Metal-mediated rearrangement of 1,2-diphenylhydrazine to ortho-semidine upon reaction with dichlorotris(triphenylphosphine)ruthenium(II).

Reaction between RuCl2(PPh3)3 and 1,2-diphenylhydrazine resulted in rearrangement and coordination of ortho-semidine. The product, RuCl2(PPh3)2(κ2-NH2-1,2-C6H4-NHPh), was characterized spectroscopically and the molecular structure was conclusively determined using X-ray crystallography. Computational chemistry was employed to probe the energetics surrounding the rearrangement reaction and product.

Fullerene nanostructures: how the oblong shape of C70 forms a cocrystal with an enormous asymmetric unit and related cocrystals.

Cocrystallization of NiII(OEP) (where OEP is the dianion of octaethylporphyrin) with C70 in p-xylene produces black plates of 12NiII(OEP)·12C70·18p-xylene (1). Single crystal X-ray diffraction at 90 K reveals that the crystal contains 42 individual, well-ordered molecules in the asymmetric unit with distinctive interactions between each NiII(OEP)/C70 pair and each pair of neighboring C70 molecules. Warming the crystal to 186 K produces a phase change so that only four NiII(OEP)/C70 sites and six p-xylene molecules are present. Under the same conditions CuII(OEP) cocrystallizes with C70 to form CuII(OEP)·C70·1.5p-xylene (2) with a much simpler structure consisting of one molecule of the porphyrin and the fullerene along with 1.5 molecules of p-xylene in the asymmetric unit. Crystallization of C70 from toluene in the presence of NiII(etioporphyrin-I) produces the black solvate 6C70·6toluene (3). It seems that C70 has a tendency to crystallize so that several orientations of the oblong molecule are present in the solid.

Quantification of hexagonal boron nitride impurities in boron nitride nanotubes via FTIR spectroscopy.

Preparation of high-quality boron nitride nanotubes (BNNTs) from commercially available stock is critical for eventual industry adoption and to perform comprehensive experimental studies of BNNTs. Separation of hexagonal boron nitride (h-BN) and BNNTs is a significant challenge, and equally so, quantification of h-BN content in mixed samples is a major challenge due to their nearly identical properties. This work introduces a simple method of quantifying h-BN content in BNNTs based on FTIR analysis. Quantification is achieved by "spiking" a BNNT sample with pure nanoscale h-BN as an internal standard. To demonstrate the efficacy of the quantification technique two BNNT enrichment methods, surfactant wrapping and centrifugation, and a novel sonication-assisted isovolumetric filtration are introduced. FTIR spectra of enriched samples show clear trends throughout the processes. We propose and demonstrate that FTIR peak ratios of the transverse and buckling modes of mixed h-BN/BNNT samples can be used to calibrate and quantify h-BN content in any BNNT sample. Hopefully, this method enables as-received BNNTs to be quantifiably enriched from low purity commercial feedstocks, enabling future development and study of BNNTs and related technology.

Single-Crystal X-ray Diffraction Studies of Solvated Crystals of C60 Reveal the Intermolecular Interactions between the Component Molecules.

The solid-state structures of seven solvates of C60 (C60·4tetrachloroethylene, C60·2tetrachloroethylene, C60·3benzene, C60· n-pentane, C60·diethyl ether, C60·chlorobenzene, and C60·benzene·dichloromethane) were determined by single-crystal X-ray diffraction at low temperature. At 90 K, the fullerene and solvate components are generally well-ordered and do not show the orientational disorder that plagues similar structures determined at room temperature. Interactions between the solvate molecules and the fullerene and between adjacent C60 molecules were examined and analyzed. Van der Waals and weak charge-transfer interactions are important to help to organize the individual components in these structures. The weak Lewis acid behavior of C60, such as when it cocrystallizes with diethyl ether or chlorinated solvents, is apparent. In addition, π-stacking interactions are prevalent. The solvates of C60 reported here were frequently obtained from attempts to cocrystallize C60 with another chemical compound. Although the desired cocrystals were never formed, the unincorporated molecules influenced solvate formation.

