page_title: Dihydrogen complex
hierarchical_section_title: Dihydrogen complex
caption_attribution_description: chemical reaction involving H2
context_page_description: Dihydrogen complexes are coordination complexes containing intact H₂ as a ligand. The prototypical complex is W(CO)₃(PCy₃)₂. This class of compounds represent intermediates in metal-catalyzed reactions involving hydrogen. Hundreds of dihydrogen complexes have been reported. Most examples are cationic transition metals complexes with octahedral geometry.
  Upon complexation, the H−H bond is extended to 0.81–0.82 Å as indicated by neutron diffraction, about a 10% extension relative to the H−H bond in free H₂. Some complexes containing multiple hydrogen ligands, i.e. polyhydrides, also exhibit short H−H contacts. It has been suggested that distances < 1.00 Å indicates significant dihydrogen character, where separations > 1 Å are better described as dihydride complexes.
context_section_description: Dihydrogen complexes are coordination complexes containing intact H₂ as a ligand.  The prototypical complex is W(CO)₃(PCy₃)₂(H₂).  This class of compounds represent intermediates in metal-catalyzed reactions involving hydrogen.  Hundreds of dihydrogen complexes have been reported.  Most examples are cationic transition metals complexes with octahedral geometry.
  Upon complexation, the H−H bond is extended to 0.81–0.82 Å as indicated by neutron diffraction, about a 10% extension relative to the H−H bond in free H₂. Some complexes containing multiple hydrogen ligands, i.e. polyhydrides, also exhibit short H−H contacts.  It has been suggested that distances < 1.00 Å indicates significant dihydrogen character, where separations > 1 Å are better described as dihydride complexes (see figure).
caption: Formation and equilibrium structures of metal dihydrogen and dihydride complexes (L = ligand).
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