Heavy Group 15 Element Pacman Complexes

Calix[4]pyrrole macrocycles (Pacman ligands) were used to incorporate heavy pnictogens (As, Sb, and Bi), yielding halogeno-pnictogen complexes (<b>Pac(EX)</b>_<b>2</b>, E = As, Sb, Bi; X = Cl, I). Arsenic(III) chloro complex <b>Pac(AsCl)</b>_<b>2</b> was synthesized in solution and isolated, while arsenic(III), antimony(III), and bismuth(III) complexes (<b>Pac(AsI)</b>_<b>2</b>, <b>Pac(SbCl)</b>_<b>2</b>, <b>Pac(BiCl)</b>_<b>2</b>, <b>Pac(BiI)</b>_<b>2</b>) were formed in solution but could not be isolated. The arsenic(III) chloro complex showed temperature- and chloride-dependent dynamics similar to <b>Pac(PCl)</b>_<b>2</b>. Hydrolysis of transient iodoarsane and chlorostibane produced oxygen-bridged complexes of the type <b>Pac(E-O-E)</b>. In the case of the synthesis of <b>Pac(SbCl)</b>_<b>2</b>, an intermediate, <b>PacH</b>_<b>2</b><b>(SbCl</b>_<b>2</b><b>)</b>_<b>2</b>, was isolated and fully characterized. Through further HCl elimination, the last two HCl molecules were finally split off, resulting in the formation of <b>Pac(SbCl)</b>_<b>2</b>. Bismuth(III) analogues were detected only transiently via ¹H NMR spectroscopy. All isolated compounds were characterized spectroscopically, crystallographically, and theoretically. Reducing <b>Pac(EX)</b>_<b>2</b> complexes led to decomposition and not to the desired formation of biradical <b>Pac(E</b>^<b>·</b><b>)</b>_<b>2</b>.