Model Complexes for the Nip Site of Acetyl Coenzyme A Synthase/Carbon Monoxide (CO) Dehydrogenase: Structure, Electrochemistry, and CO Reactivity.

Aliphatic thiolato-S-bridged tri- and binuclear nickel(II) complexes have been synthesized and characterized as models for the Nip site of the A cluster of acetyl coenzyme A synthase (ACS)/carbon monooxide (CO) dehydrogenase. Reaction of the in situ formed N2Sthiol donor ligands with [Ni(H2O)6](ClO4)2 afforded the trinuclear complexes [Ni{(LMe(S))2Ni}2](ClO4)2·CH3CN (1·CH3CN) and [Ni{(LBr(S))2Ni}2](ClO4)2·5H2O (2·5H2O) following self-assembly. Complexes 1 and 2 react with [Ni(dppe)Cl2] and dppe [dppe = 1,2-bis(diphenylphosphino)ethane] to afford the binuclear [Ni(dppe)Ni(LMe(S))2](ClO4)2·2H2O (3·2H2O) and [Ni(dppe)Ni(LBr(S))2](ClO4)2·0.75O(C2H5)2 [4·0.75O(C2H5)2], respectively. The X-ray crystal structures of 1-4 revealed a central NiIIS4 moiety in 1 and 2 and a NiIIP2S2 moiety in 3 and 4; both moieties have a square-planar environment around Ni and may mimic the properties of the Nip site of ACS. The electrochemical reduction of both terminal NiII ions of 1 and 2 occurs simultaneously, which is further confirmed by the isolation of [Ni{(LMe(S))2Ni(NO)}2](ClO4)2 (5) and [Ni{(LBr(S))2Ni(NO)}2](ClO4)2 (6) following reductive nitrosylation of 1 and 2. Complexes 5 and 6 exhibit νNO at 1773 and 1789 cm-1, respectively. In the presence of O2, both 5 and 6 transform to nitrite-bound monomers [(LMe(S-S))Ni(NO2)](ClO4) (7) and [(LBr(S-S))Ni(NO2)](ClO4)2 (8). The nature of the ligand modification is evident from the X-ray crystal structure of 7. To understand the origin of multiple reductive responses of 1-4, complex [(LMe(SMe))2Ni](ClO4)2 (9) is considered. The central NiS4 part of 1 is labile like the Nip site of ACS and can be replaced by phenanthroline. The treatment of CO to reduce 3 generates a 3red-(CO)2 species, as confirmed by Fourier transform infrared (νCO = 1997 and 2068 cm-1) and electron paramagnetic resonance ( g1 = 2.18, g2 = 2.13, g3 = 1.95, and AP = 30-80 G) spectroscopy. The CO binding to NiI of 3red is relevant to the ACS activity.

Coordination complexes of chromium(0) with a series of 1,3-diphenyl-6-aryl-fulvenes.

The synthesis and structural properties of a series of chromium tricarbonyl 'piano-stool' complexes bearing substituted penta-fulvene ligands were studied. The complexes, tricarbon-yl(1,3,6-tri-phenyl-fulvene)chromium(0) benz-ene hemisolvate, [Cr(C24H18)(CO)3]·0.5C6H6 (I), tricarbon-yl[1,3-di-phen-yl-6-(3-vinyl-phen-yl)fulvene]chromium(0), [Cr(C26H20)(CO)3] (II), and tricarbon-yl[1,3-diphenyl-6-(pyren-1-yl)fulvene]chromium(0), [Cr(C34H22)(CO)3] (III), each have a distorted octa-hedral geometry, with the fulvene coordinated in a π-η2:π-η2:π-η2 fashion. Significant deviation of the exocyclic fulvene double bond from the cyclo-penta-diene plane accompanies coordination. Evidence of non-covalent π-π inter-actions was observed in both (I) and (III), with centroid-to-centroid distances ranging from 3.330 (8) to 3.494 (8) Å.

