Preparation of non-substituted metal phthalocyanines at low temperature using activated Rieke zinc and magnesium

Article abstract of DOI:10.1080/15533170500360248

Synthesis of non-substituted metal phthalocyaninates starting from phthalonitrile in various alcohols in presence of chemically activated Rieke zinc and magnesium in three forms (ordinary magnesium turnings, activated Rieke magnesium and complex Mg(anthracene)·3THF) at low temperatures (20-50°C) is described. It is shown that the presence of active elemental metal causes a rapid PcM formation in low-weight alcohols. Copyright

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Preparation of Non-Substituted Metal Phthalocyanines
at Low Temperature Using Activated Rieke Zinc and
Magnesium
B. I. Kharisov a , L. A. Garza-Rodríguez a , H. M. Leija Gutiérrez a , U. Ortiz Méndez a , R.
García Caballero a & A. Yu. Tsivadze b
a Universidad Autónoma de Nuevo León. A.P., Ciudad Universitaria UANL, San Nicolás de los
Garza, N.L., México
b Institute of Physical Chemistry, Moscow, Russia
Version of record first published: 31 Jan 2012
To cite this article: B. I. Kharisov, L. A. Garza-Rodríguez, H. M. Leija Gutiérrez, U. Ortiz Méndez, R. García Caballero & A. Yu.
Tsivadze (2005): Preparation of Non-Substituted Metal Phthalocyanines at Low Temperature Using Activated Rieke Zinc and
Magnesium, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 35:10, 755-760
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Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, 35:755–760, 2005
Copyright # 2005 Taylor & Francis, Inc.
ISSN: 1553-3174 print/1532-2440 online
DOI: 10.1080/15533170500360248
Preparation of Non-Substituted Metal Phthalocyanines
at Low Temperature Using Activated Rieke Zinc and Magnesium
´
´ ´
B. I. Kharisov, L. A. Garza-Rodrıguez, H. M. Leija Gutierrez, U. Ortiz Mendez,
´
and R. Garcıa Caballero
´ ´ ´
Universidad Autonoma de Nuevo Leon. A.P., Ciudad Universitaria UANL, San Nicolas de los Garza,
´
N.L., Mexico
A. Yu. Tsivadze
Institute of Physical Chemistry, Moscow, Russia
lower temperatures, although frequently with relatively low
Synthesis of non-substituted metal phthalocyaninates starting yields in comparison with classic syntheses. In these
from phthalonitrile in various alcohols in presence of chemically
activated Rieke zinc and magnesium in three forms (ordinary
conditions, at low temperatures, an additional “impulse” is
needed for the phthalonitrile cyclization process; precisely,
magnesium turnings, activated Rieke magnesium and complex
.
surface energy of strong base (solid CH3ONa) (Nemykin
et al., 2000) or extra energy of defects in the surface of elemen-
tal metals (Kharisov et al., 2004) could serve as an impulse to
reach the energetic barrier. Therefore, any source of additional
energy could be useful for the successful synthesis at low
temperatures.
Mg(anthracene) 3THF) at low temperatures (20–508C) is
described. It is shown that the presence of active elemental
metal causes a rapid PcM formation in low-weight alcohols.
Keywords zinc and magnesium phthalocyaninate, Rieke metals,
synthesis at low temperature
Metals in activated form (Fu¨rstner, 1996), in particular those
obtained from anhydrous metal salts and alkali metals
(so-called Rieke metals (Fu¨rstner, 1996; Rieke, 2000; Rieke
et al., 1996, 1997; Rieke and Kim, 1998a, 1998b, 2000;
Talukdar et al., 1998; Lee et al., 2000; Sugimoto, 2003)
could be extremely useful to carry out PcM synthesis at low
temperature. The peculiarity of such pyrophoric forms of
metals is a high number of defects and imperfections in
metal surface, which make them much more active in compari-
son with the same metals in their “standard” form (sheet, wire
or non-active powder). In the present work, we have studied the
interaction of activated metallic zinc and magnesium in
the form of Rieke metals with phthalonitrile in a series of
non-aqueous solvents in the temperature range 20–508C.
Elemental magnesium in non-activated form or in active
forms f(Mgꢀ) and its complexes (sources of “soluble” zero-
INTRODUCTION
Well-known classic non-substituted phthalocyanine PcH2
and its metal complexes are usually obtained from different
precursors in non-aqueous solvents in 80–2508C temperature
range (Leznoff and Lever, 1990; Thomas, 1990). Using phtha-
lonitrile as a precursor and applying a series of techniques
(UV-treatment of the reaction system (Tomoda et al., 1976;
Kharisov et al., 2005a), use of elemental metals in the form
of finely divided metal powders (Leznoff et al., 2000;
Kharisov et al., 2004), solid strong bases (Nemykin et al.,
2000) and zeolites (Kharisov et al., 2005b), direct electroche-
mical synthesis (Turek et al., 1987; Petit et al., 1991;
Kharisov et al., 1999, 2000) using sacrificial anodes (and
even cathodes), phthalocyanine preparations can be carried at
ꢀ
.
valent magnesium Mg(anthracene) 3THF and MgH2 g are
widely used in synthetic organic and organometallic chemistry
(Fu¨rstner, 1996;). Sometimes its use requires a preactivation by
different methods (sonication or formation of intermediate
active magnesium complexes) (Baker et al., 1991). With
respect to its application in phthalocyanine chemistry, the
reaction of elemental magnesium with phthalonitrile was first
studied by Linstead et al., (1934). In these pioneering exper-
iments, the reaction mixture needed to be heated up to 2958C
Received 18 August 2005; accepted 9 September 2005.
The authors are very grateful to CONACyT (project 39,558-Q) and
UANL (PAICyT-2005) for financial support.
Address correspondence to B. I. Kharisov, Facultad de Ciencias
´
Quimicas, Universidad Autonoma de Nuevo Leon, 66450 San
Nicolas de los Garza 18-F, Nuevo Leon, A.P. 18-F, C.P. 66450,
´
´
´
´
Mexico. E-mail: bkhariss@ccr.dsi.uanl.mx
755

