Chelate-stabilized zinc complexes of alcohols and carbonyl compounds: Pyridylphenylketone and pyridylphenylmethanol

Article abstract of DOI:10.1016/S0020-1693(01)00395-4

The reactions of various zinc salts with the chelating ketone pyridylphenylketone (PPK) and the chelating alcohol pyridylphenylmethanol (PPM) were studied. 2:1 reactions of PPK with ZnX₂ yielded octahedral complexes (PPK)₂ZnX₂ with X = OSO₂CF₃, Cl, Br, NCS. 1:1 reactions yielded the square pyramidal complexes [(PPK)₂ZnHal]₂ZnHal₄ with X = Br, I and the trigonal-bipyramidal complex [(PPK)Zn(NCS)₂]₂. With Zn(SC₆F₅)₂ the tetrahedral 1:1 complex (PPK)Zn(SC₆F₅)₂ resulted. Methanol as a coligand was incorporated in the octahedral complex [(PPK)₂Zn(CH₃OH)₂](BF₄) ₂. Of the PPM complexes, only (PPM)₂Zn(OSO₂CF₃)₂ was analogous to the corresponding PPK complex. The zinc halides produced the octahedral complexes [(PPM)₃Zn]ZnHal₄ with X = Cl, Br. Zn[N(SiMe₃)₂]₂ and PPM yielded polymeric zinc pyridylphenylmethoxide.

Full text of DOI:10.1016/S0020-1693(01)00395-4

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Inorganica Chimica Acta 318 (2001) 23–30
Chelate-stabilized zinc complexes of alcohols and carbonyl
compounds: pyridylphenylketone and pyridylphenylmethanol
C. Sudbrake, H. Vahrenkamp *
Institut fu¨r Anorganische und Analytische Chemie der Uni6ersita¨t Freiburg, Albertstrasse 21, D-79104 Freiburg, Germany
Received 8 January 2001; accepted 14 February 2001
Abstract
The reactions of various zinc salts with the chelating ketone pyridylphenylketone (PPK) and the chelating alcohol
pyridylphenylmethanol (PPM) were studied. 2:1 reactions of PPK with ZnX2 yielded octahedral complexes (PPK)2ZnX2 with
X=OSO2CF3, Cl, Br, NCS. 1:1 reactions yielded the square pyramidal complexes [(PPK)2ZnHal]2ZnHal4 with X=Br, I and the
trigonal-bipyramidal complex [(PPK)Zn(NCS)2]2. With Zn(SC6F5)2 the tetrahedral 1:1 complex (PPK)Zn(SC6F5)2 resulted.
Methanol as a coligand was incorporated in the octahedral complex [(PPK)2Zn(CH3OH)2](BF4)2. Of the PPM complexes, only
(PPM)2Zn(OSO2CF3)2 was analogous to the corresponding PPK complex. The zinc halides produced the octahedral complexes
[(PPM)3Zn]ZnHal4 with X=Cl, Br. Zn[N(SiMe3)2]2 and PPM yielded polymeric zinc pyridylphenylmethoxide. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Crystal structures; Zinc complexes; Ketone complexes; Alcohol complexes
tural curiosities [6]. The situation is somewhat more
favourable with ketones [9]. Not counting the frequent
zinc porphyrin solvates, four zinc–acetone [10,11] and
one zinc–benzophenone complexes [12] have been
structurally characterized. Again, we were the first to
describe the structures of hexa(aldehyde)zinc complexes
[6], and until today no hexa(ketone) complex of zinc
has been fully characterized.
The evasiveness of the simple zinc–alcohol and zinc–
aldehyde complexes has induced others [13–17] and
ourselves [8,18,19] to resort to chelate assistance by
employing pyridine-derived alcohols and aldehydes.
Thereby, convincing structural [19] and functional
[13,14] models of alcoholdehydrogenase could be
obtained.
The present paper continues along these lines. In
order to avoid the pitfalls of aldehyde chemistry in the
presence of zinc ions, a chelating ketone was used. In
order to allow comparisons of bonding and stability,
the corresponding alcohol was also employed. The sys-
tems chosen were pyridylphenylketone (PPK) and
pyridylphenylmethanol (PPM), which are the pheny-
lated analogues of pyridine–carbaldehyde and pyridyl–
methanol used by us previously [18,19]. We are not
1. Introduction
Zinc-containing species play an important role in the
catalytic activation of organic carbonyl compounds.
This is so for both industrial organic chemistry [1] and
biological processes [2]. Specifically, for the zinc con-
taining alcoholdehydrogenase enzymes [2,3] it extends
to the activation of both the carbonyl and alcoholic
functions in their mutual redox interconversions. These
facts provide ample justification for investigating the
coordination chemistry of zinc with aldehydes, ketones,
alcohols and terminal alkoxides as ligands.
