Joseph C. Scanlon

Organometallic intercalation compounds of FeOCl

Abstract The layered transition metal oxyhalide FeOCl has been found to undergo direct intercalation by the organometallic molecular compounds ferrocene and cobaltocene. From x-ray powder diffraction studies, it has been shown that the Van der Waals gap between the FeOCl layers expands by roughly 5A to accomodate the metallocene. With either metallocene, the data accurately fit a body centered orthorhombic unit cell. A structural model consistent with the observations is proposed, based on a simple shift of alternate FeOCl layers by one-half unit cell in the [101] direction (a-c diagonal) accompanied by the interlayer expansion. There is no evidence for ordering within the metallocene layers. The intercalation of ferrocene is especially significant because its first ionization potential (6.88 eV) is substantially higher than those of organometallic compounds previously intercalated into transition metal dichalcogenides.

Magnetic resonance of intercalation compounds of graphite: Questions of ionicity and mobility of inserted species

Abstract Graphite will react at room temperature with Lewis acids as PF 5 and BF 3 in the presence of the oxidant C1F to form intercalation compounds containing closed-shell anions. In the case of “C 16 BF 4 ”, the chemical shifts of both 11 B and 19 F nuclear magnetic resonances point to the existence of BF − 4 , rather than the initial BF 3 , within the graphite planes. The existence of second order quadrupolar coupling of the 11 B resonance suggests, however, possible hybrid BF 3 BF − 4 character, as in B 2 F − 7 , a known dimeric anion of BF 4 and BF 3 . NMR results on 19 F and 31 P in the two compounds “C 14 PF 6 ” and “C 28 PF 6 ” support this hypothesis, as “C 28 PF 6 ” shows only the presence of PF − 6 , but the more concentrated “C 14 PF 6 ” shows composite PF 5 PF − 6 character. Our claim for intercalated anions in these systems is reinforced both by radical cation-type signals in the ESR and by deshielding effects in the 13 C NMR. The narrow linewidths of the nuclear magnetic resonance absorptions of the intercalated species are suggestive of “liquid-like” behavior.

Intercalation of organometallic compounds into layered transition metal oxyhalides

Abstract The syntheses of the new intercalate compounds FeOCl[(EtMe 4 Cp) 2 Fe] 0.16 , VOCl(CoCp 2 ) 0.16 , and TiOCl(CoCp 2 ) 0.16 are reported. Their structures are found by X-ray powder diffraction to be qualitatively the same as those of the previously reported complexes FeOCl(CoCp 2 ) 0.16 and FeOCl(FeCp 2 ) 0.16 . Results of 57 Fe Mossbauer and magnetic susceptibility studies on the latter two compounds are reported, and shown to be consistent with electron transfer from the metallocene to the host upon intercalation.

The interaction of potassium with graphite and other benzenoid systems

Abstract Potassium can reduce benzenoid systems ranging from graphite to bituminous coals. We have examined the nature of this reduction by electron spin resonance of “C 8 K” products formed by heating potassium metal directly with SP-1 graphite, 13 C-labelled “amorphous carbon”, and Spherocarb. Graphite C 8 K possesses a linewidth linearly proportional to temperature, as is the case for sodium metal, and in contrast to the behavior of graphite/acceptor compounds. The other C 8 K compounds show both a narrow and a broad resonance, reflecting respectively benzenoid anions and dispersed potassium metal. In contrast, Illinois #6 coal, when reduced by potassium naphthalenide in tetrahydrofuran at 23°C, shows only slight changes in the ESR spectrum.

X-RAY DIFFRACTION OF N-PARAFFINS AND STACKED AROMATIC MOLECULES: INSIGHTS INTO THE STRUCTURE OF PETROLEUM ASPHALTENES

ABSTRACT X-ray diffraction investigation of normal paraffins and Debye internal interference calculations on stacks of aromatic molecules are used to make inferences about the structure of petroleum asphaltenes. The gamma band, a broad peak near 4.5 A, is associated with weakly ordered paraffins. Stacks of aromatic molecules can give rise to diffraction peaks at d value higher than that of the “(002)” line. X-ray diffraction of the liquids n-hexadecane, decalin, perhydro-fluorene, 1,3 dimethyladamantane, and 1-methyl naphthalene confirms the above insights and demonstrates that diffraction can distinguish among the organic structural types “paraffinic,” “naphthenic,” and “aromatic.”

