Showing papers by "Malcolm L. H. Green published in 1991"
TL;DR: In this article, an alternative catalytic strategy for CO2 reform-ing was proposed, which gives excellent yields (90%) from a stoichiometric (1:1) feed of CO2 and CH4.
Abstract: INCREASING concern about world dependence on petroleum oil has generated interest in the more efficient use of natural gas1–4. The conversion of methane to the common feedstock synthesis gas (carbon monoxide and hydrogen) by steam reforming is already well established5, and we have shown recently that yields of syn-thesis gas in excess of 90% can be obtained at moderate tem-peratures and ambient pressure by partial oxidation, with air or oxygen, over supported transition-metal catalysts6,7. The use of carbon dioxide as an oxidant for conversion of natural gas to synthesis gas is well established in steam reforming5, and is also known in CO2 reforming (for example, the Calcor process8,9), in which the use of excess CO2 yields mainly CO. In the present work, we describe an alternative catalytic strategy for CO2 reform-ing which gives excellent yields (90%) from a stoichiometric (1:1) feed of CO2 and CH4. Carbon deposition ('coking'), which is a hazard of CO2-reforming routes, is suppressed here by the use of catalysts based on platinum-group metals. We show that the exothermic partial oxidation of CH2 and the endothermic CO2-reforming reaction can be carried out simultaneously, thus introducing the possibility of tuning the thermodynamics of the process.
753 citations
TL;DR: During MIV, the progressive loss of ventilation and capacity to generate pressure is associated with the early onset and progression of a peripheral fatiguing process within the inspiratory muscles.
Abstract: We have investigated whether the capacity of the inspiratory muscles to generate pressure and flow during a ventilatory load is related to changes in inspiratory muscle relaxation rate. Five highly motivated normal subjects performed voluntary maximal isocapnic ventilation (MIV) for 2 min. Minute ventilation and esophageal, gastric, and transdiaphragmatic pressures were measured breath by breath. We observed that ventilation, peak inspiratory and expiratory pressures, and inspiratory flow rate declined from the start of the run to reach a plateau at 60 s that was sustained for the remainder of the exercise. In a subsequent series of studies, MIV was performed for variable durations between 15 and 120 s. The normalized maximum relaxation rate of unoccluded inspiratory sniffs (sniff MRR, %pressure loss/10 ms) was determined immediately on stopping MIV. Sniff MRR slowed as the duration of MIV increased and paralleled the decline in inspiratory pressure and ventilation observed during the 2-min exercise. No further slowing in MRR occurred when ventilation became sustainable. We conclude that, during MIV, the progressive loss of ventilation and capacity to generate pressure is associated with the early onset and progression of a peripheral fatiguing process within the inspiratory muscles.
30 citations
TL;DR: The chiral indene derivative (4S,5S)-trans-4,5-bis(1H-inden-3-ylmethyl)-2,2-dimethyl-1,3-dioxolane has been prepared and used to synthesise the bis(η-INDENyl) derivatives [ML1Cl2].
Abstract: The chiral indene derivative (4S,5S)-trans-4,5-bis(1H-inden-3-ylmethyl)-2,2-dimethyl-1,3-dioxolane has been prepared and used to synthesise the bis(η-indenyl) derivatives [ML1Cl2][M = Ti, Zr or Hf; H2L1=(4S,5S)-trans-4,5-bis(1H-inden-1-ylmethyl)-2,2-dimethyl-1,3-dioxolane]. The crystal structure of the zirconium compound has been determined. Hydrogenation of the compounds [ML1Cl2] gives the corresponding bis(4,5,6,7-tetrahydroinden-1-ylmethyl) derivatives [ML2Cl2]. The ability of the new metal compounds to catalyse the polymerisation of ethylene and propene has been examined. The compounds together with methylaluminoxane [(OAIMe)n] as cocatalyst are active for polymerisation of ethylene and, for M = Zr, for propene.
28 citations
Patent•
24 Dec 1991
TL;DR: In this paper, a method of converting a reactant gas mixture of CO2, O2 and CH4 into a product gas mixture comprising H2 and CO is proposed. But the method is not suitable for high temperature environments.
Abstract: A method of converting a reactant gas mixture of CO2, O2 and CH4 comprises contacting the reactant gas at 750 - 850 °C with a solid catalyst, which is a d-block transition metal or oxide such as a group VIII metal on a metal oxide support such as alumina, and which selectively converts the reactant gas into a product gas mixture comprising H2 and CO.
