CLUSTER CHEMISTRY .75. TETRA-NUCLEAR, PENTA-NUCLEAR AND HEPTA-NUCLEAR CLUSTERS DERIVED FROM (RU4(MU-H)4(CO)11)2(MU-DPPA) [DPPA = C2(PPH2)2] - X-RAY STRUCTURES OF RU4(MU-H)[MU-3-HC2PPH2(RU4(MU-H)4(CO)11)](MU-PPH2)(MU-CO)(CO)9 AND RU7(MU-H)3(MU-5-HC2PPH2)(MU-PPH2)(CO)16

The reaction between C2(PPh2)2 and Ru4(mu-H)4(CO)12 gave {Ru4(mu-H)4(CO)11}2{mu-C2(PPh2)} (1), which on heating formed initially the hydrido-mu-3-alkyne bis-Ru4 cluster Ru4(mu-H)[mu-3-HC2PPh2{Ru4(mu-H)4(CO)11}](mu-PPh2)(mu-CO)(CO)9 (2) (by cleavage of a P-C(sp) bond in 1 and addition of one cluster H atom to the resulting acetylide), followed by the novel Ru7 cluster Ru7(mu-H)3(mu-5-HC2PPh2)(mu-PPh2)(CO)16 (3). The core in 3 has a new geometry, consisting of an Ru4 tetrahedron sharing an apical Ru atom with a C2Ru4 octahedron; there is a further peripheral Ru-Ru interaction linking the two cluster components. By conventional electron counting, 3 is a 108 CVE cluster. Two other minor products isolated from the reaction were Ru5(mu-4-PPh)(CO)15-3n(eta-C6H5Me)n (n = 0 and 1).