Publications
27 results found
Stadler B, Meng HHY, Belazregue S, et al., 2023, PCP Pincer Complexes of Titanium in the+3 and+4 Oxidation States, ORGANOMETALLICS, Vol: 42, Pages: 1278-1285, ISSN: 0276-7333
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- Citations: 1
Kramer T, Chadwick FM, Macgregor SA, et al., 2023, <SUP>???????</SUP>???????Solid-State Confinement Effects in Selective exo-H/D Exchange in the Rhodium s-Norbornane Complex [(Cy<sub>2</sub>PCH<sub>2</sub>CH<sub>2</sub>PCy<sub>2</sub>)Rh(?<SUP>2</SUP>:?<SUP>2</SUP>-C<sub>7</sub>H<sub>12</sub>)][BAr<SUP>F</SUP><sub>4</sub>], HELVETICA CHIMICA ACTA, Vol: 106, ISSN: 0018-019X
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- Citations: 1
Webster L, Kramer T, Chadwick FM, 2022, Synthesis and reactivity of titanium 'POCOP' pincer complexes, DALTON TRANSACTIONS, Vol: 51, Pages: 16714-16722, ISSN: 1477-9226
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- Citations: 2
Chadwick FM, Krämer T, Webster L, 2022, Synthesis and Reactivity of titanium ‘POCOP’ pincer complexes
<jats:p>The ‘POCOP’ pincer ligand, [2,6-(R2PO)2C6H3], has been attached to titanium in both Ti(III) and Ti(IV) complexes for the first time. Using a lithium-halogen exchange route [2.6-(R2O)2C6H3]Li ([RPOCOP]Li) can be synthesised. Both the iso-propyl and tert-butyl derivatives can be made, but only the latter isolated. These can be reacted with the Ti(III) and Ti(IV) synthons to make [tBuPOCOP]TiCl2 (1), [tBuPOCOP]TiCl3 (2) and {[iPrPOCOP]TiCl2(µ-Cl)}2 (4). In the presence of Ti(IV), THF and [RPOCOP]Li an unprecedented ligand rearrangement occurs. 1 can be derivatised with alkylating agents to make bis-methyl, phenyl and neopentyl complexes. The last of these can activate H2 to make a rare example of a titanium hydride chloride, with the metal pincer fragment staying attached. This opens the door for this archetypical pincer ligand to be used with early transition metals.</jats:p>
Idelson C, Webster L, Kramer T, et al., 2020, Asymmetric bis-PNP pincer complexes of zirconium and hafnium - a measure of hemilability, DALTON TRANSACTIONS, Vol: 49, Pages: 16653-16656, ISSN: 1477-9226
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- Citations: 1
Idelson C, Webster L, Krämer T, et al., 2020, Asymmetric Bis-PNP Pincer Complexes of Zirconium and Hafnium - a Measure of Hemilability
<jats:p>Asymmetrically-bound pyrrollide-based bis-PNP pincer complexes of zirconium and hafnium</jats:p><jats:p>have been formed. The [κ2-PNPPh][κ3-PNPPh]MCl2 species are in direct contrast to previous</jats:p><jats:p>zirconium PNP pincer complexes. The pincer ligands are fluxional in their binding and the</jats:p><jats:p>energy barrier for exchange has been approximated using VT-NMR spectroscopy and the</jats:p><jats:p>result validated by DFT calculations.</jats:p>
Landman IR, Suleymanov AA, Fadaei-Tirani F, et al., 2020, Bronsted and Lewis acid adducts of triazenes, DALTON TRANSACTIONS, Vol: 49, Pages: 2317-2322, ISSN: 1477-9226
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- Citations: 12
Tan J-F, Bormann CT, Perrin FG, et al., 2019, Divergent Synthesis of Densely Substituted Arenes and Pyridines via Cyclotrimerization Reactions of Alkynyl Triazenes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 141, Pages: 10372-10383, ISSN: 0002-7863
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- Citations: 49