24 citations
TL;DR: Measurements of sniff Pnp and Pnp MRR are of limited value in patients with abnormal lung mechanics because the transmission of pleural pressure to the upper airways during brief dynamic maneuvers is impaired in the presence of airway obstruction and lung fibrosis.
Abstract: Sniff esophageal pressure (Pes) and maximal relaxation rate (MRR, percent pressure loss/10 ms) are useful measurements of inspiratory muscle performance, but they require the passage of an esophageal balloon. We have examined the relationship between sniff esophageal and nasopharyngeal pressures (sniff Pes, sniff Pnp) and maximal relaxation rates (Pes MRR, Pnp MRR) in 13 patients with chronic obstructive pulmonary disease (COPD), five with intrapulmonary fibrosis (IPF), and seven with the “shrinking lung syndrome” of systemic lupus erythematosus (SLE). The ratio sniff Pnp/Pes (mean ± SD) was 0.65 ± 0.15 in COPD, 0.76 ± 0.18 in IPF, and 0.91 ± 0.03 in SLE. The ratio Pnp/Pes MRR was 1.20 ± 0.2 in COPD, 1.14 ± 0.12 in IPF, and 1.07 ± 0.13 in SLE. We confirm that the transmission of pleural pressure to the upper airways during brief dynamic maneuvers is impaired in the presence of airway obstruction and lung fibrosis. We conclude that measurements of sniff Pnp and Pnp MRR are of limited value in patients with...
23 citations
TL;DR: In this article, the synthesis and properties of cluster dithiolene compounds are described along with the properties of the cluster salts of tetracyanoquinodimethane.
Abstract: The synthesis and properties of the cluster salts [C]+[A]–{C = Mo4(η-C5H4Pri)4(µ3-S)4,* Mo4(η-C5H4Pri)4(µ3-Se)4, Fe4(η-C5H5)4(µ3-S)4,* Fe4(η-C5H4Me)4(µ3-S)4,* Cr4(η-C5H5)4(µ3-S)4, Cr4(η-C5H4Me)4(µ3-S)4, or Cr4(η-C5H4Me)4(µ3-Se)4; A = Fe4(NO)4(µ3-S)4} and [Mo4(η-C5H4Pri)4(µ3-S)4]2[Os6(CO)18]* are described along with the cluster salts of tetracyanoquinodimethane (tcnq) or tetracyanoethylene (tcne)[Mo4(η-C5H4Pri)4(µ3-S)4][tcnq],*[Fe4(η-C5H5)4(µ3-S)4][tcnq], [Fe4(η-C5H4Me)4(µ3-S)4][tcnq],*[Cr4(η-C5H5)4(µ3-S)4][(tcnq)2],[Cr4(η-C5H4Me)4(µ3-S)4][tcnq], [Cr4(η-C5H4Me)4(µ3-S)4][(tcnq)2], [Cr4(η-C5H4Me)4(µ3-Se)4][tcnq], [Cr4(η-C5H4Me)4(µ3-Se)4][(tcnq)2], [Mo4(η-C5H4Pri)4(µ3-Se)4][tcnq], [Mo4(η-C5H4Pri)4(µ3-Se)4][tcnq]3, and [Cr4(η-C5H4Me)4(µ3-S)4][tcne]. The cluster dithiolene salts [C]n+[Mo{S2C2(CF3)2}3]n–{C = Mo4(η-C5H4Pri)4(µ3-Se)4, Mo4(η-C5H4Pri)4(µ3-S)4, [Mo4(η-C5H4Pri)4(µ3-S)4]2, Cr4(η-C5H4Me)4(µ3-S)4, or Cr4(η-C5H4Me)4(µ3-Se)4} and [Mo4(η-C5H4Pri)4(µ3-S)4][Ni{S2C2(CN)2}2] are also reported. Crystal structures have been determined for the compounds marked* and also for the neutral selenium cubane [Mo4(η-C5H4Pri)4(µ3-Se)4]. The crystal structures of the cluster salts are not always those predicted from idealized ionic model considerations. Electrical conductivities and magnetic properties are described. The compound [Mo4(η-C5H4Pri)4(µ3-S)4][tcnq] has an unusual ribbon arrangement of the tcnq– anions and shows weak antiferromagnetic behaviour with TN≈ 12 K.
