o-Bis(haloorganostannyl)benzenes As Powerful Bidentate Lewis Acids toward Halide Ions

The synthesis of the o -phenylene-bridged ditin species o -C 6 H 4 (SnXMe 2 ) 2 ( 2, X = Cl; 4, X = F) and o -C 6 H 4 (SnCl 2 Me) 2 ( 3 ) is reported and the crystal structures of [ o- C 6 H 4 (SnClMe 2 ) 2 ·Cl] - [(Ph 3 N) 2 P] + ( 5 ) and [ o -C 6 H 4 (SnClMe 2 ) 2 ·F] - [K·C 20 H 24 O 6 ] + ( 7 ) are described. Variable-temperature 119 Sn and 19 F NMR studies indicate that 2 and 4 act as bidentate Lewis acids toward chloride and fluoride ions exclusively forming the stable anionic 1:1 complexes 5, 7, and [ o -C 6 H 4 (SnFMe 2 ) 2 ·F] - [Et 4 N] + ( 8 ). No formation of dianionic 1:2 adducts was observed even with excess of halide ions. The affinity of 2 toward fluoride is greater than toward chloride. Reaction of 2 with HMPA gives the neutral complex o- C 6 H 4 (SnClMe 2 ) 2 ·(Me 2 N) 3 PO ( 10 ), the crystal structure of which is also described.