Pyridinium Salts of Dehydrated Lanthanide Polychlorides.

The reaction of lanthanide (Ln) chloride hydrates ([) with pyridine (py) yielded a set of dehydrated pyridinium (py-H) Ln-polychloride salts. These species were crystallographically characterized as [[py-H-py][py-H][LnCl]] (; Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) or [[py-H][LnCl(py)]] ((; Ln = Tb, Dy, Ho, Er, Tm, Yb, Lu). The metal centers adopt an octahedral (-6) geometry, binding six Cl ligands.

Solid-State End-On to Side-On Isomerization of (N═N) in {[(RN)Nd]N} (R = SiMe) Connects In Situ Ln(NR)/K and Isolated [Ln(NR)] Dinitrogen Reduction.

Examination of the reduction chemistry of Nd(NR) (R = SiMe) under N has provided connections between the in situ Ln(III)-based Ln(NR)/K reductions of N that form side-on bound neutral (N=N) complexes, [(RN)(THF)Ln][μ-η:η-N], and the Ln(II)-based [Ln(NR)] reductions by Sc, Gd, and Tb that form end-on bound (N=N) complexes, {[(RN)Ln][μ-η:η-N]}, which are dianions. The reduction of Nd(NR) by KC under dinitrogen in EtO in the presence of 18-crown-6 (18-c-6) forms dark yellow solutions of [K(18-c-6)]{[(RN)Nd]N} at low temperatures that become green as they warm up to -35 °C in a glovebox freezer. Green crystals obtained from the solution turn yellow-brown when cooled below -100 °C, and the yellow-brown compound has an end-on Nd(μ-η:η-N) structure.

Nitrogen reduction by the Fe sites of synthetic [MoSFe] cubes.

Nitrogen (N) fixation by nature, which is a crucial process for the supply of bio-available forms of nitrogen, is performed by nitrogenase. This enzyme uses a unique transition-metal-sulfur-carbon cluster as its active-site co-factor ([(R-homocitrate)MoFeSC], FeMoco), and the sulfur-surrounded iron (Fe) atoms have been postulated to capture and reduce N (refs. ).

The Lanthanide Contraction Is a Variable.

Upon examination of the bond distances of the recently reported series of [Ln(SST)(THF)] [Ln = lanthanides, SST = tris(trimethylsilyl)siloxide (OSi(SiMe)), and THF = tetrahydrofuran] compounds, it was found that over the Ln-series (La through Lu), the Ln-O(THF) bond changed by 0.257 Å, whereas the Ln-O(SST) bond varied by 0.164 Å.

Synthesis, structure, and electrochemical properties of [LNi(R)(CF)] and [LNi(R)] complexes.

The new anionic nickelate complexes [(MeCN)Ni(CF)(CF)], [(MeCN)Ni(CF)(CF)], [(IMes)Ni(CF)(CF)], [(IMes)Ni(CF)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), and [(F-NHC)Ni(R)] (F-NHC = 1,3-bis(2,4-FPh), 2,4,6-FPh- or 3,4,5-FPh)imidazol-2-ylidene; (R = CF or CF) were synthesized and structurally characterized. The electrochemical properties of all new compounds were revealed by cyclic voltammetry studies and compared to the known CF analogue [(MeCN)Ni(CF)]. The IMes-coordinated complexes exhibited initial oxidation events that were well-separated from a second oxidation process in the cyclic voltammograms.

Synthesis and Characterization of Solvated Lanthanide Tris(trimethylsilyl)siloxides.

In an effort to develop precursors for the production of lanthanide silicate (LnSiO) materials, the reactions of [Ln(NR)] (R = SiMe) with three equivalents of tris(trimethylsilyl)silanol (H-OSi(SiMe)) or H-SST) in tetrahydrofuran (THF) were undertaken. The products were crystallographically characterized as [Ln(SST)(THF)] (where = , , , , , , , , , , , , , and ). In general, these compounds are similar to the previously reported [Gd(SST)(THF)] complex, where each metal center of the monomeric species is found to adopt a trigonal bipyramidal (TBP; τ = av 0.

Synthesis of a Nitrogenase P -Cluster Model with [Fe S (μ-S ) ] Core from the All-Ferric [Fe S (S ) ] Cubane Synthon.

Constructing synthetic models of the nitrogenase P -cluster has been a long-standing synthetic challenge. Here, we report an optimal nitrogenase P -cluster model [{(TbtS)(OEt )Fe S } (μ-STbt) (μ -S)] (2) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl] that is the closest synthetic mimic constructed to date. Of note is that two thiolate ligands and one hexacoordinated sulfide are connecting the two Fe S incomplete cubanes similar to the native P -cluster, which has never been achieved.