23 citations
TL;DR: The new compounds K[W(PMe3)3H5], [K(18crown-6)], [W(C5H5)4Et)H4], K[cis-Re(PME3)4H2], [PMe 3H5(SnBun3)], this paper,
Abstract: The new compounds K[W(PMe3)3H5], [K(18-crown-6)][W(PMe3)3H5](18-crown-6 = 1,4,7,10,13,16-hexaoxacycloctadecane), Na[W(PMe3)3H5], [Na(15-crown-5)][W(PMe3)3H5], (15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane), [{W(PMe3)3H5Li}4], K[W(η-C5H5)(PMe3)H4], [K(18-crown-6)][W(η-C5H5)(PMe3)H4], [K(18-crown-6)][W(η-C5H4Et)(PMe3)H4], K[cis-Re(PMe3)4H2], [K(18-crown-6)][cis-Re(PMe3)4H2], [W(PMe3)3H5(SnBun3)], [W(ηC5H5)(PMe3)H4(SnBun3)], [Re(PMe3)4H2(SnBun3)], [H(η-C5H5)2ZrW(PMe3)3H5], [Cl(η-C5H5)2ZrW(PMe3)3H5], [{(Ph3P)Au}3W(PMe3)3H4]Cl·xCH2Cl2 and [K(18-crown-6)][Mo(η-C5H5)2H] are reported The X-ray crystal structures of [K(18-crown-6)][W(PMe3)3H5], [Na(15-crown-5)][W(PMe3)3H5], [{W(PMe3)3H5Li}4], [K(18-crown-6)][cis-Re(PMe3)4H2], [{(Ph3P)Au}3W(PMe3)3H4]Cl·015CH2Cl2 and [K(18-crown-6)][Mo(η-C5H5)2H] have been determined The crystal structures of [K(18-crown-6)][W(PMe3)3H5] and [Na(15-crown-5)][W(PMe3)3H5] have also been determined by neutron diffraction Evidence for the presence of a degree of covalent bonding in the systems M–H–M′, where M = W and M′= Li, Na or K and M = Re, M′= K, is discussed
22 citations
TL;DR: In this paper, the bridging oxygen atom sits on a crystallographic inversion center giving a linear Nb-O-Nb group with Nb O 1.9434(4) and Nb N 2.8619(5)A.
Abstract: The reaction between [Nb(η-C5H5)2H3] and LiBu followed by SnMe3Cl gives [Nb(η-C5H5)2H2(SnMe3)]2, also produced from [Nb(η-C5H5)2H3] and SnMe3H. Heating 2 with styrene, PMe3, isoprene or but-2-yne gives [Nb(η-C5H5)2L(SnMe3)](L =η-H2CCH–C6H5, 3; PMe3, 4; η-H2CCHCMeCH2, 5; or η-C2Me26). Photolysis of complex 3 in the presence of CO, 2,6-Me2C6H3NC, MeCN, or PMe3 gives [Nb(η-C5H5)2L(SnMe3)](L = CO, 7; 2,6-Me2C6H3NC, 8; η2-MeCN, 9a and 9b; or PMe3, 4). Heating 3 with H2 regenerates 2 and releases styrene. Compound 3, 5 or 6 reacts with SnMe3H to give the bis(stannyl) derivative [Nb(η-C5H5)2H(SnMe3)2]10, which is also formed by prolonged heating of [Nb(η-C5H5)2H2(SnMe3)] with SnMe3H. Photolysis of 3 under CO2 gives a mixture of 7 and [{Nb(η-C5H5)2(SnMe3)}2(µ-O)]11 by cleavage of the CO2 molecule. Compound 11 crystallises in the orthorhombic space group Pbca with a= 8.409(3), b= 21.109(4) and c= 15.582(3)A. The bridging oxygen atom sits on a crystallographic inversion centre giving a linear Nb–O–Nb group with Nb–O 1.9434(4) and Nb–Sn 2.8619(5)A.
21 citations
TL;DR: The findings of this study suggest that erroneous conclusions about the significance of slowing of sniff MRR with fatigue may be made if MRR is determined from voluntary efforts with a peak pressure of less than 60% of control maximum, as may occur with fatigue.
