Complex sentence: Methylcyclopentadienyl manganese tricarbonyl (MMT) is a gasoline additive used to replace lead for unleaded gasolines, and functions as an antiknock agent by raising the octane ratings of gasoline.
Split into simpler sentences: Methylcyclopentadienyl manganese tricarbonyl (MMT) is a gasoline additive. MMT is a lead replacement for unleaded gasolines and functions as an anti-knock agent by raising the octane ratings of gasoline.