A TRIOSMIUM CLUSTER WITH A NOVEL MODE OF METALLACYCLOPENTADIENE FRAGMENT BONDING - X-RAY STRUCTURE AND REACTIVITY OF OS-3(MU-3-ETA(1)-ETA(1)-ETA(2)-ETA(2)-C(SIME(3))C(ME)C(H)C(PH))(CO)(9)

The molecular structure of Os-3{mu(3)-eta(1):eta(1):eta(2):eta(2)-C(SiMe3)C(Me)C(H)C(Ph)}(CO)(9) (3), obtained from Os-3(mu(3)-Me(3)SiC(2)Me)(mu-CO)(CO)(9) (2) and PhC=CH in hot hexane, involves an osmacyclopentadiene ring pi-coordinated to the remaining two osmium atoms of the cluster. Heating of 3 in refluxing benzene yields two new compounds, Os-3-(mu-H){mu(3)-C(SiMe(3))C(Me)C(H)C(C6H4)}(CO)(8) (4) with a rearranged coordinated on one cluster edge osmacyclopentadiene fragment, and Os2{mu-eta(1):eta(1):eta(4)-C(SiMe(3))C-(Me)C(H)C(Ph)}(CO)(6) (5). Compound 4 reacts with PPh(3) at room temperature to form Os-3{mu-eta(1):eta(1):eta(4)-C(SiMe(3))C-(Me)C(H)C(Ph)}(CO)(8)(PPh(3)) (8).