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Inter-Ring Interactions in Dimers of Magnesium -Cation Radicals Control by Solvent Polarity.

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green solution was vigorously stirred under an oxygen overpressure (ca. 1 bar, 12 h) .
After allowing the mixture to cool to room temperature, phase separation of the
solvent system occurred immediately. The precipitated p-chlorobenzoic acid (6a)
was filtered off and recrystallized from acetonitrile affording a white solid (0.68 g,
4.3 mmol, 87% yield, mp 240-243°C). The green perfluorinated phase containing
the catalyst was separated from toluene and can be used for further experiments.
Preparation of cyclooctene oxide (11 a). A 25 mL flask was charged with a solution
of the ruthenium catalyst 4b (640 mg, 0.25 mmol, 5 moi%) in l-bromoperfluorooctane (2.5 mL) and a solution ofcyclooctene (550 mg, 5 mmol) and isobutyraldehyde (720 mg, 10 mmol) in toluene The biphasic system was warmed to SO "C
affording a single phase and was stirred at that temperature for 5 h under an oxygen
atmosphere (oxygen balloon). The reaction mixture was cooled to O T , and the
phases separated. The brown perfluorinated phase containlng the catalyst was separated and can be reused for further experiments. The organic phase was washed
with 2Maqueous NaOH in order to remove the acid formed as by-product. The
toluene was evaporated and the product was purified by flash chromatography on
silica gel (eluent: hexanesjfBuOMe 10: 1) yielding cyclooctene oxide (11 a) (517 mg,
4.1 mmol, 82%).
Inter-Ring Interactions in Dimers of Magnesium
n-Cation Radicals: Control by
Solvent Polarity**
Kristin E. Brancato-Buentello and W. Robert Scheidt*
An important property of metalloporphyrins is the facile oxidation of the macrocyclic ligand to yield x-cation radicals,
which are important in both biological oxidation chemistry and
photosynthesis. Such species have been known in solution for
almost three decades." 21 Temperature-dependent electronic
spectra indicate that sterically unhindered x-cation radicals
dimerize.12.31 Fajer et a1.I2]also noted the importance of solvent
for changes in the spectra of [Mg(oep')]+ (H,oep = octaethylporphyrin) in CH,Cl, and MeOH. Fuhrhop et al.r31showed
that formation of the [Zn(oep')] radical dimer was stabilized
by solvents of increasing polarity. We have been concerned with
the characterization of metalloporphyrin x-cation radicals, in
particular their inter-ring and spin-spin interactions. In 1989
we reported the structure of the first sterically nonbulky derivative of a n-cation radical, [{Zn(0H,)(0ep')},]~+, which forms a
strongly coupled, virtually eclipsed cofacial dimer with an interplanar porphyrin-ring spacing of 3.31 A.141The dimers show an
unprecedented complete overlap of the two rr-cation radical
rings in the solid state, which was subsequently found in eight
other derivatives.[s1
[Mg(oep')]ClO, is unusual in that it displays relatively high
solubility in toluene/CH,Cl, (4/1). We were thus able to prepare
X-ray quality single crystals of [Mg(oep')]ClO, derivatives from
two solvent systems (Scheme 1). Both 1[*]and 2 are dimeric in
Received: January 7, 1997
Revised version: March 24, 1997 [Z9973IE]
German version: Angew. Chem. 1997, 109, 1605-1607
Keywords: epoxidations
oxidations ruthenium
- fluorine - homogeneous catalysis -
[l] J. G. Riess, M. Le Blanc, Pure Appl. Chem. 1982,54, 2383; J. G. Riess, New. J
Chem. 1995, 19, 893; V. W
. Sadtler, M. P. Krafft, J. G. Riess, Angew. Chem.
1996,108,2106; Angew. Chem. In!. Ed. Engl. 1996,35,1976.
[2] C. M. Sharts, H. R. Reese, J Fluorine Chem. 1978, 11, 637 and references
[3] I. T Horvath, J. Rabai, Science 1994, 266, 72; US-A 5463082, 1995; I. T.
Horviith in Applied Homogeneous Catalysis with Organometnllic Compounds,
(Eds.: B. Cornils, W. Herrmann), VCH, 1996, 601.
141 For recent applications of perfluorinated solvents for the performance of organic reactions see: S . M. Pereira, G. P. Savage, G. W. Simpson, Synth. Commun. 1995, 25, 1023; R. P. Hughes, H. A. Trujillo, Organometnll~cs1996, 15,
286; D. P. Curran, S . Hadida, .
