Linear and bent oxo-bridged dinuclear rhenium(V) complexes with terminal and bridging pyrazole ligands

The [ReOX3(AsPh3)(OAsPh3)] (X = Cl or Br) complexes react with two equivalents of 3,5-dimetylopyrazole (3,5-Me2pzH) in acetone at room temperature to give [{Re(O)X2(3,5- Me2pzH)2}2(μ-O)] (1 and 2). In the case of [ReOBr3(AsPh3)(OAsPh3)], a small quantity of the dinuclear rhenium complex [{Re(O)Br(3,5-Me2pzH)}2(μ-O)(μ-3,5-Me2pz)2] (3) has been isolated next to the main product 2. Treatment of [ReOX3(PPh3)2] compounds with two equivalents of 3,5-Me2pzH in acetone at room temperature leads to the isolation of symmetrically substituted dinuclear rhenium complexes [{Re(O)X(PPh3)}2(μ-O)(μ-3,5-Me2pz)2] (4 and 5). Refluxing of [ReO(OEt)X2(PPh3)2] complexes with 3,5-Me2pzH in ethanol affords unsymmetrically substituted dinuclear rhenium [{Re(O)X(PPh3)}(μ-O)(μ-3,5-Me2pz)2{Re(O)X(3,5- Me2pzH)}] complexes (6 and 7). The complexes obtained in these reactions have been characterised by IR, UV–Vis, 1H and 31P NMR. The crystal and molecular structures have been determined for 1, 2, 3, 4, 6 and 7 complexes.