title: Two hydrogen ligands on tetrairidium clusters: a relativistic density functional study.
abstract: Structural and energetic properties of Ir(4)H(2) have been determined by applying a relativistic density functional method. As previously obtained for Ir(4)H, terminal coordination of H ligands is preferred, in contrast to some other transition metals. Square-planar Ir(4) isomers with an H binding energy of up to 318 kJ mol(-1) per atom were determined as the most stable structures of Ir(4)H(2). Isomers with a tetrahedral or butterfly structure of the metal framework exhibit average H atom binding energies of up to approximately 300 kJ mol(-1). For all three types of isomers, a surprisingly large number of stable minima was identified. Unexpectedly, structural as well as energetic properties of Ir(4)H(2) complexes are very similar to Ir(4)H. Thus binding of an H atom to Ir(4) is only slightly affected by the presence of a second H ligand. In all cases examined, the reaction H(2)+ Ir(4)--> H(2)Ir(4) was found to be exothermic with reaction energies of up to 170 kJ mol(-1).
authors.affiliation: Department Chemie, Theoretische Chemie, Technische Universität München, 85747 Garching, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Krüger
authors.forename: Chuenchit
authors.initials: C
authors.lastname: Bussai
authors.forename: Alexander
authors.initials: A
authors.lastname: Genest
authors.forename: Notker
authors.initials: N
authors.lastname: Rösch
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D004735:Energy Transfer; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D007495:Iridium / Q000737:chemistry*; D007536:Isomerism; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory
chemical_list: D008024:Ligands; D007495:Iridium; D006859:Hydrogen