However, except for alkoxides, these species are weak
ligands and bind to zinc only when better ligands or
donor solvents are absent. Typically, recrystallization
from methanol can produce methanol adducts of zinc
complexes [4], and we were the first to determine the
crystal structures of hexa(alcohol)zinc complexes [5].
Similarly, prior to our own extensive studies [6–8] the
aldehyde complexes of zinc were laboratory and struc-
* Corresponding author. Tel.: +49-761-203 6120; fax: +49-761-
203 6001.
E-mail address: vahrenka@uni-freiburg.de (H. Vahrenkamp).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00395-4

24
C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
aware of any zinc complex chemistry of these two
ligands, but several copper complexes of PPK were
described by Goher et al. [20].
spective of the stoichiometric ratio of ZnHal2 and
PPM.
In order to introduce deprotonated PPM as an
alkoxide ligand, PPM was reacted with Zn[N(SiMe3)2]2,
in which the silylamide ligands act as a base and a good
leaving group. The complex [Zn(pyridylphenylmethox-
ide)2]x (13) was obtained, which is likely to be an
alkoxide-bridged oligomer.
2.3. Structural considerations
1
The H NMR spectra of the complexes (see Section
2. Results and discussion
3), showing mostly aromatic resonances, are of little
diagnostic value. In contrast, the IR data of the PPK
complexes (Table 1) are quite informative. They prove
both O and N coordination of PPK in all cases by the
typical lower-wavenumber shift of the w(CO) absorp-
tions and the typical higher-wavenumber shift of the
w(CN) pyridine ring absorptions. Although the w(CN)
bands move little, there are characteristic variations
among the w(CO) bands: in those complexes where a
high coordination number and/or good coligands are
present (2–4) there is the least shift of w(CO). When the
number of good donors is small or when the complexes
are cationic (1, 5, 6, 9) there is the highest shift of
w(CO). The complexes of PPM (10–13) lack such char-
acteristic IR features, showing as typical bands only the
2.1. Complexes of PPK
The common anhydrous zinc salts were reacted with
PPK in 1:2 and 1:1 stoichiometric ratios. The 1:2
reactions were straightforward for Zn(CF3SO3)2, ZnCl2,
ZnBr2 and Zn(NCS)2 yielding the octahedral 1:2 com-
plexes 1–4 (PPK)2ZnX2 [X=CF3SO3 (1), Cl (2), Br (3),
NCS (4)].
When a 1:1 stoichiometric ratio was employed for
Zn(CF3SO3)2, complex 1 resulted again. However, with
ZnBr2 and ZnI2, products with a 3:4:6 ratio of zinc,
PPK and halide resulted, which were identified as
[(PPK)2ZnHal]2ZnHal4 (Hal=Br (5), I (6)). Yet an-
other composition (1:1:2) was observed with Zn(NCS)2,
the resulting complex being identified as the thio-
cyanate-bridged dimer [(PPK)Zn(NCS)2]2 (7).
Starting with Zn(SC6F5)2, one PPK ligand could be
incorporated, resulting in the tetrahedral complex
(PPK)Zn(SC6F5)2 (8). In an attempt to prepare a com-
plex bearing only PPK ligands, the very labile methanol
complex [Zn(MeOH)6](BF4)2 was treated with PPK.
Irrespective of the stoichiometric ratio of the reagents,
only two PPK ligands were attached to zinc in the
product [(PPK)2Zn(MeOH)2](BF4)2 (9).
broad OH absorptions between 3100 and 3300 cm−1
.
Of the 1:2 complexes 1–4, 1 was chosen for a struc-
ture determination, the result of which is shown in Fig.
1. The ligand arrangement around zinc in the cen-
trosymmetrical molecule is close to octahedral. The
ZnꢀO(ketone) bond length is relatively short when
compared with ZnꢀO(aldehyde) bond lengths in related
complexes of pyridine–carbaldehyde [8]. This corre-
sponds to the expectation that the ketonic ligands are
better donors than the aldehydes towards zinc. In con-
trast, the ZnꢀO(sulfonate) bonds are comparatively
long, as might have been expected considering the
2.2. Complexes of PPM
As expected, PPM proved to be a weaker ligand than
PPK. Furthermore, the racemic nature of PPM as
resulting from the reduction of PPK seems to hamper
crystallization, and hence an unambiguous characteri-
zation of the resulting compounds. Thus the structural
assignments given for the PPM complexes rest mostly
on their analytical compositions.
Only with Zn(CF3SO3)2 was a product obtained that
is analogous to that containing PPK: complex
(PPM)Zn(CF3SO3)2 (10) resulted in good yields. With
ZnCl2 and ZnBr2 a dismutation of the zinc halide seems
to occur again, this time leading to cationic constituents
having three of the O,N-chelating PPM ligands per zinc
ion. The resulting complexes [(PPM)3Zn]ZnHal4 [Hal=
Cl (11), Br (12)] were the only isolated products, irre-
Table 1
IR data (KBr, cm−1) of the PPK complexes
a
6˜(CꢁO)
6˜(CN)
PPK
1668
1624
1648
1649
1659
1622
1619
1635
1638
1625
1578
1598
1594
1595
1597
1585
1584
1595
1595
1598
1
2
3
4
5
6
7
8
9
a Pyridine ring vibration.

