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Cs3AuO the First Ternary Oxide with Anionic Gold.

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again the valuable balance of stability and reactivity in
triruthenium clusters.
Received: January 15, 1993 [Z 5808 IE]
German version: Angm'. Chem. 1993. 105. 1142
Fig. 1. Molecular structure of I b . Selected bond lengths [pm]: Ru2-Cl
213.0(5). Rut-Ct 227.1(5). Rul-C2 222.6(6), Rul-C3 223.0(6), R u K 4
223.4(7). Rul-C5 222.3(6). C1-C2 143.1(8), C2-C3 142.8(9), C3-C4 138.9(9).
C4-CS 143.5(9), CS-C1 143.6(8).
RuI).['l Both of these bonding types are known in the chemistry of ruthenium in, for example, 2[*l and 3,I9] but this
structure in which the cluster geometry is fixed by insertion
of a linking C p unit into a metal-metal bond is, to our
knowledge, unprecedented. Compound 4['01is, however, an
isolobal analogue of 1, and the mononuclear analogue 5["]
completes this isoelectronic series of M,, M,, and M , metallacycles.
[I] J. L. Kersten. A. L. Rheingold, K. H. Theopold. C. P. Casey, R. A.
Wiedenhoefer, C. E. C. A. Hop, Angen. Chem. 1992, t04. 1364; Angeir.
Chem. Int. Ed. Engl. 1992,31. 1341 ;see also J. J. Schnelder. ihd. 1992. 104,
1422 and 1992.31. 1392.
[2] See R. F. Jordan, Adv. Orgunomet. Chem. 1991. 32, 325- 387.
131 N. J. Coville. K . E. du Plooy, W. Pickl, Coord. Chem. Res. 1992. 116,
[4] D. S. Bohle, D. Heineke. A. Tiripicchio, M. Tmpicchio Camellini, H.
Vdhrenkamp. Angew. Cheni. 1990, 1112, 938-939: Angew. Chem. In!. Ed.
EngI. 1990.29.896-897; D. Heineke. D. S. Bohle. H. Vahrenkamp, Chem.
Ber. 1993, 126, 355-363.
[5] I R ( C H , C I , , B [ c m ~ ' ] ) : la.2115m,2065vs,2030vs, 1 9 9 4 s . 1 9 3 3 ~ I: b :
2084 vs. 2041 vs, 2004 vs, 1967 sh. 1922 m.'H N M R (CDCI,. int. TMS,
C p resonances): l a : 6 = 5.34 (m. 2H). 4.44 (m, 2H): I b : d = 5.05 (m.
2H). 3.98 (m, 2H). " C N M R (CDCI,, int. TMS, C p resonances): l a :
6 = 9 7 . 4 ( 1 C ) , 9 0 . 0 ( 2 C ) , 8 5 . 8 ( 2 C ) : 1 b : 6 = 1 0 7 . 5 ( d , J p ~= X . l H z , l C ) .
89.2 ( 2 C ) , 84.6 (2C). "P N M R (CDCI,, ext. H,PO,): 1 b: 6 = 29.3.
[6] Crystal data of l b : monoclinic, P2,jn. u =11.224(2), h =16.382(3),
c = 17.2980) A, B = 91.90(3)", Z = 43441 reflections. R = 0.031. Further
details of the structure determination may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische
Information mbH. W-76344 Eggenstein-Leopoldshafen (FRG). upon
quotation of the depository number CSD-400041, the authors. and the full
journal citation.
171 For a discussion of these bonding types see W. A. Herrmann. G. Kriechbaum, C. Bauer, E. Guggolz, M. L. Ziegler, Angric. Chem. 1981,93.838839; Angew. Chein. In!. Ed. Engl. 1981, 20, 815-816.
[81 K . P. C. Vollhardt, T. W. Weidemann, J Am. Chpm. Soc. 1983, 1115, 16761677.
[9] N. D Fedsey, N. J. Forrow, G . Hogarth, S. A. R. Knox, K. A. MacPherson. M. J. Morris, A. G. Orpen. J Orgunomet. Chem. 1984,267.C41 -C44.
[lo] S. Toke, E. T. K. Haupt, U. Behrens. Chem. Bey. 1986, 119. 96-106.
[111 P. Eilbracht. W. Fassmann, W. Diehl, Chem. Ber. 1985, 118, 2314-2329.
1121 H . Schmidtbaur, Angew. C h m . 1983, 95, 980-1000: Angrit.. Chrm. In/.
Ed. Engl. 1983.22,907 - 927.
[131 A. J Deeming, N. I. Powell. C. Whittaker, J Chern. Soc. D u k m Tron.s.
[14] D. Heineke, H. Vahrenkamp. Chem. Ber. 1993, 126. 373-377.
