Ground and excited state absorption spectra along with optical limiting measurements have been made on a series of systematically altered organometallic cluster compounds. Measurements using 8 ns pulses at 532 nm on methylene chloride solutions of iron-tricobalt organometallic cluster complexes (70% nominal transmission) show limiting throughputs of 350-700 mJ/cm2 without focusing. The optical limiting properties are shown to be minimally dependent on counter-ion substitution indicating little perturbation in the cluster bonding. Optical limiting is shown to be strongly dependent on ligand substitution. Ground state and excited state absorption spectra reveal broad features indicating the materials can be used as limiters over a large spectral range (>lOOnm) . Temporal pulse narrowing of 8 ns pulses to 5 ns at 532 nm was observed, indicating subnanosecond intersystem crossing. The lifetime of the excited state was determined to be 115 ns, much longer than the pulse length, indicating that efficient limiting occurs for longer pulses. Optimization of optical limiting properties is discussed.