The substitution of carbonyl ligands in the edge-shared bioctahedral cluster [PPN]2[Ru10C2-(CO)24] by two types of 4e donor π-bonding ligands, viz., a diene (norbornadiene) and an alkyne (diphenylacetylene), has been investigated under various conditions. The reaction of [PPN]2[Ru10C2(CO)24] with norbornadiene (NBD) in diglyme at 140°C has provided the anionic derivative [PPN]2[Ru10C2(CO)22(NBD)] (1). Oxidation of this compound with [Cp2-Fe][BF4] affords the neutral derivative Ru10C2(CO)23(NBD) (2), which can also be prepared by direct oxidative substitution of [Ru10C2(CO)24]2- with 2[Cp2Fe][BF4] in the presence of NBD. Spectroscopic and crystallographic studies of 1 and 2 show that the NBD ligand occupies a chelating position on one of the "outer" ruthenium atoms in the bifurcated Ru10C2 framework. This location contrasts with that adopted by the alkyne ligand in both [PPN]2-[Ru10C2(CO)22(C 2Ph2)] (3) and Ru10C2(CO)23(C2Ph2) (4). In these derivatives the alkyne moiety is located in an "inner" site bridging two apical ruthenium atoms. The generality of these substitution sites was probed by preparing the mixed ligand derivative Ru10C2(CO)21(NBD)(C2-Ph2) (5). This compound can be synthesized in four distinct ways: (1) by oxidation of 1 with 2[Cp2Fe][BF4] in the presence of C2R2; (2) by oxidation of 3 with 2[Cp2Fe][BF4] in the presence of NBD; (3) by substitution of two carbonyl ligands in 2 by C2R2 in refluxing toluene; and (4) by substitution of two carbonyl ligands in 4 by NBD in refluxing toluene. The substitution sites observed for the individual ligands are maintained in the mixed ligand derivative. The new compounds were characterized by analytical and spectroscopic methods including negative ion FAB mass spectroscopy and 1H NMR spectroscopy as well as by X-ray crystallographic studies of compounds 2 and 5.
|Number of pages||6|
|Publication status||Published - 1998 Sep 28|
ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry