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.

Two magnesium complexes of the 6-aminofulvene-2-aldimine (AFA) system bearing cyclohexyl groups on the donor nitrogen atoms have been synthesised; in the first the ligand is coordinated via the two nitrogen donors while in the second it is found to ligate magnesium via the cyclopentadienyl and the imine donors.

Reaction of the Grignard reagent with polydentate nitrogen-donor ligands yields new species with rare magnesium coordination and possible catalytic activity. In the first of the title compounds, poly[[mu4-dihydrobis(pyrazol-1-yl)borato-kappa2N,N']potassium(I)], [K(C6H8BN4)]n, (I), polymeric chains form a two-dimensional network in the [100] plane. Each potassium ion is coordinated by four N atoms of pyrazolyl ligands, while weak (mu-BH)...K+ interactions additionally stabilize the structure. The K and B atoms both lie on a mirror plane. In three new structures obtained by disproportionation of the Grignard reagent, each Mg atom is bound to a kappa2N,N'-type ligand, forming the basal plane, and tetrahydrofuran molecules occupy the axial positions. Di-mu-chlorido-bis[dihydridobis(pyrazol-1-yl)borato]tris(tetrahydrofuran)dimagnesium(II), [Mg2(C6H8BN4)2Cl2(C4H8O)3], (II), adopts a dimeric structure with mu-Cl-Mg interactions. One of the Mg atoms has an octahedral coordination, while the other has a distorted square-pyramidal environment. However, in the bis-chelate compounds bis[dihydridobis(pyrazol-1-yl)borato-kappa2N,N'](tetrahydrofuran-kappaO)magnesium(II), [Mg(C6H8BN4)2(C4H8O)], (III), and bis[dihydridobis(pyrazol-1-yl)borato-kappa2N,N']bis(tetrahydrofuran-kappaO)magnesium(II), [Mg(C6H8BN4)2(C4H8O)2], (IV), the Mg atoms have square-pyramidal and octahedral environments, respectively. The Mg atom in (IV) lies on an inversion centre.

Key indicatorsSingle-crystal X-ray study T = 150 K Mean (C-C) = 0.003 Å R factor = 0.035 wR factor = 0.070 Data-to-parameter ratio = 19.0For details of how these key indicators were automatically derived from the article, see

The oligomerization of 2,6‐dimethyl­phenyl isocyanide by successive insertion of 2,6‐dimethyl­phenyl isocyanide with MeLi reagent gave the title compound, C38H42N4, which crystallizes in a centrosymmetric structure and possesses normal geometric parameters.