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

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