Synthesis and structural characterization of praseodymium(III) and neodymium(III) complexes of tripodal tris[2-(salicylideneamino)ethyl]amine

The preparation and characterization of praseodymium(III) and neodymium(III) complexes of heptadentate (N4O3) ligand trensal, tris [2-(salicylideneamino)ethyl] amine (H(3)L(1)), have been studied. These complexes (PrL(1) and NdL(1)) were prepared by the reaction of the praseodymium(III) or neodymium(III) complex of 1,9-bis(2-aminoethyl)-1,4,6, 9,12,14-hexaazacyclohexadecane with salicylaldehyde in acetonitrile. Alternatively, the reaction of tris(2-aminoethyl)amine and salicylaldehyde in the presence of praseodymium(III) or neodymium(III) salt in acetonitrile also gave praseodymium(III) and neodymium(III) complexes of trensal. The molecular structures of PrL(1) and NdL(1) were determined by X-ray structural analysis; these are rare examples of lanthanide heptadentate complexes in which the metal ions are coordinated by the four nitrogen atoms and the three oxygen atoms. The crystals of PT(C27H27N4O3). 0.5CH(3)CN and Nd(C27H27N4O3). 0.5CH(3)CN are both trigonal, space group P (3) over bar, a=13.713(2), c=8.093(3) Angstrom, U=1318.0(7) Angstrom(3), Z=2 for [PrL(1)]. 0.5CH(3)CN, and a=13.724(3), c=8.067(3) Angstrom, U=1315.8(7) Angstrom(3), Z=2 for [NdL(1)]. 0.5CH(3)CN. The structures were solved by heavy-atom Patterson methods and expanded using Fourier techniques; they were then refined by full-matrix least-squares procedures to R=0.033 and R(w)=0.043 for 1547 observed reflections with I greater than or equal to 3 sigma(I), R=0.028 and R(w)=0.039 for 1923 observed reflections with I greater than or equal to 3 sigma(I) for [PrL(1)]. 0.5CH(3)CN and [NdL(1)]. 0.5CH(3)CN, respectively. The individual metal ions and the apical nitrogen atoms lie on a 3-fold axis in each crystal; the molecules possess a C-3 molecular symmetry.