Organophosphorus-Modified Lanthanide Nitrates as Potential Actinide Oxide Aerosol Surrogates.

In search of suitable simulants for aerosol uranium waste products from Plutonium Uranium Redox Extraction (PUREX) process burns, a series of lanthanide nitrate hydrates ([Ln(NO)·HO]) were dissolved in the presence of tributylphosphate (O═P(O(CH)CH)) referred to as TBP) in kerosene or triphenylphosphate (O═P(O(CH) referred to as TPhP) in acetone. The crystal structure of the TPhP derivatives of the lanthanide nitrate series and uranium nitrate were solved as [Ln(κNO)(TPhP)] ( = , , , , , , , , , , , , , ) and [U(O)(κNO)(TPhP)] (), respectively. The lanthanide-TBP, , and were further characterized using FTIR spectroscopy, P NMR spectroscopy, thermogravimetric analysis, and X-ray fluorescence spectroscopy.

A dinuclear MoH complex supported by bulky CHBu ligands.

Hydride-bridged transition metal complexes have been found to serve as suitable precursors for the activation of small molecules without the use of reducing agents. In this study, we synthesized a dinuclear Mo2H8 complex supported by bulky C5H2tBu3 (Cp‡) ligands, Cp‡2Mo2H8 (1), from the reaction of Cp‡MoCl4 with KC8 under H2. The hydrides of complex 1 can be replaced with benzene at 60 °C to afford a μ-benzene complex Cp‡2Mo2H2(μ-C6H6) (2).

[(MeCN)Ni(CF)] and [Ni(CF)]: Foundations toward the Development of Trifluoromethylations at Unsupported Nickel.

Nickel anions [(MeCN)Ni(CF)] and [Ni(CF)] were prepared by the formal addition of 3 and 4 equiv, respectively, of AgCF to [(dme)NiBr] in the presence of the [PPh] counterion. Detailed insights into the electronic properties of these new compounds were obtained through the use of density functional theory (DFT) calculations, spectroscopy-oriented configuration interaction (SORCI) calculations, X-ray absorption spectroscopy, and cyclic voltammetry. The data collectively show that trifluoromethyl complexes of nickel, even in the most common oxidation state of nickel(II), are highly covalent systems whereby a hole is distributed on the trifluoromethyl ligands, surprisingly rendering the metal to a physically more reduced state.

Synthesis of [MoS] Clusters from Half-Sandwich Molybdenum(V) Chlorides and Their Application as Platforms for [MoSFe] Cubes.

Triangular [MoS] clusters are known to serve as platforms to accommodate a metal atom M, furnishing cubic [MoSM] clusters. In this study, three [MoS] clusters supported by η-cyclopentadienyl (Cp) ligands, [CpMoS] (Cp = CMeSiMe, CMeSiEt, and CMeH), were synthesized via half-sandwich molybdenum chlorides CpMoCl. In the cyclic voltammogram of the [MoS] cluster having CMeH ligands, a weak feature appeared in addition to the [CpMoS] redox process, indicating the interaction between [CpMoS] and the [NBu] cation of the electrolyte, while such a feature was less significant for the CMeSiR variants.

Synthesis, Characterization, and Nanomaterials Generated from 6,6'-(((2-Hydroxyethyl)azanediyl)bis(methylene))bis(2,4-di- tert-butylphenol) Modified Group 4 Metal Alkoxides.

The impact on the morphology nanoceramic materials generated from group 4 metal alkoxides ([M(OR)]) and the same precursors modified by 6,6'-(((2-hydroxyethyl)azanediyl)bis(methylene))bis(2,4-di- tert-butylphenol) (referred to as H-AM-DBP (1)) was explored. The products isolated from the 1:1 stoichiometric reaction of a series of [M(OR)] where M = Ti, Zr, or Hf; OR = OCH(CH)(OPr ); OC(CH)(OBu ); OCHC(CH)(ONep) with H-AM-DBP proved, by single crystal X-ray diffraction, to be [(ONep)Ti( k( O,O',O'',N)-AM-DBP)] (2), [(OR)M(μ( O)- k( O',O'',N)-AM-DBP)] [M = Zr: OR = OPr , 3·tol; OBu , 4·tol; ONep, 5·tol; M = Hf: OR = OBu , 6·tol; ONep, 7·tol]. The product from each system led to a tetradentate AM-DBP ligand and retention of a parent alkoxide ligand.

