Synthesis and Structure of High-Nuclearity Carboxylate-Modified Heteropolyoxovanadate Serving as a Heterogeneous Catalyst for Selective Oxidation of Alkylbenzenes.

A high-nuclearity carboxylic-modified heteropolyoxovanadate, Na 2 K 10 H 15 [P 8 V IV 24 (tart) 15 (H 2 O) 15 (OH)O 51 ]·58H 2 O [ 1 , tart = C 4 H 2 O 6 ], has been successfully synthesized by a conventional aqueous method under mild conditions. The crystallographic study reveals that compound 1 crystallizes in the tetragonal I 4 1 / a space group and is composed by a trilayer saddle-like polyoxoanion {P 8 V 24 }. Two {V 3 (tart)(H 2 O)O 11 } as linking units bridge the top {P 4 V IV 9 (tart) 7 (H 2 O) 4 (OH)O 23 } and the bottom {P 4 V IV 9 (tart) 6 (H 2 O) 9 O 22 } layers via tartrate ligands and {PO 4 } tetrahedra, resulting in a 24-nuclearity POV skeleton structure. More interestingly, compound 1 serves as a heterogeneous catalyst for the selective oxidation of diphenylmethanes with 96.2% conversion and 93.6% selectivity under the optimized conditions.