Methylene-Bridged Tri- and Tetratin Compounds as Lewis Acids

Abstract

Syntheses of a series of trinuclear tin compounds, (Ph 2 XSnCH 2 ) 2 SnXPh ( 2, X = Ph; 6, X = F; 8, X = Cl) and (PhCl 2 SnCH 2 ) 2 SnCl 2 ( 10 ) and tetranuclear tin compounds (Ph 2 XSnCH 2 SnXPh) 2 CH 2 ( 3, X = Ph; 7, X = F; 9, X = Cl) are reported, and the crystal structure of [(Ph 2 FSnCH 2 ) 2 SnFPh·F] - [C 12 H 24 O 6 ·K] + ( 6b ) is described. Variable temperature 119 Sn and 19 F NMR studies indicate that the structure observed for the anion in 6b in the solid state is retained in solution. There is no NMR evidence for the formation of 1:2 adducts with fluoride ion, although such species are identified in acetonitrile solutions from electrospray mass spectrometry (ESMS). 119 Sn NMR spectral data indicate that reaction of trinuclear tin compound 8 with [(Ph 3 P) 2 N] + Cl - and HMPA results in formation of the 1:1 complexes [(Ph 2 ClSnCH 2 ) 2 SnClPh·Cl] - [(Ph 3 P) 2 N] + ( 8a ) and (Ph 2 ClSnCH 2 ) 2 SnClPh·[(CH 3 ) 2 N] 3 PO ( 8b ), respectively. In contrast, 19 F and 119 Sn NMR data show that the tetranuclear tin compound 7 reacts with fluoride ion to give a stable 1:2 adduct [(Ph 2 FSnCH 2 SnFPh) 2 CH 2 ·2F] 2- 2[Bu 4 N] + ( 7b ) in solution, being no NMR evidence for formation of a 1:1 adduct. However, ESMS indicates the presence of both 1:1 and 1:2 adducts in acetonitrile solution.