Stannyllithiums preparation

The reduction of the stannyl radical (t-Bu2MeSi)3Sn with alkali metals produces a variety of structural modifications depending on the solvent used (Scheme 2.55). Thus, in nonpolar heptane, a dimeric stannyllithium species [58c Li ]2 (E = Sn) was formed, whereas in more polar benzene, the monomeric pyramidal structure 58c [Ti -Li (C6H5)] was produced. In the latter compound the Li+ ion was covalently bonded to the anionic Sn atom being at the same time n -coordinated to the benzene ring. A similar monomeric pyramidal CIP 58c [Li (thf)2] was prepared by reduction in polar THE the addition of [2.2.2]cryptand to this compound resulted in the isolation of the free stannyl anion 58c K+([2.2.2]cryptand), in which the ion lacked its bonding to the Sn atom. ... 

Imidoylstannanes, R13SnCR2=NR3, can be prepared from the reaction of stannyllithium compounds with the corresponding imidoyl chlorides (C1CR2=NR3 R2 and R3 = aryl),163 or, more generally, from the reaction of an acylstannane with an amine.164 The imidoylstannane can then be reduced to an a-aminostannane (Equation (49)).165... 

Stannylaluminium compounds have been prepared from the stannyllithium compounds (equation 19-18) and their cuprates have been used in the stannylmetallation of terminal alkyncs and enynes.21 59... 

Examples of these compounds are given in Table 19-4. The stannylzinc compounds have been used in the presence of a copper or platinum catalyst for preparing vinylstan-nanes from terminal alkynes or from vinyl triflates,20 83> 84 but these reagents seem to have little advantage over the more readily available stannyllithium or stannylmagne-sium compounds. 

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