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KCeSe4 A New Solid-State Lanthanide Polychalcogenide.

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Chorin vac-8 was attached to estradiol derivative 19, which
was prepared in a few steps (Scheme 3), in order to optimize
the biological properties of photodynamically active
sensitizers and to bind chlorins to the estrogen receptors as
fluorescence markers.['"' In estrogens the structural region
with the phenolic hydroxyl group is crucial for receptor
thus the chlorin was attached with a diether
spacer of appropriate length to the 17-hydroxyl function of
the estradiol.
The homocliiral diastereomeric estrogen chlorin ethers
10 a and 10 b obtained by the introduction of the enantiomerically pure estrogen unit were separated by analytical HPLC;
this should also be possible for the preparative-scale resolution of chlorin rac-8. Spectroscopic data for selected compounds are provided in Table 1 .
Table 1. Selected spectroscopic data for rac-8, rac-9, rue-lOa,b, rac-11, and
rac-8: M.p. 207-208'C; LJVjVIS (CHCI,): A,,, [nm] ( E ) = 391 (144800). 489
(8700), 495 (SSOO), 523 (200), 591 (1600), 616 (1400) 643 (37400); ' H NMR
(360 MHz, CDCI,): 8 = - 2.65 (m. br, 2 H, NH), 1.80 (s, 3 H, CH, an C-2),
3.65,4.04 (AB system, J4,,= 17.9 Hz, 2 H, CH, on C-2), 4.60 (m, br, 1 H, OH),
6.81 (d, JtlCOH
= 3 Hz, 1 H , 3-H),, ( 5 s. 5 H, 5-, 8-, 10..
15-, 20-H); MS (70eV): mlz628 ( M + , loo%), 555 (M'-CH,CO,CH,, 50).
rac-9: M.p. 80-85°C; UVjVIS (CHCI,): i
[nm] ( E ) = 390 (154600) 639
19). 612
(39300); MS (70eV): n7/: 778 (M'. 1.4%). 626 ( M - C , H , , O , .
( M + - C q H , o O , . 71), 539 (612-CHzCO2CH,, 57) 538 (612-CH,C02CH,,
35): High-resolution MS: rnir for
43). 150 (C,H,(OH),CH,CH=CH:.
calc. 778.3578, found 778.3568.
rue-lOa, b: Binary mixture of diastereomers: m.p. 82-86 'C; UV/VIS (CHCI,):
A,,, [nm] (6) = 391 (162300), 640 (40900); MS (70eV): mi: 940 ( M ' , 3%).
-2H. 3). 626 (MI-C,,H,,O,.
- 2 H . 19). 612
684 (M+-C,,H,,O,
(M' -C,,H,,O,,
48), 538 (612-CH3CO,CH,. 89), 330 (C,,H,,O,+. 48):
High-resolution MS: mii for C,,H,,N,O, calc. 940.4986, found 940.4949.
ruc-11: M.p. 17X ' C ; UV/VIS (CHCI,): i,,, [nm] ( E ) = 289 (18400). 372
(34100).409(98500), 544(5400). 570(7900),614(47400), 'H N M R (360 MHz.
CDCI,): d = 1.77 (s, 3 H. CH, on C-2). 3.79. 3.82 (AB system. JAR= 16.9 Hz,
2 H, CH, on C-2). 8.56, 8.68, 9.39, 9.40, 9.42 ( 5 s, 5 H. 5-, 8.. 10.. 15.. 20-H);
M S ( 7 0 e V ) : m / r 6 8 2 ( M t with '&Ni. 100%).609(M+-CH,CO,CH,CH,, 72).
ruc-14: M.p. 195 C: UV:VIS (CHCI,): A,,, [nm] (6) = 404 (154800). 484sh
(5800). 504 (10100), 540 (8900). 585 (5100). 642 (35800); ' H NMR (360 MHr,
CDCI,): 6 = -3.02. -2.84 (2 s, 2 H, NH), 1.95 (s. 3 H. CH, on C-2),
(AB system. J,, = 17 Hz, 2 H. CH, 011 C-2), 9.05. 9.10. 9.88. 9.90. 9.93 ( 5 s.
5 H, 5-. 8-, lo-. 15-, 20-H); MS (70eV): nij; 626 ( M t .100%), 553
(M' -CH,CO,CH,, 29).
