Two-electron reduction of bis(1,3-imidazolinium) salts 2 and 3 with KC₈ gives rise to stable diradicaloids 4 and 5, respectively. Calculations reveal a very low singlet–triplet energy gap ΔE_S–T for 5 (10.7 kcal mol⁻¹), while ΔE_S–T for 4 (29.1 kcal mol⁻¹) is rather large.

The first Sn^I diradical [(ADC^Ph)Sn]₂ (4) based on an anionic dicarbene (ADC^Ph={CN(Dipp)}₂CPh; Dipp=2,6‐iPr₂C₆H₃) scaffold has been isolated as a green crystalline solid by KC₈ reduction of the corresponding bis‐chlorostannylene [(ADC^Ph)SnCl]₂ (3). The six‐membered C₄Sn₂‐ring of 4 containing six π‐electrons shows a diatropic ring current, thus 4 may also be regarded as the first 1,4‐distannabenzene derivative. DFT calculations suggest an open‐shell singlet (OS) ground state of 4 with a remarkably small singlet–triplet energy gap (ΔE_OS–T=4.4 kcal mol⁻¹), which is consistent with CASSCF (ΔE_S–T=6.6 kcal mol⁻¹ and diradical character y=37 %) calculations. The diradical 4 splits H₂ at room temperature to yield the bis‐hydridostannylene [(ADC^Ph)SnH]₂ (5). Further reactivity of 4 has been studied with PhSeSePh and MeOTf.

The synthesis and characterization of the crystalline diphosphene radical cations [P ₂ ] ⁺ ˙ and dications [P ₂ ] ²⁺ featuring a π-conjugated C ₂ P ₂ C ₂ -framework have been reported (Dipp = 2,6- iPr ₂ C ₆ H ₃ ).

The first 1,4‐distibabenzene‐1,4‐diide compound [(ADC)Sb]₂ (5) based on an anionic dicarbene (ADC) (ADC=PhC{N(Dipp)C}₂, Dipp=2,6‐iPr₂C₆H₃) is reported as a bordeaux‐red solid. Compound 5, featuring a central six‐membered C₄Sb₂ ring with formally Sb^I atoms may be regarded as a base‐stabilized cyclic bis‐stibinidene in which each of the Sb atoms bears two lone‐pairs of electrons. 5 undergoes 2 e‐oxidation with Ph₃C[B(C₆F₅)₄] to afford [(ADC)Sb]₂[B(C₆F₅)₄]₂ (6) as a brick‐red solid. Each of the Sb atoms of 6 has an unpaired electron and a lone‐pair. The broken‐symmetry open‐shell singlet diradical solution for (6)²⁺ is calculated to be 2.13 kcal mol⁻¹ more stable than the closed‐shell singlet. The diradical character of (6)²⁺ according to SS‐CASSCF (state‐specific complete active space self‐consistent field) and UHF (unrestricted Hartree‐Fock) methods amounts to 36 % and 39 %, respectively. Treatments of 6 with (PhE)₂ yield [(ADC)Sb(EPh)]₂[B(C₆F₅)₄]₂ (7‐E) (E=S or Se). Reaction of 5 with (cod)Mo(CO)₄ affords [(ADC)Sb]₂Mo(CO)₄ (8).