The preparation and characterization of Ba3Te2O9; a new oxide structure

The structure of Ba3Te2O9 has been determined from x-ray powder diffraction data and by profile refinement of neutron diffraction data. We find tellurium octahedrally coordinated as expected and the same face-shared [B2O9]6− unit as observed in Ba3W2O9. The phase Ba3Te2O9 has, however, a Cs3Fe2F9 type structure (P63mmc, a=5.8603(1)A, c=14.3037(6)A) rather than the Cs3Tl2Cl9 structure (R3c) found for the tungsten analogue. The two oxide structures have the same BaO3 layer sequence but differ only in the spatial arrangement of the [B2O9] groups in the lattice. Infrared and Raman spectra confirm the different site symmetries associated with the different packing of the tungstate and tellurate anions in their respective structures.

Microstructural characterization of the dispersed phases in Al-Ce-Fe system

Analytical electron microscopy studies were conducted on a rapidly solidified Al-8.8Fe-3.7Ce alloy and arc melted buttons of aluminum rich Al-Fe-Ce alloys to determine the characteristics of the metastable and equilibrium phases. The rapidly solidified alloy consisted of binary and ternary metastable phases in the as-extruded condition. The binary metastable phase was identified to be Al6Fe, while the ternary metastable phases were identified to be Al10Fe2Ce and Al20Fe5Ce. The Al20Fe5Ce was a decagonal quasicrystal while the Al10Fe2Ce phase was determined to have an orthorhombic crystal structure belonging to space group Cmmm, Cmm2, or C222. Microscopy studies of RS alloy and cast buttons annealed at 700 K established the equilibrium phases to be Al13Fe4, Al4Ce, and an Al13Fe3Ce ternary phase which was first identified in the present study. The crystal structure of the equilibrium ternary phase was determined to be orthorhombic with a Cmcm or Cmc2 space group. The details of X-ray microanalysis and convergent beam electron diffraction analysis are described.

The disruption of aromatic stacking order in mesophase petroleum coke via reductive alkylation

Abstract The thermolysis of a 510° C vacuum residuum of petroleum under hydrogen can lead to an insoluble coke material of correlation length in the direction of aromatic stacking (L c ) of 7.3 nm, which is more than 3 times greater than that typically found for coals of anthracite rank. In spite of this high degree of stacking order, the coke material can be solubilized via the technique of reductive alkylation. The coke is combined with tetrahydrofuran and potassium metal, and the aromatic “molecules” of the coke form solubilized anions (K° consumption 5–6 mmol/gram). These anions react with alkyl iodides to form alkylated aromatic adducts, of vapor pressure osmometry molecular weight ca. 1000 gram/mole and showing only weak intermolecular paraffin interactions in X-ray diffraction. Thus, a high degree of aromatic stacking, as manifested by a narrow (002) peak in diffraction, does not imply that the material is refractory; the chemical significance of such aromatic-aromatic interactions is currently of interest to those studying both carbon fibers and coal conversion. Heteronuclear correlated 1 H/1b 13 C NMR is used to elucidate the detailed chemistry of the disruption of aromatic stacking.

More on the reaction of graphite/potassium with water

Abstract The first stage intercalation compound of graphite with K°, C 8 K, will react with water at room temperature to yield a solid product containing graphite inserted with potassium cations and water molecules. Temperature-variant 1 H NMR shows that both T 1 and T 2 decrease as temperature decreases from 298 K to 213 K (T 1 > T 2 at these temperatures) with an activation energy of 0.25 eV. Starting with a C 8 K D 2 O product, one can isotopically exchange with H 2 O to yield a product with 17% H 2 O after 48 hours at room temperature, showing the inserted species are not kinetically “encapsulated.” X-ray diffraction, thermogravimetric analysis, and nuclear magnetic resonance are used to distinguish the graphite compound from a mixture of graphite and hydrates of potassium hydroxide.

121Sb nuclear magnetic resonance of a GraphiteSbCl5 intercalation compound

Graphite will react at room temperature with SbCl5 to form a second stage, orthorhombic, intercalation compound of lattice parameters a0 = 849 pm, b0 = 738 pm, and c0 = 1272 pm. 121Sb nuclear magnetic resonance (15 MHz, 23°C) in the dispersive mode reveals a signal of width 7100 Hz located at 384 ppm downfield from SbCl−6. Electron spin resonance (9.5 GHz, 23°C) shows an asymmetric, ca. 95 G wide line of Dysonian center at g = (2.0024±0.0014). These results are consistent with oxidative intercalation of graphite by SbCl5 to form a compound containing both SbCl−6 and SbCl5. Our findings are compared to work on the analogous intercalate C10AsF5 and on the “overoxidized” material formed by reaction of graphite with WF6 and F2.