Abstract: We have measured the normalized maximal relaxation rate (MRR, % pressure loss/10 ms) of esophageal and transdiaphragmatic pressures in five normal subjects who performed unoccluded sniffs from FRC, with the peak pressure varying between 10 and 100% of each subject's maximum. MRR was computed as the maximal rate of decay of pressure divided by the peak pressure, with units of %pressure loss/10 ms. We observed that MRR became progressively faster as sniff peak pressure increased in amplitude above 10% maximum. In four subjects this trend was most marked for sniffs of less than 40% maximal pressure, with little change as peak pressure increased further. In a fifth subject this trend continued across the full range of pressure. Thus, MRR may be an effort-dependent variable during voluntary inspiratory maneuvers. We postulate that sniff MRR becomes faster with increasing peak pressure because of progressive activation of fast-twitch type II muscle fibers. The findings of this study suggest that erroneous concl...
16 citations
TL;DR: The µ-alkyne complex 1 reacts with further C2Me2 to give low yields of the mononuclear η-alkne derivative [WCl4(η-C2Me 2)(thf)]2 which has been structurally characterised as discussed by the authors.
Abstract: The complex Na[W2Cl7(thf)5](thf = tetrahydrofuran) reacts with alkynes to afford the dimetallatetrahedrane complexes [W2Cl4(µ-Cl)2(µ-RC2R′)(thf)2](1, R = R′= Me; 4, R = R′= H; 5, R = R′= Et; 6, R = H, R′= Ph) for which the X-ray crystal structures of 1 and 4 have been determined. In contrast, treatment of the related [W2Cl7(thf)2]– ion with C2Me2 yields the η-bound alkyne complex [NBun4][W2Cl4(µ-Cl)3(η-C2Me2)2]7. The µ-alkyne complex 1 reacts with further C2Me2 to give low yields of the mononuclear η-alkyne derivative [WCl4(η-C2Me2)(thf)]2 which has been structurally characterised. Treatment of 2 with pyridine(py) affords the corresponding adduct [WCl4(η-C2Me2)(py)]3. Treatment of 1 with one or two equivalents of [N(PPh3)2]Cl gives the mono- or dianonic derivatives [N(PPh3)2][W2Cl5(µ-Cl)2(µ-C2Me2)(thf)]8 or [N(PPh3)2]2[W2Cl6(µ-Cl)2(µ-C2Me2)]9 respectively. Extended Huckel molecular orbital calculations suggest that tight metal–µ-alkyne binding in the ditungsten complexes [W2Cl4(µ-Cl)2(µ-RC2R′)(thf)2] Suppresses a potential second-order Jahn–Teller distortion in these systems.
15 citations
TL;DR: In this article, structural and spectroscopic evidence is presented for the presence of Nb-H-M interactions, where M = Li, Na or K. The X-ray crystal structure of 11 shows there are two separate ions [Nb(η-C5H5)2(SnMe3)2]− and [K(18crown-6)]+ with no close interionic contacts.
Abstract: The reaction between [Nb(η-C5H5)2H3] and LiBu, LiBu-1,4,7,10-tetraoxacyclododecane(12-crown-4), NaH–1,4,7,10,13-pentaoxacyclopentadecane(15-crown-5), KH-1,4,7,10,13,16-hexaoxacyclo-octadecane(18-crown-6), or NaNH2 gives M[Nb(η-C5H5)2H2](M = Li, 1; or Na, 5) and [M(crown)][Nb(η-C5H5)2H2][M(crown)= Li(12-crown-4)2, Na(15-crown-5)3 or K(18-crown-6)4]. The compound SnMe3Cl reacts with 1 or 4 to give [Nb(η-C5H5)2H2(SnMe3)]. The hydrides [Nb(η-C5H5)2H2(SnMe3)] and [Nb(η-C5H5)2H(SnMe3)2] react with LiBu–12-crown-4, NaNH2–15-crown-5 and KH–18-crown-6 to give [M(crown)][Nb(η-C5H5)2H(SnMe3)][M(crown)= Li(12-crown-4), Na(15-crown-5)7 or K(18-crown-6)8] and [M(crown)][Nb(η-C5H5)2(SnMe3)2][M(crown)= Li(12-crown-4)9, Na(15-crown-5)10 or K(18-crown-6)11], respectively. The X-ray crystal structure of 11 shows there to be two separate ions [Nb(η-C5H5)2(SnMe3)2]– and [K(18-crown-6)]+ with no close interionic contacts. Structural and spectroscopic evidence is presented for the presence of Nb–H–M interactions, where M = Li, Na or K.
