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Condensed RuSn6 Octahedra in Ru3Sn15O14.

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Condensed RuSn, Octahedra in Ru3SnI5Ol4**
Werner Reichelt,” Tilo Sohnel, O t t o . R a d e m a c h e r ,
Heinrich O p p e r m a n n , A r n d t Simon,* Jiirgen Kohler,
and Hansjiirgen M a t t a u s c h
The Sn0,,’Ru02system is of interest with regard to the electronic properties of dimension stable anodes (DSA).“] Detailed
studies of the ternary system Ru/Sn/0[21led to the discovery of
new oxygen-poor phases. From the compound described as
“RuSn,O,” by phase analysis, red translucent crystals can be
obtained in 21 tin melt.[31The X-ray structure analysis‘41of these
crystals gave the composition Ru,Sn, ,O,, s RuSn,O,,,,
good agreement with the composition RuSn, 950,,2
previously by systematic investigations of the phase equilibria
and electron beam microanalysis of single crystals.151Due to the
M:O ratio of greater than 1 for the compound, an unusual
structure wah expected. Indeed, the Ru,Sn,,O,, structure is
remarkable for several reasons.
The prqjection of the monoclinic unit cell parallel to [OlO]
(Fig. 1 ) shows characteristic triple chains of corner-sharing
RuSn, octahedra. They run in the direction of the projection
[Ol 01 and are surrounded from all sides by 0 atoms, which link
the strands partially together. Each strand has the composition
Ru,Sn,,O,,. A polyhedral representation of the arrangement
oftlie Sn atoms in the strand is given in Figure 2. In addition the
Fig I. Prqcclion 01 (lie unil cell of Ru,Sn,,O,, parallel lo [OIO] Thc R u , Sn. .ind
0 atoiii.\ arc diiiuti n i l h spheres of increasing siLe. and the RuSn,, octahedra are
highlighlcd i n llic t o p p u t ol‘thc figure. The Sn a t o m ( S n l l ) which docs not belong
to ;I RuSn,, octahedion I S marked with a n arrow. Heterododecane units of Sn and
ti betuecn the cluster \trands.
Do7 I l r . W Rciclielt, Dipl.-Chem. T. Siihnel. Dr. 0. Radrmacher.
Prof 1)r H Oppcrmnnn
Institur i i i i - 2ii~)i-g.iiiischcC‘heints dcr Tcchnischen UnibersiVat
Motiiiii.;cii\trar\e 13 D-01062 Dresden (Germany)
T c l e l ~ 1111 ~(ILIC
+ (351Ih43-72X7
Pro1 1h A SIIIIOI?.
I l r .I. Kahlcr. Dr. H . Mattausch
fur ~ o t k i i t - p c r l b r s c h u n g
Hciscnbcr~slr,i\c I, D 7 0 5 6 Y Stutlgart (Germany)
I**/We thanh l’rde\\or P. B d t c h e r and l’rofcssor H . G. \ o n Schnering for helpful
d i \ c i i \ ~ i i i i i ,ind
tlic Ikursche Forschunesgenieinschaft and the Volkswagen-
S t i l ~ u n g1,r liiiiitic1~11
Fig. 2. Strand ofcorner-linked RuSn, octahedra (left)and the rcprescntation o f t h e
Sn, ~etiahcdrarcsulting from tilting the octahedra (right)
structure contains a further Sn atom (Sn 1 1 ) marked with an
arrow in Figure 1, which does not belong to the assembly of the
strand. This Sn atom leads to the loss of the sqmmetry centers
(Cm instead of C2.!nz),whereas the variation of all other atom
positions from the higher symmetry is small. Thus, there are two
equivalent positions for the specially positioned Sn atom which
are linked through a pseudo inversion center in the center of the
strand. According to X-ray crystallographic
only one
position is occupied (Fig. 1 ) . Bond length-bond strength considerations[,. 71 show that the bonding around the occupied and
the empty position are completely equivalent, which is manifested in the uniform bond order sums near 2 for the participating
0 atoms. The discrete Sn atom is also divalent. The corresponding analysis of the Sn-O bonds for the Sn atoms in the strand
showed that all the terminal atoms likewise are divalent (type 1 :
Sn 1,2,3,4,5,6,8.10), whereas the atoms that function as linking
elements in the strand (type 2: Sn 7,9) have bond order sums of