Utilization of a Nonemissive Triphosphine Ligand to Construct a Luminescent Gold(I)-Box That Undergoes Mechanochromic Collapse into a Helical Complex.

Luminescent gold(I) complexes ([Au6(Triphos)4Cl](PF6)5·2(CH3C6H5), [Au6(Triphos)4Cl](AsF6)5·8(CH3C6H5), and [Au6(Triphos)4Cl](SbF6)5·7(CH3C6H5) where Triphos = bis(2-diphenylphosphinoethyl)phenylphosphine) with a boxlike architecture have been prepared and crystallographically characterized. A chloride ion resides at the center of the box with two of the six gold(I) ions nearby. Mechanical grinding of blue luminescent crystals containing the cation, [Au6(Triphos)4Cl]5+, results in their conversion into amorphous solids with green emission that contain the bridged helicate cation, [µ-Cl{Au3(Triphos)2}2]5+. A mechanism of the mechanochromic transformation is proposed. The structures of the blue-emitting helicate, [Au3(Triphos)2](CF3SO3)3·4(CH3C6H5)·H2O, and the green-emitting bridged-helicate, [µ-Cl{Au3(Triphos)2}2](PF6)5·3CH3OH have been determined by single crystal X-ray diffraction.

Bis-phenylethynyl polyhedral oligomeric silsesquioxanes: new high-temperature, processable thermosetting materials.

Bis-phenylethynyl polyhedral oligomeric silsesquioxane (bis-PE-POSS) compounds were synthesized and thermally cured yielding crosslinked materials. After curing at 370 °C, thermal decomposition occurs near 600 °C under nitrogen. These materials were synthesized by condensation of a new phenylethynyl-functional dichlorosilane onto tetrasilanol phenyl POSS, yielding two geometric isomers.

Mixed valence copper-sulfur clusters of highest nuclearity: a Cu8 wheel and a Cu16 nanoball.

Fully spin delocalized mixed valence copper-sulfur clusters, 1 and 2, supported by µ4-sulfido and NSthiol donor ligands are synthesized and characterized. Wheel shaped 1 consists of Cu2S2 units. The unprecedented nanoball 2 can be described as S@Cu4(tetrahedron)@O6(octahedron)@Cu12S12(cage) consisting of both Cu2S2 and (µ4-S)Cu4 units. The Cu2S2 and (µ4-S)Cu4 units resemble biological CuA and CuZ sites respectively.

Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials.

The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements.

Regioselective Synthesis and Crystallographic Characterization of Isoxazoline-Ring-Fused Derivatives of Sc3N@Ih-C80 and C60.

Highly regioselective 1,3-dipolar cycloaddition of 3,5-dichloro-2,4,6-trimethoxybenzonitrile oxide (1) to Sc3N@Ih-C80 or C60 affords the corresponding isoxazoline-ring-fused derivatives Sc3N@Ih-C80(C10H9O4NCl2) (2a) and C60(C10H9O4NCl2) (2b). 2a represents the first example of an endohedral metallofullerene derivative with an isoxazoline ring. Crystallographic and NMR spectroscopic studies reveal a [5,6]-bond addition pattern in 2a but a [6,6]-bond addition manner in 2b.

Isolation and Crystallographic Characterization of Gd3N@D2(35)-C88 through Non-Chromatographic Methods.

While several nonchromatographic methods are available for the isolation and purification of endohedral fullerenes of the type M3N@Ih-C80, little work has been done that would allow other members of the M3N@C2n family to be isolated with minimal chromatography. Here, we report that Gd3N@D2(35)-C88 can be isolated from the multitude of endohedral and empty cage fullerenes present in carbon soot obtained by electric-arc synthesis using Gd2O3-doped graphite rods. The procedure developed utilizes successive precipitation with the Lewis acids CaCl2 and ZnCl2 followed by treatment with amino-functionalized silica gel. The structure of the product was identified by single-crystal X-ray diffraction.

