The series Os4(µx-η2-C2Ph2)(CO)14n (n = 0, 1, 2; x = n + 2) Models for site-specific surface catalysts

The cluster Os4(µ-η2-C2Ph2)(CO)14 (1) has been prepared from the reaction of Os4(CO)14 and C2Ph2 in CH2Cl2 at 25 °C. Other minor products include the known clusters Os3(µ3-η2-C2Ph2)(CO)10 and Os3(µ-η4-C4Ph4)(CO)9. The structure of 1 reveals an approximately planar C2Os4 skeleton with a dimetallacyclobutene ring (C—C = 1.32(4) A) and a flat butterfly Os4 unit (Os—Os range = 2.859(2)–2.916(2) A). The 13C{1H} NMR spectrum of 1 indicates the carbonyl ligands are rigid at room temperature. Stirring 1 in CH2Cl2 for 2 days (ambient temperature) afforded Os4(µ3-η2-C2Ph2)(CO)13 (2). The Os atoms in 2 also have an almost flat butterfly arrangement (Os—Os range = 2.7392(7)–2.8947(6) A) with the alkyne ligand located over one of the Os3 triangles. The 13C NMR data for 2 are consistent with rapid rotation on the NMR timescale of the hinge Os(CO)3 units at 21 °C, but slow rotation at –50 °C. Heating 2 at 40 °C gave Os4(µ4-η2-C2Ph2)(CO)12 (3) after 2 days. Cluster 3 has the common butterfly arrangement of Os atoms with ...