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Fluorinated Arylarsonate-Containing Polyoxomolybdates: pH-Dependent Formation of Mo6 vs Mo12 Species and Their Solution Properties

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide We report on the synthesis and structural characterization of six novel arylarsonate-containing polyoxomolybdates with fluorinated-functionalities in the para position of the phenyl ring. The reaction of the various arylarsonic acids, RAsO 3 H 2 [ R = 4-F–C 6 H 4 (H 2 L F ), 4-F 3 C–C 6 H 4 (H 2 L CF3 ), 4-F 3 CO–C 6 H 4 (H 2 L OCF3 )] with Na 2 MoO 4 ·2H 2 O in aqueous pH 3 solution resulted in the heteropoly-6-molybdates [{(4-F–C 6 H 4 )As} 2 Mo 6 O 24 (H 2 O)] 4– ( 1 ), [{(4-F 3 C–C 6 H 4 )As} 2 Mo 6 O 24 ] 4– ( 2 ) and [{(4-F 3 CO–C 6 H 4 )As} 2 Mo 6 O 24 (H 2 O)] 4– ( 3 ), which were isolated as guanidinium salts. When the reaction was performed in aqueous pH 1 solution the inverted-Keggin type heteropoly-12-molydates [{(4-F–C 6 H 4 )As} 4 Mo 12 O 46 ] 4– ( 4 ), [{(4-F 3 C–C 6 H 4 )As} 4 Mo 12 O 46 ] 4– ( 5 ) and [{(4-F 3 CO–C 6 H 4 )As} 4 Mo 12 O 46 ] 4– ( 6 ), were obtained and isolated as sodium salts. The 6-molybdates 1 – 3 and the 12-molybdates 4 – 6 can be easily interconverted reversibly in solution as a function of pH (3 vs 1). Polyanions 1 and 3 are isostructural and they exhibit a bent hexamolybdate ring, whereas the ring is flat for 2 . The inverted-Keggin polyanions 4 – 6 are isostructural and the metal-oxo core is capped by four arylarsonate groups. All six polyanions have been characterized in the solid state by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, and hermogravimetric analysis as well as in solution by multinuclear NMR ( 1 H, 19 F). The synthetic procedures for the arsonic acids (4-F 3 C–C 6 H 4 )AsO 3 H 2 (H 2 L CF3 ) and (4-F 3 CO–C 6 H 4 )AsO 3 H 2 (H 2 L OCF3 ) are reported for the first time.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.4c02951

Authors: Arun Pal, Saurav Bhattacharya, Xiang Ma, Ahmad Ben Kiran, Cristian Silvestru, Ulrich Kortz