POLYSULFONYLAMINES - XCIV - MOLECULES WIT H UNUSUALLY LONG N(SP(2))-SI(SP(3)) BONDS - SYNTHESIS AND CRYSTAL-STRUCTURES OF 1,2-BENZENEDISULFONYLAMINOSILANES

The following compounds were obtained by metathesis of silver 1,2-benz enedisulfonimide (AgZ) with the appropriate chlorosilanes: ZSiMe(3) (4 ), ZSi(n)Pr(3), ZSiMe(2)(n)Bu, ZSiMe(2)(CMe2-CHMe2) (7), (Z)(2)SiMe2 ( 8). In the crystal structures of 4 (monoclinic, space group P2(1)/n), 7 (monoclinic, P2(1)/c) and 8 (monoclinic, P2(1)/n), which were determ ined by low-temperature X-ray diffraction, the molecules adopt the N-s ilyl form and display unusually long bonds between the trigonal-planar N and the tetrahedrally coordinated Si atoms (4: 182.6, 7: 184.1, 8: 177.8 and 180.5 pm). For 7 in CDCl3 solution, H-1 and C-13 NMR data in dicate N,O-silylotropy. The solid state structures of molecules 4 and 7 strongly suggest that the N-Si bond lengthening in N,N-disulfonylate d aminosilanes is mainly induced by the pi-acceptor character of the S O2 groups and not by the occasionally observed coordination expansion of the Si atom through short intramolecular O ... Si contacts.