DEARYLATION IN THE INTERACTIONS BETWEEN (Et3NH)HC2O4 OR (Et3NH)2C2O4 AND SnPh3Cl: INFRARED STUDY

Five new oxalato, hydrogenoxalato and hydrogenocarbonato adducts (three) and complexes (two) obtained on allowing (Et3NH)HC2O4 or (Et3NH)2C2O4 to react with SnPh3Cl have been studied by infrared spectroscopy, then discrete structures suggested on the basis of spectroscopic data. The anions behave as monochelating ligands, the environments around the metallic centres being octahedral. In two of the compounds, the benzene molecules obtained in situ are lattice. In all these structures when considering the cation involved in extra hydrogen bonds, a supramolecular architecture may be obtained.


INTRODUCTION
During the past few decades, the synthesis of new molecules belonging to organo-and halotin(IV) family have been of great research interest worldwide due to their applications in medicine and industry and also for structural considerations [1][2][3][4][5].
In this dynamic our group has initiated here the study of the interactions between (Et3NH) HC2O4 or (Et3NH)2C2O4 and SnPh3Cl which has yielded the five studied adducts and complexes. The new compounds obtained have been studied by infrared technic and structures suggested on the basis of infrared data. When (L1) is allowed to react with SnPh3Cl, in ethanol in the ratio 1/1, 2/1 and 1/2 -A, B, C-, white powders are collected after a slow solvent evaporation. When ethanolic solutions of (L2) and SnPh3Cl are allowed to react in 1/2 and 1/1 ratio -D and E-white precipitates are obtained, stirred around two hours and filtered. The analytical data [% Calculated (% Found)], summarized on Table 1, have allowed to suggest the following formulae:

MATERIALS AND METHODS
The elemental analyses have been obtained from the Microanalyses Laboratory (University of Burgundy, Dijon-France). The infrared spectra have been obtained from the University of Caen-France using a Brucker FT-IR spectrometer. IR abbreviations: broad (br), very strong (vs), strong (s), medium (m), shoulder (sh), weak (w).
The chemicals were obtained from ALDRICH Company-Germany-and used as such.

General considerations
It seems worthy to outline the fact that the three first compounds -hydrogenoxalato-were obtained after a slow solvent evaporation while the two last ones -oxalato-were precipitates.
Dearylation of SnPh3Cl into SnPh2Cl2 occurs in the obtention of A, B, C and into SnPhCl3 for D and E (dearylation and lattice benzene molecules have yet been reported by Alcock and Roe [6]). For the compound C, beside the dearylation a cleavage of the C-C bond of the hydrogenoxalate is observed leading to an hydrogenocarbonate.

Spectroscopic study
Let us consider the main infrared data of the studied compounds: For all these studied compounds we just consider the complex-anion for proposing a structure.
Dealing with hydrogenoxalate, Braga et al [7] and Viadhyanathan et al [8] have reported structures containing hydrogen bonded dimers of [HC2O4]with a ten atoms ring. For our two hydrogenoxalate adducts we will consider the anion in this dimeric form.
For A the infrared data allows to suggest a structure consisting of the above dimeric hydrogen bonded hydrogenoxalates monochelating two SnPh2Cl2 molecules, the environment around the tin centre being octahedral (Figure 1). Fig. 1. Proposed structure for A.
The structure of B is deduced from the one of A on adding, two lattice benzene molecules (Figure 2). The main features of the spectrum of the compound C is the strong reduction of the intensity of the bands of the hydrogenoxalate which has turned into an hydrogenocarbonate.
For C, a basic hydrogen bonded hydrogenocarbonates dimer chelates four SnPh2Cl2 molecules (Figure 3). The environment around the tin centres is octahedral -four benzene molecules obtained in situ are lattice. The number of stretching bands for D and E -only two with a little splitting due to crystal effects-allows concluding to the presence of a centrosymmetrical oxalate.
A structure containing a seven coordinated tin centre has yet been reported by Ma et al for aqua-dimethyl-bis (2pyrazinecarboxylato-N,O)-tin(IV) trihydrate [9]. We suggest for D a structure consisting of an oxalate monochelating [SnPhCl4]leading to an heptacoordinated tin centre (Figure 4). The structure of E is deduced from the one of D on withdrawing one chloro atom leading to an octahedral environment ( Figure 5). In all these structures the cation may be involve through hydrogen bonds leading to supramolecular architectures.

CONCLUSION
The five new oxalato, hydrogenoxalato and hydrogencarbonato compounds studied here have discrete structures with mainly a monochelating anion, the environments around tin centres being in most cases octahedral, the tin centre being in an heptacoordinating environment in one case. Mono-or bidearylations of SnPh3Cl occurs in the studied compounds leading to SnPh2Cl2 and SnPhCl3 adducts, the benzene molecules obtained in situ being lattice. When extra hydrogen bonds involving the cation are considered, supramolecular architectures may be obtained.

ACKNOWLEDGMENTS
We thank Dr Laurent Plasseraud (University of Burgundy, Dijon-France) and Dr Jocelyne Levilain (University of Caen-France) for equipment support.