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Insertion of Functional Groups into Square-Planar Units A New Construction Principle for Open Microporous Framework Structures.

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Data collection was carried out on a Siemens Platform goniometer with a C C D
detector at 205(2) K using Mo,, radiation (i
= 0.71073 A). 11621 reflections
were collected over the range - 17 I h 5 15, - 11 I k I l l , and - 21 5 1 1 2 0 , of
which 4331 were unique (R,,, = 0.0434). Corrections applied: Lorentz-polarization, extinction (0.0045(12)), and absorption (semiempirical, 7& and T,,,
were 0 1766 and 0.1342, respectively). The structure was solved by direct methods i n conjunction with standard difference Fourier techniques. Least squares
refinement based upon F z converged with residuals of R , = 0.0756,
wR, = 0.2121. and GOF ~ 1 . 1 7 7based upon 1>2o(I). All non-hydrogen
atoms were refined anisotropically and hydrogen atoms were placed in calculated (d(C--H) = 0.96 A) positions. The largest peak and hole in the difference
map were 3.079 and - 0 . 4 3 7 e k 3 , respectively [28].
1241 J. R. Dilworth, J. Zubieta. Inorg. Synth. 1986, 24, 193.
[25] R. Poli. H. D. Mui, J Am Chem. Soc 1990, f f 2 ,2446.
[26] P Hofacker. C Friebel, K. Dehnicke, P. Bauml, W. Hiller, J. Strahle, Z .
Nulurfi)rsch. B 1989, 44, 1161.
[27] I. Ugi, H. Perlinger, L. Behringer, Chem. Ber. 1958, P i , 2330.
[28] Further details of the crystal structure investigations may be obtained from the
Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen
(Germdny). on quoting the depository number CSD-405951 (17), CSD-405952
(7) and CSD-409593 (13/14 cocrystal).
Insertion of Functional Groups into
Square-Planar Units:
A New Construction Principle for
Open Microporous Framework Structures
Michael Schindler* and Werner H. Baur*
Currently 98 different topologies of microporous frameworks
are known,"] most of which are based on variously bridged
coordination tetrahedra of oxygen atoms around aluminum,
phosphorus, and silicon centers. Much current synthetic work
involving related phases is devoted to incorporating reactive
transition metals into these frameworks and to devising compounds with larger pores accessible to larger molecules. The aim
of this work is to increase the potential usefulness of such microporous compounds for catalytic applications.
Recently three phases were synthesized that combine the presence of a reactive transition metal with an accessible pore space;
these phases are thermally reasonably stable, re- and dehydrate
reversibly, and are capable of exchanging cations located in the
pore space: Frankfurt vanadium phosphate one (FVP-1) 1['1
(with 2 . 8 1 ~ 1 4 . 0 -0.1
< w , < l . l , 0 5 ~ 5 0 . 2 01y<2.1,
7 1 2 1 10) as well as compounds 213]and 3.[31At first sight the
1 ,)O,}(PO,),I.(PO,);(OH);zH,O
CS,[V,O,(PO,),]. IH,O
architecture of these compounds seems to be based on different
principles from those applicable to zeolite frameworks. However, on closer inspection it appears that different chemical compositions require an extension of these principles.
The exciting chemistry and topology of the bonding arrangements in vanadates and related materials has merited two recent
reviews.l4]While many of these phases are based on the principle
of heteropolyions of the Keggin type,"] (i.e. these clusters do
not form strong bonds outside the molecule) the units of 1-3
[*] M. Schindler, Prof. Dr. W. H. Baur
Institut fur Kristallographie und Mineralogie der Universitdt
Senckenberganlage 30, D-60054 Frankfurt am Main (Germany)
Fax: Int. code +(69)798 22101
e-mail . Baur(u
AnRew. Chem. Inr. Ed. Engl. 1997, 36, No. 112
are what we denote as anti-Keggin groups (composition
[(V~f,V~~,)O,](PO,),, with -0.1 s w s l.l),~'l in which the
phosphate tetrahedra are outside of the shells of vanadium coordination polyhedra and are, therefore, able to form bridges between neighboring groups. Each of these V,O,(PO,),
V,P,O, 7) groups is composed of five square-pyramidally O-coordinated V atoms and four PO, groups (Figure 1). The central
Figure I . Two bridged spiked helmet V,O,(PO,), units (top) iis well as two joined
square-planar building blocks (bottom), which could, for example, represent two
single four-rings (S4R) or two square-planar coordination polyhedra of 0 around
Nb. The circles denote the connectors to neighboring groups. An individual
V,O,(PO,), group consists of four connectors, in this case phosphate tetrahedra,
and a central square-pyramidal coordination around V 5 + , which shares all its basal
edges with the surrounding square-pyramidal coordination polyhedron around
V 4 + . The symmetry of one spiked helmet V,O,(PO,), unit is 4mm.
