POTENTIAL-ENERGY SURFACES FOR TC++H-2 AND RU++H-2 REACTIONS

Geometries, potential-energy surfaces (PES), and some one-electron properties of 12 electronic states of two second row transition metal dihydride ions, namely, TcH2+ and RuH2+ are calculated using complete active space multiconfiguration self-consistent field (MCSCF) followed by multireference single- and double-excitation configuration interaction (MRSDCI) methods. The ground-state Tc+ (a7S, d 5s1) ion does not insert into H2. The 5A2 ground state of TcH2+ with geometry re = 1.59 Å, θe = 49.5° is formed by the spontaneous insertion of Tc+ (a5D, 4d6) into H2. The quartet-state Ru+ (a4F) ion arising from the 4d7 configuration inserts spontaneously into H 2 to form the ground state (4A2) of RuH 2+ with re = 1.678 Å and θe = 29.2°. RuH2+ in the ground state is better described as a complex of Ru+ (a4F) with H 2. The energies of formation of the ground states Of TcH 2+ and RuH2+ from their dissociated counterparts are calculated as 22.4 and 21.2 kcal/mol, respectively. All the sextet-state PES's of RuH2+ and some of the quintet-state surfaces (namely, 5A1, 5A2, and 5B1) of TcH2+ contain large barriers for insertion. The high-spin linear stationary states of both TcH 2+ and RuH2+ are more stable than the low-spin linear states. The polarity of the metal-H bond in the ground state of TcH2+ is found to be opposite to that in RuH 2+. The adiabatic ionization potentials of TcH2 and RuH2 are calculated as 7.41 and 6.63 eV, respectively, at the MRSDCI level of theory. © 1990 American Institute of Physics.