Received: July 14, 1992 [Z54641E]
German version: Angrw. Chem. 1992, 104, 1650
CAS Registry numbers:
rue-3,101544-04-1; rac-4 ( Z isomer), 144320-56-9; rac-4 (Eisomer), 144407-374; ruc-5 ( Z isomer), 138749-68-5; rue-5 (Eisomer). 138608-12-5; rue-6, 14432057-0; roc-7, 144320-47-8; rue-8, 144320-49-0; rue-9, 144320-51-4; IOa, 14432053-6; l o b , 144407-36-3; rac-11. 144320-58-1; ruc-12. 144320-59-2; rue-13 ( Z
isomer), 144320-60-5; rac-13 ( E isomer), 144407-38-5; ruc-14, 14432048-9; 15, 1194-98-5; 16. 144320-50-3; 17, 53-16-7; 18, 144320-54-7; 19,
144320-52-5; 20, 144320-55-8; (H,CO),P(O)CH,CO,C(CH,),.
[(H,C,),PCH,CH,CH(OCH,)J+ Br-, 86608-70-0;(H,CO),P(O)CH,CO,CH,.
[l] H. Brockmann Jr. in The Porphyrins, Vol. 2 (Ed.: D. Dolphin), Academic
Press, New York, 1978, pp. 287-326.
[2] a) E. Lederer, C. R. Acad. Sci. 1939, 209. 528-529; b) J. A. Ballantine,
A. F. Psaila, A. Pelter, D. Murray-Rust, V. Ferrito. P. Schembri, V. Jaccarini, J Chcm. Soc. Pc,rkm Puns. 1980, 1080-1089; c) F.-P. Montforts,
C. M . Muller. A. Lincke. Liebigs Ann. Cliem. 1990.415-418; d) R. Deeg.
H.-P. Kriemler, K.-H. Bergmann, G. Muller, Hoppe-Sej'lerk 2. Physinl.
Chem. 1977, 358, 339-352; e) K.-H. Bergmann. R. Deeg, K . D. Gneuss,
H.-P. Kriemler. G. Muller, ibid. 1977. .?58, 1315-1332: f ) M. lmfeld, D.
Arigoni. R. Deeg, G. Muller in Vitamin B,, (Eds.: B. Zagalak, W.
Friedrich), de Gruyter. Berlin. 1979, pp. 315-316; g) C . Sotinou, C. K .
Chang, J. Am. Cheni. Soc. 1988, 110. 2264-2270: h) R. Timkovich. M . S.
JC VCH VerlagsgesellschufimhH, W-6940 Weinhrrm, 1992
Cork. R B. Gennis. P. Y Johnson, ibicl. 1985,107,6069-6075; I) P. Karuso, P. R. Bergquist, J. S. Buckleton, R. C. Camhie, G. R. Clark, C. F.
Rickard, Terrahedrnn Let/. 1986, 27, 2177-2178; j) K. Sakata, K . Yamamoto, H. Ishikawa, A. Yagi, H. Etoh. K. Ina. ihid. 1990, 3 f . 11651368; k) K. C. Bible. M. Buytendorp. P. D. Zierath, K . L. Rinehart, Proc.
Nut/. Acud Scr. U S A 1988, 85, 4582-4586.
[3] a) J. Deisenhofer. 0 . Epp. K . Miki. R . Huher. H. Michel, J Mol. Bml.
1984. 180. 385-398: b) R. Huber. Angew. Cl7em. 1989, 101. 849-871:
Angew. Chem. Inr. Ed. Engl. 1989. 28. 848-869; c) J. Deisenhofer. H.
Michel. ibrd. 1989, 101, 872-892 and 1989, 28. 829-847.
[4] a) H . van den Bergh, P. Cornaz, Nachr. Chem. Tech. Lub. 1985. 33. 582589; b) T. J. Dougherty. J. H. Kaufmann. A. Goldfarh. K . R. Weishaupt.
D. Boyle, A. Mittleman, Cancer Res. 1976, 38, 3628; c) T. J. Dougherty in
Merhods in Porpli,vrrn Plintosc.n.Fitilcrrinn (Ed.: D. Kessel). Plenum. New
York. 1985, pp. 313-328: d) S. Beckmann, T. Wessel, B. Franck, W. Honle,
H. Borrmann, H. G. von Schnering, Angew. Chrm. 1990,102.1439 -1 441;
Angrw. C%eni.Inr. Ed. Engl. 1990, 29, 1395; e) F:P. Montforts. A. Meler,
G. Haake, F. Hoper, Telruhedron Lett. 1 9 9 1 , 32, 3481-3482.
[ 5 ] a ) F.-P. Montforts. G. Ziinmermann, Angel$. Chem. 1986, 98, 451-452:
Angrbr. C h m Int. Ed. Engl. 1986, 25. 458-459: b) G. Hadke, A. Meler.
