ChemInform Abstract: High Nuclearity Clusters and Beyond

Abstract

Abstract Separate series of neutral and anionic osmium carbonyl clusters based on 3–20 osmium atoms have been prepared and characterised in the solid by single crystal X-ray analysis and in solution largely by 13 C NMR spectroscopy and vibrational analysis (IR). They appear to fall into two distinct series, viz ., those which follow a polytetrahedral, non-metallic growth sequence, e.g. [Os 3 (CO) 12 ] and [Os 3 (CO) 11 ] 2− , [Os 4 (CO) 14 ] and [Os 4 (CO) 13 ] 2− , [Os 5 (CO) 16 ] and [Os 5 (CO) 15 ] 2− , and [Os 6 (CO) 18 ] and [Os 6 (CO) 17 ] 2− , and those which apparently follow the route to bcc packing, e.g. [Os 6 (CO) 18 ] 2− , [Os 7 (CO) 21 ] and [Os 7 (CO) 20 ] 2− , [Os 8 (CO) 23 ] and [Os 8 (CO) 22 ] 2− , [Os 9 (CO) 24 ] 2− , [Os 10 (CO) 26 ] 2− and [Os 10 C(CO) 24 ] 2− , and [Os 20 (CO) 40 ] 2− . Alternatively, the species [Os 4 (CO) 14 ] and [Os 4 (CO) 13 ] 2− , [Os 10 (CO) 26 ] 2− and [Os 10 C(CO) 24 ] 2− and [Os 20 (CO) 40 ] 2− may be viewed as forming a ‘magic number’ sequence of clusters corresponding to the tetrahedral growth pattern, viz . 4, 10, and 20. Also described are the syntheses of mixed Os-C and Os-Hg clusters. The former bear a close resemblance to the carboranes in their structural features, whereas the Os-Hg clusters represent examples of linked cluster systems containing both transition metal and main group cluster domains. The geometric relevance that all these structures bear to the ‘metallic state’ is discussed.