Electronic structure of bispentalene complexes of titanium, zirconium, andhafnium: A photoelectron spectroscopic study

The geometrical parameters of the bis(pentalene) complexes of titanium, zir conium, and hafnium. (3a-c) have been calculated by applying the RHF method . For 3a a structure with Ci symmetry results, whereas for 3b,c D-2 symmetr y is predicted. The torsional angles between the two pentalene ligands are calculated to be 56 degrees (3a), 51 degrees (3b), and 50 degrees (3c). The orbital sequence of the six highest occupied molecular orbitals agrees ver y well with the ionization energies measured by PE spectroscopy of 3a-c. Th ese measurements support a structure with D-2 or closely related symmetry.