Am. Chem. SOC.1996, f18,2531; D. P. Curran,
M. Hoshino, 1 Org. Chem. 1996.61, 6480.
[S] I. Klement, P. Knochel, Synlett 1995, 1113.
[6] 1. Klement, P. Knochel, Synletf 1996, 1004.
[7] C. Massyn, R. Pastor, A. Cambon, Bull. SOC.Chim. Fr. 1974, 5 , 975; A. E.
Pedler, R. C. Smith, J. C. Tatlow, J . Fluorine Chem. 1971, I, 433.
[8] Aromatic aldehydes bearing electron-withdrawing groups are not readily oxidized by oxygen in the absence of a metal catalyst (see Scheme 4).
[9] T. Yamada, T. Takai, 0. Rhode, T. Mukaiyama Chem. Lett. 1991, 1; T. Yamada, 0 . Rhode, T, Takai, T. Mukaiyama &id. 1991,s.
[lo] The ruthenium catalyst could be recovered in over 95% (by weight) from the
fluorous phase after several reaction cycles.
[ll] A slow autoxidation was found to occur within 60 h under the reaction conditions in the absence of the ruthenium catalyst.
[12] For a recent Mn-catalyzed epoxidation using a perfluorinated porphyrin ligand see: G. Pozzi, S . Banfi, A. Manfredi, F. Montanari, S . Quici, Tetrahedron
1996.52, 11879.
F r g f * P ' ) ( H o E t ) l m g ( ~ P . ) ~ ~ ~ ~ ~ l~g(oep')(oclo3)]2
the solid state, but their inter-ring interactions are dramatically
different.[g1The structures, along with concentration-dependent
electronic spectra, shed light on the effects of solvent (polarity)
on the formation of radical-cation dimers.
Side and plan views of one of the identical dimeric units of 1
and that of 2 are presented in Figures 1 and 2. The x-x interaction between the rings is apparent. The two porphyrin rings of
the cofacial dimer of 1 are directly above each other with no
lateral shift between them. This is true for both dimeric units of
1, even though there is no required crystallographic symmetry.
0 VCH Verlagsgese~lschaftmbH. D-69451 Weinheim, 1997
Scheme 1. Formation of dimers ofn-cation radicals: a) oxidation with thianthrenium perchlorate [6] (1 :1.05) in CHZCI,;crystallization from b) CH,CI,/CHCI, (Sjl)
and hexane or c) toluene/CH,C1, (4/1) and hexane. Dried solvents and flame-dried
glassware must be used throughout to avoid acid-catalyzed demetalation [7].
Prof. W. R. Scheidt, K. E. Brancato-Buentello
Department of Chemistry and Biochemistry
University of Notre Dame
Notre Dame, IN 46556 (USA)
Fax: Int. code +(219)631-4044
e-mail: w.r.scheidt.1@,
This work was supported by the U. S . National Institutes of Health (GM38401). K. E. B. thanks the J. Peter Grace Foundation for a doctoral fellowship.
0570-0833/97/3613-1456$17.50+ .SO/O
Angew. Chem. Inr. Ed. Engl. 1997,36, N o . 13/14
Figure 1. Spacefilling diagrams showing side-on views of dimers 1 (top) and 2
(bottom), and the substantial differences in core overlaps. The interplanar spacing
in 1 is 3.21 A, and the lateral shift effectively 0 A. In 2 the interplanar spacing is
3.46 A, and the lateral shift 6.27 A.
Figure 2. Plan views of the crystal structures of 1 (left) and 2 (right)
The strong interaction is consistent with a lateral shift of about
0 8,and is a feature of all previously characterized dimeric octaethylporphyrin x-cation radicals,[51 all of which were crystallized from polar solvents. The orientation of the ethyl groups in
radical 1, which all point outwards from the center, is also a
characteristic feature.
The two rings of radical 2 show an apparently weaker interaction with a large lateral shift of 6.27 8,. Consistent with this,
each porphyrin has four ethyl groups pointing “up” and four
pointing “down” in an orientation that minimizes the inter-ring
ethyl-ethyl interactions. Scheidt and Lee[”] surveyed the interring geometry for all structurally characterized neutral porphyrin dimers with sterically unhindered peripheral substituents. They noted that the observed lateral shifts tend to
Angew. Chem.In[. Ed. Engl. 1997, 36, No. 13/14
cluster around specific values rather than displaying a continuous distribution. The lateral shift of 2 is in the range observed
for the group Scheidt and Lee classified as “weak”, whereas the
lateral shift of about 0 8,for 1 is much smaller than that for the
group they classified as “strong” (lateral shifts of 1.5 8,). However, the lateral shifts in l are similar to those seen in a number
of other [(M(oep’>},]’+ dimer~.‘~]
All other structural features of 1 and 2 are consistent with
significant differences in the inter-ring interactions in the two
derivatives. The twist angle of 28.3” in 1 leads to a number of
close inter-ring atomic contacts in the inner 16-membered porphyrin ring. The closest inter-ring contacts are between cc-C
atoms and between a-C atoms and methine C atoms. The perpendicular displacements of each atom from the 24-atom mean
planes of 1 are small. Interestingly, the deviations are such that
the close interatomic separations are slightly smaller than they
would be if the cores were precisely planar. The two rings interlock like puzzle pieces to allow more intimate interactions. The
other independent dimer in 1 shows exactly the same phenomenon with a twist angle of 28.2” and similar core conformational features. Edge-over-edge overlap in 2 is small, and the
two cores, each with modest C,, doming, also dome away from
each other. Both features are consistent with a weak inter-ring
An alternating long-short bond-length pattern is observed in
the inner 16-membered rings of 1. The same pattern is evident
in each of the four independent rings (Scheme 2).This unusual
pattern was first observed in [(Zn(0H,)(0ep’)},]’~[~~
and has
subsequently been seen in a number of other dimers of x-cation
The basis for this unusual phenomenon is not
certain but appears to be associated with strongly overlapping
x-cation rings. Bond lengths in the weaker dimer 2 show the
normal porphyrin delocalization pattern.
Differences in the inter-ring interactions of 1 and 2 are also
reflected in the geometry of the coordination groups. The axial
M g - 0 distances (d= 2.039(15) 8, and 2.046(4) A, respectively)
fall well within the broad range seen in other five-coordinate Mg
derivatives (Mg-0 2.012-2.078 A). The mean Mg-N, bond
length in 1 is 2.073(2) A, slightly shorter than that found in other
five-coordinate Mg porphyrins (2.083-2.096 8,)“31but within
the limits observed for six-coordinate Mg porphyrins (2.068 2.078 8,).[141 The mean Mg-N, bond length of 2.079(3) 8, in 2
is slightly longer. A larger difference is found in the out-of-plane
displacement of the metal. For 1 the average of 0.34(4)A is
somewhat low for five-coordinate Mg porphyrin (0.390.52 A),[”] whereas the 0.50 8,displacement in 2 lies within this
range. The shorter-than-normal Mg-N, bond lengths and the
smaller Mg-atom displacement of 1 are the result of the very
tight face-to-face interaction:’
whereas the weaker x-x interaction in 2 leads to the normal geometry of the five-coordinate
Mg center in the porphyrin.
The dramatically different solid-state structures of 1 and 2 are
reflected in significant differences in the electronic spectra of
[Mg(oep’)]+ in CH,Cl, and toluene/CH,Cl, (4/1). At high concentration a broad, concentration-dependent, near-IR band is
seen in both CH,CI, (954 nm) and toluene/CH,Cl, (ca.
912 nm). These bands are similar to that arising from dimerization.”] Most important are the striking solvent- and concentration-dependent features in the UV/Vis region. The spectra generally show the normal features for formation of n-cation
radicals“ - 3. ‘’I: weaker, blue-shifted, broadened Soret bands
and red-shifted, substantially broadened visible (a and 8) bands
along with the appearance of a new band in the visible region at
about 1 = 660 nm, which is characteristic of the magnesium
x-cation derivative.“ ’I
VCH Verlagsgesellschafi mbH, 0-69451 Weinheim, 1997
0370-0833/97/3613-1457$ 1 7 . 5 0 + SOjO
2 106.5
/ 6
2 106.5
Figure 3. Electronic spectra of [Mg(oep')]+ in a) CH,CI, and b) toluene/CH,CI,.
