Quadruply bonded metal complexes of rhenium and molybdenum have been prepared with tetrachlorocatechol. Structural characterization on the [Re-2(Cl(4)Cat)(4)](2-) anion has shown that it consists of distorted square-planar Re(Cl(4)Cat)(2) units linked by a short (2.2067 angstrom) quadruple Re-Re bond. The addition of tetrachlorocatechol to molybdenum acetate was used to prepare the isoelectronic molybdenum analogue "[Mo-2(Cl(4)Cat)(4)](4-)". This complex was found to be far more reactive than the rhenium dimer. A dimer containing a Mo-Mo double bond, [(Cl(4)Cat)(2)Mo(mu-O)(mu-OCH3)Mo(Cl(4)Cat)(2)](3-), was obtained as the methanolysis product of the complex formed initially, and the oxomolybdenum(V) monomer [MoO(Cl(4)Cat)(2)](-) was formed under more oxidative conditions. Both complexes are oxygen-sensitive, giving [MoO2(Cl(4)Cat)(2)](2-) as the final air-stable complex product.