Acceptor Behavior and E–H Bond Activation Processes of the Unsaturated Heterometallic Anion [MoReCp(μ-PCy2)(CO)5]−(MoRe)

The ability of the title anion to act as an acceptor of simple donors and to participate in E–H bond activation processes (E = p-block element) was analyzed by examining its reactions with PPh2H, HSPh, and HCC­(p-tol). The sodium salt of this anion (1-Na) reacted with PPh2H to give the electron-precise derivative Na­[MoReCp­(μ-PCy2)­(CO)5(PPh2H)], with the added ligand trans to the PCy2 group. The latter reacted with (NH4)­PF6 to give the hydride-bridged derivative mer-[MoReCp­(μ-H)­(μ-PCy2)­(CO)5(PPh2H)], which was dehydrogenated photochemically to give first the known compound [MoReCp­(μ-PCy2)­(μ-PPh2)­(CO)5] and then the new complex [MoReCp­(μ-O)­(μ-PCy2)­(μ-PPh2)­(CO)3], with a strongly asymmetric bridging oxide ligand (Mo–Re = 2.8640(6) Å). The reaction of 1-Na with HSPh involved protonation and ligand addition to give the thiol complex [MoReCp­(μ-H)­(μ-PCy2)­(CO)5(HSPh)], which underwent spontaneous dehydrogenation to give the thiolate derivative [MoReCp­(μ-PCy2)­(μ-SPh)­(CO)5] (Mo–Re = 2.9702(8) Å), having a quite puckered central MoPReS ring. The latter rearranged photochemically to yield [MoReCp­(μ-PCy2)­(μ-SPh)­(1κ-CO)­(CO)4], which displays a Re­(CO)4 fragment and reverts thermally to the starting isomer; density functional theory calculations on these and related [MoReCp­(μ-PCy2)­(μ-X)­(CO)5] complexes (X = PPh2, Cl) revealed that the structure with the puckered central ring is strongly disfavored for bulky X groups. Compound 1-Na reacted with (p-tolyl)­acetylene to give the complex Na­[MoReCp­(μ-PCy2)­(CO)5{η2-HC2(p-tol)}], with an alkyne ligand η2-bound to Re and positioned cis to the PCy2 group. Protonation of the latter gave the alkenyl complex [MoReCp­{μ-κ1:η2-C­(p-tol)­CH2}­(μ-PCy2)­(CO)5], which rearranged spontaneously via alkenyl–carbonyl coupling and different 1,2-H shifts to give [MoReCp­{μ-η2:κ2C,O-C­(p-tol)­CHC­(O)­H}­(μ-PCy2)­(CO)4], with a formyl-alkenyl ligand O-bound to Re through its formyl fragment (Mo–Re = 2.970(1) Å).