Oligomeric Rare-Earth-Metal Halide Clusters. Three Structures Built of (Y16Z4)Br36 Units (Z = Ru, Ir)

Article abstract of DOI:10.1021/ic960650x

Suitable reactions in sealed Nb tubing at 850-950 °C gave good yields of a family of oligomeric cluster phases that were characterized by single-crystal X-ray diffraction means. The basic Y₁₆Z₄ units (?4? symmetry) can be derived from 2+2 condensation of centered Y₆Br₁₂Z-type clusters or as tetracapped truncated tetrahedra Y₁₆ that are centered by a large tetrahedral Z₄. These are surrounded by 36 bromine atoms which bridge edges or cap faces of the Y₁₆Z₄ nuclei and, in part, bridge to metal atoms in other clusters. The principal bonding appears to be Y-Z and Y-Br, with weaker Y-Y (d ? 3.70 A?) and negligible Z-Z interactions. The phase Y₁₆Br₂₀Ru₄ (P4₂/nnm, Z = 2; a = 11.662(1) A?, c = 16.992 (2) A?) is isostructural with Y₁₆I₂₀Ru₄ and with the new Sc₁₆-Br₂₀Z₄ (Z = Fe, Os). Syntheses only in the presence of Ir and ABr-YBr₃ fluxes (A = K-Cs) produce Y₁₆-Br₂₄Ir₄ (Fddd, Z = 8; a = 11.718(3) A?, b = 22.361(7) A?, c = 44.702(2) A?), in which the electron-richer Ir interstitials are compensated by four additional bromine atoms and altered bridging between macroclusters. Larger amounts of YBr₃ yield a third example, Y₂₀Br₃₆Ir₄ (Y₁₆Br₂₄Ir₄·4YBr₃, I4₁; a, Z = 4; a = 12.699(1) A?, c = 45.11-(1) A?). Here infinite zigzag chains of YBr_6/2 octahedra that share cis edges lie between and bridge to the Y₁₆Ir₄ clusters. All of these phases contain 60-electron, closed-shell macroclusters. Y₁₆Br₂₀Ru₄ and Y₂₀Br₃₆Ir₄ were found to exhibit temperature-independent (Van Vleck) paramagnetism with values typical of those found for other rare-earth-metal, zirconium, niobium, and tantalum cluster halides.

