Electronic Communication in Binuclear Osmium- and Iridium-Polyhydrides

[Image: see text] Reactions of polyhydrides OsH(6)(P(i)Pr(3))(2) (1) and IrH(5)(P(i)Pr(3))(2) (2) with rollover cyclometalated hydride complexes have been investigated in order to explore the influence of a metal center on the MH(n) unit of the other in mixed valence binuclear polyhydrides. Hexahydride 1 activates an ortho-CH bond of the heterocyclic moiety of the trihydride metal–ligand compounds OsH(3){κ(2)-C,N-[C(5)RH(2)N-py]}(P(i)Pr(3))(2) (R = H (3), Me (4), Ph (5)). Reactions of 3 and 4 lead to the hexahydrides (P(i)Pr(3))(2)H(3)Os{μ-[κ(2)-C,N-[C(5)RH(2)N-C(5)H(3)N]-N,C-κ(2)]}OsH(3)(P(i)Pr(3))(2) (R = H (6), Me (7)), whereas 5 gives the pentahydride (P(i)Pr(3))(2)H(3)Os{μ-[κ(2)-C,N-[C(5)H(3)N-C(5)(C(6)H(4))H(2)N]-C,N,C-κ(3)]}OsH(2)(P(i)Pr(3))(2) (8). Pentahydride 2 promotes C—H bond activation of 3 and the iridium-dihydride IrH(2){κ(2)-C,N-[C(5)H(3)N-py]}(P(i)Pr(3))(2) (9) to afford the heterobinuclear pentahydride (P(i)Pr(3))(2)H(3)Os{μ-[κ(2)-C,N-[C(5)H(3)N-C(5)H(3)N]-N,C-κ(2)]}IrH(2)(P(i)Pr(3))(2) (10) and the homobinuclear tetrahydride (P(i)Pr(3))(2)H(2)Ir{μ-[κ(2)-C,N-[C(5)H(3)N-C(5)H(3)N]-N,C-κ(2)]}IrH(2)(P(i)Pr(3))(2) (11), respectively. Complexes 6–8 and 11 display HOMO delocalization throughout the metal–heterocycle-metal skeleton. Their sequential oxidation generates mono- and diradicals, which exhibit intervalence charge transfer transitions. This notable ability allows the tuning of the strength of the hydrogen–hydrogen and metal–hydrogen interactions within the MH(n) units.