Thursday, January 20, 2022

Simple conversion of trisodium phosphide, Na3P, into silyl- and cyanophosphides and structure of a terminal silver phosphide - Dalton Transactions (RSC Publishing)

Simple conversion of trisodium phosphide, Na3P, into silyl- and cyanophosphides and structure of a terminal silver phosphide - Dalton Transactions (RSC Publishing)
Reaction of trisodium phosphide (Na3P) with chlorosilanes allows for simple derivatization into silyl- and cyano-substituted phosphanide species which were compared to each other. The recently discovered cyano(triphenylsilyl)phosphanide shows unique coordination properties compared to the bis(silyl)phosphides.

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes | Nature Chemistry

Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes | Nature Chemistry


Heteroleptic Rare-Earth Tris(metallocenes) Containing a Dibenzocyclooctatetraene Dianion | Inorganic Chemistry

Heteroleptic Rare-Earth Tris(metallocenes) Containing a Dibenzocyclooctatetraene Dianion | Inorganic Chemistry

Isolable heteroleptic tris(metallocenes) containing five-membered and larger rings remain extremely scarce. The utilization of tripositive rare-earth-metal ions with ionic radii >1 Å allowed access to unprecedented and sterically congested dibenzocyclooctatetraenyl (dbCOT) metallocenes, [K(crypt-222)][Cptet2RE(η2-dbCOT)] (RE = Y (1), Dy (2); Cptet = tetramethylcyclopentadienyl), through a salt metathesis reaction involving Cptet2RE(BPh4) and the potassium salt of the dbCOT dianion. The solid-state structures were investigated by single-crystal X-ray diffraction, magnetometry, and IR spectroscopy and provided evidence for the first crystallographically characterized (dbCOT)2– anion in a complex containing d- or f-block metals. Remarkably, the (Cptet) ligands force a distortion from planarity within the (dbCOT)2– moiety, engendering a rare η2-bonding motif, as opposed to the classical η8 conformation observed in complexes bearing a (COT)2– ion. The η2 coordination mode was proven crystallographically between 100 and 298 K and computationally (DFT and NBO). Furthermore, nucleus independent chemical shift (NICS) calculations uncovered significant ring current within the dbCOT ligand. The solution-state properties of 1 and 2 were analyzed via cyclic voltammetry, NMR, and UV–vis spectroscopy. Cyclic voltammograms of 1 and 2 exhibit a quasi-reversible feature indicating the accessibility of complexes with dbCOT in two oxidation states (dbCOT2–/3–•). Importantly, the dysprosium congener, 2, is a zero-field single-molecule magnet (SMM).

Mechanisms of Electrochemical N2 Splitting by a Molybdenum Pincer Complex | Inorganic Chemistry

Mechanisms of Electrochemical N2 Splitting by a Molybdenum Pincer Complex | Inorganic Chemistry

Molybdenum complexes supported by tridentate pincer ligands are exceptional catalysts for dinitrogen fixation using chemical reductants, but little is known about their prospects for electrochemical reduction of dinitrogen. The viability of electrochemical N2 binding and splitting by a molybdenum(III) pincer complex, (pyPNP)MoBr3 (pyPNP = 2,6-bis(tBu2PCH2)-C5H3N)), is established in this work, providing a foundation for a detailed mechanistic study of electrode-driven formation of the nitride complex (pyPNP)Mo(N)Br. Electrochemical kinetic analysis, optical and vibrational spectroelectrochemical monitoring, and computational studies point to two concurrent reaction pathways: In the reaction–diffusion layer near the electrode surface, the molybdenum(III) precursor is reduced by 2e and generates a bimetallic molybdenum(I) Mo2(μ-N2) species capable of N–N bond scission; and in the bulk solution away from the electrode surface, over-reduced molybdenum(0) species undergo chemical redox reactions via comproportionation to generate the same bimetallic molybdenum(I) species capable of N2 cleavage. The comproportionation reactions reveal the surprising intermediacy of dimolybdenum(0) complex trans,trans-[(pyPNP)Mo(N2)2](μ-N2) in N2 splitting pathways. The same “over-reduced” molybdenum(0) species was also found to cleave N2 upon addition of lutidinium, an acid frequently used in catalytic reduction of dinitrogen.

Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes | Journal of the American Chemical Society

Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes | Journal of the American Chemical Society

Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. Similar fields can be generated in molecular systems using charged functionalities. Manganese(V) salen nitrido complexes (salen = N,N′-ethylenebis(salicylideneaminato)) appended with a crown ether unit containing Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to determine the effect of charge on pKaE1/2, and the net bond dissociation free energy (BDFE) of N–H bonds. The series, which includes the manganese(V) salen nitrido without an appended crown, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were used with the Mn(VI/V) reduction potentials to calculate the N–H BDFEs of the imidos in acetonitrile. Despite a span of >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans ∼6 kcal/mol (between 73 and 79 kcal/mol). These results suggest that the incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa values while minimally affecting the BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer pathways.

Monday, January 17, 2022

Nitrogen Atom Transfer Catalysis by Metallonitrene C−H Insertion: Photocatalytic Amidation of Aldehydes - Schmidt‐Räntsch - - Angewandte Chemie International Edition - Wiley Online Library

Nitrogen Atom Transfer Catalysis by Metallonitrene C−H Insertion: Photocatalytic Amidation of Aldehydes - Schmidt‐Räntsch - - Angewandte Chemie International Edition - Wiley Online Library
Nitrogen Atom Transfer Catalysis by Metallonitrene C−H Insertion: Photocatalytic Amidation of Aldehydes

Photocatalytic nitrogen atom transfer into aldehyde C−H bonds is reported. A palladium(II) metallonitrene species with nitrogen-centered biradical character was identified as the key intermediate and was photocrystallographically, magnetically and computationally characterized. The nucleophilic metallonitrene C−H insertion step results in inverted selectivity for the net nitrene transfer catalysis.

Tris(tetramethylguanidinyl)phosphine: The Simplest Non‐ionic Phosphorus Superbase and Strongly Donating Phosphine Ligand - Buß - 2022 - Chemistry – A European Journal - Wiley Online Library

Tris(tetramethylguanidinyl)phosphine: The Simplest Non‐ionic Phosphorus Superbase and Strongly Donating Phosphine Ligand - Buß - 2022 - Chemistry – A European Journal - Wiley Online Library
Dr. Florenz Buß, Maike B. Röthel, Janina A. Werra, Philipp Rotering, Dr. Lukas F. B. Wilm, Dr. Constantin G. Daniliuc, Pawel Löwe, Prof. Dr. Fabian Dielmann

e202104021 | First Published:18 November 2021

The crystalline phosphorus superbase tris(1,1,3,3-tetramethylguanidinyl)phosphine is accessible through an easy and scalable procedure starting from cheap and commercially available bulk chemicals. The properties of the strongly electron-donating phosphine in coordination chemistry and the reactivity with small molecules (CO2, SO2, N2O and elemental chalcogens) were studied.

A Phosphorus‐Based Pacman Dication Generated by Cooperative Self‐Activation of a Pacman Phosphane - Eickhoff - 2022 - Chemistry – A European Journal - Wiley Online Library

A Phosphorus‐Based Pacman Dication Generated by Cooperative Self‐Activation of a Pacman Phosphane - Eickhoff - 2022 - Chemistry – A European Journal - Wiley Online Library


An NHC‐Stabilized H2GeBH2 Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains - Ackermann - 2022 - Chemistry – A European Journal - Wiley Online Library

An NHC‐Stabilized H2GeBH2 Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains - Ackermann - 2022 - Chemistry – A European Journal - Wiley Online Library
Matthias T. Ackermann, Dr. Michael Seidl, Fuwei Wen, Dr. Michael J. Ferguson, Prof. Alexey Y. Timoshkin, Prof. Eric Rivard, Prof. Dr. Manfred Scheer

e202103780 | First Published:11 November 2021

The NHC-stabilized compound IDipp  GeH2BH2OTf was synthesized. Reactivity studies on this novel building block with different phosphines and AsPh3 showed its potential to serve as an ideal precursor for unprecedented cationic group 13/14/15 chain compounds. In addition, a reaction with PH3 leads to the formation of the parent hydrides [IDipp  GeH2BH2PH3][OTf] and [IDipp  GeH3][OTf].

