Magnesiation of N‐Methyl‐1, 3‐propylenediaminoboryl Ferrocene

Abstract

AbstractN‐methyl‐1, 3‐propylenediaminoboryl ferrocene (1‐H) was obtained by a three‐step synthesis: i) At first ferrocene was reacted with BBr3 to give dibromoboryl ferrocene (FcBBr2). ii) In a second step FcBBr2 was transformed into FcB(OMe)2 by treatment of FcBBr2 with Me3SiOMe. iii) Finally reaction of FcB(OMe)2 with H2NCH2CH2CH2NMeH yielded the boryl ferrocene 1‐H. In addition we examined the metalation of 1‐H with magnesium 2, 2, 6, 6‐tetramethylpiperidide (TMP) and mixtures of Li(TMP)/Mg(TMP)2. The reaction of 1‐H with 0.5 equivalent of Mg(TMP)2 yielded quantitatively the homoleptic complex Mg[1]2 whereas metalation of 1‐H with 1.5 and 2 equivalents of Mg(TMP)2 gave product mixtures. However, N,N'‐dimethyl‐1, 3‐propylenediaminoboryl ferrocene (1‐Me) and the ortho‐methylated derivatives 2‐Me and 3‐Me (3‐Me bears additionally one Me group in 1′‐postion) could be identified after derivatization with Me2SO4. The metalated ferrocene derivative (Li2(THP)2Mg3(TMP)2[3]2) which is bearing one Li and one Mg atom in the ortho‐position and a further two Mg atoms in N‐ and 1′‐positions, was formed in good yield by treatment of 1‐H with an excess of a 1:2 mixture of Li(TMP) and Mg(TMP)2 in tetrahydropyran (THP). Single crystals of the racemic complex Li2(THP)2Mg3(TMP)2[3]2 were available by gas‐phase diffusion of hexane into a concentrated THP solution at ambient temperature (space group C2/c). The crystal structure of Li2(THP)2Mg3(TMP)2[3]2 displays a racemic dimer of the Rp‐ and the Sp‐enantiomer.