Tricobalt Carbonyl Clusters Containing Cn (n = 2, 4, 6) Ligands

Treatment of Co-3(mu(3)-CBr)(mu-dppm)(CO)(7) with zinc dust in refluxing thf afforded Co-6(mu(6)-C-2)(mu-dppm)(2)-(mu-CO)(CO)(12) (5), containing two Co-3 triangles which are linked by a short Co-Co bond and the C-2 ligand. The Pd(0)/Cu(I)-catalyzed reactions of Co-3(mu(3)-CBr)(mu-dppm)(CO)(7) or Co3(mu-CBr)(CO)(9) with Co-3{mu(3)-C(C equivalent to C)(n)Au(PPh3)}(mu-dppm)(CO)(7) (n = 1, 2, respectively) gave {Co-3(mu-dppm)(CO)(7)}(2)(mu(3):mu(3)-CC equivalent to CC) (6) and the unsymmetrical C-6 derivative {(OC)(9)Co-3}{mu(3):mu(3)-C(C equivalent to C)(2)C}{Co-3(mu-dppm)(CO)(7)} (4). The former reacted further with dppm to give {Co-3(mu-dppm)(CO)(7)}(2)(mu(3):mu(3)-CC equivalent to CC)(mu-dppm) (7), in which the two Co-3 clusters are bridged by the third dppm ligand.