Serendipitous formation and characterization of K2[Pd(NO3)4]·2HNO3

Michael Zoller,Klaus Wurst,Jörn Bruns,Hubert Huppertz,Gunter Heymann

doi:10.1515/znb-2019-0018

Abstract

Abstract A potassium tetranitratopalladate(II) with the composition K2[Pd(NO3)4] · 2HNO3 was synthesized by a simple solvothermal process in a glass ampoule. The new compound crystallizes in the monoclinic space group P21 /c (no. 14) with the lattice parameters a = 1017.15(4), b = 892.94(3), c = 880.55(3) Å, and β = 98.13(1)° (Z = 2). The crystal structure of K2[Pd(NO3)4] · 2HNO3 reveals isolated complex [Pd(NO3)4]2− anions, which are surrounded by eight potassium cations and four HNO3 molecules. The complex anions and the cations are associated in layers which are separated by HNO3 molecules. K2[Pd(NO3)4] · 2HNO3 can thus be regarded as a HNO3 intercalation variant of β-K2[Pd(NO3)4]. The characterization is based on single-crystal X-ray and powder X-ray diffraction.

Highlights

Synthesis and characterization of new binary and ternary borates is an intensively investigated field of research
The crystal structure of K2[Pd(NO3)4] · 2HNO3 reveals isolated complex [Pd(NO3)4]2− anions, which are surrounded by eight potassium cations and four HNO3 molecules
To avoid the implementation of water, we investigated reactions of suitable metal precursors and borate species with fuming nitric acid (N2O4 in HNO3), in which N2O4 will capture remaining molecules of water under formation of a HNO3-HNO2 mixture

Summary

Introduction

Synthesis and characterization of new binary and ternary borates is an intensively investigated field of research. With the synthesis of K3Na[B6O9(OH)3]NO3 [4], Lu2B2O5(NO3)2 · 2H2O [5], and Pr[B5O8(OH)(H2O)0.87]NO3 · 2H2O [6], we contributed first results on the synthesis of borate nitrates These compounds were obtained from a low acidic medium, essentially via hydrothermal synthesis. Α-K2[Pd(NO3)4] was already published by Elding, Norén, and Oskarsson in 1986 In both compounds, the four squarely coordinated nitrate groups were found to be situated on the same side of the coordination plane (Fig. 1, left). All three structures consist of [Pd(NO3)4]2− anions with monodentate nitrate groups turned in pairs in one direction, just like in β-K2[Pd(NO3)4] [11], which was synthesized in 2009. The tetranitratopalladate system has been complemented by the synthesis of the novel compound K2[Pd(NO3)4] · 2HNO3 described in the following

Synthesis

X -ray structure determination

H Bond O7–H7LO2

Crystal structure

Powder diffraction data

Conclusion