Configurations of 1,3-bis(aryl)-1,3-diaza-2-thiaallenes in the crystal state

The σ,π-mixing responsible for the Z,Z configuration of the title compounds is indifferent to both withdrawing (NO₂) and releasing (OMe) π-electron character of ortho-substituents, and the arrangement of aromatic rings in the Z,E configuration orthogonally to the NSN plane is a universal way to overcome steric hindrances due to bulky (Bu^t, Br) ortho-substituents.