Stabilization of the Compressed Planar Benzene Dianion in Inverse-Sandwich Rare Earth Metal Complexes.

For the first time, the capture of the planar antiaromatic parent benzene dianion in between two trivalent rare earth (RE) metal cations (RE), each stabilized by two guanidinate ligands, is reported. The synthesized inverse-sandwich complexes [{(MeSi)NC(NPr)}RE](μ-η : η-CH), (RE=Y (1), Dy (2), and Er (3)) were crystallized from aprotic solvents and feature a remarkably planar parent benzene dianion, previously not encountered for any metal ion prone to low or absent covalency. The -2 charge localization at the benzene ligand was deduced from the results obtained by single-crystal X-ray diffraction analyses, spectroscopy, magnetometry, and Density Functional Theory (DFT) calculations.

Implementation of 2,2'-azobispyridine radical mono- and dianions in dinuclear rare earth metal complexes.

The seminal isolation of a dinuclear rare earth metal complex comprising a bridging 2,2'-azobispyridyl radical anion, [(CpY)(μ-abpy˙)](BPh), is presented, which was obtained from a one-electron chemical oxidation of [(CpY)(μ-abpy)]. The unprecedented compounds were characterized by crystallography, spectroscopy and DFT computations. The radical character was proven by EPR spectroscopy.

Construction of intermolecular σ-hole interactions in rare earth metallocene complexes using a 2,3,4,5-tetraiodopyrrolyl anion.

The generation of noncovalent intermolecular interactions represents a powerful method to control molecular vibrations and rotations. Combining these with the axial ligand field enforced by the metallocene ligand scaffold provides a dual-pronged approach in controlling the magnetic-relaxation pathways for dysprosium-based single-molecule magnets (SMMs). Here, we present the first implementation of 2,3,4,5-tetraiodopyrrole (TIPH) in its anionic form [TIP] as a ligand in three isostructural rare-earth metal complexes Cp*RE(TIP) (1-RE, RE = Y, Gd, and Dy; Cp* = pentamethylcylopentadienyl), where the TIP ligand binds through the nitrogen and one iodine atom κ(N,I) to the metal centre.

Introducing the Bis(mesitoyl)phosphide Ligand into Dinuclear Trivalent Rare Earth Metal Coordination Chemistry.

Anionic ancillary ligands play a critical role in the construction of rare earth (RE) metal complexes due to the large influence on the stability of the molecule and engendering emergent electronic properties that are of interest in a plethora of applications. Supporting ligands comprising oxygen donor atoms are highly pursued in RE chemistry owing to the high oxophilicity innate to these ions. The scarcely employed bis(acyl)phosphide (BAP) ligands feature oxygen coordination sites and contain a phosphide backbone rendering it attractive for RE-coordination chemistry.

Guanidinate Yttrium Complexes Containing Bipyridyl and Bis(benzimidazolyl) Radicals.

Ancillary ligand scaffolds that sufficiently stabilize a metal ion to allow its coordination to an open-shell ligand are scarce, yet their development is essential for next-generation spin-based materials with topical applications in quantum information science. To this end, a synthetic challenge must be met: devising molecules that enable the binding of a redox-active ligand through facile displacement and clean removal of a weakly coordinating anion. Here, we probe the accessibility of unprecedented radical-containing rare-earth guanidinate complexes by combining our recently discovered yttrium tetraphenylborate complex [{(MeSi)NC(NPr)}Y][(μ-η-Ph)(BPh)] with the redox-active ligands 2,2'-bipyridine (bpy) and 2,2'-bis(benzimidazole) (Bbim), respectively, under reductive conditions.

Pyrrolyl-Bridged Metallocene Complexes: From Synthesis, Electronic Structure, to Single-Molecule Magnetism.

The π- and σ-basicity of the pyrrolyl ligand affords several coordination modes. A sterically encumbering coordination sphere around metal centers may foster new coordination modes for the pyrrolyl ligand. Here, we present three dinuclear rare earth complexes [Cp*RE(μ-pyr)], [RE = Y (), La (), Dy (); Cp* = pentamethylcyclopentadienyl, pyr = pyrrolyl], which were synthesized through a protonolysis reaction between allyl complexes and H-pyrrole.

A rare isocyanide derived from an unprecedented neutral yttrium(ii) bis(amide) complex.

A room temperature stable complex formulated as Y(NHAr*) has been prepared, where Ar* = 2,6-(2,4,6-(Pr)CH)CH, by KC reduction of ClY(NHAr*). Based on EPR evidence, Y(NHAr*) is an example of a d Y(ii) complex with significant delocalization of the unpaired electron density from the metal to the ligand. The isolation of molecular divalent metal complexes is challenging for rare earth elements such as yttrium.

Heteroleptic Rare-Earth Tris(metallocenes) Containing a Dibenzocyclooctatetraene Dianion.

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)][CpRE(η-dbCOT)] (RE = Y (), Dy (); Cp = tetramethylcyclopentadienyl), through a salt metathesis reaction involving CpRE(BPh) 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) anion in a complex containing d- or f-block metals.