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Isolated and Condensed Ta2Ni2 Clusters in the Layered Tellurides Ta2Ni2Te4 and Ta2Ni3Te5.

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solution should provide information about electron delocalization within a given bpy unit and over the three bpy groups
of the ligand, a feature of special significance for an expanded atom description.[201Conductivity and magnetic properties are also of much interest. Furthermore, it might be possible to extend the list of such molecular "elements" from
sodio-cryptatium to doubly reduced calcio-cryptatium and
to triply reduced lanthano-cryptatium, for instance.
Received: February, 4, 1991 [Z 4422 IE]
German version: Angew. Chem. 103 (1991) 884
CAS Registry numbers:
"a@ c l]Bre, 134055-00-8; "ae
CH,CN, 134055-02-0.
134055-01-9; [Na@c l]eQ.
[11 J. M. Lehn, Ace. Chem. Res. I f (1978) 49.
[2] J.-M. Lehn, Pure Appl. Chem. 52 (1980) 2303.
[3] R. H. Huang, M. K. Faber, K. J. Moeggenborg, D. L. Ward, J. L. Dye,
Narure (London) 331) (1988), 599.
[4] J. L. Dye, Science (Washinglon D.C.) 247 (1990) 663; Pure Appl. Chem. 61
(1989) 1555.
[5] See ref. [2], footnote on page 2310.
[6] Note also the species Li(NH,), described as [Lie(NH,),ee] [6a] and
N(CH,), [6b] formed by electrochemical reduction of the corresponding
[7] a) N. Mammano, M. J. Sienko, J. Am. Chem. SOC.90 (1968) 6322; b)
R. K. Quinn, J. J. Lagowski, J. Phys. Chem. 72 (1968) 1374; J. 0. Littlehailes, B. J. Woodhall, Discuss. Faraday SOC.45 (1968) 187.
[8] J.-C. Rodriguez-Ubis, B. Alpha, D. Plancherel, J.-M. Lehn, Helv. Chim.
Acra 67 (1984) 2264.
[9] The electrochemical reduction of a colorless 1 mM solution of
[Naa c l]Bre containing 0.1 M tetrabutylammonium hexafluorophosphate (Bu,NPF,) in D MF was conducted on a glassy carbon working
electrode using a Pt coil as counter electrode and an Ag"/AgBr reference
electrode. Fc was added as an internal reference to measure the potentials;
the sweep rate was 100 mVsec-'. Potentials versus saturated calomel electrode (SCE) are obtained by subtracting 0.4 V ; see R. R. Gagne, C. A.
Koval, G. C. Lisensky, Inorg. Chem. 19 (1980) 2854; G. Gritzner, J. Kuta,
Pure Appl. Chem. 56 (1984) 461.
[lo] Y. Ohsawa, M. K. De Armond, K. W. Hanck, D. E. Morris, D. G. Whitten, P. E. Neveux, Jr., J. Am. Chem. SOC.105 (1983) 6522.
[I I] The electrocrystallization cell was made by our own glassblower and consisted of an H-type arrangement with a glass frit (porosity no. 5) separating
the two compartments. The compartments were coupled to the high vacuum independently, in order to be able to distill the solvent through the
vacuum line directly into them, without going through the glass frit. In this
fashion, it was possible to save complex by placing typically, 7 mg in only
one of the compartments along with enough supporting electrolyte
(Bu,NPF,) for a 0.1 M solution, while using only electrolyte in the other
compartment. The typical vacuum obtained was ca. 10-5-10-6 mm. The
current was controlled with a current source made in the institute. In this
two-electrode configuration, both electrodes were Pt wires, 0.7 mm in diameter and ca. 3 cm long. The optimal current was 10 pA and a typical run
was complete in 15 hours. After this period deep blue-violet crystals of
pyramidal shape had formed on the cathode (Fig. 1); they were of optimal
size and qualitity for X-ray analysis. For removal from the cell, the vacuum
was broken with purified Ar, and the electrode removed and placed in a
Schlenck tube. After selection under the microsope of several crystals for
X-ray analysis, the electrode was taken out of the Schlenck tube under a
strong nitrogen flow, the highly air-sensititve crystals were removed from
the Pt surface, and one was quickly selected and mounted for X-ray
analysis all under a constant cold nitrogen stream.
