The heterotrinuclear linear arrangement Ln–Pd–Ln has short Ln–Pd distances: does it imply a covalent bond?

Complexes with short intermetallic distances between transition metal fragments and lanthanide (Ln) fragments are fascinating objects of study, owing to the ambiguity of the nature of the interaction. The addition of the divalent lanthanide fragments Cp*2Ln(OEt2) (Ln = Sm or Yb) to a redox-active, non-symmetrical ligand, 2-pyrimidin-2-yl-1H-benzimidazole (Hbimpm), leads to two isostructural complexes, of the general formula (Cp*2Ln)2[μ-Pd(pyridyl)2] (Ln = Sm (4) and Yb (5)). These adducts have interesting features, such as unique linear Ln-Pd-Ln arrangements and short Ln-Pd distances, which deviate from the expected lanthanide contraction. A mixed computational and spectroscopic study into the formation of these adducts gathers important clues as to their formation. At the same time, a thorough characterization of these complexes establishes the +3 oxidation state of all the involved Ln centers. Detailed theoretical computations demonstrate that the apparent deviation from the lanthanide contraction is not due to any difference in the intermetallic interaction between the Pd and the Ln, but that the fragments are joined together by electrostatic interactions and dispersive forces. This conclusion is in contrast with the findings about a third complex, Cp*2Yb(μ-Me)2PdCp* (6), formed during the reaction, which also possesses a short Yb-Pd distance. Studies at the CASSCF level of theory on this complex show several orbitals containing significant interactions between the 4f and 4d manifolds of the metals. This demonstrates the need for methodical and careful analyses in gauging the intermetallic interaction and the inadequacy of empirical metrics in describing such phenomena.

The use of stoechiometric SmI2 in combination with benzophenone and N-heterocyclic aromatics such as bipyridine, phenanthroline and pyridine allows the direct ortho-coupling of both partners in an atom economical reaction free of any other coupling additives. The transformation was investigated by 1H NMR, X-ray studies and theoretical calculations providing reaction intermediates and the reaction mechanism.

The dataset contains the raw data for the compound Cp*2Yb(taphen)PtMe2

This article relates the synthesis and characterization of novel heterobimetallic complexes containing a low-valent lanthanide, a tetradentate redox non-innocent ligand, viz. the 4,5,9,10-tetraazaphenanthrene, taphen ligand and transition metal fragments of PdMe2 and PtMe2. The experimental results are supported by a theoretical study. Investigation of their reduction properties allowed the formation of isostructural original heterotrimetallic complexes containing two Cp*2Yb fragments and the (taphen)MMe2 (M = Pd and Pt) motifs. These complexes are stable in non-coordinating solvent such as toluene but decompose in coordinating solvents such as thf. Investigation of the internal electron transfer shows that the taphen ligand behaves as a two-electrons reservoir but is capable of transferring back only one electron in thf. This reversible electron(s) transfer is rare in organolanthanide chemistry and show the potential interest of these complexes in reductive chemistry. Additionally, the trinuclear complexes feature odd X-ray crystal structures in which a deviation of symmetry is observed. The latter observation was studied in depth using quantum chemistry calculations highlighting the role of non-covalent weak interactions.

Divalent thulium complexes have great potential in reductive organic chemistry and for small-molecule transformations. Nonetheless, they are rare and hard to synthesize, thus their electronic structure is almost unexplored. In their Communication on page 4266 ff., G. Nocton et al. present a first step to the discovery of the submerged part of the iceberg, through unravelling the ground-state nature of divalent thulium triflate by means of luminescence, magnetism, and EPR spectroscopy.

AbstractThe first molecular TmII luminescence measurements are reported along with rare magnetic, X and Q bands EPR studies. Access to simple and soluble molecular divalent lanthanide complexes is highly sought for small‐molecule activation studies and organic transformations using single‐electron transfer processes. However, owing to their low stability and propensity to disproportionate, these complexes are hard to synthetize and their electronic properties are therefore almost unexplored. Herein we present the synthesis of [Tm(μ‐OTf)2(dme)2]n, a rare and simple coordination compound of divalent thulium that can be seen as a promising starting material for the synthesis of more elaborated complexes. This reactive complex was structurally characterized by X‐ray diffraction analysis and its electronic structure has been compared with that of its halide cousin TmI2(dme)3.

