Andrea Sella

(PhTe)3−: The Anionic Tellurium Analogue of I3−

The missing link between solid-state tellurium chemistry and polyhalide ions is provided by the synthesis of the almost linear (PhTe)(3)(-) ion, whose structure is shown. Tritelluride units are a recurring motif in the solid state and are related to the structures of polyhalides.

Reactivity of pyrazolylborate complexes of samarium with transition metal carbonyls

Abstract The reaction of [Sm(TpMe,Me)2] with [M(η-C5H4R)(CO)3]2 (M = Cr, R = H; M = Mo, R = Me, tBu; M = W, R = H) gives good yields of [Sm(TpMe,Me)2(μ-OC) M(η-C5H4R)(CO)2]. The crystal structure of the complex for which M = Mo and R = Me has been determined (triclinic, P1¯, a = 10.4106(6), b = 14.1022(8), c = 18.6974(11)A, α = 71.579(2), β = 88.751(2), γ = 85.095(2)° and V = 2594.8(3)A3) confirms the seven coordinate samarium centre with the expected bridging isocarbonyl. In contrast, the reaction of [Sm(TpMe,Me)2] with [Co2(CO)8] gives the salt [Sm(TpMe,Me)2][Co(CO)4] together with [Co4(CO)12].

Synthesis and structure of the first η6-pyrazine complex [V(η6-Me4pyrazine)2] and related studies

Abstract The synthesis of vanadium and molybdenum complexes derived from nitrogen-containing heterocyclic aromatic ligands are described. The first η-pyrazine sandwich complex, [V(η 6 -Me 4 pyrazine) 2 ], has been prepared by metal vapour synthesis and crystallographically characterized. The synthesis of [Mo(η 6 -2,6-lutidine) 2 ] has been substantially improved, and provides a convenient starting material for the preparation of the new half-sandwich compounds [Mo(η 6 -2,6-lutidine)(PMe 3 ) 3 ] and [Mo(η 6 -2,6-lutidine)(η 3 -allyl)Cl] 2 .

(PhTe)3−: das anionische Telluranalogon von I3−

Das „missing link” zwischen der Feststoff-Tellurchemie und den Polyhalogenid-Ionen wird durch die Synthese des nahezu linearen (PhTe)3−-Ions hergestellt, dessen Struktur gezeigt ist. Tritellurid-Einheiten sind ein haufig vorkommendes Motiv in der Feststoff-Tellurchemie und strukturell eng mit den Polyhalogeniden verwandt.

A steric preference for linear versus bent imido ligation? Synthesis and x-ray crystal structure of [Mo(NAr)2(edtc)2] (Ar = 2,6-iPr2C6H3; edtc = S2CNEt2) containing two linear imido moieties

Abstract Reaction of two equivalents of ArNCO (Ar = 2,6-iPr2C6H3) with [MoO2(edtc)2] affords the bisimido complex [Mo(NAr)2(edtc)2] shown by crystallography to contain two linear imido ligands; this is in contrast to the parent complex [Mo(NPh)2(edtc)2] previously shown to contain both linear and bent imido groups.

Simple adducts of samarium and ytterbium diiodide: synthesis and molecular structures of LnI2(3,5-lutidine)4 (Ln = Sm, Yb) and YbI2(4-t-butylpyridine)4

Abstract Reaction of LnI2 (Ln = Sm, Yb) with substituted pyridines in THF gives good yields of the highly coloured complexes [LnI2(py)4]. The structures of complexes [LnI2(3,5-lutidine)4] (Sm, Yb) and [YbI2(4-t-butylpyridine)4] have been determined by X-ray crystallography and show simple octahedral coordination about the metal centre with trans-iodide ligands.

