Investigations on the interaction of dichloroaluminum carboxylates with lewis bases and water: An efficient road toward oxo- and hydroxoaluminum carboxylate complexes

Article abstract of DOI:10.1021/ic2023924

A series of dichloroaluminum carboxylates [Cl₂Al(O ₂CR)]₂ (were R = Ph (1a), ^tBu (1b), CHCH ₂ (1c) and C₁₁H₂₃ (1d)) were prepared and extended investigations on their structure a

Full text of DOI:10.1021/ic2023924

Article
pubs.acs.org/IC
Investigations on the Interaction of Dichloroaluminum Carboxylates
with Lewis Bases and Water: an Efficient Road toward Oxo- and
Hydroxoaluminum Carboxylate Complexes
Wojciech Bury,† Elzbieta Chwojnowska,† Iwona Justyniak,‡ Janusz Lewinski,*,†,‡ Aneta Affek,†
́
̇
Ewa Zygadło-Monikowska,† Joanna Bak,§ and Zbigniew Florjanczyk*,†
́
̨
†Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
‡Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
§Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
S
* Supporting Information
ABSTRACT: A series of dichloroaluminum carboxylates [Cl2Al(O2CR)]2 (were R = Ph
(1a), tBu (1b), CHCH2 (1c) and C11H23 (1d)) were prepared and extended investigations
on their structure and reactivity toward various Lewis bases and H2O performed.
Compounds [Cl2Al(O2CR)]2 and their adducts with Lewis bases show a large structural
variety, featuring both molecular and ionic forms with different coordination numbers of
the metal center and various coordination modes of the carboxylate ligand. Upon addition
of a Lewis base of moderate strength the molecular form [Cl2Al(O2CR)]2 equilibrates with
new ionic forms. In the presences of 4-methylpyridine the six-coordinate Lewis acid−base
t
adducts [Cl2Al(λ2-O2CR)(py-Me)2] [R = Ph (3a), Bu (3b)] with a chelating carboxylate
ligand were formed. The reactions of 1a, 1b, and 1d with 0.33 equiv of H2O in THF-
toluene solution lead to oxo carboxylates [(Al3O)(O2CR)6(THF)3] [AlCl4] [where R =
Ph (4aTHF), tBu (4bTHF), and C11H23 (4dTHF)] in high yield. The similar reaction of 1c in
tetrahydrofuran (THF) afforded the chloro(hydroxo)aluminum acrylate [(ClAl)2(OH)-
(O2CC2H3)2 (THF)4][AlCl4] (5), while the hydrolysis of 1b in MeCN lead to the hydroxoaluminum carboxylate
1
[Al2(OH)(O2CtBu)2(MeCN)6][AlCl4)3] (6). All compounds were characterized by elemental analysis, H, 27Al NMR, and IR
spectroscopy, and the molecular structure of 1a, 3a, 3b, 4aTHF, 4bTHF, 4bpy‑Me′, 5, and 6 were determined by single-crystal X-ray
diffraction. The study provides a platform for testing transformations of secondary building units in Al-Metal−Organic
Frameworks toward H2O and neutral donor ligands.
coordination in various systems is referred to as a carboxylate
shift; however, the chemistry of aluminum carboxylates is
largely an unexplored area because of a relative paucity of
structural data for simple aluminum-carboxylate systems.
Valuable models for elucidation of the preferred coordination
mode of a carboxylate ligand to aluminum center concern the
[MeCO2(AlMe3)2]− anion with the monodentate carboxylate
ligand I,7 the dimeric [R2Al(μ-O2CR′)]2 complexes with
carboxylate bridging mode II,4b,8 and a number of crystallo-
graphically characterized alkylaluminum compounds derived
from bifunctional carboxylic acids exhibiting a large structural
variation (Scheme 1).9 Surprisingly, the chelating mode III was
not observed, and it was argued that this coordination mode is
unavailable for carboxylates on aluminum because of the ring
strain associated with the AlO2C cycle.8a
INTRODUCTION
■
Aluminum is the third most abundant element in the shallow
Earth, where it forms a rich array of solute molecules and solids,
including clays and aluminum hydroxide phases. The hydrolysis
of aluminum compounds is one of the key steps in sol−gel
routes to commercially important ceramics based on alumina1
and fabrication of methylalumoxane oligomers2 that are used in
industry as cocatalysts for the polymerization of olefins using
group 4 metallocene catalysts. In the past two decades
considerable efforts were made to obtain hybrid inorganic−
organic polymers containing alumina core decorated with
carboxylate ligands, where the synthetic methods applied
include the reactions of aluminum hydroxides (especially
boehmite) with carboxylic acids,3 or controlled hydrolysis of
dialkylaluminum carboxylates.1 Several reports also describe the
application of carboxylate alumoxanes4 as reinforcing nano-
fillers for polymers,3d,5 catalysts supports,6 protecting layers,
and processable precursors for ceramic materials.1 In this
regard, carboxylate anions play an important role in self-
assembly pathways of the metastable species and in the change
of morphology and hydrophobicity of the oligomeric aluminum
salts formed in these systems. This flexibility of the carboxylate
Furthermore, the intensive structural investigations concern-
ing the structure of hydroxo- and oxoaluminum complexes
resulted in the isolation of large purely inorganic model
aggregates such as Al8,10a Al13,10b,c Al30,10d,e or Al32.10c These
Received: November 4, 2011
Published: December 20, 2011
© 2011 American Chemical Society
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experiments. As starting reagents we selected four dichlor-
oaluminum carboxylates derived from benzoic, pivalic, acrylic,
or laurylic acid, that is, [(RCO2)AlCl2]2-type compounds
Scheme 1. Selected Coordination Modes of Both (a) the
Carboxylate Ligand to Al Center and (b) the Oxo- and
Hydroxoaluminum Building Units
t
(where R = Ph (1a), Bu (1b), CHCH2 (1c), and C11H23
(1d)). The carboxylate ligands differ in the steric and electronic
character including one highly lipophilic ligand with a long
aliphatic chain. These compounds were obtained in equimolar
reactions of EtAlCl2 with the corresponding carboxylic acid.
Compounds 1a, 1b, and 1c were isolated in high yield as
colorless crystals, whereas 1d formed a viscous liquid, and fully
characterized spectroscopically in solution, and additionally the
molecular structure of 1a was determined by single crystal X-
ray diffraction studies (because of a low quality of crystals of 1b
and 1c, we were unable to obtain a proper data set to perform a
reliable X-ray analysis).
