apical ethylidyne group, ^CCH3, is symmetrically connected to the H3Fe3(CO)9 triangular fragment with an average C-Fe distance of 1.947 Á. The C-C bond distance in the ethylidyne group is 1.466 Á. Other bond distances and angles are normal.The tricobalt analogue of I, Co3(CO)9CCH3, a member of a class of compounds that have been extensively studied,*