John P. Selegue

The cyclo-C3 ligand: trimetallic cyclopropenium complexes of Group 6–8 metals, including the X-ray crystal structure of [{Fe(CO)2(Cp)}3(μ3-C3)][SbF6]

Abstract Several trimetallic cyclopropenium cations have been prepared via reactions of three equivalents of a metallate anion with [C33Cl3][SbF6]. The X-ray crystal structure of [{Fe(CO)2(Cp)}3(μ3-C3)][SbF6] (1) shows a nearly equilateral C3 ring with an iron center bonded to each vertex. The cyclopropenium complexes [{Ru(CO)2(Cp)}3(μ3-C3)][SbF6] (2), [{Mo(CO)3(Cp)}3(μ3-C3)][SbF6] (3), [{W(CO)3(Cp)}3(μ3-C3)][SbF6] (4), and [{Re(CO)5}3(μ3-C3)][SbF6] (5) were spectroscopically characterized. Because of the 3-fold symmetrical nature of these complexes, their NMR spectra display a single cyclo-C3 ring carbon resonance and a single set of resonances for the metal moiety. Compound 1 reacts with Li[BHEt3] and LiMe to give complex reaction mixtures. We were not able to add a fourth metal center to the C3 ring of 1. The spectroscopically characterized C9 complex [{Fe(CO)2(Cp)}3{μ3-C3(CC)3}][SbF6] (6), prepared by the reaction of three equivalents of [Fe(CCSiMe3)(CO)2(Cp)] with [C33Cl3][SbF6], was not stable enough to isolate in analytically pure form.

Convenient syntheses of [RuCl(CO)2(Cp)] and [OsCl(CO)2(Cp)]

Abstract [RuCl(CO) 2 (Cp)] ( 1 ) is obtained in two simple steps from [RuCl 3 (H 2 O) x ]. [RuCl 2 (CO) 3 ] 2 , produced by refluxing [RuCl 3 (H 2 O) x ] in hydrochloric and formic acids, reacts cleanly with [SiMe 3 (C 5 H 5 )] to give [RuCl(CO) 2 (Cp)] ( 1 ) in 74% overall yield from [RuCl 3 (H 2 O) x ]. [OsCl(CO) 2 (Cp)] ( 2 ) is similarly obtained in four steps from [OsO 4 ]. Known conversion Of [OsO 4 ] to [NH 4 ] 2 [OsCl 6 ], reduction to [OsCl 3 ] and carbonylation to [OsCl 2 (CO) 3 ] 2 in a tube furnace, and finally reaction with [SiMe 3 (C 5 H 5 )] give [OsCl(CO) 2 (Cp)] ( 2 ) in 26% overall yield from [OsO 4 ]. These preparations are a significant improvement over previous published methods, avoiding the intermediacy of [M 3 (CO) 12 ].

The elusive [Ni(H2O)2(15-crown-5)]2+ cation and related co-crystals of nickel(II) hydrates and 15-crown-5.

Initial attempts to make [Ni(H2O)2(15-crown-5)](NO3)2, i.e. to insert the Ni2+ ion into the 15-crown-5 macrocycle, gave the mono- (two polymorphs) and dihydrate of a co-crystal of[Ni(H2O)6](NO3)2 and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane=15C5). Synthetic routes designed to restrict the water available to the Ni2+ cation gave three additional compounds, [Ni(H2O)6](NO3)2-trans-[Ni(H2O)4(MeOH)2]-(NO3)2x2(15C5), cis-[Ni(H2O)4(NO3)2]-trans-[Ni(H2O)4-(NO3)2]x2(15C5) and [Ni(H2O)2(MeCN)(NO3)2]x15C5x-MeCN. All five compounds contain Ni2+ ions with two trans aqua ligands. In all six structures these aqua ligands make hydrogen bonds to the 15C5 molecules to form stacks in which the Ni complexes and 15C5 molecules alternate. The structures are surprisingly complicated: all are co-crystals,some are also solvates, and most have Z0 > 1. The target compound was finally prepared by heating pale green crystals of [Ni(H2O)6](NO3)2x15C5x2H2O to over 350 K and then cooling the resulting mixture of yellow crystals and solution to room temperature. Formation of the target compound seems to be favored at higher temperatures by a positive Delta(rxn)S(o) and an increased rate of ligand exchange.

