Wydział Chemii

Stanisław Wołowiec

Lechosław Latos-Grażyński

1994

Inorganic Chemistry

33

3576-3586

10.1021/ic00094a022

Naukowa

Angielski

Artykuł

The coordination of cyanide by diiron(III) diporphyrins in chloroform has been studied by NMR and 2H NMR
spectroscopy in order to determine the reaction pathway and intermediates. The diiron(III) diporphyrin of general
formula XFeinTTPO(CH2)„OTTPFeinX (X = CP, B r, I-; TTPO = 5-(o-(m-,/?-)-hydroxy)-10,15,20-tritolylporphyrin
dianion) has been synthesized. Two TTPO units are linked via diether moiety ( = 2 or 3) through ortho-, meta-,
or para-positions of meso phenyls. The cyanide salts tetrabutylammonium cyanide [TBA] [CN] and bis-
(triphenylphosphine)nitrogen(l+) cyanide [BPN][CN] have been used in NMR titrations. The formation of a
high-spin, monocyano species has been established in the first reaction step for all systems under investigation. The
pyrrole resonances appear at characteristic position at 70 ppm (293 K). The electronic structures of monocyano
iron(III) complexes and of high-spin, five-coordinate halide diiron(III) diporphyrins are similar. The monocyano
species are converted into low-spin μ-cy ano-bridged diiron(III) complexes of the intra- or intermolecular structure
as determined by diporphyrin geometry. Two different types of μ-cyano bridged species have been detected by
and 2H NMR and IR spectroscopy. Reaction of diiron(III) diporphyrin and cyanide in excess results in the formation
of low-spin [(CN)2FeinTTPO(CH2)„OTTPFem(CN)2]2 45"complexes. The NMR results indicate that the effective
Cs symmetry of the diporphyrin subunits is retained in the diiron(III) diporphyrins. The paramagnetic shifts of
tricyano and tetracyano species are in a typical range for low-spin iron(III) porphyrins. The magnetic interaction
between two paramagnetic centers of {[(CN)FemTTPO(CH2)„OTTPFeni(CN)](M-CN)}- is small as reflected by
paramagnetic shift of pyrrole resonances. The characteristic connectivity patterns have been determined for pyrrole
resonances of low-spin iron(III) diporphyrins by means of 2D COSY and NOESY 1H NMR.

https://doi.org/10.1021/ic00094a022

https://www.acs.org/content/acs/en.html