vanadyl oxygen atom is bonded to a V5+ ion, its position on the
hemispherical-shaped group is reminiscent of the spike on a
spiked helmet.['' However, in a topological sense the vanadium
coordination polyhedra are only decoration. The active parts of
the group are the phosphate tetrahedra that connect the planar
square groups at their corners after twists of about 90" (Figure 1). Thus, we must initially consider nets composed of
square-planar groupings.
As far as we know, nets of bonds have not been studied from
this viewpoint. However, studies by Wells[61and Smith"] include useful information on this topic. We consider our basic
building units to be four-connected square-planar groups,
which can differ considerably in terms of their chemistry and
size. Thus, the planar four-coordinations of oxygen atoms
around Nb (and Nb around 0) yield in one topology the NbO
crystal structure typers1 (Figure 2a and Table I ) , and single
four-rings (S4R) of silicate tetrahedra Si,O,O,,, yield within the
NbO framework the crystal structure of the zeolite sodalite[']
(Figure 2b and Table 1). By connecting the squares we can obtain either the framework of 1 (and 3) with the spiked helmet
unit as the building block (Figure 2c, Table 1) or the framework
of 4"01 (not illustrated) with the square-planar Mo,O,(PO,),
group as the building block. The central part of this group
consists of a Mo,O:+ cube with four molybdenyl (Mo=O)
groups and two Mo-Mo bonds; that is, it is chemically completely different from the vanadium phosphate groups in 1 and
3 but the connectivity properties of both groups are identical.
Thus, we know four frameworks, which are constructed by con-
VCH Verlagsgesellschaff mhH. D-6Y451 Weinheim, 1Y97
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Figure 3. a) The underlying net of %RHOtopology (viewed approximately parallel
to [loo]) for zeolite rho: two of the ts chains are highlighted; b) a ring of four spiked
helmet V,O,(PO,),
units i n 2, which is equivalent to a double eight-ring (DSR) in
zeolite rho.
Figure 2. The underlying nets of the aSOD topologies (viewed approximately parallel to [OOl]): a) NbO-type: Nb and 0 are represented by circles of the same size:
b) sodalite: the tetrahedral centers are indicated by small circles. two of the twisted
ts chains are highlighted; c ) polyhedral representation of the framework of 1: the
spiked helmet V,09(P0,), units are shown in one of their possible onenrations.
Table I Frameworks classified as belonging to the aSOD, orRHO. and aMER
general topologies ofconnecting square-planar building units. The chemical compositions apply only to the frameworks themselves, not to the pore contents of the
correspondingcompounds. Compound 3, the ordered counterpart of 1,belongs also
to the @SODtype of net, but crystallizes in the space group F&m.
cell constants [A]
space group
cell constants [A]
FD [a1
space group
zeolite rho
zeolite W
A ~ I O S ~ Z ~ O ~ ~
14.09, 14.20, 10.04
25.5, 25.5, 18 1
cell constants [A]
FD [a]
space group
[a] FD
number of cations per 1000 A'.
nections of square-planar units, that are based on an a-type
sodalite framework. Therefore, we adopted the code aSOD, in
order to distinguish it from the symbol for SOD type topology
employed for zeolites.['] The topological relationship between
the NbO-type and the SOD-type nets['] had already been recognized by Wells (see p. 29 in reference [6J). A necessary, but
possibly insufficient condition for a zeolite framework to be the
basis of a net composed of square units is the presence of infinite
chains of four-rings within the three-dimensional nets. These are
obtained by extending the dimers given in Figure 1 into chains
(Figure 2b). Smith calls these the ts chains.[71They occur in a
number of frameworks derived from the planar 4.82 net."]
