Nickel(II) Dihydrogen and Hydride Complexes as the Intermediates of H2 Heterolytic Splitting by Nickel Diazadiphosphacyclooctane Complexes

The interaction of a series of [Ni((P2N2R2)-N-R1)(2)](2+) complexes 1-4 (where (P2N2R2)-N-R1=1,5-R-2-3,7-R-1-1,5-diaza-3,7-diphosphacyclooctane; R-1=o-Py, Ph; R-2=CHPh2, p-Tol) with H-2 is reversible yielding the products of heterolytic splitting of dihydrogen in the metal coordination sphere - [NiH((P2N2R2)-N-R1)((P2N2H)-N-R1-H-R2)](2+). Experiments conducted with parahydrogen allowed to see the signal at about -4 ppm corresponding to the metal-bound H-2 in the nickel dihydrogen complex [Ni(eta(2)-H-2)((P2N2CHPh2)-N-Ph)(2)](2+) (3-H-2) - the short-living non-classical intermediate, which so far has been revealed only computationally.

Automated summary

A series of complexes [Ni((P2N2R2)-N-R1)(2)](2+) can interact with H-2 reversibly, producing products capable of heterolytic splitting of dihydrogen. Experiments with parahydrogen revealed the presence of the short-lived non-classical intermediate 3-H-2 in the nickel dihydrogen complex, which has so far only been identified computationally.