F.-P. Montforts, G. Scheurich, G. Zimmermann. Lirbigs Ann. Chem. 1992,
[6] a) G. M. Anstead. J. L. Ensign, C. S. Peterson, J. A. Katzeneilenbogen, J
Org. Chcm. 1989,54,1485- 1491: b) R. Hahnel, E. Twaddle, T. Ratajcrak,
J Steroid Biochem. 1973, 4, 21; c) A. Vessieres. S. Top, C. Vaillant, D.
Osella, J.-P. Mornon, G. Jaouen, Angew. Chrm. 1992, 104, 790-792;
Angrw. Chrm. Inf. Ed. Engl. 1992, 31, 753 - 755.
[7] a) F.-P. Montforts, F. Romanowski, J. W. Bats, Angew. Chem. 1989. 101.
471 473; Angew. Chem. lnt. Ed. Engl. 1989. 28, 480-483: h) F.-P. Montforts, G. Mai. F. Romanowski. J. W. Bats. Telruhedrun Lerr. 1992. 33 ,
[S] ruc-11: Triclinic. space group P,. a = 13.250(2). b =16.315(2). c =
17.757(6) A, a = 100.28(2), /{ = 108.96(2), 7 = 107.44(1) , V = 3298(3) A'.
Z = 4 (two independent molecules). p.,,, =1.377 gcm-3,fi(Cu,,) =
12.7 cm-'. The structure was determined by direct methods (Multan 80
program). R ( F ) = 0.120 for the 3864 reflections employed. Enraf-Nonius
CAD-4 diffractometer; SDP program system. Further details of the crystal
structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftllch-technische Information
mbH. D-W-7514 Eggenstein-Leopoldshafen 2 (FRG) on quoting the depository number CSD-55235, the names of the authors, and the journal
[9] The ruffling in the structures of the two independent molecules IS described
by d,, parameters of 0.21 and 0.17 A. For a definition of dmcf. a) C.
Kratky. R. Waditschatka, C. Angst, J. E. Johansen, J. C. Plaquevent, J.
Schreiber. A. Eschenmoser. Heh. Chin7. Actu 1985. 68, 1312-1337; h) A.
Eschenmoser, Angao. Chem. 1988. 100, 5 - 40; Angew. Chrm. Int. Ed. Enpl.
1988, 27, 5.
I:lo] R. Hunter. B. Bartels, J. P. Michael, Terruhedron Lett. 1991. 32. 1095
KCeSe, : A New Solid-state Lanthanide
By Anthony C . Sutorik and Mercouri G. Kanatzia'is*
Although interest in both solid-state and soluble metal
polychalcogenide compounds has increased over the last few
years, the extension of this work to the lanthanides and
actinides has yet to be fully realized. At present only a handful of these compounds have been confirmed to possess polychalcogenido ligands, although several others are suspected
to by analogy."] Rare earth metals are highly oxophilic,
which precludes the use of oxygen-containing solvents commonly employed for solution reactions. A preparative
[*] Prof. Dr. M. G. Kanatzidis, A. C . Sutorik
Department of Chemistry and
Center for Fundamental Materials Research
Michigan State University
East Lansing. MI 48824 (USA)
This work was supported by the National Science Foundation and the
NASA Graduate Student Researchers Program. The authors wish to
thank Isaac S. Sutorik and Gregori Kanatzidis for many stimulating and
productive discussions.
0570-0833j92jl212-lS94 $3.50+.25/0
Angrw. Chern. Inr. Ed. Engl. 1992, 31. No. 12
method which satisfies the requirements of being both oxygen-free and enables the use of large quantities of polychalcogenides is the molten salt technique. The use of molten
alkali metal polychalcogide fluxes as both reactant and media has been shown to give a wide variety of new alkali
metal/transition metal polychalcogenide compounds, especially when the reaction temperature is maintained within
the range of 250-400 "C, which favors polychalcogenide formation.". 3l We have studied the reactivity of lanthanides
and actinides in various alkali metal polychalcogenide fluxes. and we now report on the synthesis of KCeSe,, a new
solid-state lanthanide polychalcogenide compound with a
novel, but remarkably simple, structure, containing exclusively se;- units.
