The chemistry of cobalt acetate.: VIII.: New members of the family of oxo-centred trimers, [Co3(μ3-O)(μ-O2CCH3)5-p(μ-OR)pL5]2+ (R = H, alkyl, L = ligand, p=0-4).: The preparation and characterisation of the trimeric tetrakis(μ-acetato)-(μ-hydroxo)-μ3-oxo-pentakis(pyridine)-tri-cobalt(III) hexafluorophosphate, [Co3(μ3-O)(μ-O2CCH3)4(μ-OH)(C5H5N)5][PF6]2, and the preparation and crystal structure of the trimeric tris(μ-acetato)-(μ-hydroxo)-(μ-methoxo)-μ3-oxo-pentakis(pyridine)-tri-cobalt(III) hexafluorophosphate •methanol•water solvate [Co3(μ3-O)(μ-O2CCH3)3(μ-OH)(μ-OCH3)(C5H5N)5][Pf6]2•CH3OH•0.25H2O

The isolation, characterisation and some reaction chemistry of salts of the new oxo-centred cobalt(III) acetate trimeric dications, [Co-3(mu(3)-O)(mu-O2CCH3)(4)(mu-OH)(C5H5N)(5)](2+) (15), [Co-3(mu(3)-O)(mu-O2CCH3)(3)(mu-OH)(mu-OCH3)(C5H5N)(5)](2+) (16) and [Co-3(mu(3)-O)(mu-O2CCH3)(3)(mu-OCH3)(2)(C5H5N)(5)](2+) (17), and the X-ray crystal structure of (16)[PF6](2).CH3OH.0.25H(2)O (refined to R(F) = 0.0639, R-w(F) 2 0.0569) are reported. The compound (16)[PF6](2).CH3OH.0.25H(2)O crystallises in space group P2(1)/n (No. 14). The oxo-centred trimer has a Co3ON5 core, with the mu(3)-O atom 0.707 Angstrom out of the plane of the approximately isosceles triangle formed by the three near-octahedrally co-ordinated cobalt atoms. The Co...Co distances are 2.778(1), 2.796(1) and 3.326(1) Angstrom, and the CO-(mu(3)-O) distances are 1.8865(4), 1.880(4) and 1.883(4) Angstrom. The existence of an extensive series of compounds in 'cobalt(III) acetate' is discussed, and the trinuclear species shown to have stoichiometries described by [Co-3(mu(3)-O)(OAc)(6-x-n)(OR)(n)(L)(3+y+2x)]((x+1)+) (0 less than or equal to y less than or equal to 3, 0 less than or equal to x less than or equal to (3-y), 0less than or equal ton <(5-x) L=ancillary ligand, e.g. py, MeCN, H2O, solvent). (C) 2003 Elsevier Science Ltd. All rights reserved.