A new dirbenium complex with an unsupported bridging hydride ligand

The reaction of Re₂(CO)₈(μ-H)2 with CH₂(NMe₂)₂ in chloroform at 25°C yielded the new compound Re₂(CO)₈(NHMe₂)(Cl)(μ-H) (1) in 31% yield. Compound 1 was characterized by IR, ¹H NMR and a single-crystal X-ray diffraction analysis. Crystal data: orthorhombic, Pbca, a = 13.787(4), b = 19.884(5), c = 12.296(2) Å. Solution by direct methods (MITHRIL), R = 0.035 for 1800 reflections. The complex contains two rhenium atoms linked by an unsupported hydride bridge, Re Re = 3.362(1) Å, Re(1)---H = 1.8(1) Å and Re(2)---H = 2.0(1) Å. A chloride ligand abstracted from the solvent is terminally bonded to Re(1), and a dimethylamine ligand abstracted from the CH₂(NMe₂)₂ is coordinated to Re(2). When heated to 68°C, the dimethylamine ligand was eliminated and the chloride ligand became a bridge in the new compound Re₂(CO)₈(μ-H)(μ-Cl) (2), yield 76%.