Unprecedented Linking of Two Polyoxometalate Units with a Metal-Metal Multiple Bond

The reaction of (Bu4N)(2)[Pe(2)Cl(8)] with lacunary Keggin polyoxometalate K-7[PW11O39] in water produces a new dumbbell-shaped heteropolyoxometalate anion, [Re-2(PW11O39)(2)](8-), whose structure contains a central Re-2 core with a quadruple bond between Re atoms (Re-Re 2.25 angstrom), coordinated to two polyoxometalate units. This complex represents the first example of the direct linking of two polyoxometalate units via a metal-metal multiple bond. The compounds were characterized by X-ray analysis, IR, and electrospray ionization mass spectrometry.