NEW TRANSITION METAL OXALATO COMPLEXES WITH DABCOH22+ AS ADVERSE CATION: SYNTHESIS AND INFRARED STUDY

: On allowing DABCOH 2 (HC 2 O 4 ) 2 to react with transition metal dihalides in ethanol, a new series of complexes of general formula M(oxalate) 2 DABCOH 2 2+ . nDABCOH 2 2+ .2X - (n=1/2;1) have been obtained. When (n=1) a dimeric structure is suggested, the two monomeric species being hold together by biprotonated DABCO through N-H…O hydrogen bonds. In the case of the complex M(oxalate) 2 DABCOH 2 2+ .1/2 DABCOH 2 2+ .2X - -M = Ni, Cu- the structure is an infinite chain. The environment around the metallic centers is octahedral or square pyramidal. The oxalate behaves as a monochelating and hydrogen bonds involved ligand or is only concerned by hydrogen bonds.


INTRODUCTION
The acidic substituted ammonium salts, because of their solubility in organic solvents have been used by several groups to reach new complexes of metals, transitional or not [1][2][3][4][5]. In this dynamic focusing in oxalic acid salts, our group has yet reported several papers in this field [6][7][8]. Rao et al. [9] have reported the crystal structure of DABCOH2(HC2O4)2. We initiate here the study of the interactions between Rao et al. salt [9] and some transitional metal halides which has yielded ten new complexes containing the core DABCOH2(C2O4).MC2O4.nDABCOH2.2X -(X = Cl, Br) (n=1/2;1) whose infrared study have been carried out then structures suggested on the basis of infrared data.

MATERIALS AND METHODS
We have obtained Rao et al. salt [9] -DABCOH2(HC2O4)2 -(L) on mixing DABCO and oxalic acid in ethanol in ½ ratio after a slow solvent evaporation.
The analytical data reported below have allowed suggesting the following formulae for the ten new complexes (Table 1). Elemental analyses and IR spectra (performed on a Brucker FT-IR spectrometer) have been obtained from Rhodes University of Grahamstown-South Africa.
IR abbreviations: br (broad) vs (very strong); s (strong); m (medium). Chemical reagents are purchased from ALDRICH Company (Germany) and used as received. For the complex (D) we can maintain the dimeric nature of the above complexes but in this case the string connecting the two complexe -anions is DABCOH2 2+ ……Cl -……..DABCOH2 2+ rather than one DABCOH2 2+ . The two chloride atoms involved in the strings are then connected by another DABCOH2 2+ ……Cl -……..DABCOH2 2+ string, the remaining chloride atom being involved in electrostatic interactions with the main component of the structure. The hydrogen bonds between the biprotoned DABCO and the oxalates are bifurcated ones ( Figure 2). This compound is (A) to which has been added two molecules of DABCOH2C2O4 the suggested structure is a monomer consisting of a [CoCl2(C2O4)] 2core as in (A) to which are connected in both sides [(DABCOH2)2C2O4] 2+ ; the structure is reported in Figure 3.  The structure of the complex (I) is also dimeric, the core being [NiCl(C2O4)2] 3-(the environment around the metallic centre is a square based pyramid), the biprotoned DABCO connecting through bifurcated N-H…O,O hydrogen bonds the oxalates of each core but also the chlorido atoms through N-H…Cl leading to an infinite chain structure reported in Figure 5. For (J) a lattice molecule of ethanol is added to the (I) structure.

CONCLUSIONS
The studied complexes have dimeric -or infinite chain-structures, the environments being octahedral or square based pyramidal, the oxalate behaving as a monochelating and bifurcated hydrogen bonds involved ligand or only bifurcated hydrogen bonds concerned. Biprotonated DABCO alone or biprotonated DABCO, chlorido atoms and oxalate anion strings are involved in all the structures connecting oxalates or chloride and bromido atoms.