Structural and Electron Self-Exchange Rate Variations in Isomeric (Hexaamine)cobalt(III/II) Complexes

• Published in: Inorganic chemistry Vol. 36; no. 11; pp. 2420 - 2425
• Main Authors: Bernhardt, Paul V, Jones, Lathe A, Sharpe, Philip C
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.05.1997
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic961345e

The syntheses and characterisation of the new macrocyclic hexaamine trans-(5(S),7(S),12(R),14(R)-tetramethyl)-1,4,8,11-tetraazacyclotetradecane-6,13-diamine (L6) and its CoIII complex are reported. The X-ray crystal structural analyses of [CoL6]Cl2(ClO4) [monoclinic, space group C2/c, a = 16.468(3) Å, b = 9.7156(7) Å, c = 15.070(3) Å, β = 119.431(8)°, Z = 4] and the closely related cis-diamino-substituted macrocyclic complex [CoL2](ClO4)3· 2H2O (L2 = cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) [orthorhombic, space group Pna21, a = 16.8220(8) Å, b = 10.416(2) Å, c = 14.219(3) Å, Z = 4] reveal significant variations in the observed Co−N bond lengths and coordination geometries, which may be attributed to the trans or cis disposition of the pendent primary amines. The CoIII/II self-exchange electron transfer rate constants for these and other closely related hexaamines have been determined, and variations of some 2 orders of magnitude are found between pairs of trans and cis isomeric CoIII complexes.