Synthesis and characterisation of new oligoacetylenic silanes

Abstract

Synthetic routes to a series of novel oligoacetylenic silanes with or without (hetero)aromatic bridges have been developed. The compound Me3SiCCSi(Ph)2CCSiMe3 was first prepared, which was selectively desilylated with CaCO3 in methanol at room temperature to afford the mono-protected bis(alkynyl) silane Me3SiCCSi(Ph)2CCH in moderate yield. Treatment of this mono-protected species with nBuLi, followed by silylation with Ph2SiCl2, gives a good yield of Me3SiCCSi(Ph)2CCSi(Ph)2CCSi(Ph)2CCSiMe3, with alternating silicon and acetylene units. A range of linear silicon-linked oligoalkynes containing phenylene, bithienylene and anthrylene rings, HCCRCCSi(Ph)2CCRCCH and HCCRCCSi(Ph)2CCRCCSi(Ph)2CCRCCH (R = 1,4-phenylene, 5,5′-bithienylene or 9,10-anthrylene), were synthesised by condensation reactions of Ph2SiCl2 with the components obtained in situ from a HCCRCCH–nBuLi mixture in THF and the products were isolated by chromatography on silica. All these new compounds have been characterised by IR, 1H and 13C NMR and UV/VIS spectroscopies and mass spectrometry. The single-crystal X-ray structure of HCC(p-C6H4)CCSi(Ph)2CC(p-C6H4)CCSi(Ph)2CC(p-C6H4)CCH has been determined, showing that two silicon atoms and six acetylene units constitute the backbone of the molecule.