C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
25
,
Fig. 1. Molecular structure of the centrosymmetrical complex (PPK)2Zn(CF3SO3)2 (1). Bond lengths (A): ZnꢀN, 2.049(3); ZnꢀO1, 2.117(2);
ZnꢀO2, 2.185(3); O1ꢁC, 1.229(4); O2ꢀS 1.453(3). Bond angles (°): N1ꢀZnꢀO1, 79.06(10); N1ꢀZnꢀO1%, 100.94(10); ZnꢀO1ꢀC, 112.1(2); ZnꢀO2ꢀS,
138.0(2).
,
Fig. 2. Structure of the [(PPK)2ZnI] cations in 6. Bond lengths (A): ZnꢀN1, 2.067(5); ZnꢀN2, 2.055(5); ZnꢀO1, 2.156(4); ZnꢀO2, 2.161(4); ZnꢀI,
2.523(1); O1ꢁC, 1.235(7); O2ꢁC, 1.240(7). Bond angles (°): N1ꢀZnꢀO1, 76.8(2); N2ꢀZnꢀO2, 77.0(2); N1ꢀZnꢀO2, 92.3(2); N2ꢀZnꢀO1, 91.8(2);
IꢀZnꢀN1, 115.7(1); IꢀZnꢀN2, 114.3(1); IꢀZnꢀO1, 105.0(1); IꢀZnꢀO2, 101.1(1).
mediocre ligating qualities of the triflate ion. As ob-
served for the aldehyde complexes [6–8], the CꢁO bond
length changes little upon coordination.
gives no clue as to why for certain zinc halide/NO
ligand combinations the [L2ZnHal]2ZnHal4 constitution
is preferred.
This suggests that complexes 2–4 assume structures
like that of 1. There is no evidence for or against this
assumption other than the IR data, which group 2–4
together and differentiate them from 1. However, pyri-
dine–carbaldehyde forms octahedral L2ZnHal2 com-
plexes for Hal=Cl, Br, I, which have the halide ligands
in a cis-orientation [8]. Accordingly a cis-structure must
also be considered for 2–4.
Of the two 3:4:6 complexes, 6 was chosen for a
structure determination. Fig. 2 shows the cationic con-
stituents of 6. Their square-pyramidal structure corre-
sponds in nearly all molecular details to that of the
corresponding pyridine–carbaldehyde zinc complex [8].
The only difference worth mentioning concerns the
The 1:1 composition of the thiocyanate complex 7
had led us to assume it to have a tetrahedral structure
with both thiocyanate ligands attached via their sulfur
atoms, as observed by us in several cases for
(chelate)Zn(SR)2 complexes [19]. The observed dinu-
clear structure (see Fig. 3) is unique for us: firstly
because we have never observed it for pyridine-derived
aldehydes or alcohols [8,19], and secondly because it is
the first case of a trigonal-bipyramidal coordination of
zinc in such species. The bond lengths and angles in the
molecule are in the normal range, with the noteworthy
observation that the axial and bridging NCS ligand has
a shorter ZnꢀN bond than the equatorial and terminal
NCS ligand. Obviously, the ZnꢀS coordination at one
terminus of the bridging NCS ligand does not reduce
the donor qualities at the other terminus and hence the
strength of the axial ZnꢀN bond.
,
ZnꢀO bond lengths: they are about 0.1 A shorter in 6
than in the aldehyde complex, again confirming the
better donor qualities of the ketone PPK. The structure

26
C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
The structure of the tetrahedral 1:1 complex 8 can be
situation before for zinc complexes containing alcohol
and aldehyde ligands in the same molecule [6].
deduced with some certainty from several similar struc-
tures of (NO ligand)Zn(SC6F5)2 complexes determined
by us before [19]. The ZnONS2 coordination pattern
corresponds to that in alcoholdehydrogenase [3], and
the tetrahedral arrangement should be severely dis-
torted with a small OꢀZnꢀN and a large SꢀZnꢀS angle.
