Orbital energy mismatch engenders high-spin ground states in heterobimetallic complexes

Scott C. Coste, Tyler J. Pearson, Alison B. Altman, Ryan A. Klein, Brian A. Finney, Michael Y. Hu, E. Ercan Alp, Bess Vlaisavljevich, Danna E. Freedman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The spin state in heterobimetallic complexes heavily influences both reactivity and magnetism. Exerting control over spin states in main group-based heterobimetallics requires a different approach as the orbital interactions can differ substantially from that of classic coordination complexes. By deliberately engendering an energetic mismatch within the two metals in a bimetallic complex we can mimic the electronic structure of lanthanides. Towards this end, we report a new family of complexes, [Ph,MeTpMSnPh3] where M = Mn (3), Fe (4), Co (5), Ni (6), Zn (7), featuring unsupported bonding between a transition metal and Sn which represent an unusual high spin electronic structure. Analysis of the frontier orbitals reveal the desired orbital mismatch with Sn 5s/5p primarily interacting with 4s/4p M orbitals yielding localized, non-bonding d orbitals. This approach offers a mechanism to design and control spin states in bimetallic complexes.

Original languageEnglish (US)
Pages (from-to)9971-9977
Number of pages7
JournalChemical Science
Volume11
Issue number36
DOIs
StatePublished - Sep 28 2020

Funding

The aggregate data here allow us to construct a qualitative MO picture (shown in Fig. 6) which describes the M\u2013Sn bonding interaction. A foundational aspect of ligand \uE103eld theory towards describing metal\u2013ligand interactions is the introduction of covalency which implies d orbital-based MOs have metal\u2013ligand antibonding character. Indeed, crystallographic, spectroscopic, and theoretical data show that the Sn donor forms a polar-covalent bond in which electron density shi\uE09Ds away from Sn with more electronegative transition metals. However, we \uE103nd that the 3d-based MOs have no M\u2013Sn antibonding character, countering the classical MO description of coordination complexes. Consequently, the electronic and magnetic properties in 3\u20136 are more like a free ion description with respect to the M 3d orbitals despite the covalent M\u2013Sn interaction. This is surprising as the Sn 5s/5pz and M 3dz2 orbitals have appropriate symmetry and orbital overlap to form a bonding interaction. We posit that the origin for this observation is energetic mismatch between the M 3d orbitals and the electropositive Sn donor orbitals. The Hirshfeld charge decomposition analysis supports this as the higher lying M 4s, 4p, and 4d orbitals have more atomic Sn contribution than the 3d-based MOs. This suggests that the localization of the M 3d orbitals are due to the higher energy of the Ph3Sn donor orbitals relative to the 3d orbitals. This energetic mismatch is supported by atomic ionization potentials and energies of the hydrogen-like atomic orbitals.55

ASJC Scopus subject areas

  • General Chemistry

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