Chadwick FM, Curchod BFE, Scopelliti R, et al., 2019, Azo-MICs: Redox-Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 58, Pages: 1764-1767, ISSN: 1433-7851
Chadwick FM, Curchod BFE, Scopelliti R, et al., 2019, Azo‐MICs: Redox‐Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes, Angewandte Chemie, Vol: 131, Pages: 1778-1781, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo‐MICs). The properties of these ligands were examined by synthesizing Rh<jats:sup>I</jats:sup>, Au<jats:sup>I</jats:sup>, and Pd<jats:sup>II</jats:sup> complexes. Experimental (NMR, IR) and theoretical investigations show that Azo‐MICs are potent σ‐donor ligands. Yet, they feature a small singlet–triplet gap and very low‐lying LUMO levels. The unique electronic properties of Azo‐MICs allow for reversible one‐electron reductions of the metal complexes, as evidenced by cyclic voltammetry.</jats:p>
Clement DD, Binding SC, Arnold TAQ, et al., 2019, Synthesis and characterization of permethylpentalene titanium aryloxide and alkoxide complexes, Polyhedron, Vol: 157, Pages: 146-151, ISSN: 0277-5387
© 2018 Elsevier Ltd A series of titanium complexes containing the permethylpentalene ligand (C8Me62−; Pn∗) – Pn∗Ti(O-2,6-Me-C6H3)Cl (1), Pn∗Ti(O-2,4-tBu-C6H3)Cl (2), Pn∗Ti(OtBu)Cl (3), Pn∗Ti(O-2,6-Me-C6H3)2 (4), Pn∗Ti(OtBu)2 (5) – or the (hydro)permethylpentalene ligand (C8Me6H−; Pn∗(H)) – Pn∗(H)Ti(O-2,6-Me-C6H3)Cl2 (6) and Pn∗(H)Ti(O-2,6-Me2-C6H3)3 (7) – were prepared by the reaction of [Pn∗TiCl(μ-Cl)]2 with the corresponding potassium salt or alcohol. All complexes have been characterized by single crystal X-ray diffraction studies and NMR spectroscopy. The (hydro)permethylpentalene complexes contain a stereocenter and planar chirality which can be described as R,RP or S,SP configurations.
Chadwick FM, McKay AI, Martinez-Martinez AJ, et al., 2017, Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates, CHEMICAL SCIENCE, Vol: 8, Pages: 6014-6029, ISSN: 2041-6520
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- Citations: 37
Chadwick FM, Kramer T, Gutmann T, et al., 2016, Selective C-H activation at a molecular rhodium sigma-alkane complex by solid/gas single-crystal to single-crystal H/D exchange, Journal of the American Chemical Society, Vol: 138, Pages: 13369-13378, ISSN: 0002-7863
The controlled catalytic functionalization of alkanes via the activation of C–H bonds is a significant challenge. Although C–H activation by transition metal catalysts is often suggested to operate via intermediate σ-alkane complexes, such transient species are difficult to observe due to their instability in solution. This instability may be controlled by use of solid/gas synthetic techniques that enable the isolation of single-crystals of well-defined σ-alkane complexes. Here we show that, using this unique platform, selective alkane C–H activation occurs, as probed by H/D exchange using D2, and that five different isotopomers/isotopologues of the σ-alkane complex result, as characterized by single-crystal neutron diffraction studies for three examples. Low-energy fluxional processes associated with the σ-alkane ligand are identified using variable-temperature X-ray diffraction, solid-state NMR spectroscopy, and periodic DFT calculations. These observations connect σ-alkane complexes with their C–H activated products, and demonstrate that alkane-ligand mobility, and selective C–H activation, are possible when these processes occur in the constrained environment of the solid-state.
