Oxidative Addition of Dihydrogen to Divanadium in Solid Ne: Multiple-Bonded Triplet HVVH and Singlet V₂ (μ-H)₂

Dinuclear compounds of early transition metals with a high metal-metal bond order are of fundamental interest due to their intriguing bonding situation and of practical interest because of their potential involvement in catalytic processes. In this work, two isomers of V₂ H₂ have been generated in solid Ne by the reaction between V₂ and H₂ and detected by infrared spectroscopy: the linear HVVH molecule (³ Σ_g ^- ground state), which is the product of the spin-allowed reaction between V₂ (³ Σ_g ^- ground state) and H₂ , and a lower-energy, folded V₂ (μ-H)₂ isomer (¹ A₁ ground state) with two bridging hydrogen atoms. Both isomers are characterized by metal-metal bonding with a high bond order; the orbital occupations point to quadruple bonding. Irradiation with ultraviolet light induces the transformation of linear HVVH to folded V₂ (μ-H)₂ , whereas irradiation with visible light initiates the reverse reaction.