756
B. I. KHARISOV ET AL.
(boiling point of phthalonitrile) to start the reaction; the metallic potassium (30.78 g, 0.7874 mol) in the form of small
reported yield was only 9.5%. Then, Rieke Burnst (1987) pieces and THF (350 mL), freshly distilled over metallic
used activated magnesium Mgꢀ in refluxing glyme forming sodium were collocated in a 500-mL flask with refrigerator
magnesium phthalocyanine (according to IR-spectral data) (all inside the nitrogen-containing glove box) and stirred vigor-
for 5 min with 38% yield at room temperature conditions. ously with simultaneous gradual heating to boiling point of
Among non-synthetic reports on magnesium phthalocyaninate, THF (668C). Reaching melting point of potassium, the
recent works of Mizuguchi (2001a, 2001b) should be noted, heating and stirring were immediately suspended, since the
where its crystal structure and p-p interactions are discussed. reaction became very exothermic and needed cooling. After
In our current work, we have used different forms of this active reaction step, the mixture was stirred vigorously
magnesium and zinc for phthalocyanine preparation in low- for 3 h to guarantee a total consumption of potassium, then
weight alcohols at low temperatures (208–508C).
the flask was kept without stirring and heating for 3–5 h in
order to precipitate the formed metal. Then THF was
decanted, new portion of fresh THF (250–300 mL) was
added, the mixture was stirred for 5 min and kept for 1 h.
This last operation was repeated once again. Rieke zinc was
prepared similarly using anhydrous zinc chloride (21.550 g,
0.1581 mol), metallic potassium (11.448 g, 0.0256 mol), and
THF (300 mL). Alternatively, the equipment shown in Fig. 1
was used for Rieke metal preparation.
EXPERIMENTAL PART
Materials and Equipment
Phthalonitrile, metallic magnesium and zinc, 30% solution
of CH3ONa in CH3OH, anthracene, and PcH2 (Aldrich) as a
standard were used as supplied. Solvents (methanol, ethanol,
propanol, 1-butanol, from Aldrich and Fisher) were distilled
by standard methods before use. Metals were treated by tech-
niques below before use. Organic microanalyser (Perkin-
Elmer) was used for C, H and N contents determination.
Infrared spectra were recorded on Bruker (Tensor 27) and
Perkin-Elmer, respectively. Ultrasonic treatment of reaction
systems was carried out in the ultrasonic cleaners of different
capacity (3 and 11 L), as well as using stronger ultrasonic
source (sonic dismembrator, Fisher, model 500, in some
selected experiments).
The obtained powders (Rieke magnesium and zinc) were
kept for further use in phthalonitrile cyclization processes.
Since the activity of freshly obtained Rieke metals generally
decreases (Fu¨rstner, 1996) in hours or days due to further
agglomeration of formed small metal particles, the Rieke
metals were used for phthalocyanine preparation immediately
or up to 2 days after its preparation.
.
Preparation of the Complex Mg(anthracene) 3THF
This procedure was carried out according to published lit-
erature (Fu¨rstner, 1996) with small changes. All manipulations
were carried out under nitrogen. A mixture of 24.3 g (1.0 mol)
of purified magnesium pulverized turnings and 200 g of anthra-
cene was introduced into a three-necked 2 L flask and heated
for 10 min at 1108C in an oven. Thereafter, the flask was
equipped with a glass reflux condenser and a magnetic
stirring bar and flushed with nitrogen; 1 L of anhydrous THF
and a few drops (ꢀ0.05 mL) of ethyl bromide were added.
The suspension was stirred for 36 h at 608C and 12 h more in
an ultrasonic field to achieve the conversion of Mg to the
Use of Activated Elemental Metals in Synthetic Procedures
Magnesium was used in the following three forms: 1) usual
metallic magnesium in the form of turnings, chemically treated
before use; 2) Rieke magnesium; 3) classic complex Mg(an-
.
thracene) 3THF. Zinc was used in the form of Rieke metal
only, since preliminary experiments with use of non-
activated zinc gave only traces of zinc phthalocyaninate.
Non-activated magnesium turnings were used for phthaloni-
trile cyclization after careful purification of its surface from
oxide layer as follows. Mg turnings (20 g) were cut to
decrease their size and collocated to a 500 mL flask, to which
4 M solution of NH4Cl (100 mL) was added. The mixture
was heated for 30 min at room temperature at controlled
pH 4–8 with use of 6 M HCl to avoid formation of magnesium
hydroxide. Then solution was decanted, magnesium was
washed two times with 100 mL of distilled water (50 mL),
three times with absolute ethanol (50 mL) and two times with
THF (50 mL), and stored under THF.
.
bulky orange precipitate of Mg(anthracene) 3THF. Then the
product was separated mechanically from magnesium pieces,
washed with 2 ꢁ 150 mL of THF and dried for 20 h in vacuo.
Yield 64%. According to Fu¨rstner (1996), the final product
contains trace amounts of anthracene and elemental magne-
sium due to the equilibrium existing between Mg(anthracene)
3THF and its precursors.
Use of Activated Metals for Phthalocyanine Preparation
Generally, a Rieke metal (0.2–0.5 g) or Mg(anthrace-
Preparation of Rieke Magnesium and Zinc
.
The Rieke magnesium was prepared as follows (Rieke et al., ne) 3THF complex (0.5 g) was added to the solution (20 mL
1988). All manipulations with precursors and formed activated of a solvent), containing 3–5 g of phthalonitrile and 5 drops
metal were carried out in a box filled with nitrogen and dried of 30% solution of CH3ONa in methanol. The flask was put
with P4O10. Commercial anhydrous magnesium chloride, into an ultrasonic cleaner and maintained under treatment a
dried in oven at 1308C before use (38.50 g, 0.4044 mol), T ¼ 0–508C for 24–72 h. Then the formed blue product was