TL;DR: In this article, the crystal structure of the η 6 -arene derivative [Zr(η 6-C 6 H 5 Me)(PMe 3 ) 2 Cl 2 ] has been determined.
TL;DR: In this article, the cycloheptatrienyl ligands of ZrCl4 with sodium amalgam were shown to exhibit a non-parallel arrangement of the ligands, and the electronic structures of these ligands were investigated by photoelectron spectroscopy and extended-Huckel molecular-orbital calculations.
Abstract: Reduction of ZrCl4 with sodium amalgam in the presence of cycloheptatriene gives the crystallographically identified [Zr(η6-C7H8)2]1 which exhibits a non-parallel arrangement of the cycloheptatrienyl ligands. This reacts with PMe3 or 1,2-bis(dimethylphosphino)ethane (dmpe) to yield [Zr(η7-C7H7)(η5-C7H9)(PMe3)]2 and [{Zr(η7-C7H7)(η5-C7H9)}2(dmpe)]3 respectively. Treatment of compound 1 with (AlEt2Cl)2 in tetrahydrofuran (thf) yields [{Zr(η7-C7H7)(thf)(µ-Cl)}2]4 which reacts with N,N,N′,N′-tetramethylethylenediamine, PMe3, dmpe and 1,2-dimethoxyethane to produce [Zr(η7-C7H7)(Me2NCH2CH2NMe2)Cl]5, [Zr(η7-C7H7)(PMe3)2Cl]6, [Zr(η7-C7H7)(dmpe)Cl]7 and [Zr(η7-C7H7)(MeOCH2CH2OMe)Cl]8, respectively. The electronic structures of 1 and [Zr(η7-C7H7)(η5-C7H9)]11 have been investigated by photoelectron spectroscopy and extended-Huckel molecular-orbital calculations.
TL;DR: The new compounds [Nb(η-C6H5Me)(PMe3)3] as discussed by the authors have been prepared and evidence for the anions are presented.
Abstract: The new compounds [Nb(η-C6H5Me)(PMe3)3R](R = H or SiMe3), [Nb(η-C6H5Me)(tmps)], [Nb(η-C6H5Me)(tmps)H][tmps = MeSi(CH2PMe2)3], [Nb(η-C6H5Me)(η-C5H5)(PMe3)], [Nb(η-C6H5Me)(η-C9H7)(PMe3)], [Nb(η5-C9H7)(CO)3(PMe3)], [Nb(η-C6H5Me)(η5-C7H9)(PMe3)], [Nb(η-C7H7)(η4-C7H8)(PMe3)], [Nb(CO)3(PMe3)4][Nb(CO)5(PMe3)], [Nb(η-C7H7)(CO)2(PMe3)], [Nb(η-C6H5Me)2X](X = Br, I, Me, Ph or CH2Ph), [{Nb(η-C6H5Me)(µ-SR)2}2](R = CH2Ph, Me or Bu) and [{Mo(η-C6H5Me)(µ-SePh)2}2][PF6]2 have been prepared (indicates the crystal structure has been determined). Evidence for the anions [Nb(η-C6H5Me)(PMe3)3]– and [Nb(η-C6H5Me)(tmps)]– is presented.
TL;DR: The unsupported WW double bond of W2(η-C5H4R)2X4 has been characterized in this article, and the µ-phosphido complex has been crystallographically characterised.
Abstract: The unsupported WW bond of [W2(η-C5H4R)2X4](X = Cl, R = Pri1a or Me 1b; X = Br, R = Pri2) readily undergoes oxidative-addition reactions with HY [Y = H, Cl, SR′(R′= Me, Et, Pri, Ph or But), or PPhR′(R′= H or Ph)] to afford the corresponding derivatives [W2(η-C5H4R)2X4(µ-H)(µ-Y)] in good yields. For 1a the addition of H2 is reversible with reductive elimination occurring readily at ca. 50 °C under reduced pressure. The µ-phosphido complex [W2(η-C5H4Pri)2Cl4(µ-H)(µ-PPh2)] has been crystallographically characterised and possesses a WW double bond [2.6558(3)A]. The µ-thiolato complexes [W2(η-C5H4R)2Cl4(µ-H)(µ-SR′)] are fluxional and undergo inversion at the µ-S atom; ΔG‡ values for this process have been determined and increase in the order R′= But < Pri < Ph < Et < Me. The µ-chloro complexes [W2(η-C5H4R)2Cl4(µ-Cl)(µ-H)] undergo a different fluxional process which effectively involves rotation of the (µ-Cl)(µ-H) fragment about the W–W vector. The complexes [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = H or PPh2) react with PMe3 to give the corresponding adducts [W2(η-C5H4Pri)2Cl3(µ-Cl)(µ-H)(µ-Y)(PMe3)], the X-ray crystal structure of the µ-phosphido complex (Y = PPh2) having been determined. In contrast, treatment of [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = Cl or SR′) with an excess of PMe3 affords the mononuclear complex [W(η-C5H4Pri)Cl(PMe3)3].
