Increasing the solubility of strong reducing agents containing Mo ₂⁴⁺ units and alkyl-substituted guanidinate ligands

Six very soluble paddlewheel compounds containing Mo₂ ⁿ⁺ units, n = 4, 5, 6, and two alkyl-substituted bicyclic guanidinate ligands have been synthesized. The quadruply bonded complexes with n = 4, Mo₂(TMhpp)₄ and Mo₂(TEhpp)₄, (TMhpp = the anion of 3,3,9,9-tetramethyl-1,5,7-triazabicyclo[4.4.0]dec-4-ene and TEhpp = the anion of 3,3,9,9-tetraethyl-1,5,7-triazabicyclo[4.4.0]dec-4-ene) are easily oxidized. The electrode potentials in THF are -1.08 and -1.17 V vs. Ag/AgCl, respectively, for the Mo₂^5+/4+ couple. These potentials are in accord with the low ionization potentials for the quadruply bonded compounds. Because of the high solubility of the Mo₂ ⁴⁺ compounds in most common organic solvents they are attractive candidates for use as strong reducing agents in homogeneous systems.