Chadwick FM, Olliff N, Weller AS, 2016, A convenient route to a norbornadiene adduct of iridium with chelating phosphines, [Ir(R2PCH2CH2PR2)(NBD)][BAr4F] and a comparison of reactivity with H-2 in solution and the solid state, JOURNAL OF ORGANOMETALLIC CHEMISTRY, Vol: 812, Pages: 268-271, ISSN: 0022-328X
Chadwick FM, Cooper RT, O'Hare D, 2016, Zirconium and Hafnium Permethylpentalene Compounds, ORGANOMETALLICS, Vol: 35, Pages: 2092-2100, ISSN: 0276-7333
Chadwick FM, Rees NH, Weller AS, et al., 2016, A Rhodium-Pentane Sigma-Alkane Complex: Characterization in the Solid State by Experimental and Computational Techniques, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 55, Pages: 3677-3681, ISSN: 1433-7851
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- Citations: 38
Grigoropoulos A, Whitehead GFS, Perret N, et al., 2016, Encapsulation of an organometallic cationic catalyst by direct exchange into an anionic MOF, Chemical Science, Vol: 7, Pages: 2037-2050, ISSN: 2041-6539
Metal–Organic Frameworks (MOFs) are porous crystalline materials that have emerged as promising hosts for the heterogenization of homogeneous organometallic catalysts, forming hybrid materials which combine the benefits of both classes of catalysts. Herein, we report the encapsulation of the organometallic cationic Lewis acidic catalyst [CpFe(CO)2(L)]+ ([Fp–L]+, Cp = η5-C5H5, L = weakly bound solvent) inside the pores of the anionic [Et4N]3[In3(BTC)4] MOF (H3BTC = benzenetricarboxylic acid) via a direct one-step cation exchange process. To conclusively validate this methodology, initially [Cp2Co]+ was used as an inert spatial probe to (i) test the stability of the selected host; (ii) monitor the stoichiometry of the cation exchange process and (iii) assess pore dimensions, spatial location of the cationic species and guest-accessible space by single crystal X-ray crystallography. Subsequently, the quasi-isosteric [Fp–L]+ was encapsulated inside the pores via partial cation exchange to form [(Fp–L)0.6(Et4N)2.4][In3(BTC)4]. The latter was rigorously characterized and benchmarked as a heterogeneous catalyst in a simple Diels–Alder reaction, thus verifying the integrity and reactivity of the encapsulated molecular catalyst. These results provide a platform for the development of heterogeneous catalysts with chemically and spatially well-defined catalytic sites by direct exchange of cationic catalysts into anionic MOFs.
Weller AS, Chadwick FM, McKay AI, 2016, Transition Metal Alkane-Sigma Complexes: Synthesis, Characterization, and Reactivity, Advances in Organometallic Chemistry, Pages: 223-276
Although transient and difficult to observe, well-defined σ-alkane complexes are now becoming established due to the developments in characterization techniques alongside synthetic methodologies that allow for their observation. Although the number of such complexes still remains relatively small compared to other σ-complexes, such as those with dihydrogen, their growing number and diversity promises much for the future in terms of the development of their fundamental structure and bonding and their role in selective C–H bond activation and functionalization. In this perspective review, the synthesis and characterization of σ-alkane complexes are presented, and the onward reactivity of relatively well-defined examples discussed, with the emphasis on recent results.
Adams GM, Chadwick FM, Pike SD, et al., 2015, A CH2Cl2 complex of a [Rh(pincer)]+ cation, Dalton Transactions, Vol: 44, Pages: 6340-6342, ISSN: 1477-9226
The CH2Cl2 complex [Rh(tBuPONOP)(κ1-ClCH2Cl)][BArF4] is reported, that also acts as a useful synthon for other complexes such as N2, CO and H2 adducts; while the analogous PNP complex undergoes C–Cl activation.