Complex 9 was subjected to a structure determina-
tion to find out whether the methanol constituents are
actually bound to zinc and whether comparative infor-
mation as to the ketone versus alcohol binding
strengths can be obtained. Fig. 4 shows that the trans-
octahedral Zn(PPK)2X2 arrangement of 9 is quite simi-
lar to that in 1. The major difference between 1 and 9
consists in the fact that the alcohol in 9 has shorter
ZnꢀO bonds than the sulfonate in 1. The most impor-
tant bonding information is that that there is no signifi-
cant difference between the ZnꢀO(alcohol) and
ZnꢀO(carbonyl) bond lengths. We have observed this
As suitable single crystals of the PPM complexes
could not be obtained their structures had to be de-
duced by analogy. For 10 it can be concluded from the
reaction course and solubility behaviour that its ligand
arrangement corresponds to that of 1. Convincing evi-
dence for the structural assignment of 11 and 12 is
lacking. The analytical composition is in accord with
the given formulas, which imply octahedral tris(chelate)
coordination of PPM. Previous experience with
2-pyridylmethanol [18] would have predicted a formula-
tion as [(PPM)2ZnHal]2ZnHal4, like in 6 and 7. Though
we have not observed tris(chelate) complexes of zinc
with N,O-chelating alcohols before [18,19], we did so
with N,O-chelating aldehydes [8]. Finally, complex 13 is
unlikely to be a tetrahedrally coordinated monomer
owing to its low solubility. We propose it to be an
oligomer or polymer containing interconnected arrays
,
Fig. 3. Molecular structure of the centrosymmetrical dinuclear complex [(PPK)Zn(NCS)2]2 (7). Bond lengths (A): ZnꢀN1, 2.053(3); ZnꢀN2,
1.923(3); ZnꢀN3, 2.072(3); ZnꢀO1, 2.236(2); ZnꢀS, 2.405(1); O1ꢁC, 1.230(4). Bond angles (°): N1ꢀZnꢀO1, 75.7(1); N1ꢀZnꢀN2, 120.8(1); N2ꢀZnꢀS,
115.6(1); N1ꢀZnꢀS, 118.9(1); O1ꢀZnꢀN3, 171.8(1); ZnꢀN2ꢀC, 174.9(3); ZnꢀN3ꢀC, 152.9(2); ZnꢀSꢀC, 99.3(1).
,
Fig. 4. Structure of the [(PPK)2Zn(MeOH)2] cations in 9. Bond lengths (A): ZnꢀN1, 2.062(2); ZnꢀN2, 2.058(2); ZnꢀO1, 2.157(2); ZnꢀO2, 2.142(2);
ZnꢀO3, 2.096(2); ZnꢀO4, 2.156(2); O1ꢁC, 1.229(3); O2ꢁC, 1.228(3). Bond angles (°): N1ꢀZnꢀO1, 76.8(1); N2ꢀZnꢀO2, 77.3(1); N1ꢀZnꢀO2,
109.8(1); N2ꢀZnꢀO1, 96.0(1); N1ꢀZnꢀN2, 171.9(1); O1ꢀZnꢀO2, 173.2(1); O3ꢀZnꢀO4, 171.8(1).

C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
27
of ZnL2 units held together by bridging alkoxide units,
thereby giving the zinc ions an octahedral ZnN2O4
coordination as in 1 or 9. Such an array of doubly
O-bridged ZnN2O2 units, which occurs frequently in
transition metal salen complexes, has, for instance, been
found for tetrameric zinc oxinate [21]. Strong donors
should be able to break the array up, and, in accor-
dance with this, 13 dissolves in the strong donor solvent
DMSO, in which it should exist as a ZnL2(DMSO)2
monomer.
[18] and N,N-dimethylaniline [19]. Yet for the closest
structural analogy to the alcoholdehydrogenases, the
ZnONS2 coordination in the L·Zn(SC6F5)2 complexes,
there seems to be a uniform picture: all Zn(SC6F5)2
complexes of O,N-chelating alcohols, aldehydes and
ketones obtained by us so far (this paper and Ref. [19])
are mononuclear tetrahedral (O,N-ligand)Zn(SR)2
species.
The final point of discussion concerns the coordina-
tion numbers of zinc in these complexes. It is common-
place that the coordination numbers of zinc in enzymes
change frequently during enzymatic action. This is
reflected in our work by the occurrence of coordination
numbers 4, 5 and 6 for the same types of O,N ligand,
exemplified here by the PPK complexes 8, 7 and 1.
Furthermore, this paper and our previous work [6] have
shown that alcohols and carbonyl compounds can be
present as ligands in the same complex. Thus, although
the chelating species employed in this work are not
typical as substrates for alcoholdehydrogenase, they
have provided ample information about the basic coor-
dination chemistry in the enzyme.
2.4. Discussion
The PPK and PPM complexes described here provide
a natural complement to the pyridine-derived aldehyde
and alcohol complexes described by us before [8,18,19].
Frequently, compositions and structures are analogous,
but the trans geometries of 1 and 9, the ligand arrange-
ment in dinuclear 7, the 1:3 composition in the cations
of 11 and 12, and the composition and structure of 13
are novel. Again, it has been demonstrated that this
type of N,O-chelate ligand goes along with a wide
variety of coligands, which range from the softest
donors, like iodide or sulfur species, to the hardest
donors and weakest ligands, like triflate or even per-
chlorate [6].
