New quaternary arsenide oxides with square planar coordination of gold(i) – structure, 197Au Mössbauer spectroscopic, XANES and XPS characterization of Nd10Au3As8O10 and Sm10Au3As8O10. Issue 12 (26th February 2015)

• Record Type: Journal Article
• Authors: Bartsch, Timo; Niehaus, Oliver; Johrendt, Dirk; Kobayashi, Yasuhiro; Seto, Makoto; Abdala, Paula M.; Bartsch, Manfred; Zacharias, Helmut; Hoffmann, Rolf-Dieter; Gerke, Birgit; Rodewald, Ute Ch.; Pöttgen, Rainer
• Is Part Of: Dalton transactions. Volume 44:Issue 12(2015)
• Page Start: 5854
• Page End: 5866
• Publication Date: 2015-02-26
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt00193e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The title compounds were synthesised and characterised. Abstract : The quaternary gold(i ) arsenide oxides Nd10 Au3 As8 O10 and Sm10 Au3 As8 O10 were synthesized in sealed quartz ampoules from the rare earth (RE) elements, their appropriate sesquioxides, arsenic, arsenic(iii ) oxide and finely dispersed gold at maximum annealing temperatures of 1223 K. Both structures were refined from X-ray single crystal diffractometer data at room temperature and at 90 K. Nd10 Au3 As8 O10 and Sm10 Au3 As8 O10 crystallize with a new structure type that derives from the BaAl4 structure through distortions and formation of ordered vacancies. The structures consist of stacked polycationic [RE10 O10 ] 10+ layers with oxygen in tetrahedral rare earth coordination and polyanionic [Au(i )3 (As2 )4 ] 10− layers with gold in square planar or rectangular planar coordination of four arsenic dumbbells (255 pm As1–As2). In contrast to the well known ionic rare earth oxide layers, the gold arsenide layers rather show covalent bonding and account for the metallic nature of these two new arsenide oxides. This is confirmed by electronic structure calculations and resistivity measurements. The oxidation state of gold was investigated by 197 Au Mössbauer, X-ray absorption near edge structure (XANES) and photoelectron (XPS) spectroscopy. Due to missing comparative gold arsenide compounds, the monovalent gold phosphide oxides RE2 AuP2 O were measured for comparison. The XANES measurements additionally comprise monovalent gold arsenides REAuAs2 . The XPS study contains BaAuAs as reference compound instead. Combination of all data clearly indicates Au(i ), which was not observed in square planar coordination up to now. Temperature dependent magnetic susceptibility data show Curie–Weiss paramagnetism for Nd10 Au3 As8 O10 and no magnetic ordering down to 2.5 K. Sm10 Au3 As8 O10 shows the typical Van Vleck type paramagnetism for samarium compounds along with a transition to an antiferromagnetically ordered state at T N = 8.6 K.