In the KCeSe, structure,[41Ce and Se form anionic layers
with K' ions in the cavity between the layers. The anionic
layers themselves are further partitioned into two layers of
Sez- units. which sandwich a layer of Ce3+ ions. The Ce3+
ions are in a square antiprismatic environment, coordinated
to the ends of eight diselenide ions, four above the Ce plane
and four below (see Fig. 1). The Sei- units point in one
Fig. 2. View along the L' axis of the anionic layers in KCeSe,. The CeJ ions are
represented by the eight-coordinate, shaded ellipses, and the Se atoms by the
nonshaded ellipses.
Fig. 1. Immediate coordination environment of CeJ' in KCeSe,. The Ce3+
ion is coordinated to one end of eight separate Se:- units in a square-antiprismatic arrangement. The Ce" ion has the point symmetry of 422 and the Se
atom resides on a mirror plane; hence, all Se atoms are crystallographically
equivalent. Selected bond lengths [A] and angles [-I: Ce-Se 3.075(1); Se-Se'
2.385(3): Se-Ce-Se" 69.92(3);Ce-Se-Se' 110.20(3).
direction within one layer and this direction is reversed in the
layer below. The net effect is such that when projected onto
the (001) plane, a pattern of two crosses with a common
center as inversion center is seen. Each Sez- unit bridges
four Ce3' ions, whereby each Se atom acts as a ,uzbridge;
the expanded anionic layer is shown in Figure 2. The K +
ions are not shown but are, in fact, colinear with the Ce3+
ions and are displaced from these by only half the length of
the c axis. Hence, except for their distances from the Seilayers, Ce3+ and K + have the same coordination environment. A further feature of this structure is the formation of
channels parallel to (IIO), which are bound on both sides by
Ce3+ and above and below by Sez- (Fig. 3). Their dimensions are 4.16 8, (Ce-Ce) by 3.61 A (Se-Se), and hence, they
are too small for intercalation of most species, although Li
intercalation may be possibile by the reduction of Sei- to
The repeating unit shown in Figure 1 is the same unit
which is found in two closely related three-dimensional
structure types: CuAI, and NbTe,. The former is found in
several compounds of the formula TX, (T = transition
metal, X = Sb, Ge, Sn, or Pb)."' It is simply the result of
fusing the anionic layers of KCeSe,, through face-sharing at
the square antiprisms, into a three-dimensional structure.
Indeed, since K and Ce share coordination spheres, KCeSe,
can be considered as a derivative of CuAI,, in which the two
AnKerl. Chmn. Inr. E d EngI. 1992. 31, N o . I2
Fig. 3. View of KCeSe, showing intralayer channels parallel to the (110)
planes. K + ions are included between the layers. The dimensions of the intralayer channels are 4.16 .& (Ce-Ce) by 3.61 (Se-Se).
cations alternate in the Cu positions along the c axis. The
NbTe, structure161is also closely related to CuAl,; the N b
cations reside in half of the Cu positions and are ordered
such that every second plane of metal positions is vacant.
forming a porous structure. NbTe, has Te:units,
analogous to the Se4- units in KCeSe,.
Previously, only two structure types had been known for
alkali metal(A) lanthanide(Ln) chalcogenide(Q) systems.
Both have the stoichiometry ALnQ,.['] The first type is simply a NaCl structure with the A + and Ln3+ ions randomly
distributed in the lattice. The second is the a-NaFeO, structure type, itself derived from the NaCl structure, in which the
two cations are partitioned into alternating layers throughout the lattice. Thus, KCeSe, represents a new structural
motif for a potential new family of alkali metal lanthanide
A solid-state far-IR spectrum of KCeSe, shows only a
broad absorption band beginning at 250 cm- '. A conductivity measurement on a pressed pellet using four probes was
performed at 300K. A value of 5.1 x lO-'Scm-'
found, indicating a semiconducting material. The diffuse reflectance spectrum of a microcrystalline sample of KCeSe,
measured in the range of 2500 to 190 nm shows an abrupt
absorption edge at approximately 780 nm, which suggests a
band gap in the neighborhood of 1.59 eV.
(uVCH Verlugsg~reNsrlzaftmbH, W-6940 Weinheim, 1992
oS70-0833i92iI212-1595$3.50+ .2SjO
CAS Registry numbers:
KCeSe,. 144586-78-7; K,Se. 1312-74-9; Se, 7440-45-1; Ce, 7782-49-2.
E 200
T [Kl
Fig. 4. Plot of l/x, vs. T ; data taken at 500 G for KCeSe, The inset graph
shows an expanded plot of the region between 2-50 K.
