The nature of the Pt chain distortion in the potassium-deficient krogmann salt, K1.75Pt(CN)41.5H2

Abstract The recent discovery of the incommensurate superlattice in K2Pt(CN)4 Br0.3 · 3H2 O and the interpretation based on Peierls distortion is of continuing high interest. By means of an x-ray crystallographic study of K1.75 Pt(CN)41.5H2O we have recently shown the existence of a transversely distorted, non-linear Pt chain in this partially oxidized conducting salt. The main findings of the structure analysis were 1. the structure contains stacks of nearly planar cyanoplatinate groups aligned in a distorted chain parallel to the triclinic c axis; 2. the cell contains 4 formula units hence is stoichiometric, hence there is no essential disorder; 3. there are 3 non-equivalent Pt atoms and two distinct Pt-Pt separations 2.966(1) and 2.978(1) A in the chain; and 4. the maximum transverse Pt displacement is 0.198(1) A. The R-factor at the current refinement stage is 0.054.