Reactions of the dirhenium(II) complexes [Re2X4(dppm)2](X = Cl or Br, dppm = Ph2PCH2PPh2) with isocyanides. Part 2. The A-frame-like monoisocyanide species [Re2(µ-X)(µ-dppm)2X3(CNR)]n+(R = Me, But, or C6H3Me2-2,6; n= 0 or 1)

The triply bonded complexes [Re2X4(dppm)2](X = Cl or Br, dppm = Ph2PCH2PPh2) react with RNC (R = Me, But, or C6H3Me2-2,6) to yield the monoisocyanide adducts [Re2X4(dppm)2(CNR)]. The spectroscopic properties of these species are in accord with the presence of isomers in solution. Chemical oxidation of the neutral complexes to their corresponding paramagnetic monocations produces a single isomer in each instance. The solid-state structure of [Re2Cl4(dppm)2(CNBut)] has been shown to be that of the A-frame-like molecule [Cl2Re(µ-Cl)(µ-dppm)2ReCl(CNBut)]. The retention of a Re–Re multiple bond is supported by both structural work (Re–Re = 2.30 A) and a qualitative treatment of the bonding which is consistent with the presence of a slightly weakened triple bond.