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Na14Ba14CaN6ЧA Nanodispersion of a Salt in a Metal.

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\ /
"r ./ I
.I ,Gy.
Scheme 1. A
= Si(SiMe,),.
tions-short CI-CI distances (less than 300 pm) between the
parallel, nonplanar Ga2C1, rings and would evidently suffer
from a high ring strain.
The dichlorobis(hypersi1yl)digallane opens manifold possibilties for the synthesis of new gallium(I1) compounds, in particular, heterocycles containing a Ga, unit.
Experimental Procedure
1 : A suspension of Ga[GaCI,] (0.48 g, 1.68 mmol) in pentane (1 0 mL) was combined
at -78 "C with a solution of Li(THF),Si(SiMe,), (0.79 g. 1.68 mmol) in pentane
(1SmL). After slow warming to room temperature, the mixture was stirred
overnight and all volatiles were removed from the red solution in vacuum. The
residue was taken up in pentane (10 mL) and filtered. Colorless plates of 2 (0.20 g.
24%) crystallized from the solution at - 30 'C; then after reducing the volume
of the mother liquor, colorless prisms of 1 (0.21 g: 35% relative to
Li(THF),Si(SiMe,),) subsequently crystallized; m. p. > 180 'C (decomp ). 1:
' H N M R (C,D,): 6 = 0.44; "C N M R (C,D,): 6 = 3 5. MS (70 eV. EI, 64Ga):mi;
1053 (4) [Ga,[Si(SiMe,),],CI,]+.. 667 (1 1) [Ga,[Si(SiMe,),],CI]+. 598 (1) [Ga[Si(SiMe,),],Cl]+', 583 (12) [Ga[Si(SiMe,),],CI - Me]',
563 (6) [Ga[Si(SiMe,),],]', 351 (1) [GaSi(SiMe,),Cl]+, 316 (80) [GaSi(SiMe,),]'.. 73 (100)
[SiMe,]+. 2: 'H N M R (C,D,): 6 = 3.72 (m. 4H. OCH,), 1.10 (m, 4H. CH,), 0.38
(s. 27H, SiMe,); "C NMR (C,D,): 6 = 69.1 (OCH,). 25.8 (CH,), 2.8 (SiMe,). MS
(70 eV, EI. 69Ga):mji (%): 386 (0.5) [M - THF]+', 371 (0.5) [M - T H F - Me]',
351 (15) [M - T H F - Cl]', 247 (90) [Si(SiMe,),]+, 73 (100) [SiMe,]'
3: Compound 3 was synthesized analogously to 1 from Ga[GaCI,] (0.25g.
0.88 mmol) and Li(THF),Si(SiMe,), (0.83 g. 1.75 mmol). Yield: 0.22 g 3 (49%).
'H NMR (C,D,): 6 = 0.35; "C N M R (C,D,): 6 = 3. 1. MS (70 eV. EI. "Cia): m j z
(X)563: (10) [Ga[Si(SiMe,),],]', 73 (100) [SiMe,]'.
Received: November 8, 1995 [Z8534IE]
German version: Angepi. Chem 1996, 108, 593-595
Keywords: digallanes . gallium compounds
[I] a) W. Uhl, Angeii. Chem. 1993,105, 1449-1461, Angew. Chem. I n / . Ed. Engl.
1993,32.1386; b) W. Uhl, M. Layh, T. Hildenbrand, J. Organomer Chem. 1989,
[2] X. He, R. A Bartlett. M. M.Olmstedd. K. Ruhlandt-Senge. B. E. Sturgeon.
P. P. Power, Angew. Chem. 1993, 105, 761; AngeK. CAem. Inr. Ed. Engl. 1993.
32, 717.
[3] R. D. Schluter, A. H. Cowley, D. A. Atwood R. A. Jones, M. R. Bond, C. J.
Carraro, J. Am. Chem Soc. 1993, 115, 2070.
[4] J. C. Beamish, R. W. H. Small. I. J. Worrall, Inorg. Chen?. 1979. 18. 220.
