By Elimination of Dihydrogen from an Organotin Hydride

The elimination of hydrogen may be induced by an amine or by a transition metal catalyst, or it may be spontaneous.21 

The mechanisms of these reactions are not understood in detail, but the spontaneous or base-induced elimination of hydrogen from a variety of compounds R2SnXH has been shown to involve a radical chain mechanism (see Section 15.3.4). 

The reduction of bis(tributyltin) oxide with sodium borohydride in ethanol apparently falls into this group of reactions. After 5 min, the only tin compound present is tribu-tyltin hydride, but, during 2 h, this is converted into hexabutylditin in good yield. The catalyst for the decomposition of the hydride appears to be the ethoxide ion which is generated from the NaBH4 and ethanol.22 

The use of transition metal catalysts to induce the elimination of hydrogen is important and has the potential for considerable development.25 The reaction of trialkyltin hydrides with a Pd(PPh3)4 catalyst may provide the best method that is presently available for preparing hexaorganodistannanes, particularly on a large scale ( 200 g).26 27 

The yields are essentially quantitative and the distannanes can often be used without purification. When Pd(PPh3)4 is added portionwise to trimethyltin hydride, the reaction is exothermic, and the hydride boils under reflux (equation 18-24). Tributyltin hydride reacts similarly, and the reaction of (solid) triphenyltin hydride can be carried out in benzene. The reaction with a 1 1 molar mixture of McvSnH and Bu3SnH gives Me3SnSnMe3, Me3SnSnBu3, and Bu3SnSnBu3 in the ratio of 1 2 1. 

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