Structure and Bonding of Transition Metal Dihydrogen Complexes [M(CO)₅(H₂)] (M = Cr, Mo, W)

Important intermediates in catalytic hydrogenation, η²‐dihydrogen complexes are also appealing subjects for theoretical studies. The MH₂ binding enthalpies for the complexes [M(CO)₅(H₂)] (M = Cr, Mo, W) were calculated at the CCSD(T)/MP2 level as 15.9 (M = Cr), 12.8 (M = Mo), and 16.3 kcal mol⁻¹ (M = W). Charge decomposition analysis suggests that H₂ is a significant σ donor and a moderate π acceptor. The topological analysis of the electron density distribution indicates a cyclic structure for the MH₂ moiety.