Publications
166 results found
Parr JM, White AJP, Crimmin MR, 2023, Calcium-stabilised transition metal bis(formyl) complexes: structure and bonding., Chem Commun (Camb), Vol: 59, Pages: 9840-9843
Reaction of a molecular calcium hydride with a series of group 9 dicarbonyl complexes [M(η5-C5Me5)(CO)2] (M = Co, Rh, Ir) led to the formation of both mono(formyl) and bis(formyl) complexes. The bis(formyl) complexes are unique. They have been characterised by multinuclear NMR spectroscopy and examples have been crystallographically characterised for the first time.
Zhang L, Kaukver S, McMullen J, et al., 2023, Catalytic C-H Alumination of Thiophenes: DFT Predictions and Experimental Verification, Organometallics, Vol: 42, Pages: 1711-1716, ISSN: 0276-7333
A computational model for the palladium-catalyzed C-H functionalization of thiophenes with aluminum hydride reagents has been developed. This model predicts that metalation should occur exclusively at the 2-position of the heterocycle. While related 2-metalated furans are known to undergo a ring-expansion reaction, further calculations suggest that the thiophene-derived organoaluminum compounds should be both kinetically and thermodynamically stable with respect to ring opening. This model is supported by experimental data. Selective C-H alumination of thiophene, 2-methylthiophene, 2-methoxythiophene, and benzothiophene was achieved using [Pd(PCy3)2] as a catalyst with loadings as low as 0.02 mol %. Even under extremely forcing conditions (200 °C) there was no evidence for a ring-opening event. The differences in selectivity between furan and thiophene systems are rationalized in terms of the stabilization of a key intermediate (and transition state) in the pathway for furan ring opening by a strong dative O→Al interaction.
Sheldon DJ, Parr JM, Crimmin MR, 2023, Room Temperature Defluorination of Poly(tetrafluoroethylene) by a Magnesium Reagent., J Am Chem Soc, Vol: 145, Pages: 10486-10490
Perfluoroalkyl substances (PFAS) are pervasive in the environment. The largest single use material within the PFAS compound class is poly(tetrafluoroethylene) (PTFE), a robust and chemically resistant polymer. Despite their widespread use and serious concerns about their role as pollutants, methods for repurposing PFAS are rare. Here we show that a nucleophilic magnesium reagent reacts with PTFE at room temperature, generating a molecular magnesium fluoride which is easily separated from the surface-modified polymer. The fluoride in turn can be used to transfer the fluorine atoms to a small array of compounds. This proof-of-concept study demonstrates that the atomic fluorine content of PTFE can be harvested and reused in chemical synthesis.
Parr JM, Crimmin MR, 2023, Carbon-Carbon Bond Formation from Carbon Monoxide and Hydride: The Role of Metal Formyl Intermediates., Angew Chem Int Ed Engl, Vol: 62
Current examples of carbon chain production from metal formyl intermediates with homogeneous metal complexes are described in this Minireview. Mechanistic aspects of these reactions as well as the challenges and opportunities in using this understanding to develop new reactions of CO and H2 are also discussed.
