Bimetallic Fe–Cu Carbido Carbonyl Clusters Obtained from the Reactions of [Fe4C(CO)12Cu(MeCN)2] with N-Donor Ligands

The reaction of [Fe4C(CO)(12){Cu(MeCN)}(2)] (1) with 3 equivalents of L-L (phen or Me(2)phen) affords [Cu(L-L)(2)][Fe4C(CO)(12){Cu(L-L)}] (L-L = phen, 2; Me(2)phen, 3) in good yields. These are protonated by strong acids resulting in [HFe4C(CO)(12){Cu(L-L)}] (L-L = phen, 4; Me(2)phen, 5). The reaction may be reversed with bases, resulting in the quaternary ammonium salts [NR4][Fe4C(CO)(12){Cu(phen)}] (6). 4 and 5 react with a slight excess of L-L resulting in the elimination of copper in the form of [Cu(L-L)(2)](+) and formation of the previously reported [HFe4C(CO)(12)](-) homometallic cluster. Conversely, the reaction of 1 with a monodentate N-ligand such as quinoline, even if used in large excess, results in the substitution product [Fe4C(CO)(12){Cu(quinoline)}(2)] (8), which is then transformed into [Cu(Me(2)phen)(2)] [Fe4C(CO)(12){Cu(quinoline)}] (9) after reaction with Me(2)phen. By using the anionic cluster [Fe5C(CO)(14){Cu(MeCN)}](-) instead of the neutral 1, only substitution has been observed by using both phen and quinoline, resulting in [Fe5C(CO)(14){Cu(phen)}](-) (10) and [Fe5C(CO)(14){Cu(quinoline)}](-) (11), respectively. Finally, the reaction of 1 with [Ru(tpy)(bpy)(N4C-C6H4-CN)]Cl affords crystals of [Fe4C(CO)(12)Cu2Cl{Ru(tpy)(bpy)(N4C-C6H4-CN)}] (12). All compounds 2-12 have been characterized by a combination of spectroscopic (IR, NMR) and crystallographic methods. All these clusters may be viewed as composed by a butterfly [Fe4C(CO)(12)](2-) core bonded to Cu(I) fragments and/or H+ ions.