Synthesis, Infrared and Mössbauer Characterization of Some Chloridestannate (IV) Inorganic-organic Hybrid Complexes: Sn-Ph Bonds Cleavage

Five new compounds are isolated from reactions carried out in solution. All the compounds are characterized by, Infrared and Mössbauer spectroscopies. Spectroscopic studies have shown the presence of different carracterristic bands, notably υ (PO) vibrations coming from triphenylphosphine oxide, with wide absorption due to the NH2 groups coming from urea and the intense doublet which show the presence of phenyl groups. The proposed structures, in the solid state, are discrete though hydrogen bonding interactions may occur. Event in this study is the dearylation evidenced, cleaved Sn-Ph bonds occurring in the presence of triphenylphosphine oxide or urea, during some reaction processes. In the presence of triphenylphosphine oxide, the dearylation is followed by the formation of Sn-Cl new bonds while in the presence of urea, the Sn-Ph bonds cleavage undergo with a deamination of the urea giving rise to the formation of Sn-N and Sn-Cl new bonds whose presence are ascertained by the Mössbauer parameters. The oxidation of tin (II) to tin (IV) as well as the coordination behavior of the oxonium, H3O + cation is also noted in this work. In the reaction of triphenylphosphine oxide with SnCl2. 2H2O and nitric acid, we have obtained compounds in which tin has oxidized. The reactions between urea and SnPh3Cl are the site of a species exchange which can be explained by a deamination of urea and a dephenylation of SnPh3Cl Studies aimed at understanding the processes of this transformation still unknown leading to the isolation of aminochlorotin (IV) compounds and isolating their single crystals are being carried in our laboratory (LA.CHI.MI.A).


Introduction
Organotin materials display interesting properties and have multiple applications. They exhibit, for example, inhibition towards pancreatic cancer cells [1][2][3][4], anticancer activity [5][6][7], catalysis application [8], fungicidal activity [9]. Moreover, they are used in the preparation of some thin-film transistors matrix [10]. In the seventies, several crystalline structures of tin (IV) compounds with ligand such as Ph 3 AsO, PyO, Ph 3 PO were reported [11][12][13]. In these complexes, the OSnPh 3 O cores are in a trans-trigonal bipyramidal arrangement whith the phenyl groups in equatorial positions. The Dakar group has been involved in the development of halo-and organotin (IV) class of compounds since more than two decades. We recently have described the spectroscopic characterization of the complex [(PhCH 2 ) Ph 3 P (NO 3 )] [(SnPh 3 Cl) 3 ] [14] which contains a central tridentate nitrate anion linked to tin centres. Sn-Ph bonds exhibit a reasonable labile character and can be cleaved in some conditions. Numerous works especially those reporting crystalline structures evidencing the presence of Sn-Ph bonds cleaved from partial to total dearylation [15,16] have been published. In these studies, the dearylation generally occur when reactions happen in organic solvent solutions and, new bonds are trained because the tin atom affords multiple possible synthons. In this work, we investigated, in organic solvent, at room temperature, the interactions between dichloridotin (II) dihydrate, SnCl 2 . H 2 O and, cetyltrimethylbromide, C 19 H 42 NBr or triphenylphosphine oxide, Ph 3 PO and nitric acid, HNO 3 in the one hand, triphenyltin (IV) chloride, SnPh 3 Cl and, triphenylphosphine oxide, Ph 3 PO or urea, CH 4 ON 2 in the other hand. These interactions afforded white powders whose infrared and Mössbauer characterization are carried out and reported herein characterization is reported herein.

General
Chemicals were purchased from Sigma-Aldrich (Germany) and were used without any further purification. Elemental analyses were performed at the Institut de Chimie Moléculaire, Université de Bourgogne Franche-Comté, Dijon, France. The infrared spectra were recorded on a Bruker Vector 22 spectrometer equipped with a Specac Golden Gate™ ATR device. The 119 Sn Mössbauer spectra were obtained from the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Servico de Nanotecnologia (SENAN), Laboratorio de Fisica Aplicada, Brazil. The 119 Sn Mössbauer spectra were obtained from a constant-acceleration spectrometer moving a CaSnO 3 source at room temperature. The samples were analyzed at liquid N 2 temperature, and the isomer shift values are given with respect to that source. All the Mössbauer spectra were computer-fitted assuming Lorentzian lineshapes. Mössbauer parameters are given in mm/s [abbreviations: Q.
All mixtures were stirred around 2h at room temperature under a not controlled atmosphere.
The analytical data [% calculated (% found)], have allowed to suggest the following formulae (Table 1).

