X-RAY AND MULTINUCLEAR MAGNETIC-RESONANCE STUDY OF THE COMPLEXES OF LANTHANUM(III) WITH 2,2' 6',2''-TERPYRIDINE/

The reaction between La(NO3)(3) . 6H(2)O and 2,2':6',2 ''-terpyridine (terpy) in acetonitrile solution was investigated by H-1, O-17, and La -139 NMR spectroscopy. The crystal structure of [La(NO3)(2)(terpy)(2)] [La(NO3)(4)(terpy)]. CH3CN .(1)/2H2O was determined by X-ray diffract ion: triclinic; space group P ($) over bar 1; a = 14.979(4) Angstrom, b = 17.501(10) Angstrom, c = 11.603(5) Angstrom; Z = 2; alpha = 106.34 (4)degrees, beta = 94.22(3)degrees, gamma = 83.30(3)degrees. At conver gence, R(F) = 0.053 and R(W) = 0.032 for 4012 reflections. In solution , the La-139 NMR coordination shell. O-17 NMR spectroscopy indicates t hat during the complexation by terpy, coordinated water is totally dis placed from the coordination sphere whereas the nitrate groups remain partially bound. Proton NMR data confirm the total displacement of wat er and show that two terpy molecules are in close proximity when they are coordinated to the same La(III) ion. From the NMR results, it is s hown that during the complexation process seven different La(III) spec ies can be observed: [La(NO3)(3)(CH3CN)(4)], [La(NO3)(3)(CH3CN)(3)(H2O )], [La(NO3)(3)(terpy)(CH3CN)], [La(NO3)(3)(terpy)(H2O)], (4)(terpy)(C H3CN)](-),[La(NO3)(4)(terpy)(H2O)](-), and [La(NO3)(2)(terpy)(2)](+). The structure of the cationic complex in solution shows similarities w ith the solid state compound, but the anionic complex is affected by s olvation. Comparisons are made with the La(III) complexes previously o btained with 1,10-phenanthroline and 2,2'-bipyridine as well as with d ata reported in the literature.