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8. Iron- and Cobalt-Catalyzed Synthesis of Carbene Phosphinidenes

Author

Pal, Kuntal, Hemming, Oliver B, Day, Benjamin M, Pugh, Thomas, Evans, David J, and Layfield, Richard

Subjects
010405 organic chemistry, QD, General Medicine, 010402 general chemistry, 01 natural sciences, 3. Good health, 0104 chemical sciences
Abstract

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3)2}2] (M=Fe, Co), N-heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)·PAr. The formation of (IMe4)·PMes (Mes=mesityl) is also catalysed by the phosphinidene-bridged complex [(IMe4)2Fe-(m-PMes)]2, which provides evidence for metal-catalysed phosphinidene \ud transfer.

Published
2015

12. Strong Exchange Coupling in a Trimetallic Radical-Bridged Cobalt(II)-Hexaazatrinaphthylene Complex

Author

Moilanen, Jani, Chilton, Nicholas F., Day, Benjamin M., Pugh, Thomas, and Layfield, Richard A.

Subjects
hexaazatrinaphthylene, kemia, kalium, koboltti
Abstract

Reducing hexaazatrinaphthylene (HAN) with potassium in the presence of 18-c-6 produces [{K(18-c-6)}HAN], which contains the S = 1/2 radical [HAN]C ¢ . The [HAN]C ¢ radical can be transferred to the cobalt(II) amide [Co{N- (SiMe3 )2 }2 ], forming [K(18-c-6)][(HAN){Co(N’’)2 }3 ]; magnetic measurements on this compound reveal an S = 4 spin system with strong cobalt–ligand antiferromagnetic exchange and J ¢290 cm¢1 (¢2 J formalism). In contrast, the CoII centres in the unreduced analogue [(HAN){Co(N’’)2}3] are weakly coupled (J ¢4.4 cm¢1 ). The finding that [HAN]C ¢ can be synthesized as a stable salt and transferred to cobalt introduces potential new routes to magnetic materials based on strongly coupled, triangular HAN building blocks. peerReviewed

Published
2016

13. A three-coordinate iron–silylene complex stabilized by ligand–ligand dispersion forces

Author

Hänninen, Mikko M., Pal, Kuntal, Day, Benjamin M., Pugh, Thomas, and Layfield, Richard A.

Subjects
heterocyclic silyene complexes, kompleksiyhdisteet, bonding
Abstract

The structural and bonding properties of a three-coordinate N-heterocyclic silyene (NHSi) complex of the iron(II) amide [Fe{N(SiMe3)2}2] are reported. Computational studies reveal that dispersion forces between the amido SiMe3 substituents and the isopropyl substituents on the NHSi ligand significantly enhance the stability of the complex, along with Fe-to-Si π-backbonding. peerReviewed

Published
2016

16. Double Ligand Activation in Silyl-Substituted Rare-Earth Cyclobutadienyl Complexes

Author

Chakraborty, Anindita, Day, Benjamin M., Durrant, James P., He, Mian, Tang, Jinkui, and Layfield, Richard A.

Abstract

The sodium cyclobutadienyl (Cb) reagent [Na2{η4-C4(SiMe3)4}(THF)]2(2) reacts with rare-earth halides [MCl3(THF)x], where M = Y, Dy (x= 3.5) and Lu (x= 3), giving the sandwich coordination polymers [M{η3-C4(SiMe3)4H}{η4-C4(SiMe3)3-κ-(CH2SiMe2}Na]∞(3M, M = Y, Dy, Lu). The coordination environments of the rare-earth metals in 3Mfeature an η4-cyclobutadienyl ligand, with additional coordination by a tuck-in trimethylsilyl group and an η3-cyclobutenyl ligand. The ligand activation is thought to be a consequence of deprotonation of the Cb ligand by 2. The axial nature of the crystal field in 3Mis reflected in the single-molecule magnet properties of 3Dy, which has an anisotropy barrier of 309 cm–1in zero applied magnetic field.

Published
2020
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32. Iron- and Cobalt-Catalyzed Synthesis of Carbene Phosphinidenes.

Author

Pal, Kuntal, Hemming, Oliver B., Day, Benjamin M., Pugh, Thomas, Evans, David J., and Layfield, Richard A.

Subjects
CARBENE synthesis, PHOSPHINIDENES, IRON catalysts, COBALT catalysts, HETEROCYCLIC compounds, STOICHIOMETRY
Abstract

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3)2}2] (M=Fe, Co), N-heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)⋅PAr. The formation of (IMe4)⋅PMes (Mes=mesityl) is also catalyzed by the phosphinidene-bridged complex [(IMe4)2Fe(μ-PMes)]2, which provides evidence for metal-catalyzed phosphinidene transfer. [ABSTRACT FROM AUTHOR]

Published
2016
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40. Dominance of Cyclobutadienyl Over Cyclopentadienyl in the Crystal Field Splitting in Dysprosium Single-Molecule Magnets.

