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Structures and spectroelectrochemistry (UV-vis, IR, EPR) of complexes [(OC)3ClRe]n(abpy), n = 1, 2; abpy = 2,2'-azobispyridine

, , , and . Journal of Organometallic Chemistry, 604 (2): 267--272 (2000)
DOI: 10.1016/S0022-328X(00)00282-5

Abstract

(OC)3ClRe(abpy) (1) and [(OC)3ClRe]2(abpy) (2) with abpy = 2,2'-azobispyridine were structurally characterized and studied by spectroelectrochem. in the UV-visible and in the IR carbonyl stretching region. 1 Exhibits a s-cis/E/s-trans configurated abpy ligand with metal coordination to one pyridyl and one azo function and one nonbonding Re-N interaction at 3.293 \AA to the 2nd pyridyl N atom. The dinuclear 2 with two azoimine-coordinated metal centers is distinguished by the trans arrangement of the chloride ligands with respect to the Re2(m-abpy) plane, the Re-Re distance is 5.033(7) \AA. The azo bond lengths at 1.272(9) (1) and 1.304(10) A (2) indicate substantial p back donation from the Re(I) centers into the p*(abpy) orbital. Spectroelectrochem. reveals the successive occupation of the p*(abpy) orbital by electrons; metal-to-ligand charge transfer features are shifted to higher energies and carbonyl stretching bands to lower wavenumbers. The EPR spectra of both radical anion intermediates 1$\surd$- and 2$\surd$- are dominated by very similar 185,187Re hyperfine splitting, ruling out a mixed-valent formulation. The 2nd electron uptake is followed by the rapid loss of one chloride, leading to an unsym. species in the dinuclear system. [on SciFinder(R)]

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