[U(bipy)4 ]: A Mistaken Case of U0 ?

After more than 50 years, the synthesis and electronic structure of the first and only reported "U0 complex" [U(bipy)4 ] (1) has been reinvestigated. Additionally, its one-electron reduced product [Na(THF)6 ][U(bipy)4 ] (2) has been newly discovered. High resolution crystallographic analyses combined with magnetic and computational data show that 1 and its derivative 2 are best described as highly reduced species containing mid-to-high-valent uranium ligated by redox non-innocent ligands.

Copper coordinated ligand thioether-S and NO2(-) oxidation: relevance to the CuM site of hydroxylases.

In order to gain insight into the coordination site and oxidative activity of the CuM site of hydroxylases such as peptidylglycine α-hydroxylating monooxygenase (PHM), dopamine ß-monooxygenase (DßM), and tyramine ß-monooxygenase (TßM), we have synthesized, characterized and studied the oxidation chemistry of copper complexes chelated by tridentate N2Sthioether, N2Osulfoxide or N2Osulfone donor sets. The ligands are those of N-2-methylthiophenyl-2'-pyridinecarboxamide (HL1), and the oxidized variants, N-2-methylsulfenatophenyl-2'-pyridinecarboxamide (HL1(SO)), and N-2-methylsulfinatophenyl-2'-pyridinecarboxamide (HL1(SO2)). Our studies afforded the complexes [(L1)Cu(II)(H2O)](ClO4)·H2O (1·H2O), {[(L1(SO))Cu(II)(CH3CN)](ClO4)}n (2), [(L1)Cu(II)(ONO)] (3), [(L1(SO))Cu(II)(ONO)]n (4), [(L1)Cu(II)(NO3)]n (5), [(L1(SO))Cu(II)(NO3)]n (6) and [(L1(SO2))Cu(II)(NO3)] (7). Complexes 1 and 3 were described in a previous publication (Inorg. Chem., 2013, 52, 11084). The X-ray crystal structures revealed either distorted octahedral (in 2, 4-6) or square-pyramidal (in 1, 3) coordination geometry around Cu(II) ions of the complexes. In the presence of H2O2, conversion of 1→2, 3-5→6 and 6→7 occurs quantitatively via oxidation of thioether-S and/or Cu(ii) coordinated NO2(-) ions. Thioether-S oxidation of L1 also occurs when [L1](-) is reacted with [Cu(I)(CH3CN)4](ClO4) in DMF under O2, albeit low in yield (20%). Oxidations of thioether-S and NO2(-) were monitored by UV-Vis spectroscopy. Recovery of the sulfur oxidized ligands from their metal complexes allowed for their characterization by elemental analysis, (1)H NMR, FTIR and mass spectrometry.

Beyond the Butterfly: Sc2C2@C(2v)(9)-C86, an Endohedral Fullerene Containing a Planar, Twisted Sc2C2 Unit with Remarkable Crystalline Order in an Unprecedented Carbon Cage.

The synthesis, isolation, and characterization of a new endohedral fullerene, Sc2C88, is reported. Characterization by single crystal X-ray diffraction revealed that it is the carbide Sc2C2@C(2v)(9)-C86 with a planar, twisted Sc2C2 unit inside a previously unseen C(2v)(9)-C86 fullerene cage.

Isolation of CeLu2 N@Ih -C80 through a Non-Chromatographic, Two-Step Chemical Process and Crystallographic Characterization of the Pyramidalized CeLu2 N within the Icosahedral Cage.

