CRYSTAL STRUCTURE OF BIS-(AQUATRIMETHYLSTANNYL)OXALATE [Me 3 Sn(H 2 0)] 2 C 2 0 4 Libasse Diop, 1 Mary F Mahon, 2 Kieran C Molloy* 2 and Mamadou Sidibe 1 1 Department de Chimie, Faculte des Sciences et Techniques, Universite Cheikh Anta Diop de Dakar, Dakar, Republique du Senegal 2 School of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK Abstract The structure of bis-(aquatrimethylstannyl)oxalate has been determined and found to contain metal atoms in ayxutsrqonmlihfecaSB trans-0 2 SnC 3 environment. Each tin atom is bonded axially by one water and a monodentate oxalate, while the lattice structure is dominated by hydrogen bonds rather than intermolecular carboxylate bridges. Introduction We have been interested for some time in the structural chemistry of organotin(IV) derivatives of mono- and di-basic oxyanions (CI0 4 \ N0 3 , Cr0 4 2 ", Se0 4 2 ' etc), a group of compounds which have been largely overlooked crystallographically. In addition to the known structure determinations of (R 3 Sn) 2 C0 3 (R = Me, ; Bu) (1, 2) and Me 3 SnN0 3 (H 2 0) (3), we have reported the structure of (Me 3 Sn) 2 S0 4 .2H 2 0 (4) and, more recently, (Me 3 Sn) 2 Se0 3 .H 2 0.(5) Organotin oxalates are a group of compounds which come into this general area of interest and on which we have previously reported spectroscopic data (6). From the structural point of view both neutral and anionic tin oxalate complexes are known and display a variety of structures. The main themes which emerge from the collective structural data available are that such compounds generally incorporate either chelating e.g. [(Ph 3 As0)(N0 3 )Ph 2 Sn] 2 C 2 0 4 (7) or bridging e.g. [(Bu 3 Sn) 4 (C 2 0 4 ) 3 (H0Et) 2 ] 2 " (8) carboxylate functionalities. Some species e.g. [(Ph 3 Sn) 3 (C 2 0 4 ) 2 ]" (9) and (Cy 3 Sn) 2 C 2 0 4 (10) contain both bonding modes, the latter example simultaneously generating isomeric five-coordinate tin environments in the same species. The chelating nature of the oxalate manifests itself through two oxygens which are cis- to the C-C bond e.g. [(Ph 3 As0)(N0 3 )Ph 2 Sn] 2 C20 4 (7), formation of a five- membered SnC 2 0 2 ring being universally favoured over the four-membered Sn0 2 C ring which would arise if each carboxylate group acted independently. Bridging behaviour arises from the two oxalate groups in unison i.e. in which the intermolecular interaction is from the opposite end of the oxalate to the nominally intramolecular Sn-0 bond e.g. [(Ph 3 Sn) 3 (C 2 0 4 ) 2 ]' (9), (Cy 3 Sn) 2 C 2 0 4 (10). It would appear that no examples exist in which each end of the dicarboxylate acts as a separate bridging unit to generate parallel chains of molecules, even when the two functionalities are separated by methylene units e.g. (Me 3 Sn) 2 malonate (11). In this paper we report the structure of [Me 3 Sn(H 2 0)] 2 C 2 0 4 , in which the oxalate shows preference for hydrogen bonding rather than bridging/chelating behaviour towards tin. Experimental Details of the instruments used for measuring IR (12), NMR and Mössbauer spectra (13) are given elsewhere. Synthesis of Bis-(aquatrimethylstannyl)oxalate (1) SnMe 3 CI (3.00g, 15mmol) and [Et 4 N] 2 C 2 0 4 .4H 2 0 (3.17g, 7.5mmol) were mixed in in ethanol. The resulting precipitate was recrystallised from acetonitrile to yield the title compound in 73% yield (m.p. > 235°C). Analysis, found (calculated for C 8 H 22 0 6 Sn 2 ): 21.4(21.3),zyvspnmcbaVSROJIHC Η 4.92(4.92), Sn 52.1(52.6)%. IR(cm" 1 ): 3340, 3242b [v(H 2 0)], [1635vs, 1282vs [v asym s ™ m (C0 2 )], 549m, 562m [Vasym(C3 Sn)], 227m [v(SnO)]. Mössbauer (mms 1 ): IS 1.30, QS 3.82. NMR (DMSO; δ ppm, J Hz), 1 H: 649 Brought to you by | Purdue University Libraries Authenticated Download Date | 1/22/15 2:06 PM