[Cu(η²‐H₂)Cl], a Model Compound for H₂ Complexes. Ab Initio Calculations and Identification by IR Spectroscopy

It cannot be simpler! This applies, however, to the structure of the title compound rather than to the experimental conditions under which it is prepared. This prototype for complexes with side‐on H 2 bonding was formed by cocondensation of monomeric CuCl with H 2 in an argon matrix and unambiguously characterized by IR spectroscopy. In such simple systems the ab initio calculations can almost take the place of experiment—they also clearly favor the side‐on coordination of the H 2 ligand and predict the surprisingly high energy of formation (93 kJ mol −1 ).