Abstract
The reactions of 2-amino-anthracene with [Os(3)(CO)(10)(CH(3)CN)(2)] have been studied and the products structurally characterized by spectroscopic, X-ray diffraction, photophysical and electrochemical techniques. At room temperature in CH(2)Cl(2) two major, isomeric products are obtained [Os(3)(CO)(10)(μ-η(2)-(N-C(1))-NH(2)C(14)H(8))(μ-H)] (1, 14%) and [Os(3)(CO)(10)(μ-η(2)-(N-C(3))-NHC(14)H(9))(μ-H)] (2, 35%) along with a trace amount of the dihydrido complex [Os(3)(CO)(9)(μ-η(2)-(N-C(3))-NHC(14)H(8))(μ-H)(2)] (3). In refluxing tetrahydrofuran only complexes 2 and 3 are obtained in 24% and 28%, respectively. A separate experiment shows that complex 1 slowly converts to 2 and that the rearrangement is catalyzed by adventitious water and involves proton transfer to the anthracene ring. Complex 1 is stereochemically non-rigid; exhibiting edge to edge hydride migration while 2 is stereochemically rigid. Complex 3 is also stereochemically non-rigid showing a site exchange process of the magnetically nonequivalent hydrides typical for trinuclear dihydrides. Interestingly, 2 decarbonylates cleanly to the electronically unsaturated 46e(-) cluster [Os(3)(CO)(9)(μ(3)-η(2)-(N-C(3))-NHC(10)H(9))(μ-H)] (4, 68%) in refluxing cyclohexane, while photolysis of 2 in CH(2)Cl(2) yields only a small amount of 3 along with considerable decomposition. The mechanism of the conversion of 1 to 2 and the dependence of the product distribution on solvent are discussed. All four compounds are luminescent with compounds 1-3 showing emissions that can be assigned to radiative decay associated with the anthracene ligand. Complexes 1-3 all show irreversible 1e(-) reductions in the range of-1.85-2.14 V while 4 shows a nicely reversible 1e(-) wave at-1.16 V and a quasi-reversible second 1e(-) wave at-1.62 V. Irreversible oxidations are observed in the range from +0.35 to +0.49 V. The relationship between the cluster ligand configurations and the observed electrochemical and photochemical behavior is discussed and compared with that of the free ligand.