Ruthenium hydrides bearing SbPh3 and AsPh3 ligands: characterization of the bis(dihydrogen) complexes [Cp*Ru(H2)2(EPh3)]+ (Cp*=C5Me5; E=Sb, As)

Reaction of NaBH4 with [Cp*RuCl2(EPh3)] (E=Sb 1a, As 1b) in THF/EtOH affords the trihydride complexes [Cp*RuH3(EPh3)] (E=Sb 2a, As 2b) in good yield. These trihydrides are protonated by HBF4·OEt2 in CH2Cl2 at −80 °C furnishing the cationic bis(dihydrogen) complexes [Cp*Ru(H2)2(EPh3)][BF4] (E=Sb 3a, As 3b), which were characterized in solution by T1 and 1JHD measurements. These species are unstable and decompose at T>0 °C. The reaction of [Cp*RuCl(SbPh3)2] with H2 and NaBAr′4 in fluorobenzene yields the dihydride [Cp*RuH2(SbPh3)2][BAr′4] (5). Protonation of the monohydride [Cp*RuH(SbPh3)2] (6) by HBF4·OEt2 in CH2Cl2 at −80 °C generates the dihydrogen complex [Cp*Ru(H2)(SbPh3)2]+ (7), which rearranges to its dihydride tautomer 5 when the temperature is raised.