almost 1 .[‘I The difference results directly from the coordination
of the Sn atoms: eight atoms of the type 1 form the apices of
SnO, pyramids such as in SnO. two atoms form the apices of
trigonal SnO, pyramids. The apices of the pyramids each point
towards the Ru atoms. The (four) atoms of type 2 are coordinated in a distorted tetrahedral fashion by two 0 and two Ru
atoms. The most striking structural feature in Ru,Sn,,O,, are
the corner-linked RuSn, octahedra. The Ru -Sn distances lie in
the range between 251 and 262 pm and the Sn -Sn distances
between 333 and 380 pm. RuSn, octahedra are also found in the
intermetallic phase Ru,Sn, .[‘‘I Here the Ru- Sn distances
are (2 x ) 282 and (4 x ) 259 pm. The RuSn, octahedron
is also known from the “inorganometallic complex”
[Ru(SnC1,),]4- .[‘*I
The linkage scheme given in Figure 2 is closely related to the
topology of the perovskite structure. In the latter. cornersharing TiO, octahedra are arranged parallel. In the GdFeO,
variantLt3]the octahedra are tilted towards one another. Those
in the strand found in Ru,Sn,,O,, correspond t o a one-dimensional section of this structure. However, the tilting of the octahedra in the strand is so extreme that Faces and edges of neighboring octahedra span almost regular tetrahedra, which in turn
are linked together through a face, edge, and two corners. Thus.
the sequence of the Sn atoms parallel to (001) corresponds to the
section from a hexagonal close packing arrangement.
The above comparison with the perovskite structure is a
rough simplification, in that in Ru,Sn,
metal octahedra are linked to one another. Systems of con-
densed clusters with such units, among others those with Ru a s
interstitial atom. are known for the electropositive rare earth
metals, however only in terms of the motif of the edge linkage.'14, ' 51 A diverse range of corner-sharing systems of metal
octahedra occur in metal-rich oxoniobates.['"' In contrast to
here strong homonuclear metal-metal bonds are
present, and the octahedra are empty. Indeed, the strand found
in the latter compound corresponds to a one-dimensional section from the layers of octrahedra in Ba,Nb,O, with a tilting of
the octahedra by about 30". Interestingly, the special direction
of this section in the metal-rich oxoniobates could so far not be
detected despite a directed search.
The band structure calculation on the basis of the extended
Hiickel method"', I s ] shows Ru,Sn,
to be a semiconductor
(Fig. 3 a), in agreement with the transparency of the compound.
The COOP analysis reveals that. as expected. no Sn-Sn bonds
but exclusively strong S n - 0 and R u - S n bonds are present.
_ L
Fig. 3. a ) Projected density of states for Ru,Sn,,O,,. b) C O O P curves for R u 3 Sn
and R u l -Sn interactions in the RuSii, octahedra (to the right bonding). R u l and
R u 2 a t o m s center the peripheral octahedra. Ru3 atoms the central R u S n , octahcdra. T h e COOP curves for Sn atoms of the same oxidation state are very similar
within a RuSn, octahedron and therefore are each represented as a sum in the
The corresponding analysis of the Ru- Sii interactions shows
very similar bonding for the peripheral Rul and Ru2 atoms,
however, considerably different bonding for the central Ru3
atom (Fig. 3 b). The difference may at first be surprising due to
the geometrically very similar coordination of the Ru atoms by
Sn atoms; however, it is simply the result of the already stressed
chemical dissimilarity of the Sn atoms. Up to the Fermi edge E,
only bonding Ru-Sn states are occupied. The upper edge of the
valence band is dominated by Ru-Sn' interactions, and, since
the central Ru3 atom is surrounded by four Sn atoms of this
type, the electronic structure directly below the Fermi edge is
particularly dominated by the states of this atom.