Concentrations in both solvent systems are (top to bottom) 3.00 x 1 0 - 4 ~ ,
2 . 2 5 ~ 1 0 - ~1 ~. 5, 0 ~ 1 0 - 7~ .~5, 0 ~ 1 0 - 3~ .~7 , 5 ~ 1 0 - and
~ ~ 1, . 8 8 ~ 1 0 - The
lowest concentration in a) is 9.38 x
Scheme 2. Diagram of the formal porphinato cores in 1 (top) and 2 (bottom) with
averaged values of bond lengths and angles. For I these averages are taken over the
four independent rings. The values of the averaged bond distances for the inner
16-membered rings are displayed four times to illustrate the alternating bond pattern; all other averaged values are displayed only once. Also displayed are the
perpendicular atomic displacements, in units of 0.01 A, of each atom from the
24-atom mean plane of the core. Positive values of displacement are toward the
center of the other ring. One of the four independent rings is shown for 1. Estimated
standard deviations for individual C-C or C-N bonds are 0.008 A for 1 and
0.007 A for 2, and 0.6" and 0.5" for their angles, respectively.
Figure 3a shows the general concentration-dependent spectral changes in CH,Cl, in the Soret region. At the lowest concentration shown there are bands at 394 and 408 nm; the latter
is more prominent at still lower concentrations. The intensity of
the band at 394 nm increases monotonically with increasing
concentration at the expense of the band at 408 nm. Other blueshifted features (shoulders at 322,355, and 379 nm) also become
more prominent. Figure 3b shows the concentration-dependent
spectral changes that occur in toluene/CH,Cl, (4/1). Again
there is a 410 nm Soret band, whose relative intensity decreases
in favor of a band at 397 nm , accompanied by other blue-shifted shoulders. Even at the highest concentrations the blue-shifted
Soret band and other components are not as completely developed as in CH,Cl,. The blue-shifted band envelopes exhibit
strong similarities in the shapes and intensities of the shoulders.
However, the concentration dependence is more complex in
toluene/CH,Cl,. The ratio of intensities of the bands at 397 and
0 VCH VerlagsgeJellschaft mbH, 0-69451 Weinheim, 1997
410 nm first increases, then decreases, and finally increase again.
In CH,Cl, the ratio of the bands at 394 and 408 nm increases
The 408/410 nm band at low concentration almost certainly
corresponds to the monomeric [Mg(oep')J species, whereas the
394/397 nm Soret and other strongly blue-shifted features must
correspond to the formation of an aggregated, tightly interacting dimeric species in which the in-plane x and y directions are
distinct.["] The nearly identical blue-shifted features in the two
solvents suggests the presence of similar limiting species. The
intensities clearly indicate differences in relative proportions in
the two solvents: monomeric species are favored in toluene/
CH,Cl, , and the species yielding the blue-shifted spectra in
CH,Cl,. However, the presence of a significant amount of a
third component, for which the intenstiy of the spectral band
increases and then decreases with increasing concentration, is
only seen in toluene/CH,Cl, . Since this (third) species appears
with increasing solute concentration, it is clearly at least dimeric.
We interpret the spectral differences to be the result of differences in dimerization equilibrium constants and in the nature of
the (dimeric) species in the two solvents. The differences for the
two solvent systems are as expected if dimerization is more
strongly favored in polar solvents, as is the case in the zinc
system.13]Although the exact nature of the solution species cannot be deduced solely from the electronic spectra, the data clearly suggest significantly different solution species in the two solvents. The dimeric solid-state structures obtained from the two
solvents suggest possible structures in solution. The species
yielding the strongly blue-shifted spectra could have a structure
Angew. Chem. Int. Ed. Engl. 1997, 36, No. 13/14
similar to 1. whereas the other dimeric species in toluene/
CH,CI, may be associated with a species similar to 2.
We have reported the first solid-state analysis of five-coordinate [Mg(oep')J x-cation radicals. Two distinct dimeric species
have been characterized in which the inter-ring overlap is controlled by crystallization from solvents of different polarity :
high polarity leads to a tightly coupled cofacial dimer, and lower
polarity to a more weakly coupled cofacial dimer. The concentration- and solvent-dependent differences in the UV/Vis spectra parallel the findings in the solid state.
Ferromagnetic Coupling in the
Bis(p-end-on-azido)iron(m) Dinuclear Complex
Anion of [Fe"(bpym),] 2[Fei"(N,) 0] * 2 H 2 0 **
Received: January 14, 1997 [Z9993IE]
German version: Angew Chem. 1997, 109. 1608-1611
Keywords: magnesium . noncovalent interactions
oids * UV/Vis spectroscopy - x-n interactions
[I] J.-H Fuhrhop, D. Mauzerall, J. Am. Chem. Soc. 1969. 91, 4174-4181.
[2] J. Fajer, D. C. Borg, A. Forman, D. Dolphin, R. J. Felton. J. Am. Chem. Soc.
1970,92. 3451 -3459.
