Anionic Magnesium and Calcium Hydrides : Transforming CO into Unsaturated Disilyl Ethers

OA-artikkeli, mutta ladattaessa tulee hieman erinäköinen versio (esim. ei lisenssiä). Tallennettu kuitenkin OA-artikkelina.The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X-ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be “terminal”, but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis-ethenediolate complexes. These cis-ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C1 source CO.Peer reviewe

Inhibition of Alkali Metal Reduction of 1-Adamantanol by London Dispersion Effects

A series of alkali metal 1-adamantoxide (OAd1) complexes of formula [M(OAd1)(HOAd1)2], where M=Li, Na or K, were synthesised by reduction of 1-adamantanol with excess of the alkali metal. The syntheses indicated that only one out of every three HOAd1 molecules was reduced. An X-ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd1 donors as well as the reduced alkoxide (OAd1), with the Ad1 fragments clustered together on the same side of the NaO3 plane, contrary to steric considerations. This is the first example of an alkali metal reduction of an alcohol that is inhibited from completion due to the formation of the [M(OAd1)(HOAd1)2] complexes, stabilized by London dispersion effects. NMR spectroscopic studies revealed similar structures for the lithium and potassium derivatives. Computational analyses indicate that decisive London dispersion effects in the molecular structure are a consequence of the many C−H⋅⋅⋅H−C interactions between the OAd1 groups.Peer reviewe

Crystalline Germanium(I) and Tin(I) Centered Radical Anions

An isostructural series of heavy Group 14 E(I) radical anions (Ge, Sn, Pb), stabilized by a bulky xanthene-based diamido ligand are reported. The radical anions were synthesised by the one-electron reduction of their corresponding E(II) precursor complexes with sodium naphthalenide in THF, yielding the radical anions as charge-separated sodium salts. The series of main group radicals have been comprehensively characterized by EPR spectroscopy, X-ray crystallography and DFT analysis, which reveal that in all cases, the spin density of the unpaired electron almost exclusively resides in a p-orbital of pi symmetry located on the Group 14 center.Peer reviewe

Terpene Dispersion Energy Donor Ligands in Borane Complexes

Structural characterization of the complex [B(beta-pinane)(3)] (1) reveals non-covalent H center dot center dot center dot H contacts that are consistent with the generation of London dispersion energies involving the beta-pinane ligand frameworks. The homolytic fragmentations of 1, and camphane and sabinane analogues ([B(camphane)(3)] (2) and [B(sabinane)(3)] (3)) were studied computationally. Isodesmic exchange results showed that London dispersion interactions are highly dependent on the terpene's stereochemistry, with the beta-pinane framework providing the greatest dispersion free energy (Delta G = -7.9 kcal mol(-1)) with Grimme's dispersion correction (D3BJ) employed. PMe3 was used to coordinate to [B(beta-pinane)(3)], giving the complex [Me3P-B(beta-pinane)(3)] (4), which displayed a dynamic coordination equilibrium in solution. The association process was found to be slightly endergonic at 302 K (Delta G = +0.29 kcal mol(-1)).Peer reviewe