[I21 a) Crystal data: C,,H,,N,Na, M, = 638.74, tetragonal, space group I4,,
a=14.685(4), c = 14.731(4)& V=3176.7A3, eclled=1.335gcm-',
Z = 4, p(Cu,,)=7.392 cm-' (graphite monochromator). A total of 1021
reflections were collected using a Philips PW 1100/16 automatic diffractometer. Quantitative data were obtained at - 100°C using a locally built
gas flow device. The resulting data set was analyzed using an Enraf-Nonius
SDPjVAX package [12b]. Three standard reflections measured every hour
during the data collection period showed no significant trend. The raw
step-scan data were converted to intensities using the Lehmann-Larsen
method [I 2c] and corrected for Lorentz, polarization, and absorption factors. The structure was then solved with SIR [12d] and relined to
R = 0.036 using 897 reflections with I > 3u*(1). b) B. A. Frenz: The EnrufNononius CADI-SDP in H. Schenk, R. Olthof-Hazekamp, H. Van Koningveld, G. C. Bassi (Eds.): Computing in Crysrallography Delft University
press 1978, 64-71; c) M. S. Lehmann, F. K. Larsen, Acra Crystallogr.
Sect. A 3 0 (1974) 580; d) M. C. Burla, G. Cascarano, G. Giacovazzo,
A. Nunzi, G. Polidori, Acra Crystallogr. A 43 (1987) 370. e) Further details
of the crystal structure investigations are available on request from the
Verlagsgesellschafi mbH, W-6940 Weinheim, 1991
Director of the Cambridge Crystallographic Data Centre, University
Chemical Laboratory, Lensfield Road, GB-Cambridge CB2 1EW (UK),
on quoting the full journal citation.
[13] A. Caron, J. Guilhem, C. Riche. C. Pascard, B. Alpha, J.-M. Lehn, J.C. Rodriguez-Ubis. Heh. Chim. Aciu 68 (1985) 1577.
1141 Y Ohsawa. M:H. Wangbo, K. W. Hanck, M. K. De Armond, Inorg.
Chem. 23(1984) 3426.
[I51 W. Kaim, Cltem. Ber. 114 (1981) 3789 and references therein; T. Takeshita,
N. Hirota, J. Am. Chem. Soc. 93 (1971) 6421.
[16] The neutral species precipitated after two-electron reduction of the parent
complexes [M(bipy),lZe in CH,CN; they have been studied by ESR in the
solid state and in DMF solution; see A. G. Motten, K. W. Hanck,
M. K. De Armond, Chem. Phys. Lett. 79 (1981) 541; D. E. Morris,
K. W. Hanck, M. K. De Armond, J. Am. Chem. SOC.105 (1983) 3032;
D. E. Morris, K. W. Hanck, M. K. De Armond, Inorg. Chem. 24 (1985)
[17] A. Kaifer, L. Echegoyen. D. A. Gutowski, D. Goli, G. W. Gokel, 1 Am.
Chem. Soc. 105 (1983) 7168; H. Bock, B. Hierholzer, F. Vogtle, G. Hollmann, Angew. chem. 96 (1984) 74; Angew. Chem. Int. Ed. Engl. 23 (1984)
57; R. E. Wolf, Jr., S.Cooper, J. Am. Chem. SOC. 106 (1984) 4646;
. Gokel,
D. A. Gutowski, M. Delgado. V. J. Gatto, L. Echegoyen, G. W
ibid. 108 (1986) 7553; H. Bock, H.-F. Herrmann, ibid. f f f (1989) 7622.