3. Experimental
In comparison with the monodentate aldehydes, ke-
tones or alcohols, there is a significant enhancement of
complex stabilities when using the chelating pyridine-
derived species. The complexes of the latter can be
prepared in donor solvents, their water sensitivity is
low, complex formation does not require a large excess
of the ligand, and their handling, e.g. for reactions or
structure determinations, is greatly facilitated. This ad-
vantage is not outweighed by seriously altered Znꢀ(O-
ligand) bonding situations, as has been demonstrated
by the structural comparisons.
One important motivation for this work was to
gather information for a comparison of the binding
between zinc and the carbonyl or alcoholic functions.
As the structural data in this and the preceding papers
[5–8,18,19] have shown, there is little difference in
terms of bond lengths or hydrolytic sensitivities. As a
consequence, the replacement of alcohol by carbonyl
ligands (this paper), as well as the replacement of
carbonyl by alcohol ligands [6], is possible. This bears
relevance in the context of the function of alcoholdehy-
drogenases, which are able to both oxidize alcohols and
reduce carbonyl compounds [3].
3.1. General procedures
For the general working and measuring procedures,
see Ref. [22]. Ligand PPK and the zinc salts were
obtained commercially. All reagents were stored and
handled under anhydrous conditions.
3.2. Preparations
Ligand PPM [23] was prepared by a new route:
20.65 g (0.113 mol) of PPK in 120 ml of methanol at
0°C were treated in small portions with 5.00 g
(0.132 mol) of solid NaBH4. After stirring for 2.5 h at
room temperature, 250 ml of water were added slowly
and the mixture stirred for another 0.5 h. Then it was
extracted with five 75 ml portions of CH2Cl2 and the
organic extracts dried over MgSO4. After removal of
the solvent in vacuo the solid residue was recrystallized
from n-heptane/benzene (1:1), yielding 16.58 g (79%) of
colourless PPM, m.p. 132°C. IR (KBr): 3112 vs, br
1
(OH). H NMR (CDCl3): l=5.75 (s, 1H, CH), 7.30
(m, 8H, aromatic), 7.60 (s, br, 1H, OH), 8.55 (m, 1H,
aromatic).
Irrespective of the similarity in bonding capabilities,
the chelating alcohols and carbonyl compounds display
characteristic differences in terms of compositions and
structures of their zinc complexes. This is most obvious
in this paper for the zinc halide complexes (2–7 versus
11 and 12). Previously we had observed such differences
for the alcohols and aldehydes derived from pyridine
3.2.1. Complex 1
1.00 g (2.75 mmol) of anhydrous Zn(CF3SO3)2 and
1.00 g (5.50 mmol) of PPK were dissolved in 25 ml of
absolute methanol and stirred for 15 min. After re-
moval of the solvent in vacuo the residue was crystal-

28
C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
lized from acetonitrile, yielding 1.45 g (72%) of 1 as
colourless crystals, m.p. 252°C.
3.2.6. Complex 6
Like 5, from 0.73 g (4.00 mmol) of PPK and 1.28 g
(4.00 mmol) of anhydrous ZnI2: yield 0.80 g (35%) of 6,
colourless crystals, m.p. 148°C.
Anal. Found: C, 42.78; H, 2.49; N, 3.84; Zn, 8.97%.
Calc. for C26H18F6N2O8S2Zn (729.95): C, 42.78; H,
2.44; N, 3.94; Zn, 9.58.
Anal. Found: C, 34.68; H, 2.27; N, 4.04; Zn, 11.33%.
Calc. for C48H36I6N4O4Zn3·CH3CN (1690.43+41.05):
C, 34.51; H, 2.23; N, 4.01; Zn, 11.73.
1H NMR (CD3CN): 7.60 (m, 2H), 7.78 (m, 1H), 7.89
(m, 2H), 8.08 (m, 1H), 8.37 (m, 2H), 9.03 (m, 1H).
1H NMR (CDCl3): 1.96 (s, 3H, CH3CN), 7.55 (m,
2H), 7.69 (m, 4H), 7.86 (m, 8H), 7.92 (m, 12H), 8.17
(m, 8H), 8.98 (m, 4H).
3.2.2. Complex 2
Like 1, from 1.10 g (6.00 mmol) PPK and 0.41 g
(3.00 mmol) of anhydrous ZnCl2 in 15 ml of acetoni-
trile. Yield 0.80 g (53%) of 2, colourless crystals, m.p.
128°C.
3.2.7. Complex 7
Like 4, from 0.63 g (3.50 mmol) of Zn(NCS)2 and
0.64 g (3.50 mmol) of PPK. The product was precipi-
tated with diethyl ether and recrystallized from acetoni-
trile/chloroform (1:1), yielding 0.89 g (35%) of 7 as
colourless crystals, m.p. 234°C.
Anal. Found: C, 57.33; H, 3.61; N, 5.57; Zn, 13.02%.
