Matrix-isolation studies of the reactions of ground- and excited-state atomic iron with cyclopropane

The chemistry of atomic iron reacting with cyclopropane in an argon matrix at 15 K has been investigated. A spontaneous reaction leads to the formatio n of C2H4FeCH2, [Fe(C2H2)][CH4], and a species in which FeH2 is complexed,w ith allene, (FeH2)(H2C=C=CH2). UV photolysis of the matrix resulted in C-H bond activation to give methylvinyliron and ethynyliron hydride, Atomic iro n was observed to form a weakly bound adduct with cyclopropane. This adduct is stable to irradiation using visible light, but UV photolysis led to enh anced absorptions assigned to methylvinyliron, ethynyliron hydride, and met hane. A strongly interacting complex between two cyclopropane molecules and iron was observed. This species exhibits a large carbon-hydrogen frequency shift that is suggestive of an agostic hydrogen interaction. This complex undergoes a photoreaction at lambda greater than or equal to 500 nm to yiel d the disproportionation product Fe(C2H4)(3), isolated for the first time i n an argon matrix. Photolysis of Fe(C2H4)(3) results in the loss of ethylen e to form Fe(C2H4)(2).