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.

Strontiumguanidinat, SrC(NH) 3 ,d ie erste Verbindung mit zweifach deprotonierter Guanidineinheit, wurdeaus Strontium und Guanidin in flüssigem Ammoniak synthetisiert und mittels Rçntgen-und Neutronenpulverdiffraktion, IR-Spektroskopie und Dichtefunktionaltheorie inklusive harmonischer Phononenrechnungen charakterisiert. Die in der hexagonalen Raumgruppe P6 3 /m kristallisierende Verbindung ist das Stickstoffanalogon des Strontiumcarbonats,S rCO 3 ,u nd dem Motiv nachs chichtartig aus Sr 2+ -Ionen und komplexen Anionen des Typs C(NH) 3 2À aufgebaut;l etztere nehmen die eigentümlicheT rinacriagestalt an. Der Vergleicht heoretischer Phononenrechnungen mit experimentellen IR-Banden sowie quantenchemische Bindungsanalysen erlauben einen ersten Einblickindie Bindungs-und Packungsverhältnisse des bisher unbekannten Anions im Kristall.

We report the crystal structure of Ba(CN 3 H 4 ) 2 as synthesized from liquid ammonia. Structure solution based on X‐ray diffraction data suffers from a severe pseudo‐tetragonal problem due to extreme scattering contrast, so the true monoclinic symmetry is detectable only from neutron powder diffraction patterns, and structure solution and refinement was greatly aided by density‐functional theory. The symmetry lowering is due to slight deviations of the guanidinate anion from the mirror plane in space group P b 2, a necessity of hydrogen bonding. At 300 K, barium guanidinate crystallizes in P 2 1 / c with a =6.26439(2) Å, b =16.58527(5) Å, c =6.25960(2) Å, and a monoclinic angle of β=90.000(1)°. To improve the data‐to‐parameter ratio, anisotropic displacement parameters from first‐principles theory were incorporated in the neutron refinement. Given the correct structural model, the positional parameters of the heavy atoms were also refinable from X‐ray diffraction of a twinned crystal. The two independent guanidinate anions adopt the all‐ trans ‐ and the anti ‐shape. The Ba cation is coordinated by eight imino nitrogens in a square antiprism with Ba−N contacts between 2.81 and 3.04 Å. The IR and Raman spectra of barium guanidinate were compared with DFT‐calculated phonon spectra to identify the vibrational modes.