The molecular structure of 1a consists of two Cl2Al units
bridged by benzoate groups (Figure 1). The Al−O bond
complexes structurally represent the Baker−Figgis−Keggin
i s o m e r s h a v i n g t h e s t o i c h i o m e t r y
AlO4Al12(OH)24(H2O)127+(aq) where oxo- and hydroxoalumi-
num building units display usually trigonal A and tetrahedral B
or D coordination geometries (Scheme 1).11 The trigonal
coordination mode C is rather unique, and to date there are
only two examples of well-defined complexes with incorporated
Al3O moiety, both involving acetate ligands.12,13 Recently, the
μ3-oxo-centered trinuclear aluminum clusters have received
special attention because their employment as building units for
the formation of metal−organic framework (MOF) materials
with giant pores.14 Other unique clusters such as the Al13, Al4,
or Al15 were isolated in the presence of multifunctional
carboxylate ligands.15
In a search for prototypical low-nuclear oxo- and
hydroxoaluminum clusters decorated with carboxylate ligands
as novel suitable precursors of higher aggregates or the
predesigned molecular platform for modeling the reactivity of
prototypical Al-MOFs toward water and/or neutral donor
molecules we considered the use of chloroaluminum
carboxylates that can be obtained in the reaction of aluminum
alkyl chlorides with carboxylic acids. Surprisingly, this class of
aluminum-halogen complexes has not been explored so far.
Only recently we communicated a complex nature of
chloroaluminum benzoates featuring both molecular and ionic
forms with different coordination numbers of the metal center
and various coordination modes of the carboxylate ligand.16
Herein we present systematic investigations on the structure of
[Cl2Al(O2CR)]n-type compounds and their transformation in
the presence of various Lewis bases under anhydrous
conditions, as well as in the presence of water. The study
reports on the first examples of aluminum complexes with a
chelating carboxylate ligand as well as a convenient method for
the synthesis of oxo- and hydroxoaluminum complexes with
bridging carboxylate units. An excellent platform for testing
transformations of secondary building units in Al-MOFs toward
H2O and neutral donor ligands is also provided.
Figure 1. Molecular structure of 1a; hydrogen atoms have been
omitted for clarity. Selected bond lengths (Å) and angles (deg): Al1−
O1, 1.755(3); Al1−Cl1, 2.095(1); Al1−Cl2, 2.099(2); Al1−O2′,
1.777(3); Cl1−Al1−Cl2, 115.6(6); O1−Al1−Cl1, 108.2(1); O1−
Al1−Cl2, 108.8(1); O1−C1−O2, 121.4(4).
lengths (Al−Oav. = 1.766 Å) are slightly shorter than those in
the aluminum alkyl analogues characterized previously (cf. Al−
Oav. = 1.810 Å),17 reflecting the different Lewis acidity of the
X2Al species involved. Interestingly, in the structure of 1a the
central eight-membered Al2O4C2 ring is almost flat, in contrast
to the chairlike conformation of [tBu2Al(μ-O2CPh)]2. The IR
spectrum of 1a (in CH2Cl2) shows two characteristic bands at
1562 cm−1 [νasymm(CO2)] and 1497 cm−1 [νsymm(CO2)] that
can be attributed to the stretching vibrations of the bridging
carboxylate group; however, additional vibrations in this
spectral range are also present, which indicate a more complex
nature of this system in solution. Similar characteristic pattern
can be observed in the IR spectrum of 1b−d also (see the
Experimental Section). The IR spectra of 1d nujol film (see the
Supporting Information) and its solutions in benzene reveal
exclusively the presence of intensive bands at 1572 (υasymmCO2)
and 1488 (υsymmCO2) cm−1 indicating the presence of bridging
carboxylate units.
To have a better understanding of equilibria present in
solutions we performed 27Al NMR spectral studies for 1a−d in
a noncoordinating solvent. The 27Al NMR spectra of 1a and 1b
in CDCl3 display a dominating signal of the dimeric
[(RCO2)AlCl2]2 species at 77 ppm (this chemical shift is
similar to that observed for the chemically closely related four-
coordinate dichloroaluminum acetylacetonate complex exhibit-
ing the 27Al resonances at 88 ppm.18) This signal is, however,
RESULTS AND DISCUSSION
■
Synthesis and Structure Characterization of Dichlor-
aluminum Carboxylates. The reactivity of dichloroalumi-
num carboxylate complexes toward Lewis bases of different
strength as well as water was investigated in a series of control
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accompanied by a number of lower intensity resonances in the
higher and lower field (Figure 2a and 2b). Similar spectrum of
Figure 2. 27Al NMR solution spectra of (a) 1a, (b) 1b, and (c) 1d in
CDCl3 at 20 °C.
1c was very complex and featureless. These observations
indicate that the dimeric form of 1a−1c is unstable in solution
and rearranges to a number of likely neutral and ionic
aluminum species with four- and six-coordinate aluminum
centers.18,19 Surprisingly, the 27Al NMR spectra of 1d recorded
in noncoordinating solvents like benzene or chloroform reveal
only a single resonance at 77 ppm characteristic of the dimeric
form (Figure 2c). The dimeric character of 1d was confirmed
by molecular weight measurements in benzene solution; the
calculated value for the dimer is 594 g/mol whereas the
experimental data were around 600 g/mol. Thus, the data
clearly indicate that the relative concentration of neutral and
ionic species of dichloroaluminum carboxylates and their
association degree in solution strongly depend on the character
of the carboxylate ligand, and the more lipophilic ligand bearing
a long alkyl chain stabilizes the dimeric form with bridging
carboxylate ligands.
Figure 3. 27Al NMR solution spectra of 1a in various solvents: (a)
CDCl3, (b) THF, (c) MeCN, (d) py-Me; (e) 1a:water (1:0,33) in
THF at 20 °C.
with a new ionic form which we tentatively ascribed as
[(RCO2)2Al(THF)x]+[AlCl4]− (2THF) (Scheme 2) based on
our earlier observations for the related dichloroaluminum
acetylacetonate systems.20
Scheme 2
Investigations on the Interaction of Dichloroalumi-
num Carboxylates with Lewis Bases. The revealed solution
behavior of dichloroaluminum carboxylates exhibits a number
of common features with those observed previously for
dichloroaluminum acetylacetonate [Cl2Al(acac)] complex,
that is, both types of compounds form labile molecular species
which readily equilibrate with ionic species in solution,18 and
the latter acetylacetonate derivative was highly reactive toward
Lewis bases.20,21 Therefore, we were also curious as to how the
addition of different Lewis bases might impact on the structure
of chloroaluminum carboxylate species. In the next step we
performed 27Al NMR studies for 1a, 1b, and 1d in the presence
of THF, acetonitrile (MeCN), and 4-methylpyridine (py-Me).
