Synthesis and characterization of technetium(V) 8-quinolinolates. X-ray crystal structure of cis-chlorobis(2-methyl-8-quinolinolato)oxotechnetium(V)

Abstract

Technetium(V) complexes of 8-quinolinolates of the form TcOL/sub 2/X (L = 8-quinolinolate and its 5,7-dichloro, 5,7-dibromo, 5-nitro, and 2-methyl derivatives; X = Cl, Br) have been synthesized and characterized. These neutral species precipitate from methanol after reaction of the quinolinolate ligand with TcOX/sub 4//sup -/. High performance liquid chromatography analyses of the complexes show that the halide ligand of cis-TcO(8-quinolinolate)/sub 2/X is susceptible to solvolysis in methanol, forming what is believed to be TcOL/sub 2/(OCH/sub 3/); when X is Cl, the specific first-order rate constant governing this process is 1 X 10/sup -4/s/sup -1/ (25/sup 0/C, no ionic strength, in methanol). A single-crystal X-ray structure determination shows that the chlorobis(2-methyl-8-quinolinolato)oxotechnetium(V) complex, TcO(CH/sub 3/C/sub 9/H/sub 5/NO)/sub 2/Cl, formula weight 467, has a distorted-octahedral coordination geometry, with the chloro and oxo ligands in a cis configuration. A oxo-induced structural trans effect characteristic of M=O moieties is manifested in a lengthening of the Tc-O bond trans to the yl oxygen and a displacement of the Tc atom out of the mean equatorial plane. This complex crystallizes in the triclinic centrosymmetric space group P anti-1 with a = 7.693 (2) A, b = 9.337 (2) A, c = 12.739 (3) A, ..cap alpha.. =more » 86.52 (2)/sup 0/, ..beta.. = 85.99 (2)/sup 0/, ..gamma.. = 84.12 (2)/sup 0/, and V = 907 (2) A/sup 3/, with Z = 2, for 2882 observed reflections with I/sub 0/ greater than or equal to 2sigma(I). Structural aspects of metal complexes containing 8-quinolinolate ligands are discussed. 32 references, 4 figures, 6 tables.« less