Molecular structure of a monomeric, base-free metal(I) amide, TlN[Si(CH3)(3)](2), by gas electron diffraction and by density functional theory and abinitio MP2 calculations

Thallium bis(trimethylsilyl)amide is a monomer in the gas phase. The molecu lar symmetry is C-2, the Tl-N bond length is 214.8(12) pm by gas electron d iffraction as compared to about 258 pm in the crystalline dimer (Klinkhamme r, K. W.; Henkel, S. J. Organamet. Chem. 1994, 480, 167). Structure optimiz ation by DFT or ab initio (MP2) calculations with the ECP basis set on the Tl atom fails to reproduce the experimental Tl-N bond distance unless the 5 s,5p,5d electrons on the metal are described explicitly and the atomic basi s set includes both polarization and diffuse functions.