The 27Al NMR spectra of 1a, 1b, and 1d in THF solution are
similar and consist of two dominating signals at 104 ppm and
around 0 ppm, which are characteristic for AlCl4− anion and a
cationic aluminum carboxylate species, respectively.19 However,
the characteristic resonance of a lower intensity at 77 ppm from
the dimeric form of the parent carboxylate can also be observed
(Figure 3b, Supporting Information, Figures S1b and S2a).
These observations indicate that upon addition of THF the
molecular form of dichloroaluminum carboxylates equilibrates
When MeCN was used as a solvent, the corresponding
spectra of 1a, 1b, and 1d revealed a complete disappearance of
the resonance at 77 ppm and appearance of additional
resonances at −11 and −23 ppm (Figure 3c, Supporting
Information, Figures S1c and S2b) which indicates that MeCN
drives the transformations of the studied systems to a larger
number of ionic forms of as yet unidentified structure. Some
additional light on the character of possible species formed
provide the investigations involving dimethoxyethane (DME)
as a bidentate Lewis base. The addition of 4 molar equiv of
DME to a toluene solution of 1a, 1b, or 1d led to the
precipitation of the ionic complex [AlCl2(DME)2]+[AlCl4]−
(2DME) in high yield (the molecular structure was confirmed by
single-crystal X-ray diffraction, see Supporting Information,
Figure S7 and Table S2).
We have also revealed that in the presence of py-Me as a
significantly stronger Lewis base, the character of chloroalumi-
num carboxylate species formed highly depends on the reagents
molar ratio (Scheme 3). The addition of 1 equiv of py-Me to
the solutions of 1a, 1b, and 1d results in a disappearance of the
27Al resonances because of the parent dimeric forms and the
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Scheme 3
appearance of two sharp signals at 102 ppm and 0 ppm (see
Supporting Information, Figure S3 and S4) which likely
correspond to ionic species [(RCO2)2Al(py-Me)x]+[AlCl4]−
(2py‑Me). However, the use of an excess of py-Me in all
above-mentioned systems leads to the formation of a
dominating signal at 27 ppm which can be attributed to the
six-coordinate complex [Cl2Al(O2CR)(py-Me)2] (3) along with
significantly lower intensity resonances corresponding to ionic
forms.
To have a better view on the structure of products formed in
reactions of 1a−1d with Lewis bases, we performed separate
experiments in Schlenk tubes, and many efforts were made to
obtain well-defined crystalline aluminum carboxylate adducts
with the corresponding donor ligand.
However, only in the reaction involving py-Me and 1a or 1b
did we successfully isolated from the postreaction mixture
crystals of suitable quality for X-ray analysis. In both cases the
reactions afforded the six-coordinate molecular Lewis acid−
Figure 4. Molecular structures of (a) 3a and (b) 3b; hydrogen atoms
have been omitted for clarity. Selected bond lengths (Å) and angles
(deg): (a): Al1−Cl1, 2.232(1); Al1−Cl1′, 2.232(9); Al1−O1,
1.975(2); Al1−O1′, 1.975 (2); Al1−N1, 2.057(3); Al1−N2,
2.065(3); N1−Al1−N2, 174.1(1); O1−C1−O1′, 115.8(3); O1−
Al1−O2, 66.4(1); (b): Al1−Cl1, 2.249(1); Al1−Cl2, 2.214(1); Al1−
O1, 1.986(2); Al1−O2, 1.977(2); Al1−N1, 2.043(3); Al1−N2,
2.046(3); N1−Al1−N2, 170.2(1); O1−C1−O2, 115.7(3); O1−Al1−
O2, 65.9(1).
t
base adduct [Cl2Al(λ2-O2CR)(py-Me)2] (R = Ph (3a), Bu
(3b)) in high yield. The molecular structures of 3a and 3b
consist of discrete mononuclear units with the aluminum
centers in a distorted octahedral configuration (Figure 4). In
both cases, the carboxylate group acts as a symmetrical
chelating ligand (O−Al−O = 66.4(1)° or 65.9(1)° and O−
C−O = 115.8(3)° or 115.7(3)°, for 3a or 3b, respectively). The
pyridine ligands are mutually trans (N−Al−N = 174.1(1)° or
170.2(1)°, with coplanar aromatic rings, and the Cl1−Al−Cl1′
angle of 101.4(5)° or Cl1−Al−Cl2 angle of 100.1(5) for 3a or
3b, respectively. Both the Al−O = 1.975(1) Å or Al1−O1 =
1.986(2) Å and Al1−O2 = 1.977(2) Å, (for 3a or 3b) and the
Al−Cl (2.232(1) Å) or Al1−Cl1 = 2.249(1) Å and Al1−Cl1 =
2.214(1) Å (for 3a or 3b, respectively) distances are slightly
longer than those observed for the four-coordinate dimer 1a,
and the axial Al1−N1 distances are 2.057(3) or 2.043(3) and
Al1−N2 distances are 2.065(3) Å or 2.046(3) for 3a or 3b,
respectively. Compounds 3a and 3b represent unique examples
of monomeric aluminum carboxylates with a chelating
carboxylate ligand (structurally characterized analogous gallium
carboxylate was also reported very recently22). It is worthy to
note that our previous theoretical calculations on the relative
stability of various structures of the type 3 adducts confirmed
that the formation of the six-coordinate chelate structure is
thermodynamically preferred which is in agreement with the
experimental data.16
Interestingly, analysis of the crystal structure of 3a revealed
that the monomeric units self-assemble via C−Haliph···π and C−
Har···Cl interactions to produce two-dimensional (2D) grids,
which are further organized by complementary C−Har···O
interactions into a three-dimensional (3D) network with open
channels directed along the b axis (Figure 5). In contrast, the
analysis of the crystal structure of 3b revealed the self-
organization of [Cl2Al(λ2-O2CtBu)(py-Me)2] units into one-
Figure 5. Crystal packing diagrams for 3a, view along the (a) b axis
(stick model), (b) b axis (space-fill model), and (c) c axis (stick
model).