Parr JM, Crimmin MR, 2023, Carbon‐Carbon Bond Formation from Carbon Monoxide and Hydride: The Role of Metal Formyl Intermediates**, Angewandte Chemie, Vol: 135, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Current examples of carbon chain production from metal formyl intermediates with homogeneous metal complexes are described in this Minireview. Mechanistic aspects of these reactions as well as the challenges and opportunities in using this understanding to develop new reactions of CO and H<jats:sub>2</jats:sub> are also discussed.</jats:p>
Stadler B, Gorgas N, White AJP, et al., 2023, Double Deprotonation of CH<sub>3</sub>CN by an Iron‐Aluminium Complex**, Angewandte Chemie, Vol: 135, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Herein we present the first double deprotonation of acetonitrile (CH<jats:sub>3</jats:sub>CN) using two equivalents of a bimetallic iron‐aluminium complex. The products of this reaction contain an exceeding simple yet rare [CHCN]<jats:sup>2−</jats:sup> dianion moiety that bridges two metal fragments. DFT calculations suggest that the bonding to the metal centres occurs through heavily polarised covalent interactions. Mechanistic studies reveal the intermediacy of a monomeric [CH<jats:sub>2</jats:sub>CN]<jats:sup>−</jats:sup> complex, which has been characterised in situ. Our findings provide an important example in which a bimetallic metal complex achieves a new type of reactivity not previously encountered with monometallic counterparts.<jats:sup>[1, 2]</jats:sup> The isolation of a [CHCN]<jats:sup>2−</jats:sup> dianion through simple deprotonation of CH<jats:sub>3</jats:sub>CN also offers the possibility of establishing a broader chemistry of this motif.</jats:p>
Baker GJ, White AJP, Casely IJ, et al., 2023, Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc-Anilide Complex, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, ISSN: 0002-7863
Stadler B, Gorgas N, White AJP, et al., 2023, Double Deprotonation of CH3CN by an Iron-Aluminium Complex, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ISSN: 1433-7851
Mies T, Schürmann C, Ito S, et al., 2023, Front Cover: Synthesis and Characterization of a Calcium‐Pyrazolonato Complex. Observation of <i>In‐Situ</i> Desolvation During Micro‐Electron Diffraction (Z. Anorg. Allg. Chem. 5/2023), Zeitschrift für anorganische und allgemeine Chemie, Vol: 649, ISSN: 0044-2313
Parr JMM, Phanopoulos A, Vickneswaran A, et al., 2023, Understanding the role of ring strain in beta-alkyl migration at Mg and Zn centres, CHEMICAL SCIENCE, ISSN: 2041-6520
Garçon M, Phanopoulos A, White AJP, et al., 2023, Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes**, Angewandte Chemie, Vol: 135, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Reaction of a hexagonal planar palladium complex featuring a [PdMg<jats:sub>3</jats:sub>H<jats:sub>3</jats:sub>] core with H<jats:sub>2</jats:sub> is reversible and leads to the formation of a new [PdMg<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>] tetrahydride species alongside an equivalent of a magnesium hydride co‐product [MgH]. While the reversibility of this process prevented isolation of [PdMg<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>], analogous [PtMg<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>] and [PtZn<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>] complexes could be isolated and characterised through independent syntheses. Computational analysis (DFT, AIM, NCIPlot) of the bonding in a series of heterometallic tetrahydride compounds (Ni–Pt; Mg and Zn) suggests that these complexes are best described as square planar with marginal metal‐metal interactions; the strength of which increases slightly as group 10 is descended and increases from Mg to Zn. DFT calculations support a mechanism for H<jats:sub>2</jats:sub> activation involving a ligand‐assisted oxidative addition to Pd. These findings were exploited to develop a catalytic protocol for H/D exchange into magnesium hydride and zinc hydride bonds.</jats:p>
Garcon M, Phanopoulos A, White AJP, et al., 2022, Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ISSN: 1433-7851
Garçon M, Phanopoulos A, Sackman GA, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries**, Angewandte Chemie, Vol: 134, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>New heterometallic hydride complexes that involve the addition of {Mg−H} and {Zn−H} bonds to group 10 transition metals (Pd, Pt) are reported. The side‐on coordination of a single {Mg−H} to Pd forms a well‐defined σ‐complex. In contrast, addition of three {Mg−H} or {Zn−H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X‐ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.</jats:p>
