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The potassium silole K 2 [SiC 4 -2,5-(SiMe 3 ) 2 -3,4-Ph 2 ] reacts with [M(η 8 -COT)(THF) 4 ][BPh 4 ] (M=Er, Y; COT=cyclo-octatetraenyl) in THF to give products that feature unprecedented insertion of the nucleophilic silicon centre into a carbon-oxygen bond of THF. The structure of the major product, [(μ-η 8  : η 8 -COT)M(μ-L 1 )K] ∞ (1 M ), consists of polymeric chains of sandwich complexes, where the spiro-bicyclic silapyran ligand [C 4 H 8 OSiC 4 (SiMe 3 ) 2 Ph 2 ] 2- (L 1 ) coordinates to potassium via the oxygen. The minor product [(μ-η 8  : η 8 -COT)M(μ-L 1 )K(THF)] 2 (2 M ) features coordination of the silapyran to the rare-earth metal. In forming 1 M and 2 M , silole insertion into THF only occurs in the presence of potassium and the rare-earth metal, highlighting the importance of bimetallic synergy. The lower nucleophilicity of germanium(II) leads to contrasting reactivity of the potassium germole K 2 [GeC 4 -2,5-(SiMe 3 ) 2 -3,4-Me 2 ] towards [M(η 8 -COT)(THF) 4 ][BPh 4 ], with intact transfer of the germole occurring to give the coordination polymers [{η 5 -GeC 4 (SiMe 3 ) 2 Me 2 }M(η 8 -COT)K] ∞ (3 M ). Despite the differences in reactivity induced by the group 14 heteroatom, the single-molecule magnet properties of 1 Er , 2 Er and 3 Er are similar, with thermally activated relaxation occurring via the first-excited Kramers doublet, subject to effective energy barriers of 122, 80 and 91 cm -1 , respectively. Compound 1 Er is also analysed by high-frequency dynamic magnetic susceptibility measurements up to 10 6  Hz., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The first germole-ligated single-molecule magnets are reported, with contrasting properties found for the near-linear sandwich complexes [(η 8 -COT)Ln(η 5 -Cp Ge ] - , where Ln=Dy (1 Dy ) or Er (1 Er ), COT is cyclo-octatetraenyl and Cp Ge is [GeC 4 -2,5-(SiMe 3 ) 2 -3,4-Me 2 ] 2- . Whereas 1 Er has an energy barrier of 120(1) cm -1 in zero applied field and open hysteresis loops up to 10 K, the relaxation in 1 Dy is characterized by quantum tunneling within the ground state., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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.)

Addition of the bipyridyl-embedded cycloparaphenylene nanohoop bipy[9]CPP to [Fe{H 2 B(pyz) 2 }] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP){H 2 B(pyz) 2 } 2 ] (1). The molecular structure of 1 shows that the nanohoop ligand contains a non-planar bipy unit. Magnetic susceptibility measurements indicate spin-crossover (SCO) behaviour with a T 1/2 of 130 K, lower than that of 160 K observed with the related compound [Fe(bipy){H 2 B(pyz) 2 } 2 ] (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop., (© 2020 Wiley-VCH GmbH.)

Reduction of the uranium(III) metallocene [(η 5 -C 5 i Pr 5 ) 2 UI] (1) with potassium graphite produces the "second-generation" uranocene [(η 5 -C 5 i Pr 5 ) 2 U] (2), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground-state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f 3 6d 1 . Appreciable covalent contributions to the metal-ligand bonds were determined from a computational study of 2, including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s-6d z 2 mixing., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Abstraction of iodide from [(η 5 -C 5 i Pr 5 ) 2 UI] (1) produced the cationic uranium(III) metallocene [(η 5 -C 5 i Pr 5 ) 2 U] + (2) as a salt of [B(C 6 F 5 ) 4 ] - . The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82° at uranium. Analysis of the bonding in 2 showed that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, thus leading to non-negligible covalent contributions to the bonding. Investigation of the dynamic magnetic properties of 2 revealed that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation by a Raman process., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

The Suzuki-Miyaura (SM) reaction is one of the most important methods for C-C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr 2 , in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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.)

The single-molecule magnet (SMM) properties of the isocarbonyl-ligated dysprosium metallocene [Cp*2 Dy{μ-(OC)2 FeCp}]2 (1Dy ), which contains a rhombus-shaped Dy2 Fe2 core, are described. Combining a strong axial [Cp*](-) ligand field with a weak equatorial field consisting of the isocarbonyl ligands leads to an anisotropy barrier of 662 cm(-1) in zero applied field. The dominant thermal relaxation pathways in 1Dy involves at least the fourth-excited Kramers doublet, thus demonstrating that prominent SMM behavior can be observed for dysprosium in low-symmetry environments., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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](.-) . The [HAN](.-) 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 Co(II) centres in the unreduced analogue [(HAN){Co(N'')2 }3 ] are weakly coupled (J≈-4.4 cm(-1) ). The finding that [HAN](.-) 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., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

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.)

Deprotonation of the yttrium-arsine complex [Cp'3Y{As(H)2Mes}] (1) (Cp'=η(5)-C5H4Me, Mes=mesityl) by nBuLi produces the μ-arsenide complex [{Cp'2Y[μ-As(H)Mes]}3] (2). Deprotonation of the As-H bonds in 2 by nBuLi produces [Li(thf)4]2[{Cp'2Y(μ3-AsMes)}3Li], [Li(thf)4]2[3], in which the dianion 3 contains the first example of an arsinidene ligand in rare-earth metal chemistry. The molecular structures of the arsine, arsenide, and arsinidene complexes are described, and the yttrium-arsenic bonding is analyzed by density functional theory., (© 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)

The sulfur-bridged dimers [{Cp'(2)Ln(μ-SSiPh(3))}(2)] (Ln=Gd (1), Dy (2); Cp'=η(5)-C(5)H(4)Me) were synthesized by the transmetalation reactions between [Cp'(3)Ln] and Ph(3)SiSLi. Compound 2 is a single-molecule magnet with slow relaxation of magnetization up to 40 K and an anisotropy barrier of U(eff) =133 cm(-1). Insight into the SMM properties of 2 and closely related SMMs has been obtained using ab initio calculations., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Organometallic single-molecule magnet: Studies of two dimeric organometallic dysprosium compounds reveal one to be the first organometallic single-molecule magnet (see picture). A comparison of the magnetic properties and electronic structures of the two compounds shows that Dy⋅⋅⋅Dy interactions have a profound influence on the dynamic magnetic behaviour, while having little effect on the static magnetic measurements., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The ion-contact complexes [{(eta(5)-Cp)(2)Mn(eta(2):eta(5)-Cp)K}(3)]x0.5 THF (1x0.5 THF) and [{(eta(2)-Cp)(2)(eta(2);eta(5)-MeCp)MnK(thf)}]x2 THF (2x2 THF) and ion-separated complexes [Mg(thf)(6)][(eta(2)-Cp)(3)Mn](2) (3), [Mg(thf)(6)][(eta(2)-Cp)(eta(2)-MeCp)(2)Mn)](2)x0.5 THF (4x0.5 THF), [Mg(thf)(6)][(eta(2)-MeCp)(3)Mn)](2)x0.5 THF (5x0.5 THF) and [Li([12]crown-4)](5)[(eta-Cp)(3)Mn](5) (6) (Cp=C(5)H(5), CpMe=C(5)H(4)CH(3)), have been prepared and structurally characterised. The effects of varying the Cp and CpMe ligands in complexes 1-5 have been probed by variable-temperature magnetic susceptibility measurements and EPR spectroscopic studies.