Divalent thulium complexes have great potential in reductive organic chemistry and for small-molecule transformations. Nonetheless, they are rare and hard to synthesize, thus their electronic structure is almost unexplored. In their Communication on page 4266 ff., G. Nocton et al. present a first step to the discovery of the submerged part of the iceberg, through unravelling the ground-state nature of divalent thulium triflate by means of luminescence, magnetism, and EPR spectroscopy.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Thulium(II)-Komplexe …… haben großes Potenzial in der reduktiven organischen Chemie und für Transformationen kleiner Moleküle. Sie sind jedoch selten und schwer zu synthetisieren, daher ist ihre elektronische Struktur nahezu unerforscht. G. Nocton et al. unternehmen in ihrer Zuschrift auf S. 4330 einen ersten Schritt hin zur Entdeckung des “verborgenen Teils des Eisbergs”, indem sie die Grundzustandseigenschaften von Thulium(II)-triflat durch Lumineszenz-, Magnetismus- und EPR-Messungen aufklären.

The equilibrium between the radical phenanthroline complex Cp*2 Sm(phen) and the coupling product (Cp*2 Sm(phen))2 has been investigated based on quantum chemistry calculations. Topological analyses pointed out that the C-C bond created has a partial covalent character, explaining why both the monomeric and the dimeric forms exist in equilibrium. A large variety of density functionals have been tested to reproduce experimental thermodynamic data for this equilibrium. Finally, the PBE0-D3 and M06-2X functionals lead to a good evaluation of the energies and enable a correct description of the ligand to metal charge transfer, both in the 4f and 5d metal orbitals.

The unique combination of a divalent organolanthanide fragment, Cp*2Yb, with bipyrimidine (bipym) and a palladium bis-alkyl fragment, PdMe2, allows the rapid formation and stabilization of a PdIV tris-alkyl moiety after oxidative addition with MeI. The crucial role of the organolanthanide fragment is demonstrated by the substitution of bipym by the 4,5,9,10-tetraazaphenanthrene ligand, which drastically modifies the electronic structure and tunes the stability of the PdIV species.

How to make sure an electron is really transferred to a tmbp ligand?

Transfert électronique dans des complexes de lanthanides : de la structure électronique à la réactivité Comprendre les réactions biologiques requiert l'utilisation de composés capables de transférer des électrons de manière sélective et de stabiliser des intermédiaires réactionnels. Ce travail s'est intéressé à la conception et à la réactivité de complexes de lanthanide divalents qui ont ce type de propriétés.Dans un premier temps, la réduction de deux molécules organiques, la phénanthroline et la benzophenone, a été étudiée. Les données thermodynamiques obtenues avec la phénanthroline ont permis de construire un ensemble de données de références de différentes fonctionnelles de la densité. Des méthodes de type TDDFT et CASSCF ont été ensuite mises en oeuvre afin de reproduire les spectres UV-visibles.Par la suite, les radicaux benzophenone et phénanthroline ont été utilisés afin de réaliser des réactions radicalaires. L'utilisation du radical tempo a permis de réaliser des réactions de réduction induite par les effets stériques des complexes. La compétition entre la benzophenone et la phénanthroline a également été étudiée et a permis de réaliser des couplages de type Minisci, qui sont inédits pour des complexes de lanthanides.Enfin, la réduction de composés organométalliques via un ligand N-hétérocyclique a été réalisée. Deux de ces composés ont été comparés vis à vis de la stabilisation de complexes de palladium au degré d'oxydation +IV. L'importance du ligand a été de plus étudiée grâce à des calculs CASSCF et DFT qui ont montré que certains types de ligands permettaient un transfert électronique plus direct jusqu'au palladium.