Reversible cooperative dihydrogen binding and transfer with a bis-phosphenium complex of chromium

Abstract

The reversible reaction of H2with a bis-phosphenium complex of chromium provides a rare example of 3d transition metal/phosphenium cooperativity. Photolysis induces the activation of H2and yields a spectroscopically detectable phosphenium-stabilized (σ-H2)-complex, readily showing exchange with gaseous H2and D2. Further reaction of this complex affords a phosphine-functionalized metal hydride, representing a unique example of reversible H2cleavage across a 3d M-P bond. The same species is also accessibleviastepwise H+/H−transfer to the bis-phosphenium complex, and releases H2upon heating or irradiation. Dihydrogen transfer from the H2-complex to styrene is exploited to demonstrate the first example of promoting hydrogenation with a phosphenium complex.