By combining two chemical methods of purification, 4 mg of purified CeLu2 N@C80 was readily isolated from 500 mg of carbon soot extract without the use of recycling HPLC, a method which has previously been necessary to obtain pure samples of endohedral fullerenes. In stage 1, CeLu2 N@C80 was selectively precipitated by virtue of its low first oxidation potential (+0.01 V) and the judicious choice of MgCl2 as the Lewis acid precipitant. For stage 2, we used a stir and filter approach (SAFA), which employed the electron-rich NH2 groups immobilized on silica gel to selectively bind residual endohedrals and higher cage fullerenes that were contaminants from stage 1. Crystallographic analysis of CeLu2 N@C80 in the co-crystal CeLu2 N@Ih -C80 ⋅Ni(octaethylporphyrin)⋅2(toluene) reveals that the Ih -C80 cage is present with a pyramidalized CeLu2 N unit inside.

Tethered bisadducts of C60 and C70 with addends on a common hexagonal face and a 12-membered hole in the fullerene cage.

The regioselective synthesis of easily isolable pure bismethano derivatives of C60 and C70 with high steric congestion is described using 1,3-dibenzoylpropane bis-p-toluenesulfonyl hydrazone as the addend precursor. When the addition occurs at two [6,6] ring junctions within the same hexagon, bisadducts with mirror symmetry are obtained for both C60 and C70. When the addition occurs at two [5,6] ring junctions in C60, a symmetrical adduct is formed, which readily undergoes photo-oxygenation and ring opening to yield a fullerene with a hole in the cage. In this work, we also propose a simple and general system to name all of the possible [6,6] bisadduct isomers on C70.

Formation of a Stable Complex, RuCl2(S2CPPh3)(PPh3)2, Containing an Unstable Zwitterion from the Reaction of RuCl2(PPh3)3 with Carbon Disulfide.

New insight into the complexity of the reaction of the prominent catalyst RuCl2(PPh3)3 with carbon disulfide has been obtained from a combination of X-ray diffraction and (31)P NMR studies. The red-violet compound originally formulated as a cationic π-CS2 complex, [RuCl(π-CS2)(PPh3)3]Cl, has been identified as a neutral molecule, RuCl2(S2CPPh3)(PPh3)2, which contains the unstable zwitterion S2CPPh3. In the absence of RuCl2(PPh3)3, there is no sign of a reaction between triphenylphosphine and carbon disulfide, although more basic trialkylphosphines form red adducts, S2CPR3. Despite the presence of an unstable ligand, RuCl2(S2CPPh3)(PPh3)2 is remarkably stable. It survives melting at 173-174 °C intact, is stable to air, and undergoes reversible electrochemical oxidation to form a monocation. When the reaction of RuCl2(PPh3)3 with carbon disulfide is conducted in the presence of methanol, crystals of orange [RuCl(S2CPPh3)(CS)(PPh3)2]Cl·2MeOH and yellow RuCl2(CS)(MeOH)(PPh3)2 also form. (31)P NMR studies indicate that the unsymmetrical dinuclear complex (SC)(Ph3P)2Ru(µ-Cl)3Ru(PPh3)2Cl is the initial product of the reaction of RuCl2(PPh3)3 with carbon disulfide. A path connecting the isolated products is presented.

Synthesis and structure of LaSc2N@C(s)(hept)-C80 with one heptagon and thirteen pentagons.

The synthesis and single-crystal X-ray structural characterization of the first endohedral metallofullerene to contain a heptagon in the carbon cage are reported. The carbon framework surrounding the planar LaSc2N unit in LaSc2N@C(s)(hept)-C80 consists of one heptagon, 13 pentagons, and 28 hexagons. This cage is related to the most abundant Ih-C80 isomer by one Stone-Wales-like, heptagon/pentagon to hexagon/hexagon realignment. DFT computations predict that LaSc2N@C(s)(hept)-C80 is more stable than LaSc2N@D5h-C80, and suggests that the low yield of the heptagon-containing endohedral fullerene may be caused by kinetic factors.

Gadolinium-containing endohedral fullerenes: structures and function as magnetic resonance imaging (MRI) agents.

Gadolinium-containing endohedral fullerenes represent a new class of effective relaxation agents for magnetic resonance imaging (MRI). The range of different structures possible for this class of molecules and their properties as MRI agents are reviewed here.