A Well-defined Magnesium Complex of C706.

Controlling and understanding charge state and metal coordination in carbon nanomaterials is crucial to harnessing their unique properties. Here we describe the synthesis of the well-defined fulleride complex [{(Mesnacnac)Mg}6C70], 2, (Mesnacnac) = HC(MeCNMes)2, Mes = 2,4,6-Me3C6H2, from the reaction of the ß-diketiminate magnesium(I) complex [{(Mesnacnac)Mg}2] with C70 in aromatic solvents. The molecular structure of complex 2 was determined, providing the first high-quality structural study of a complex with the C706- ion. In combination with solution state NMR spectroscopic and DFT computational studies, the changes in geometry and charge distribution in the various atom and bond types of the fulleride unit were investigated. Additionally, the influence of the (Mesnacnac)Mg+ cations on the global and local fulleride coordination environment was examined.

Synthesis of a Hexameric Magnesium 4-pyridyl Complex with Cyclohexane-like Ring Structure via Reductive C-N Activation.

The reaction of [{(Arnacnac)Mg}2] (Arnacnac = HC{MeC(NAr)}2, Ar = 2,6-diisopropylphenyl, Dip, or 2,6-diethylphenyl, Dep) with 4-dimethylaminopyridine (DMAP) at elevated temperatures afforded the hexameric magnesium 4-pyridyl complex [{(Arnacnac)Mg(4-C5H4N)}6] via reductive cleavage of the DMAP C-N bond. The title compound contains a large s-block organometallic cyclohexane-like ring structure comprising tetrahedral (Arnacnac)Mg nodes and linked by linear 4-pyridyl bridging ligands, and the structure is compared with other ring systems. [(Dipnacnac)Mg(DMAP)(NMe2)] was structurally characterised as a by-product.

Mechanistic insights of anionic ligand exchange and fullerene reduction with magnesium(i) compounds.

Ligand exchange reactions between combinations of the complexes [{(Arnacnac)Mg}2], where Ar = 2,6-iPr2C6H3 (Dip), 2,6-Et2C6H3 (Dep), 2,4,6-Me4C6H2 (Mes), and 2,6-Me2C6H3 (Xyl), [({Ph2P(NDip)2}Mg)2], [(Arnacnac)Li], where Ar = Mes or Xyl, and [{Ph2P(NDip)2}Li] were studied in deuterated aromatic and aliphatic solvents, and tetrahydrofuran. The reactions afforded product mixtures with asymmetrically substituted dimagnesium(i) complexes [(Arnacnac)MgMg(Ar'nacnac)], where Ar, Ar' = Dip, Dep, Mes, Xyl and [{Ph2P(NDip)2}MgMg(Arnacnac)], where Ar = Mes or Xyl, and suggest that the exchange of anionic ligands on the Mg22+ ion proceeds via an associative mechanism and is strongly dependent on ligand sterics and ligand shape, and can be very rapid. The activation reaction of fullerene C60 by dimagnesium(i) complexes [{(Arnacnac)Mg}2] and [({Ph2P(NDip)2}Mg)2] to fulleride complexes is similarly dependent on ligand sterics and ligand shape, but likely does not involve direct coordination of the fullerene to the Mg centre in dimagnesium(i) compounds prior to its reduction. The new C606- fulleride complex [({Ph2P(NDip)2}Mg)6C60] was prepared, and spectroscopically and structurally characterised.

Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium.

The reaction of the magnesium(i) complexes [{(Arnacnac)Mg}2], (Arnacnac = HC(MeCNAr)2, Ar = Dip (2,6-iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C60 afforded a series of hydrocarbon-soluble fulleride complexes [{(Arnacnac)Mg} n C60], predominantly with n = 6, 4 and 2. 13C{1H} NMR spectroscopic studies show both similarities (n = 6) and differences (n = 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. The molecular structures of [{(Arnacnac)Mg} n C60] with n = 6, 4 and 2 can be described as inverse coordination complexes of n [(Arnacnac)Mg]+ ions with C60 n- anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C60 6- ion. Experimental studies show the flexible ionic nature of the {(Arnacnac)Mg}+···C60 6- coordination bonds. DFT calculations on the model complex [{(Menacnac)Mg}6C60] (Menacnac = HC(MeCNMe)2) support the formulation as an ionic complex with a central C60 6- anion and comparable frontier orbitals to C60 6- with a small HOMO-LUMO gap. The reduction of C60 to its hexaanion gives an indication about the reducing strength of dimagnesium(i) complexes.

PNacPNacE: (E = Ga, In, Tl) - monomeric group 13 metal(i) heterocycles stabilized by a sterically demanding bis(iminophosphoranyl)methanide.

The salt metathesis reaction of the sterically demanding bis(iminophosphoranyl)methanide alkali metal complexes LM (L- = HC(Ph2P[double bond, length as m-dash]NDip)2-, Dip = 2,6-iPr2C6H3; M = Li, Na, K) with "GaI", InBr or TlBr afforded the monomeric group 13 metal(i) complexes LE:, E = Ga (1), In (2) and Tl (3) in moderate yields, and small quantities of LGaI24 in the case of Ga, respectively. The molecular structures of LE: 1-3 from X-ray single crystal diffraction show them to contain puckered six-membered rings with N,N'-chelating methanide ligands and two-coordinated metal(i) centres. Reduction reactions of LAlI25, prepared by iodination of LAlMe2, were not successful and no aluminium(i) congener could be prepared so far. DFT studies on LE:, E = Al-Tl, were carried out and support the formulation as an anionic, N,N'-chelating methanide ligand coordinating to group 13 metal(i) cations. The HOMOs of the molecules for E = Al-In show a dominant contribution from a metal-based lone pair that is high in s-character.