Further investigations of linear trirhodium complexes: experimental and theoretical studies of [Rh3(dpa)4Cl2] and [Rh3(dpa)4Cl2](BF4) [dpa = bis(2-pyridyl)amido anion]

Abstract

The linear trirhodium compound, Rh₃(dpa)₄Cl₂ (1), and its one-electron oxidation product, [Rh₃(dpa)₄Cl₂]BF₄ (2), have been synthesized and studied extensively. The magnetic measurement for compound 1 shows that it possesses one unpaired electron that is assigned to occupy the σ_nb orbital (²A₂) by DFT calculations. Upon oxidation, a β-spin electron of 1 is removed, that causes compound 2 to exhibit a triplet ground state. DFT calculations indicate that the two unpaired electrons of 2 occupy σ_nb and δ* orbitals (³B₁), which is supported by ¹H NMR spectrum. Unlike their isoelectronic analogues [Co₃(dpa)₄Cl₂] (3) and [Co₃(dpa)₄(Cl)₂]BF₄ (4), both compound 1 and 2 do not display the spin-crossover phenomenon. The reason may be attributed to the relative large energy gap between ³B₁ and open-shell singlet ¹B₁ states.