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 la, 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 degreesC furnishing the cationic bis(dihydrogen) complexes [Cp*Ru(H-2)(2)(EPh3)][BF4] (E = Sb 3a, As 3b), which were characterized in solution by T, and (1)J(HD) measurements. These species are unstable and decompose at T > 0 degreesC. The reaction of [Cp*RuCl(SbPh3)(2)] with H-2 and NaBAr4' in fluorobenzene yields the dihydride [Cp*RuH2(SbPh3)(2)][BAr4'] (5). Protonation of the monohydride [Cp*RuH(SbPh3)(2)] (6) by HBF4.OEt2 in CH2Cl2 at -80 degreesC generates the dihydrogen complex [Cp*Ru(H-2)(SbPh3)(2)](+) (7), which rearranges to its dihydride tautomer 5 when the temperature is raised. (C) 2002 Elsevier Science B.V. All rights reserved.