The magnetic susceptibility of KCeSe, was measured from
2 to 300 K at 500 G ; a plot of l/x vs. Tis shown in Figure 4.
KCeSe, appears to be paramagnetic, although several
anomalies in the data are present. At temperatures below
100 K, the curve deviates negatively from a straight line extrapolated from the higher temperature data. Similar deviations have been reported for several Ce3+ compounds and
have been attributed to crystal-field splitting of the cation's
'FSiz ground state.[g1 At temperatures above 100 K, the
Curie-Weiss law is not strictly adhered to, and a slight curvature remains in the data. In this temperature range an average peffvalue of 2.29 pB has been calculated. This value is in
accordance with the usual range for Ce"' compounds (2.32.5 pB) and is close to that of the free ion (2.54 pB) due to the
shielding effect the outer electron cloud has on the embedded
f orbitals.["] We found that the measurements must be done
on freshly prepared samples of KCeSe,; older samples tend
to give artificially high values for peff, implying a phase
change. This phase change probably occurs to a small extent
on the sample surface because the bulk of the sample remains
intact as shown by X-ray powder diffraction.
With the synthesis of KCeSe,, we have demonstrated that
alkali metal polychalcogenide fluxes can be employed to synthesize new lanthanide polychalcogenide materials. This,
along with the recently discovered molecular complex
[U(Se,)4]4-,[111 also synthesized from a molten salt flux,
opens the entire f block to further investigation. Given the
potential these metals have for eightfold coordination and
the known structural diversity of polychalcogenido ligands,
the possibilities for synthesizing new and novel structure
types become intriguingly vast.[*]
KCeSe, was synthesized from a reaction of K,Se (0.078 g. 0.5 mmol). Ce
(0.035 g, 0.25 mmol). and Se (0.158 g, 2 mmol). These starting materials were
thoroughly mixed in a glove box under a nitrogen atmosphere and loaded into
pyrex tubes, which were subsequently evacuated to approximately
mbar and flame-sealed. The mixture was heated at 300 'C for 6 days
and cooled at a rate of 2"Ch-I to 1OO'C then cooled to S O T in 1 h. The
product was isolated by dissolving away the residual polyselenide flux with
several portions of degassed dimethylformamide ( D M F ) under a nitrogen atmosphere until the solvent remained dear, indicating complete removal of the
polyselenide. The remaining material consisted of deep blue to black chunks of
KCeSe,. The oroduct was insoluble in D M F and was inert in both air and water
for extended periods, although some surface degradation was evidence in the
magnetic susceptibility studies. Homogeneity was confirmed by a comparison
of the product's powder X-ray diffraction against one calculated with X-ray
single-crystal data. A yield of 61 %, based on Ce. was typical.
Carbonyl substitution is thought to be an important step
in many syntheses and catalytic processes involving metal
carbonyls, and there is a considerable interest in methods of
assisting thermal substitution of CO ligands."] It was
thought that [Co(CO)J. like a number of mononuclear
18-electron carbonylmetalates, for example p(CO),] -,
[Mn(CO),]-, [Re(CO)J, does not react with either labeled
CO or phosphanes.['I However, it was recently shown that
alkali metal counterions accelerate the substitution reactions
Received: June 9, 1992 [Z 5396 IE]
German version: Angew. Cheni. 1992, 104, 1674
Mutual Catalysis of Neutral and Anionic Cobalt
Carbonyls in Their CO Scrambling Reactions**
By Gitiseppe Fachinelti* and Tiziana Funaioli
Experimental Procedure
[l] J. Flahaut in Hundhuok on the Physics and Chemisrry of Rare Earths:
Vol. 4 . Nun-Metallic Compuunds (Eds.: K. A. Gschneidner, Jr., L Eyring),
North-Holland, Amsterdam, 1979. p. 1. and references therein.
[2] a) M. G. Kanatzidis, Chem. Muter. 1990, 2, 353-363; b) M. G.
Kanatzidis, Y. Park, J Am. Chem. Soc. 1989. 111, 3767-3769; c) M. G.
Kanatzidis, Y Park, Chem. Muter. 1990, 2, 99-101; d) Y Park, M. G.
Kanatzidis, Angew. C h ~ m .1990, 102, 945-947: Angen.. C h m . h i . Ed.
Engl. 1990. 29, 914-915.
