Reactions of the A-frame-like monocarbonyl complexes Re2(μ-X)(μ-dppm)2X3(CO) (X = Cl or Br; dppm = Ph2PCH2PPh2) with trimethylphosphine and trialkylphosphite ligands. The structural characterization of [Re2(μ-Cl)(μ-CO)(μ-dppm)2Cl2(PMe3)2]Cl