Metastable phase transitions and structural transformations in solid-state materials at high pressure

We use a combination of diamond anvil cell techniques and large volume (multi-anvil press, piston cylinder) devices to study the synthesis, structure and properties of new materials under high pressure conditions. The work often involves the study of structural and phase transformations occurring in the metastable regime, as we explore the phase space determined as a function of the pressure, temperature and chemical composition. The experimental studies are combined with first principles calculations and molecular dynamics simulations, as we determine the structures and properties of new phases and the nature of the transformations between them. Problems currently under investigation include structural studies of transition metal and main group nitrides, oxides and oxynitrides at high pressure, exploration of new solid-state compounds that are formed within the C-N-O system, polyamorphic low- to high-density transitions among amorphous semiconductors such as a-Si, and transformations into metastable forms of the element that occur when its “expanded” clathrate polymorph is compressed.

Single Crystal, Luminescent Carbon Nitride Nanosheets Formed by Spontaneous Dissolution

A primary method for the production of 2D nanosheets is liquid-phase delamination from their 3D layered bulk analogues. Most strategies currently achieve this objective by significant mechanical energy input or chemical modification but these processes are detrimental to the structure and properties of the resulting 2D nanomaterials. Bulk poly(triazine imide) (PTI)-based carbon nitrides are layered materials with a high degree of crystalline order. Here, we demonstrate that these semiconductors are spontaneously soluble in select polar aprotic solvents, that is, without any chemical or physical intervention. In contrast to more aggressive exfoliation strategies, this thermodynamically driven dissolution process perfectly maintains the crystallographic form of the starting material, yielding solutions of defect-free, hexagonal 2D nanosheets with a well-defined size distribution. This pristine nanosheet structure results in narrow, excitation-wavelength-independent photoluminescence emission spectra. Furthermore, by controlling the aggregation state of the nanosheets, we demonstrate that the emission wavelengths can be tuned from narrow UV to broad-band white. This has potential applicability to a range of optoelectronic devices.

Some chemistry of half-sandwich η-arene tungsten compounds

The compounds [W(η-C6H5Me)(PMe3)3] and [W(η-C6H5Me){SiMe(CH2PMe2)3}] have been prepared from [W(η-C6H5Me)2] and tertiary phosphines. They are protonated by NH4BF4 to give [W(η-C6H5Me)(PMe3)3H]BF4 and [W(η-C6H5Me){SiMe(CH2PMe2)3}H]BF4, respectively. Reaction of [W(η-C6H5Me)(PMe3)3] with HCl gas gives the diprotonated cation [W(η-C6H5Me)(PMe3)3H2]2+. Treatment of [W(η-C6H5Me)(η-C3H5)(dmpe)]PF6[dmpe = 1,2-bis(dimethylphosphino)ethane] with LiAlH4 gives the η-methylcyclohexadienyl complex [W(η5-C6H6Me)(η-C3H5)(dmpe)], as a mixture of inseparable isomers. These have been characterised by multinuclear two-dimensional NMR spectroscopy. The fluorohydride [W(η-C6H5Me)(dmpe)H(F)] has also been prepared. The X-ray crystal structures of [W(η-C6H5Me)(PMe3)3H2][PF6]2 and [W(η-C6H5Me)(dmpe)H(F)] have been determined.

Electrochemical properties of graphitic carbon nitrides

Lithium-ion batteries (LIBs) are the current devices of choice for portable energy storage applications; however, improvements in energy and power densities are required to sustain future more demanding tasks, such as those associated with automotive transport. Commercially, LIB anodes are typically made from graphitic carbon-based systems that present bottlenecks associated with surface passivation and slow intercalation kinetics. We have investigated layered/graphitic carbon nitrides (gCNMs) as alternative anode materials; their unique structure and chemistry enable new intercalation processes not available for pure-C graphite. Our gCNMs are prepared from C, N-containing precursors treated at different temperatures. Cyclic voltammetry showed clear oxidation/reduction cycles in the 0.5–1.5 V range indicating that Li + intercalation took place resulting in electric conduction properties of the previously semiconducting material. Higher reaction temperatures lead to buckling of the graphitic layers and consequent loss of planarity, with a negative effect on their electrochemical performance.