[IS] The crystal structure of the dimer of a fluorenone radical contact ion pair
has been reported earlier: H. Bock, H.-F. Herrmann, D. Fenske, H. Goesmann, Angen. Chem. 100 (1988) 1125; Angen. Chem. Inr. Ed. Engl. 27
(1988) 1067.
[I91 M. K. De Armond, M. L. Myrick, Arc. Chem. Res. 22 (1989) 364 and
references therein.
[20] An intriguing case of spherical delocalization would be represented by a
"fullerium" species derived from a fullerene such as C,,, containing a
metal ion M"" in the internal cavity and n electrons on the carbon framework, ([M"@c C,,]nee). For the redox behaviour ofC,, see: P.-M. Allemand, G. Srdanov, A. Koch, K. Khemani, F. Wudl, Y. Rubin,
F. Diederich, M. M. Alvarez, S . J. Anz, R. L. Whetten, J. Am. Chem. SOC.
f f 3(1991) 2780 and references therein.
Isolated and Condensed Ta,Ni, Clusters in the
Layered Tellurides Ta,Ni,Te, and Ta2Ni,Te5**
By Wolfgang Tremel*
Dedicated to Professor Hans Georg von Schnering
on the occasion of his 60th birthday
Chalcogenides of the early transition metals have been
intensively investigated in recent years owing to their physical properties (e.g., anisotropic optical and electrical properties, superconductivity, charge density waves)."' However,
nearly all preparative investigations have been limited to
sulfides and selenides.i21Until very recently, tellurides were
ignored,L31even though their chemical uniqueness is already
indicated by a comparison of simple binary compounds with
analogous formulas: NbSe, I4'-one of the best-studied inorganic compounds-has no counterpart among the tellurides;
HfTe,['] and TaTe,,I6' in turn, have no counterpart among
the sulfides and selenides. Although the trichalcogenides
MQ, (M = Ti, Zr, Hf; Q = S, Se, Te) are similar in terms of
formula and structure for the sulfides, selenides, and tellurides,['] the compounds exhibit significant differences in
their properties.[']
The starting point of our work was an investigation of the
electronic structures of the layer compounds MTe, (M = Hf,
Ta, W, Re).['] The crystal structures of these compounds are
derived from the CdI, structure. The HfTe, structure (do
system) corresponds to the CdI, aristotype.1". ''I TaTe,
Dr. W. Tremel
Anorganisch-chemisches Institut der Universitat
Wilhelm-Klemm-Strasse 8, W-4400 Munster (FRG)
[**I This work was supported by the Bundesministerium fur Forscbung und
Technologie (grant number 05439 GXB 3).
0570-0833/91j0707-0840$3.50 i
Angew. Chem. Inl. Ed. Engl. 30 (1991) No. 7
(d1),[I2]WTe, (d2),[13]and ReSe, (d3), [141 on the other hand,
represent structural variants whose metal partial structures
are distorted in a way characteristic of the respective band
occupation. Analysis of the band structure in this series of
compounds showed that the changes in structure are induced
ele~tronically!~]An interesting partial result of this investigation was the finding that, in TaTe, the Ta-Ta bonding
orbitals are not completely occupied; therefore, modification of the structure should be possible by, for example,
inclusion of cations.
Surprisingly, the reaction of Ta, Te, and Ni did not
lead to inclusion of Ni in the interlayer regions, but instead
to the novel layer compounds Ta,Ni,Te,
Ta,Ni,Te, ,[”, I 9 ] which contain isolated and condensed
Ta,Ni, cluster units, respectively. In both compounds, the
layers are held together by van der Waals interactions only
2 3.846(2) 8,).
The structure of Ta,Ni,Te, can be described starting from
a hexagonal close packing of Te atoms; one-half of the octahedral holes in this packing are occupied by Ta atoms and
one-quarter of the tetrahedral holes are occupied by Ni
atoms. As illustrated in Figure 1, this description reveals the
structural relationship to the NiAs and CdI, structure. Figure l a shows a projection of the NiAs structure along c.
