Reactivity of Indene, Fluorene, Azulene, and Acenaphthylene with a Basal-Edge-Bridged Square-Pyramidal Hexaruthenium Dihydride

The basal-edge-bridged square-pyramidal hexanuclear cluster [Ru6(μ3-H)2(μ5-κ2-ampy)(μ-CO)2(CO)14]
(1; H2ampy = 2-amino-6-methylpyridine) reacts with indene in refluxing chlorobenzene to give [Ru7(μ3-H)(μ5-κ2-ampy)(μ-η9-C9H7)(μ-CO)3(CO)11] (2), [Ru6(μ3-H)(μ5-κ2-ampy)(η5-C9H7)(μ3-CO)(μ-CO)2(CO)11] (3), and the known dimer [Ru2(η5-C9H7)2(μ-CO)2(CO)2]. While the indenyl ligand of complex 2
is η5:η6 edge bridging, complex 3 has a terminal η5-indenyl ligand. The hexanuclear η6-fluorene derivative
[Ru6(μ3-H)2(μ5-κ2-ampy)(η6-C13H10)(μ-CO)2(CO)11] (4) has been isolated from a reaction of compound
1 with fluorene in decane at reflux temperature. Under analogous conditions, azulene reacts with 1 to
give [Ru6(μ5-κ2-ampy)(μ3-η10-C10H8)(μ-CO)2(CO)10] (5) and [Ru4(μ3-η10-C10H8)(CO)9] (6). In both
complexes, the azulene ligand is attached to three Ru atoms through its ten C atoms. Four complexes
have been isolated from reactions of acenaphthylene with complex 1 in refluxing decane:  [Ru4(μ4-κ2-ampy)(μ-η6-C12H8)(μ-η4-C12H8)(μ-CO)2(CO)5] (7), [Ru6(μ4-κ2-ampy)(μ3-η10-C12H8)(CO)12] (8), [Ru7(μ5-κ2-ampy)(μ4-η12-C12H8)(μ-CO)(CO)12] (9), and [Ru6(μ4-κ1-ampy)(μ4-η12-C12H8)(μ-CO)2(CO)9] (10). These
compounds do not maintain the metallic skeleton of the starting complex 1 and contain acenaphthylene
ligands that display unprecedented coordination modes, such as η5:η1 edge bridging (7), η2:η2 edge bridging
(7), η6:η5:η1 triangular face capping (8), and η5:η3:η2:η2 quadruply bridging (9 and 10). The coordination
mode of the ampy ligand of compound 10, which has a μ4-imido fragment and an uncoordinated pyridyl
group, is also unprecedented. The high temperatures required by all these reactions promote cluster
decarbonylation processes. This accounts for the observation that, with few exceptions (3, 4, 7), most of
the reaction products contain the polycyclic hydrocarbon ligands attached to various metal atoms through
many carbon atoms.