Protonation of metal–metal bonds: X-ray crystal structures of the complex salts [Ru2(CO)4(μ-H)(μ-Cl)(μ-PtBu2)(μ-Ph2PCH2PPh2)][BF4] and [M2(CO)4(μ-H)2(μ-PtBu2)(μ-Ph2PCH2PPh2)][BF4] (M=Fe, Ru)

Addition of tetrafluoroboric acid to the coordinatively unsaturated species [M2(CO)4(μ-H)(μ-PtBu2)(μ-dppm)] (MM) (M=Fe, 1; M=Ru, 2; dppm=Ph2PCH2PPh2) in diethylether results in rapid protonation of the dimetal vector to give the corresponding complex salts [M2(CO)4(μ-H)2(μ-PtBu2)(μ-dppm)][BF4] (1a and 2a) in nearly quantitative yield. In the same manner [Ru2(CO)4(μ-Cl)(μ-PtBu2)(μ-dppm)] (3) is protonated to yield [Ru2(CO)4(μ-H)(μ-Cl)(μ-PtBu2)(μ-dppm)][BF4] (3a). In order to show the acid–base character of these reactions 1a, 2a, 3a and [Ru2(CO)4(μ-H)(μ-NO)(μ-PtBu2)(μ-dppm)][BF4] (4a) were deprotonated by the base 1,8-diazabicyclo[5.4.0]undec-7-ene DBU to regenerate 1, 2, 3 and the novel complex [Ru2(CO)4(μ-NO)(μ-PtBu2)(μ-dppm)] (4), respectively. The molecular structures of 1a, 2a, 3a and 4 have been established by single-crystal X-ray structure analysis. Upon protonation in each case the metal–metal distance is reduced.