Reactivity Studies on an Intramolecularly Coordinated Organotin(IV) Carbonate

The reactivity of the intramolecularly coordinated organotin­(IV) carbonate L­(Ph)­Sn­(CO₃) (1), where L stands for an N,C,N-chelating ligand, 2,6-(Me₂NCH₂)₂C₆H₃, was studied. The treatment of 1 with ferrocene-based carboxylic acids RCOOH afforded the organotin­(IV) dicarboxylates LPhSn­(O₂CR)₂, where R is ferrocenyl (2), 2-ferrocenylethyl (3), and [(1E)-2-ferrocenyl]­ethenyl (4). Surprisingly, compounds 2–4 are sensitive to moisture and easily hydrolyze with condensation into the corresponding hexameric organotin oxo clusters (PhSnO)₆(O₂CR)₆ (R = ferrocenyl (5), 2-ferrocenylethyl (6), and [(1E)-2-ferrocenyl]­ethenyl (7)) possessing a Sn₆O₆ drumlike core. On the other hand, treatment of 1 with non-carboxylic acids such as HOTf, H₃BO₃, H₃PO₃, and t-BuPO₃H₂ afforded the triflate salt of a cationic organotin­(IV) hydroxide {[LPh­(H₂O)­Sn­(μ-OH)]₂}­(OTf)₂ (8), stannaboroxine LPhSnB₂O₃(OH)₂ (9), and organotin­(IV) phosphite [L­(Ph)­Sn­(HPO₃)]₂ (10) and phosphonate {[L­(Ph)­Sn]₂(μ-OH₂)­(μ-t-BuPO₃)₂} (11), respectively. Compounds 2–11 were characterized by elemental analysis and multinuclear NMR spectroscopy, and the molecular structures of compounds 6 and 9–11 were determined by single-crystal X-ray diffraction analysis. In addition, compounds 2–7 bearing redox-active ferrocenyl groups were studied by cyclic voltammetry.