No abstract

No abstract

Reaction of Fe 2 (CO) 9 at room temperature in THF or toluene with the R-imino esters (L) R 1 NdC(R 2 )C(R 3 )dO (a-i; R 1 ) alkyl, R 2 ) H, R 3 ) O-alkyl), results in the formation of several mono-and binuclear complexes, depending on the bulkiness of the R 1 substituent. With all ligands employed, the known type of complex Fe 2 (CO) 6 (L) (6) is formed. Reaction of the less bulky R 1 substituted ligands a-e (R 1 ) neo-Pe, i-Pr, 1-cyclohexylethyl) leads to the formation of Fe(CO) 2 (σ(N):as a mixture of two noninterconverting isomers together with the known type of complexes Fe 2 (CO) 6 (L-L) (7). Complexes 7 contain two (former) R-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):). 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 Fe 2 (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 R 1 ligands f-i (R 1 ) t-Bu, 2-methyl-2-butyl) results in the formation of the new binuclear complexes Fe 2 (CO) 5 (L-L) (12) in which, like in 7, two R-imino ester ligands are C-C coupled on the imine carbon atoms. In contrast to 7, the CdO 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, 1 H and 13 C 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.

The reaction of Fe2(CO)9 at room temperature in THF or toluene with the α‐imino ketones R1N=C(R2)–C(R3)=O (L) (R1 = alkyl, R2 = H, Me, Ph, R3 = Me, Ph) (a–k), initially results in the formation of the mononuclear chelate Fe(CO)3(α‐imino ketone) complexes 6 which can be isolated in moderate (6h) to high (6e–g) yield. Under these reaction conditions, complexes 6 subsequently react with [Fe(CO)4] fragments or dimerise, to form the dinuclear complexes Fe2(CO)6(α‐imino ketone) (7a–j) or Fe2(CO)4(L–L) (8a,b,k), respectively. The complexes 8 contain two α‐imino ketone ligands C–C coupled at the ketone carbon atoms. Complexes 8a,b react with CO at elevated temperatures to quantitatively yield Fe(CO)3(α‐imino ketone) (6a,b). This reaction can be reversed photochemically. Irradiation of a solution of 6a,b in the low‐energy band results in the reformation of 8a,b in almost quantitative yield. The extremely air‐sensitive complexes 6 and the dinuclear complexes 7 and 8 have been characterised spectroscopically (IR, UV/Vis, 1H and 13C NMR) and by elemental analysis. The solid state structures of complexes 6g and 8a have been determined by single‐crystal X‐ray diffraction. The molecular structure of 6g confirms the flat σ‐O,σ‐N chelate coordination of the α‐imino ketone. The structure of 8a consists of two metal–metal‐bonded Fe(CO)2 units, bridged by a formally 10e‐donating dianionic C–C coupled (tBu‐ADO) ligand. A mechanism for the formation of complexes 8 is discussed.

No abstract