High-Pressure Synthesis and Characterization of Li2Ca3[N2]3鈥擜n Uncommon Metallic Diazenide with [N2]2鈥?/sup> Ions

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• 作者：Sebastian B. Schneider ; Markus Seibald ; Volker L. Deringer ; Ralf P. Stoffel ; Rainer Frankovsky ; Gina M. Friederichs ; Henryk Laqua ; Viola Duppel ; Gunnar Jeschke ; Richard Dronskowski ; Wolfgang Schnick
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：November 6, 2013
• 年：2013
• 卷：135
• 期：44
• 页码：16668-16679
• 全文大小：660K
• 年卷期：v.135,no.44(November 6, 2013)
• ISSN：1520-5126

文摘

Dinitrogen (N₂) ligation is a common and well-characterized structural motif in bioinorganic synthesis. In solid-state chemistry, on the other hand, homonuclear dinitrogen entities as structural building units proved existence only very recently. High-pressure/high-temperature (HP/HT) syntheses have afforded a number of binary diazenides and pernitrides with [N₂]^{2鈥?/sup> and [N₂]4鈥?/sup> ions, respectively. Here, we report on the HP/HT synthesis of the first ternary diazenide. Li₂Ca₃[N₂]₃ (space group Pmma, no. 51, a = 4.7747(1), b = 13.9792(4), c = 8.0718(4) 脜, Z = 4, wR_p = 0.08109) was synthesized by controlled thermal decomposition of a stoichiometric mixture of lithium azide and calcium azide in a multianvil device under a pressure of 9 GPa at 1023 K. Powder X-ray diffraction analysis reveals strongly elongated N鈥揘 bond lengths of d_NN = 1.34(2)鈥?.35(3) 脜 exceeding those of previously known, binary diazenides. In fact, the refined N鈥揘 distances in Li₂Ca₃[N₂]₃ would rather suggest the presence of [N₂]3路鈥?/sup> radical ions. Also, characteristic features of the N鈥揘 stretching vibration occur at lower wavenumbers (1260鈥?020 cm鈥?) than in the binary phases, and these assignments are supported by first-principles phonon calculations. Ultimately, the true character of the N₂ entity in Li₂Ca₃[N₂]₃ is probed by a variety of complementary techniques, including electron diffraction, electron spin resonance spectroscopy (ESR), magnetic and electric conductivity measurements, as well as density-functional theory calculations (DFT). Unequivocally, the title compound is shown to be metallic containing diazenide [N₂]2鈥?/sup> units according to the formula (Li+)₂(Ca2+)₃([N₂]2鈥?/sup>)₃路(e鈥?/sup>)₂.}