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- Title
The series Os<sub>4</sub>(µ<sub>x</sub>-η<sup>2</sup>-C<sub>2</sub>Ph<sub>2</sub>)(CO)<sub>14–</sub><sub>n</sub> (n = 0, 1, 2; x = n + 2) — Models for site-specific surface catalysts.
- Authors
Canal, John P.; Jennings, Michael C.; Yap, Glenn P.A.; Pomeroy, Roland K.
- Abstract
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) Å) and a flat butterfly Os4 unit (Os—Os range = 2.859(2)–2.916(2) Å). 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) Å) 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 the C2Ph2 bound to all four metal atoms (Os—Os range = 2.7457(5)–2.8742(5) Å). The 13C{1H} NMR spectra of 3 at 21 and 90 °C indicate there is rapid CO exchange of the carbonyls of the two types of Os(CO)3 units, but not between the units. The spectrum at –90 °C indicates one of the rotations (presumed to be that involving the carbonyls of the wingtip Os(CO)3 units) is slowed on the NMR timescale. Compounds 1–3 form a unique series of clusters that have an alkyne ligand bound to two, three, and four metal atoms. Compound 1 is a model for a corner, compound 2 for a planar surface, and compound 3 a step site, in site-specific surface catalysts.
- Subjects
OSMIUM compounds; CARBONYL compounds; CATALYSTS; NUCLEAR magnetic resonance spectroscopy; LIGANDS (Chemistry)
- Publication
Canadian Journal of Chemistry, 2006, Vol 84, Issue 2, p176
- ISSN
0008-4042
- Publication type
Article
- DOI
10.1139/V05-239