The same type of relationship that was recognized between
the SOD-type net"' and the V,O,(PO,), framework of 1 exists
between the net of zeolite rho["] and the V,O,(PO,), frame92
work of 2['] (Table 1 , Figure 3): the S4R of (Si,Al)-tetrahedra
are replaced by the spiked helmet V,O,(PO,), groups. The relationship can be pictured by realizing that four V,O,(PO,), units
replace each double eight-ring (D8R) of (Si,Al)-tetrahedra in
zeolite rho (Figure 3b). The comparison of the unit cell lengths
of the vanadium phosphates and the aluminosilicates shows that
the linear dimensions of the square-planar V,O,(PO,), unit are
about 1.8 times larger than those of a S4R Si,O,OSiz unit; thus,
their pore space is larger. The framework density of zeolites is
expressed as the number of tetrahedral cations per 1000 A3. The
number of V and P atoms per I O O O A ' is only 60% of the
number of A1 and Si atoms per 1000 A3 for the aSOD and the
aRHO net types (Table 1). However, these numbers cannot be
compared directly, because in the aluminosilicates there are two
0 atoms per cation, while in the vanadium phosphates there are
2.43 0 atoms per cation. The most open fully crosslinked
(Si,AI)-framework observed so far is that of the zeolite faujasiteiL2]with 12.5 (Si,AI) atoms per
thus, it is denser than the
frameworks of 1 and 3.
One hypothetical example of a
vanadium phosphate net based on the
MER topology of the zeolite merlinoite (zeolite Wr131)is presented in
Figure 4 and in Table 1. Many more
such hypothetical vanadium phosphate frameworks can be derived
from zeolite-type nets by replacing
the S4R of tetrahedra by square units.
A fascinating aspect Of the aSOD
Figure 4. The net of aMER
topology (viewed parallel
frameworks of Nb,O,, sodalite, and
1 is that in each case the same topolo~
gy is generated, however, by groups
of radically different geometries,
sizes, and compositions. They have in common an overall fourconnected square-planar geometry with an approximate 90"
twist at the nodes. In terms of the geometry of the immediate
surroundings of the individual coordination polyhedra they differ too; thus the coordination sequences used to distinguish
between tetrahedral frameworks['] are different for Nb,O,, sodalite, and l .
The analogy between the more complex a-type nets and the
zeolite nets is most apparent in that both nets are of an AB,
type. In zeolites, A are four-coordinate and B two-coordinate
atoms, whereas in the a-type nets, A and B each represent
groups of atoms (1: A = V,09, B = PO,). This opens the way
to interpret other framework structures without square units in
an analogous way-like, for instance, the sulfides of Sn, Ge, and
G VCU ~erlugsge.~c~~sc~~ufi
mbH. D-69451 Weiiheim, 1997
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Angrrr.. Chem. Znt. Ed. Eng!. 1997, 36, No. 112
studied recently. An example of a structure built from
tetrahedral units is the Ge,MnS,, framework in [ (CH,),N],Ge,MnS,o,[151 which is identical to the framework of cristohalite,["] if one substitutes MnS, for one half of the SiO,
groups, and the adamantane-shaped Ge,S group for the other
half. Furthermore, starting from the ReO,-type["] (AB,) we
can view the framework of pharmacosiderite, KFe,(OH),(As0,);6
H,O, and its many isostructural compounds as examples of structures built from octahedral units. It consists of A
groups [M(O,OH)], (with M = Fe, Al, Ge, M o and other
cations in octahedral coordinations) made up of four fused octahedra tetrahedrally arranged, and of 6/2 tetrahedral B groups
TO, (with T = As, P, G e and others['s1) surrounding it octahedrally. Even N a 3 Z n 4 0 ( P 0 4 ) 3 ~ 6 H 2 0 ~belongs
L 9 1 to this series
because four fused Zn coordination tetrahedra around a central
oxygen atom replace the four octahedra of the pharmacosiderite
In terms of new microporous materials it is important to find
more open frameworks by searching for additional square-planar four-connected groups analogous to the V,O,(PO,), and
Mo,O,(PO,), units, and possibly larger ones, and to synthesize
frameworks along the principles described here. Such materials
could be particularly useful if they contained reactive transition
elements, such as the V4+/V5+ pair.["] The new construction
principle is important: the inert tetrahedral phosphate groups
bridge the potentially reactive square-planar groupings. This
role of the phosphate groups could be played by other tetrahedral anions, and the central square-planar Mo,O, and V,O,
units could be replaced by other groups. The nets composed of
square-planar units that have been introduced here are thus
potential carriers of arbitrary functional groups.
Received: August 1, 1996 [Z9406IE]
German version: Angen. Chem. 1997, 109, 88-90
Keywords: microporosity
- vanadium - zeolites
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ed.. Elsevier. London. 1996.
(21 M Schindler. W. Joswig, W. H. Baur. 2. Anorg Allg. Chem. 1997, press.
[3] M I. Khan, L. M. Meyer, R. C. Haushalter, A. L. Schweitzer, J. Zubieta, J. L.
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[5] A. Muller. J. Doring, 2. Anorg. A& Chem. 1991, 595. 251.
