Ra. Reynolds et al., KINETIC LABILITY, STRUCTURAL DIVERSITY, AND OXIDATION REACTIONS OF NEW OLIGOMERIC, ANIONIC CARBOXYLATE-PYRIDINE COMPLEXES, Inorganic chemistry, 37(6), 1998, pp. 1232-1241
The dimeric [M-2(OAc)(5)(py)(2) mu-(OH2)]Et4N complexes, I (M = Mn, Fe
, Co), have been isolated from pyridine solutions of M-II(OAc)(2) . xH
(2)O and Et4N(OAc). 4H(2)O. The X-ray structures of I (M = Mn, Fe, Co)
have been determined and show the metal ions asymmetrically bridged b
y two acetate ligands and a water molecule. One of the metal ions is b
ound by a pyridine ligand and two monodentate acetate ligands that are
hydrogen bonded to the bridging water molecule. The second metal ion
is bound to a bidentate acetate ligand and a pyridine ligand. Recrysta
llization of I from acetonitrile leads to the reorganization of I and
isolation of the M-3(OAc)(8)(Et4N)(2) complexes, II (M = Mn, Fe, Co).
The X-ray structure of II (M = Mn, Co) has been determined and shows t
he three metal ions connected by four bridging acetate ligands in a mu
(1), mu(2) mode and two acetate ligands in the mu(1),eta(1) mode, with
a bidentate acetate ligand on each of the external metal ions complet
ing the distorted octahedral geometry. Air oxidation of I-Fe in propio
nitrile leads to the formation of the mixed-valence [Fe-3 mu(3)(O)(OAc
)(7)(OH2)]Et4N (III). The X-ray structure of III has been determined a
nd resembles the core of the basic acetate complexes; however, it has
five bridging acetate ligands. The Mossbauer spectrum of III shows two
quadrupole doublets in a 1:2 ratio with delta(Fe) = 1.29(1) and 0.48
mm/s; Delta E-q = 1.89 and 0.71 mm/s. The oxidation of I-Pe by H2O2/O-
2 in pyridine solution in the presence of Cl- ligands affords Fe-4 mu(
3)-(O)(2)(OAc)(6)(py)(4)Cl-2 (IV). The X-ray structure of TV shows a r
hombic {Fe-4(III)(mu(3)-O)(2)} core previously found in iron and manga
nese chemistry. The reaction of ferrocenium ion with I-Fe under basic
conditions in dichloromethane solution led to the formation of the fam
iliar mixed-valence Fe-3 mu(3)-(O)(OAc)(6)(py)(3) complex (V) with the
basic acetate structure. Complexes I-Fe, II-Fe, III, and IV catalyze
the reaction of O-2 With adamantane under GiF conditions to give adama
ntanols and adamantanone. The similarity of the results in comparison
to similar studies previously reported for iron/carboxylate complexes
are noted and discussed.