By using a simple approach. a picture of the distribution of
valence electrons can be developed, which explains the electronic localization. Starting from the oxidation state IJ for all Sn
atoms of the type 1 and the discrete Sn atom, an ionic limit
(Ru,Sn,/,)hi(Sn' t ) l o S n 2 + ( 0 2 - ) 1 4is reached . With the oxidation state I for the Sn atoms of the type 2 a possible charge
distribution follows according to (RuSn,.,)' +(RuSn,,,)$' with
a formally zero valent central Ru atom and monovalent peripheral R u atoms. The distribution is plausible since the Sn atoms
of the type 2 (3-electron donors) together with four and two
atoms, respectively, of the type 1 (2-electron donors) lead to the
I +
18-electron configuration for all Ru atoms: RuSn,Sn, with
8 e 4 x 1 i2 x 3 e 2 x 1 x 2 e = 18 e (central octahedron).
1 + 1 +
2 t
RuSn,Sn,with 7 e + 2 x I / 2 x 3 e + 4 x l x2e=lXe(peripherI'
a1 octahedra): the linking Sn (3e) counts half and the terminal
2 t
Sn (2e) is fully included in the count. Thus Ru,Sn,,O,, forms
a solid-state analogue of a hypothetical (polymeric) carbonylnitrosyl complex [Ru,(NO),(CO),,,]~
Received. J u n e 9, 1995 [ZX074IE]
German wrsion: A q w C/ic,m. 1995. 167. 2307 -2309
Keywords: clusters . ruthenium compounds . solid-state structures tin compounds
[I] C. Iwakura. K . Sakamoto. J. Elecrrodicm. Sot. 1985,132. 2420.
[2] O. Nichterwitr. H . Oppermann. W. Reichelt. Z . Atiorg. ANg. ('htwi. 1992,615.
[3] Synthesis f m m SnO>.'Ru,Sn,.O,,,'Sii,,,,,,,, o r Ru,Sn.,'Ru,Sn,
tures Thesewere heated to 1000 C i n 1 h . thencooled to700
subsequently cooled to room temperature without controlling the rate ofcooling. T h e single cryatols tire found in the Sn regulus and were extracted with
[4] Crystallographic data of Ru,Sn,,O,,. M = 2307.55 gmol-I. monoclinic. C'ni
(no. 8). er =1239.0(2). h =707 4(2). c =1290.8(3) pm. p =108.60(2) . 2 = 2.
=7.147 gcm-'. p,,,, =7.2(2) gem-'. 2603 measured reflections (CAD4.
f-Nonius). of which 2583 with I > Zu(1). T h e structure was solved by
direct methods. FMLS retiiieinent against f' ( S H E L X 93). Atomic positions:
R~ 1 : 0.69763(9). o.ooon. i1.693(~7(9):R~ 2 : o.~8424(9j,o.sooo. o . ~ i x 2 ( 9 j ;
R U 3 : 0.788~2(10).
0.5000. 0.96509(30): Sn I : 0.90146(8), n.oooo. O.X216X(X):
Sn 2: 0.48714(8). 0.0000, 0.58026(9): Sn 3: 0.74593(6), 0.74369(10).
0.57386(6): Sn 4: 0.59472(8). 0.5000. 0.33965(10); Sn 5 : 0.94243(9), 0.5000.
0.87329(10): Sn 6 : 0 651 IO(9). 0.5000. O.OXOOO(9): Sn 7: 0.66898(6).
0 75067(10). 0.83762(6) Sn 8: 0 17984(9),0.5000. 0.1 I191(9) Sn 9.0.4086616).
0.26267(10). 0.08877(6); Sn 10: O.X3666(6). 0.74117(11). 0.34677(6); Sn II:
0.51563(8). 0 5000. 0.61972(9): 0 1 : 0.9103(7), 0.2122(11). 0.5356(6): 0 2.
0.9606(12). 0 0000. 0 9917(9), 0 3 : 0.6204(10). 0.5000. 0.5257(9), 0 4:
0.1250(9). 0.5000. 0.9423(10); 0 5. 0.4237(1 I ) , 0.0000, 0.4109(9): 0 6:
0.3449(12). 0 0000. 0.6293(12): O 7: 0.7014(6). 0.7259(10). 0.4068(6); 0 8:
0 . 5 8 ~ 7 )0. 7 6 ~ 7 ( 1 1 )O. . I I X ~ ( X )O
: ~ I 0.9901(7).
o 7 ~ ~ 1 00.~177(6);
) .
o 100.7258(9).0.5000. 0.2516(9): K = 0.044. i i R 2 = 0.109. The rhombohedra1 arrangcnient ( a = 1290.8 pm. 1 = 31.74 ) which suggests it5elf is not ~ipplic;ible
;iccording to the splitting of thc rc!Jections in the powder diagram The occiiri-cnce of Cm (instend of C2:w) is clearly evident from the relinernent. T h e
cnlcu1;ition in C2:m without Siill gives R1 = 0 20 (wR2 = 0.47). with half-filIcd Sill 1 position K1 = 0.20 ( w R 2 = 0.28) Further details of the crystal structure investig;itioii may be obtained from the ~:achinformations~entrum
Karlsruhe, D-76344 Eggenstein-Leopoldshafen (Germany) on quoting the depository number CSD-401827.
