close

Вход

Забыли?

вход по аккаунту

?

Ba2Nd7Si11N23ЧA Nitridosilicate with a Zeolite-Analogous SiЦN Structure.

код для вставкиСкачать
COMMUNICATIONS
[S]
[6]
[7]
[S]
[9]
[lo]
c) J. Zhang, J.S. Moore, J. Am. Chem. SOC. 1994, 116, 2655; d) C.
Metsendorf, H. Ringsdorf, Mol. Eng. 1992,2,189;e) C. F. van Nostrum, S. J.
Picken, A.-J. Schouten, R. J. M. ,Nolte, J. Am. Chem. SOC.1995,117, 9957.
A. R. A. Palmans, J. A. J. M. Vekemans, H. Fischer, R. A.M. Hikmet, E. W.
Meijer, Chem. Eur. J. 1997,3, 300.
Details will be published elsewhere.
A measure for the chirality is given by the chiral anisotropy factor g ( =
Ads).
(R)-(-)-2,6-Dimethyloctane was synthesized by catalytic hydrogenation of
(S)-(+)-citronellyl bromide. ”C NMR (CDCI,): 6 = 39.4, 36.9, 34.5, 29.5,
28.0,24.9,22.7,22.6,19.2,11.4;
GLC-EI-MS: m/z 142 ( M + ) ,127 (M’ - CH,),
113 (M+- CH,CH,), 85,71,57,43,29; [a]fo = - 5.5” (neat).
M. M. Green, N.C. Peterson, C. Khatri, J. Am. Chem. SOC.1993,115,4941.
For mixed stacks in equilibrium we can deduce the following equation:
(T= Al, Si; X = O).W This ratio should also hold for zeoliteanalogous nitridosilicates. All nitridosilicates obtained so far
by high-temperature synthesis possess Si -N substructures in
the range 0.5 5 T:X 5 0.75 having no open channels or large
cavities.171
The synthesis of BazNd7SillNz3produced the first nitridosilicate with a zeolite-analogous Si - N network structure. The
new nitridosilicate was synthesized in a high-frequency
furnace [*I by reaction of stoichiometric amounts Is] of barium
and neodymium with silicon diimide [lo] under nitrogen
atmosphere [Eq. (a)]. By this procedure Ba,Nd7Si,,N2, is
formed as a coarse crystalline, dark blue solid.I1ll Like all
other nitridosilicates synthesized in our group, Ba,Nd7SillN2,
is stable up to 1600°C and insensitive to hydrolysis.
in which g is the anisotropy factor for a mixture with rnolfraction x of chiral
l a in a solution of lb, gois the anisotropy factor for the solution of pure l a
[ 1 1 ] , a = K [ M ] = l + [ ( l - d ~ ) 1 2 K c ] ( M . B . M a r t i n , C h e m . Rev.1996,
696,3043), q = 1 -x, t =aq, r=a& and s is the number of molecules for
which chirality is controlled in one direction. Evaluation gives:
2 B a + 7 N d + l l Si(NH),f’/, N,
_
8 --1 Ill] For the constant go,the g value of the 10/90 mixture l d l b was used in the fit
to compensate for packing effects.
[12] In (-)- and (+)-3,3’-di(camphanoylamino)-2,2’-bipyridinein MeOH and
CHC13, weak Cotton effects are found in the bipyridine band, which are
attributed to a small deviation from coplanarity of the bipyridine system.
[13] This packing of the molecules in columns could be stabilized by intermolecular H-bonding. See a) Y. Yasuda, E. Iishu, H. Inada, Y. Shirota, Chem.
Lett. 1996,575; b) Y. Yasuda, Y.Takebe, M. Fukumoto, H. Inada, Y. Shirota,
Adv. Mater. 1996,8, 740.
Ba2Nd,SillN23-A Nitridosilicate with a
Zeolite-Analogous Si - N Structure**
Hubert Huppertz and Wolfgang Schnick”
In the past few decades zeolites and aluminosilicates have
found important technological applications as microporous
solids.[’] For the specific modification of their catalytic
properties the tetrahedral centers aluminum and silicon were
substituted by a large number of electropositive
Recently, the replacement of the bridging atoms 0 by
different atoms or building units in the network structures
was successful.131For example, Zn6[P12N24]C12
with a sodaliteanalogous structure of corner-sharing PN4 tetrahedra was
synthesized in our group.14]Host - guest behavior by reversible
encapsulation of molecular hydrogen was established for the
.[51
analogous halogen-free nitridosodalite Zn6[PI2Nz4]
With regard to the material properties and the high stability
of nitridosilicates, it seemed challenging to build up zeoliteanalogous microporous network structures from SiN4 tetrahedra. Typical for nearly all oxidic zeolites is a molar ratio of
tetrahedral centers (T) to bridging atoms (X) of T:X = 1:2
[*] Prof. Dr. W. Schnick, DipLChem. H. Huppertz
Laboratorium fur Anorganische Chemie der Universitat
D-95440 Bayreuth (Germany)
Fax: Int. code + (921)55-2788
e-mail: wolfgang.schnick@uni-bayreuth.de