Removal of every second layer of metal atoms in planes
parallel to bc (open circles) results in formation of a (fictitious) TaTe, layer structure. The distortion of the TaTe,
partial structure by movement of the Ta atoms in the directions shown by the arrows and the partial occupation of the
tetrahedral holes (marked by black points in Fig. la) leads to
the structure of Ta,Ni,Te,. Pairwise shift of the Ta atoms
away from the centers of the octahedral holes of one layer
results in a coordination of the Ta atoms by 4 + 2 Te atoms
(dT,-,,:2.789 and 3.235 8,).
Noteworthy are the following points: (1) The known CdI,
structure type is derived from the NiAs structure by removal
of every second layer of metal atoms in planes parallel to ab.
The two structures thus differ only in the arrangement of the
metal layers. This gives rise to the question why only the
CdI, structure type is observed. (2) In the (fictitious) TaTe,
structure, tetrahedral holes exist between the layers and
within the layers, but only the latter are occupied. Presumably, therefore, this “alternative” structural variant is
stabilized by inclusion of Ni atoms within the layers.[201The
occupation of the octahedral and tetrahedral holes within a
layer results in rhombuslike Ta,Ni, clusterstz1](dNi-Ni
2.503(6), dTa-Ni
= 2.646(2) A), which are linked through
longer Ta-Ni and Ta-Ta contacts (dNi-Ta
= 2.873(3),
= 3.196(1), 3.236(2) 8,) to form a two-dimensional
network (Fig. 2).
Fig. 2. Ta2Ni,Te,, parallel projection of the metal lattice along [OlO] (large
circles, Ta; small circles, Ni).
Fig. 1 . a) Derivation of the Ta,Ni,Tee, structure from the NiAs structure; parallel projection along [OOI] (large circles, Te; medium-sized circles, Ta). For
explanationsee text. b) Parallel projection of the Ta,Ni,Te, structure on a layer
along [OlO](large circles, Te; medium-sized circles, Ta; small circles, Ni). The
different Ta-Te distances are symbolized by differing lines joining the atoms
(solid line, d,,-,, = 2.789 A; dashed line dTa.Tc = 3.235 A).
Angen. Chem. Ini. Ed. Engl. 30 (1991) No. 7
The Ni-Ni distance in the Ni,Ta, clusters is nearly identi=
cal with the Ni-Ni distance in Ni metal (dNi-Ni
2.492 8,);t221
an assessment of the Ni-Ta distance of 2.646 8,
is possible by comparison with the metal-rich sulfidic phase
Ta,Ni,S,1231 (dTa-Ni
= 2.495 A).
The second compound obtained upon reaction of TaTe,
with nickel, Ta,Ni,Te,, like Ta,Ni,Te,, has a layer structure.
Figure 3 shows projections of the structure along b (Fig. 3a)
and a (Fig. 3b). Each unit cell contains two Ta,Ni,Te, layers,
which are stacked along a, and each layer has two chemically
distinguishable Ni positions. Ni atoms of type A display
short distances to two other Ni(A) atoms and Ni atoms of
type B exhibit no Ni-Ni contacts.
A possible structural description is based on the hierarchy
of interatomic distances. All Ni atoms are coordinated in a
(distorted) tetrahedral fashion by Te
= 2.562 8,
(3 x ), 2.744 8, (1 x ); JNi(B)-Te
= 2.553 8, (4 x )), and the Ta
atoms are surrounded in a square-pyramidal fashion by five
Te atoms (dTa-T,= 2.757 8, (1 x), 2.785 8, (2 x ), 2.869 8,
(2x )). Furthermore, each metal atom displays other metalmetal contacts. The Ni(A) atoms have two further Ni(A)
(dNi-Ni= 2.502 8,) and three Ta neighbors
= 2.648 8, (1 x ), 2.717 8, (2 x)) and the Ta atoms
possess five Ni neighbors (d,,-Ni(A)
= 2.648 8,(1 x), 2.717 8,
Veriugsgeseilschuji mbH. W-6940 Weinheim. 1991
3 . 5 0 i .25jO
Fig. 3. Ta,Ni,Te,: a) Perspective view of a section of the layer structure along
[010]. b) Parallel projection of a layer along [loo] (dotted circles, Te; hatched
circles, Ta; cross-hatched circles, Ni (A); open circles, Ni (B)).
