Bidentate Sulfur Dioxide Complexes of Scandium, Yttrium, and Lanthanum Difluorides

Abstract

The SO2 complexes of scandium, yttrium, and lanthanum difluorides [MF2(O2S)] were prepared via the reactions of laser-ablated metal atoms and SO2F2 upon UV–vis irradiation in cryogenic matrixes. The presence of bidentate SO2 ligand in the products was demonstrated by the characteristic infrared absorptions as well as isotopic frequency ratios from both S18O2F2 and 34SO2F2 experiments and is further supported by DFT calculations. All three product molecules were predicted to have nonplanar C 2v symmetry with the SO2 ligand bound to the metal center through both oxygens. The computed S–O bond length and stretching frequencies of ligated SO2 approach those of SO2 – as a result of electron transfer from metal center to the 1π* orbital of SO2, in agreement with the results from bonding analysis. On the basis of DFT calculations, fluorine transfer from SO2F2 to the metal center to form the MF2(O2S) complexes is highly exothermic. Although a proposed intermediate in the form of MF­(O2SF) was predicted to be stable, it was not observed in the experiments, presumably because of the low energy barrier for further isomerization to MF2(O2S).

Preparation of Group 3 Metal Sulfur Monoxide Complexes via Oxidation of Metal Atoms using SOF2 in Cryogenic Matrixes

“…The ScÀ F bond length of 1.849 Å is shorter than the YÀ F and LaÀ F bond lengths of 2.016 and 2.121 Å, following the changes in the MÀ F bond lengths of group 3 metal complexes MF 3 , OMF 2 and MF 2 (O 2 S). [16,21,23] The computed SÀ O distances are barely affected by metal atoms, and are all around 1.59 Å. This is about 0.1 Å longer than that of neutral SO molecule (1.488 Å) but close to those of the SO ligands of group 5 OMF 2 (η 2 -SO) complexes (~1.59 Å) predicted at the same level of theory that feature a superoxo-like character.…”

“…The yttrium and SOF 2 reaction product bands were observed at 888.2, 565.4 and 558.3 cm À 1 . According to the experiments with 34 S and 18 O enriched samples, the 888.2 cm À 1 band shifts to 880.0 and 854.1 cm À 1 respectively, giving a 32 S/ 34 S frequency ratio of 1.0093 and a 16 O/ 18 O frequency ratio of 1.0399, which confirms the existence of a SO ligand in this yttrium product molecule. The fact that negligible isotopic shifts were observed for the 565.4 and 558.3 cm À 1 absorptions indicates that they should be due to the antisymmetric and symmetric FÀ YÀ F stretches with the former being more intense than the latter.…”

“…[22] The bands at 886.7, 685.4, 644.9 and 486.0 cm À 1 observed from the reactions of scandium and SOF 2 in argon matrix exhibit the same tendency upon sample annealing and UV-vis irradiation, which suggest that they belong to different vibrational modes of the same complex. The 886.7 cm À 1 band exhibits a 32 S/ 34 S isotopic frequency ratio of 1.0093 and a 16 O/ 18 O isotopic frequency ratio of 1.0395. Both shifts are close to the values of the SÀ O stretch for OTiF 2 (η 1 -OS) (1.0419 and 1.0081), [20] indicating that this band is also due to a SÀ O stretch.…”

“…[11][12][13][14] It has been recently demonstrated that sulfuryl fluoride (SO 2 F 2 ) can serve as a precursor for the convenient synthesis of metal-sulfur dioxide complexes when it reacts with metal atoms in cryogenic matrixes. [15][16][17] In particular, sulfur monoxide complexes were obtained in some cases as long as there are enough valence electrons from the metal center to support one SO and one oxo ligand as well as two fluoro ligands. [18,19] The reactions of molybdenum and tungsten atoms with SO 2 F 2 in solid matrixes gave rise to side-on OMoF 2 (η 2 -SO) and OWF 2 (η 2 -SO), which are considered as peroxo-like metal complexes, (OMoF 2 ) 2 + (SO) 2À and (OWF 2 ) 2 + (SO) 2À .…”

“…[20] The situation is quite different for group 3 metals, and only bidentate sulfur dioxide complexes in the form of ScF 2 (O 2 S), YF 2 (O 2 S) and LaF 2 (O 2 S) were obtained from the reactions of metal atoms and SO 2 F 2 . [16] The absence of group 3 metal-SO complexes makes it difficult to probe the coordination chemistry of sulfur monoxide in the case of group 3 metals, and a different reaction route is therefore needed for their preparation. In this paper, we report the preparation of side-on ScF 2 (η 2 -SO), YF 2 (η 2 -SO), and LaF 2 (η 2 -SO) complexes via the reactions of laser-ablated group 3 metal atoms with thionyl fluoride (SOF 2 ) in cryogenic matrixes.…”