Clusters Incorporating Core Hypercarbon Atoms

METAL CLUSTERS INCORPORATING CORE HYPERCARBON ATOMS 

The metal-carbon cluster systems we have considered so far in the present chapter, like the carboranes considered in the previous chapter, have contained one or more skeletal carbon atoms occupying vertex sites on the cluster deltahedron or deltahedral fragment. We now turn to some molecular cluster systems in which hypercoordinated carbon atoms occupy core sites in the middle of metal polyhedra. Most are metal carbonyl carbide clusters of typical formulae Mj (CO)yC. Their carbide carbon atoms are incorporated within polyhedra, which in turn are surrounded by y carbonyl ligands. Such compounds, for which few controlled syntheses are available, have been found primarily among the products of thermal decomposition of polynuclear metal carbonyls Mj (CO)j, their carbide carbon atoms result from disproportionation reactions of carbonyl ligands (2 CO CO2 + C). 

Fundamental Polyhedron b Closo Species (a = b - 1) Nido Species (a = fe - 2) Arachno Species (a = fe - 3) 

Octahedron 7 C04(CO)i C2Et2 Fe(CO)3C4H4, 5 CoCpC4H4, and Co(CO)3C3H5 and other r -allyl 

Hexagonal 9 — Cr(C6H6)2, Cr(CO)3(C6H6) and other Hexagonal aromatic rings 

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METAL CLUSTERS INCORPORATING CORE HYPERCARBON ATOMS... 

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