Structure Description
It seems worthy to outline the oxidation of tin (II) into tin (IV) in achievement processes of complexes 1 and 2, the Sn-Ph bonds cleavage within the formation of compound 3, the Sn-Ph bonds cleavage and urea deamination occurring during the formation processes of compounds 4 and 5.
FT-IR spectroscopy Compounds 1-5 were investigated by FT-IR spectroscopy in ATR mode. In the past, several works with FT-IR tetraalkylammonium cations, triphenyphosphine oxide, carboylates and multiples other vibration bands investigation have been reported [17]. The spectrum of 1 shows absorption bands that can be assigned to cetytrimethylammonium cation (N-C, and C-H bonds) and water molecules. In fact, vibration band located at 3400 cm −1 assigned to O-H water stretching vibrations corroborate its presence in 1. Vibration bands located at 2922 cm −1 , 2849 cm −1 and 1468 cm −1 are attributed to C-H stretching and bending vibrations, whereas those at 1200 cm −1 and 1100 cm −1 correspond to C-N stretching and deformation vibrations of the cetytrimethylammonium. The rocking CH 3  Mössbauer spectroscopy and molecular structures Compounds 1-5 were also investigated by tin mössbauer spectroscopy ( Table 2).  [19,20]. We suggest in the solid state, on the basis of spectroscopic data, a discrete structure with a SnCl 5 − complex-anion coordinated to a water molecule to give the [SnCl 5 (H 2 O)] − complex which electrostatically interacts with the cetyltrimethylammonium cation ( Figure 1); the remaining water molecules are considered as lattice.   3 ] whose described structures are comprised of a central tricoordinating nitrate anion linked to tin centres [14,25]. In comparison to this nitrate behaviour, we therefore suggest, in the solid state, a two components structure.  For 3, the mössbauer parameters are consistent with cis-coordinated SnCl 4 molecule containing compounds then with the proposed formula. In the past, numerous structures with various O-donor ligands coordinated to SnCl 4 molecules in a cis or trans fashion were described, especially the crystal and mössbauer relationship of SnI 4 L 2 (L=bipy, Ph 3 PO or Ph 2 SO) complexes which exhibit cis-structures [26]. The cis-trans isomers of the adducts SnCl 4 L 2 (L=N, N-dimethylformamide (dmf), N, N-dimethylacetamide (dma), or dimethyl sulphoxide (dmso)) have also been reported [21]. On the basis of the spectroscopic data we suggest, in the solid state, in comparison to the known SnI 4 L 2 and cis-SnCl 4 L 2 , an iso-structural discrete structure comprised of a SnCl 4 molecule cis-coordinated in an octahedral fashion to two PPh 3 O molecules, the benzene molecule is considered lattice (Figure 3). For 4 and 5, the mössbauer quadrupole splitting low values of 0.60 mm. s -1 and 0.56 mm. s -1 (˂ 1 mm. s -1 ) evidence clearly absence of SnPh 3 residues, thus Sn-Ph bonds cleavage. In fact, the Sn-Ph containing compounds isomer shift and the quadrupole splitting values are generally higher than 1 mm. s -1 [14,18,21,27]. These mössbauer parameters are in accordance with the proposed formulae presumably obtained after an in situ urea degradation and Sn−Ph bonds cleavage followed by a rearrangement. The presumable exchange is uncommon. In the past, several compounds occurring a Sn−Ph bond cleavage during their isolation processes have been reported [15,16]. On the basis of spectroscopic data we suggest, in the solid state, a discrete structure which is comprised of a central tin atom coordinated to: i. For 4, a chlorine atom and three amino groups giving a SnCl (NH 2 ) 3 molecule whose octahedral coordination sphere is completed by Ph 2 CO and methanol molecules through Sn−O bonds, the benzene molecules being lattice ( Figure 4). ii. For 5, three chlorine atoms and one amino group giving a SnCl 3 (NH 2 ) molecule whose octahedral coordination sphere is completed by Ph 2 CO and methanol molecules through Sn−O bonds, the benzene molecules being lattice ( Figure 5).

Conclusion
In this study, the reaction between dichloridotin (II) dihydrate, SnCl 2 .2H 2 O exhibits a tin oxidation from 2+ to 4+. This oxidation led to the isolation of three complexes which have discrete structures. Interactions between urea and triphenyltin chloride, SnPh 3 Cl diagnosed an event in tin chemistry, an uncommon process exchange between species giving rise to aminochlorotin (IV) based compounds, when reactions are carried out in polar organic solvents, methanol for example, and in a not controlled atmosphere. This exchange follows a 1: 3 (default material: excess material) ratio and can be explained by deamination of urea and dearylation, Sn−Ph bonds cleavage of SnPh 3 Cl. Further studies in attempts to well understand the yet unknown transformation processes leading to the isolation of the aminochlorotin (IV) compounds and, isolate their single crystals are in progress in our Laboratory (LA.CHI.MI.A).