Calc for C24H18Cl2N2O2Zn (502.71): C, 56.79; H, 3.57;
N, 5.82; Zn, 12.88.
1H NMR (CDCl3): 7.40 (m, 2H), 7.53 (m, 1H), 7.71
(m, 2H), 7.81 (m,1H), 8.03 (m, 2H), 9.19 (m, 1H).
Anal. Found: C, 46.10; H, 2.49; N, 11.52; Zn,
17.93%. Calc. for C28H18N6O2S4Zn2 (729.53): C, 45.21;
H, 2.43; N, 11.33; Zn, 18.64.
3.2.3. Complex 3
1H NMR (CD3CN): 7.63 (m, 2H), 7.78 (m, 1H), 7.95
(m, 3H), 8.25 (m, 2H), 8.95 (m, 1H).
1.10 g (6.00 mmol) of PPK and 0.68 g (3.00 mmol) of
anhydrous ZnBr2 in 15 ml of warm absolute ethanol
were stirred for 15 min. Upon cooling, complex 3
(1.41 g, 80%) was precipitated as colourless crystals,
m.p. 134°C.
3.2.8. Complex 8
0.148 g (0.809 mmol) of PPK and 0.375 g
(0.809 mmol) of Zn(SC6F5)2 were dissolved in 5 ml of
chloroform and the solution layered with hexane.
Within 6 days, 0.258 g (49%) of 8 had separated as
yellow crystals, m.p. 144°C.
Anal. Found: C, 48.72; H, 3.07; N, 4.73; Zn, 11.05%.
Calc. for C24H18Br2N2O2Zn (591.62): C, 48.76; H, 3.28;
N, 4.67; Zn, 11.06.
1H NMR (CDCl3): 7.44 (m, 2H), 7.55 (m, 1H), 7.77
(m, 3H), 8.02 (m, 2H), 9.20 (m, 1H).
Anal. Found: C, 44.55; H, 1.39; N, 2.17; Zn, 10.12%.
Calc. for C24H9F10NOS2Zn (646.84): C, 44.32; H, 1.37;
N, 2.06; Zn, 10.01.
3.2.4. Complex 4
1H NMR (CDCl3): 7.71 (m, 2H), 7.99 (m, 4H), 8.34
(m, 2H), 9.09 (m, 1H).
0.60 g (3.30 mmol) of Zn(NCS)2 and 1.21 g
(6.60 mmol) of PPK in 15 ml of acetonitrile were stirred
for 30 min. Careful layering with diethyl ether and
storage at 4°C yielded 1.45 g (80%) of 4 as colourless
crystals, m.p. 154°C, which were dried in vacuo.
Anal. Found: C, 56.99; H, 3.31; N, 10.23; Zn,
11.94%. Calc. for C26H18N4O2S2Zn (547.98): C, 56.10;
H, 3.28; N, 10.43; Zn, 12.08.
3.2.9. Complex 9
0.71 g (3.90 mmol) of PPK and 0.56 g (1.30 mmol) of
[Zn(CH3OH)6](BF4)2 were dissolved in 6 ml of ni-
tromethane and the solution layered with n-heptane/di-
ethyl ether (1:1). After 3 days, 0.68 g (78%) of 9 had
separated as colourless crystals, m.p. 282°C.
Anal. Found: C, 46.64; H, 3.91; N, 4.18; Zn, 9.77%.
Calc. for C26H26B2F8O4Zn (669.50): C, 46.48; H, 3.85;
N, 4.00; Zn, 9.88.
1H NMR (CDCl3): 7.40 (m, 2H), 7.53 (m, 1H), 7.76
(m, 3H), 8.02 (m, 2H), 9.04 (m, 1H).
3.2.5. Complex 5
1H NMR (CD3CN): 3.32 (s, 6H, CH3), 7.66 (m, 4H),
7.83 (m, 2H), 7.90 (m, 4H), 8.10 (m, 4H), 8.35 (m, 6H),
9.00 (m, 2H).
1.10 g (6.00 mmol) of PPK and 1.35 g (6.00 mmol) of
anhydrous ZnBr2 in 15 ml of acetonitrile were stirred
for 30 min. Keeping the solution at 4°C for 48 h re-
sulted in the precipitation of 1.60 g (55%) of 5 as
colourless crystals, m.p. 164°C.
3.2.10. Complex 10
Anal. Found: C, 41.43; H, 2.71; N, 4.83; Zn, 13.54%.
Calc. for C48H36Br6N4O4Zn3·CH3CN (1408.43+41.05):
C, 41.33; H, 2.71; N, 4.84; Zn, 13.26.
1.00 g (5.50 mmol) of PPM and 1.00 g (2.75 mmol) of
Zn(CF3SO3)2 were dissolved in 30 ml of hot acetoni-
trile. After cooling to room temperature, the solvent
was removed in vacuo and the residue recrystallized
from acetonitrile/chloroform (3:1), yielding 1.39 g
(71%) of 10 as colourless crystals, m.p. 151°C.
