Structural Diversity of Organoantimony(III) and Organobismuth(III) Dihalides Containing O,C,O-Chelating Ligands

Abstract

Eight organoantimony and organobismuth dihalides, containing two types of O,C,O-chelating (so-called pincer) ligands, 2,6-(ROCH2)C6H3 - (R = Me, L1; R = t Bu, L2; L1SbCl2 (1), L2SbCl2 (2), L1SbI2 (3), L2SbI2 (4), L1BiCl2 (5), L2BiCl2 (6), L1BiI2 (7), L2BiI2 (8)) were prepared and characterized with the help of elemental analysis, electrospray ionization mass spectrometry, 1H and 13C NMR spectroscopy, and X-ray diffraction techniques. Except for 5, which exists as a centrosymmetric dimer, all studied compounds are monomeric in the solid state and the coordination polyhedra of the central atoms are distorted square-pyramidal. Both oxygen donor atoms are coordinated to the central metal through moderately strong or strong intramolecular interactions (range of Sb−O distances 2.279(2)−2.6912(14) Å and Bi−O distances 2.379(3)−2.460(4) Å), both in cis fashion for 1 and 2 (angles O−Sb−O 116.65(5)° and 116.73(4)°) and trans fashion for 3, 4, and 6−8 (range of angles O−M−O; M = Sb or Bi, 142.26(12)−148.28(8)°). In noncoordinating solvents (CDCl3, toluene-d 8) 1−8 display structures similar to those found in the solid state based on variable-temperature 1H NMR measurements.

The synthesis of organoantimony(III) difluorides containing Y,C,Y pincer type ligands using organotin(IV) fluorinating agents

“…These values are comparable to those found for other terminal (Sb-F) fluorine atoms in some pentavalent organoantimony derivatives [9]. 1 H NMR spectra of 4 and 5 revealed one set of relatively sharp signals for both benzylic CH 2 O and OR (R = Me for 4, tBu for 5) groups at room temperature indicating fast fluxional process of coordination/de-coordination of ligands arms [22]. However, the VT-1 H NMR showed splitting of the signal of the CH 2 O groups to an AX pattern at lower temperatures (220 K) in CDCl 3 (signals of OR groups remain intact even at 220 K), these findings are indicative for cis coordination of both ligands arms at low temperature in solution of 4 and 5 [22].…”

“…These values indicate a further attenuation of this coordination, when compared with corresponding dichloride and diiodide [2,6-(MeOCH 2 )C 6 H 3 ]SbX 2 (Sb-O bond lengths 2.523(2), 2.577(2) Å , X = Cl; 2.293(2), 2.279(2) Å , X = I) [22]. The bond distances Sb1-F1 1.948(2) and Sb1-F2 1.957(2) Å are comparable to those found for Sb-F terminal bonds in other organoantimony fluorides [9,32].…”

“…1 H NMR spectra of 4 and 5 revealed one set of relatively sharp signals for both benzylic CH 2 O and OR (R = Me for 4, tBu for 5) groups at room temperature indicating fast fluxional process of coordination/de-coordination of ligands arms [22]. However, the VT-1 H NMR showed splitting of the signal of the CH 2 O groups to an AX pattern at lower temperatures (220 K) in CDCl 3 (signals of OR groups remain intact even at 220 K), these findings are indicative for cis coordination of both ligands arms at low temperature in solution of 4 and 5 [22]. 1 H NMR spectrum of compound 6 at 300 K in C 6 D 6 revealed an AX pattern for CH 2 N groups and two signals for non-equivalent (7).…”

“…Two different fluorinating agents Me 3 SnF or 2-(Me 2 NCH 2 )C 6 H 4 Sn(n-Bu) 2 F were employed for the preparation of organoantimony difluorides 4 and 5 starting from corresponding dichlorides 1 and 2 [22] (Scheme 1). The reagents, Me 3 SnF and 2-(Me 2 NCH 2 )C 6 H 4 Sn(n-Bu) 2 F were converted to the corresponding chlorides within 1 week in toluene yielding organoantimony difluorides 4 and 5 in reasonable yields after appropriate workup (see Section 4).…”

“…1E). Compounds 4-6 were prepared from corresponding [22,23], using Me 3 SnF [24] or 2-(Me 2 NCH 2 )C 6 H 4 Sn(n-Bu) 2 F [25-28] as organotin(IV) fluorinating agents. The structure of compounds 4-6 was determined both in the solution by 1 H, 13 C and 19 F NMR spectroscopy and in the solid state using X-ray diffraction techniques.…”