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Octathioporphyrazine Crown Ethers An Octanuclear AgI Complex with Coordination in the meso Pocket.

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[Y] Since the X-ray structural analysis doesn't show any exceptional features.
it
hasn't been depicted, see F. Hampel. H. J. Bestmdnn. H. P. Oechsncr, C.
Egerer-Sieber, Zeir.sdir. / u r Kri.stul/ogrupl~re.in press.
[lo] D. Hellwinkel. W. Lindner. C/imi. Ber. 1976, 1OY. 1497-1505.
' H NMR (400 MHz, [D,] CHCI,. 31 'C. TMS]: b = 1.6 (dd, appears a s t. '4P.H) = I 5 Hr. 3H. (CH,), 1.65 (dd. 'J(P,H) = 1 2 Hz.
&.I(P.H) =1.S Hz, 3 H , PCH,): "C NMR (125 MHz, [D,] CHCI,, 31 ' C .
TMS): j = 0.5 (dd, appears i i b I. 'J(P.C) = ! 19 Hz. 1 C. PCP), 14.5 (dd.
'J(P.C) = 60 Hr. 'JJ(P.C) = 5 Hz. 1 C, Ph,P-CH,). 16.5 (dd. 'J(P.C) = 4.6and
1.S Hz. I C , CCH,); " P N M R (162 MHz, [DJ CHCI,. 31 C. H,PO,):
h = 24.3 (dd. ' J ( P , P ) = 55 and 101 Hz.2 P , PCP).
[12] See F Ramirez. K . Tasaka, N. B. Desai, C. P. Smith. J. A m Chem. ,Yo<. 1968.
YO. 751 -755; D. Hellwinkcl, Tup. Curr. Chrm. 1983. IOY. 1 64.
[13] See H. Schmidbaur. H. Stuhler. W. Bnchner, Chmn. B r x 1973. 106. 123%
1250.
tion by the rneso N atom made a major contribution to the
binding. This is now shown to be the case for the remarkable
peripheral ligation of eight silver(1) ions by an octakis(alky1thio)tetraazaporphyrin containing four crown ether units, in
which both crown ether and nieso-pocket coordination is
exhibited.[41
W d 5 ]and othersr6]have reported on the synthesis and coordination chemistry of crown ether derivatives ("oxa-crowned"
derivatives) of dithiomaleonitrile (for example, I and 2 in
Scheme 2). The mix of soft sulfur and hard oxygen donor atoms
~
Octathioporphyrazine Crown Ethers: An
Octanuclear Ag' Complex with Coordination in
the me.w Pocket**
John W Sibert, Steven J. Lange, Charlotte L. Stern,
A. G. M. Barrett,* and Brian M. Hoffman*
Porphyrazines (tetraazaporphyrins) and porphyrins are related by the isoelectronic replacement of the meso CH unit in the
latter with the meso N atom in the former (Scheme I).['] This
/
NC
\
CN
1, n = O
\
2.n=l
4,M=2H
5, M = Nil'
6, M = CU"
8, M = 2 H
9, M = Nil'
10,M = CU"
Scheme 2. Synthesis of the porphyrazine crown ethers 3--10
porphyrin
tetraazaporphyrin
Scheme 1
replacement influences the binding of a metal ion in the central
cavity.['] However, it has not been widely recognized that the
nieso N atoms' lone-pair electrons. which are in the plane of the
macrocycle and directed away from it. potentially can coordinate to additional metal ions at the macrocycle's periphery. We
recently reported the first structurally characterized example
displaying this behavior, a peripherally metalated porphyrazine
where each nzeso N atom of porphyrazineoctathiolate acts together with its two nearby peripheral S atoms to function as a
tridentate "rneso-pocket" ligand that binds a dialkyltin mole~ u l e . Because
[~~
the metal-binding capabilities of the thiolato
sulfur atoms are strong, it was by no means clear that coordina-
[*I
[**I
Prof. Dr. A. G. M. Barrett
Department of Chemistry
Imperial College of Science. Technology and Medicine
South Kensington. GB-London SW72AY ( U K )
Telefax: Int. code + (!71)59-45805
e-mail: barrett(a ic.ac.uk
Prof: Dr. B. M. Hoffman. Dr. J. W. Sihert. S. J. Lange, C. L. Stern
Department of Chemistry, Northwestern University
Evanston. TL 60208 (USA)
Tclefax: Int. code + (708)491-7713
e-mail: b m h h merctiry.chem.nwii.edu
This work was supported by the National Science Foundation (CHE9408 56 11.