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dimensional (1D) chains stabilized by weak π···π-stacking
interactions between aromatic rings of 4-methylpyridine
(Figure 6) which results in a close packing of molecules
without empty spaces in the crystal lattice.
above show unambiguously that in the dichloroaluminum
carboxylate/H2O system complex transformations take place
which lead to the formation of various hydroxo- and
oxoaluminum clusters with bridging carboxylate ligands
depending on the character of carboxylate ligands and/or the
solvent used. These observations also indicate that the reaction
of dichloroaluminum carboxylates with water is a stepwise
process in which dinuclear hydroxoaluminum complexes can be
treated as intermediate species in transformations leading to
oxoaluminum clusters.
It is interesting to note that the central oxoaluminium core in
4 is retained upon addition of a pyridine-type ligand, as a strong
Lewis base, to a solution of 4 in THF and leads to the
formation of the corresponding [(Al3O)(O2CR)6(py-Me′)3]-
[AlCl4] (R = tBu, Ph) adduct (Scheme 5). However only in one
Scheme 5
Figure 6. Crystal packing diagrams for 3b, view along the (a) b axis
and (b) a axis.
Investigations on the Interaction of Dichloroalumi-
num Carboxylates with Water. Upon the addition of water
to dichloroaluminum carboxylates we expected a more
complicated situation to that observed in the reactions with a
Lewis base, as water molecules can act as both a neutral donor
ligand and a proton donor. However, in contrast to expectation,
these reactions appeared as a convenient method for the
synthesis of oxo- and hydroxoaluminum carboxylates.
case, that is, in the reaction involving 4b and 3-methylpyridine
(py-Me′), were we able to isolate almost quantitatively the ionic
complex [(Al3O)(O2CtBu)6(py-Me′)3][AlCl4] (4bpy‑Me′) as
large block-shaped crystals suitable for X-ray crystallography.
It is worthy to note that the same product was also obtained by
a direct reaction of 1b with water-py-Me′ mixture in toluene
(see Experimental Section).
The identity of the oxo- and hydroxoaluminum carboxylates
has been confirmed by X-ray crystallography. Compounds
4aTHF and 4bTHF are isostructural (the corresponding laurylate
derivative 4dTHF is an oily product), and the representative
molecular structure of 4aTHF is shown in Figure 7. The central
The reactions of 1a, 1b, and 1d with 0.33 equiv of water
carried out in THF-toluene mixture lead to oxoaluminum
carboxylates [(Al3O)(O2CR)6(THF)3][AlCl4] (4THF) (where
t
R = Ph (4aTHF), Bu (4bTHF), and C11H23 (4dTHF)) in high
yield (Scheme 4, path a). Surprisingly, when dichloroaluminum
Scheme 4. Reaction Outcomes of Dichloroaluminum
Carboxylates Hydrolysis Depending on the Character of the
Carboxylate Ligand and/or the Donor Solvent Used
acrylate 1c was reacted with water in THF under similar
conditions, the unprecedented example of the ionic chloro-
(hydroxo)aluminum carboxylate [(ClAl)2 (OH)-
(O2CC2H3)2(THF)4][AlCl4] (5) was isolated as a main
product (Scheme 3, path b). In another control experiment
we have investigated the influence of the solvent used on the
hydrolysis reactions outcome. When the hydrolysis of 1b was
carried out in MeCN as a solvent the ionic aluminum hydroxide
[Al2(OH)(O2CtBu)2(MeCN)6][AlCl4)3] (6) was isolated as
the main product (Scheme 4, path b). The results described
Figure 7. Molecular structure of the cationic part of 4aTHF; hydrogen
atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (deg): O1−Al1, 1.821(3); O1−Al2, 1.823(3); O1−Al3,
1.817(3); Al1−O14, 2.002(4); Al2−O15, 1.987(4); Al3−O16,
1.990(3); Al1−O1−Al2, 120.2(2); Al1−O1−Al3, 120.0(2); Al2−
O1−Al3, 119.8(2).
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Al3O core of the cationic unit in both compounds consists of a
planar triangular arrangement of aluminum atoms where the
Al−O−Al angles are close to 120°. Each aluminum center
possesses a slightly distorted octahedral coordination sphere.
The mean Al−(μ3-O) distance is 1.853 Å, and the Al−O
(carboxylate) bond length (av. 1.892 Å) is smaller than that of
Al−O (THF) (1.948(3) Å). The coordination sphere of the
aluminum center in the anion has a slightly distorted
tetrahedral environment. Analysis of the crystal structures of
4aTHF and 4bTHF revealed that molecules are organized through
noncovalent interactions into microporous structures with slit-
like pores along crystallographic b and a axes respectively;
however, larger apertures are present in the former compound
(Supporting Information, Figure S5). Compound 4bpy‑Me′
crystallizes in the monoclinic P21/c space group and is
isostructural with the previously described ionic complex
4bTHF (Figure 8). Only minor differences in bond lengths
Figure 9. Molecular structure of the cationic part of 5; hydrogen
atoms have been omitted for clarity. Selected bond lengths (Å) and
angles (deg): O5−Al1, 1.825(1); O5−Al2, 1.823(1); Al1−Cl1,
2.259(5); Al2−Cl2, 2.270(5); Al1−O5−Al2, 125.8(6); O5−Al1−
Cl1, 94.3(3); O5−Al1−Cl2, 93.6(3).
Figure 8. Molecular structure of 4bpy‑Me′; hydrogen atoms and methyl
groups of tBu have been omitted for clarity. Selected bond lengths (Å)
and angles (deg): O1−Al1, 1.819(4); O1−Al2, 1.827(4); O1−Al3,
1.820(4); Al1−N1, 2.096(5); Al2−N2, 2.102(5); Al3−N3, 2.103(5);
Al1−O1−Al2, 119.7(2); Al1−O1−Al3, 120.7(2); Al2−O1−Al3,
119.6(2).
Figure 10. Molecular structure of the cationic part of compound 6;
hydrogen atoms have been omitted for clarity. Selected bond lengths
(Å) and angles (deg): O1−Al1, 1.819(2); O1−Al2, 1.821(2); Al1−
O2, 1.857(2); Al1−O4, 1.860(2); Al1−N1, 2.000(3); Al2−N4,
2.003(3);Al1−O1−Al2, 121.5(1); O1−Al1−O2, 94.5(1); O1−Al1−
O4, 95.1(1); O1−Al1−N2, 177.1(1); O1−Al2−N5, 178.6(1).
can be observed for Al−Npy‑Me and Al−OTHF distances whose
mean values are 2.100 Å and 1.991 Å, respectively. The angles
around the central oxygen atom remain unchanged; therefore,
the effect of a Lewis base strength on the geometry of the
Al3O(O2CR)6 core is very weak.
