Chemistry of the Bis(imine)-Based Tetradentate Ligand Stabilized Group 14 E(II) Cations (E=Ge and Sn)

At the limits of bisphosphonio-substituted stannylenes

Donor stabilization of Sn(II) and Pb(II) halides with 1,1'-ferrocenylene bridged bisphosphanes has been explored for Fe(C5H4P(C6H5)2)2 (dppf), and Fe(C5H4PH(C4H9))2. These bisphosphanes are reacted with SnBr2 and PbCl2 with and without additional Lewis acid (AlCl3) forming acyclic and cyclic donor adducts from which the latter represent bisphosphoniotetrylenes. Since dynamic exchange in solution is observed, characterization includes solution and solid-state NMR in addition to SC-XRD, amended by DFT calculations.

Utilization of a Tris(carbene)borate Ligand for Umpolung Reactivity of a Nucleophilic Tin(II) Cation Salt

We show that a tris(carbene)borate (TCB) ligand, namely [PhB(^tBuIm)₃]^- ([PhB(^tBuIm)₃]^- = phenyltris(3-tert-butylimidazol-2-ylidene)borato), is capable of stabilizing an unprecedented nucleophilic Sn(II) cation salt. Unlike known Sn(II) cations, the strong electron-donating ability of [PhB(^tBuIm)₃]^- makes the cationic tin atom electron-rich, σ-donating yet slightly π-accepting, which allows for the ensuing facile oxidation with o-chloranil and S₈ as well as coordination with coinage metals. The former oxidations give the Sn(IV) cation salts, while the latter reactions produce the metal complexes. The electronic structures of these species are thoroughly probed by quantum chemical computations. These results uncover an added role for TCB ligands in isolating unprecedented p-block species.

Structure and bonding of proximity-enforced main-group dimers stabilized by a rigid naphthyridine diimine ligand

The development of ligands capable of effectively stabilizing highly reactive main-group species has led to the experimental realization of a variety of systems with fascinating properties. In this work, we computationally investigate the electronic, structural, energetic, and bonding features of proximity-enforced group 13-15 homodimers stabilized by a rigid expanded pincer ligand based on the 1,8-naphthyridine (napy) core. We show that the redox-active naphthyridine diimine (NDI) ligand enables a wide variety of structural motifs and element-element interaction modes, the latter ranging from isolated, element-centered lone pairs (e.g., E = Si, Ge) to cases where through-space π bonds (E = Pb), element-element multiple bonds (E = P, As) and biradical ground states (E = N) are observed. Our results hint at the feasibility of NDI-E₂ species as viable synthetic targets, highlighting the versatility and potential applications of napy-based ligands in main-group chemistry.