Organoantimony(III) and -bismuth(III) hypervalent pseudohalides. An experimental and theoretical study

The reaction between the organopnicogen(III) chlorides R2MCl and RMCl2 [M = Sb, Bi; R = 2-(Me2NCH2)C6H4] and alkali metal pseudohalides in a 1:1 and a 1:2 molar ratio, respectively, resulted in the formation of hypervalent species of type R2MX (M = Sb, X = NCO (1), NCS (2) and SeCN (3), M = Bi, X = NCO (4) and SeCN (5), and RMX2 (M = Sb, X = NCO (6) and NCS (7), M = Bi, X = NCO (8), NCS (9) and SeCN (10). The new species were characterized by multinuclear NMR (1H, 13C, 77Se where appropriate), IR spectroscopy and mass spectrometry. The molecular structures of compounds 2–5 and 7 were determined by single-crystal X-ray diffraction. In all five compounds the nitrogen atoms in the pendant arms are involved in intramolecular coordination to metal, thus resulting in a distorted square pyramidal coordination geometry (12-M-5 hypervalent species) in case of 2–5 and a distorted trigonal pyramidal coordination geometry in case of 7 (10-Sb-4 hypervalent species). The intramolecular N → M coordination determines a chiral pattern of the investigated compounds. Bi⋯Phcentroid intermolecular interactions led to dimers in case of compound 4. In all species weak CH⋯Phcentroid intermolecular contacts led to polymeric associations, e.g. polymeric chains in case of compounds 2, 3, 5 and 7 and a 2D layer structure built by chains of dimers in case of compound 4. DFT calculations and FTIR data allowed us to assign the coordination pattern of the pseudohalide ligand in the other species.