Synthesis, Structure, and Bonding Properties of Hypercoordinate Triorganotin Compounds Featuring Three O→Sn Interactions

Abstract

Here, heptacoordinate and hexacoordinate triorganotin compounds [o-{(Ph 2 )(O)P}C 6 H 4 ] 3 SnX (X = F (2 a), Cl (2 b), Me (2 f)) featuring three O!Sn interactions were synthesized. Chloro (2 b) and methyl (2 f) compounds were obtained from the oxygenation of the heptacoordinate triorganotin compounds {o-(Ph 2 P)C 6 H 4 } 3 SnX (X = Cl (1 b), Me (1 f)) bearing three P donors. The fluorination of 2 b using tetrabutylammonium fluoride (TBAF) yielded the fluoro analogue 2 a. Structural studies were performed on a series of hypercoordinate triorganotin compounds, 2. The chloro analogue (2 b) exhibited a hexacoordi-nate geometry attributed to the SnÀ Cl bond cleavage, where the highly electrophilic stannyl cation was stabilized by three O donors. In contrast, both the fluoro (2 a) and methyl (2 f) analogues exhibited heptacoordinate structures. Although 2 f adopted a tricapped tetrahedral geometry, 2 b is classified to adopt a distinctly rare bicapped trigonal pyramidal geometry featuring one strong LP(O)!σ*(SnÀ F) interaction and two weak LP(O)!σ*(SnÀ C) interactions (LP: lone pair electrons). The origin of the structural alternations depending on the substituent is discussed using density functional theory (DFT) calculations.