Dihydrogen Adduct (Co-H₂) Complexes Displaying H-atom and Hydride Transfer
The prototypical reactivity profiles of transition metal dihydrogen complexes (M‐H₂) are well‐characterized with respect to oxidative addition (to afford dihydrides, M(H)₂) and as acids, heterolytically delivering H⁺ to a base and H⁻ to the metal. In the course of this study we explored plausible alternative pathways for H₂ activation, namely direct activation through H‐atom or hydride transfer from the σ‐H₂ adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S = ½ and an anionic S = 0 Co‐H₂ adduct, both supported by a trisphosphine borane ligand (P₃^B). The thermally stable metalloradical, (P₃^B)Co(H₂), serves as a competent precursor for hydrogen atom transfer to ᵗBu₃ArO·. What is more, its anionic derivative, the dihydrogen complex [(P₃^B)Co(H₂)]¹⁻, is a competent precursor for hydride transfer to BEt₃, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M‐H₂ complexes known.
© 2020 Wiley‐VCH. Issue Online: 01 December 2020; Version of Record online: 02 October 2020; Accepted manuscript online: 14 August 2020; Manuscript received: 16 July 2020. This research was supported by the Department of Energy (DOE‐0235032) with additional facilities support provided by the DOW Next Generation Educator Fund and the Beckman Institute at Caltech. We acknowledge Daniel Suess for initial studies of complex [Co](H) and thank Larry Henling for assistance with refinement of crystallographic data. The authors declare no conflict of interest.
Supplemental Material - anie202009814-sup-0001-misc_information.pdf