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

Abstract

The reactions of the neutral and anionic pyrazolyl-bridged triruthenium clusters [Ru 3(μ-H)(μ-dmpz)(CO) 10]( 1) and (Et 4][Ru 3 (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 [Ru 3(μ-H)(μ-dmpz)(μ-dppm)(CO) 8](3a) and [Et 4N][Ru 3(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 CF 3CO 2H 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 PPh 3 and PHPh 2 at room temperature give [Ru 3(μ-H)(μ-dmpz)(PPh 3)(CO) 9] ( 5) and [Ru 3(μ-H)(μ-dmpz)(PHPh 2)(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 PPh 3 or PHPh 2 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 [Ru 2(μ-dmpz)(μ-PPh 2)(CO) 6](7) and [Ru 3(μ-H)(μ-dmpz)(μ-PPh 2) 2(CO) 7] ( 8) have been isolated from the thermolysis of complex 6.