Mies T, Schurmann C, Ito S, et al., 2022, Synthesis and Characterization of a Calcium-Pyrazolonato Complex. Observation of In-Situ Desolvation During Micro-Electron Diffraction, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, ISSN: 0044-2313
Garcon M, Phanopoulos A, Sackman GA, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 61, ISSN: 1433-7851
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- Citations: 1
Gorgas N, White AJP, Crimmin MR, 2022, Diverse reactivity of an iron-aluminium complex with substituted pyridines, CHEMICAL COMMUNICATIONS, Vol: 58, Pages: 10849-10852, ISSN: 1359-7345
Garçon M, Phanopoulos A, White A, et al., 2022, Reversible Dihydrogen Activation and Catalytic H/D Exchange with Group 10 Heterometallic Complexes
<jats:p>Reaction of a hexagonal planar palladium complex with a [PdMg3H3] core with H2 is reversible and leads to the formation of a new [PdMg2H4] tetrahydride species alongside an equivalent of a magnesium hydride co-product [MgH]. While the reversibility of this process prevented isolation and structural characterisation of [PdMg2H4], analogous [PtMg2H4] and [PdZn2H4] complexes could be isolated and characterised through independent syntheses. Computational analysis (DFT, AIM, NCIPlot) of the bonding in a series of heterometallic tetrahydride compounds (Ni-Pt; Mg and Zn) suggests that these complexes are best described as square planar with marginal metal–metal interactions; the strength of which increases as group 10 is descended and increases from Mg to Zn. DFT calculations support a mechanism for H2 activation involving a ligand-assisted oxidative addition to Pd. These findings were exploited to develop a catalytic protocol for H/D exchange into magnesium hydride and zinc hydride bonds.</jats:p>
Gorgas N, White A, Crimmin M, 2022, Diverse Reactivity of an Iron–Aluminium Complex with Substituted Pyridines
<jats:p>The reaction of an Fe–Al complex with an array of substituted pyridines is reported. Depending on the substitution pattern of the substrate site-selective sp2 or sp3 C–H bond activation is observed. A series of reaction products are observed based on (i) C–Al bond formation, (ii) C–C bond formation by nucleophilic addition or (iii) deprotonation of the β-diketiminate ligand. A divergent set of mechanisms involving a common intermediate is proposed.</jats:p>
Rekhroukh F, Zhang L, Kong RY, et al., 2022, Stereoselective insertion of cyclopropenes into Mg-Mg bonds, CHEMICAL COMMUNICATIONS, Vol: 58, Pages: 8282-8285, ISSN: 1359-7345
Baker G, White A, Casely I, et al., 2022, Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex
<jats:p>The reversible activation of dihydrogen with a molecular zinc anilide complex is reported. The mechanism of this reaction has been probed through stoichiometric experiments and DFT calculations. The combined evidence suggests that H2 activation occurs by addition across the Zn–N bond via a four-membered transition state in which the Zn and N atoms play a dual role of Lewis acid and Lewis base. The zinc hydride complex that results from H2 addition, has been shown to be remarkably effective for the hydrozincation of C=C bonds at modest temperatures. The scope of hy-drozincation includes alkynes, alkenes, and a 1,3-butadiyne. For alkynes, the hydrozincation step is stereospecific leading exclusively to the syn-isomer. Competition experiments show that the hydrozincation of alkynes is faster than the equivalent alkene substrates. These new discoveries have been used to develop an unprecedented catalytic sys-tem for the semi-hydrogenation of alkynes. The catalytic scope includes both aryl and alkyl substituted internal al-kynes and proceeds with high alkene : alkane (96 : 4) and Z : E ratios (>91 : 9). This work offers a first example of selective hydrogenation catalysis using zinc complexes.</jats:p>
Baker G, White A, Casely I, et al., 2022, Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex
<jats:p>The reversible activation of dihydrogen with a molecular zinc anilide complex is reported. The mechanism of this reaction has been probed through stoichiometric experiments and DFT calculations. The combined evidence suggests that H2 activation occurs by addition across the Zn–N bond via a four-membered transition state in which the Zn and N atoms play a dual role of Lewis acid and Lewis base. The zinc hydride complex that results from H2 addition, has been shown to be remarkably effective for the hydrozincation of C=C bonds at modest temperatures. The scope of hy-drozincation includes alkynes, alkenes, and a 1,3-butadiyne. For alkynes, the hydrozincation step is stereospecific leading exclusively to the syn-isomer. Competition experiments show that the hydrozincation of alkynes is faster than the equivalent alkene substrates. These new discoveries have been used to develop an unprecedented catalytic sys-tem for the semi-hydrogenation of alkynes. The catalytic scope includes both aryl and alkyl substituted internal al-kynes and proceeds with high alkene : alkane (>91 : 9) and Z : E ratios (>96 : 4). This work offers a first example of selective hydrogenation catalysis using zinc complexes.</jats:p>