[S] K. L. Brown, D. Hall, J. Chem. Soc. Dulron Truns. 1973. 1843. [6] See for
example H. Fussstetter. H. Noth, W Winterstein, Chem. Ber. 1977, 110, 1931.
[7] L. Rosch, H. Neumann, Angex Chem. 1980, 92, 62, Angew. Chem. I n / . Ed.
Engl. 1980. 19, 55.
[8] A . M . Arif, A. H. Cowley, T. M. Elkins. R. A. Jones, J. Chem Soc Cltem.
Commun. 1986, 1776.
[9] R. Frey, G. Linti, K. Polborn, Chem. Ber. 1994, 127, 101
[lo] a) N. Wiberg in Frontiers in Orgunosilicon Chemistry (Eds: A. B. Bassingdale,
P. P. Gaspar), The Royal Society of Chemistry, Cambridge, 1991, p. 263; b) U.
Schneider, R. Ahlrichs, H. Horn, A. Schiifer. Angels. C h f m 1992, 104, 321,
Angew. Chem. Int. Ed. Engl. 1992. 31, 353.
[ l l ] G. Linti, J. Orgunomer. Chetn., submitted
[12] S. Henkel, K -W. Klinkhammer, W. Schwdrz, Angew. Chem. 1994, 106, 721;
Angew. Chem. Inr. Ed. EngI. 1994. 33, 681.
[I 31 a) H. Gilman, C . L. Smith, J Oi~anomer.
Chem. 1968,14,91: b) G. Gutekunst,
A. G. Brook, J. Orgunomer Chem 1982,225, I ; c) A. Heme, R. Herbst-Irmer.
G. M. Sheldrick. D. Stalke, Inorg. Chon. 1993. 32. 2694.
[14] Details of the crystal structure determination of 1 . Crystal size.
0 30 x 0.15 x 0.15 rnm. orthorhombic. space group Prr12,, u = 3606.3(6), b =
1472.6(1), < = 3253 7(3) pm, V = 17.279(6) nm3, Z = 8,
= 1.085 gcm-3,
p = 1 . 6 0 m m - ' , 64041 measured reflections in 2 8 = 4 - 5 2 , STOE IPDS.
Mo,. radiation. Structure solution with direct methods, 28580 (23486 with
F>4o(F)) unique reflections were used in the full-matrix refinement of 1172
parameters against F Z . R , = 0.057, w R , = 0.186 (all data), hydrogen atoms
L G!
a'f A
VCH Verlugsgesellschuft mbH, 0-69451 Wemheim. 1996
with riding model, mdx. residual electron density 0.725 e k ' . TWIN parameter for racemic twinning set. In one of the two independent molecules in the
asymmetric unit, one of the hypersilyl groups is disordered in such a way that
two silicon positions are observed for each of the three trirnethylsilyl groups,
but no split positions are seen for the carbon atoms The two molecules d o not
markedly differ in terms of their bond lengths and angles. Both molecules
(neglecting the disorder) are correlated by a pseudo cenfer of inversion i n
(0.0.25.--0.14) Refinement of the structure in space group Pcub (no. 61. Pbcu)
did result in a R , value of 0.20. The advice of Prof. Dr. H. Biirnighausen is
gratefully acknowledged Details of the crystal structure determination of 3:
The examined crystals were of very low diffracting intensity. Therefore the
present X-ray structure determination only confirms the constitution of 3, but
allows no further discussion of Ihe structure. Crystal size. 0 . 2 0 ~
0.20 x 0.04 mm, monoclinic, space group P2,/c, u = 2324.6(10). h =
1285.6(2). c = 2304.9(5) pm. = 101.69(3)'. V = 6.745(3) nrn'. Z = 4. pEIlod
1.11 gcm-',p =1.11 m m - ' . ProgramsusedareSiemensSHELXTLPlus(PC)
and SHELXL93 (PC). Further details of the crystal structure investigation of
I may be obtained from the Fachinformationszentrum Karlsruhe, D-76344
Eggenstein-Leopoldshafen (Germany), on quoting the number CSD-404582.