Full text of DOI:10.1021/ic960650x

7
056
Inorg. Chem. 1996, 35, 7056-7067
Oligomeric Rare-Earth-Metal Halide Clusters. Three Structures Built of (Y16Z4)Br36 Units
Z ) Ru, Ir)
(
Sharon J. Steinwand and John D. Corbett*
Department of Chemistry, Iowa State University, Ames, Iowa 50011
X
ReceiVed May 29, 1996
Suitable reactions in sealed Nb tubing at 850-950 °C gave good yields of a family of oligomeric cluster phases
that were characterized by single-crystal X-ray diffraction means. The basic Y16Z4 units (∼ 4h symmetry) can be
derived from 2+2 condensation of centered Y6Br12Z-type clusters or as tetracapped truncated tetrahedra Y16
that are centered by a large tetrahedral Z4. These are surrounded by 36 bromine atoms which bridge edges or cap
faces of the Y16Z4 nuclei and, in part, bridge to metal atoms in other clusters. The principal bonding appears to
be Y-Z and Y-Br, with weaker Y-Y ( dh ∼ 3.70 Å) and negligible Z-Z interactions. The phase Y16Br20Ru4
(P42/nnm, Z ) 2; a ) 11.662(1) Å, c ) 16.992 (2) Å) is isostructural with Y16I20Ru4 and with the new Sc16-
Br20Z4 (Z ) Fe, Os). Syntheses only in the presence of Ir and ABr-YBr3 fluxes (A ) K-Cs) produce Y16-
Br24Ir4 (Fddd, Z ) 8; a ) 11.718(3) Å, b ) 22.361(7) Å, c ) 44.702(2) Å), in which the electron-richer Ir
interstitials are compensated by four additional bromine atoms and altered bridging between macroclusters. Larger
amounts of YBr3 yield a third example, Y20Br36Ir4 (Y16Br24Ir4‚4YBr3, I41a, Z ) 4; a ) 12.699(1) Å, c ) 45.11-
(1) Å). Here infinite zigzag chains of YBr6/2 octahedra that share cis edges lie between and bridge to the Y16Ir4
clusters. All of these phases contain 60-electron, closed-shell macroclusters. Y16Br20Ru4 and Y20Br36Ir4 were
found to exhibit temperature-independent (Van Vleck) paramagnetism with values typical of those found for
other rare-earth-metal, zirconium, niobium, and tantalum cluster halides.
Introduction
an imagined tetrahedral (2+2) condensation of R6(Z) type
clusters into R16Z4 core units. The tetragonal structure reported
A large variety of zirconium (and hafnium) cluster halides
are known that contain only isolated Zr6X12Z units (X * F).
When the same systems are highly reduced, the double-metal-
layered phases ZrX (and HfX) are formed, but no compounds
with intermediate degrees of cluster condensation are known.
The contrasting compositions and structures found within
analogous ternary or quaternary rare-earth-metal (R) cluster
systems generally reflect the lower electron counts of these
7
for Y16I20Ru4 has not been seen during subsequent studies of
5
8
9
La-I, Pr-I, Gd-I, and Pr-Br systems, while only a single
example of a related cubic Gd20I28Mn4 has appeared, this
structure containing Gd16I20Mn4 units as well as a second small
8
tetrahedral cluster Gd4I8. The latter has been interpreted as a
4+
cationic Gd4I8 unit that electronically counteracts the effect
of encapsulation of four electron-poorer Mn interstitials in an
4-
otherwise similar tetrameric unit, i.e., Gd16I20Mn4 vs Y16I20-
1
-3
elements.
A necessary feature of clusters from metals of
Ru4.
either type is that these contain (are usually centered by) an
interstitial element Z, which may span later transition metals,
main-group non-metals from the second, third or, rarely, fourth
periods, hydrogen, and even diatomic C2 groups. But the rare-
earth element products are distinctive in that they afford many
electron-poorer examples in which cluster condensation via
shared metal edges affords not only quasi-infinite halogen-
sheathed chains or networks but also novel oligomeric inter-
mediates. Only two classes of the latter have been described.
One diverse group contains dimeric R10X16Z type units, as in
Gd6X16+n(C2)4 compounds (n ) 0, 1,2),3 CsEr10I18(C2)2,
Our recent explorations in Y-Br and Sc-Br systems in the
presence of late transition-metal elements as potential interstitials
have revealed not only several more R16X20Z4 compounds but
also other structures and compositions in which the same
tetrameric cluster units serve as “building blocks”. The present
article describes the new Y16Br20Z4 chemistry in some detail
since only a brief communication on Y16I20Ru4 has heretofore
appeared. In addition, two remarkable structural variations of
this theme are reported: for Y16Br24Ir4, for which the number
of bromide atoms available for intercluster bridging has
evidently increased in direct response to the increase in the
electron count of the interstitial element, and for Y20Br36Ir4, in
which unreduced YBr3 components are intergrown in an
expanded version of the second compound.
4
5
,6
Cs2R10I17Z2 (R ) La, Pr; Z ) Co, Ni), and La10I15Os2.
Only
two examples of a tetrameric oligomer are known, the result of
X
Abstract published in AdVance ACS Abstracts, November 1, 1996.
(
1) Corbett, J. D. In Modern PerspectiVes in Inorganic Crystal Chemistry;
Parth e´ , E., Ed.; NATO ASI Series C; Kluwer Academic Publishers:
Dordrecht, The Netherlands, 1992; p 27.
Experimental Section
Materials. The rare-earth metals utilized in the synthetic reactions
were Ames Laboratory products that had been vacuum distilled. The
largest impurity levels were 107-176 ppm atomic each of O and H.
Scandium metal was employed in the form of strips (∼3 × 5 mm) or
turnings. Yttrium was cold-rolled into 2-mil sheet which was cut into
small pieces (∼2 × 3 mm) immediately before use. Potential interstitial
(
2) Corbett, J. D. J. Alloys Compd. 1955, 229, 10.
(
3) Simon, A; Mattausch, Hj.; Miller, G. J.; Bauhofer, W.; Kremer, R. K.
In Handbook on the Physics and Chemistry of Rare Earths; Gschneidner,
K. A., Eyring, L., Eds.; Elsevier-North-Holland Publishers: Amster-
dam, 1991; Vol. 15, p 191.
(
(
(
4) Uhrlandt, S. C.; Artelt, H. M.; Meyer, G. Z. Anorg. Allg. Chem. 1994,
6
20, 1532.
5) Lulei, M.; Maggard, P. A.; Corbett, J. D. Angew. Chem., Int. Ed. Engl.
996, 33, 1704.
(7) Payne, M. W.; Ebihara, M.; Corbett, J. D. Angew. Chem., Int. Ed.
Engl. 1991, 30, 856.
(8) Ebihara, M.; Martin, J. D.; Corbett, J. D. Inorg. Chem. 1994, 33, 2079.
(9) Llusar, R.; Corbett, J. D. Inorg. Chem. 1994, 33, 849.
1
6) Lulei, M.; Martin, J. D.; Hoistad, L.; Corbett, J. D. J. Am. Chem.
Soc., in press.
S0020-1669(96)00650-7 CCC: $12.00 © 1996 American Chemical Society