renders these crown ethers particularly well suited for the ligation of heavy metal ions; endocyclic complexes of HgC1,[5a1and
AgI ,[ 5 bl and exocyclic complexes of PdX, (X = CI, Br),[6"1are
known. In addition to being ligands themselves, 1 and 2 are the
direct precursors to oxa-crowned octakis(a1kylthio)tetraazaporphyrins.I4. 'I
The oxa-crowned porphyrazines were synthesized by the Mg"
template cyclization of the appropriate crowned derivative of
dithiomaleonitrile as described (Scheme 2) .[81 Consistent with
the work of Linstead and co-workers for the synthesis of octamethyltetraa~aporphyrin,~~]
we obtain the highest yields for
the preparation of the Mg" porphyrazines 3 and 7 (about 35 X )
using butanol as the reaction medium. van Nostrum et al.
reported yields of 20-22% for a similar synthesis of 3 and 7 in
propanol.['] Treatment of the Mg-porphyrazines with trifluoroacetic acid provided the metal-free porphyrazines 4 and 8. Subsequent reaction with Ni(OAc), or Cu(OAc), in chlorobenzene/
D M F (5/1) quantitatively produced the corresponding centrally
metalated porphyrazines ( 5 9 and 6.10; see Table 1 for the characterization).
Preliminary studies of the binding of Ag', HgCI, , CdCI,, and
Pb" to the periphery of 5 dissolved in chloroform/methanol
(3/1) solutions employed UV/Vis spectroscopy. Reactions with
HgCI, and CdCI, caused the precipitation of compounds that
could not be sufficiently purified. No evidence for complexation
with Pb" was observed. However, the addition of a large excess
of AgBF, led to significant color changes, from blue to greenishblue, that could be
The spectrum of the parent
compound 5 has strong n-n* absorptions at 326 and 672 nm
and an n-n* transition at 485 nm that involves the peripheral S
atoms.["] The color change upon addition of Ag' ions corre-
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Table 1
Ana1)tical (elemental analysis). spectroscopic (UV:Vis, ' H NMR). and mass spectrometric data (HR-FAB-MS) for compounds 4 6. 8 10. and [ I I - X BF,].
~
Corn po 11 iid
c
Elemental analysis
H
[%I
A,,.,,
Inml [bl
[a]
6 [c]
N
6
(45.13) [d]
43.Y4
(44.96) [d]
8
48 20
148.75)
6.05
(6.00)
7.86
(8.13)
356. 504. 643, 716
3.62 (48H. m)
4.01 (I6H. t)
4.31 (16H. t)
1379.367
( 1 379.369)
9
46.3X
(46.85)
5.57
(5.62)
5.84
(5.60)
2.48
(2.57)
7.69
(7.81)
324, 342 (sh). 486. 671
3 61 (48H. m)
3.94 (16H, t)
4.19 (16H. I )
1435.294
( 1435.289)
7.57
(7.78)
3 69
(3.25)
356. 495, 614 (sh), 672
LO
46.21
146.69)
19 36
(19.50) [el
I1
326,485,672
4.21 (16H.
44.X9
(4791)
8.90
(8.78)
7.88
(8.74)
3.54 (32H. m)
3.93 ( t 6 H , t)
3.58 (37H. m)
3.94(16H. t)
[a]
5
4x.14
346. 502. 644. 716
CH,S
5.69
(5.53)
5.1 3
(5.21)
4.62
(5.19)
4
8.90
(9.32)
H1::
CHiO
I)
4.20 ( I 6 H . t)
348.498. 676
I703.280
(1203.264)
1759.186
(1259.184)
1264.182
(1764.178)
1440.275
(1440.283)
333. 605 (sh). 664
[a] Theoretical v;ilties are given in parentheses. [b) Compounds 4-6, 8- 10 in chloroform. [11.8 BF,] in methanol. [c] The chemlcal shifts of the internal i\iH protons for 4
and 8 are 6 = 2.31 and -2.18, respectively. [d] Analysis of the monohydrate. [el The analytical and crystallographic data for the two crystalline Ibrms of[11.8 BF,] are
consistent with ten Ag' ions. of which eight are directly coordinated to the porphyrazme. and four water molecules per molecule.