Compound 5 crystallizes in the monoclinic P21/c space
group (Figure 9). The cationic unit consists of two six-
coordinate aluminum atoms which are bridged by two acrylate
ligands and a hydroxo μ2-OH group. Each of the aluminum
atoms is bonded to chloride ligands with a mean Al−Cl
distance of 2.264 Å and additionally coordinated by two THF
molecules. It is worthy to note that the O5 oxygen atom from
[Al2(OH)(O2C3H3)3(THF)4]+ cation forms an intermolecular
hydrogen bond with additional THF molecule, where O5−
H50···O10 distance is 2.734 Å.
Compound 6 crystallizes in the monoclinic P21/c space
group with one [Al2(OH)(O2CtBu)2(MeCN)6]3+ cation and
three AlCl4− anions in the unit cell (Figure 10). The cation
represents an idealized 2-fold symmetry and contains two six-
coordinated aluminum atoms, which are connected by a
bridging μ2-OH hydroxide anion and two bridging carboxylate
ligands. The octahedral coordination sphere of aluminum
cations is completed by three acetonitrile molecules. This
structural motif is analogous to that previously observed in the
[Al2(μ-CH3CO2)2(μ-OH)(CH3CO2C2H5)6][AlCl4]3 aggre-
gate.23 The more detailed analysis of the crystal structure
indicated that, similarly as in compound 5, the hydroxo group is
involved in the formation of the intermolecular O−H···N
hydrogen bond with an additional acetonitrile molecule, where
the O1−H1···N7 distance is 2.758 Å.
CONCLUSIONS
■
In conclusion, the study has revealed a complex nature of
chloroaluminum carboxylate complexes featuring both molec-
ular and ionic forms with different coordination numbers of the
metal center and various coordination modes of the carboxylate
ligand. The data clearly indicate that the relative concentration
of neutral and ionic species of dichloroaluminum carboxylates
and their association degree in solution strongly depend on the
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Inorganic Chemistry
Article
mmol) in CH2Cl2 (5 mL) was added DME (0.360 g, 4.0 mmol). Large
block-shaped colorless crystals were obtained quantitatively from
CH2Cl2 at 0 °C after 2 h. Elemental analysis (%) calcd for
C8H20Al2Cl6O4: C 21.50, H 4.51, Al 12.07, Cl 47.60; found: C
21.44, H 4.45, Al 12.11, Cl 47.54. 27Al NMR (DME): δ = 24.0, 102,1.
IR (Nujol, cm−1): 487; 855; 1006; 1063; 1187; 1248; 1287; 1376;
1454.
character of the carboxylate ligand, and a more lipophilic ligand
bearing a long alkyl chain stabilizes the dimeric form with
bridging carboxylate ligands. Upon addition of Lewis bases of
moderate strength the molecular form of dichloroaluminum
carboxylates equilibrates with new ionic forms. Particularly
intriguing was the use of 4-methylpyridine as a strong base
which allowed for the isolation and structure characterization of
the six-coordinate molecular Lewis acid−base adducts [Cl2Al-
(λ2-O2CR)(py-Me)2] with a chelating carboxylate ligand.
Furthermore, the investigations on the interaction of
dichloroaluminum carboxylates with water show that these
reactions proceed via complex pathways affording various oxo-
and hydroxoaluminum complexes with bridging carboxylate
ligands. Finally, the data promise greater tuning of trans-
formation involving aluminum carboxylates toward desired
molecular units and may be vital for a better understanding of
how water and donor solvents can affect the prototypical Al-
MOF structure.
Synthesis of [Cl2Al(λ2-O2CPh)(py-Me)2] (3a). To a solution of 1a
(0.438 g, 1.0 mmol) in CH2Cl2 (5 mL) was added py-Me (0.372 g, 4.0
mmol). Large block-shaped colorless crystals were obtained from
CH2Cl2/toluene mixture crystallized at 0 °C. The isolated yield: 0.778
g (96%). 3a is soluble in THF, CH2Cl2, and poorly soluble in aromatic
solvents. Elemental analysis (%) calcd for C19H19AlCl2N2O2: C 56.31,
H 4.73, Al 6.66, Cl 17.50, N 6.91; found: C 56.35, H 4.78, Al 6.60, Cl
1
17.55, N 6.98. H NMR (CDCl3): δ = 2.40 [sb, 6H, CH3], 7.25 [mb,
6H, CHAr], 7.48 [mb, 1H, CHAr], 7.81 [mb, 1H, CHAr], 7.90 [mb, 1H,
CHAr], 8.70 [mb, 2H, CHAr], 9.09 [mb, 2H, CHAr]; 27Al NMR
(CDCl3): δ = 0.2, 26.9, 102.0. IR (cm−1): 519; 558; 687; 699; 731;
813; 894; 1036; 1060; 1071; 1078; 1104; 1171; 1209; 1234; 1262;
1306; 1339; 1378; 1451; 1506; 1563; 1575; 1592; 1602; 1627.
Synthesis of [Cl2Al(λ2-O2CtBu)(py-Me)2] (3b). A similar
procedure as for 3a using 1b (0.398 g, 1.0 mmol) and py-Me (0.372
g, 4.0 mmol) as reagents. The isolated yield: 0.709 g (92%). Elemental
analysis (%) calcd for C17H23AlCl2N2O2: C 53.00, H 6.02, Al 7.00, Cl
EXPERIMENTAL SECTION
■
All materials were purified, stored, and used under a dry nitrogen
atmosphere. Toluene and tetrahydrofuran were distilled from
sodium−potassium alloy and benzophenone. Acetonitrile was distilled
from P2O5. EtAlCl2 (1.8 M in toluene, Aldrich) was used as received.
NMR spectra were recorded on a Varian Mercury-400 spectrometer;
IR spectra were recorded on FTIR Perkin-Elmer System 2000.