[151 M. A. Petrie. P P Power, H. V. R. Dias, K. Ruhtandt-Senge. K. M. Waggoner, R. J. Wehmschulte, Orgunomefullics 1993, 12, 1086.
[16] 0. T. Beachley, Jr.. R. B. Hallcock, H. M. Zhang, J. L Atwood, Organomerallies 1985. 4 , 1675.
[17] A. F. Wells, Structurol Inorgunic Chernisrr~,,5th ed., Clarendon Press, Oxford
Na ,Ba, ,CaN,-A
in a Metal**
Nanodispersion of a Salt
Ulrich Steinbrenner and Arndt Simon*
Subnitrides of sodium and barium have recently been discovered. These compounds contain discrete Ba,N octahedra in
Na,,Ba,Nr'] as well as chains of face-sharing Ba,,,N octahedra
in NaBa,NCZ1and Na,Ba,N.[31 The bond between barium and
nitrogen is ionic, whereas that between barium and sodium is
The replacement of sodium by potassium as well as the introduction of additional potassium into a sodium-barium subnitride seemed a logical extension of this work. The reaction with
NaK alloy (Na: K = 3: 1) and barium (which had been pretreated with nitrogen in the ratio Ba:N = 3 : l ) led to a rather unexpected result: a few brittle crystals isolated from the liquid had
the composition "Na,,Ba,,KN,"
according to X-ray structure
analysis. The subnitride cluster unit of this structure is shown in
Fig. la. The atom in the cluster can easily be refined as potassium. However, since potassium nitrides are unknown,r41the coordination of nitrogen atoms to potassium is rather uncommon.
All attempts to synthesize a compound of the composition
above in high yield were unsuccessful.
A refinement of the X-ray data with calcium instead of
potassium gave slightly better R values,r51and subsequent attempts to synthesize Na,,Ba,,CaN, by specific addition of calcium were indeed successful.[61The compound formed in approximately 6 5 % yield together with NaBa,N and Ba,N. A
quantitative synthesis of the new compound Na ,Ba,,CaN, has
not yet been achieved, probably because of the low solubility of
Ca (added in small pieces) in NaK alloy and because of the
generally low reaction rate."]
['I Prof
Dr. A. Simon, DIpLChem. U. Steinbrenner
Max-Planck-Institut fur Festkorperforschung
Heisenbergstrasse 1. D-70569 Stuttgart (Germany)
Fax: Int. code +(711)689-1642
We thank Dr. T. Braun. 0.
Buresch, Dr. J. Kohler, Dr. R. Pottgen, and Dr. R.
Ramlau for experimental assistance and discussions.
0S70-0833196j3505-0552 S 15.00 2510
Angew Chem. Inr. Ed Engl. 1996, 35,
No. 5
The spurious formation of Na,,Ba,,CaN,
in the reaction
performed without added Ca has an interesting interpretation.
The barium used, which had been distilled in high vacuum, still
contained 0.3(1) wt O h Ca according to AAS analysis (AAS =
atomic absorption spectrometry). Virtually all the calcium impurity was incorporated into the solid subnitride. An EDX analysis (EDX = energy dispersive X-ray spectroscopy) verifies that
calcium is trapped in Na,,Ba,,CaN, crystals."]
