Photolysis of 3-methyl- and 3-isopropyl-3-ferrocenylcyclopropenes

The photochemistry of 3-methyl- and 3-isopropyl-3-ferrocenylcyclopropenes ( 10 and 11) has been studied. Upon triplet excitation (sensitized irradiatio n) both cyclopropenes are dimerized to a tricyclohexane dimers whereas in t he singlet state (direct irradiation) cyclopropene 10 is converted to 3-fer rocenyl-3-methylidenepropyne and trans-2-ferrocenyl-2-butene indicating tha t there is an intermediate vinyl carbene. Cyclopropene 11 is converted to 1 -ferrocenyl-4,4-dimethylcyclobutene, Direct irradiation of the mixture of 1 1 with 2-ferrocenyl-3-methyl-1-butene leads to the formation of 1,3-diferro cenyl-6,6-dimethyl-3-isopropenylcyclohexene (24). A possible reaction pathw ay via intermediate radicals is discussed. X-ray structural data are presen ted for 3,6-diferrocenyl-3,6-diisopropyltricyclo[3.1.0.0.(2,4)]hexane and c ompound 24. (C) 2000 Elsevier Science S.A. All rights reserved.