Synthesis of Zwitterionic Group 14 Centered Complexes: Traditional Coordination and Unusual Insertion Chemistry

Novel cationic E–Cl (E = Ge, Sn) fragments stabilized by a bis­(phosphino)­borate ligand (2E) were synthesized by a 1:1 stoichiometric addition of ECl2 and [Tl]­[(Ph2PCH2)2BPh2]. The metrical parameters are consistent with dative bonds between the phosphorus atoms and the electron-deficient group 14 element, which is in contrast to the traditionally used aryl- and nitrogen-based ligands, which are always covalently bound. The reaction of a second equivalent of bis­(phosphino)­borate results in the unexpected insertion of the main group center into the aliphatic B–C bond of the ligand backbone to form 3E, in addition to phosphine-borane dimer (Ph2PCH2BPh2)2 (4). The pendant phosphine on 3E was shown to possess donor ability in the coordination of BH3 (5E).