Synthetic, Structural, and Spectroscopic Studies of Sterically Crowded Tin-Chalcogen Acenaphthenes

摘要

A series of sterically encumbered peri-substituted acenaphthenes have been prepared containing chalcogen and tin moieties at the close 5,6-positions (Acenap[SnPh_3][ER], Acenap = acenaphthene-5,6-diyl, ER = SPh (1), SePh (2), TePh (3), SEt (4); Acenap[SnPh_2Cl][EPh], E = S (5), Se (6); Acenap[SnBu_2Cl][ER], ER = SPh(7), SePh (8), SEt (9)). Two geminally bis(peri-substituted) derivatives ({Acenap[SPh_2]}_2SnX_2, X = Cl (10), Ph (11)) have also been prepared, along with the bromo-sulfur derivative Acenap(Br)-(SEt) (15). All 11 chalcogen-tin compounds align a Sn-C_(Ph)/Sn-Cl bond along the mean acenaphthene plane and position a chalcogen lone pair in close proximity to the electropositive tin center, promoting the formation of a weakly attractive intramolecular donor-acceptor E···Sn-C_(Ph)/E···Sn-Cl 3c-4e type interaction. The extent of E→Sn bonding was investigated by X-ray crystallography and solution-state NMR and was found to be more prevalent in triorganotin chlorides 5-9 in comparison with triphenyltin derivatives 1-4. The increased Lewis acidity of the tin center resulting from coordination of a highly electronegative chlorine atom was found to greatly enhance the lp(E)-σ*(Sn-Y) donor-acceptor 3c-4e type interaction, with substantially shorter E-Sn peri distances observed in the solid state for triorganotin chlorides 5-9 (~75% Σ~r_(vdW)) and significant ~1J(~(119)Sn,~(77)Se) spin-spin coupling constants (SSCCs) observed for 6 (163 Hz) and 8 (143 Hz) in comparison to that for the triphenyltin derivative 2 (68 Hz). Similar observations were observed for geminally bis(peri-substituted) derivatives 10 and 11.