TL;DR: The amino-functionalised ferrocene derivative FcCH2CH2NH2 has been intercalated under mild conditions into both single-crystal and microcrystalline samples of the layered host lattices MoO3, 2H-TaS2, and α-Zr(HPO4)2·H2O as mentioned in this paper.
Abstract: The amino-functionalised ferrocene derivative FcCH2CH2NH2[Fc = Fe(η-C5H4)(η-C5H4)] has been intercalated under mild conditions into both single-crystal and microcrystalline samples of the layered host lattices MoO3, 2H-TaS2, and α-Zr(HPO4)2·H2O. The X-ray powder patterns for the new intercalates have been indexed and yield interlayer lattice expansions of 13.09, 5.89 and 14.54 A, respectively. The large interlayer expansions of 13.09 and 14.5 A observed for the intercalates of both MoO3 and α-Zr(HPO4)2·2H2O suggest the formation of a bilayer of guest molecules within these host lattices. The 57Fe Mossbauer spectrum of MoO3(FcCH2CH2NH2)0.36 exhibits a quadrupole doublet with an isomer shift δFe= 0.442 mm s–1 and quadrupole splitting Δ= 2.344 mm s–1, indicating the presence of unoxidised ferrocene molecules within the oxide layers. Solid-state 13C CP-MAS NMR spectra of MoO3(FcCH2CH2NH2)0.36 are consistent with the existence of both neutral FcCH2CH2NH2 and FcCH2CH2NH3+ moieties within the host. In addition, the changes in the electronic structure of MoO3 that accompany the interacalation of FcCH2CH2NH2 have been investigated by solid-state photoelectron spectroscopy.
TL;DR: In this article, the triply-bonded dimers were treated with C5H4R 2Cl4 followed by HCl gas, and the X-ray crystal structure for R = Pri, R′= Et revealed a perpendicular bridging EtCNH ligand.
Abstract: Treatment of the WW triply-bonded dimers [W2(η-C5H4R)2Cl4](R = Pri or Me) with R′CN (R′= Me, Et, or Ph) followed by HCl gas affords the complexes [W2(η-C5H4R)2Cl4(µ-Cl)(µ-R′CNH)] in quantitative yield; the X-ray crystal structure for R = Pri, R′= Et reveals a perpendicular bridging EtCNH ligand.
TL;DR: In this paper, a double-rearrangement mechanism with polyhedral edge stretches through a monocapped-square-antiprismatic geometry to a tricapped-trigonal-prismatic intermediate in which all phosphines occupy capping positions.
Abstract: W(PMe{sub 3}){sub 3}H{sub 6} (1), an archetypal nine-coordinate transition-metal complex, has been studied in the crystalline state by variable-temperature {sup 13}C and {sup 31}P CP/MAS NMR spectroscopy. The NMR spectra are consistent with a tricapped-trigonal-prismatic geometry for the complex, with two phosphine ligands in eclipsed prismatic sites and the third capping the prismatic face opposite the other two. The two prismatic phosphines are shown to be on inequivalent sites. At temperatures above 340 K, exchange broadening shows the occurrence of ligand functionality interchange between the different phosphine environments. Analysis of these line shapes and magnetization-transfer data, in the slow limit of exchange, for the both {sup 13}C and {sup 31}P nuclei shows activation parameters of E{sub a} = 148.8 {plus minus} 15 kJ mol{sup {minus}1} and A = 6.6 {times} 10{sup 23} s{sup {minus}1} for the ligand-functionality-interchange process. The most likely mechanism involves a double-rearrangement mechanism with polyhedral edge stretches through a monocapped-square-antiprismatic geometry to a tricapped-trigonal-prismatic intermediate in which all phosphines occupy capping positions. This allows complete scrambling of the ligand functionality, in a manner such that the spatial movement of the phosphine ligands within the crystalline frame need only be relatively small. An additional dynamic process, involving amore » tripod reorientation of the PMe{sub 3}rotors, has been detected by dipolar broadening of the {sup 13}C NMR spectra. 31 refs., 10 figs., 2 tabs.« less
TL;DR: In this article, the electrochemistry of 4′-nitrobenzo-15-crown-5 with phenyl isocyanate has been investigated by cryclic voltammetry in acetonitrile.
