Reaction of FcC[triple bond, length as m-dash]CC(O)R (Fc = ferrocenyl) with Ru3(CO)12 leading to unexpected nitro-group reduced ruthenoles and 1,2-CO-inserted triruthenium clusters

Abstract

The reaction of Ru₃(CO)₁₂ with ferrocene-containing alkynyl ketones FcC[triple bond, length as m-dash]CC(O)R (Fc = ferrocenyl; R = Ph (1); 2-thienyl (2); 4-CH₃O-Ph (3); 4-NH₂-Ph (4); 4-NO₂-Ph (5); ferrocenyl (6)) proceeds in toluene with the formation of triruthenium clusters (1a-6a), ruthenoles (1b-5b, 5c and 1d-5d) and unexpected 1,2-CO-inserted triruthenium clusters (1c-4c). 1a-6a were isolated from the reaction of Ru₃(CO)₁₂ with one equivalent of 1-6, respectively. Ruthenoles 1b-5b, 5c and 1d-5d were collected by adding 1-5 to the corresponding 1a-5a in a molar ratio of 1 : 1, respectively. Unexpectedly, the nitro group in one of the two phenyl rings in both 5c and 5d molecules was reduced to an amino group, while their ruthenole skeletons are retained. When 1-4 were added to the corresponding 1a-4a in a molar ratio of 1 : 1, respectively, the unusual triruthenium clusters (1c-4c) were isolated, involving 1,2-insertion of a terminal coordinated carbonyl between two C[triple bond, length as m-dash]C units of the ynone molecules. No reaction between 6a and 6 was observed. And the familiar cyclotrimerization products were not found. All new compounds were characterized by NMR, FT-IR, and MS-ESI and most of them were structurally confirmed by single crystal X-ray diffraction. The results suggested that the ferrocenyl groups in the 1,3-ynones exhibit strong electron and steric effects on the reaction process and product distribution during their reactions with Ru₃(CO)₁₂.