[3] J.-H Fuhrhop. P. Wasser, D. Riesner, D. Mauzerall, J. Am. Chem. Soc. 1972,
94. 7996-8001
[4] H. Song. C. A Reed, W R. Scheidt, 1 Am. Chem. Soc. 1989. ill, 6867-6868.
IS] a) H. Song, R D. Orosz, C. A. Reed. W. R. Scheidt, h o g . Chon. 1990, 29.
4274--4282; b) W. R. Scheidt, H . Song, K. J. Haller, M K. Safo, R. D. Orosz,
C. A. Reed, P G. Debrunner, C. E. Schulz, ihid. 1992, 31,939-941 ; c) ibid
1997,36. 406 -412; d ) K. E. Brancato-Buentello. W. R. Scheidt, unpublished
[6] Y. Murata, H. J. Shine. J Org. Chem. 1969, 34, 3368-3372.
[7] W. A. Oertling. A. Salehi. C. K. Chang, G. T. Babcock, J Phys. Chem. 1987.91.
3114- 3116.
181 The EtOH molecule coordinated to Mg in crystals of 1 results from from the
stabilizer in commercial CHCI,. Despite the importance of the EtOH in obtaining crystals, it has minimal effects on the spectra of a solution in CH,CI, at the
small concentrations of rhe crystallization experiment
[9] Compound 1 crystallized from CH,CI,/CHCI, (ca. 5jl) layered with
hexanes, and 2 from toluene:CH,CI, (4/1). A pink-purple crystal of 1
(0.13 x 0.20 x 0.60 mm) and a dark purple crystal of 2 (0 017 x 0.06 x 0.17 mm)
were analyzed on an Enraf-Nonius FAST area-detector diffractometer with a
Mo rotating-anode source (i.= 0.71073 A) by procedures that were described
previously (W. R. Scheidt, I. Turowska-Tyrk. Inorg. Chem. 1994, 33. 1314131X) Crystal data for I : u =12.176(1), h = 21.657(5), c = 29.302(8)A,
/{ = 9Y.94(1) . monoclinic, P2,. V = 7610.9(3) A', 2 = 4 (dimes), pEalid=
1.291 gcm-'. X,,,= 27.06 . Crystal data for 2: a = 10.280(4), h =11.681(3),
c' = 13 939(6) A. 1 = 83.93(2), fl = 83 63(3), ;=78.18(3)'. triclinic. Pi, V =
1622.2(10) A'. 2 = 2, pralcd= 1 344 g ~ m - 20,,,
~ , = 29.73.. All measurements
were made at 124+2 K. Data were corrected for Lorentzian, polarization,
and absorption factors (relative transmission coefficients = 1.00-0.729 for 1
and 1.00-0 5 6 5 for 2). Both structures were solved by direct methods
(SHELXS) [10a] and refined against F' with SHELXL-93 [lob]. All data collected were used. and all porphyrin hydrogen atoms were idealized with the
standard SHELXL-93 methods. 1: R , = 0.0746 for 17417 observed reflections
(Fn?4.00(FJ).irR, = 0 2099 for 24123 total unique data (1884 variables refined) including negative F 2 (residual electron density = 0.76 and
-0.45 e A ~ ' ) 2: R , = 0.1030 for 3993 observed data, wR2 = 0.2912 for 8081
uniquedata (463 variables. residual electrondensity = 0.63 and -0.71 e k ' )
Crystallographic data (excluding structure factors) for the structures reported
in this paper have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-100099. Copies of the data
can be obtained free of charge on application to The Director. CCDC,
12 Union Road. Cambridge CB21EZ, UK (fax: int. code +(1223)336-033;
e-mail: depositp
[lo] a) G M. Sheldrick, Acru Cry,~tallogr.A 1990, 46, 467-473; b) unpublished
[ l l ] W. R. Scheidt. Y J. Lee, Srruc Bonding (Eerhn) 1987, 64, 1-70.
[12] K. E. Brancalo-Buentello, S.-J Kang, W R. Scheidt, J. Am Chem. Soc. 1997.
11Y. 2839-2846
1131 a ) K . M Barkigia, L. D. Spaulding. J Fajer, Inorg. Chem. 1983.22. 349-351,
b) C. C. Ong, V McKee, G A. Rodley, Inorg. Chim. Acta 1986, 123,
L11 - L14; c) V. McKee, G A Rodley, [hid. 1988, 151, 233-236; d ) S . Yang,
R. A. Jacobson. hid. 1991. 190,129-134.
[14] a ) R. Bonnett. M. B. Hursthouse, K. M Abdul Malik, B. Mateen, 1 Chem.
