Reaction products of dichlorodiorganostannanes with sodium in liquid ammonia: In-situ investigations with 119Sn NMR spectroscopy and usage as intermediates for the synthesis of tetraorganostannanes

Dichlorodibutylstannane, dichlorodioctylstannane and dichlorodiphenylstannane were reacted with different amounts of sodium in liquid ammonia. At a molar ratio of R2SnCl2/Na of 1:2, polystannanes precipitated, in some cases accompanied by cyclic oligostannanes. The products resulting from mixtures with R2SnCl2/Na ratios of 1:3 to 1:10 were soluble and, hence, could be studied in-situ in liquid ammonia with 119Sn NMR spectroscopy. The compounds obtained, tin hydrides of the type R2SnH− and in certain cases distannides of the composition R4Sn22−, formed essentially independent of the R2SnCl2/Na ratio; this, in contrast to views expressed in the literature. Our experiments showed that the chemical structure of the in-situ generated species did not permit to draw conclusions about the composition of the reaction products with bromoethane and vice versa – a practice commonly described. Furthermore, we observed migration of the butyl groups both in-situ during the reaction of dichlorodibutylstannane with sodium in liquid ammonia, as well as in the final reaction product. By contrast in the case of the phenyl substituent, migration was detected not during the chemical event in liquid ammonia, but only in the compounds formed. These observations imply a different mechanism for butyl and phenyl group migration.

Dichlorodiorganostannanes were exposed to different amounts of Na in liquid ammonia. Polystannanes were formed at R2SnCl2, 1:2, ratio; at 1:3 to 1:10 ratios stannides emerged, R2SnH− and (R4Sn2)2−. These stannides reacted with bromoethane giving tetraorganostannanes. Migration of alkyl groups was evident in the formed stannides as well as in the reaction products with bromoethane.Figure optionsDownload as PowerPoint slideHighlights
► We examined reactions of R2SnCl2 with different quantities of Na in liquid NH3.
► Depending on the R2SnCl2/Na ratio, polystannanes or stannides formed.
► Stannides were identified in situ with 119Sn NMR spectroscopy.
► Migration of side groups proceeded in-situ with R = alkyl but not with R = phenyl.
► Stannides reacted with BrC2H5 to different kinds of tetraorganostannanes.