Cs,AuO, the First Ternary Oxide
with Anionic Gold""
By Claus Feldmann and Martin Jansen*
Dedicated to Professor Heinrich Noth
on the occasion of'his 65th birfhday.
I- I
Me2C - Fe(C0)2
The reaction pathway leading to 1 a, b is as uncommon as
their structure. Almost all coordination compounds of
Ph,P=C(CH), contain this ylide as an intact ligand.1'21 Its
reactions with [Os,(CO),,(MeCN),], for example, produce
closed Os, clusters with doubly and triply bridging
Ph,PC,H, units.r131Although the cleavage of phosphorus
ylides to generate carbene ligands is not unusual,"21 the separation of the oppositely charged Ph,P and C,H, fragments
and insertion of the cyclopentadienylide fragment into one
Ru-Ru bond of [Ru,(CO),,] are remarkable. Clusters I a, b
thus extend the long list of product types from reactions of
[Ru,(CO),,] and phosphorus ylides14. 14] and underline once
Angrw. Chem. h i t . Ed. Engl. 1993, 32. N o . 7
Gold has the highest electron affinity among the metals,
222.73 kJmol-', a value comparable to that of iodine
(295.30 kJ mol-').l'l Accordingly, the unusual properties of
CsAu, which crystallizes with the CsCl structure type, are
attributed to ionic bonding and thus the existence of anionic
gold (Au-).['] Because of this singular
this compound has been intensively studied in recent years. It behaves as a semiconductor with a band gap of approximately
2.6 eV.131There is still considerable disagreement whether the
cesium auride can be viewed as a purely ionic crystal
Cs' Au- . Differing ionic contributions to chemical bonding
have been discussed, and a value of roughly around 50% is
[*] Prof. Dr. M. Jansen, Dip].-Chem. C. Feldmann
Institut fur Anorgdnische Chemie der Universitdt
Gerhard-Domagk-Strasse 1. D-53121 Bonn ( F R G )
Telefax: Int. code +(228)735660
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
VCH Verlugsge.sclls~/iaftmhH, 0-69451 Wemheim, 1993
0570-0X33/93j0707-/04Y $ 10.00
the most popular; [',
even covalency has been considered.15]The picture of a pure ionic crystal is weakened by the
amazingly high electronic conductivity observedr3'. 61 in
comparison to that expected for an ionic model, and by the
presence of disorder (Au on Cs positions and vice versa) on
the order of 5%.["*] To gain insight into the bonding in
CsAu from its chemical behavior, we started conducting
solid-state reactions with CsAu to determine whether Auions are transported in solid state through diffusion. We have
observed the interdiffusion of Cs,O and CsAu and established that a new crystalline ternary compound, Cs,AuO, is
formed through transport in the solid. Crystals of higher
quality are obtained when CsAu is introduced as the constituting elements in the presence of excess cesium. The rodshaped (0.15 x 0.15 x 0.38 mm')), red-brown, transparent
crystals are extremely oxygen and moisture sensitive.
According to the results of X-ray powder diffraction,
which were verified by a single-crystal structure determination,['] Cs,AuO crystallizes as a hexagonal perovskite with
the anti-CsNiC1, structure type,["] in which Au and 0 adopt
the crystal-chemical function of Cs and Ni, respectively
(Fig. 1). The OCs, structural unit is stretched along the
Fig. 2. Au L,-XANES spectra of
Au,03, AuCI,, AuCN. AuCI, Au,
CsAu, and Cs,AuO (from top to
lower than that for CsAu. We consider this to be evidence
that Au in this compound has an even more distinct anionic
Experimental Procedure
Cs,AuO was synthesized by the interdiffusion ofequal molar amountsofCsAu
(0.601 g, 1.82 mmol) [XI and CsO, 4 9 (0.513 g, 1.82 mmol) [I 11. The intimately
ground binary components Cs,O and CsAu were annealled at 300 "C in a gold
crucible under argon for 3 weeks. Only small, strongly intergrown crystals of
Cs,AuO were found in the resulting reaction product.
Fig. 1. Unit cell of Cs,AuO; the polyhedra surrounding Au- and 0'- are
emphasized: 40-Cs) = 2.796(2) A (6 x ), d(Au-Cs) = 3.917(2) A (6 x ), and
4.242(3) A (6 x ).
threefold axis; the Cs-0 distances correspond roughly to
those in CS,O.["~ Each gold atom is surrounded by 12 cesium atoms in the form of a hexagonal cuboctahedron. The
increase in the (averaged) Au-Cs distance (4.08 A) from that
is the result of an increase in the coordiin CsAu (3.69
nation number from 8 to 12, and the extent of lengthening
corresponds well to that expected. The strong distortion of
the polyhedron around Au is striking: the distance between
Au and the six Cs neighbors in the a/b level is 3.917(2) A, and
between Au and the 2 x 3 Cs atoms above and below this
layer 4.242(3) A.