~
sponded to the disappearance of the transition at 485 nm and
sharpening (but not shifts) in the %-TI* transitions.
The absence of the n--T[* transition indicates that the Ag' ions
coordinate to the peripheral S donor atoms. The small changes
in the n - x* transitions are unlike those observed for the mesocoordinated tin adduct of porphyrazineoctathiolate. In the latter case the Soret band is shifted out of the visible region of the
spectrum, presumably as a result of the stabilization of the a,,
molecular orbital through coordination to the meso N atoms.
Thus, in solution 5 appears to coordinate Ag' ions through the
crown moieties alone without participation of the mem N
atoms.
Slow evaporation in the dark of a chloroform/methanol solution containing 5 and an excess of AgBF, produced complex 1I
1
8+
I -
Fig. 1. X-ray structure of the porphyrazine cation I 1 with all other atomb of the
complex [ 1 1 - 8BFJ removed for clarity.
ll
as blue crystals with a red reflex in two distinct morphologies
(needles and cubes). The analysis of both types of crystals indicates more than eight Ag' ions per porphyrazine. Importantly,
when only eight or fewer equivalents of AgBF, were added to 5,
no crystalline product was obtained.
X-ray diffraction studies on [11.8 BF4][I2,1 3 ' yield the first
structural characterization of a crowned porphyrinic macrocycle incorporating metal ions in the crowns. They disclose a far
more interesting situation than inferred from the behavior in
solution: ;Lcrystal having the needle morphology["] has not
four. but eight Ag' ions coordinated to the periphery of the
porphyrazine (Fig.
Four Ag' ions are coordinated in an
endocyclic fashion by the crown moieties, consistent with the
inferences based on optical spectra of solutions. However, four
additional Ag' ions occupy the meso pockets and undergo tridentate, S-N-S coordination by the peripheral thioether S and
the meso N atoms (the coordination sphere of these Ag' ions is
completed by 0 atoms from solvent). The lack of evidence for
rneso coordination in solution suggests a preference for the ligation of Ag' by the crown moieties of 5.
As shown in Figure 2d, each of the four Ag' ions in the crown
subunit is coordinated by one S atom (average distance
2.5.5(1) A ; range 2.50(1)-2.60(1) A). and all three macrocyclic
0 atoms (average distance 2.52(3) A; range 2.39(3)--2.69(3) A).
In addition there is a weaker interaction with the remaining S
donor atom (average 2.98(1) A; range 2.95(1)-3.04(1) A). The
Ag-S and A g - 0 bond lengths are typical and similar to those
in the related Ag' complexes of macrocycles 1, 2.1sb1and 1,4dithia-7,10,13-trioxacyclopentadecane.['*I Each of the four Ag'
ions in the rmso pockets is coordinated unsymmetrically by the
two S donor atoms (Fig. 2b). The short Ag,,,,,- S bond lengths
average 2.69(1) A (range 2.65(1)-2.74(1) A), whereas the long
Ag,,,,-S
bond lengths average 2.81(1) A (range 2.71(1)-
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-
Keywords: coordination * crown ethers porphyrazines
compounds
*
silver
-
Fig. 2. Coordination geometry about Ag’ions in the crown ether units ( a )and in the
mem pockets (h) of the porphyrazine cation 11. The average bond lengths are given
in angstroms.
2.88(1) A). The Ag-N,,,,
bonds are slightly longer (average
2.40(3) A; range 2.37(3)-2.43(3) A), though similar to those
reported for Ag-N(pyridine) bonds.“ 61
The ability of S-appended porphyrazines to coordinate metal
ions in two distinct binding sites is due to the flexibility of the
C,-S bond. This flexibility can be gauged by examining the
“bite” distance between the two S atoms on each pyrrole unit.
