Extending distannoxane double ladders using rigid spacers:: A double ladder with eight chiral tin atoms -: and a twist!

The new bulky silicon-containing ditin precursor p-(RCl2SnCH2SiMe2)(2)C6H4 (R = CH2-SiMe3 (4)) has been synthesized and further reacted to form a unique double ladder {[p-(R(Cl)SnCH2SiMe2)(2)C6H4]O}(4) (6). The two layers within 6 are twisted with respect to one another, resulting in a helical motif and a total absence of molecular symmetry so that there are eight chiral tin atoms within the system. The structure is compared to the double ladder {[m-(R(Cl)SnCH2CH2)(2)C6H4]O}(4) (11), which was prepared from the less, sterically demanding ditin precursor m-(RCl2SnCH2CH2)(2)C6H4 (10). The two layers within 11 are parallel, and the molecule contains only two kinds of tin atom.