Synthesis and photochemical properties of 2,2′-silaspirobiindan and related compounds

Abstract

In the last three decades, much attention has been focused on the photochemical reactions of group 14 element compounds because of their characteristic properties and reactivities. [1][2][3] Kira and Sakurai have previously reported the photorearrangement of benzyltrimethylsilane (1a) and (acyloxy)methyl-substituted benzylsilanes via C-Si photo-cleavage. 4 Very recently, Hiratsuka et al. have clarified the photophysical and photochemical processes of 1a at 77 K and the molecular structure of its excited state by MNDO-PM3 calculations. 5 However, little is known about the synthesis and photochemical behaviour of 2,2'-silaspirobiindan and its related group 14 element compounds, 6 although spiro conjugated compounds having two perpendicular π-electron systems have been widely investigated. [7][8][9] We now report the synthesis and photochemical behaviour of 2,2'-sila-and germa-spiro compounds and their related compounds.The benzyl-substituted silanes (1a-d) and the spirocompounds 2a-c were prepared by the Grignard method or the literature method (see Scheme 1). 6,10 For example, 2,2'-silaspirobiindan 2b was obtained by treatment of the Grignard reagent of o-xylylenedichloride with tetrachlorosilane in THF in a 52 % isolated yield. 11 The product was purified by flash column chromatography on silica gel using hexane eluent and repeated recrystallisation from methanol. Similarly the related group 14 element compounds were synthesised in good yields. The results are summarised in Table 1.

The Structure of Bis(catecholato)silanes: Phase Adaptation by Dynamic Covalent Chemistry of the Si–O Bond

“…As an ideal reference for the monomeric form of 1, 2,2′-silaspirobiindane (4, oxygen atoms in 1 replaced by CH 2 -groups) was synthesized according to a literature known procedure (see SI section 7.4 for SCXRD). 21 The diffusion coefficients of 4 (and derived from this the hydrodynamic radii r H and the hydrodynamic volumes V H ), determined in different solvents (CD 2 Cl 2 , 153 Å 3 ; C 6 D 6 , 136 Å 3 ; THF-d 8 , 145 Å 3 ), are nearly the same within experimental error. This indicates the absence of significant interaction of the reference compound 4 with the solvents.…”

“…Recent studies − demonstrated that more accurate information about the (dynamic) behavior in a solution can be obtained by comparing the data of the systems under study with such suitable reference compounds of similar size and shape as possible. As an ideal reference for the monomeric form of 1 , 2,2′-silaspirobiindane ( 4 , oxygen atoms in 1 replaced by CH 2 -groups) was synthesized according to a literature known procedure (see SI section 7.4 for SCXRD) . The diffusion coefficients of 4 (and derived from this the hydrodynamic radii r H and the hydrodynamic volumes V H ), determined in different solvents (CD 2 Cl 2 , 153 Å 3 ; C 6 D 6 , 136 Å 3 ; THF- d 8 , 145 Å 3 ), are nearly the same within experimental error.…”