Organo-magnesium reagents: the crystal structures of [Mg(anthracene)(THF)3] and [Mg(triphenylmethyl)Br(OEt2)2]

[Mg(anthracene)(THF)3] (1), (THF = tetrahydrofuran), is monomeric in the solid state; the metal is bound to the C(9) and C(10) centres with r−(MgC) 2.30 A, and the [anthracene]2− ligand folded along the C(9)–C(10) vector with a mean angle of 28.6°. [Mg(CPh3)Br(OEt2)2] (4) is also monomeric; the metal centre is four-coordinate, bound only to the ipso-carbon of the carbanion, r(MgC) 2.225(1) A. Reaction of 1 or elemental magnesium with BrCPh3 in THF or addition of THF to 4, yields a red solid of the Grignard reagent containing some paramagnetic species.