Synthesis of [Cl2AlO2CPh]2 (1a). A solution of benzoic acid
(1.196 g, 9.8 mmol) in CH2Cl2 (6 mL) was cooled to −78 °C, and a
solution of MeAlCl2 in hexane (9.8 mL of 1 M solution in hexane, 9.8
mmol) was added dropwise. Then the reaction mixture was warmed to
room temperature and stirred for 2 h. Small rhombic colorless crystals
were obtained from CH2Cl2/hexane mixture crystallized at 0 °C
overnight. The isolated yield: 1.932 g (90%). Elemental analysis (%)
calcd for C7H5AlCl2O2: C 38.39, H 2.30, Al 12.32, Cl 32.38; found: C
38.46, H 2.37, Al 12.25, Cl 32.31. 1H NMR (CDCl3): δ = 7.63 [m, 2H,
CHAr], 7.87 [m, 1H, CHAr], 8.27 [m, 2H, CHAr]; 27Al NMR (CDCl3):
δ = 2.0, 77.0, 91.0, 102.0. IR (Nujol, cm−1): 560; 677; 715; 1376; 1452;
1495; 1566; 1598; 1618.
1
18.40, N 7.27; found: C 52.92, H 6.05, Al 6.93, Cl 18.35, N 7.21. H
NMR (CDCl3): δ = 1.01 [s, 9H, (CH3)3CCO2], 2.68 [s, 6H, CH3],
7.78 [d, 4H, CHAr], 8.64 [d, 4H, CHAr]; 27Al NMR (CDCl3): δ = 0.2,
27.0, 102.0. IR (Nujol, cm−1): 509; 561; 625; 725; 818; 1036; 1067;
1213; 1233; 1377; 1455; 1502; 1518; 1562; 1626.
Synthesis of [Al3O(O2CPh)6(THF)3][AlCl4] (4aTHF). To a toluene
solution of 1a (1.314 g, 3.0 mmol), water (0.018 g, 1.0 mmol) in THF
(2 mL) was added, and the reaction mixture was stirred for 12 h.
Colorless crystals suitable for X-ray analysis were isolated from the
postreaction mixture after storage at −5 °C. The isolated yield: 0.919 g
(76%). Elemental analysis (%) calcd for C54H54Al4Cl4O16: C 53.66, H
1
4.50, Al 8.93, Cl 11.73; found: C 53.60, H 4.45, Al 8.89, Cl 11.70. H
NMR (CDCl3): δ = 2.12 [4H, s, (CH2CH2)2O], 4.49 [4H, s,
(CH2CH2)2O], 7.42 [2H, m, CHAr], 7.52 [1H, s, CHAr], 8.01 [2H, s,
CHAr], 27Al NMR (CDCl3): δ = 2.4, 102.3. IR (cm−1): 464; 554; 656;
698; 746; 868; 1010; 1090; 1263; 1443; 1520; 1556; 1581; 1610;
2904; 2965; 3059; 2500−3500(w).
Synthesis of [Al3O(O2CtBu)6(THF)3][AlCl4] (4bTHF). To a toluene
solution of 1b (1.194 g, 3.0 mmol), water (0.018 g, 1.0 mmol) in THF
(2 mL) was added, and colorless crystals suitable for X-ray analysis
were isolated from the postreaction mixture after storage at 4 °C. The
isolated yield: 0.751 g (69%). Elemental analysis (%) calcd for
C42H78Al4Cl4O16: C 46.33, H 7.22, Al 9.91, Cl 13.02; found: C 46.27,
H 7.18, Al 9.85, Cl 13.06. 1H NMR (CDCl3): δ = 1.11 [9H, s,
(CH3)3C], 1.96 [4H, s, (CH2CH2)2O], 4.12 [4H, s, (CH2CH2)2O];
27Al NMR (CDCl3): δ = 0.2, 104.1; 13C NMR 25.0, 27.3, 39.8, 70.3,
185.8. IR (cm−1): 432; 489; 515; 541; 631; 711; 801; 891; 917; 1042;
1241; 1369; 1392; 1450; 1495; 1639; 2872; 2933; 2969.
Synthesis of [Cl2AlO2CtBu]2 (1b). A slightly modified procedure
as for 1a; a toluene solution of pivalic acid (1.000 g, 9.8 mmol) was
added dropwise to a solution of EtAlCl2 in toluene (5.4 mL, 1.8 M) at
−78 °C under nitrogen atmosphere. The reaction mixture was allowed
to warm up to room temperature. Crystals of 1b were isolated from
the concentrated postreaction mixture at 0 °C after 24 h. The isolated
yield: 1.677 g (86%). Elemental analysis (%) calcd for C5H9AlCl2O2:
C 30.18, H 4.56, Al 13.56, Cl 35.63; found: C 30.14, H 4.50, Al 13.46,
1
Cl 35.56. H NMR (CDCl3): δ = 1.37 [s, 12H, (CH3)3CCO2]; 27Al
NMR (CDCl3): δ = 2.0; 77.0; 91.0; 101.9. IR (Nujol, cm−1): 542; 607;
690; 787; 1038; 1235; 1377; 1460; 1493; 1575.
Synthesis of [Al3O(O2CtBu)6(py-Me′)3][AlCl4] (4bpy‑Me′). Proce-
dure A: to a toluene solution of 4bTHF (0.544 g, 0.5 mmol) 3-picoline
(0.140 g, 1.5 mmol) was added, and colorless crystals were isolated
from a concentrated postreaction mixture. The isolated yield: 0.358 g
(62%). Procedure B: to a toluene solution of 1b (1.194, 3.0 mmol)
water (0.018 g, 1.0 mmol) in 3-picoline (2 mL) was added, and
colorless crystals of 4bpy‑Me′ suitable for X-ray analysis were isolated
from the postreaction mixture stored at 4 °C. The isolated yield: 0.855
g (74%). Elemental analysis (%) calcd for C48H75Al4Cl4N3O13: C
50.05, H 6.56, Al 9.37, Cl 12.31, N 3.65; found: C 50.01, H 6.52, Al
9.32, Cl 12.27, N 3.61. 1H NMR (CDCl3): δ = 1.05 [9H, s, (CH3)3C],
2.42 [3H, s, CH3C5H4N], 7.10−8.90 [4H, m, CHAr]; 27Al NMR
(CDCl3): δ = 2.1, 102.1; 13C NMR (CDCl3): δ 18.6, 27.2, 39.6,
123.0−149.6, 186.1. IR (cm−1): 422; 477; 480; 512; 612; 695; 714;
795; 823; 1045; 1071; 1122; 1209; 1238; 1366; 1389; 1443; 1491;
1629; 2872; 2927; 2965; 3094.
