Protonation of metal-metal bonds:: X-ray crystal structures of the complex salts [Ru2(CO)4(μ-H)(μ-PtBu2) (μPh2PCH2PPh2)][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 [M-2(CO)(4)(mu -H)(mu -(PBu2)-Bu-t)(mu -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 [M-2(CO)(4)(mu -H)(2)(mu -(PBu2)-Bu-t)(mu -dppm)][BF4] (1a and 2a) in nearly quantitative yield. In the same manner [Ru-2(CO)(4)(mu -Cl)(mu -(PBu2)-Bu-t)(mu -dppm)] (3) is protonated to yield [Ru-2(CO)(4)(mu -H)(mu -H)(mu -(PBu2)-Bu-t)(mu -dppm)][BF4] (3a). In order to show the acid-base character of these reactions 1a, 2a, 3a and [Ru-2(CO)(4)(mu -H)(mu -NO)(mu -(PBu2)-Bu-t)(mu -dppm)][BF4 (4a) were deprotonated by the base 1,8-diazabicyclo[5.4.0]undec-7-ene DBU to regenerate I, 2, 3 and the novel complex [Ru-2(CO)(4)(mu -NO)(mu -(PBu2)-Bu-t)(mu -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. (C) 2001 Elsevier Science B.V. All rights reserved.