Synthesis and reactivity of [Ru{HB(pz)(3)}{P(C6H11)(3)}Cl(OCH2R)] (pz equals pyrazolyl, R=H or Me)

The complex [Ru{HB(pz)(3)}(cod)Cl] 1 (cod = cycloocta-1,5-diene) reacted with P(C6H11)(3) (greater than or equal to 1 equivalent) in boiling dimethylformamide (dmf) to give the highly air-sensitive intermediate [Ru{HB(pz)(3)}{P(C6H11)(3)}Cl(dmf)] which, on exposure to air in either ethanol or methanol as the solvent, was converted to the ruthenium(III) complexes [Ru{HB(pz)(3)}{P(C6H11)(3)}Cl(OCH2R)] (R = Me 2a or H 2b) in good yields. Complex 2b has been characterized by X-ray crystallography. Treatment of 2a or 2b with L = MeCN, pyridine, CO, P(OMe)(3), or PMe3 in CH2Cl2 afforded the (diamagnetic) ruthenium(II) compounds [Ru{HB(pz)(3)}{P(C6H11)(3)}(Cl)L] 3-7. Most remarkably, 2a or 2b reacted also with terminal alkynes HC=R (R = Ph, CO2Et, Bu-n or SiMe3) giving the neutral vinylidene complexes [Ru{HB(pz)(3)}{P(C6H11)(3)}Cl(=C=CHR)] 8-11. Preliminary results of a study of the catalytic activity of 2 are also presented. Thus, 2a and 2b catalysed the dimerization of some terminal alkynes HC=CR (R = Ph, CO2Et or SiMe3).