Structural studies of precursor and partially oxidized conducting complexes. 15. A combined neutron and x-ray diffraction study of ammonium tetracyanoplatinate chloride trihydrate, (NH4)2[Pt(CN)4]Cl0.3.3H2O

Abstract

The main structural findings reported here, which bear on the diminished electrical conductivity of (NH/sub 4/)/sub 2/(Pt(CN)/sub 4/)Cl/sub 0/./sub 3/ . 3H/sub 2/O compared to prototype K/sup 2/(Pt(CN)/sub 4/)Br/sub 0/./sub 3/ . 3H/sub 2/O, are that while the intrachain Pt-Pt spacings are shorter and are of equal length (2.88(1)A) in the K+ salt, they are longer and are of different length (2.910(5) and 2.930(5)A x rays) in the NH/sub 4//sup +/ salt. Thus the formation of alternately long and short Pt-Pt separations (dimerization) in NH/sub 4/CP(Cl) is likely one of the most important factors contributing to its electrical conduction properties. A factor which supports hypothesis is that in RbCP(Cl), the Pt-Pt distances are also of unequal length (2.924(8) and 2.877(8)A), and Rb CP(Cl) has lower room temperature conductivity than KCP(Br). The complete explanation for the structure-conductivity relationships in those POTCP complexes is obviously much more complicated, because although a Rb/sup +/ ion has nearly the same cation radius as NH/sub 4//sup +/ and RbCP(Cl) and NH/sub 4/CP(Cl) are isostructural, the low-temperature electrical conductivity (NH/sub 4/CP(Cl)<< RbCP(Cl)) is vastly different.