Hydrolysis of dinuclear spacer-bridged diorganotin(IV) triflates. A novel cationic double ladder with supramolecular association

A series of oligomethylene-bridged diorganotin triflates R(OTf)₂Sn(CH₂)_<i>n</i>Sn(OTf)₂R (R = CH₂SiMe₃; <i>n</i> = 3, 4, 8, 10) were synthesized by reaction of triflic acid with the precursor oxides R(O)Sn(CH₂)_<i>n</i>Sn(O)R. On the basis of ¹¹⁹Sn NMR (in acetonitrile) the triflates appear to be the simple six-coordinated ionic species [(MeCN)₄(RSn(CH₂)_<i>n</i>SnR)(MeCN)₄]²⁺. These triflates readily undergo hydrolysis to give products, the identity of which depends on the length of the oligomethylene bridge. For <i>n</i> = 3 (<b>5</b>), the solid-state structure shows association of two dimeric units, which results in a tetracationic double ladder. Extensive hydrogen bonding gives rise to a supramolecular association. Solution ¹¹⁹Sn NMR and ES MS suggest some dissociation of <b>5</b> into dimers containing four tin atoms and possibly monomers containing two tin atoms. A rudimentary solid-state structure for <i>n</i> = 4 (<b>6</b>) indicates a linear polymer based on dimeric (four tin atoms) units. The structure of <b>6</b> also features extensive hydrogen bonding, this time effectively giving rise to alternating layers of cations and anions.<br>