Synthesis and crystallographic characterization of a gallium salicylaldimine complex of radiopharmaceutical interest

The synthesis and structural characterization of the Ga complex of 1,1,1-tris((5-methoxysalicylaldimino)methyl)ethane is reported. The ligand affords an uncharged gallium complex with a crystallographic 3-fold axis passing through the Ga atom and the ethyl carbon atoms. The ligand occupies all 6 coordination sites about the metal by bonding through the lone pairs of the 3 imino N atoms and the three deprotonated phenolic 0 atoms. The Ga-N and Ga-O bond lengths lie in the range of values reported for octahedral Ga(III) complexes. The C-N, C-O, and C-C bond are identical to those reported for the Co(III) complex of cic,cis-1,3,5-tris(salicylaldimino)cyclohexane, Co[(sal)3tach]. The smaller twist angle of the gallium complex (52.40) can be attributed to the greater flexibility of the ligand the absence for d10 Ga of a ligand field stabilization energy which favors antiprismatic geometry for the Co(III) complex. 37 references, 1 figure, 1 table