Neutral and anionic pyrazolyl-bridged triruthenium carbonyl cluster complexes. Reactions with bis( diphenylphosphino) methane, triphenylphosphine and diphenylphosphine

Article abstract of DOI:10.1016/0022-328X(96)06152-9

The reactions of the neutral and anionic pyrazolyl-bridged triruthenium clusters [Ru₃(μ-H)(μ-dmpz)(CO)₁₀] (1) and [Et₄N][Ru₃(μ-dmpz)(μ-CO)₃(CO)₇] (2) (Hdmpz = 3,5-dimethylpyrazole) with three different phosphine ligands have been studied. Complexes 1 and 2 react with bis(diphenylphosphino)methane (dppm) to give the asymmetric substituted products [Ru₃(μ-H)(μ-dmpz)(μ-dppm)(CO)₈] (3a) and [Et₄N][Ru₃(μ-dmpz)(μ-dppm)(μ-CO)₂(CO)₆] (4) respectively, in which the dppm and pyrazolyl ligands span different Ru-Ru edges. Protonation of the anionic complex 4 with CF₃CO₂H affords the asymmetric neutral hydride 3a. Complex 3a slowly undergoes an isomerization reaction in solution at room temperature to give a symmetric derivative (3b) in which the diphosphine, hydride and pyrazolyl ligands span the same Ru-Ru edge. The reactions of compound 1 with PPh₃ and PHPh₂ at room temperature give [Ru₃(μ-H)(μ-dmpz)(PPh₃)(CO)₉] (5) and [Ru₃(μ-H)(μ-dmpz)(PHPh₂)(CO)₉] (6) respectively. In compounds 5 and 6, the phosphine ligand occupies an equatorial site cis to the pyrazolyl and hydride ligands. The anionic complex 2 does not react with PPh₃ or PHPh₂ at room temperature, but gives mixtures of many products at higher temperatures. Compounds 3-6 are thermally unstable, decomposing in THF at reflux temperature into mixtures of many compounds. The diphenylphosphido derivatives [Ru₂(μ-dmpz)(μ-PPh₂)(CO)₆] (7) and [Ru₃(μ-H)(μ-dmpz)(μ-PPh₂)₂(CO)₇] (8) have been isolated from the thermolysis of complex 6.