A bicarbonate bridged diruthenium(I) complex: Key evidence for the decarboxylation step in the base-assisted reduction of Ru2Cl4(CO)6

Base-assisted reduction of [Ru(CO)3Cl2]2 in the presence of NP-Me2 (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru2(CO)4Cl2(NP-Me2)2] (1). Two NP-Me2 and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru–Ru single bond. Reaction of [Ru(CO)3Cl2]2, TlOTf, KOH and NP-Me2 in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru2(CO)2(μ-CO)2(μ-O2COH)(NP-Me2)2](OTf) (2). The in situ generated CO2 is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [RuII(CO)3Cl2]2 → [RuI2(CO)4]2+.