Erste strukturelle Charakterisierung eines azoaromatischen Radikalanions, stabilisiert durch Dikupfer(I)-Koordination

Abstract

Stabilisiert durch zweifache Chelatkoordination von {Cu(Ph3P)2}+ ist das Radikalanion von 2,2′‐Azobis(5‐chlorpyrimidin), das im Komplex (siehe Bild) eine N‐N‐Bindungslänge von 1.345(7) Å aufweist – in Übereinstimmung mit einer einfach reduzierten Azofunktion.

Structure, electrochemistry, spectroscopy, and magnetic resonance, including high-field EPR, of {(μ-abpy)[Re(CO)3X]2}o/•−, where abpy=2,2′-azobispyridine and X=F, Cl, Br, I

“…From calculations on {(l-abpy) [Re(CO) 3 Cl] 2 } n [16], the bond length should increase from 1.329 Å for the neutral complex (n = 0) to 1.359 Å for the stable radical anion (n = À1). This has been confirmed experimentally by the example of the abcp complex {(l-abcp)[Cu(PPh 3 ) 2 ] 2 }(PF 6 ), abcp = 2,2 0 -azobis(5-chloropyrimidine), [29] with an azo N-N bond length at 1.345 Å.…”

Multifrequency EPR Study and Density Functional g-Tensor Calculations of Persistent Organorhenium Radical Complexes

“…Herein we report a multifrequency EPR investigation of two stable dinuclear complex anions {(µ-L)[Re(CO) 3 Cl] 2 } •-, L ) 2,2′-azobispyridine (abpy, 3,7 complex 1) and 2,2′-azobis(5chloropyrimidine) (abcp, complex 2). 7,8 These compounds are highly suitable for a detailed experimental and computational study for the following reasons:…”

Multistep redox sequences of azopyridyl (L) bridged reaction centres in stable radical complex ions {(μ-L)[MCl(η5-C5Me5)]2}˙+, M = Rh or Ir: spectroelectrochemistry and high-frequency EPR spectroscopy

“…Cathodic peak potentials a E EC for chloride-dissociative EC steps in coupled dinuclear complexes {(µ-L)MCl(C 5 Me 5 )] 2 } n at Ϫ1.46 V or free abcp at Ϫ1.01 V, 12,16 confirming the substantial metal-to-ligand electron transfer in the ground state of neutral {(µ-L)[M(C 5 Me 5 )] 2 . Supporting this interpretation, the EPR signal reported for mononuclear [(abpy)Rh(C 5 Me 5 )] Ϫ (g 1 = 2.16, g 2 = 2.002, g 3 = 1.945) has shown substantial metal contributions according to the oxidation state description [(abpy ϪII )Rh II (C 5 Me 5 )] Ϫ .…”

“…12 The ability of the abpy ligand to bridge two metal centres at a distance of about 5 Å, 14 the rather small size of its π system, and the low-lying π* orbital 15 make it a very special ligand, suitable for studying metal-metal interactions across an unsaturated molecular bridge. 12 2,2Ј-Azobis(5-chloropyrimidine) was obtained in a similar way through chlorinating oxidative coupling of 2-aminopyrimidine; 16 it was shown to be an even better π acceptor ligand than abpy. 16,17 The compounds studied are the dinuclear {(µ-L)[MCl(η 5 -C 5 -Me 5 )] 2 }(PF 6 ) n , M = Rh or Ir, and L = abpy or abcp, which were initially isolated as stable one-electron reduced (radical) species (n = 1) but could be converted preparatively into the diamagnetic forms (n = 2) for M = Ir through chemical oxidation.…”

“…12 2,2Ј-Azobis(5-chloropyrimidine) was obtained in a similar way through chlorinating oxidative coupling of 2-aminopyrimidine; 16 it was shown to be an even better π acceptor ligand than abpy. 16,17 The compounds studied are the dinuclear {(µ-L)[MCl(η 5 -C 5 -Me 5 )] 2 }(PF 6 ) n , M = Rh or Ir, and L = abpy or abcp, which were initially isolated as stable one-electron reduced (radical) species (n = 1) but could be converted preparatively into the diamagnetic forms (n = 2) for M = Ir through chemical oxidation. Cyclic voltammetry, variable frequency EPR (9.5, 230, 285 GHz) and the spectroelectrochemical (UV/Vis) characterisation of the intermediates will be described, the results obtained shall be compared with those of the previously studied analogues of bpym, 10 bpip and bptz.…”