The First Structural Characterisation of a Group 2 Metal Alkylperoxide Complex: Comments on the Cleavage of Dioxygen by Magnesium Alkyl Complexes

Abstract

A new high-yield synthesis of [(PhCH(2))(2)Mg(thf)(2)] and [[(PhCH(2))CH(3)Mg(thf)](2)] via benzylpotassium has allowed a simple entry into benzylmagnesium coordination chemistry. The syntheses and X-ray crystal structures of both [(eta(2)-Me(2)NCH(2)CH(2)NMe(2))Mg(CH(2)Ph)(2)] and [eta(2)-HC[C(CH(3))NAr'](2)Mg(CH(2)Ph)(thf)] (Ar'=2,6-diisopropylphenyl) are reported. The latter beta-diketiminate complex reacts with dioxygen to provide a 1:2 mixture of dimeric benzylperoxo and benzyloxo complexes. The benzylperoxo complex [[eta(2)-HC[C(CH(3))NAr'](2)Mg(mu-eta(2):eta(1)-OOCH(2)Ph)](2)] is the first example of a structurally characterised Group 2 metal-alkylperoxo complex and contains the benzylperoxo ligands in an unusual mu-eta(2):eta(1)-coordination mode, linking the two five-coordinate magnesium centres. The O[bond]O separation in the benzylperoxo ligands is 1.44(2) A. Reaction of the benzylperoxo/benzyloxo complex mixture with further [eta(2)-HC[C(CH(3))NAr'](2)Mg(CH(2)Ph)(thf)] results in complete conversion of the benzylperoxo species into the benzyloxo complex. This reaction, therefore, establishes the cleavage of dioxygen by this system as a two-step process that involves initial oxygen insertion into the Mg[bond]CH(2)Ph bond followed by O[bond]O/Mg[bond]C sigma-bond metathesis of the resulting benzylperoxo ligand with a second Mg[bond]CH(2)Ph bond. The formation of a 1:2 mixture of the benzylperoxo and benzyloxo species indicates that the rate of the insertion is faster than that of the metathesis, and this is shown to be consistent with a radical mechanism for the insertion process.

Ligand Dependence of Binding to Three-Coordinate Fe(II) Complexes

“…Here, this difficulty is avoided by using the potassium salt of the bulky β-diketiminate ligand (KL tBu,iPr2 ). This potassium salt was synthesized by treating the diimine L tBu,iPr2 H with benzylpotassium22 in diethyl ether 23. Reaction of KL tBu,iPr2 with FeCl 2 (THF) 1.5 in toluene reproducibly gave a clean product from which KCl could be removed by filtration.…”

Reactivity of Hydride Bridges in High-Spin [3M–3(μ-H)] Clusters (M = FeII, CoII)

“…Anal. found (calcd) for C 45 H 66 N 6 Fe 3 : C, 62.83 (62.95); H, 7.78 (7.75); N, 9.73 (9.79); Fe, 19.39 (19.51).…”

Tetraanionic Biphenyl Lanthanide Complexes as Single-Molecule Magnets

“…20 mL) layered with n-pentane (ca. 20 9 In a 20 mL scintillation vial, (NN TBS )DyI(THF)2 (0.4000 g, 0.457 mmol) and biphenyl (0.0352 g, 0.228 mmol) were dissolved in ca. 10 mL of THF.…”