The technetium(V) complex TcOL(sal), where L represents dianionic N-salicylidene-D-glucosamine and sal represents monoanionic salicylaldehyde, has been synthesized and characterized. This neutral species precipitates from a concentrated methanol solution after reaction of a 5-fold excess of the glucose derivative with tcoc14-. The presence of chelated salicylaldehyde in the Final compound does not appear to result from hydrolysis of the Schiff base ligand L prior to coordination since the reaction of tcoc14-L, and salicylaldehyde in a 1:1:1 stoichiometric ratio does not yield TcOL(sal). It thus appears that the formation of TcOL(sal) is a kinetically controlled process. The crystal structure of the title compound, (N-salicylidene-D-glucosaminato)(salicylaldehydato)oxotechnetium(V), was determined by X-ray analysis using counter data. The technetium atom is in a distorted octahedral coordination environment with the three donor atoms of the Schiff base ligand (i.e., the neutral aldimine nitrogen atom, the anionic phenolic oxygen atom of the Schiff base moiety, and the anionic hydroxylic oxygen atom of the glucopyranose ring) occupying the plane normal to the Tc=0 linkage. The coordination shell is completed by the binding of a salicylaldehyde ligand through a charged phenolic oxygen atom and a neutral carbonyl oxygen atom in positions cis and trans to the Tc=O linkage, respectively. This unusual coordination mode of salicylaldehyde, in which the neutral atom is trans to the M=0 linkage, has not been previously observed in oxo complexes containing similar ligands and presumably results from the formation of this complex by a kinetically controlled process. The length of the Tc=O bond trans to Tc=O is 2.360 (9) A, while the displacement of the Tc atom out of the mean equatorial plane toward the oxo group is 0.422 (1) A. This complex crystallizes in the orthorhombic space group P212121 with a = 6.533 (2) Å, b = 12.649 (4) Å, c = 23.675 (7) A, and V = 1956 (1) A3 with Z = 4, for 1445 observed reflections with I > 2σ(I). © 1987, American Chemical Society. All rights reserved.
Synthesis and Structure of an Amino Sugar-Schiff Base Complex of Technetium(V) Containing Salicylaldehyde in an Unusual Coordination Mode
DUATTI, Adriano;MARCHI, Andrea;MAGON, Luciano;BERTOLASI, Valerio;GILLI, Gastone
1987
Abstract
The technetium(V) complex TcOL(sal), where L represents dianionic N-salicylidene-D-glucosamine and sal represents monoanionic salicylaldehyde, has been synthesized and characterized. This neutral species precipitates from a concentrated methanol solution after reaction of a 5-fold excess of the glucose derivative with tcoc14-. The presence of chelated salicylaldehyde in the Final compound does not appear to result from hydrolysis of the Schiff base ligand L prior to coordination since the reaction of tcoc14-L, and salicylaldehyde in a 1:1:1 stoichiometric ratio does not yield TcOL(sal). It thus appears that the formation of TcOL(sal) is a kinetically controlled process. The crystal structure of the title compound, (N-salicylidene-D-glucosaminato)(salicylaldehydato)oxotechnetium(V), was determined by X-ray analysis using counter data. The technetium atom is in a distorted octahedral coordination environment with the three donor atoms of the Schiff base ligand (i.e., the neutral aldimine nitrogen atom, the anionic phenolic oxygen atom of the Schiff base moiety, and the anionic hydroxylic oxygen atom of the glucopyranose ring) occupying the plane normal to the Tc=0 linkage. The coordination shell is completed by the binding of a salicylaldehyde ligand through a charged phenolic oxygen atom and a neutral carbonyl oxygen atom in positions cis and trans to the Tc=O linkage, respectively. This unusual coordination mode of salicylaldehyde, in which the neutral atom is trans to the M=0 linkage, has not been previously observed in oxo complexes containing similar ligands and presumably results from the formation of this complex by a kinetically controlled process. The length of the Tc=O bond trans to Tc=O is 2.360 (9) A, while the displacement of the Tc atom out of the mean equatorial plane toward the oxo group is 0.422 (1) A. This complex crystallizes in the orthorhombic space group P212121 with a = 6.533 (2) Å, b = 12.649 (4) Å, c = 23.675 (7) A, and V = 1956 (1) A3 with Z = 4, for 1445 observed reflections with I > 2σ(I). © 1987, American Chemical Society. All rights reserved.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
