A Zwitterionic Tetrastanna(II) Cyclic Crown

A 12-membered zwitterionic tetrastanna(II) cycle 1 having a crown ether-like topology has been isolated from the deprotonation of 1,1 & PRIME;-methylenediimidazole (B) with two equivalents of Sn[N(SiMe3)(2)](2) (A). The solid-state structure and NMR analysis confirms the tetrastanna(II) cycle 1 to be comprised of two stannate(II) and two stannyliumylidene ion pairs in alternating positions of the heterocycle. Computational analysis shows greater nucleophilicity at the proximally located stannate(II) centers. Nonetheless, the tetrastanna(II) cycle 1 remains poorly reactive due to engagement of Sn-II lone pair electrons in intramolecular donor-acceptor interactions. Simple deprotonation reaction between Sn[N(SiMe3)(2)](2) (A) and N-(diisopropylphenyl)imidazole (C) in equimolar ratio has led to a stannylene 2, involving the formation of a Sn-C covalent bond with the anionic imidazol-2-yl carbon center along with the release of NH(SiMe3)(2). Compound 2 exists as a dimer, where the unsubstituted ring nitrogen atom coordinated intermolecularly to the other stannylene center.

Automated summary

A zwitterionic tetrastanna(II) cycle 1 with a crown ether-like topology was obtained from the deprotonation of 1,1'-methylenediimidazole (B) with Sn[N(SiMe3)(2)](2) (A). It consists of two stannate(II) and two stannyliumylidene ion pairs in alternating positions of the heterocycle. Despite greater nucleophilicity at the proximally located stannate(II) centers, the tetrastanna(II) cycle 1 is poorly reactive due to intramolecular donor-acceptor interactions involving Sn-II lone pair electrons. On the other hand, the deprotonation reaction between A and N-(diisopropylphenyl)imidazole (C) led to the formation of a stannylene 2, which is a dimer with coordination between the unsubstituted ring nitrogen atom and the other stannylene center.