SYNTHESIS AND STRUCTURAL AND SPECTROSCOPIC CHARACTERIZATION OF THE GERMANAZENE [GEN(2,6-I-PR2C6H3)]3 AND THE TIN AND LEAD TETRAMERS [SNN(BMES2)]4, [SNN(2,6-I-PR2C6H3)]4, AND [PBN(2,6-I-PR2C6H3)]4

The reactions of M[N(SiMe3)2]2 (M = Ge, Sn, Pb) with two bulky primary amines have been investigated. When Ge[N(SiMe3)2]2 was treated with H2N(Dipp) (Dipp = 2,6-i-Pr2C6H3), the trimeric species [GeN(Dipp)]3 (1) was formed in high yield. The reaction of Sn[N(SiMe3)2]2 with H2N(Dipp) or the primary borylamine H2NBMes2 gives the tetrameric species [SnN(Dipp)]4 (2) and [SnN(BMes2)]4 (3). The lead compound [PbN(2,6-i-Pr2C6H3)]4 (4) was prepared in a similar manner. Details of the H-1 NMR spectroscopy and X-ray crystal structures of all compounds are reported. The trimer [GeN(Dipp)]3 (1), which was described in a preliminary communication, has a planar Ge3N3 ring structure with stereochemically active Ge lone pairs. The structures of 2-4 are tetrameric, featuring Sn4N4 or Pb4N4 cubane skeletons. The data suggest considerable ionic character in the M-N bonds. Crystal data [Mo K-alpha (lambda = 0.71069 angstrom)] at 130 K are as follows: 2, a = 12.214 (2) angstrom, b = 19.129 (4) angstrom, c = 21.488 (4) angstrom, alpha = 84.27 (1)-degrees, beta = 76.15 (1)-degrees, gamma = 86.78 (1)-degrees, Z = 4, triclinic, space group P1BAR, 9463 unique observed (I > 2-sigma(I) data, R(F) = 0.050; 3, a = 28.185 (8) angstrom, c = 35.161 (11) angstrom, Z = 12, tetragonal, space group I4c2BAR, 5199 unique observed (I > 3-sigma(I) data, R(F) = 0.083; 4, a = 12.330 (3) angstrom, b = 19.242 (4) angstrom, c = 21.435 (6) angstrom, alpha = 83.06 (2)-degrees, beta = 76.61 (2)-degrees, gamma = 85.97 (2)-degrees, Z = 4, triclinic, space group P1BAR, 11095 unique observed (I > 2-sigma(I)) data, R(F) = 0.074.