Reactivity of NCN-Chelated (NCN = C6H3-2,6-(CH2NMe2)2) Antimony(III) and Bismuth(III) Oxides toward Oxides of Arsenic

Organoantimony­(III) and organobismuth­(III) oxides (LMO)2 (where L is the NCN-chelating ligand C6H3-2,6-(CH2NMe2)2 and M = Sb (1), Bi (2)) reacted smoothly with arsenic oxides As2O5 and As2O3 to form the molecular oxides [(LM)3(AsO4)2] and [(LM)2(As2O5)] (where M = Sb (3, 5), Bi (4, 6)). All compounds were characterized by electrospray ionization (ESI) mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and, in the case of 5 and 6, single-crystal X-ray diffraction (XRD) analyses. Compound 3 formed two conformational isomers in a benzene or chloroform solution, as confirmed by 1H and 13C NMR spectroscopy. As in the case of 3, 5 also formed conformational isomers in a benzene solution, whereas the bismuth analogue 6 was unstable in solution. The stabilities of the three possible conformers of 5 were studied by density functional theory (DFT) calculations.