Structure and Properties of Tetracyanomanganate(II), [MnII(CN)4]2−, The First Paramagnetic Tetrahedral Cyanometalate Complex

A place in the sun for solutions of [(Ph₃P)₂N]₂[Mn(CN)₆] provides—by photochemical degradation—[Mn^II(CN)₄]²⁻ ions, the only homoleptic cyanide complex ion that is high spin (structure depicted on the right). Magnetic measurements indicate a high-spin ⁶A₁ ground state (S=5/2), and the cyanide ligands are virtually entirely σ donors, without significant binding contributions from d–π* back-bonding.