Friday, January 14, 2022

Ultrahard magnetism from mixed-valence dilanthanide complexes with metal-metal bonding

Ultrahard magnetism from mixed-valence dilanthanide complexes with metal-metal bonding
Metal-metal bonding interactions can engender outstanding magnetic properties in bulk materials and molecules, and examples abound for the transition metals. Extending this paradigm to the lanthanides, herein we report mixed-valence dilanthanide complexes (CpiPr5)2Ln2I3 (Ln is Gd, Tb, or Dy; CpiPr5, pentaisopropylcyclopentadienyl), which feature a singly occupied lanthanide-lanthanide σ-bonding orbital of 5dz2 parentage, as determined by structural, spectroscopic, and computational analyses. Valence delocalization, wherein the d electron is equally shared by the two lanthanide centers, imparts strong parallel alignment of the σ-bonding and f electrons on both lanthanides according to Hund’s rules. The combination of a well-isolated high-spin ground state and large magnetic anisotropy in (CpiPr5)2Dy2I3 gives rise to an enormous coercive magnetic field with a lower bound of 14 tesla at temperatures as high as 60 kelvin.

Deciphering the Role of Symmetry and Ligand Field in Designing Three-Coordinate Uranium and Plutonium Single-Molecule Magnets | Inorganic Chemistry

Deciphering the Role of Symmetry and Ligand Field in Designing Three-Coordinate Uranium and Plutonium Single-Molecule Magnets | Inorganic Chemistry
Abstract Image

Actinide single-molecule magnets (SMMs) have gained paramount interest in molecular magnetism as they offer a larger barrier height of magnetization (Ueff) reversal compared to the lanthanide analogue, thanks to their greater metal–ligand covalency. However, the reported actinide SMMs to date yield a relatively smaller Ueff as there is no established design principle to enhance Ueff values. To address this issue, we have employed ab initio CASSCF/CASPT2/NEVPT2 calculations to study a series of three-coordinate U3+ and Pu3+ SMMs. To begin with, we have studied two experimentally characterized U3+ ion-field-induced SMMs, namely, planar [U{N(SiMe2tBu)2}3] (1) and pyramidal [U{N(SiMe3)2}3] (2) complexes reported earlier. Both the complexes were found to stabilize mJ = |±1/2⟩ as the ground state with a very strong quantum tunneling of magnetization (QTM), rendering them unsuitable for SMMs. Our calculations reveal that in the pyramidal geometry (such as in 2), the energy of the 5f26d1 state is lowered compared to the planar geometry (as in 1), resulting in a slightly better SMM characteristic in the former. To unravel the effect of symmetry in magnetic properties, ab initio calculations were performed on two reported T-shaped complexes [U(NSiiPr2)2(I)] (3) and [U(NHAriPr6)2I] (4, AriPr6 = 2,6-(2,4,6-iPr3C6H2)2C6H3). Quite interestingly, mJ = |±9/2⟩ is found to be the ground state for both the complexes with a blocking barrier exceeding 900 cm–1. Furthermore, to decipher the effect of the transuranic element in magnetic anisotropy, ab initio calculations were extended to the Pu analogue of 2, [Pu{N(SiMe3)2}3] (5), which yields a record-breaking blocking barrier of ∼1933 cm–1. Among the three-coordinate geometries studied, the pyramidal geometry was found to offer substantial magnetic anisotropy for Pu3+ ions, while a T-shaped geometry is best suited for U3+ ions. While the chosen theoretical protocols’ overestimation of barrier height cannot be avoided, these values are still several orders of magnitude larger than the Ueff values reported for any actinide SMMs and unveil a design principle for superior three-coordinate actinide-based SMMs.

Simple conversion of trisodium phosphide, Na3P, into silyl- and cyanophosphides and structure of a terminal silver phosphide - Dalton Transactions (RSC Publishing)

Simple conversion of trisodium phosphide, Na3P, into silyl- and cyanophosphides and structure of a terminal silver phosphide - Dalton Transa...