tron-deficient 4d and 5d metals is not surpri~ing[~~1-remarkable, however, is the occurrence of condensed clusters
in typical layer compounds. Some of the few known examples are ZrC1,[25]TbC1H,-,,[261 and Gd,C1,Cz,[271where
octahedral metal clusters are condensed to form two-dimensional layers. Also remarkable is the occurrence of layer
compounds for nonmetal/metal ratios of 1 / 1 . Here, too, the
low-valent zirconium halides (e.g., ZrC1) are a prime example. Presumably, therefore, the “isoelectronic correlation”
Zr-C1 and Ta-Te is not a mere coincidence.
Metallic properties are expected for both compounds,
Ta,Ni,Te, and Ta,Ni,Te,,1z81 as shown by an attempt to
assign formal oxidation numbers on the basis of electronegativity considerations (e.g., (TaZ0),(Ni2@),(Teze), or
(Ta3@),(Ni’e)2(Te2e), for the former and (Ta2@),(NiZ@),(TezQ), for the latter). Band-structure calculations of the
LCAO type (EH approximation)IZg1confirm that this approach is basically correct. The calculated density of states
for Ta,Ni,Te, with the contributions of Ta and Ni (Fig. 5a)
shows the metallic character of the compound. The calculated Ta-Ta, Ta-Ni, and Ni-Ni overlap populations (COOP
diagram, Fig. 5b) indicate the relative strength of the respective metal-metal interactions. The numerical values of 0.040,
0.155, and 0.156/0.078 (dTa-Ni
= 2.646(2)/2.873(3) A) for
the Ni-Ni, Ta-Ta, and Ta-Ni overlap populations reveal the
importance of Ta-Ta and Ta-Ni interactions in comparison
to Ni-Ni interactions.
(2 x);
= 2.922 A (2 x)); Ni atoms of type B have
only four neighboring Ta atoms (d,,-Ni,B)
= 2.922 A).
A structural description in terms of polyhedra starts from
a chain of NiTe, tetrahedra. Ni (A) atoms are part of a chain
of edge-linked NiTe, tetrahedra and Ni(B) atoms part of a
chain of vertex-linked tetrahedra. Finally, the pyramidal
TaTe, building blocks are linked through five common edges
with five neighboring NiTe, tetrahedra.
More instructive for understanding the structure and for
elucidating the structural relationship of Ta,Ni,Te, and
Ta,Ni,Te, is to consider the partial “naked-metal’’ structure
of one layer (Fig. 4). The Ta,Ni,Te, structure also contains
Fig. 5. a) Density of states (DOS) for Na,Ni,Te,. Left: Total density (dashed
line) and Ni partial density. Right: Ta partial density. b) COOP diagram (left,
antibonding; right, bonding): solid line, Ta-Ta; dashed line, Ta-Ni (average);
dashed and dotted line, Ni-Ni. The Fermi level is marked by a horizontal line.
Fig. 4. Ta,Ni,Te,: Projection of the metal lattice along (1001(hatched circles,
Ta; cross-hatched circles, Ni(A); open circles, Ni(B)). Two of the rhombusshaped Na,Ni, clusters are highlighted by shading.
rhombuslike Ta,Ni, clusters, but, in this case, they are linked
through common Ta-Ni edges to give A[Ta,Ni,] chains; that
is, cluster condensation through trans edges results in one-dimensional infinite chains. These chains are joined through
the Ni(B) atoms to form a two-dimensional metal layer.