[**I This work was supported by the Fonds der Chemischen Industrie and the
Deutsche Forschungsgemeinschaft (Projekt “Nitridozeolithe” SCHN 3771
6-1 and in the Gottfried-Wilhelm-Leibnizprogram).
Angew. Chem. Int. Ed. Engl. 1997,36, No. 23
900-1650*C’40h,
HF furnace
Ba2Nd,Si,,N2,
+ 11 H,
(a)
The X-ray structure
on single crystals of
Ba2Nd7SillN2, shows a three-dimensional network structure of corner-sharing SIN, tetrahedra according to
2 [ (Siy/NF1NE)25-].With a molar ratio of Si:N = 11:23, the
degree of condensation is smaller than in most of the
Accordingly besides
oxidic zeolites (Al/Si:O = 1:2)
bridging atoms Ni2], terminal atoms are connected to Si
(“‘1).
(The superscript in square brackets in NIX]defines
the number of Si atoms covalently bound to N, and vice
versa for Sir.]). The ratio of Q4 and Q2 tetrahedra in the
Si-N network structure is 1O:l. Thus Ba2Nd7SillNz3shows
the lowest degree of condensation amongst the Si - N
network structures obtained so far. The network of
corner-sharing SIN, tetrahedra in Ba2Nd7SillNZ3can be
characterized by the specific distribution of Si,N, ring sizes.[14]
In Ba2Nd7Sil,N23all ring sizes appear with the exception of
n = 2 and 5.
Characteristic for the structure of BaZNd7Si,lN23(Figure 1)
are channels along [OOl]. The Ba2+ions are centered in the
Si8N8ring channels and in the Si6N6ring channels along [loo].
The Nd3+ ions are positioned in the smaller voids. The metal
ions are coordinated by seven and eight nitrogen atoms of the
Si-N network (Ba2+-N: 273(1)-316(2) pm; Nd3+-N:
229(2)-312(1) pm). The Ba2+ ions in the wide Si,N, ring
channels (Figure 2) have a markedly higher coordination
number of 16 and corresponding longer distances to the
nitrogen atoms (Ba2+-N: 337(1)-441(2) pm).
The bond distances Si - NL2] in the network structure
(167(1) -175.5(5) pm) are typical for simple bridging N[2]
atoms in nitrido~ilicates.[~]The distances Si -NIII
(175.4(12) pm) correspond to the values of terminal N atoms
in Ba5Si2N6(174-176 pm).[15]
A measure for the microporousity of a zeolite-analogous
structure is the framework density (FD), which indicates the
number of tetrahedral centers (T) in a volume of 1000A3.
With a FD of 18.5, Ba2Nd7SillNz3
is similar to typical zeolites
(framework densities of some zeolites in T/(lOOO A,): 17.5
(A1P04-5), 17.9 (ZSM-5), 19.3 (Nonasil)) .[6]
The successful synthesis of Ba2Nd7SillN2,is the first proof
that not only highly condensed Si - N network structures but
also open, zeolite-like networks of corner-sharing SIN,
tetrahedra can be realized. In contrast to conventional
zeolites, which are synthesized by solvothermal procedures
using templates, the nitridosilicates are only accessible by
high-temperature synthesis. The next aim of our efforts will be
the exchange of the bulky metal ions for hydrogen atoms
0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
0570-0833/9713623-2651$ 17.50t.50/0
2651
COMMUNICATIONS
[lo] The X-ray amorphous product obtained by
. ammonolysis of SiCl, has the approximate
composition Si(NH)> Despite its undefined
character, silicon diimide is an important precursor for the technical production of Si3Nu.Cf.
H. Lange, G. Wotting, G. Winter, Angew.
Chem. 1991,103,1606; Angew. Chem Int. Ed.
Engl. 1991,30, 1579.
[ l l ] The composition of Ba,Nd,Si,,N,, determined
by structural analysis was confirmed by energy
dispersive X-ray microanalysis (Ba, Nd, Si).
The absence of hydrogen (NH) was checked by
IR spectroscopy.
[12] Ba2Nd,Sii,Nz3: Cmrnm, a = 1096.20(6), b =
2304.60( 14), c = 964.85(5) pm. Z = 4, Siemens
P4 diffractometer, MoKu radiation, graphite
monochromator, F(OO0) = 3388.0, /(MoKa) =
18.39 mm-I, w scan, 14287 measured reflections
in the range 2" 5 285 60", 2021 unique reflections with F i >Oo(F;), empirical absorption
correction (@ scans), R,,, = 0.0472; the crystal
Figure 1. Crystal structure of Ba,Nd,Si,,N,,, viewed along [OOl]. Left: the SIN, tetrahedra are shown as closed
structure was solved by direct methods
polyhedra, Ba2+as gray spheres, and Nd3+as white spheres. Right: topology of the Si-N network; only the Si
(SHELXTL, Vers. 5.03) and anisotropically
refined by a least-squares procedure against
tetrahedral centers are directly connected.
