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.