[6] A. F. Wclls. Further Studies .f'TIiree-dimen.sional Nets, ACA Monograph No.
8. Pittsburgh. 1979
[7] J. V. Smrth. An?.Minerul. 1978.63.960; in Crystal Structures of Zeolites, Landolt-5drn.srein S m e s 111(Eds.: W. H. Baur, R. X. Fischer), Springer, Berlin,
1997. i n press.
[8] A. L. Bowman. T C Wallace, J L. Yarnell, R. G . Wenzel, Acta Crystallogr.
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( I 11 W H Baur. A Bieniok. R. D. Shannon, E. Prince, Z . Krisfullogr. 1989, 187,
[12] W. H. Baur. Arm Mineral 1964, 49, 697.
[13] A. Bieniok. K. Bornholdt, U. Brendel, W. H. Baur, J Muter. Chem 1996, 6 ,
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Surl. Sci Curul. 1989,4Y, 375; K. Tan. Y. KO,J. B. Parise. A. Darovsky, Chem
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[I51 0. Achak, J. Y. Pivan, M. Maunaye. M. Louer, D. Louer, J Alloys Compd.
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AnReh.. Chrm Int Ed Enxl. 1997, 36. No. 112
New Nickel-Catalyzed Carbozincation of
Alkynes: A Short Synthesis of (2)-Tamoxifen**
Thomas Stiidemann and Paul Knochel*
Dedicated to Professor Waldemar Adam
on the occasion of his 60th birthday
The coordination of a double bond to a transition metal center strongly modifies the reactivity of the metal fragment and
that of the coordinated olefin."] This olefin activation is of great
importance for applications in organic synthesis, since it allows
the formation of new carbon -carbon bonds between unfunctionalized unsaturated molecules.'*1 Recently, we have shown
that the coordination of a double bond to a dialkylnickel(l1)
complex considerably facilitates the reductive elimination of the
organic ligands, making efficient nickel-catalyzed cross-coupling reactions between sp3-hybridized C centers possible for
the first time.i31 Here we report our attempts to extend this
reaction to alkynyl iodides (Scheme I), which led to the discovery of a highly stereoselective nickel-catalyzed carbozincation of
Scheme 1. Nickel-catalyzed cross-coupling of alkenyl and alkynql iodides with dialkylzinc compounds.
Our first experiments involved the treatment of trimethylsilylpentyne 2 with two dialkylzinc compounds, diethylzinc
(Et,Zn) and dipentylzinc (Pent,Zn). Like the corresponding alkenyl iodide, 2 undergoes smooth cross-coupling with
Et,Zn and Pent,Zn in THF/NMP (3/1) in the presence of a
catalytic amount of [Ni(acac),] (7.5 mol%, acac = acetylacetonate; -40"C, 20 h) to give the desired cross-coupling
products 3a and 3b in 60 and 61 % isolated yield, respectively
[Eq. (a)]. The coordination of the triple bond lowers the electron
EtzZn ( 2 equiv).
[ N i ( a c a ~ ) ~7.5
] ( mol % )
-78 ' C bis -40 'C, 20 h
3a : R = Et; 61 %
3b : R = Pent; 60 %
density a t the metal center (intermediate 1 in Scheme 1 ) and
facilitates the cross-coupling
In contrast, iodohexynes such as 4a that bear a more reactive
terminal alkyne group undergo tandem addition to the triple
bond, followed by coupling with the R group of R,Zn, to afford
exo-alkylidenecyclopentanes5. The reaction of 4a with Pent,Zn
or di(4-chlorobutyl)zinc in the presence of [Ni(acac),]
(7.5 mol%) furnishes cyclopentanes 5a (65%) and 5b (68%)
[Eq. (b)]. To determine the stereochemistry of the addition to
Prof. Dr. P. Knochel, DipLChem. T. Stiidemann
Fachbereich Chemie der Universitat
Hans-Meerwein-Strasse, D-35032 Marburg (Germany)
Fax: Int. code +(6421)282189
We thank the D F G (SFB 260) and the Fonds der Chemischen Industrie for
generous financial support. We thank Witco A G (Bergkamen), BASFAG
(Ludwigshafen), Bayer A G (Leverkusen), Chemetall GmbH (Frankfurt) and
SIPSY SA (Avrilli, France) for the generous gift of chemicals.
Verlagsgesel1.schUfrmbH, 0-69451 Weinheirn, 1997
$ 15.00+ .7.7,'11
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group, insertion, new, unit, microporous, squares, framework, structure, open, planar, construction, function, principles
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