In the tin-capped porphyrazine octathiolate. a purely meso-coordinated complex, the S . . . S distance is 3.74 A. This distance
decreases to 3.25 8, in the nickel-capped porphyrazine octathiolate, a complex exhibiting the classic bidentate “dithiolene” coordination of a Ni” ion by both S atoms on each pyrrole ring.[‘’’
An intermediate value for the S . . . S separation might be expected for 11, because it contains both types of bonding in the same
molecule, and such is the case. The average S . . S distance in 11
is 3.58 A (range 3.57-3.60 A), comparable to that in an octathiomethylporphyrazine (S . . . S = 3.53 A) with no peripherally coordinated metal ions.‘”]
As first seen with the tin-capped porphyrazine octathiolate,
heteroatoms at the fl positions of the pyrrole ring can function
together with the meso N atom to form a tridentate binding
pocket that readily accepts metal ions. This is now found to be
true in both thiolate- and thioether-appended porphyrazines,
thus establishing that porphyrazines should not be viewed simply as modified porphyrins, but as a discrete class of molecules
with its own unique properties. We anticipate that a rich chemistry with meso-pocket coordination will grow from the study of
functionalized porphyrazines.
Experiniencal Procedure
4: A suspet~sionof magnesium turnings (30 mg: 1.23 mmol) in hutanol (8-10 mL)
was heated at reflux for 24 hours with iodine as an initiator. To the resulting
magnesium butoxide suspension was added solid l ( 1 . 0 g: 3.3 mmol). The solution
rapidly turned yellow. then green and. after several minutes. settled at a deep blue
color. The reaction was kept at reflux under a nitrogen atmosphere for 18 h. The
hutanol was then removed under reduced pressure, and the residue taken up in
chloroform and filtered. The filtrate was passed through a silica column ( 5 %
CH,OH in CHCI, as eluent) to afford the Mg-porphyrazine 3. which was used
without further purification. Compound 3 was dissolved in neat trifluoroacetic acid
(10 mL) and stirred at room temperature for 1 h. The solution was poured over ice
and neutraliLed with ammonium hydroxide. The resulting precipitate was filtered
and washed with water and methanol. Column chromatography on silica ( 3 %
CH,OH in CHCI,) produced pure 4 as a blue solid: yield 35-40% (based on 1)
Porphyrazine 8 was prepared from crown ether 2 by an identical procedure.
5 (M = Ni) and 6 (M = Cu): The 21H.23H-porphyrazine 4 (150 mg) and a large
excess ofM(OAc), (M = Ni o r Cu) were added to a mixture OfchlorobenzenelDMF
(511; 10 mL). The reaction was heated to 100°C under a nitrogen atmosphere and
stirred for 18 h. The solvent was then removed under reduced pressure, and the solid
residue washed with methanol and filtered. The product was isolated in nearly
quantitative yield following column’ chromatography on silica (3 % CH,OH in
CHCI,). PorphyrdZiileS 9 and 10 were prepared from 8 by an identical procedure.
11 : To a solution (chloroform/methanol3!1,50 mL) of 5 (40 mg) was added AgBF,
(> 10 equiv). The color of the solution immediately changed from blue to greenishblue. Slow evaporation of the solvent in the dark produced I 1 as blue crystals with
a red sheen.
Received: May 2. 1995 [Z 79521EJ
German version: Atr~yiw.Clrem. 1995. 107. 2173-2176
2022
K‘ V C H Verfugsgese/lschu//m h H , 0-69451 Weinlieim. 1Y95
Plzrlzulor~unini~.r
. Properlies und App/icurions (Eds. : C. C. Leznoff, A. B. P.
Lever), VCH, New York, 1989.
See. for example, J. P. Fitzgerald. B. S. Haggerty, A. L. Rheingold, L. May,
G. A. Brewer. Inorg. Cheni. 1992, 31, 2006.
a) C. S. Velazquez. W. E. Broderick. M. Sabat. A. G . M. Barrett, B. M. Hoffman, J. Am. Chefn. SOC.1990. 112. 7408: b) C . S. Velazquez, G. A. Fox, W. E.
Broderick, K. A. Andersen, 0 . P. Anderson, A. G. M. Barrett. B. M. Hoffman. ihid. 1992. 114. 7416.
Preliminary accounts of this work: a) J. W. Sibert. S. J. Lange, C. Stern, B. M.
Hoffman. A. G. M. Barrett, Ahslr. Pup. Am. Chem. SOC.206rh Nurionu/ Meeting(Chicago. IL) 1993, INOR 60; b)A. G. M. Barrett. presented at the Macrocycles Group Meeting of the Royal Society of Chemistry (UK), University of
Warwick. UK, 1994.
a) J. W. Sihert. S . J. Lange. C . Stern, B. M. Hoffman, A. G. M. Barrett, J. Chem.