N activation on a molybdenum-titanium-sulfur cluster.

The FeMo-cofactor of nitrogenase, a metal-sulfur cluster that contains eight transition metals, promotes the conversion of dinitrogen into ammonia when stored in the protein. Although various metal-sulfur clusters have been synthesized over the past decades, their use in the activation of N has remained challenging, and even the FeMo-cofactor extracted from nitrogenase is not able to reduce N. Herein, we report the activation of N by a metal-sulfur cluster that contains molybdenum and titanium.

Synthesis and Characterization of Tris(trimethylsilyl)siloxide Derivatives of Early Transition Metal Alkoxides That Thermally Convert to Varied Ceramic-Silica Architecture Materials.

In an effort to generate single-source precursors for the production of metal-siloxide (MSiO ) materials, the tris(trimethylsilyl)silanol (H-SST or H-OSi(SiMe) (1) ligand was reacted with a series of group 4 and 5 metal alkoxides. The group 4 products were crystallographically characterized as [Ti(SST)(OR)] (OR = OPr (2), OBu (3), ONep (4)); [Ti(SST)(OBu )] (5); [Zr(SST)(OBu )(py)] (6); [Zr(SST)(OR)] (OR = OBu (7), ONep, (8)); [Hf(SST)(OBu )] (9); and [Hf(SST)(ONep)(py) ] ( n = 1 (10), n = 2 (10a)) where OPr = OCH(CH), OBu = OC(CH), OBu = O(CH)CH, ONep = OCHC(CH), py = pyridine. The crystal structures revealed varied SST substitutions for: monomeric Ti species that adopted a tetrahedral ( T-4) geometry; monomeric Zr compounds with coordination that varied from T-4 to trigonal bipyramidal ( TBPY-5); and monomeric Hf complexes isolated in a TBPY-5 geometry.

Synthesis and lanthanide coordination chemistry of phosphine oxide decorated dibenzothiophene and dibenzothiophene sulfone platforms.

Syntheses for new ligands based upon dibenzothiophene and dibenzothiophene sulfone platforms, decorated with phosphine oxide and methylphosphine oxide donor groups, are described. Coordination chemistry of 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene (8), 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene-5,5-dioxide (9) and 4,6-bis(diphenylphosphinoyl)dibenzothiophene-5,5-dioxide (10) with lanthanide nitrates, Ln(NO3)3·(H2O)n is outlined, and crystal structure determinations reveal a range of chelation interactions on Ln(III) ions. The nitric acid dependence of the solvent extraction performance of 9 and 10 in 1,2-dichloroethane for Eu(III) and Am(III) is described and compared against the extraction behavior of related dibenzofuran ligands (2, 3; R = Ph) and n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (4) measured under identical conditions.

A nitrogenase cluster model [Fe8S6O] with an oxygen unsymmetrically bridging two proto-Fe4S3 cubes: relevancy to the substrate binding mode of the FeMo cofactor.

An oxygen-encapsulated iron sulfido cluster, [(DmpS)Fe(4)S(3)O][(DmpS)Fe(4)S(3)](μ-SDmp)(2)(μ-OCPh(3)) (2; Dmp = 2,6-(mesityl)(2)C(6)H(3)), has been synthesized by the reaction of the preformed dinuclear iron thiolate/alkoxide [(Ph(3)CO)Fe](2)(μ-SDmp)(2) (1) with (1/8)S(8) and (1/4)H(2)O in toluene. In the [Fe(8)S(6)O] core, the oxygen atom bridges unsymmetrically two incomplete Fe(4)S(3) cubes, and two coordinatively unsaturated iron atoms are weakly bound to mesityl rings. Relevance of the cluster structure of 2 to the nitrogenase FeMo cofactor and its substrate binding mode is discussed.

Five- and Six-Coordinate 2-Methyl-2-propanethiolato Complexes of Zirconium(IV): Synthesis and Structures of [Li(DME)(3)][Zr(SCMe(3))(5)] and [(THF)Li](2)Zr(SCMe(3))(6).

Five-coordinate and six-coordinate 2-methyl-2-propanethiolato complexes of zirconium, [Li(DME)(3)][Zr(SCMe(3))(5)] (1) and [(THF)Li](2)Zr(SCMe(3))(6) (2), were obtained from the ZrCl(4)/LiSCMe(3) reaction system. The control of the Zr coordination number, by the ether ligands, THF or DME, bound to Li, is demonstrated by the conversion of 2 into 1 upon dissolution in DME. 1 and 2 were crystallographically characterized.