Compounds with Two Metal−Metal Multiple Bonds: New Ways of Making Doublets into Cyclic Quartets

New types of products obtained by combining two dinuclear multiply metal−metal bonded species (doublets) to obtain cyclic tetranuclear products (quartets) are reported. One new type consists of pairs of quadruply bonded Mo24+ units united by two μ-X links (X = H, OH, O) although in the last case oxidation has also occurred so that these are Mo25+ moieties. In these cases, the subunits are Mo2(DArF)3. The second new type consists of Mo2(DArF)2 subunits linked by four μ-X bridges, where X = Cl, Br, I. The previously known compound Mo4I8(PBun3)4 has been shown to differ from all previously known Mo4X8(PR3)4 molecules (X = Cl, Br) by retaining two quadruple bonds instead of being a metallacyclobutadiyne, as are the others.