290304-73-3Relevant academic research and scientific papers
Preparation and properties of carbonyliron complexes of 1-aza-4-oxa-1,3-butadiene (α-imino ester). X-ray crystal structures of Fe(CO)2(σ(N): σ(C)-i-PrN(H)C(H)C(O)OEt)2 and Fe(CO)2(σ(N): σ(C)-i-PrN(H)C(H)C(O)OMe)(i-PrN=C(H)C(O)O)
Siebenlist, Ron,Frühauf, Hans-Werner,Vrieze, Kees,Kooijman, Huub,Smeets, Wilberth J. J.,Spek, Anthony L.
, p. 3016 - 3031 (2000)
Reaction of Fe2(CO)9 at room temperature in THF or toluene with the α-imino esters (L) R1N=C(R2)C(R3)=O (a-i; R1 = alkyl, R2 = H, R3 = O-alkyl), results in the formation of several mono- and binuclear complexes, depending on the bulkiness of the R1 substituent. With all ligands employed, the known type of complex Fe2(CO)6(L) (6) is formed. Reaction of the less bulky R1 substituted ligands a-e (R1 = neo-Pe, i-Pr, 1-cyclohexylethyl) leads to the formation of Fe(CO)2(σ(σ(N): σ(C)-i-PrN(H)C(H)C(O)OEt)2 (10a-d/10′a-d) as a mixture of two noninterconverting isomers together with the known type of complexes Fe2(CO)6(L-L) (7). Complexes 7 contain two (former) α-imino ester ligands joined at the imine carbon atoms. In the presence of water, the reaction in THF leads to the formation of Fe(CO)2(σ(N): σ(C)-i-PrN(H)C(H)C(O)OMe)(i-PrN=C(H)C(O)O) (11/11′). The unusual σ(N):σ(C) coordination of the newly formed ligands in 10 and 11 is confirmed by X-ray structure determinations. Thermal or photochemical activation of 7 in toluene leads to the formation of Fe2(CO)4(L-L) (9), and reaction of 7 with HCl leads to displacement of the N-protonated C-C coupled organic compounds 8. Reaction of 9 with CO (1 atm) at room temperature results in the re-formation of 7. Reaction with the bulky substituted R1 ligands f-i (R1 = t-Bu, 2-methyl-2-butyl) results in the formation of the new binuclear complexes Fe2(CO)5(L-L) (12) in which, like in 7, two α-imino ester ligands are C-C coupled on the imine carbon atoms. In contrast to 7, the C=O oxygen atoms in 12 are coordinated, and instead of a metal-metal bond a bridging CO is present. All complexes and the organic products have been characterized by spectroscopy (IR, 1H and 13C NMR, FD/FAB-mass) and by elemental analyses. An explanation for the product distribution and the possible mechanisms for the formation of the complexes is discussed.