TL;DR: The one-pot syntheses of [Nb(η6-C7H8)(PMe3)2Cl2] and [nb(nbCl4(thf)2] (thf = tetrahydrofuran) have provided a convenient route to the virtually unexplored η-cycloheptatrienyl niobium system as discussed by the authors.
TL;DR: The main purpose of as discussed by the authors is to discuss the likely areas of future developments in the field of organotransition metal chemistry in the next decade, which will reflect in part the historical momentum of past discoveries and therefore it is appropriate briefly to review the progress made in the last forty or so years.
Abstract: The main purpose of this article is to discuss the likely areas of future developments in the field of organotransition metal chemistry in the next decade. Inevitably these will reflect in part the historical momentum of past discoveries and therefore it is appropriate briefly to review the progress made in the field in the last forty or so years
TL;DR: The relative sign of the 2J(H-D) coupling constant in (CH2D)TiCl3 has been determined in this article, and it has been shown to be negative.
Abstract: The relative sign of the 2J(H–D) coupling constant in (CH2D)TiCl3 has been redetermined and found to be negative.
Patent•
24 Dec 1991TL;DR: In this article, a method of converting a reactant gas mixture of CO2 compound, O2 and CH4 with a solid catalyst at a temperature between 750 and 850 °C, which catalyst comprises an oxide or a block of transition metal such as a Group VIII metal on a metal oxide support such as alumina, is described.
Abstract: Un procede de conversion d'un melange gazeux reactant compose de CO2, O2 et CH4 consiste a mettre en contact le gaz reactant avec un catalyseur solide a une temperature comprise entre 750 et 850 °C, lequel catalyseur se compose d'un oxyde ou d'un metal de transition du bloc d tel qu'un metal du groupe VIII sur un support d'oxyde metallique tel que l'alumine, et qui convertit de maniere selective le gaz reactant en un melange gazeux final comprenant H2 et CO. A method of converting a reactant gas mixture of CO2 compound, O2 and CH4 involves contacting the reactant gas with a solid catalyst at a temperature between 750 and 850 ° C, which catalyst comprises an oxide or a block of transition metal such as a Group VIII metal on a metal oxide support such as alumina, which selectively converts the reactant gas in a final gas mixture comprising H2 and CO.
TL;DR: The one-pot syntheses of [Nb(η6-C7H8)(PMe3)2Cl2] and [nb(nbCl4(thf)2] (thf = tetrahydrofuran) have provided a convenient route to the virtually unexplored η-cycloheptatrienyl niobium system as mentioned in this paper.
Abstract: The one-pot syntheses of [Nb(η6-C7H8)(PMe3)2Cl2] and [Nb(η-C7H7)(η4-C7H8)(PMe3)] from [NbCl4(thf)2] (thf = tetrahydrofuran) have provided a convenient route to the virtually unexplored η-cycloheptatrienyl niobium system. The X-ray crystal structures of the subsequent derivatives [Nb(η-C7H7)(Me2PCH2CH2PMe2)CO] and 17-electron [Nb(η-C7H7)(PMe3)2I] have been determined.
TL;DR: Pentaborane(9) reacts with [Fe(PMe3)3(η2-CH2PMe2)H] to give [2,3-{FeMe3]2}2(µ-H)B4H9] in yields of up to 1 and 22% respectively; the X-ray crystal structure of (1) shows a nido-pentaborane structure in which a BH3 fragment caps the Fe2B face as mentioned in this paper.
Abstract: Pentaborane(9) reacts with [Fe(PMe3)3(η2-CH2PMe2)H] to give [2,3-{Fe(PMe3)2}2(µ-H)B4H9](1) and [2-{Fe(PMe3)3}B4H8](2) in yields of up to 1 and 22% respectively; the X-ray crystal structure of (1) shows a nido-pentaborane(9) structure in which a BH3 fragment caps the Fe2B face.