Author

Durrant JP, Day BM, Tang J, Mansikkamäki A, and Layfield RA

Abstract

Replacing a monoanionic cyclopentadienyl (Cp) ligand in dysprosium single-molecule magnets (SMMs) with a dianionic cyclobutadienyl (Cb) ligand in the sandwich complexes [(η 4 -Cb'''')Dy(η 5 -C 5 Me 4 t Bu)(BH 4 )] - (1), [(η 4 -Cb'''')Dy(η 8 -Pn † )K(THF)] (2) and [(η 4 -Cb'''')Dy(η 8 -Pn † )] - (3) leads to larger energy barriers to magnetization reversal (Cb''''=C 4 (SiMe 3 ) 4 , Pn † =1,4-di(tri-isopropylsilyl)pentalenyl). Short distances to the Cb'''' ligands and longer distances to the Cp ligands in 1-3 are consistent with the crystal field splitting being dominated by the former. Theoretical analysis shows that the magnetic axes in the ground Kramers doublets of 1-3 are oriented towards the Cb'''' ligands. The theoretical axiality parameter and the relative axiality parameter Z and Z rel are introduced to facilitate comparisons of the SMM performance of 1-3 with a benchmark SMM. Increases in Z and Z rel when Cb''' replaces Cp signposts a route to SMMs with properties that could surpass leading systems., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Published
2022
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42. Rare-Earth Cyclobutadienyl Sandwich Complexes: Synthesis, Structure and Dynamic Magnetic Properties.

Author

Day BM, Guo FS, Giblin SR, Sekiguchi A, Mansikkamäki A, and Layfield RA

Abstract

The potassium cyclobutadienyl [K 2 {η 4 -C 4 (SiMe 3 ) 4 }] (1) reacts with MCl 3 (THF) 3.5 (M=Y, Dy) to give the first rare-earth cyclobutadienyl complexes, that is, the complex anions [M{η 4 -C 4 (SiMe 3 ) 4 }{η 4 -C 4 (SiMe 3 ) 3 -κ-(CH 2 SiMe 2 }] 2- , (2 M ), as their dipotassium salts. The tuck-in alkyl ligand in 2 M is thought to form through deprotonation of the "squarocene" complexes [M{η 4 -C 4 (SiMe 3 ) 4 } 2 ] - by 1. Complex 2 Dy is a single-molecule magnet, but with prominent quantum tunneling. An anisotropy barrier of 323(22) cm -1 was determined for 2 Dy in an applied field of 1 kOe, and magnetic hysteresis loops were observed up to 7 K., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2018
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43. A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial Limit.

Author

Guo FS, Day BM, Chen YC, Tong ML, Mansikkamäki A, and Layfield RA

Abstract

Abstraction of a chloride ligand from the dysprosium metallocene [(Cp ttt ) 2 DyCl] (1 Dy Cp ttt =1,2,4-tri(tert-butyl)cyclopentadienide) by the triethylsilylium cation produces the first base-free rare-earth metallocenium cation [(Cp ttt ) 2 Dy] + (2 Dy ) as a salt of the non-coordinating [B(C 6 F 5 ) 4 ] - anion. Magnetic measurements reveal that [2 Dy ][B(C 6 F 5 ) 4 ] is an SMM with a record anisotropy barrier up to 1277 cm -1 (1837 K) in zero field and a record magnetic blocking temperature of 60 K, including hysteresis with coercivity. The exceptional magnetic axiality of 2 Dy is further highlighted by computational studies, which reveal this system to be the first lanthanide SMM in which all low-lying Kramers doublets correspond to a well-defined M J value, with no significant mixing even in the higher doublets., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2017
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44. Iron- and Cobalt-Catalyzed Synthesis of Carbene Phosphinidenes.

Author

Pal K, Hemming OB, Day BM, Pugh T, Evans DJ, and Layfield RA

Abstract

In the presence of stoichiometric or catalytic amounts of [M{N(SiMe3 )2 }2 ] (M=Fe, Co), N-heterocyclic carbenes (NHCs) react with primary phosphines to give a series of carbene phosphinidenes of the type (NHC)⋅PAr. The formation of (IMe4 )⋅PMes (Mes=mesityl) is also catalyzed by the phosphinidene-bridged complex [(IMe4 )2 Fe(μ-PMes)]2 , which provides evidence for metal-catalyzed phosphinidene transfer., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2016
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