The Solubility of Bis(cyclopentadienyl)samarium(II) and Implications for the Reaction of Samarium Metal with Bis(cyclopentadienyl)mercury(II)

Bis(cyclopentadienyl)samarium(II) has been shown to be insoluble in thf : ether mixtures, hence it cannot be isolated as a soluble product from the reaction of samarium with HgCp₂ in thf : ether.     

Solvothermal vs. bench-top reactions: control over the formation of discrete complexes and coordination polymers

The formation of discrete complexes [M(mcoe)2S2] (M = Cu, Ni; S = MeOH, H2O) vs. a nitroso-bridged ferromagnetically-coupled Cu(II) coordination polymer [Cu(mcoe)2] is influenced by the use of solvothermal reaction conditions.     

Molecular and Crystal Structures of Pentafluorophenyl‐platinum(II) Complexes with Bis(diphenylphosphino)methane,Bis(diphenylarsino)methane and 1,2‐Bis(diphenylarsino)ethane

The X‐ray crystal structures of [PtCl₂(dppm)], [Pt(C₆F₅)₂L] (L = dppm (bis(diphenylphosphino)methane), dpam (bis(diphenylarsino)methane), dpae (bis(diphenylarsino)ethane)) and [PtCl(C₆F₅)(dpae)] show the complexes to be monomeric with chelating dipnictido ligands, and not alternatives with bridging ligands. In [Pt(C₆F₅)₂(dpam)₂], there are two unidentate diarsine ligands in a cis‐arrangement.     

Chalcogen Bonds in Selenocysteine Seleninic Acid,a Functional GPx Constituent,and in Other Seleninic or Sulfinic Acid Derivatives

The controlled oxidation reaction of L-selenocystine under neutral pH conditions affords selenocysteine seleninic acid (3-selenino-L-alanine) which is characterized also by means of single-crystal X-ray diffraction. This technique shows that selenium forms three chalcogen bonds (ChBs), one of them being outstandingly short. A survey of seleninic acid derivatives in the Cambridge Structural Database (CSD) confirms that the C−Se(=O)O− functionality tends to act as a ChB donor robust enough to systematically influence the interactional landscape in the solid. Quantum Theory of Atom in Molecules (QTAIM) analysis proves the attractive nature of the short contacts observed in crystals containing the seleninic functionality and calculation of surface molecular electrostatic potential (MEP) reveals that remarkably positive σ-holes can frequently be found opposite to the covalent bonds at selenium. Both CSD searches and QTAIM and MEP approaches show that also the sulfinic acid moiety can function as a ChB donor, albeit less frequently than the seleninic acid one. These findings may contribute to a better understanding, at the atomic level, of the mechanism of action of the enzymes that control oxidative stress and ROS deactivation and that contain selenocysteine seleninic acid and cysteine sulfinic acid in the active site.     

Engineering of efficient panchromatic sensitizers for nanocrystalline TiO(2)-based solar cells.

A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation [(C(2)H(5))(3)NH][Ru(H(3)tcterpy)(NCS)(3)] 1, [(C(4)H(9))(4)N](2)[Ru(H(2)tcterpy)(NCS)(3)] 2, [(C(4)H(9))(4)N](3)[Ru(Htcterpy)(NCS)(3)] 3, and [(C(4)H(9))(4)N](4)[Ru(tcterpy)(NCS)(3)] 4 (tcterpy = 4,4',4' '-tricarboxy-2,2':6',2' '-terpyridine) have been synthesized and fully characterized by UV-vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a Ru(II)N6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better pi-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO(2) films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, K(ads), of (1.0 +/- 0.3) x 10(5) M(-1). The amount of dye adsorbed at monolayer saturation was (n(alpha) = 6.9 +/- 0.3) x 10(-)(8) mol/mg of TiO(2), which is around 30% less than that of the cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO(2) films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm(2), and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.     

Diverse heteroleptic ytterbium(III) thiocyanate complexes by oxidation from bis(thiocyanato)ytterbium(II)

The new ytterbium(II) thiocyanate complex [Yb(NCS)2(thf)2] (1), synthesised by redox transmetallation between [Hg(SCN)2] and ytterbium metal in THF at room temperature, gave monomeric, eight coordinate [Yb-(NCS)2(dme)3] (2, dme = 1,2-dimethoxyethane) on crystallisation from DME, and is a powerful, synthetically useful reductant. Thus, oxidation of 1 with Hg(SCN)2, Hg(C6F5)2/HOdpp (HOdpp = 2,6-diphenylphenol), TlCp (Cp = C5H5 or CH3C5H4), Tl(Ph2pz) (Ph2pz = 3,5-diphenylpyrazolate) and CCl3CCl3 in THF yielded the ytterbium(II) complexes [Yb(NCS)3(thf)4] (3), [Yb-(NCS)2(Odpp)(thf)3](4), [Yb(NCS)2Cp-(thf)3] (Cp = C5H5 (5), CH3C5H4 (6)), [Yb(NCS)2(Ph2pz)(thf)4] (7) and [Yb(NCS)2Cl(thf)4] (8). In the solid state, complexes 4, 6 and 7 were shown by X-ray crystallography to be six, eight and eight coordinate monomers, respectively. Exclusively terminal, N-bound transoid thiocyanate bonding is observed with eta1-Odpp (4), eta5/-C5H4Me (6) and eta2-Ph2Pz (7) ligands attached approximately perpendicular to the N...N vector. The chloride complex 8 is not a molecular species, but consists of discrete, seven coordinate [YbCl2(thf)5] cations and [Yb(NCS)4(thf)3] anions. By contrast, oxidation of 1 with TlO2CPh gave a mixture of [[Yb(NCS)-(O2CPh)2(thf)2]2] (9) and 3 through rearrangement of an initially formed [Yb(NCS)2(O2CPh)] species. The X-ray structure of 9 indicates a dimeric complex with a (Yb(mu-O2CPh)4Yb] core that contains both bridging bidentate and bridging tridentate benzoate groups, and with a terminal N-bound thiocyanate and two THF ligands on each ytterbium. Reduction of Ph2CO with 1 in THF yielded the dinuclear complex [[Yb(NCS)2(thf)3]2(mu-OC(Ph)2C(Ph)2O)] (10), in which two octahedral Yb centres are bridged by a 1,1,2,2-tetraphenylethane-1,2-diolate ligand, derived from reductive coupling of the benzophenone reagent.     

A Novel Alkene(alkyl)(aqua)(aryl)platinum(II) Complex – [Pt{CH(CH2C6F5)CH2CH2CH=CH2}(C6F5)(OH2)]

From the reaction of PtCl₂(hex) (hex = hexa‐1,5‐diene) with LiC₆F₅ in diethyl ether, the complex [Pt{CH(CH₂C₆F₅)CH₂CH₂CH=CH₂}(C₆F₅)(OH₂)] ( 1 ) was isolated. The crystal structure (monoclinic, C2/c (no. 15), Z = 8, a = 15.241(3), b = 16.579(2), c = 16.225(2) Å, β = 111.12(2)°) shows a complex with square planar coordination around platinum with a template formed 1‐pentafluorophenylhex‐5‐en‐2‐yl ligand, and C₆F₅ and aqua ligands trans to the double bond and alkyl carbon, respectively.     

Refutation of the synthesis of tetrakis(cyclopentadienyl)cerium(IV)

Reaction of sodium cyclopentadienide with dipyridinium hexachlorocerate(IV) in tetrahydrofuran yields tris(cyclopentadienyl)cerium(III) and not tetrakis(cyclopentadienyl)cerium(IV).