Chadwick FM, Ashley AE, Cooper RT, et al., 2015, Group 9 bimetallic carbonyl permethylpentalene complexes, DALTON TRANSACTIONS, Vol: 44, Pages: 20147-20153, ISSN: 1477-9226
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- Citations: 5
Cooper RT, Chadwick FM, Ashley AE, et al., 2015, Double CO<sub>2</sub> activation by 14-electron η<SUP>8</SUP>-permethylpentalene titanium dialkyl complexes, CHEMICAL COMMUNICATIONS, Vol: 51, Pages: 11856-11859, ISSN: 1359-7345
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- Citations: 11
Pike SD, Chadwick FM, Rees NH, et al., 2014, Solid-state synthesis and characterization of σ-Alkane complexes, [Rh(L2)(η2,η2-C7H12)][BArF4] (L2 = bidentate chelating phosphine), Journal of the American Chemical Society, Vol: 137, Pages: 820-833, ISSN: 0002-7863
The use of solid/gas and single-crystal to single-crystal synthetic routes is reported for the synthesis and characterization of a number of σ-alkane complexes: [Rh(R2P(CH2)nPR2)(η2,η2-C7H12)][BArF4]; R = Cy, n = 2; R = iPr, n = 2,3; Ar = 3,5-C6H3(CF3)2. These norbornane adducts are formed by simple hydrogenation of the corresponding norbornadiene precursor in the solid state. For R = Cy (n = 2), the resulting complex is remarkably stable (months at 298 K), allowing for full characterization using single-crystal X-ray diffraction. The solid-state structure shows no disorder, and the structural metrics can be accurately determined, while the 1H chemical shifts of the Rh···H–C motif can be determined using solid-state NMR spectroscopy. DFT calculations show that the bonding between the metal fragment and the alkane can be best characterized as a three-center, two-electron interaction, of which σCH → Rh donation is the major component. The other alkane complexes exhibit solid-state 31P NMR data consistent with their formation, but they are now much less persistent at 298 K and ultimately give the corresponding zwitterions in which [BArF4]− coordinates and NBA is lost. The solid-state structures, as determined by X-ray crystallography, for all these [BArF4]− adducts are reported. DFT calculations suggest that the molecular zwitterions within these structures are all significantly more stable than their corresponding σ-alkane cations, suggesting that the solid-state motif has a strong influence on their observed relative stabilities.
Chadwick FM, O'Hare DM, 2014, Half- and Mixed-Sandwich Uranium Permethylpentalene Compounds, ORGANOMETALLICS, Vol: 33, Pages: 3768-3774, ISSN: 0276-7333
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- Citations: 9
Chadwick FM, Cooper RT, Ashley AE, et al., 2014, Early Transition Metal Permethylpentalene Complexes for the Polymerization of Ethylene, ORGANOMETALLICS, Vol: 33, Pages: 3775-3785, ISSN: 0276-7333
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- Citations: 13
Cooper RT, Chadwick FM, Ashley AE, et al., 2013, Synthesis and Characterization of Group 4 Permethylpentalene Dichloride Complexes, ORGANOMETALLICS, Vol: 32, Pages: 2228-2233, ISSN: 0276-7333
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- Citations: 26
Binding SC, Zaher H, Chadwick FM, et al., 2012, Heterolytic activation of hydrogen using frustrated Lewis pairs containing tris(2,2′,2"-perfluorobiphenyl)borane, DALTON TRANSACTIONS, Vol: 41, Pages: 9061-9066, ISSN: 1477-9226
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- Citations: 27
Chadwick FM, Ashley A, Wildgoose G, et al., 2010, Bis(permethylpentalene)uranium., Dalton Trans., Vol: 39, Pages: 6789-6793, ISSN: 1477-9226
The reaction of Li2(C14H18)(TMEDA)x (C14H18 = permethylpentalene, Pn*) with UCl4 yields U(η8-C14H18)2, (UPn*2) an analog of CePn*2 and U{η8-C8H4(1,4-SiiPr3)2}2. The UPn*2 mol. is structurally characterized via a variety of techniques, its magnetism is probed in the soln. and solid phase and the redox properties were studied using cyclic voltammetry. UPn*2 is reducible and the reduced species reacted with N2 to form a stable complex. An analogous complex was not found under Ar. [on SciFinder(R)]
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