Synthesis of substituted calcium-bis(disilylamides) by transmetalation of tin(II) and tin(IV) amides

Stannylenes as well as stannanes with substituted disilylamino groups are valuable synthons for the synthesis of alkaline earth metal bis(disilylamides) via the transmetallation reaction. Whereas bis [2,2,5,5-tetramethyl-2,5-disilaaza-cyclo-pentyl]stannylene 1 is a suitable reagent for this type of reaction, bis[trimethylsilyl-tris(trimethylsilyl)silylamino]stannylene 2 (monoclinic, P2(1)/c, a = 1492.6(2), b = 1705.2(2), c = 1865.3(3) pm, beta = 109.03(2)degrees, Z = 4) is not only attacked at the Sn-N-bond but also the N-Si-bond is cleaved by calcium metal. Similar light sensitivity as for 2 is observed for the mercury bis [trimethylsilyl-tris(trimethylsilyl)silylamide] 3, the homolytic M-N-bond cleavage leads to the formation of the trimethylsilyl-tris(trimethylsilyl)silylamino radical (g = 2.00485; a(N) = 16.2 G). The calcium tin exchange reaction of 1 in THF yields tris(tetrahydrofuran-O)calcium-bis[2,2,5,5-tetramethyl-2,5- disilaaza-cyclo-pentanide] 4 (monoclinic, P2(1)/n, a = 1060.9(2), b = 1919.3(5), c = 1686.0(3) pm, beta = 90.30(2)degrees, Z = 4). The stannanes Me(n-4)Sn[N(SiMe(3))(2)](n) with n = 1 or 2 are also valuable materials for the synthesis of bis(tetrahydrofuran-O)calcium-bis[bis(trimethylsilyl)amide].