Synthesis of [Cl2AlO2CC2H3]2 (1c). A similar procedure as for 1b
using acrylic acid (1.960 g, 9.8 mmol) and EtAlCl2 in toluene (5.4 mL,
1.8 M). All volatile compounds were removed under vacuum, and a
white powder was obtained. Recrystallization from concentrated
toluene solution afforded 1c as a polycrystalline product. The isolated
yield: 1.408 g (85%). Elemental analysis (%) calcd for C3H3AlCl2O2:
C 21.33, H 1.79, Al 15.97, Cl 41.97; found: C 21.26, H 1.84, Al 15.90,
Cl 41.92.
Synthesis of [Cl2AlO2CC11H23]2 (1d). A similar procedure as for
1b using lauric acid (1.960 g, 9.8 mmol) and EtAlCl2 in toluene (5.4
mL, 1.8 M). The product 1d was isolated as an orange-colored viscous
liquid. Elemental analysis (%) calcd for C12H23AlCl2O2: C 48.50, H
7.80, Al 9.08, Cl 23.86; found: C 48.42, H 7.86, Al 9.14, Cl 23.91. 27Al
NMR (CDCl3): δ = 77.0. IR (cm−1): 516; 549; 693; 718; 1066; 1118;
1326; 1461; 1565; 2850; 2920; 2950, IR (benzene, cm−1): 464; 524;
564; 692; 1028; 1080; 1120; 1376; 1392; 1488; 1572.
Reaction of 1a, 1b, 1d with DME (2DME). To a solution of 1a
(0.438 g, 1.0 mmol), 1b (0.398 g, 1.0 mmol), or 1d (0.594 g, 1.0
Synthesis of [Al2(OH)Cl2(O2CCHCH3)2(THF)4][AlCl4] (5). To a
toluene solution (10 mL) of 1c (1.014 g, 3.0 mmol), water (0.018 g,
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Inorganic Chemistry
Article
1.0 mmol) in tetrahydrofuran (2 mL) was added slowly under
vigorous stirring. Colorless crystals of 5 suitable for X-ray analysis were
isolated from the concentrated postreaction mixture after storage at 4
°C. Yield: 0.415 g (56%). Elemental analysis (%) calcd for
C22H39Al3Cl6O9: C 35.65, H 5.30, Al 10.92, Cl 28.70; found: C
35.61, H 5.22, Al 10.86, Cl 28.62. 1H NMR (CDCl3): δ = 1.99 [4H, s,
(CH2CH2)2O], 4.13 [4H, s, (CH2CH2)2O], 5.87 [1H, dd,
CHaHbCHCOO], 6.06 [1H, dd, CHaHbCHCOO], 6.29 [1H, dd,
CHaHbCHCOO]; 27Al NMR (CDCl3): δ = 1.2, 102.1. IR (cm−1): 489;
541; 624; 663; 692; 721; 798; 839; 878; 923; 984; 1023; 1080; 1263;
1379; 1462; 1594; 1613; 1655; 1668; 2885; 2914; 2963; 2650−
3500(w).
3b: C17H23AlCl2N2O2: M = 385.25, monoclinic, space group C2/c
(no. 15), a = 10.3121(10) Å, b = 27.225(3) Å c = 14.6991(15) Å, β =
92.602(6)°, U = 4122.4(7) Å3, Z = 8, F(000) = 1616, Dc = 1.241 g m3,
T = 100(2) K, θmax = 21.94°, μ(Mo−Kα) = 0.369 mm−1, 2478 unique
reflections.. Refinement converged at R1 = 0.0597, wR2 = 0.1074 for
all data and 247 parameters (R1 = 0.0451, wR2 = 0.1023 for 2060
reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.058. The residual electron density = +0.84/−0.66 e Å−3.
4aTHF: C H Al Cl O : M = 1378.54, triclinic, space group P1 (no.
̅
56 58
4
8
16
2), a = 14.3681(3) Å, b = 14.7009(3) Å, c = 20.8981(4) Å, α =
99.2950(10)°, β = 102.4920(10)°, γ = 116.0590(10)°, U =
3702.24(14) Å3, Z = 2, F(000) = 1420, Dc = 1.237 g m3, T =
100(2) K, θmax = 23.26°, μ(Mo−Kα) = 0.407 mm−1, 10502 unique
reflections. Refinement converged at R1 = 0.0949, wR2 = 0.2061 for all
data and 778 parameters (R1 = 0.0847, wR2 = 0.1748 for 8861
reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.028. The residual electron density = +0.92/−0.88 e Å−3.
Synthesis of [Al2(OH)(O2CtBu)2(MeCN)6][AlCl4]3 (6). To a
toluene solution (10 mL) of 1b (1.194 g, 3.0 mmol), water (0.018
g, 1.0 mmol) in acetonitrile (2 mL) was added slowly, and this reaction
mixture was stirred for 2 h. Colorless crystals of 6 suitable for X-ray
analysis were isolated from the concentrated postreaction mixture after
storage at 0 °C. Yield: 0.605 g (59%). Elemental analysis (%) calcd for
C22H37Al5Cl12N6O5: C 25.76, H 3.64, Al 13.15, Cl 41.47, N 8.19;
found: C 25.70, H 3.60, Al 13.11, Cl 41.42, N 8.13. 1H NMR
(CDCl3): δ = 1.12 [9H, s, (CH3)3CCO2], 2.09 [3H, s, CH3CN]; 27Al
NMR (CDCl3): δ = 0.5, 87,1, 102.2. IR (cm−1): 798; 952; 1026; 1096;
1234; 1263; 1379; 1456; 1495; 1591; 2307; 2338; 2854 2927; 2959;
2500−3500(w).
