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Reductive coupling of a 9,10-dibromo-9,10-disilatriptycene derivative followed by treatment with chlorotrimethylsilane (TMSCl) affords a series of TMS-capped 9,10-disilatriptycene oligomers DSiT[n]. Each isomer, up to the pentamer (n = 5), can be separated using recycling gel permeation chromatography. The X-ray structural analysis of DSiT[2] shows that the six silicon atoms are linearly aligned in a rigid array structure. While the ultraviolet (UV) absorption maximum remains constant at 230 nm, irrespective of the chain length, the magnetic circular dichroism (MCD) spectra exhibit a red shift band near 245 nm, and the emission maximum steadily shifts from 319 to 337 nm as the number of silicon atom increases. These spectra indicate the occurrence of electronic delocalization along the one-dimensional arrangement of bridge-head disilane moieties.

A variety of 9-phospha-10-silatriptycenes (PSiT) and some derivatives, such as the phosphine selenides and cis-platinum complexes, have been prepared in order to study their structures and characteristics as a phosphine ligand. The 1J(P−Se) NMR coupling constant of the phosphine selenides demonstrate the large s character of the lone pair orbital on the phosphorus atom, attributable to the small C−P−C bond angles of the PSiT framework, as confirmed by X-ray crystallography. The strong trans influence of PSiT has been determined from the 1J(Pt−C) coupling constant measurements of the cis-[PtMe2(psit)2], which is due to the increase in the P−Pt−P angle in the complexes derived from the steric repulsion between the two bulky PSiT ligands. Both the substituent on the silicon and the bridging benzene rings affect the electronic character. Electron-withdrawing substituents on the silicon atom slightly increase the s character of the phosphorus lone pair orbital, and the isopropoxy groups on the bridging benzene...

We have prepared anti,cisoid-alternating oligosilanes up to Si22 comprising bis(tetramethylene)-tethered bicyclic disilane units end-capped with n-alkyldimethylsilyl groups to measure their UV absorption and MALDI-TOF mass spectra. It was confirmed that the absorption maximum wavelength due to the σσ* transition remains constant in the present anti,cisoid-alternating oligosilanes irrespective of elongation of the chain length, providing the generality of the suppression effect of σ-conjugation by a cisoid turn.

A bicyclic trisilane unit affords all-anti peralkylated pentasilane with dihedral angles ω > 178°. Its UV and MCD spectra as well as the X-ray crystallography of a related compound demonstrate the highly σ-conjugated system due to the rigidity of the silicon chain conformation.