Every formulation other than the corresponding ionic
one, (Cs+),Au-02-, would require the existence of energetically very high-lying electronic states as well as electron
delocalization, which can be excluded due the transparency
of the crystals (even in thick layers). Thus, the ionic formulation must correctly describe the fundamental bonding situation. This interpretation is supported by a comparison of the
gold L,-XANES (XANES = X-ray Absorption Near-Edge
Structure) spectra of Au,O,, AuCI,, AuCN, AuC1, Au,
CsAu, and Cs,AuO (Fig. 2). The area of the prepeak at
about I2keV correlates with the number of unoccupied Au
5d states and is therefore a sensitive indicator for the valence
state of gold. One can recognize that the density of free states
in the region of the Au valence levels for Cs,AuO is even
Verlagsge.sellsrhaJi mhH. D-69451 Weinheim, 1993
Large, rod-shaped, red-brown, transparent crystals were isolated according to
the following method: Equal molar amounts of CsO, 4 9 (0.986 g, 3.50 mmol)
and fresh precipitated gold (0.690 g, 3.50 mmol) [13] were heated at 200 'C in a
melt of distilled cesium (1 ,892 g. 14.20 mmol) in a Duran glass tube under argon
for eight weeks. The excess cesium was then distilled off under high vacuum
(0.01 Pa). To improve the crystal quality, the single-phase residue was annealled
for an additional five days at 200°C in a Duran glass ampule under argon and
then cooled slowly ( 5 K h - ').
Received: February 19, 1993 [Z5878IE]
German version: Angew. Chem. 1993, 105, 1107
[I] H. Hotop, W. C. Lineberger, J. Phys. Chem. Ref: Data 1975, 4, 539.
[2] a) W. E. Spicer, A. H. Sommer, J. G. White. Phys. Rev. 1959,115, 57: b) J.
Knecht, R. Fischer, H. Overhof, F. Hensel, J. Chem. SOC.Chem. Commun.
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25, 2009.
[3] a) W. E. Spicer, Phys. Rev. 1962, 125, 1297; b) F. Wooten, G. A. Condas,
Phys. REV.1963, 131, 657; c) C. Norris, L. Wallden, Phys. Status Solidi
Sect. A 1970, 2, 381.
[4] J. Robertson, Phjs. Rev. Sect. B 1983, 27, 6322.
[5] G. Steinleitner, W. Freyland, Phys. Left. Sect. A 1975, 55, 163.
[6] R. Dupree. D. J. Kirby, W. W. Warren, Phys. Rev. Sect. B 1985.31, 5597.
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[8] G. A. Tinelli, D. F. Holcomb, J. Solid State Chem. 1978, 25, 157.
[9] X-ray structural analysis of Cs,AuO: space group P6,lmmc; a = 7.830(2),
c =7.059(10) A; Z = 2, pralEd
= 5.418 gem-'; Cs in 6h (x = 0.1598(1)),
Au in 2d, 0 in 2a; R = 0.044; 346 observed reflexions, F(OO0) = 504:
Enraf-Nonius CAD-4 diffractometer, w scan, 28 range from 3.0" t o
34.94', Mo,. radiation. Further details of the crystal structure mvestigation may be obtained from the Fachinformationszentrum Karlsruhe,
Gesellschaft fur wissenschaftlich-technische Information mbH, D-76344
Eggenstein-Leopoldshafen (FRG) on quoting the depository number
CSD-57248, the names of the authors, and the journal citation.
[lo] G. N . Tishchenko, Ti. Inst. Krislallogr. Akud. Nuuk. SSSR 1955, I f , 93.
[ l l ] A. Helms, W. Klemm, Z. Anorg. AIIg. Chem. 1939, 242, 33.
[12] C. Feldmann, A. Redeker, J. Hormes, M . Jansen. unpublished.
[13] G. Kriiss, Justus Liehigs Ann. Chem. 1887, 238, 43.
[14] Editor's comment: After this communication was submitted, a publication
on a Cd,AuN compound was printed for which Au- centers were also
formulated. J. Jiiger, D. Stahl, P. C. Schmidt, R. Kniep, Angew. Chem.
1993, 105. 738: Angew. C17em. Inr. Ed. Engl. 1993, 32, 709.
OS70-0X33/93j0707-1osOB 10.00f ,2510
Angms. Chem I n t . Ed. Engl. 1993, 32, N o . 7
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oxide, ternary, first, anionic, gold, cs3auo
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