Stretching the P-C Bond. Variations on Carbenes and Phosphanes

Lanthanide Phosphonates and Phosphates in Molecular Magnetism

Phosphonate and phosphate ligands have historically received less attention when compared to the widely prevalent carboxylate ligand system. Phosphonates possess multiple donating sites, often leading to the formation of larger aggregates with limited solubility. Conversely, the P-O bond within phosphates is highly susceptible to hydrolysis, resulting in the precipitation of insoluble compounds, particularly when interacting with lanthanide metal ions. However, over the past few decades, various synthetic approaches have emerged for the preparation and characterization of lanthanide complexes involving both phosphonate and phosphate ligands. Consequently, researchers have delved into exploring the magnetic properties of these complexes, such as their potential as single molecule magnets (SMMs) and their ability to exhibit a magnetocaloric effect (MCE). This review will encompass an examination of the crystal structures and magnetic characteristics of lanthanide complexes featuring phosphonate and phosphate ligands.

Bond Dissociation Energies of Carbene-Carbene and Carbene-Main Group Adducts

A range of carbene structures and their adducts with one another and with a selection of small-molecule electrophiles and nucleophiles were examined at the composite correlated molecular orbital theory G3MP2 level to explore ground-state "carbenic" structures, their stabilities, and reactivities. Differences between carbene general classification as a singlet electrophilic carbene or singlet nucleophilic carbene and their given reactivity are discussed. A key quantity is the carbon-carbon bond dissociation energy for carbene dimers or the carbene-adduct dissociation energy for other species. The carbene dimer bond dissociation energies span a wide range from 10 to 170 kcal/mol. The hydrogenation energies and singlet-triplet splitting were found to correlate best with the carbene's self-dimerization energy, whereas other descriptors do not. The proton and fluoride affinities of the carbenes alone prove inadequate for classifying reactivity among classes of carbenes. The self-dimerization bond dissociation energy, hydrogenation energy, and singlet-triplet splitting of various carbenes, despite sometimes large differences in proton affinity and other indicators of reactivity, provide usable metrics to correlate substantial amounts of thermodynamic and kinetic (reactivity) information regarding these structures.

Tweaking the Charge Transfer: Bonding Analysis of Bismuth(III) Complexes with a Flexidentate Phosphane Ligand

To account for the charge transfer and covalent character in bonding between P and Bi centers, the electronic structures of [P(C6H4-o-CH2SCH3)3BiCln](3-n)+ (n = 0-3) model species have been investigated computationally. On the basis of this survey a synthetic target compound with a dative P→Bi bond has been selected. Consecutively, the highly reactive bismuth cage [P(C6H4-o-CH2SCH3)3Bi]3+ has been accessed experimentally and characterized. Importantly, our experiments (single-crystal X-ray diffraction and solid-state NMR spectroscopy) and computations (NBO and AIM analysis) reveal that the P···Bi bonding in this trication can be described as a dative bond. Here we have shown that our accordion-like molecular framework allows for tuning of the interaction between P and Bi centers.