Mononuclear carbonyls iron pentacarbonyl

The first mononuclear carbonyl compound of cobalt, iron or manganese known was the pentacarbonyl complex [Fe(CO)5] " with a trigonal-bipyramidal ligand field (see Fig. 2). Though related electroneutral species of cobalt and manganese are not known due to a strict observance of the 18-electron-rule in these cases, the monoanionic manganese derivative fMn(CO)5] has also been described as a trigonal-bipyramidal species. ... 

Preparation of Mononuclear Carbonyls from Iron Pentacarbonyl... 

The reaction of iron pentacarbonyl with l,4-diazabicyclo[2.2.2]-octane with UV irradiation produced the mononuclear iron carbonyl complex 30 (Scheme 28).Subsequent irradiation of 30 with additional Fe(CO)s resulted in a complex with two Fe(CO)4 fragments 31. 

The mononuclear metal carbonyls contain only one metal atom, and they have comparatively simple structures. For example, nickel tetracarbonyl is tetrahedral. The pentacarbonyls of iron, ruthenium, and osmium are trigonal bipyramidal, whereas the hexacarbonyls of vanadium, chromium, molybdenum, and tungsten are octahedral. These structures are shown in Figure 21.1. 

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