The reaction of W-2(OOCCF3)(4) with (CO)(9)Co3CCOOH and Na[OOCCF3] in a nonpolar solvent mixture leads to the formation of the cluster of clusters {[Na][W-2{OOCCCo3(CO)(9)}(2)(OOCCF3)(4)(THF)(2)]}(2), 1, in 40% yield. The structure of 1 . 3C(6)H(5)CH(3) in the solid state corresponds to a dimer of W-2 dinuclear complexes (monoclinic P2(1)/c, a = 15.234(6) Angstrom, b = 23.326(11) Angstrom, c = 20.658(7) Angstrom, beta = 102.46(3)degrees; V = 7,168(5) Angstrom(3); Z = 4; R(F) = 8.39%). Each W-2 unit is bridged by two cis cluster carboxylates, and the remaining four equatorial sites are occupied by monodentate [OOCCF3](-) ligands. The axial positions contain coordinated THF. The W-2 carboxylate is opened up (W-W distance of 2.449(2) Angstrom) so that the free ends of the [OOCCF3](-) ligands on both W-2 carboxylate units can cooperate in chelating two Na+ ions thereby forming a dimer of W-2 complexes. A distinctive EPR spectrum with g = 2.08 is consistent with each W-2 carboxylate being a mixed-valent W(II)-W(III) species. The reaction of W-2(OOCCF3)(4) with (CO)(9)Co3CCOOH in THF in the absence of Na[OOCCF3] leads to the expected diamagnetic W(II)-W(II) cluster carboxylate W-2{OOCCCo3(CO)(9)}(3)(OOCCF3)(THF)(2), 3.