NON-SUBSTITUTED METAL PHTHALOCYANINES
757
FIG. 1. Equipment for synthesis of Rieke metals.

758
B. I. KHARISOV ET AL.
separated from unreacted metal by shaking and decanting of
more light metal phthalocyaninate phase with the solvent,
washed with ethanol in Soxhlet equipment and dried in air.
Some experiments were carried out without ultrasonic
treatment.
TABLE 1
Metal phthalocyaninate yields at different temperature (treat-
ment 12 h, with CH3ONa)
Temperature,
8C
Metal phthalo-
cyaninate yield, wt.%
Solvent
Purification and Identification of the Products
Non-activated magnesium (purified turnings)
50
35
Methanol
Methanol
Methanol
18–22
15–20
11–17
Phthalocyanines formed were purified by washing with hot
ethanol in a Soxhlet equipment and dried in air. The products
were characterized by metal content by atomic absorption
spectroscopy. According to elemental analysis data, compo-
sitions of the obtained products correspond to typical metal
phthalocyanines PcM. The samples of formed products,
showed the best correspondence between found and calculated
data, are as follows.
20
20–50
Ethanol, 1-Propanol, 0–15
1-Buthanol (badly reproducible)
Rieke magnesium
50
50
50
50
35
35
35
35
20
20
20
20
Methanol
Ethanol
33
27
57
85
21
36
21
66
5
1-Propanol
1-Butanol
Methanol
Ethanol
Zinc phthalocyaninate: found/calcd.: Zn (10.55/11.32),
C (65.87/66.44), N (18.51/19.38), H (2.46/2.77).
Magnesium phthalocyaninate: found/calcd.: Mg (3.88/4.63),
C (70.88/71.53), N (19.97/20.86), H (2.48/2.98).
1-Propanol
1-Butanol
Methanol
Ethanol
Some variations of composition (0.05–0.30%) were observed
in different experiments. The IR spectra (KBr pellet) of
metal phthalocyanines contain the following main bands
(cm21), among others: 3500–3380 (v.s.,w), 2929 (m), 2851
(m) fn(C–H)g; 2300–2280 (s), 1730 (v.s.), 1622 (s), 1514
(m) fn(C–C) of benzene ringsg; 1472 (m) fn(C–C) of pyrrol
ringsg; 1365 (s) (pyrrol nuclei-mesoatoms of N); 1320 (m),
1150 (s) fg(C–H)g. IR spectra of the same PcM, obtained in
different solvents, are almost identical (the difference is in
the peak intensity).
7
1-Propanol
1-Butanol
43
36
Non-activated zinc
20–50
All 4 alcohols
Traces
Rieke zinc
50
50
50
50
35
35
35
35
20
Methanol
Ethanol
10
8
1-Propanol
1-Butanol
Methanol
Ethanol
Traces
39
12
RESULTS AND DISCUSSION
According to the chemical analysis of the formed products,
corresponding metal phthalocyaninates of 90–96% purity (for
phthalocyanine chemistry, such grade of purity is absolutely
normal) are formed in all cases. Using non-activated mag-
nesium after careful elimination of oxidation products from
its surface, it is possible to obtain magnesium phthalocyaninate
in various non-aqueous solvents with relatively good yields in
the temperature interval 20–508C (Table 1). In the case of
more active Rieke magnesium, metal phthalocyanine yields
in various solvents are considerably higher. However, in the
case of zero-valent magnesium in the form of a Mg-anthracene
complex, it is still difficult to evaluate its influence on the
phthalocyanine cyclization due to low yields of the final
product.
Traces
Traces
9
