Addition and/or oxidation in the reaction of a tricobalt cluster with silver(I) salts: synthesis, structure and solution properties of [Co3Cp3(μ3-CPh)2{μ-Ag(X)}] (X=CF3CO2, NO3) and [Co3Cp3(μ3-CPh)2{μ-Ag(NCMe)}]PF6

Reactions of the benzylidyne-capped tricobalt cluster [Co3Cp3(μ3-CPh)2] (1) with various silver salts have been examined. The salts of weakly- or non-coordinating anions (e.g., BF4− and PF6−) oxidize 1 in CH2Cl2 to form its cationic radical, 1+. Reactions with salts of strongly coordinating anions (e.g., CF3CO2− and NO3−) yield the silver(I) adducts of 1, [Co3Cp3(μ3-CPh)2{μ-Ag(X)}] (for X=CF3CO2−: 2 and NO3−: 3). Even with AgBF4 or AgPF6, the reaction in MeCN produces a silver(I) adduct, [Co3Cp3(μ3-CPh)2{μ-Ag(NCMe)}]+ (4+). The Co3Ag skeleton in the structures of 2, 3, and 4+ is similar in each compound. The Co–Co bond bridged by the Ag atom (for 2, Co–Co=2.4785(8) Å, for 3, Co–Co=2.4837(9) Å, and for 4+, Co–Co=2.4578(7) Å) is longer than the average Co–Co bond length in 1 where 〈Co–Co〉av=2.382(8) Å. The other Co–Co bonds in the compounds are slightly shorter than those in 1. The Co2Ag triangle is not coplanar with the Co3 triangle; the dihedral angles between these triangles for 2, 3 and 4+ are 162.7°, 157.7°, and 151.6°, respectively. Dissolution of 4PF6 in CH2Cl2 leads to the formation of 1+ and the deposition of Ag metal. The 1H NMR spectra of 2 and 3 in CD2Cl2 indicate that the AgX group moves over the three Co–Co bonds. The ESR spectra in frozen acetonitrile solutions of 2, 3, and 4PF6 show the existence of a small amount of 1+, but the deposition of Ag metal was not observed.