Synthetic and structural studies ion the cyclic bis(amino)stannylenes Sn[(NR)2C10H6-1,8] and their reactions with SnCl2 or Si[(NCH2But)2C6H4-1,2] (R = SiMe3 or CH2But)

Treatment of {HNR}(2)C10H6-1,8 [R = SiMe3 (1), CH2But (2)] with Sn[N(SiMe3)(2)](2) afforded the cyclic stannylene Sn[{NR}(2)C10H6-1,8] [R = SiMe3 (3), CH2But (4)]. From 3 and SnCl2 in THF and crystallisation from toluene, the product was the crystalline tetracyclic compound Sn(Cl)[{N(SiMe3)}(2)C10H6-1,8]SnCl ( 5) as the (toluene)0.5-solvate. Reaction of 4 with the silylene Si[(NCH2But)(2)C6H4-1,2] (6) [abbreviated as Si(NN)] in benzene and crystallisation in presence of Et2O furnished the crystalline tricyclic complex Sn[{Si(NCH2But)(2)C6H4-1',2'}(2)-{(NCH2But)(2)C10H6-1,8}] (7) as the Et2O-solvate. Complex 5 slowly dissociated into its factors 3 and SnCl2 in toluene, but rapidly in THF. Solutions of 7 in C6D6, C7D8 or THF-d(8), studied by multinuclear, variable temperature NMR spectroscopy, revealed the presence of an equilibrium between 8 (an isomer of 7, in which the skeletal atoms of the eight-membered ring were SnNCCCNSiSi rather than the SnSiNCCCNSi of 7) and 4 + 2 Si(NN), with 8 dominant in PhMe but not in THF; additionally 8 was shown to be fluxional and solutions of 8 in C6D6 or C7D8 decomposed to give the silane Si(NN)[(NCH2But)(2)C10H6-1,8], 6 and Sn metal. The X-ray structures of 3, 5 and 7 are presented.