Mixed carbonyl–nitrile complexes of dirhenium(II). The structural characterization and reactivity of salts of the [Re 2Cl 3(μ-dppm) 2(CO)(NCMe) n] + cations (dppm=Ph 2PCH 2PPh 2, n=1 or 2)

Abstract

The monocarbonyl complexes Re 2X 4(μ-dppm) 2(CO) (X=Cl or Br) react with stoichiometric quantities of the nitriles RCN (R=Me or Ph) in the presence of TlY (Y=PF 6 or O 3SCF 3) to afford complexes of the type [Re 2X 3(μ-dppm) 2(CO)(NCR)]Y and [Re 2X 3(μ-dppm) 2(CO)(NCR) 2]Y in high yield. Crystal structure determinations on the salts [Re 2Cl 3(μ-dppm) 2(CO)(NCMe)]O 3SCF 3 and [Re 2Cl 3(μ-dppm) 2(CO)(NCMe) 2]ReO 4 have shown that the former has the unsymmetrical structure [(MeCN)(CO)ClRe(μ-dppm) 2ReCl 2] + with a ReRe bond (ReRe distance 2.2881(7) Å), while the bis-nitrile complex is the edge-sharing bioctahedron [(MeCN)ClRe(μ-Cl)(μ-CO)(μ-dppm) 2ReCl(NCMe)] +, with an all- cis arrangement of the μ-CO and two MeCN ligands and a ReRe bond (ReRe distance 2.5669(4) Å). The species [Re 2X 3(μ-dppm) 2(CO)(NCMe)] + and [Re 2X 3(μ-dppm) 2(CO)(NCMe) 2] + readily interconvert upon the addition or loss of an acetonitrile ligand and, along with their benzonitrile analogues, they react with halide, XylNC and acetylene to afford Re 2X 4(μ-dppm) 2(CO), [Re 2X 3(μ-dppm) 2(CO)(CNXyl) 2]Y and [Re 2X 3(μ-dppm) 2(CO)(η 2-C 2H 2)]Y, respectively.