This structural description has mnemonic advantages. In
principle, the occurrence of clusters in compounds of elec-
\ ,
Verlagsgesellschuft mbH, W-6940 Weinheim. 1991
The high formation tendency of the title compounds and
the preferred formation of clusters instead of inclusion of the
3d metal in the interlayer region may be ascribed to the large
affinity between electron-deficient and electron-rich metals
(according to the generalized Lewis acid-base concept of
Brewer et al.[30]). This fact is also documented by the
synthesis of other related compounds such as M,FeTe,
(M = Nb, Ta), M,M’,Te, (M’ = Fe, Co; M = Nb, Ta),
TaMiTe, (M’ = Co, Ni) Ta,MTe, (M’ = Fe, CO),[~’],and
TaFe, +xTe3(x z 0.07).[321
Received: February 15, 1991 [Z 4442 IE]
German version: Angew. Chem. 103 (1991) 900
[I] See, for example, a) J. A. Wilson, A. D. Yoffe, Adv. Phys. /8(1969) 193; b)
J. A. Wilson, F. J. DiSalvo, S . Mahajan, ibid. 24 (1975) 117; c) P. Monceau
(Ed.): Elecrronic Properties of Inorganic Quasi One-Dimensional Compounds, Part 1 and 2 . Reidel, Dordrecht 1985; d) J. Rouxel (Ed.): Crystal
Chemistry and Properties of Materials with Quasi One-Dimensional Structures, Reidel, Dordrecht 1986; e) H. Kimamura (Ed.): Theoretical Aspects
0570-0833191jO707-0842 $3.50
+ .25/0
Angew. Chem. Int. Ed. Engl. 30 (1991) No. 7
of Band Structures and Electronic Properties of Pseudo One-Dimensional
Solids, Reidel, Dordrecht 1985; f) M. S . Whittingham, A. J. Jacobson
(Eds.): Intercalation Chemistry, Academic Press, New York 1982; g)
R. H. Friend, A. D. Yoffe, Adv. Phys. 36 (1987) 1.
[2] a) S . A. Sunshine, D. A. Keszler, J. A. Ibers, Acc. Chem. Res. 20 (1987)
395; b) A. Meerschaut, P. Grenouilleau, R. Brec, M. Evain, J. Rouxel, J.
Less-Common Met. 116 (1986) 229; c) J. Rouxel, R. Brec, Annu. Rev. Mater. Sci. 16 (1986) 137.
[3] a) NbNiTe,: E. Liimatta, J. A. Ibers, J. Solid State Chem. 71 (1987) 384;
NbPdTe,: E. Liimatta, J. A. Ibers, ibid. 77 (1988) 141; TaNiTe, and
Ta,Pd,Te,,: E. Liimatta, J. A. Ibers, ibid. 78 (1989) 7; b) TaTe,: S . Lee,
N. Nagasundaram, Chem. Muter. 1 (1989) 597; c) Ta,SiTe,: M. E. Badding, F. J. DiSalvo, Inorg. Chem. 29 (1990) 3952; d) An excellent review on
tellurium-rich tellurides: P. Bottcher, Angew. Chem. 100 (1988) 781 ;
Angen. Chem. Int. Ed. Engl. 27 (1988) 759.
141 a) A. Meerschaut, J. Rouxel, J Less-Common Mer. 24 (1975) 117; b) J. L.
Hodeau, M. Marezio, C. Rouceau, R. Ayroles, A. Meerschaut, J. Rouxel,
P. Monceau, J. Phys. C f 1 (1978)4117;c) forashort review see S . Kagoshima, H. Nagasawa, T. Sambongi: One-Dimensional Conductors, Springer,
Berlin 1988, Chapter 4.
[5] S . Furuseth, L. Brattis, A. Kjeksbus, Acra Chem. Scand. 27 (1973) 2367.
[6] E. Bjerkelund, A. Kjekshus, J. Less-Common Met. 7 (1964) 231.
[7] W. Kronert, K. Plieth, Z . Anorg. Allg. Chem. 336 (1963) 207; L. Brittas,
A. Kjekshus. Acta Chem. Scand. 26 (1972) 3441; Acta Chem. Scand A29
(1975) 623.
