Sulfur-silicon bonds lengths

As mentioned earlier (Section II, A, 1,a), although the silicon-silicon bond in hexamethyldisilane is fairly resistant to oxidative cleavage by concentrated sulfuric acid, this bond in higher homologs of the series CH3[Si(CH3)2] CH3 becomes more reactive toward the acid with increasing chain length. 

In the reaction with thiophene 32, the disilathiirane 38 was unexpectedly formed in about 50 % yield by way of sulfur extraction. The X-ray structure analysis of the disilathiirane 38 revealed a very short Si-Si bond length of 230.5 pm and an almost planar environment at the silicon atoms (angular sum C-Si-C + C-Si-Si + Si-Si-C = 358 7°) [10]. These features are typical for related three-membered rings of this type and were also observed for other disilathiiranes [13]. As illustrated by the isolation of the 1,2-disilacyclohexadiene 39, sulfur abstraction from 32 seems to be initiated by [2+4]-cycloaddition of disilene 3. The bicyclic compound 40 is most likely formed by photoisomerization of 39 [14]. 

The solid-state structure of bis(2-(methylthiomethyl)phenyl)chlorosilane 2 (Fig. 2) shows an interaction between one sulfur atom and the silicon in a trigonal bipyramidal environment. The Si-S bond length of 313.30(16) pm is shorter than the sum of the van der Waals radii (390 pm). 

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