Compounds with two metal-metal multiple bonds: New ways of making doubletsinto cyclic quartets

New types of products obtained by combining two dinuclear multiply metal-me tal bonded species (doublets) to obtain cyclic tetranuclear products (quart ets) are reported. One new type consists of pairs of quadruply bonded Mo-2( 4+) units united by two mu-X links (X = H, OH, O) although in the last case oxidation has also occurred so that these are Mo-2(5+) moieties. In these cases, the subunits are Mo-2(DArF)(3). The second new type consists of Mo-2 (DArF)(2) subunits linked by four mu-X bridges,where X = Cl, Br, I. The pre viously known compound Mo4I8(PBu3n)(4) has been shown to differ from all pr eviously known Mo4X8(PR3)(4) molecules (X: = Cl, Br) by retaining two quadr uple bonds instead of beings metallacyclobutadiyne, as are the others.