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

A series of sterically encumbered peri-substituted acenaphthenes have been prepared containing chalcogen and tin moieties at the close 5,6-positions (Acenap­[SnPh3]­[ER], Acenap = acenaphthene-5,6-diyl, ER = SPh (1), SePh (2), TePh (3), SEt (4); Acenap­[SnPh2Cl]­[EPh], E = S (5), Se (6); Acenap­[SnBu2Cl]­[ER], ER = SPh­(7), SePh (8), SEt (9)). Two geminally bis­(peri-substituted) derivatives ({Acenap­[SPh2]}2SnX2, 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–CPh/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–CPh/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% ∑rvdW) and significant 1J(119Sn,77Se) 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.

一系列具有空间位阻的苊（acenaphthene）位取代衍生物已被合成，其在紧邻的5,6位引入了硫族元素（chalcogen）与锡基团：通式为Acenap­[SnPh3]­[ER]，其中Acenap指苊-5,6-二基（acenaphthene-5,6-diyl），ER分别为SPh（化合物1）、SePh（2）、TePh（3）、SEt（4）；另一类为Acenap­[SnPh2Cl]­[EPh]，其中E为S（5）、Se（6）；还有Acenap­[SnBu2Cl]­[ER]，ER为SPh（7）、SePh（8）、SEt（9）。同时还合成了两种偕双（位取代）衍生物({Acenap­[SPh2]}2SnX2，X=Cl（10）、Ph（11）)，以及溴-硫族衍生物Acenap­(Br)­(SEt)（15）。上述11种硫族-锡化合物均将Sn–CPh/Sn–Cl键排布于苊母核的平均平面内，并使硫族元素的孤对电子靠近带正电性的锡中心，从而促进形成弱吸引力的分子内供体-受体型相互作用，即E···Sn–CPh/E···Sn–Cl 3c-4e（三中心四电子）型相互作用。通过X射线晶体衍射与溶液态核磁共振（nuclear magnetic resonance, NMR）对E→Sn成键的程度进行了研究，结果表明：与三苯基锡衍生物1~4相比，三有机锡氯化物5~9中的该相互作用更为显著。研究发现，高电负性氯原子配位会增强锡中心的路易斯酸性，从而大幅强化孤对电子lp(E)−σ*(Sn–Y)型供体-受体三中心四电子相互作用；在固态下，三有机锡氯化物5~9的E–Sn位间距更短（约为范德华半径和的75%），且化合物6（163 Hz）与8（143 Hz）的¹J(¹¹⁹Sn,⁷⁷Se)自旋-自旋耦合常数（spin-spin coupling constants, SSCCs）远高于三苯基锡衍生物2（68 Hz）。偕双位取代衍生物10与11也呈现出类似的实验现象。