Tetrakis[(trimethylsilyl)ethynyl] Group 14 metal derivatives: an examination of the electronic interaction between two Group 14 metals connected by an acetylene wire

The tetrakis(trimethylsilyl)ethynyl derivatives of Si, Ge, Sn, and Pb were prepared and examined spectroscopically. NMR and Mössbauer spectroscopy and X-ray crystal structure data clearly demonstrate an electronic interaction in the ground state between the distal SiMe 3 groups and the central metal atom, leading to a strong shielding of the central metal atom; the respective nmr signals of the central metal are among the most shielded examples reported for a tetrahedral Group 14 metal centre with four carbon ligands. The nature of these electronic interactions is discussed.