IS] Ru =9XSmol%.Sn =48.891nol%.O =41.23moloh:T.SOhnel.W.Reichel~.
G. NichterwitL. 7 Vortragstagung dcr Arbeitsgruppe Festkorperchemie dei<;DCli. Bonn, 1994. Poster P O 11 66.
[bj with.\,(Sn - 0 )= [r/(Sn -O):1.86]-4.5 according to I. D. Brown [7] the following
bond ordcr suins Xs>(Sn 0) were obtained for S n l =1.86. Sn2 = 2.OX.
Sn3 = 2.03. Sn4 = 2.01. Sn5 =1.85, S n h =1.98. Sn7 = 0.8% Sn8 =1.95.
Sn9 = 0.93. SnlO = 2.04. S n l l = 2.09
171 1. D. BroNii in Srrircrrrrc trwd Bonding 111 Crymi/\, W. I1 (Eds.: M O'Keeffe.
A . Navrotsky). Academic Prcss. New York. 1981.S.1 fC.
[ X I Tin iilso exists 111 the unusual oxidation state + I in SrSnP [9.10]
[Y] B. Eisenmann. H. Jordan. H. Schgfer. J LewComnion Mer. 1986, 1 / 6 , 251
[lo] F. R. Wagner. Dissertation. Universitiit Saarbrucken. 1993.
[I 1 1 0. Schwomma. H . Nowotny. A. Wittemann. , W O ~ I U / . Y
/ ~ . 1964.9.7. 1538.
[I21 T. Yainakawa. H. Moriyama, S.Shinoda. Y Saito, I/ior,q-.C / x w . 1987.26. 3347.
(131 P Coppens. M . Eibacliiitz, A c / o Cr.v.$/d/oxr.1965, 19. 524.
(141 T. Hughhanks. .I. D. Corhctt. I m r g . C'/rcw7. 1989.28, 631.
(151 M . W Payne. P. K. Dorhout. S.-J. Kiin.T. R . Hughbanks, J. D. Corbett. /nor,q-.
(%rill. 1992, 31. 13x9
1161 J. Kohler. Ci. Svensson. A . Simon. Atigcu.. <'/wni. 1992. 104. 1463: Atzgwi.
c ' / l e w l . IHr. Ed. EllXl. 1992. 31, 1437.
[17] R. HoTfmann, J. C/iiwr. P/i?..s. 1963.39. 1397. If,,matrix elements: J H . Ammeter. H:B. Btirgi. J. C. Thibeault. R. Hoffmann, J. ,4171. Chon. Soc. 1978,100,
3686. Ti~ht-binding-approach:M -H. Whangbo, R. Hoffinaiin. 3 Am. C/
S O C1978, / M I . 6093. Special k points: R . Ramirez, M . C. Bohm. In/. J Qnun/imi U Z ~
I . 3 1 . 391 : R . H. Sunimerville. R . Hoffmann. J A m . C/icwi.S o [ .
1976.YK 7240.
[ I X ] J. Kiihler. P. Wunsch. PC-Version of the program E H M A C C (extended-Hiickel
program by M.-H. Whangbo. R . Hoffmann. modified by M. Evain. J. Mitchell). Slutlgart. 1991. Parameters for the E H calculations: atomic orbital
energics H,, [cV] (coefficiciits i,)
for 0: 2s -32.36 (2.275). 2p - I 4 8 (2.275):
S n : 4s - 16.16 (2.12). 4p -8.32 (1.82); R u . 5s - 10.4 (2.08). 5p -6.87 (2.04).
4d - 14.90 (5.38). Doublc functions \+ere used for R u : C , 0.5340. C 2 2.30. and
C 2 0.6365
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