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One of the great challenges of inertial confinement fusion and high energy density experiments is understanding the effects of mix on thermonuclear burn. The MARBLE campaign, conceived at Los Alamo...

Differences in molecular mobility between polystyrene foam and Brij-78 wax results in vast differences in the 1H nuclear magnetic resonance (NMR) linewidth. This allows for the convenient determina...

Ferrocene could be adsorbed on activated carbon, carbon nanotube surfaces, graphite, and graphene in the absence of a solvent at room temperature in spite of its high melting point (174 °C). In each case only monolayers formed via self-adsorption and the transition to surplus polycrystalline material was abrupt, with no multiple layers occurring. Variable-temperature multinuclear solid-state NMR spectroscopy was applied to study the mobilities of the surface-adsorbed ferrocene molecules. It has been demonstrated that on favorable supports the major anisotropic interactions that usually broaden the solid-state NMR signals of polycrystalline and amorphous materials were reduced or completely eliminated due to the mobility of the adsorbed ferrocene. In favorable cases the chemical shift anisotropy (CSA) and the dipolar and quadrupolar interactions were reduced to a degree that allowed the recording of the spectra of the solid materials on a conventional solution NMR spectrometer.

The adsorption of the metallocenes ferrocene, doubly deuterated ferrocene, cymantrene and nickelocene, as well as molybdenum hexacarbonyl, proceeds in the absence of a solvent. Large single pieces of silica gel were placed in contact with the solid metallocenes and the adsorption process was visualized on a macroscopic scale and the maximal loadings were determined. 1 H, 2 H, and 13 C solid-state NMR studies confirmed fast isotropic reorientation of the surface-adsorbed metallocene molecules within the pores of the silica. All prevalent anisotropic solid-state interactions were averaged out. The solid diamagnetic and paramagnetic materials were amenable to measurements with a standard solution NMR instrument. All metallocenes adsorbed in a monolayer. In the case of ferrocene and cymantrene, different 13 C MAS signals were obtained for the cyclopentadienyl ring carbon nuclei and assigned to one ring interacting with the surface and one ring pointing away from it. The relative adsorption strengths of ferrocene on different silica supports, nanotubes, and activated carbon were determined by a novel straightforward method recording the desorption temperature. The reversibility of adsorption has been demonstrated by competition experiments using ferrocene, doubly deuterated ferrocene, and cymantrene. Adsorbed nickelocene could be reduced to small Ni0 aggregates on the surface and the catalytic activity of the resulting material for the cyclotrimerization of phenylacetylene was proven.

Reactions of trans-Fe(CO)3(P((CH2)mCH═CH2)3)2 (m = a/4; b/5, c/6, e/8) and Grubbs' catalyst (12-24 mol %, CH2Cl2, reflux) give the cage-like trienes trans- Fe(CO)3(P((CH2)mCH═CH(CH2)m)3 P) (3a-c,e, 60-81%). Hydrogenations (ClRh(PPh3)3, 60-80 °C) yield the title compounds trans- Fe(CO)3(P((CH2)n)3 P) (4a-c,e, 74-86%; n = 2m + 2), which have idealized D3h symmetry. A crystal structure of 4c suggests enough van der Waals clearance for the Fe(CO)3 moiety to rotate within the three P(CH2)14P linkages; structures of E,E,E-3a show rotation to be blocked by the shorter P(CH2)4CH═CH(CH2)4P linkages. Additions of NO(+)BF4(-) give the isoelectronic and isosteric cations [ Fe(CO)2(NO)(P((CH2)n)3 P)](+)BF4(-) (5a-c(+)BF4(-); 81-98%). Additions of [H(OEt2)2](+)BArf(-) (BArf = B(3,5-C6H3(CF3)2)4) afford the metal hydride complexes mer,trans-[ Fe(CO)3(H)(P((CH2)n)3 P)](+)BArf(-) (6a-c,e(+)BArf(-); 98-99%). The behavior of the rotators in the preceding complexes is probed by VT NMR. At ambient temperature in solution, 5a,b(+)BF4(-) and 6a(+)BArf(-) show two sets of P(CH2)n/2 (13)C NMR signals (2:1), whereas 5c(+)BF4(-) and 6b,c(+)BArf(-) show only one. At higher temperatures, the signals of 5b(+)BF4(-) coalesce; at lower temperatures, those of 5c(+)BF4(-) and 6b(+)BArf(-) decoalesce. These data give ΔH(⧧)/ΔS(⧧) values (kcal/mol and eu) of 8.3/-28.4 and 9.5/-6.5 for Fe(CO)2(NO)(+) rotation (5b,c(+)) and 6.1/-23.5 for Fe(CO)3(H)(+) rotation (6b(+)). (13)C CP/MAS NMR spectra show that the Fe(CO)3 moiety in polycrystalline 4c (but not 4a) undergoes rapid rotation between -60 and 95 °C. Approaches to minimizing these barriers and developing molecular gyroscopes are discussed.

