We have studied the reactions of iron atoms and clusters with oxygen, acetylene, and water molecules in superfluid He droplets at T = 0.37 K. For all systems, the formation of weakly bound adducts was found, but the insertion reaction of iron into existing molecular bonds could not be observed. The formation of FeOH2 and FeC2H2 complexes was evidenced by mass spectrometry. However, it was found that the reaction of iron atoms with oxygen molecules under similar conditions leads to the stabilization of an intermediate reaction product, the weakly bound linear FeOO adduct, which undergoes complete dissociation upon electron impact ionization. All reactions observed are not expected to proceed in the gas phase. The R2PI spectrum of the y(5)D(4)(0)<- a(5)D(4) atomic transition of Fe solvated in helium droplets was recorded. A relatively small blue shift of similar to 120 cm(-1) with respect to the gas phase position was found.