Publications
54 results found
Ashley AE, Thompson AL, O'Hare D, 2009, Non-Metal-Mediated Homogeneous Hydrogenation of CO2 to CH3OH., Angew. Chem., Int. Ed., Vol: 48, Pages: 9839-S9839/4, ISSN: 1433-7851
The selective hydrogenation of CO2 to methanol was carried out using an FLP [frustrated Lewis pairs]-based nonmetal-mediated process at low pressures (1-2 atm). The first step is heterolytic activation of H and subsequent insertion of CO2 into a B-H bond of 2,2,6,6-tetramethylpiperidine [TMP] and B(C6F5)3 forming [TMPH][HB(C6F5)3].; introduction of CO2 produced the formatoborate complex [TMPH]-[HCO2B(C6F5)3]. Selective distn. at 100° resulted in decompn. of the intermediate complex with recovery of methanol. The process provides for utilization of CO2 greenhouse gas, solving problems related to storage of sequestered gas, with further benefit of prodn. of methanol as fuel and chem. feedstock. [on SciFinder(R)]
Ashley AE, Cowley AR, Green JC, et al., 2009, Synthesis and Characterisation of Low-Coordinate Transition-Metal Complexes Stabilised by Sterically Demanding Carbazolido Ligands., Eur. J. Inorg. Chem., Pages: 2547-2552, ISSN: 1434-1948
The synthesis and characterization of the homoleptic transition-metal complexes (1,8-Ph2-3,6-Me2C12H4N)2M (M = Cr, 1; M = Mn, 2; M = Fe, 3; M = Co, 4) are described. Formally two-coordinate, the solid-state structures of 2 and 3 reveal near-linear N-M-N geometries and significant bending of the flanking Ph groups towards the metal centers. Solid-state magnetic measurements reveal high spin metal centers in 1-4; computational calcns. for the model complexes M(1,8-Ph2C12H6N)2 (M = Cr-Co) confirm the presence of high-spin configurations within these bis-carbazolido compds. and an orbital ordering of δ < π < σ for these systems. [on SciFinder(R)]
O'Hare DM, Ashley AE, 2008, Process for preparation of substituted pentalene derivatives and their transition metal sandwich complexes.
A process for prepn. of 1-R1-2-R2-3-R3-4-R4-5-R5-6-R6-pentalenes (1; R1-R6 = C1-40 organyl, halo; preferably R1-R6 = C1-4 alkyl; preferably R5 = R5, R1 = R4, R3 = R6; more preferably R1-R6 are the same, R1-R6 = Me), 1-R1-2-R2-3-R3-4-R4-5-R5-6-R6-1,2-dihydropentalenes (2, same R), alkali and alk. earth salts of 1,2-dihydropentalenes MSx[1·H]n (M = Group IA, IIA metal, S = chelating solvent, preferably 1,2-dimethoxyethane, TMEDA; x = 0-8; n = 1,2) and Group IIIB-VIII transition metal complexes, comprising η3-η8 dihydropentalenide ligands, including sandwich, ansa-sandwich and binuclear sandwich compds., useful as catalysts for hydrogenation, Fischer-Tropsch reaction, hydroformylation, hydroamination, hydrosilylation, polymn., oxidn., cyclotrimerization, and cycloaddn. reactions, is described. The process comprises electrophilic alkylation of 3,7-dioxobicyclo[3.3.0]octane-2,4,6,8-tetracarboxylate ester, decarboxylation yielding the 2-R1-4-R3-6-R4-8-R6-bicyclo[3.3.0]octane-3,7-dione (3), dehydrogenation to the substituted 1,2,4,5-tetrahydropentalene-2,5-dione (4), redn. to 1,3,4,6-tetrahydropentalene-2(2H),5(5H)-dione (5), alkylation of the dione 5 by an organometallic reagent, preferably by RCeCl2 at -70°, yielding 1-R1-2-R2-3-R3-4-R4-5-R5-6-R6-1,2,3,4,5,6-hexahydropentalene-2,5-diol (6), dehydration of the diol 6, preferably by reaction with conc. H2SO4 to give the 1,2- or 1,4-dihydropentalenes (1a) followed by optional deprotonation, transmetalation, stannylation or complexation reactions. In an example, 1,2,3,4,5,6-hexamethyl-1,2-dihydropentalene (1aa)was prepd. in a multistep procedure starting from tetra-Me 3,7-dihydroxybicyclo[3.3.0]octa-2,6-diene-2,4,6,8-tetracarboxylate by MeI/K2CO3 methylation, decarboxylation, Br2 oxidn. to 2,4,6,8-tetramethylbicyclo[3.3.0]octa-2,5-diene-3,7-dione, Zn redn. to 2,4,6,8-tetramethylbicyclo[3.3.0]octa-1(5)-ene-3,7-dione and methylation by MeCeCl2 in a 60% yield. In another example, the iron complex [Fe2(CO)4
Ashley AE, Cooper RT, Wildgoose GG, et al., 2008, Homoleptic Permethylpentalene Complexes: "Double Metallocenes" of the First-Row Transition Metals., J. Am. Chem. Soc., Vol: 130, Pages: 15662-15677, ISSN: 0002-7863
The synthesis of the bimetallic permethylpentalene complexes Pn*2M2 (M = V, Cr, Mn, Co, Ni; Pn* = C8Me6) was accomplished, and all of the complexes were structurally characterized in the solid state by single-crystal x-ray diffraction. Pn*2V2 (1) and Pn*2Mn2 (3) show very short intermetallic distances that are consistent with metal-metal bonding, while the Co centers in Pn*2Co2 (4) exhibit differential bonding to each side of the Pn* ligand that is consistent with an η5:η3 formulation. The Pn* ligands in Pn*2Ni2 (5) are best described as η3:η3-bonded to the metal centers. 1H NMR studies indicate that all of the Pn*2M2 species exhibit D2h mol. symmetry in the soln. phase; the temp. variation of the chem. shifts for the resonances of Pn*2Cr2 (2) indicates that the mol. has an S = 0 ground state and a thermally populated S = 1 excited state and can be successfully modeled using a Boltzmann distribution (ΔH° = 14.9 kJ mol-1 and ΔS° = 26.5 J K-1 mol-1). The solid-state molar magnetic susceptibility of 3 obeys the Curie-Weiss law with μeff = 2.78 μB and θ = -1.0 K; the complex is best described as having an S = 1 electronic ground state over the temp. range 4-300 K. Paradoxically, attempts to isolate the double ferrocene equiv., Pn*2Fe2, led only to the isolation of the permethylpentalene dimer Pn*2 (6). Soln. electrochem. studies were performed on all of the organometallic compds.; 2-5 exhibit multiple quasi-reversible redox processes. D. functional theory calcns. were performed on this series of complexes to rationalize the obsd. structural and spectroscopic data and provide ests. of the M-M bond order. [on SciFinder(R)]
Ashley A, Balazs G, Cowley A, et al., 2007, Bis(permethylpentalene)cerium - another ambiguity in lanthanide oxidation state., Chem. Commun. (Cambridge, U. K.), Pages: 1515-1517, ISSN: 1359-7345
The title compd. Ce(η8-C8Me6)2 (1) exists in a valency close to Ce(III) with some Ce(IV) and provides an example of the Kondo effect in a discrete mol. Treating Li2(C8Me6)(TMEDA)0.19 with CeCl3 in THF, followed by treatment with 1,2-dichloroethane as mild oxidant gave 61% 1. The structure of 1 was detd. by x-ray crystallog. and also optimized geometries were calcd. by DFT-B3LYP methods. [on SciFinder(R)]
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