Synthesis, Structure, and Properties of SrC(NH)₃, a Nitrogen‐Based Carbonate Analogue with the Trinacria Motif

Abstract

Strontium guanidinate, SrC(NH)3 , the first compound with a doubly deprotonated guanidine unit, was synthesized from strontium and guanidine in liquid ammonia and characterized by X-ray and neutron diffraction, IR spectroscopy, and density-functional theory including harmonic phonon calculations. The compound crystallizes in the hexagonal space group P63 /m, constitutes the nitrogen analogue of strontium carbonate, SrCO3 , and its structure follows a layered motif between Sr(2+) ions and complex anions of the type C(NH)3 (2-) ; the anions adopt the peculiar trinacria shape. A comparison of theoretical phonons with experimental IR bands as well as quantum-chemical bonding analyses yield a first insight into bonding and packing of the formerly unknown anion in the crystal.

Synthesis, Crystal Structure, Polymorphism, and Magnetism of Eu(CN3H4)2 and First Evidence of EuC(NH)3

“…Compared to both SrC(NH)3 [30] and YbC(NH)3 [31], EuC(NH)3 shows a shorter a-and a longer c-axis, while the volume falls in-between the two. The C-N bonds are found to be somewhat short at [30] and YbC(NH) 3 [31], EuC(NH) 3 shows a shorter a-and a longer c-axis, while the volume falls in-between the two. The C-N bonds are found to be somewhat short at 1.328(1) Å, close to a double bond although the bond order should be 1 1 / 3 .…”

“…Progressing from there, we recently reported doubly deprotonated guanidinates-in SrC(NH)3 and YbC(NH)3-and the first magnetic guanidinate, Yb(CN3H4)3, a non-Curie-Weiss paramagnet [30,31].…”

“…Preliminary thermogravimetric analysis (TGA) measurements of α-and β-Eu(CN3H4)2 show a two-step decay. The first step around 155 °C corresponds to the loss of two equivalents of ammonia, typical for guanidinates [30,31,35], to arrive at the hydrogen cyanamide Eu(NCNH)2. This phase has not been prepared before.…”

“…For EuC(NH) 3 , Rietveld refinements were performed with the Jana2006 suite using the reported SrC(NH) 3 structure type [30] as the starting model. The hydrogen atoms were located by DFT calculations (see below).…”

“…This compound is isostructural to SrC(NH) 3 [30] and YbC(NH) 3 [31] and crystallizes in the hexagonal space group P6 3 /m with a = 5.1634(7) Å, c = 7.1993(9) Å, V = 166.23(4) Å 3 , and Z = 2 ( Figure 8; Table 2). As for YbC(NH) 3 , DFT calculations were used to locate the hydrogen atoms, a method validated in reference [46] (Table 4).…”