Complexes of rhenium and osmium polyhydrides with metallic Lewis acids: X-ray crystal structure of [Ag{ReH7(PPhPrI2)2}2][PF6]

Bis(di-isopropylphenylphosphine) heptahydridorhenium(VII)(1) reacts with AgPF6, Agl, Cul, and HgCl2 to give the heterometallic complexes [Ag{ReH7(PPhPr2I)2}2][PF6](2) and [Ag{ReH7(PPhPr2I)2}][PF6](3); [Agl{ReH7(PPhPr2I)2}](4); [Cul{ReH7(PPhPr2I)2}](5); and [HgCl2{ReH7(PPhPr2I)2}](6) respectively, without loss of hydrogen. Similarly, [OsH6(PPhPr2I)2] reacts with HgCl2 to give [HgCl2-{OsH6(PPhPr2I)2}]. Complex formation is accompanied by only subtle changes in the hydride 1H n.m.r. shifts (<1 p.p.m.). However, substantial changes occur in the ν(Re–H) i.r. absorption bands. Crystals of (2) are triclinic, space group P(Z= 2), with lattice parameters a= 13.188(6), b= 16.014(6), c= 14.827(6)A, α= 112.47(3), β= 101.03(3), and γ= 90.65(3)°. The structure was solved and refined to R= 0.048 (R′= 0.047) for 4 452 reflections having 2θ⩽ 50°(Mo-KαX- radiation) collected at 200 K. The complex cation comprises a silver atom and two Re(PPhPr2I)2 fragments arranged linearly (Re–Ag–Re 172°, mean Re–Ag 2.873 A). No evidence of the hydride ligands was found from the diffraction study.