Geometry and Electronic Structure of Titanacycloalkenes

1999-02-27T00:00:00Z (GMT) by Daniel B. Lawson Roger L. DeKock
A number of titanacycloalkenes, H2TiC2H2, HTiC3H3, H2TiC4H4, and HTiC5H5, have been studied using ab initio techniques. Vibrational frequencies were computed at the RHF, MP2, BLYP, and B3LYP levels. Both a LANL2DZ pseudopotential and an all-electron TZV basis set was used for each method. The electronic structure of the systems of interest is characterized in terms of natural resonance theory (NRT) and the atoms in molecules (AIM) analysis. All rings are planar except for titanabenzene, HTiC5H5. H2TiC2H2 has C2v symmetry and has single Ti−C bonds. HTiC3H3, unlike the isovalent cyclobutadiene and silacyclobutadiene, has C2v symmetry and shows significant electron delocalization. In H2TiC4H4 the TiC4 ring is planar with equivalent single Ti−C bonds and has C2v symmetry. HTiC5H5 has a boat-shaped geometry where the angle between the CTiC plane and the plane formed by the neighboring four carbon atoms is nearly 90°. AIM analysis isolates a weak critical point between Ti and the para-C atom, and NRT analysis confirms the weak bonding interaction.