An Open‐Shell Singlet Sn(I) Diradical and H(2) Splitting

The first Sn(I) diradical [(ADC(Ph))Sn](2) (4) based on an anionic dicarbene (ADC(Ph)={CN(Dipp)}(2)CPh; Dipp=2,6‐iPr(2)C(6)H(3)) scaffold has been isolated as a green crystalline solid by KC(8) reduction of the corresponding bis‐chlorostannylene [(ADC(Ph))SnCl](2) (3). The six‐membered C(4)Sn(2)‐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 H(2) at room temperature to yield the bis‐hydridostannylene [(ADC(Ph))SnH](2) (5). Further reactivity of 4 has been studied with PhSeSePh and MeOTf.