Synthesis and electrochemistry of ([mu]-oxo)technetium complexes with bipyridine and halide ligands. Crystal structures of ([mu]-O)[X(bpy)[sub 2]Tc][sub 2]X[sub x][center dot]bpy (X = Cl, Br) and ([mu]-O)[Cl(phen)[sub 2]Tc][sub 2]Cl[sub 2]
- Boston College, Chestnut Hill, MA (United States)
Dinuclear [mu]-oxo complexes of technetium, in which the two Tc atoms are in intimate electronic communication, have been synthesized and structurally characterized. ([mu]-O)[X(bpy)[sub 2]Tc][sub 2]X[sub 2][center dot]bpy, where X = Cl (I) and Br (II), are isomorphic and crystallize in the orthorhombic space group. The compound ([mu]-O)[Cl(phen)[sub 2]Tc]Cl[sub 2][center dot]4H[sub 2]O (III) also crystallized in Pbcn. In each structure, the geometry is distorted octahedral around each Tc, with the equatorial ligands on the opposite metal atoms being staggered relative to one another. The bridging oxygen atom sits on a 2-fold symmetry element which bisects the angle formed by the staggered Tc-X bonds. Infrared Tc-O stretching frequencies are in the range 723-730 cm[sup [minus]1]. Halides are easily dissociated from the phenanthroline complexes and an analog, ([mu]-O)[(OH)(phen)[sub 2]Tc][sub 2](PF[sub 6])[sub 2][center dot]6H[sub 2]O, of a ruthenium water oxidation catalyst has been investigated. Cyclic voltammetry revealed three one-electron couples that are independent of pH over a wide range. At low pH, oxidation of ([mu]-O)[(OH)(phen)[sub 2]Tc][sub 2][sup 2+] by O[sub 2] occurs slowly, but is rapid with HNO[sub 3] or H[sub 2]O[sub 2] to give the (III--IV) mixed-valent complex, which exhibits a low energy (IVCT) band at 959 nm. The comproportionation constant for ([mu]-O)[(OH)(phen)[sub 2]Tc][sub 2][sup 2+] + ([mu]-O)[(OH)(phen)[sub 2]Tc][sub 2][sup 4+] [yields] ([mu]-O)[(OH)(phen)[sub 2] Tc][sub 2][sup 3+] is 3.07 [times] 10[sup 10], consistent with close electronic communication between the two technetium atoms. 33 refs., 4 figs., 7 tabs.
- OSTI ID:
- 6464602
- Journal Information:
- Inorganic Chemistry; (United States), Vol. 32:8; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
TECHNETIUM COMPLEXES
ELECTROCHEMISTRY
BIPYRIDINES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CRYSTAL STRUCTURE
HALIDES
ORTHORHOMBIC LATTICES
OXIDATION
OXYGEN
PHENANTHROLINES
VIBRATIONAL STATES
VOLTAMETRY
AROMATICS
AZAARENES
AZINES
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
CRYSTAL LATTICES
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
KINETICS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIDINES
REACTION KINETICS
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400400* - Electrochemistry
400201 - Chemical & Physicochemical Properties