[3] a)S. A Sunshine, D. Kang, J. A. Ibers, J Am. Chem. Sue. 1987, 109,
6202-6204; b) D. Kang. J. A. Ibers, Inurg. Chem. 1988, 27. 549-551.
[4] Crystals of KCeSe, are tetragonal. space group P4/nhm (no. 125)
with u = 6.376(2), c = 8.329(1) A, V = 338.6(2) A', 2 = 2, QGn,' =
4.855 g ~ m - Measured
~ ;
reflections: 949; independent reflections: 916:
reflections with F: > 3 0 ( F , ) : 302. Complete anisotropic refinement
(11 variables), resulted in a final R = 0.039. R, = 0.049. Measurement
temperature 23 "2. Rigaku AFC6 diffractometer (Mo,, radiation,
[ f = 572.140 cm-', 20,,,
= 60.00"); structure was solved with TEXSAN.
empirical absorbtion correction (DIFABS). Further details of the crystal
structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technischeInformation
mbH. D-W-7514 Eggenstetn-Leopoldshafen 2 (FRG), on quoting the depository number CSD-56489. the names of the authors. and the journal
[5] F. Hulliger, Struct. Bonding (Berlin) 1968, 4. 83-229.
[6] K. Selte. A. Kjekshus, Actu Chem. Scundu. 1964. 1R, 690-696.
[7] a) Compounds of the type ALnQ, (A = Na; Ln = La, Ce, Pr, Nd; Q = S)
were first synthesized by Ballestracci and Bertaut (R. Ballestracci, E. F.
Bertaut. Bull. Sue. Fr. Mineral. Cry~rkdlogr.1964, 87, 512). They and
others expanded the range of compounds to include A = Li, K, Rb, Cs:
Q = Se; and several other lanthanides L, [7 b-h]. In general the compounds with large values for the radius ratio, rLn,+:rAIfavor the disordered NaCl structure. whereas smaller values (0.6-1.2) tend toward the
1-NaFeO, structure type [7i,j]; b) R. Ballestracci, E. F. Bertaut, ;bid. 1965.
88. 136: c) R. Ballestracci. [hid. 1965, 88, 207, d) M. Tromme. C. R.
S e a n m Acud.Sci. Ser. C. 1971,273,849; e) W. Bronger, R. Elter, E. Mans,
T. Schmidt, Rev. Chim. M f n e r . 1974, 10, 147; f) S. Kabre. M. Juhen-Pou201. M. Guittard. Bull. SUC.Chim. Fr. 1974, 10, 1881 ; g) C. M. Plug, G. C.
Verschoor, A m Cry.rtullogr. Sect. B 1976,32, 1856; h) T. Ohtani. H. Honjo, H. Wada, Muter. Res. Bull. 1987,22, 829-840: i) W. Bronger, Crysrullogrupliy und C r j s t u l Chemistry of Muleriuls n,ith Layered Structures (Ed. :
F. Levy). Reidel Dordrecht. 1976, p. 93; j) M. Brunei, F, DeBergevin, M.
Gondrand, J Phrs. Chem. S o l i h 1972, 33%1927.
[8] Recently we have succeeded in synthesizing and structurally characterizing
by X-ray diffraction a new phase isostructural to KCeSe,: RbCeTe,. The
space group of RbCeTe, is P4/nhm with u = 6.952(3) and F = 9.084(4) A.
The Ce-Te, Te-Te. and R b T e bonds are 3.285(1), 2.776(2) and 3.765(1) A.
respectively. R = 0.031, R , = 0.024.
[9] a) H. Lueken. W. Bruggemann. W. Bronger, J. Fleischhauer, J Les.T-Cunmun Met. 1979. 65, 79-88; b) M. Duczmal. L. Pawlak, J Mugn. Mug".
Muter. 1988, 76-77, 195-196.
[lo] N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon
Press, 1984, p. 1443.
[ l l ] A. C. Sutorik, M. G. Kanatzidis, J. Am. Chem. Sue. 1991, 113,7754-7755.
VCH Verlugsgesellschaft mbH, W-6940 Weinheim, 1992
Prof. Dr. G. Fachinetti, Dr. T. Funaioli
Dipartimento di Chimica e Chimica Industriale Universita di Pisa
Via Risorgimento, 35, 1-56106 Pisa (Italy)
[**I This work was supported by Minister0 dell' Universita e della Ricerca
Scientifica e Tecnologica (MURST). We thank Dr. G. Fochi for helpful
Angew. Chem. Inr. Ed. Engl. 1992, 31. Nu. 12
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