Reactions of the dirhenium(II) complexes Re2X4(μ-dppm)2 (X=Cl, Br; dppm =Ph2PCH2PPh2) with isocyanides: Part XX. Oxidation of the complexes Re2X4(μ-dppm)2(L) (X=Cl or Br; dppm=Ph2PCH2PPh2; L=t-BuNC, XylNC or CO) to the edge-sharing bioctahedral dirhenium(

The reactions of the halogens X2 (X=Cl or Br) with the diamagnetic dirhenium(II) complexes Re2X4(μ-dppm)2(L), where dppm=Ph2PCH2PPh2, X=Cl or Br, and L=XylNC (xylyl isocyanide), t-BuNC or CO, and with salts of the edge-sharing bioctahedral species [Re2X3(μ-dppm)2(CO)(NCMe)2]+, provide convenient routes to the dirhenium(III) species [Re2X5(μ-dppm)2(L)]+. These cations, where L=XylNC, t-BuNC or CO, have been isolated as their halide (Cl− or Br3−), [PF6]− and [O3SCF3]− salts. IR spectroscopy shows that terminal RNC and CO ligands are present, and a crystal structure determination of the complex [Re2Cl5(μ-dppm)2(CO)]PF6 confirms that the cation has the edge-sharing bioctahedral structure [Re2(μ-Cl)2(μ-dppm)2Cl3(CO)]+ with a formal ReRe bond (ReRe distance=2.6607(4) Å). 31P-NMR spectroscopy indicates that these salts are weakly paramagnetic, with their P resonances exhibiting unusually large upfield shifts.