Schuldig gesprochen – ein Beweis für die “Nicht‐Unschuld” des Cyanidliganden

Abstract

Über drei Jahrhunderte nach der Erzeugung von CN− in der ersten synthetischen Koordinationsverbindung wurde nun das nicht‐unschuldige Redox‐Verhalten des Cyanidliganden in M3[Co(CN)3] (M=Ba oder Sr) eindeutig belegt. Das 18‐Valenzelektronen‐Komplexion [Co(CN)3]6− besteht laut strukturellen und spektroskopischen Untersuchungen aus Co−I mit abgeschlossener d‐Schale und drei teilreduzierten Cyanid‐Liganden mit der Ladung −5/3.

Synthesis and Crystal Structure of the Electron‐Rich Cyano‐Rhodate Ba3[Rh(CN)3]

“…176) with a = 9.23266(7) Å, c = 5.81612(6) Å at 293(1) K (Table 1 and Table 2). The rhodium compound is isostructural to Ba 3 [Co(CN) 3 ] [4] and Ba 3 [Ir(CN) 3 ]. [5] The unit cell [5] In the series of the isoelectronic species carbon monoxide (CO), cyanide (CN -), and acetylide (C 2 2-) clear bonding trends are obvious when comparing structural and vibrational properties, although a triple bond between both atoms is assumed in all cases.…”

“…Ba 3 [Rh(CN) 3 ] crystallizes in the hexagonal space group P6 3 /m (no. 176) with a = 9.23266(7) Å, c = 5.81612(6) Å at 293(1) K (Table 1 and Table 2).…”

“…The formal description of the complex anions as cyano-metalates would result in oxidation state -III for the transition metal atoms. However, XPS and XANES spectra as well as quantum chemical calculations on Ba 3 [Co(CN) 3 ] indicated s 0 d 10 closed shell configuration for the cobalt atom, and the reduction of the cyano ligands. The complex ion is best described as [Co -(CN 1.67-) 3 ], which can be understood in terms of a mesomeric stabilization [Co -(CN -) 2 (CN 3-)].…”

“…However, XPS and XANES spectra as well as quantum chemical calculations on Ba 3 [Co(CN) 3 ] indicated s 0 d 10 closed shell configuration for the cobalt atom, and the reduction of the cyano ligands. The complex ion is best described as [Co -(CN 1.67-) 3 ], which can be understood in terms of a mesomeric stabilization [Co -(CN -) 2 (CN 3-)]. [4] Obviously, the cyano CN ligands have lost their "innocence" by electron uptake.…”

“…[1][2][3] In recent years, extremely electron-rich cyano compounds, such as Ba 3 [Co(CN) 3 ] [3,4] and Ba 3 [Ir(CN) 3 ], [5] have been reported. The formal description of the complex anions as cyano-metalates would result in oxidation state -III for the transition metal atoms.…”