Aqueous hydrogen peroxide is widely used as an oxidizing agent in industry and academia. Herein, the hydrogen peroxide adducts of phosphine oxides, [tBu3PO⋅H2O2]2 and [Ph3PO⋅H2O2]2⋅H2O2, are described. Additionally, the corresponding di(hydroperoxy)propane adducts R3PO⋅(HOO)2CMe2 (R=Cy, Ph) were synthesized and characterized. All adducts could be obtained as large single crystals suitable for structural characterization by X-ray crystallography and solid-state NMR spectroscopy. The di(hydroperoxy)propane adducts are soluble in organic solvents which enables oxidation reactions in one phase. As the adducts are solid and molecular, they can easily be applied stoichiometrically. No loss of oxidizing power occurs upon long-term storage of the single crystals at room temperature or the powders at -20 °C.

The tridentate chelate nickel complexes [(CO)Ni{(PPh2 CH2 )3 CMe}] (2), [(CO)Ni{(PPh2 CH2 CH2 )3 SiMe}] (6), and [Ph3 PNi{(PPh2 CH2 CH2 )3 SiMe}] (7), as well as the bidentate complex [(CO)2 Ni{(PPh2 CH2 )2 CMeCH2 PPh2 }] (3) and the heterobimetallic complex [(CO)2 Ni{(PPh2 CH2 )2 CMeCH2 Ph2 PAuCl}] (4), have been synthesized and fully characterized in solution. All (1) H and (13) C NMR signal assignments are based on 2D-NMR methods. Single crystal X-ray structures have been obtained for all complexes. Their (31) P CP/MAS (cross polarization with magic angle spinning) NMR spectra have been recorded and the isotropic lines identified. The signals were assigned with the help of their chemical shift anisotropy (CSA) data. All complexes have been tested regarding their catalytic activity for the cyclotrimerization of phenylacetylene. Whereas complexes 2-4 display low catalytic activity, complex 7 leads to quantitative conversion of the substrate within four hours and is highly selective throughout the catalytic reaction.

Ruthenocene, bis(indenyl)ruthenium, bis(tetrahydroindenyl)ruthenium, cyclododecane, ferrocene, and ferrocene-d2 have been adsorbed on silica surfaces by grinding the polycrystalline materials with silica. The adsorption process proceeds without solvent and is practically complete within 2 h. Its progress is monitored by 1H, 13C, and 2H solid-state NMR spectroscopy. The transition from the crystal lattice to the surface species that are highly mobile is proven by strongly reduced chemical shift anisotropies and diminished dipolar interactions. Furthermore, the residual line widths are reduced. All solid-state NMR spectra indicate that the transition from a monolayer to the crystalline state is abrupt, and no multiple layers form on the surfaces. A correlation between surface coverage and 2H residual line widths has been established. Besides a hydrophobic dry silica surface, wet and TMS-capped silica have been used as supports. The adsorption leads to the highest surface coverages and most mobile species fo...

Ferrocene and chromocene can be adsorbed on silica surfaces by impregnation or by grinding powders of the metallocenes with silica. The vanishing crystal lattice and formation of mobile surface species can in both cases be proven by diminished Chemical Shift Anisotropies and reduced residual linewidths as well as changes in the chemical shifts of the 1H and 13C MAS NMR signals. In contrast to adsorbed ferrocene, the surface-adsorbed chromocene is highly air-sensitive and continues to react with the silica surface within an hour.

The synthesis and characterization of a series of complexes based upon a central triplatinum ditropylium (Tr) unit [Pt 3 Tr 2 ] 2+ containing different halide ligands is reported. The complexes were synthesized in moderate yield and characterized by multi-nuclei NMR spectroscopy, mass spectrometry, microanalysis and X-ray crystallography. In addition it was demonstrated that mixed-metal, palladium–platinum sandwich complexes could also be formed [Pd n Pt 3-n Tr 2 X 3 ][ Y ] ( X = Cl, Br and I, Y = NBu 4 + or PBu 4 + ).

Solid-state NMR spectroscopy of selected phos-phine oxides adsorbed on silica surfaces establishes thesurface mobilities, even of phosphine oxides with highmelting points. Crystal structures of the adductsPh 3 PO·HOSiPh 3 and Cy 3 PO·H 2 O indicate that the interac-tions with silica involve hydrogen bonding of the P=Ogroup to adsorbed water and surface silanol groups.Phosphine oxides represent an immensely important class ofcompounds. [1] They are by-products of phosphine chemistry,and are generated as stoichiometric co-products of the Wittig,Appel, and other reactions. They are also indispensable probesfor surface acidities of oxides [2] and recently received attentionin the decomposition of warfare agents. [3] Another long-stand-ing question in the field of immobilized catalysts [4] is whetheradsorbed phosphine oxides mimic the 31 P MAS (magic anglespinning) NMR signals of phosphine linkers quaternized toform phosphonium salts. [5] Despite their importance, the sur-face chemistry of phosphine oxides is not well documented.Herein, we prove using solid-state NMR techniques that evenphosphine oxides with high melting points possess heretoforeunappreciated surface mobilities in the absence of solvents.The silica-adsorption process of phosphine oxides proceeds atambient temperature by co-grinding the dry components.Crystal structures of model compounds show that interactionswith surface silanol groups and adsorbed water mediate theadsorption and mobility, which correlates with leaching data invarious solvents.The