The reversible reaction of H(2)with a bis-phosphenium complex of chromium provides a rare example of 3d transition metal/phosphenium cooperativity. Photolysis induces the activation of H(2)and yields a spectroscopically detectable phosphenium-stabilized (sigma-H-2)-complex, readily showing exchange with gaseous H(2)and D-2. Further reaction of this complex affords a phosphine-functionalized metal hydride, representing a unique example of reversible H(2)cleavage across a 3d MP bond. The same species is also accessibleviastepwise H+/H(-)transfer to the bis-phosphenium complex, and releases H(2)upon heating or irradiation. Dihydrogen transfer from the H-2-complex to styrene is exploited to demonstrate the first example of promoting hydrogenation with a phosphenium complex.