Ternary composites of delaminated-MnO2/PDDA/functionalized-CNOs for high-capacity supercapacitor electrodes

Composite materials are synthesized by combining chemically functionalized carbon nano-onions (ONCNOs), a polyelectrolyte (polydiallyldimethylammonium chloride, PDDA) and delaminated layered-manganese oxides (MnO2). While carbon nano-onions are among the least studied carbon allotropes to date, extensive research has been reported on various types of crystalline and amorphous MnO2 to overcome their limitations for energy storage applications. We have developed a synergistically tuned synthesis of MnO2-based composites with ONCNOs via a sequential chemical deposition technique to achieve high-capacity supercapacitor electrodes with long-term stability. A composite with 55 wt% MnO2 on PDDA modified ONCNOs exhibits a high-capacitance of 218.6 F g−1 in a symmetric two-electrode cell containing an aqueous electrolyte (1.0 M Na2SO4) with a high-energy density of 6.14 W h kg−1. Analytical techniques, such as high-resolution transmission electron microscopy, X-ray diffraction, atomic force microscopy, thermogravimetric analysis, and electrochemical measurements (cyclic voltammetry, galvanostatic charge–discharge, and impedance), are employed to fully characterize the synthesized materials and to understand their electrochemical behavior. Emphasis is also given to understand the phenomenon that promotes higher capacitance and long-term stability of such composites based on MnO2 redox chemistry.

New intercalation compounds of transition metal dichalcogenides

Abstract In this paper we describe the preparation and characterization of ethylenediamine-intercalated 6R-TaS2 and octylamine-intercalated 2H-TaS2. We also describe attempts to intercalate various electron acceptor species into transition metal dichalcogenides.

Muon investigations of fullerenyl radicals

Four of the five possible isomeric C70Mu radicals have been detected by transversefieldμSR in a C70 powder sample at 298 K. Their assignment is based on the results of semi-empirical MNDO calculations. There are significant changes in intensity and lineshape of the signals at low temperature. The first μSR spectrum of a fullerenyl radical in solution has been obtained.

The synthesis and characterization of 1-formyl-2-acylcyclopentadienylthallium compounds

Abstract The reaction of sodium cyclopentadienide with RCOOEt (R=Me, Ph, 2-thienyl, or OEt) or Bu t COCl followed by Vilsmeier reagent in the presence of excess sodium methoxide produces the 2-substituted-6-dimethylaminofulvenes 1a – e in modest yields. Basic hydrolysis results in the formation of 2-substituted-6-hydroxyfulvenes 2a – e in very good yields. Subsequent deprotonation with TlOEt yields the 1-formyl-2-acyl or carboethoxy cyclopentadienylthallium compounds 3a – e .

A re-investigation of the reaction of [RuCl2(CO)3]2 with C5H5(Me3Si) X-ray structure determination of [Ru(CO)3(η-C5H5)][fac-RuCl3(CO)3]

Abstract The reaction of [RuCl 2 (CO) 3 ] 2 with C 5 H 5 (SiMe 3 ) has been re-investigated. In our hands, in refluxing tetrahydrofuran, the reaction gives consistently [Ru(CO) 3 (η-C 5 H 5 )][ fac -RuCl 3 (CO) 3 ], 1 , and [RuCl(CO) 2 (η-C 5 H 5 )], 2 , in 68% and 12% yield respectively. The reaction of CO with commercially available hydrated OsCl 3 gives [OsCl 2 (CO) 3 ] 2 in 44% yield. The crystal structure of [Ru(CO) 3 (η-C 5 H 5 )][ fac -RuCl 3 (CO) 3 ] is reported; superlattice symmetry is observed.

Preparation and Structure of 3,4,8,9-Tetrachloro-2,5,7,10-tetrahydro[1,6]dithiecine

The reaction of Z-1,4-dibromo-2,3-dichlorobut-2-ene (1) with sodium sulfide leads to 3,4,8,9-tetrachloro-2,5,7,10-tetrahydro[1,6]dithiecine (2) as the principal product, rather than the anticipated 3,4-dichloro-2,5-dihydrothiophene (3). Compound (2) was characterized spectroscopically and its structure determined by X-Ray crystallography.

Highly polarized ruthenium alkynyls with nitrothienyl substituents

Me3SiC/CC4H2S-5-NO2 was synthesized in good yield by palladium-catalyzed cross-coupling of ethynyltrimethylsilane and 2bromo-5-nitrothiophene or 2-iodo-5-nitrothiophene. Reactions of Me3SiC/C(C4H2S)NO2 with a series of ruthenium chloride complexes [RuClLL?(Cp?)] gave the alkynyls [Ru(2-C/CC4H2S-5-NO2)LL?(Cp?)] (L, L ?� /CO, PMe2Ph or PPh3 ;C p ?� /C5H5 or C5Me5). These metal complexes, each with a strongly electron-donating metal center at one end and an electron-accepting organic substituent at the other end of a p-conjugated chain, are strongly polarized and are expected to demonstrate non-linear optical activity. # 2002 Elsevier Science B.V. All rights reserved.