From a structural point of view, the Ba,,CaN, cluster extends the series of previously known subnitride and suboxide
clusters (Fig. 1 ) . While the M,A octahedra in Na,,Ba,N remain
Fig. 1 The Ba,,CaN, cluster (a) i n Na,,Ba,,CaN, and its schematic fragmentation into M, ,A, ( b ) . M,A2 (c). and M A , fragments (d) (see text). Drawn from the
center outwards. the Ba,,CaN, cluster consists of a central Ca atom, an octahedron
of N atoms. ii cube of Ba' atoms, and an octahedron of Baa atoms.
discrete, in Rb,0,[91 two of them share a face to form the M,A,
cluster;["] in Cs, 103[111
three octahedra are connected through
common faces to form the M , ,A3 cluster. The M 5A6cluster in
Na,,Ba,,CaN, results from six analogously connected octahedra. Consequently, the central calcium atom is surrounded by
an octahedron of N atoms and a cube of Ba atoms (Ba'). Six
additional Ba atoms (Baa) cap the faces of this cube. In the
structure of Na ,,Ba,,CaN, the clusters are arranged in the
cubic close packing scheme. The tetrahedral voids of the pdcking are occupied by eight of the fourteen Na atoms in two Na
tetrahedra whose edges are bridged by the six remaining Na
atoms. Remarkably, the octahedral voids of the cluster packing
remain empty.
The C a - N distance of 257(1) pm in the cluster (Fig. l a ) is
about 14 pm longer than corresponding distances in comparable structures (Ca,N: 243 pm,["] x-Ca,N,: 246 ~ m , [ ' ~ '
Ca,NAu: 141 prn[l4'). On the other hand the Baa-N distance
of 250(1) pm is 25 pm shorter (Ba,N: 276 pm,[15] NaBa,N:
273 pmf2').and the Baa-Na distances (440 pm and 451 pm) are
somewhat longer than Ba-N o r Ba-Na distances in comparable structures (NaBa,N: 420 pm and 450 pm, Na,Ba:
432 pm.["] NaBa: 410 pm and 435 pm["]). The distance between Ba' and N is 276 pm. The striking differentiation in the
Ba-Ba distances (Ba'-Ba': 379 pm, Ba'-Ba": 426 pm) is also
found in the cluster chain Ba,N in NaBa,N and Na5Ba3N
(365 pm and 408 pm), in contrast to the intermetallic phases
NaBa (449 pm and 459 pm) and Na,Ba (452 pm) in which this
differentiation does not occur. The Na-Na distances are
401(1) pm between atoms in the Na tetrahedra and 366 pm to
the bridging Na atoms (Na,Ba,N: 370 pm to 410 pm, Na,Ba:
370 pm, NaBa: 366 pm and 387 pm).
The band structure calculated with the Extended-Huckel approximation shows a distinct separation in energy between the
sharp, localized levels of the N atoms and a broad band consisting of Na and Ba orbitals, which extends beyond the Fermi
level. A Mulliken population analysis resulted in highly negatively charged nitrogen atoms, which can be interpreted as N 3 ions. Calcium and barium supply the electrons needed to form
these ions. The Ca and Ba' atoms have a higher positive charge
than the Baa atoms, which indicates that especially the Baa
atoms are responsible for the bonding between the cluster and
the Na matrix. Both the cluster unit itself and the Na atoms may
be considered neutral.
On the basis of a purely electrostatic model the shift of the
nitride ions out of the centers of the Ba5CaN octahedra, which
is responsible for the long C a - N distances, is a result of the
mutual repulsion of the highly charged N 3 - ions. A similar
displacement is found for the 0'- ions in the suboxide structures Cs,,O,r"~ and Rb,0,.[91 In the latter the anions are situated 31 pm from the centers of the octahedra. This model also
explains the trigonal distorsion of the Ba,N octahedra in
and Na,Ba,N,I3] which results in the two different
Ba-Ba distances in the Ba3N chains.
The plausible assumption that the bonds within the cluster
are predominantly ionic and that it is embedded in a metallic
matrix leads to a formal description of the bonding as
[ N a l 4 B a , ] [ B a ~ + C a 2 + N ~ In
- ] . this model one part of the structure forms a metallic Na,,Ba, matrix, which contains discrete,
finely dispersed unit cells of the hypothetical perovskite type
"BaCaN,". Na,,Ba14CaN6 may be considered a nanodispersion of a salt in a metal.