[8] See, for example, E. Canadell, Y. Mathey, M.-H. Whangbo, J. Am. Chem.
Soc. 110 (19SS) 104, and references cited therein.
[9] J:G. Smeggil, S . Bartram, J. Solid State Chem. 5 (1972) 391.
[lo] H. D. Megaw: Crystal Structures: A Working Approach, Saunders,
Philadelphia 1973, p. 216.
[ I l l 9. E. Brown, Acta Crystallogr. 20 (1966) 264.
[I21 B. E. Brown, Acta Crysrolbgr. 20 (1966) 268.
[13] N. W. Alcock, A. Kjekshus, Acta Chem. Scand. 19 (1965) 79.
[14] W. Tremel, lnorg. Chem. 30 (1991), in press.
[I51 In order to synthesize Ta,Ni,Te,, the corresponding stoichiometric
amounts of the elements, together with I, as mineralizer, were heated in a
sealed quartz glass tube for 14 d at 1000°C. The product (EDAX (energy
dispersive X-ray spectroscopy): Ta, Ni, Te) consists of platelets with a
metallic luster and is a single phase according to the Guinier diagram.
[16] Space group Pmna (No. 53), Z = 2 (based on Ta,Ni,Te,), a = 7.897(1),
b = 7.228(1), c = 6.230(1) k, (Siemens R3), Mo,, (p = 51.60 mm-I);
crystal size, 0.04 x 0.035 x 0.035 mm3; 0-20 scan, 20,,,=75"C, 1734 reflections (h,k.+& empirical absorption correction, 807 symmetry-independent reflections, R(F,)/R, = 0.0646/0.0693. b) Further details in the
crystal structure investigations are available on request from Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische
Information mbH, W-7514 Eggenstein-Leopoldshafen 2 (FRG), by quoting the depository number CSD-55272, the names of the authors, and the
journal citation.
[I71 An independent structure determination of Ta,Ni,Te, was recently reported: J. L. Huang, B. G. Huang. Acta Crysrallogr. Sect. A 4 6 (Suppl.) (1990)
[lS] Ta,Ni,Te, was synthesized from the corresponding stoichiometric
amounts of the elements at 900°C in a sealed quartz glass tube (10 d) with
addition of TeCI, as mineralizer. The product (EDAX: Ta, Ni, Te) consists
of needles with metallic luster which are up to 1 cm long. The Pd analogue
Ta,Pd,Te, was synthesized under analogous conditions ( T = 850T ) . Lattice constants a = 13.989(3), b = 3.713(1), c = 18.630(4) A,space group
Pnmu (Nr. 62). Z = 4.
1191 Space group Pnma (No. 62), Z = 4, a = 13.897(4), b = 3.695(1),
c = 17.729(6)A (Siemens R3), Mo,, (p) = 45.49mm-'); crystal size,
0.006 x 0.03 x 0.15 mm3; w-20 scan, 28,,, = SO", 3321 reflections ( h , k , 0,
empirical absorption correction, 3158 symmetry-independent reflections,
2353 with 1>20(l), R(F,)/R, = 0.043/0.044 [16b].
[20] The preferential occurrence of the Cdl, structure type can be understood
on the basis of LCAO band-structure calculations (extended Huckel (EH)
approximation) and on the basis of symmetry arguments. The incorporation of nickel (and, in general, of elements of the iron group) in the tetrahedral holes of a layer of the TaTe, structure leads to their electronic
stabilization due to interaction of unoccupied I,,levels of tantalum with
the corresponding occupied levels of nickel: W. Tremel, unpublished results.
[21] The formulation Ta,Ni,Te, (instead of TaNiTe,) was chosen in order to
give the cluster formal recognition as well.
[22] CRC Handbook of Chemistry and Physics, 60th ed., CRC Press, Boca
Raton. FL (USA) 1980
[23] 9. Harbrecht, H. F. Franzen, J. Less-Common Met. 113 (1985) 349.
[24] A. Simon, Angew. Chem. 93 (1981) 23; Angew. Chem. Int. Ed. Engl. 20
(1981) I.
