Coordination of N-methylpyrrolidone to iron(II)

The use of NMP (N -methylpyrrolidone) as a cosolvent has been shown to improve the yield of iron-catalyzed cross-coupling reactions, but surprisingly there are no iron complexes of NMP in the literature. This paper reports two novel NMP complexes of iron(II): Fe3Cl6(NMP)8 and Lt BuFe(NMP)Cl (Lt Bu = bulky β-diketiminate ligand). The X-ray crystal structure of Fe3Cl6(NMP)8 shows an octahedral View the MathML sourceFe(NMP)62+ cation and two tetrahedral FeCl3(NMP)− anions. 1H NMR spectra show that the NMP ligands are labile, exchanging rapidly on the NMR time scale. The β-diketiminate complex has a trigonal pyramidal geometry with the NMP in an axial position. The use of NMP improves the yield of the catalytic cross-coupling of methyl 4-chlorobenzoate and 1-hexylmagnesium bromide using these and other iron complexes as precatalysts.