A n g r i r . t'iirn?. Iril
E d Engl. 1996, 35,N o . 5
Fig. 2. A schematic view of the structure of Na,,Ba,,CaN,- ii dispersion of ionic
Ba,CaN, units in a metallic matrix of sodium and barium. Thc shaded polyhedra
represent Ca-centered Ba, cubes whose faces are all capped by N atoms
It i s interesting to note that the amount of sodium is variable.
So far we synthesized four different, strictly stoichiometric
phases Na,Ba,,CaN, with n = 14, 17, 21 and 22. According to
X-ray analysis all these phases contain the described Ba,,CaN,
cluster in different Na environments.'20]
VCH V e r l ~ ~ . ~ g ~ . ~ mhH,
~ l l . s0-69451
~ h ~ i ~ We'iiiheim,
Received: November 17, 1995 [28562IE]
German version. A n g w Chem 1996. IOH. 595 -597
0570-0833:96i3505-0553 $ 1S.00+ .2.i 0
Keywords: barium compounds . calcium compounds . nitrides .
solid-state structures
[17] G. J. Snyder, A. Simon, J. Chem. Soc. Dalton Trans. 1994, 1159.
[18] Band structure calculations [21,22] have been performed with the program
package EHMACC/EHPC/EHF’P [23] using relativistic single-zeta orbitals
and orbital energies 1241 (N 2s: H,, = - 26.253 eV, [ =1.886; N 2p:
H,, = -13.829eV. i=1.728; Na 3s: H,, = - 4.962eV. i = 0.833; Na 3p:
H , , = - 2 . 9 7 5 e V , [=0.611; Ca 4s: H , , = - 5 . 3 4 2 e V , [=1.071, Ca 4p.
H,, = - 3.561 eV, i= 0.891; Ba 6s: H,, = - 4.440 eV, ( = 1.279; Ba 6p:
H,, = - 2.991 eV, i = 1.059). The results yield a sharp band of N 2s character
(- 27.0 to -26.0eV). another sharp band of N 2p character (-14.4 to
- 13.4 eV). and a diffuse band (starting at -8.0 eV) with Na and Ba character,
which extends beyond the Fermi level. Obviously, the bond energies found for
the N 2s and N 2p bands are too high [25]. This is not surprising. since the
nitride ions in the subnitrides can not be treated satisfactorily within the Extended-Hiickel approximation. A similar band structure calculation for
NaBa,N results in a bond energy of 9.7 eV for the N 2p levels. In contrast. the
U P spectra of the N 2p levels in this substance show that the experimental bond
energy is only 2.0 eV [25]. The result corresponds with UPS measurements of
the alkali metal suboxides, which show photoemission from the 0 2p levels at
2.7 eV.““’
[19] Without charge iteration the band structure calculation results in the following
Mulliken charges- N -2.77, Ba’ f1.58, Baa f1.14, Ca f1.43, N a l -0.24,
Na2 -0.38.
1201 A. Simon, U. Steinbrenner, J. Chem. Soc. Dalfon Trans., in press.
1211 R. Hoffmann, J. Chem. Phys. 1963, 39, 1397.
[22] R. Hoffmann, W. N. Lipscomb, J. Chem. Phys. 1962, 36, 2179.
[23] QCPE program EHMACC of M. H. Whangbo, M. Evain, T.Hughbanks, M.
Kertesz, S . Wijeyesekera, C. Wilker, C. Zheng, R. Hoffmann
[24] J. P. Desclaux, At. Dora Nucl. Data Tables 1973, f 2 , 311
[25] U. Steinbrenner, Diplomarbeit, University of Stuttgart, 1994.
[26] G. Ebbinghaus. A. Simon, Chem. Phys. 1979, 43. 117.
G. J. Snyder, A. Simon, Angew Chem. 1994, 106, 713; Angew. Chem. Int Ed.
Engl. 1994. 33, 689.
P. E. Rauch, A. Simon, Angew Chem. 1992, 104, 1505. Angex.. Chem. l n f . Ed.
Engl. 1992,31, 1519.
