Reactions of the dirhenium(II) complexes Re 2X 4(μ-dppm) 2 (X=Cl, Br; dppm =Ph 2PCH 2PPh 2) with isocyanides : Part XX . Oxidation of the complexes Re 2X 4(μ-dppm) 2(L) (X=Cl or Br; dppm=Ph 2PCH 2PPh 2; L= t-BuNC, XylNC or CO) to the edge-sharing bioctahedral dirhenium(III) cations [Re 2(μ-X) 2(μ-dppm) 2X 3(L)] +

Abstract

The reactions of the halogens X 2 (X=Cl or Br) with the diamagnetic dirhenium(II) complexes Re 2X 4(μ-dppm) 2(L), where dppm=Ph 2PCH 2PPh 2, X=Cl or Br, and L=XylNC (xylyl isocyanide), t-BuNC or CO, and with salts of the edge-sharing bioctahedral species [Re 2X 3(μ-dppm) 2(CO)(NCMe) 2] +, provide convenient routes to the dirhenium(III) species [Re 2X 5(μ-dppm) 2(L)] +. These cations, where L=XylNC, t-BuNC or CO, have been isolated as their halide (Cl − or Br 3 −), [PF 6] − and [O 3SCF 3] − salts. IR spectroscopy shows that terminal RNC and CO ligands are present, and a crystal structure determination of the complex [Re 2Cl 5(μ-dppm) 2(CO)]PF 6 confirms that the cation has the edge-sharing bioctahedral structure [Re 2(μ-Cl) 2(μ-dppm) 2Cl 3(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.