On the electronic structure and chemical bonding of titanium tetraauride: TiAu4 and TiAu4−

The structural and electronic properties of titanium tetraauride are investigated using photoelectron spectroscopy and density functional calculations. The photoelectron spectra of TiAu4− show a relatively simple spectral pattern with a large energy gap, suggesting that neutral TiAu4 has a highly stable electronic configuration. Theoretical calculations have found a slightly distorted tetrahedral structure for TiAu4−, whereas the closed shell neutral TiAu4 has perfect Td symmetry. Chemical bonding analyses suggest that the AuTi bonds have multiple bond characters due to the Au 5d to Ti 3d back donation and that chemical bonding in the tetraauride is similar to that in heavier titanium tetrahalides.