G. J. Snyder, A. Simon, J A m Chem. Soc. 1995, 117, 1996.
Nitrides M,N of the alkali metals Na, K, Pb, and Cs have been mentioned, but
could not be characterized: F. Fischer, F. Schroter, Eer. 1910, 43, 1465; R .
Suhrmann. K. Clusius, Z. Anorg. Allg. Chem. 1926, 152, 5 2 ; F. Blatter, E.
Schumacher, J. Less Common Met. 1986, f f 5 , 307.
Structural analysis ofNa,,Ba,,CaN,: space group Fm3m, a = 1789.54(6) pm,
2 = 4. pEIlid= 2.745 gem-,. N in 24e ( x = 0.8563(4)), Ca in 4a. Nal in
24d, Na2 in 32j, (x =0.3292(2)), Baa in 24e (x=O.71644(3), Ba’ in 32J
(x = 0.10577(1)). Rf = 0.0283 (“Na,,Ba,,KN,”:
0.0287, “Na,,Ba,,ScN,”:
0.0283), irR2 = 0.0452 (“Na,,Ba,,KN,”~ 0.0453, “Na,,Ba,,ScN,”. 0 0471)
for 512 reflections and 17 parameters. F(OO0) = 4000, CAD-4 diffractometer.
(0- 6 scan, 6 range from 2 to 24 ’, AgKaradiation, absorption correction:
scan. Further details of the crystal structure investigation may be obtained
from the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen (Germany) on quoting the depository number CSD-404430.
Under an inert argon atmosphere distilled Ba (555.6 mg, 4.046 mmol), distilled
Ca (11.6 mg, 0.289mmol). NaN, dried under high vacuum (37.6mg.
0.578 mmol), and Na-K alloy (1223.8 mg. 69 atom%) were sealed in a tantalum ampoule. To prevent oxidation of the tantalum, the ampoule was additionally sealed in a Duran glass ampoule. This ampoule was heated to 400’C at
20 K h - ’ . After24 h a t thistemperature, theampoulewascooledat 1 K h - I to
120°C and annealed at this temperature for 3 months. Excess alloy was removed from the metal slurry in a press (about 5 kbar). The product was a
brittle metallic substance, two-thirds of which consisted of Na,,Ba,,CaN,. All
manipulations were performed in a glovebox under argon.
Experiments with Ca,N o r Ca-Ba alloy as calcium source are in progress.
Standardless EDX point analysis on a Na,,Ba,,CaN, crystal gave a Ca:Ba
ratio of 1’15.8.
A. Simon, Z. Anorg. Allg Chenr. 1977, 431, 5.
A (anion): N or 0 .
A. Simon, E. Westerbeck, 2. Anorg. Allg. Chem. 1977, 428, 187.
E. T.Keve, A. C. Skapski, Inorg. Chem. 1968. 7, 1757.
P. Y Laurent, J. Lang, M. T. LeBihan, Actu Cryslallogr. Sect. E 1968, 24,
J. Jager, D. Stahl, P. C. Schmidt, R. Kniep, A n g e x Chem. 1993, 105, 738.
Angew. Chem. lnt. Ed. Engl. 1993, 32, 709.
T. Kiinzel, Dissertation. University of Stuttgart, 1980.
G. J. Snyder, A. Simon, Z. Naturforsch. B 1994, 49, 189.
VCH Verlagsgesellschuj~mbH, D-6Y451 Weinherm, 1996
In the communication “Selective Catalysis on Silicon Dioxide
with Substrate-Specific Cavities” by W F. Maier and J. Heilmann (Angew. Chem. Int. Ed. Engl. 1994, 33, 471-473) the
reaction rate of 7 mmol h- g-’ (p. 472, last paragraph) should
be corrected to 0.07 mmol h - g- In addition the specification
of 1.0 g of catalyst A used in this experiment is missing.
O57O-0833/96I350S-0554$ 15 OOf .2S/0
’ ’.
Angew. Chern. lnt. Ed Engl. 1996, 35, No. 5
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