1H NMR (CD3CN): 1.93 (s, 3H, CH3CN), 7.62 (m,
8H), 7.76 (m, 4H), 7.98 (m, 12H), 8.27 (m, 8H), 9.20
(m, 4H).

C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
29
Anal. Found: C, 42.54; H, 3.00; N, 3.82; Zn, 8.91%.
Calc. for C26H22F6N2O8S2Zn (733.98): C, 42.45; H,
3.02; N, 3.80; Zn, 9.57.
1H NMR (CD3CN): 1.95 (s, 3H, CH3CN), 5.98 (s,
3H, CH(OH)), 7.25 (m, 21H), 7.77 (m, 3H), 8.45 (m,
3H).
1H NMR (CD3CN): 6.16 (s, 1H, CH(OH)), 7.30 (m,
7H), 7.60 (m, 1H), 8.00 (m, 1H), 8.60 (m, 1H).
3.2.13. Complex 13
0.44 g (1.30 mmol) of Zn[N(SiMe3)2]2 were added to
a solution of 0.50 g (2.70 mmol) of PPM in 40 ml of
anhydrous CH2Cl2. After stirring for 1 h the solution
was layered with hexane. After 3 days, 0.35 g (60%) of
13 had separated as a colourless powder, m.p. 99°C.
Anal. Found: C, 66.45; H, 4.65; N, 6.46; Zn, 15.07%.
Calc. for C24H20N2O2Zn (433.82): C, 66.19; H, 4.61; N,
6.25; Zn, 14.75.
3.2.11. Complex 11
0.74 g (4.00 mmol) of PPM and 0.55 g (4.00 mmol) of
anhydrous ZnCl2 were dissolved in 6 ml of warm anhy-
drous acetonitrile. Upon cooling to room temperature,
0.66 g (40%) of 11 were precipitated as a colourless
powder, m.p. 148°C.
Anal. Found: C, 52.50; H, 4.17; N, 6.44; Zn, 15.04%.
Calc. for C36H33Cl4N3O3Zn2·CH3CN (828.27+41.05):
C, 52.43; H, 4.05; N, 6.07; Zn, 15.15.
1H NMR (DMSO-d6): 5.84 (s, 1H, CH(OH)), 6.46–
8.35 (m, 9H).
1H NMR (CD3CN): 1.93 (s, 3H, CH3CN), 6.14 (s,
3H, CH(OH)), 7.36 (m, 18H), 7.47 (m, 3H), 7.93 (m,
3H), 8.61 (m, 3H).
3.3. Structure determinations
The crystals were obtained directly from the reaction
solutions and used without drying in vacuo. They were
immersed in fluorinated polyether oil and immediately
placed in the nitrogen stream of the diffractometer’s
cooling system. Diffraction data were recorded with the
ꢀ–2q technique on a Nonius CAD4 diffractometer
3.2.12. Complex 12
Like 11, from 0.79 g (4.25 mmol) of PPM and 0.49 g
(2.12 mmol) of anhydrous ZnBr2. Yield 0.75 g (69%) of
12 as a colourless powder, m.p. 148°C.
Anal. Found: C, 43.59; H, 3.47; N, 5.35; Zn, 12.49%.
Calc. for C36H33Br4N3O3Zn2·CH3CN (1006.07+41.05):
C, 43.29; H, 3.49; N, 5.87; Zn, 12.33.
,
fitted with a molybdenum tube (Ka, u=0.7107 A) and
a graphite monochromator. No absorption corrections
Table 2
Crystallographic details
1
6
7
9
Formula
C26H18F6N2O8S2Zn
C48H36I6N4O4Zn3·CH3CN
C28H18N6O2S4Zn2
729.53
0.5×0.3×0.2
C
26H26B2F8N2O4Zn
Molecular mass
Crystal size (mm3)
Space group
Z
729.95
0.8×0.7×0.6
Pbca
1690.43+41.05
0.7×0.3×0.3
C2/c
669.50
0.8×0.8×0.6
P21/n
(
P1
1
4
4
4
,
a (A)
10.028(1)
14.931(2)
19.342(2)
90
90
90
27.219(5)
15.776(3)
14.270(3)
90
111.67(3)
90
7.167(3)
8.266(6)
13.607(3)
97.34(4)
101.85(3)
107.25(5)
737.9(6)
1.64
15.248(3)
12.165(2)
15.704(3)
90
104.29(3)
90
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
2896.0(4)
1.67
5694.6(16)
2.00
2822.8(9)
1.58
dcalc (g cm−3
)
Temperature (K)
293
1.08
293
4.55
183
1.95
183
0.96
v(Mo Ka) (mm−1
)
hkl range
h
k
l
0 to 12
0 to 18
−23 to 0
2837
2835
2021
−33 to 31
0 to 19
0 to 17
5821
5581
3945
−8 to 8
−10 to 0
−16 to 16
3103
2892
2513
−18 to 7
−14 to 14
−18 to 19
11 179
5526
5029
Reflections measured
Independent reflections
Observed reflections (I\2|(I))
Parameters
205
309
190
388
Reflections refined
2835
5581
2892
5526
R1 (observed reflections)
wR2 (all reflections)
Residual electron density (e A
0.038
0.118
+0.3, −0.3
0.037
0.108
+1.4, −1.3
0.033
0.094
+0.8, −0.7
0.038
0.101
+0.5, −0.5
−3
,
)

30
C. Sudbrake, H. Vahrenkamp / Inorganica Chimica Acta 318 (2001) 23–30
[3] Cf. articles of Eklund, Cedergren-Zeppezauer, Zeppezauer,
Pocker, Pettersson, Makinen, Dutler and Dunn in I. Bertini, C.