Crystallographic Data. The data were collected at 100(2) K on a
Nonius Kappa CCD diffractometer24 using graphite monochromated
MoKα radiation (λ = 0.71073 Å). The unit cell parameters were
determined from ten frames, then refined on all data. The data were
processed with DENZO and SCALEPACK (HKL2000 package).25
The structure was solved by direct methods using the SHELXS9726
program and was refined by full matrix least−squares on F2 using the
program SHELXL97.27 All non-hydrogen atoms were refined with
anisotropic displacement parameters. The hydrogen atoms were
introduced at geometrically idealized coordinates with a fixed isotropic
displacement parameter equal to 1.5 (methyl groups) times the value
of the equivalent isotropic displacement parameter of the parent
carbon. Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
nos. CCDC 737314 (1a), CCDC 843886 (2DME), CCDC 737315
(3a), CCDC 843888 (3b), CCDC 843889 (4aTHF), CCDC 843890
(4bpy‑Me), CCDC 843887 (4bTHF), CCDC 843891 (5), CCDC
843892 (6). Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB21EZ, U.K. (fax:
(+44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
4bpy‑Me: C48H75Al4Cl4N3O13: M = 1151.83, monoclinic, space group
P21/c (no. 14), a = 11.3611(4) Å, b = 23.7589(9) Å, c = 24.7769(10)
Å, β = 107.126(2)°, U = 6391.4(4) Å3, Z = 4, F(000) = 2432, Dc =
1.197 g m3, T = 100(2) K, θmax = 21.97°, μ(Mo−Kα) = 0.295 mm−1,
7660 unique reflections. Refinement converged at R1 = 0.0855, wR2 =
0.1872 for all data and 720 parameters (R1 = 0.0688, wR2 = 0.1661 for
6200 reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.045. The residual electron density = +0.92/−0.88 e Å−3.
4bTHF: C46H82Al4Cl4O17: M = 1156.84, This compound crystallizes
as twins, triclinic, space group P1 (no. 2), a = 13.0010(9) Å, b =
̅
12.9510(9) Å, c = 18.4270(13) Å, α = 83.870(4)°, β = 78.589(4)°, γ =
83.782(4)°, U = 3011.8(4) Å3, Z = 2, F(000) = 1228, Dc = 1.276 g m3,
T = 100(2) K, θmax = 23.26°, μ(Mo−Kα) = 0.316 mm−1, 5028 unique
reflections. The goodness-of-fit on F2 was equal to 1.066.
5: C26H47Al3Cl6O10: M = 813.28, monoclinic, space group P21/c
(no. 14), a = 15.4156(11) Å, b = 14.1660(10) Å, c = 22.3022(14) Å, β
= 128.659(4)°, U = 3803.1(5) Å3, Z = 4, F(000) = 1696, Dc = 1.420 g
m3, T = 99(2) K, θmax = 30.00°, μ(Mo−Kα) = 0.569 mm−1, 11092
unique reflections. Refinement converged at R1 = 0.0382, wR2 =
0.0786 for all data and 410 parameters (R1 = 0.0303, wR2 = 0.0861 for
9549 reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.048. The residual electron density = +1.00/−0.51 e Å−3.
6: C24H40Al5Cl12N7O5: M = 1066.93, monoclinic, space group P21/
c (no. 14), a = 13.2971(4) Å, b = 19.4679(6) Å, c = 20.4001(6) Å, β =
103.408(2)°, U = 5137.0(3) Å3, Z = 4, F(000) = 2168, Dc = 1.380 g
m3, T = 100(2) K, θmax = 24.41°, μ(Mo−Kα) = 0.769 mm−1, 8302
unique reflections. Refinement converged at R1 = 0.0658, wR2 =
0.1053 for all data and 530 parameters (R1 = 0.0500, wR2 = 0.0993 for
6847 reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
to 1.065. The residual electron density = +0.62/−0.49 e Å−3.
1a: C H Al Cl O : M = 437.98, triclinic, space group P1 (no. 2), a
̅
14 10
2
4
4
= 7.1889(3) Å, b = 8.6829(3) Å c = 8.9185(4) Å, α = 113.518(2)°, β =
112.421(2)°, γ = 93.641(2)°, U = 456.33(3) Å3, Z = 1, F(000) = 220,
Dc = 1.594 g m3, T = 100(2) K, θmax = 24.10°, μ(Mo−Kα) = 0.760
mm−1, 1442 unique reflections. Refinement converged at R1 = 0.0826,
wR2 = 0.1779 for all data and 263 parameters (R1 = 0.0691, wR2 =
0.1576 for 1314 reflections with Io > 2σ(Io)). The goodness-of-fit on
F2 was equal to 0.998. The residual electron density = +0.60/−0.50 e
Å−3.
ASSOCIATED CONTENT
■
S
* Supporting Information
Additional 27Al NMR data, X-ray crystallographic files in CIF
format, molecular figures and bond length/bond angle tables
for compounds 1a, 2DME, 3a, 3b, 4aTHF, 4bTHF, 4bpy‑Me′, 5, and
6. This material is available free of charge via the Internet at
http://pubs.acs.org.
2DME: C8H20Al2Cl6O4: M = 446.90, orthorhombic, space group
Pbcm (no. 57), a = 6.7311(2) Å, b = 14.7242(4) Å c = 19.1681(6) Å,
U = 1899.75(10) Å3, Z = 4, F(000) = 912, Dc = 1.563 g m3, T =
100(2) K, θmax = 27.46°, μ(Mo−Kα) = 1.002 mm−1, 2239 unique
reflections. Refinement converged at R1 = 0.0374, wR2 = 0.0812 for all
data and 98 parameters (R1 = 0.0329, wR2 = 0.0787 for 2048
reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.124. The residual electron density = +0.86/−0.35 e Å−3.
3a: C19H19AlCl2N2O2: M = 405.24, monoclinic, space group P21/m
(no. 11), a = 10.5831(6) Å, b = 10.9003(8) Å, c = 11.1279(9) Å, β =
115.451(4)°, U = 1159.12(16) Å3, Z = 2, F(000) = 420, Dc = 1.161 g
m3, T = 100(2) K, θmax = 24.11°, μ(Mo−Kα) = 0.331 mm−1, 1941
unique reflections. Refinement converged at R1 = 0.0470, wR2 =
0.0886 for all data and 133 parameters (R1 = 0.0404, wR2 = 0.0861 for
1707 reflections with Io > 2σ(Io)). The goodness-of-fit on F2 was equal
1.093. The residual electron density = +0.27 /− 0.22 e Å−3.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: evala@ch.pw.edu.pl (Z.F.), lewin@ch.pw.edu.pl (J.L.);
Web-site: http://lewin.ch.pw.edu.pl (J.L.). Fax: (+48) 22-
2347279.
ACKNOWLEDGMENTS
■
This work was supported by the Ministry of Science and
Higher Education (N N204 128037) and European Union in
the framework through the Warsaw University of Technology
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Article
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ey, G.; Burghammer,
Development Programme of ESF (WB) and Warsaw University
of Technology.
(15) (a) Powell, A. K.; Heath, S. L. Coord. Chem. Rev. 1996, 149, 59−
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