F Z with all data, 32 refined parameters, R1=
0.0440, wR2 = 0.0884, GOF = 0.973. Further details of the crystal structure
investigation may be obtained from the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen,on quoting the depository
number CSD-407202.
[13] Most of the oxidic zeolites have a molar ratio T O = 12. Nevertheless, there
are exceptions like the zeolites C H I , -CLO, -PAR, -RON, and -WEN with
T O < 1:2. Accordingly, terminal 011
' atoms were found as well as simple
bridging 0l21atoms, cf. ref. 161.
[14] Network structures of connected SIN, can be characterized topologically by
the cycle-class sequence. It specifies the relative abundance of Si,N, ring
sizes (for n = 1,2,3...) per unit cell. Cycle-class sequence of Ba,Nd,Si,,N,,:
(-,0,6,1,0,12,24,30...). Cf. also: a) W. E. Klee, Z. Kristallogr 1987, 179,67; b)
A. Beukemann, W. E. Klee, ibid. 1994, 209, 709.
[15] H. Yamane, F. J. DiSalvo, J. AIIoys Comp., 1996,240, 33.
Figure 2. Sectional view of the wide Si,N, ring channels ([OOl] 8 285 x 438 pm2)
in Ba,Nd,Si,iN23.Left: coordination of the Ba2+ions (coordination number 16).
Right: the free diameter of the channels is calculated from the atomiccoordinates
considering the ionic radius of N3- (146 pm); cf. also ref. [6].
bound to the nitrogen atoms of the Si-N network structures.
The Ba2+ions in the open channels of Ba2Nd,Sil,N2, seem to
be predestined for this procedure.
Received: June 27,1997 [Z10606IE]
German version: Angew. Chem. 1997,109,2765-2767
-
-
Keywords: nitridosilicates solid-state structures structure
elucidation zeolite analogues
PI
a) J.~CSmith, Chem. Rev. 1988,88, 149; b) D. W. Breck, Zeolite Molecular
Sieves, Wiley, New York, 1974.
W. Holderich, M. Hesse, F. Naumann, Angew. Chem. 1988,100,232;Angew.
Chem. Int. Ed. Engl. 1988,27,226.
C. L. Bowes, G. A. Ozin, Adv. Muter. 1996,8, 13.
W. Schnick, J. Liicke, Angew. Chem. 1992,104,208; Angew. Chem. Int. Ed.
Engl. 1992,31, 213.
J. Weitkamp, S. Ernst, F. Cubero, F. Wester. W. Schnick, Adv. Muter 1997,9,
247.
W. M. Meier, D. H. Olson, Atlas of Zeolite Structure Types, Butterworths,
London 1987.
W. Schmck, H. Huppertz, Chem. Eur J. 1997,3,679.
T. Schlieper, W. Schnick, Z. Anorg. Allg. Chem. 1995, 621, 1037.
In a typical batch 0.4 mmol Ba, 1.3 mmol Nd, and 2 mmol Si(NH)2 were
thoroughly mixed under inert gas atmosphere in a glove box and transferred
in a tungsten crucible into the high-frequency furnace. Under nitrogen
atmosphere the reaction mixture was heated to 900°C in 7 h and over a
further 18 h to 1650°C followed by a cooling over 15 h to 1400°C and in
another 15 min to room temperature.
2652
0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997
Alkylrhenium Oxides from Perrhenates: A
New, Economical Access to Organometallic
Oxide Catalysts**
Wolfgang A. Herrmann,* Roland M. Kratzer, and
Richard W. Fischer
Organometallic oxides have been thoroughly investigated,
particularly because some representatives of this ever-growing class of compounds exhibit a variety of catalytic properties."] One of the main reasons behind our interest in rhenium
is the diverse catalytic successes of methyltrioxorhenium
(MTO) .[*I This has recently been reported to catalyze different oxidation
Twenty years after MTO was first
observed,151two synthetic pathways have become established
for access to organorhenium(vr1) oxides:
[*I Prof. Dr. W. A Herrmann, R. M. Kratzer
Anorganisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-85747 Garching (Germany)
Fax: Int. code + (89)289-13473
e-mail: herrmann@zaphod.anorg.chemie.tu-muenchen.de
Dr. R. W. Fischer
Corporate Research & Technology, Hoechst AG, Frankfurt am Main
(Germany)
[**I Multiple Bonds between Transition Metals and Main Group Elements, Part
169. This work was generously supported by the Bayerische Forschungsverbund Katalyse. Part 168: W. A. Herrmann, H. Ding, R. M. Kratzer, F. E.
Kuhn, J. J. Haider, R. W. Fischer, J. Orgunomet. Chem., in press.
0570-0833/97/3623-2652$ 17.50+.50/0
Angew. Chem. Inr. Ed. Engl. 1997,36, No. 23
Документ
Категория
Без категории
Просмотров
1
Размер файла
358 Кб
Теги
analogous, structure, zeolites, nitridosilicate, siцn, ba2nd7si11n23чa
1/--страниц
Пожаловаться на содержимое документа