1251 A. W. Struss, J. D.Corbett, Inorg. Chem. 9 (1970) 1373.
1261 H. Mattausch, A. Simon, K. Ziebeck, J. Less-Common Met. 113 (1985)
[271 U . Schwanitz-Miiller, A. Simon, Z . Noturforsch. B 4 0 (1985) 710.
Angen. Chem. I n t . Ed. Engl. 30 (1991) No. 7
[28] W. Tremel, unpublished results.
[29] Extended Huckel approximation: R. Hoffmann, J. Chem. Phys. 39 (1963)
1397. H,, matrix elements: J. H. Ammeter, H.-B. Biirgi, J. C. Thibeault,
R. Hoffmann, J. Am. Chem. Sue. 100 (1978) 3686. Tight-binding approximations: M.-H. Whangbo, R. Hoffmann, ibid. 100 (1978) 6093; M.H. Whangbo, R. Hoffmann, R. B. Woodward, Proc. R. Soc. London A 366
(1979) 23. Parameters for Ta: J. Li, R. Hoffmann. M. E. Badding, F. J. DiSalvo, Inorg. Chem. 29 (1990) 3943; parameters for Ni and Te: J.-F. Halet,
R. Hoffmann, W. Tremel, E. Liimatta. J. A. Ibers, Chem. Muter. 1 (1989)
351. Special k points: R. Ramirez. M. C. Bohm, In!. J. Quantum Chem. 30
(1986) 391.
[30] L. Brewer, P. R. Wengert, Metal. Trans. 4 (1973) 83.
[31] W. Tremel, Habilitarionsschrft. Miinster 1991.
[32] E. Potthoff, W. Tremel, unpublished results.
[Cp,Fe,(CO),(p-SitBu * NMI)]I: The First
Silanetriyldiiron Complex**
By Yasuro Kawano, Hiromi Tobita, and Hiroshi Ogino*
The chemistry of mononuclear[lland dinuclearl2I carbyne
complexes is well established. However, there are no reports
on the analogous silanetriyl complexes. Here we wish to
report the synthesis and crystal structure of the first donorstabilized cationic silanetriyl diiron complex, 1 (NMI =
. NMI)]@
N-methylimidazole), which was isolated as 1-1.
The synthesis of 1-1 was achieved by exchanging an iodide
on the silanediyl bridge of the p-silanediyl complex 213]with
a strong Lewis base, NMI.
The unprecedented silanetriyl-bridged structure of 1-1was
determined unequivocally by an X-ray crystal structure analysis (Fig. l).I4I Coordination of the lone pair on the nitrogen
atom of NMI to the Si atom in the tert-butylsilanetriyl ligand
causes pyramidalization of the silicon atom (the angle between the Fe,Si plane and Si-C8 is 143.2'). The two Cp
rings, which are mutually cis, and the tert-butyl group are
located on the same side of the Fe,SiC bicyclic ring. The
distance between the Si and I atoms (5.388(2) A) is substantially longer than the sum of the effective van der Waals radii
of Si and I (4.08 A).['] This clearly indicates that there is no
chemical bond between Si and I. The plane of the five-membered ring of NMI is parallel to the Fe-Fe bond and the
NMI ligand is disordered between the two possible orientations related by a crystallographic mirror plane. The Fe-Si
[*I Prof. Dr. H. Ogino, Y Kawano, Dr. H. Tobita
Department of Chemistry, Faculty of Science
Tohoku University
Aoba-ku, Sendai 980 (Japan)
[**I This work was supported by the Nissan Science Foundation and by the
Ministry of Education, Science and Culture (Grant-in-Aid for International Scientific Research Program). NMI = N-methylimidazole.
Verlagsgesellschaft mbH, W-6940 Weinheim, 1991
OS70-0833/91/0707-0843S 3.50+ .25/0
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ta2ni2, ta2ni3te5, clusters, isolated, telluride, condensed, layered, ta2ni2te4
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