Low coordinate magnesium chemistry supported by a bulky β-diketiminate ligand

A series of magnesium(II) alkyl, alkoxide, carboxylate, amide and halide complexes stabilised by the bulky beta-diketiminate ligand, HC(C(Me)N-2,6-(Pr2C6H3)-Pr-i)(2) (BDI), have been synthesised and structurally characterised. (BDI)H reacts with MgMe2 in Et2O to give the four-coordinate complex (BDI)MgCH3(Et2O), 1, and in toluene to afford [(BDI)Mg(mu-CH3)](2), 2. Three coordinate complexes may be accessed by increasing the size of the alkyl ligand; hence, the reaction of (BDI) H with (Bu2Mg)-Bu-t yields (BDI) (MgBu)-Bu-t, 3, while Li(BDI) reacts with (PrMgCl)-Pr-i to afford (BDI) (MgPr)-Pr-i, 4; a similar reaction with PhMgCl affords the diethyl ether adduct (BDI)MgPh(Et2O), 5. The etherates 1 and 5 may be converted into the base-free complexes, 2 and (BDI)MgPh, 6, respectively, upon heating in vacuo. The direct reaction of (BDI)H with RMgX (X = Cl or Br) results in relatively inert halide-bridged dimers of formula [(BDI)Mg(mu-X)](2), (X = Cl, 7; X = Br, 8). The alkylmagnesium derivatives react readily with alcohols, amines or carboxylic acids to yield alkoxide, amide and carboxylate complexes, respectively. For example, 4 reacts with (PrOH)-Pr-i (or O-2) to form [(BDI)Mg(mu-(OPr)-Pr-i)](2), 9. Convenient one-pot synthetic procedures have been developed using commercially available Bu2Mg. Treatment of Bu2Mg with (BDI)H, followed by its reaction with MeOH, (BuOH)-Bu-t, (Pr2NH)-Pr-i, (Me3Si)(2)NH, MeCO2H or PhCO2H affords [(BDI)Mg(mu-OMe)](2), 10, [(BDI) Mg(mu-(OBu)-Bu-t)](2), 11, (BDI)Mg((NPr2)-Pr-i), 12, (BDI)Mg(NTMS2), 13, [(BDI)Mg([mu-O2CMe])](2), 14, and [(BDI)Mg(mu-O2CPh)](2), 15, respectively. The molecular structures of complexes 4-8 and 12-15 are reported.