NEW SPIRO-TIN COMPOUNDS - REACTION OF N,N'-DIALKYL SULFUR DIIMIDES WITH CYCLIC BIS(AMINO)STANNYLENES - UNEXPECTED FORMATION OF A N-N BOND

N,N'-Dialkyl sulfur diimides (1), R(NSN)R [R = Me (a), Et (b), Pr-n (c ), (n)Bu (d)] react with cyclic bis(amino)stannylenes such as 1,3-di-t ert-butyl-4,4-dimethyl-1,3,4,2 lambda(2)-diazasilastannetedine (2) or 1,3-di-tert-butyl-4,4,5,5-tetramethyl-1,3,4,5,2 lambda(2)-diazadisilas tannolidine (3) in a 2:1 ratio to give the new spiro-tin(IV) compounds 5a-d, 6b and 6c, built from the respective cyclic bis(amino)stannylen e and a seven-membered ring in which the two sulfur diimide groups are coupled via a N-N bond and across the tin atom. A 1: 1 adduct 4 is pr oposed as an intermediate which is the final product 4e in the case of R = (t)Bu (1e). The products were characterized by multinuclear magne tic resonance (H-1, C-13, N-15, Si-29, Sn-119 NMR), and in the case of 5c the molecular structure was determined by single crystal X-ray str ucture analysis [monoclinic, space group C2/c; a = 1504.1(3), b = 1393 .3(3), c = 1688.6(3) pm; beta = 115.71(3)degrees].