The reaction between the
[Mn(BS)(H2O)]+ monomeric and
[Mn2(μ-BS)2(H2O)2]2+
dimeric cations and
[Fe(CN)6]3- gave rise to
cation−anion interaction via the formation of
[FeC⋮NMn] bridges. Depending on the
nature of the Schiff base and regardless of the stoichiometry used,
either the trimeric anion
[{Mn(BS)}2{Fe(CN)6}]-
(BS = 3-MeOsalen, 6; 5-Clsalen, 7; 5-Brsalen,
8; salcy, 10) or the pentameric cation
[{Mn(BS)}4{Fe(CN)6}]+
(BS
= saltmen, 9) is formed, which has been assembled by the
K+ cation or the ClO4
- anion,
respectively. The X-ray
analysis of 6 revealed a two-dimensional network layer
structure. The magnetic measurements showed its
metamagnetic behavior, where the ferromagnetic interaction operates
within each layer and the antiferromagnetic
interaction operates between the layers. The Neel temperature,
T
N, is 9.2 K, and the critical field at 2 K is
300 Oe.
The temperature dependent magnetic susceptibilities of
7 and 8 are in agreement with a discrete,
symmetrical, trinuclear
structure Mn(III)Fe(III)Mn(III)
(S
Mn = 2, S
Fe = 1/2,
S
Mn = 2) with a ferromagnetic spin coupling
between the
Mn(III) and Fe(III) ions, a small antiferromagnetic
intertrimer interaction, and a large zero-field splitting of
the
Mn(III) ion. The structure of 9 consists of a
two-dimensional layer containing as the repeating unit a cyclic
dodecamer.
The layers stack along the c axis, and
ClO4
- anions are positioned between the
layers. The magnetic measurements
showed this compound's ferromagnetic behavior. There are, in
fact, two kinds of intralayer magnetic interactions,
the interaction between the Fe(III) and Mn(III) ions bridged
by CN groups and the interaction between two Mn(III)
ions in the dimer [Mn2(saltmen)2], both
being ferromagnetic. The interlayer magnetic interaction is
ferromagnetic.
All of the interactions render to 9 an overall
ferromagnetic behavior.
Co(II)-porphyrin complexes catalyze the reaction of aromatic azides (ArN(3)) with hydrocarbons that contain a benzylic group (ArR(1)R(2)CH) to give the corresponding amines (ArR(1)R(2)C-NHAr). When at least one of the R substituents is hydrogen, the catalytic reaction proceeds further to give the imine ArRC=NAr in good yields. The reaction mechanism has been investigated. The reaction proceeds through a reversible coordination of the arylazide to the Co(II)-porphyrin complex. This unstable adduct can either react with the hydrocarbon in the rate-determining step or decompose by a unimolecular mechanism to afford a putative "nitrene" complex, which reacts with more azide, but not with the hydrocarbon, to afford the byproduct diaryldiazene. The kinetics of the catalytic reaction have been investigated for a range of azides and substituted toluenes. Arylazides with electron-withdrawing substituents react at a faster rate and a good correlation is found between the log(k) and the Taft parameters. On the other hand, an excellent correlation between the logarithm of the rate for substituted toluenes relative to that of toluene and a radical parameter (sigma*JJ) alone was found, with no significant contribution by polar parameters. An explanation has been proposed for this anomalous effect and for the very high isotopic effect (k(H)/k(D)=14) found.
The complex Ru(TPP)(NAr)(2) inserts a nitrene group into allylic and benzylic C-H bonds and is the key intermediate in the ruthenium porphyrin-catalyzed amination of hydrocarbons by aryl azides.
This feature article provides an overview of the application of organic azides for the intermolecular amination of sp(3) and sp(2) C-H bonds. The catalytic activity of several metal complexes was reviewed underlining both synthetic and mechanistic aspects of the C-H amination. The majority of the aminated compounds reported in literature have been collected in this paper to provide a compendium of published procedures. In addition, the discussion of involved mechanisms has been included to assist the reader to envisage the future potential of organic azides in the synthesis of aza-derivatives.
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