi mixture in THF and the products were isolated by chromatography on silica. All these new compounds have been characterised by IR,1H and13C NMR and UV/VIS spectroscopies and mass spectrometry. The single-crystal X-ray structure of HC≡C(p-C6H4)C≡CSi(Ph)2C≡C (p-C6H4)C≡CSi(Ph)2C≡C(p-C6H4C≡CH has been determined, showing that two silicon atoms and six acetylene units constitute the backbone of the molecule.