Soc. Prrkin li.ows. 2 1977,2072-2076; b) V. McKee, C. C. Ong. G. A. Rodley,
Inorg. Chum 1984, 23, 4242-4248; c) V. McKee, G. A. Rodley, Inorg. Chim
Aciu 1988. 1i1. 233-236
[15] The effect of E complexation or %-x dimer formation on the out-of-plane
position of the metal atom is that of a weakly interacting sixth ligand [4,16].
[16] M. M. Williamson. C L. Hill, Inorg. Chem. 1987. 26, 4155-4160.
[17] JLH. Fuhrhop. D. Mauzerall, .
Am. Chen?. Soc. 1968, 90,3875-3876.
11x1 M. Gouterman. .I Mol. Spectrosc 1961, 6, 138-163.
Angen.. Chmi. 1n1. Ed. EngI. 1997, 36. N o . 13/14
Giovanni De Munno,* Teresa Poerio, Guillaume Viau,
Miguel Julve,* and Francesc Lloret
The design of new polynuclear species exhibiting ferromagnetic coupling is one of the major challenges in magnetochemistry.['] Three strategies have been proposed for obtaining these
compounds,[21which make use of the 1) required or 2) accidental orthogonality of the magnetic orbitals and 3) spin-polarization effects. The second case depends on structural parameters
that are difficult to control during synthesis. The di-p-hydroxobridged copper(I1) complexes are the best example for this: Magnetic coupling is ferromagnetic for angles 6 at the hydroxo
bridge of less than 97.5" and antiferromagnetic for 0 larger than
97.5".13]The remarkable ability of the end-on bridging azide ion
to stabilize the triplet state in dinuclear complexes of divalent
transition metal ions of the first r0w[4-73is another example
of accidental orthogonality. The magnitude of the ferromagnet~ ] + 2.4 cmic coupling varies between + 200 ( C U " ) [ ~and
(Mn") .['I
We recently synthesized new honeycomb layered materials of
formula [M,(bpym)(N,),] (M = Mn", Fe", Co": bpym = 2,2'bipyrimidine), which exhibit alternating ferro- (through double
end-on azido) and antiferromagnetic (through bis(che1ating)
bpym) interactions.'8. 1' In our attempts to synthesize the iron(I1)
derivative 2, single crystals of 1 were obtained after partial oxi-
lFe,(b~~m)W,),l 2
dation by atmospheric oxygen. Complex 1 was characterized by
IR spectroscopy, variable-temperature magnetic measurements,
and X-ray structural analysis.
The crystal structure of 1 consists of centrosymmetric double
end-on azido-bridged iron(1xr) dinuclear anions with monodentate azide groups as terminal ligands (Figure 1, top), mononuclear tris(2,2'-bipyrimidine)iron(ii) cations (Figure 1, bottom),
and water molecules.
Each iron atom in the anion has a distorted octahedral coordination sphere. The metal to bridging azide bond lengths (av
are significantly longer than those involving the
metal center and the terminal azide groups (av 2.031(5) A), as
expected. The latter value compares well with that of 2.023(8) 8,
in the mononuclear iron(I1r) complex (Et,N)[Fe{ HB(3,5Me,pz),}(N,),][' O1 (HB(3,5-Me2pz), = hydrotris(3,5-dimethylI-pyrazo1yl)borate) but is somewhat longer than the Fe-N(axin the porphyrin iron(II1)
ial azide) bond length (1.925(7)
complex [Fe(TPP)(N,)(py)][' 'I (TPP = tetraphenylporphirinate). The occurrence of high-spin (1 and the pyrazolylborate
Prof. G . De Munno, T. Poerio
Dipartimento di Chimica
Universita degli Studi della Calabria
1.87030 Arcavacata di Rende. Cosenza (Italy)
Fax: Int code +(984)492044
Prof. M. Julve. Dr. G. Viau, Dr. F. Lloret
Departament de Quimica lnorganica
Facultat de Quimica de la Universitat de Valencia
Dr. Moliner 50, E-46100 Burjassot, Valencia (Spain)
Fax: Int. code +(6)386-4322
This work was supported by the Spanish Direccion General de Investigacion
Cientifica y Tknica (DGICYT) (Project PBY4-1002) and the Italian Minister0
dell'universita el della Ricerca Scientifica e Tecnologica G V. thanks the
Spanish Ministery of Education and Science for a postdoctoral fellowship.
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interactions, dimer, solvents, magnesium, ring, intel, radical, cation, polarity, control
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