Sheldon DJ, Crimmin MR, 2022, Repurposing of F-gases: challenges and opportunities in fluorine chemistry, CHEMICAL SOCIETY REVIEWS, Vol: 51, Pages: 4977-4995, ISSN: 0306-0012
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- Citations: 3
Rekhroukh F, Zhang L, Kong R, et al., 2022, Stereoselective Insertion of Cyclopropenes into Mg–Mg Bonds
<jats:p>The reaction of cyclopropenes with compounds containing Mg–Mg bonds is reported. 1,2-Dimagnesiation occurs exclusively by syn-addition to the least hindered face of the alkene forming a single diastereomeric product. DFT calculations support a concerted and stereoselective mechanism. These findings shed new light on the stereochemistry of reactions involving magnesium reagents.</jats:p>
Gorgas N, White AJP, Crimmin MR, 2022, Cooperative C-H Bond Activation by a Low-Spin d(6) Iron-Aluminum Complex, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 144, Pages: 8770-8777, ISSN: 0002-7863
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- Citations: 4
Parr JM, White AJP, Crimmin MR, 2022, Magnesium-stabilised transition metal formyl complexes: structures, bonding, and ethenediolate formation, CHEMICAL SCIENCE, Vol: 13, Pages: 6592-6598, ISSN: 2041-6520
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- Citations: 2
Garçon M, Phanopoulos A, Sackman G, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries
<jats:p>New heterometallic hydride complexes that involve the addition of {Mg–H} and {Zn–H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg–H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg–H} or {Zn–H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.</jats:p>
Garçon M, Phanopolous A, Sackman G, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries
<jats:p>New heterometallic hydride complexes that involve the addition of {Mg–H} and {Zn–H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg–H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg–H} or {Zn–H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.</jats:p>
Mulryan D, Rodwell J, Phillips NA, et al., 2022, Au(I) Catalyzed HF Transfer: Tandem Alkyne Hydrofluorination and Perfluoroarene Functionalization, ACS CATALYSIS, Vol: 12, Pages: 3411-3419, ISSN: 2155-5435
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- Citations: 1
Batuecas M, Kong RY, White AJP, et al., 2022, Functionalization and hydrogenation of carbon chains derived from CO, Angewandte Chemie International Edition, Vol: 61, ISSN: 1433-7851
Selective reactions that combine H 2 , CO and organic electrophiles (aldehyde, ketones, isocyanide) to form hydrogenated C 3 and C 4 carbon chains are reported. These reactions proceed by CO homologation mediated by [W(CO) 6 ] and an aluminum(I) reductant, followed by functionalization and hydrogenation of the chain ends. A combination of kinetics (rates, KIEs) and DFT calculations has been used to gain insight into a key step which involves hydrogenation of a metallocarbene intermediate. These findings expand the extremely small scope of systems that combine H 2 and CO to make well-defined products with complete control over chain length and functionality.
Gorgas N, White A, Crimmin M, 2022, Cooperative C–H Bond Activation by a Low-Spin d6 Iron–Aluminium Complex
<jats:p>The reactions of transition metal complexes underpin numerous synthetic processes and catalytic transformations. Typically, this reactivity involves the participation of empty and filled molecular orbitals centred on the transition metal. Kinetically stabilised species, such as octahedral low-spin d6 transition metal complexes, are not expected to participate directly in these reactions. However, novel approaches that exploit metal ligand-cooperativity offer an opportunity to challenge these preconceptions. Here we show that inclusion of an aluminium-based ligand into the coordination sphere of neutral low-spin d6 iron complex leads to unexpected reactivity. Complexes featuring an unsupported Fe–Al bond are capable of the intermolecular C–H bond activation of pyridines. Mechanistic analysis suggests that C–H activation proceeds through a reductive deprotonation in which the two metal centres (Fe and Al) act like a frustrated Lewis-pair. Key to this behaviour is a ground state destabilisation of the d6 iron complex, brought about by the inclusion of the electropositive aluminium-based ligand. These findings have immediate implications for the design of reagents and catalysts based on 1st row transition metals.</jats:p>
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