Photoprotonation of a metal nitride complex

Protonation of both the ground and the excited states of trans-NRe(R 2 PCH 2 CH 2 PR 2 ) 2 Cl + has been shown to occur in HCl solution (R=Me). The product is the imido complex trans-HNRe(R 2 PCH 2 CH 2 PR 2 ) 2 Cl 2+ . Titration of the ground and excited states yields apparent pK values of ca. -1.0 and 4.5, respectively, demonstrating a profound increase in bascisity in the excited state. This change, which can be rationalized by a simple orbital diagram, is due to an increase in electron density at the nitride nitrogen in the excited state