Amine attack on the carbonyl ligands of the protonated dicyclopentadienyl-bridged diruthenium complex [{(η5-C5H3)2(SiMe2)2}Ru2(CO)4(μ-H)]+

Complexes [{(eta (5)-C5H3)(2)(SiMe2)(2))Ru-2}(CO)(4)(mu -H)](+) (1H(+)BF(4)(-), 1D(+)TfO(-)), with a protonated Ru-Ru bond, were prepared by protonation of {(eta (5)-C5H3)(2)(SiMe2)(2)}Ru-2(CO)(4) (1) With HBF4. Et2O or CF3SO3D. The bridging proton in 1H(+) is removed oily very slowly by amine bases even though it is thermodynamically acidic (pK(a)(AN) = 6.5 (+/-0.2)). This-remarkable kinetic inertness of the bridging proton allows amines (NH3-, NH2CH3, NH(CH3)(2), morpholine, piperidine, pyrrolidine) to react with 1H(+) by attacking the CO ligand to give a formamide (HC(=O)NR2) and the CO-substituted product {(eta (5)-C5H5)(2)(SiMe2)(2)}Ru-2(CO)(3)(NMR2) (2) Thus, protonation of the metal-metal bond in 1H(+) promotes reactions of the CO ligand that are not possible;ip the unprotonated 1. A proposed mechanism for these reactions is supported by kinetic studies of the reaction of 1D(+)TfO(-) with morpholine in nitromethane at 20.0 degreesC, as well as by deuterium-labeling experiments. The molecular structure of {(eta (5)-C5H3)(2)-(SiMe2)(2)}Ru-2(CO)(3)(NH2CH3) (2f), as determined by an X-ray diffraction investigation, is also presented.