Catecholato complexes

C. Milsmann, A. Levina, H. H. Harris, G. J. Foran, P. Turner, and P. A. Lay, Charge distribution in chromium and vanadium catecholato complexes X-ray absorption spectroscopic and computational studies, Inorg. Chem., 45 (2006) 4743 -754. 

Interestingly, a homoleptic 2-mercapto phenolate complex c-[V(mcp)3] can be prepared from VO(acac)2 (as can the catecholato analog) by displacement of the acac and 0x0 ligands [54]. Similar to the catecholato complex, the structure is described as octahedral distorted toward trigonal prismatic. The redox features of this compound appear at values more negative than its catecholato analog. The Nernstian V(I V/V)... 

A few ionic bis-catecholato N-coordinated complexes 177-181 have been reported192 205 207. Crystallographic studies of 177, 180 and 181 showed all three to have a near-octahedral geometry, with Si—O bond lengths very similar to those in the tris-catecholato complexes, and typical Si—N dative bond lengths of 2.157, 2.085 and 2.173 A, respectively. The 29Si chemical shifts for 177-181, which are in line with hexacoordination, are listed in Table 22. 

Catecholato complexes of the type trans-[0s(0)2(Rcat)2]2 (Rcat = catechol, 4-methylcatechol, 4-tert-butylcatechol, 4-nitrocatechol) are made from 0s04 and the catechol in alkali or from the catechol and trans-K2[0s(0)2(0H)4]. The pyridine complexes trans-[0s(0)2 (Rcat)(py)2] were obtained from 0s04, pyridine, and the catechol (Rcat = cat, 4-Me-cat) [va9(0s02), -820 cm 1 vs(0s02), —860 cm 1] (255). 

The crystal structure of this isostructural series of catechol complexes consists of discrete [M(catechol) 4 ] dodecahedra, a hydrogen bonded network of 21 waters of crystallization and sodium ions, each of which is bonded to two catecholate oxygens and four water oxygens. Of the possible eight coordinate poly-hedra, only the cube and the dodecahedron allow the presence of the crystallographic 4 axis on which the metal ion sits. As depicted in Figure 5 and verified by the shape parameters in Table IV, the tetrakis(catecholato) complexes nearly display the ideal D2d molecular symmetry of the mmmm isomer of the trigonalfaced dodecahedron. 

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