Soc. Chenr. Commun. 1994, 1751; h) J. W. Sihert, S. J. Lange, B. M. Hoffman,
D. J. Williams. A. G. M. Barrett. Inorg. Chem. 1995, 34, 2300.
a) H.-J. Holdt. Pure Appl. Chem. 1993, 65. 477: b) H.-J. Holdt. J. Teller. Z.
C%em. 1988. 28. 249.
C. F. van Nostrum, F. B. G. Benneker. N. Veldman. A. L. Spek, A,-J.
~
113, 109.
Schouten. R. J. M . Nolte, Red. Truv. Chim. P u y . s - 5 ~1994,
C. J. Schramm, B. M. Hoffman. Inorg. Clzem. 1980, 19. 383.
M. E. Baguley. H. France. R. P. Linstead, M. Whalley, J Chem. Soc. 1955.
3521
van Nostrum et al. noted changes in the visible spectrum of 7 upon addition of
up to six equivalents of Ag’ ions per porphyrazine. They ascribe the uptake of
more than four equivalents of Ag’ to dimerization caused when the metal ions
are sdndwiched between neighboring porphyrazines 171.
P. Doppelt, S. Huille. New J. Chem. 1990, 14, 607.
Crystal data: triclinic, space group Pi (no. 2). u =15.377(8), b = 17.685(6),
c =19.002(7) A. 3~ =104.94(3), /i= 95.57(4), 7 = 99.71(4)”, V = 4867(8) A’,
Z = 2,
= 2.161 gcm-’. y(Mo,,) = 4.20 cm-’. A blue, platelike crystal
(0.48 x 0.14 x 0.02 mm) was mounted on a n Enraf-Nonius CAD-4 diffractometer with graphite monochromated Mo,, radiation (=
i0.71069 A). Data
collection at T = - 120 C, u - f l scan, 20,., = 45.9‘. 14110 measured reflections. 13512 unique (R,,,,= 0.065), ofwhich 6424 with I > 3 o ( f )were used in all
calculations. An analytical absorption correction was applied which resulted in
transmission factors ranging from 0.74 to 0.96. The data were corrected for
Lorentz and polarization effects. The structure was solved by direct methods
(SHELXS-86) and refined by the full-matrix least-squares technique (Texsan
5.0). The Ag, Ni, S, and 0 atoms were refined anisotropically; the remaining
atoms were refined isotropically. The residual electron density was not completely modeled. The positions of the porphyrdzine atoms and the peripheral
coordination ofeight silver ions are unambiguous. The highest peak in the final
difference Fourier map was 2 . 9 0 e k 3 . At final convergence, R =
xllFo[= 0.109. R, = [ ( ~ i ~ ( ~ ~ ~ ~ ~ ( ~ ~=~0.136
2 ; ~for
i i
632 parameters. Further details of the crystal structure investigation are available on request from the Director of the Cambridge Crystallographic Data
Centre, 12 Union Road. GB-Cambridge CB2IEZ (UK) on quoting the full
lournal citation.
[I 31 Crystals having cubic morphology have also been isolated. Crystal data: cubic,
u = h = r = 30.200(5)A.
(141 Additional Ag’ ions. not bonded to the porphyrazine. are cocrystaliized in the
lattice.
1151 A. J. Blake. G. Reid, M. Schroder, J. Clirm. Soc. Clzem. Cmnmun. 1992, 1074.
(161 Recent examples a) G. Smith, A. N. Reddy, K. A. Byriel. C. H. L. Kennard,
Po/v/ri&lron 1994, 13. 2425: b) S. 0 .Sommerer, B. L. Westcott. K. A. Ahboud,
Ac/a Crj:rto//ijjir. S K ~ .C 1994, 5 0 , 48; c) H. Adams, N. A. Bailey, D. E. Fenton. Y . 3 . Ho. Inorg. Chrm. Arra 1993. 212. 65.
(171 C. S. Velazquez, T. F. Baumann, M. M. Olnistead, H. Hope. A . G. M. Barrett.
B. M. Hoffman, J. Am. Chem. Sor. 1993. 115. 9997.
Ic.ll/zlFol
0570-0833195i3418-2022.8 10.00+ .25iO
Angew Chem. I n / . Ed. Engl. 1995. 34, No. 18
F o z ) J
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