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)2and Fe(CO)2(σ(N): σ(C)-i-PrN(H)C(H)C(O)OMe)(i-PrNC(H)C(O)O)

Abstract

Reaction of Fe2(CO)9 at room temperature in THF or toluene with the α-imino esters (L) R1NC(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(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-PrNC(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 tol...