Abstract
The reaction of the unsaturated anion [Re3(μ-H)4(CO)10]- with pyrazole (used as solvent at 80 °C) proceeds in a stepwise manner, at first giving the [Re3(μ-H)3(μ-η2-pz)(CO)10]- anion (2, pz = pyrazolate), with H2 evolution. Spectroscopic characterization has shown that 2 contains a pz ligand bridging through the two N atoms, one edge of the triangular cluster. At longer times, CO is evolved and 2 transforms into the novel species [Re3(μ-H)3(μ-η2-pz)(CO)9(Hpz)]- (3), containing one pz ligand bridging a cluster edge and a second pyrazole molecule terminally bonded on the third vertex of the triangle, replacing an axial carbonyl of 2. The treatment with CO (atmospheric pressure, room temperature) slowly restores 2. A single-crystal X-ray analysis of 3 has revealed the syn coordination of the two heterocycles with respect to the metal triangle plane and an intramolecular hydrogen bond between the N−H proton of the pyrazole ligand and the aromatic π-electrons of the bridging pyrazolate. There is NMR evidence t...
Published Version
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