Luchinat, W. Maret, M. Zeppezauer (Eds.), Zinc Enzymes,
Birkha¨user, Basel, 1986.
[4] The Cambridge Crystallographic Data File lists 41 structures of
zinc complexes with methanol ligands, of which 17 are porphyrin
complexes.
[5] C. Sudbrake, B. Mu¨ller, H. Vahrenkamp, Eur. J. Inorg. Chem.
(1999) 2009.
[6] B. Mu¨ller, H. Vahrenkamp, Eur. J. Inorg. Chem. (1999) 117 and
references cited therein.
were applied. The structures were solved with direct
methods and refined anisotropically with the SHELX
program suite [24]. Hydrogen atoms were included with
fixed distances and isotropic temperature factors 1.5
times those of their attached atoms. Parameters were
refined against F2. The R values are defined as R1=
S ꢀFo−Fcꢀ/S Fo and wR2={S [w(Fo2−Fc2)2]/S [w-
(Fo2)2]}1/2. Drawings were produced with SCHAKAL [25].
Table 2 lists the crystallographic data.
[7] B. Mu¨ller, H. Vahrenkamp, Eur. J. Inorg. Chem. (1999) 129.
[8] B. Mu¨ller, H. Vahrenkamp, Eur. J. Inorg. Chem. (1999) 137.
[9] The Cambridge Crystallographic Data File reports 50 structures
of zinc complexes with ketonic ligands, of which 23 bear b-dike-
tonate-type ligands.
4. Supplementary material
[10] R.A. Edwards, O.P. Gladkikh, M. Nieuwenhuyzen, C.J.
Wilkins, Z. Kristallogr. 214 (1999) 111.
[11] V.C. Adam, U.A. Gregory, B.T. Kilbourn, J. Chem. Soc. D
(1970) 1400.
[12] V.K. Bel’ski, R.N. Streltsova, B.M. Bulychev, P.A. Storozkenko,
L.V. Ivankina, A.I. Gorbunov, Inorg. Chim. Acta 164 (1989)
211.
[13] D.J. Creighton, J. Hajdu, D.S. Sigman, J. Am. Chem. Soc. 98
(1976) 4619.
The crystallographic data of the structures described
in this paper were deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication
nos CCDC-149836 (for 1), 149837 (for 7), 149838 (for
6) and 149839 (for 9). Copies of these data are available
free of charge from the following address: The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44-1223-336033; e-mail: teched@chemcrys.
cam.ac.uk).
[14] M. Hughes, R.H. Prince, J. Inorg. Nucl. Chem. 40 (1978) 703.
[15] A. Ohno, S. Yasui, R.A. Gase, S. Oka, V.K. Pandit, Bioorg.
Chem. 9 (1980) 199.
[16] M. Bochmann, G.C. Bwembya, R. Grinter, A.K. Powell, K.J.
Webb, M.B. Hursthouse, K.M. Abdul Malik, M.A. Mazid,
Inorg. Chem. 33 (1994) 2290.
Acknowledgements
[17] T. Sato, H. Takeda, K. Sakai, T. Tsubomura, Inorg. Chim. Acta
246 (1996) 413.
[18] M. Tesmer, B. Mu¨ller, H. Vahrenkamp, J. Chem. Soc., Chem.
Commun. (1997) 721.
[19] B. Mu¨ller, A. Schneider, M. Tesmer, H. Vahrenkamp, Inorg.
Chem. 38 (1999) 1900.
This work was supported by the Deutsche
Forschungsgemeinschaft. We are indebted to Mrs P.
Klose for help with the preparative work.
[20] M.A.S. Goher, R.J. Wang, T.C.W. Mak, J. Coord. Chem. 38
(1996) 151 and references cited therein.
[21] Y. Kai, M. Morita, N. Yasuoka, N. Kasai, Bull. Chem. Soc.
Jpn. 58 (1985) 1631.
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