The Fe(TPA) (TPA = tris(pyridyl-2-methyl)amine) class of non-haem Fe catalysts is proposed to carry out selective hydrocarbon oxidations through the generation of high-valent iron species. Using ambient mass spectrometry, we obtain direct evidence for the formation of an Fe(O)(OH) species under catalytic conditions. In addition, O-labelling suggests that this Fe(O)(OH) species serves as the active oxidant in hydrocarbon oxidation catalysis.
Anionic [2]pseudorotaxanes have been prepared by threading an axle consisting of two dithiophosphonate donor groups attached to a 1,4,5,8-naphthalenediimide (NDI) core through the cavity of the bis-1,5-(dinaphtho)-38-crown-10 ether (15DN38C10). The subsequent coordination of these interlocked, negatively charged species to R 3 SnCl (R = Me, Ph) and (Ph 3 P) 2 CuNO 3 yields neutral (pseudo)rotaxanes of the general formula NDI[(CH 2 CH 2 O) n (An)PS 2 "M"] 2 ⊂ 15DN38C10 (n = 1, 2; An = anisole; "M" = R 3 Sn or (Ph 3 P) 2 Cu). Solution and solid state studies of the rotaxanation process show that there are two factors influencing the interaction between the axles and the wheel: the size of the stopper and the length of the side-arms of the axles. When the axle termini are bulky enough to prevent threading, the length of the side-arms has little influence over the self-assembly process. In contrast, when the size of the stopper does not preclude the threading of the axle through the cavity of the crown, the length of the side-arms is the determining factor in the rotaxanation process. These results presented here provide an alternative method for the synthesis of counter-ion free interlocked species, based on anionic axles with donor capabilities that would produce a neutral interlocked architecture upon threading and coordination to cationic metal-containing centers.
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