K. Meyer et al., NITRIDOMANGANESE(V) AND NITRIDOMANGANESE(VI) COMPLEXES CONTAINING MACROCYCLIC AMINE LIGANDS, Journal of the American Chemical Society, 120(29), 1998, pp. 7260-7270
Photolysis of trans-[(cyclam)Mn-III(N-3)(2)](ClO4) (1) in methanol at
-35 degrees C with similar to 350 nm light produces blue [{trans-[(cyc
lam)Mn-V(N)]}(2)(mu-N-3)](ClO4)(3). 3H(2)O (2) and dinitrogen (cyclam
= 1,4,8,11-tetraazacyclotetradecane). A series of six-coordinate compl
exes trans-[(cyclam)Mn-V(N)Y](n+), where Y represents Cl, n = 1 (3); C
H3CN, n = 2 (4); ClO4-, n = 1 (5); CF3CO2-, n = 1 (6), was also synthe
sized. From a methanol solution of 2 and addition of NaCN the species
cis-[(cyclam)Mn-V(N)(CN)](ClO4) (7) was obtained. Photolysis of [LMnII
I(N-3)(3)], where L represents the macrocycle 1,4,7-trimethyl-1,4,7-tr
iazacyclononane, in CH3CN at 20 degrees C with 253.7 nm light produces
colorless crystals of [{LMnII(N-3)}(2)(mu-N-3)(2)] (8) (photoreductio
n), whereas photolysis with 350 nm light at -35 degrees C gives the bl
ue photooxidation product [LMnV(N)(N-3)(2)] (9). Complexes 1-7 were ch
aracterized by X-ray crystallography. Compounds 2-7 contain the nitrid
omanganese(V) unit (Mn=N 1.51-1.54 Angstrom). All nitridomanganese(V)
complexes display significant temperature-independent paramagnetism in
dicative of a low-spin d(2) electron configuration. In the electronic
spectra four d-d transitions have been identified for the first time w
hich were unambiguously assigned by single crystal polarized UV/vis/NI
R and magnetic circular dichroism (MCD) spectroscopy. The spectra were
satisfactorily analyzed in the frame of ligand-field theory (angular
overlap method). N-15 NMR spectroscopy revealed an enormous deshieldin
g of the nitrido group in 4, 6, and 7 (delta = 693-699 ppm referenced
to CH3NO2 at 0 ppm). Electrochemically, complex 4 undergoes a reversib
le one-electron oxidation generating a stable nitridomanganese(VI) spe
cies (d(1)) which has been characterized by UV-Vis and EPR spectroscop
y.