Synthesis and Properties of Bridgehead-Functionalized Permethylbicyclo[2.2.2]octasilanes
作者:Harald Stueger、Bernd Hasken、Uwe Gross、Roland Fischer、Ana Torvisco Gomez
DOI:10.1021/om400184y
日期:2013.8.26
A series of previously unknown bridgehead-functionalized bicyclo[2.2.2]octasilanes, Me3Si-Si8Me12-X, X-Si8Me12-X, and X-Si8Me12-Y [X, Y = -SiMenPh3-n (n = 1, 2) (2, 3, 10), -SiMe(2)Fc (Fc = ferrocenyl) (4, 11, 13, 14), -COR (R = Me, tBu) (6, 7, 12), COOMe (8), COOH (9)], have been prepared by the reaction of the silanides Me3Si-Si8Me12-K+ or K+-Si8Me12-K+ with proper electrophiles and fully characterized. The molecular structures of 2, 3, 4, 6, 8, 9, 10, and 13 as determined by single-crystal X-ray diffraction analysis exhibit a slightly twisted structure of the bicyclooctasilane cage. Endocyclic bond lengths, bond angles, and dihedral angles are not influenced considerably by the substituents attached to the bridgehead silicon atoms. Due to sigma(SiSi)/pi(aryl) conjugation, a 20-30 nm bathochromic shift of the longest wavelength UV absorption band relative to Me3Si-Si8Me12-SiMe3 (1) is evident in the UV absorption spectra of the phenyl and ferrocenyl derivatives. Otherwise, UV absorption data do not support the assumption of aryl/aryl or aryl/C=O interaction via the sigma(SiSi) bicyclooctasilane framework.