Flexibility in coordinative behavior of propane-1,3-diamine toward Zn(II) and Cd(II) halides:[M(1,3pn)2X2 (M=Zn, Cd; X=Cl, Br,I)].

A series of compounds of formula M(1,3pn) 2X 2 (M Zn(II), Cd(II); 1,3pn=propane-1,3-diamine; X Cl, Br, I) has been prepared; two of them (M Zn, X Cl) and (M Cd, X I) have been structurally characterized. The Zn(1,3pn) 2Cl 2 (I) compound crystallizes in the P2 1/c space group, with eight formula units in a cell of dimensions: a=12.833(4), b=16.753(9), c=13.010(4) Å, β=118.88(3) °. The Cd(1,3pn) 2I 2 (II) compound crystallizes in the P2 1/n space group with four formula units. The structures were solved with the heavy-atom method and refined by full matrix least-squares to R and R w values of 0.029 and 0.038, 0.042 and 0.058 for I and II respectively. The asymmetric unit of I consists of a dimeric [Zn- (1,3pn) 2] 2 4+ moiety, where both Zn ions are tetrahedrally coordinated to four nitrogen atoms belonging to one chelating and two bridging 1,3pn ligands. The dimeric moiety generates an infinite chain upon translation of one cell in the direction of the diagonal (1,0,1). The structure of II shows a polymeric arrangement of octahedral Cd atoms sharing both iodine atoms and 1,3pn ligands. The MN stretching vibrations are discussed and assigned in the light of the known structures