1-Propanol
1-Butanol
All 4 alcohols
Traces
.
Mg(anthracene) 3THF complex
20–50 All 4 alcohols
Traces
latter possess more activity; such effect is due to high
specific surface areas (Fu¨rstner, 1996) for activated magnesium
and zinc, used in the present work. Additionally, particle sizes
of Rieke magnesium are much smaller in comparison with the
particles of standard magnesium, prepared by grinding of metal
turnings, so higher surface energy of the Rieke form contributes
to easier cyclization of phthalonitrile and, as a consequence,
lower initial temperature of this process. Evidently, high
number of defects and imperfections in the activated metal
surface and small size of metal aggregates make them very
active not only with respect to phthalonitrile cyclization, but
As it is seen, when Rieke metals are used, the best results are
observed in 1-propanol and 1-butanol. This is distinct from our
unpublished results with the use of copper and nickel, where
methanol and ethanol were the highest-yielding solvents. Mag-
nesium is evidently more active in comparison with zinc; this
fact is in accordance with classic organometallic monographs
and textbooks. Comparing non-active and Rieke metals, the

NON-SUBSTITUTED METAL PHTHALOCYANINES
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gates Mn (M ¼ Mg, Zn) in presence of CH3ONa can be
proposed. Mn is an aggregate with high number of defects,
which, under strong ultrasonic treatment, used in the present
work, forms preferential sites of reaction and further allows
elimination of metal atom(s) reacting with organic substrate.
Alternatively, in the case of application of strong ultrasonic
treatment, these aggregates can be eliminated completely
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defects and preferential sites of reaction on the metal surface
and further “extraction” of a metal atom, “associated” with
an organic partner.
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Low-temperature formation of functionalized Grignard reagents
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prations, realized in our laboratory, it is noted that the use of
activated metals is much more effective in comparison with
the use of ultraviolet treatment (Tomoda et al., 1976;
Kharisov et al., 2005a), zeolites (Kharisov et al., 2005b) and
direct electrochemical synthesis starting from sacrificial
metal anodes (Kharisov et al., 1991, 2000). Temperature of
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CONCLUSIONS
Non-substituted metal phthalocyaninates (M ¼ Mg, Zn)
were obtained from phthalonitrile as a precursor and metals
in different forms: non-activated metal and Rieke metal at
low temperatures (20–508C). The last form seems to be
stronger with respect to the cyclization of phthalonitrile in a
series of alcohols. The mechanism, including small metal
aggregates in the surface of the activated metal, is proposed.
It is suggested that high quantity of defects and imperfections
in the surface of activated forms of metals contributes to cycli-
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