Oligomeric Rare-Earth-Metal Halide Clusters
Inorganic Chemistry, Vol. 35, No. 24, 1996 7057
elements employed were powdered Ni, Ru, Rh, Pd, Os, Ir (Johnson-
Matthey, g99.9%), Re (Aldrich, 99.99%), Cr (AESAR, 99.5%), Fe
and Cu (reagent grade), chunks of Co (AESAR, 99.5%) and Mn
observed after quenching a reaction run at 1100 °C for 14 d,
demonstrating its relatively high stability. Observed product combina-
tions were sometimes in violation of the phase rule, indicating that
equilibrium had not been reached. Identification of all reaction products
was complicated by the number of phases found.
(
Johnson-Matthey, 99.99%), and Pt strips (government issue, reagent
grade).
The rare-earth-metal tribromides were prepared from the metals by
The analogous Sc16Br20
investigations of the corresponding Sc20-xBr28
Both occurred in more reduced (Sc-richer) systems, e.g., 20% Sc16
Br20Fe from compositions around Sc Br Fe, along with Sc-Fe binary
phases. The composition NaSc Br Fe at 840 °C for 24 d gave 60%
along with Sc and unreduced Na-Sc-Br compound(s) that
evidently served as a flux, but further heating of the product for 20 d
at 950 °C led to decomposition of the cluster phase. Likewise, a Sc
Z (Z ) Fe, Os) were encountered during
4
1
0
15
the ammonium bromide route, which proceeds via (NH
intermediates that are subsequently decomposed to form the RBr
which are then vacuum sublimed. Yttrium metal strips or dendrites
AESAR) were heated with a large excess of NH Br under Ar at 310
C until the evolution of H and NH YBr
ceased (∼3 d). The (NH
decomposed at 400 °C in vacuo to yield YBr (s), which was sublimed
was prepared in
4 3
) RBr
6
4
Z phases, as follows.
phases
-
3
4
3
3
(
°
4
4
4
)
4 3
6
Sc16Br20Fe
4
2
3
3
in a tube under dynamic vacuum at ∼800 °C. ScBr
3
3
-
1
3
a similar manner, with the corresponding formation, decomposition,
Br
amounts of an unknown, while a similar reaction at 950 °C for 2 w, or
of a NaSc Br Os composition at 840 °C or 950 °C, led to two different
unknowns and no Sc16Br20Os . The lattice parameters for Z ) Fe and
2 2 4 4
Os composition yielded ca. 50% Sc16Br20Os , Sc11Os , and small
and sublimation temperatures of 320, 550, and ∼700 °C, respectively.
Syntheses. Exploratory and directed synthetic reactions were carried
out on a scale of 150-200 mg within welded Nb tubes that were in
4
4
4
7
-9
Os determined from 22 and 34 indexed lines in the Guinier patterns
are a ) 10.996(1), 11.116(1) Å and c ) 16.021(4), 16.124(2) Å,
respectively.
turn jacketed by fused silica, as before.
gained if the interior of the loaded silica jacket was also cleaned with
an HF-H SO -HNO metal-cleaning solution and then rinsed just
before it was evacuated and sealed off. All transfers took place inside
a glovebox with e0.01 (vol) ppm of H O. Particular care was taken
to avoid the introduction of light impurities. Oxygen, usually from
O, was a persistent problem that inevitably manifested itself in the
Higher-purity products were
2
4
3
4 6
Y16Br24Ir . This was first observed after the composition CsY -
Br11Ir, had been heated to 850 °C, held there 4 d, and ramped (3 deg/
h) to 950 °C, where it was held for 2 w before cooling slowly. The
2
H
2
reaction product consisted of ∼50% Y16Br24Ir
black crystals grown in and around a mixture of YBr
(∼15%), and Cs Br (∼25%). A similar composition heated even
more slowly (15 d) to 950 °C followed by a 2 w reaction gave the
phases mentioned above plus Y20Br36Ir
4
as agglomerates of brittle
formation of the pervasive ROBr and upset the loaded stoichiometries.
This problem can be reduced by strong flaming of the walls of the
3
(∼10%), YOBr
Y
3 2
9
SiO
2 2
jacket under high vacuum just before sealing. Even so, H O
1
1
continues to evolve from the bulk silica and even to diffuse slowly
through the walls. Contamination from both sources increases with
time and temperature.
4
(below) in ∼20% yield. The
1
2
products formed appeared to depend on not only temperature but also
reaction time. The new phase was also synthesized in good yield in
analogous reactions with RbI or KI at 900 °C for 5 w. These products
Products were judged both visually and with the aid of Guinier X-ray
powder patterns, the yields of known phases being estimated (in terms
of equivalent scattering power) on the basis of calculated patterns and
their intensities. An internal standard of Si powder (NIST) added to
the ground products enabled lattice constants of known phases to be
refined from measured and indexed lines by least-squares means to a
9
also contained lines for Y
the presence of Rb Br
6
Br10Ir and Y
5
Ir
2
and weak lines evidencing
3
Y
2
9
or K
3
YBr
6
. (The formation of the ternary
alkali-metal yttrium(III) halide phases was generally favored over cluster
formation.) This oligomeric phase has been observed only in reactions
that contain alkali metals and therefore A
preferably with more YBr to compensate for this side product. There
is no evidence that any alkali metal is incorporated in the structure.
. Although the powder pattern of this compound was first
3 2 9 3 6
Y Br or A YBr as a flux,
4
3
few parts in ∼10 .
Y
16Br20Ru
4
and Analogues. The compound was first obtained from
, Y foil, and Ru powder loaded on stoichiometry
and heated at 980 °C for 24 d. This gave the new compound in 40%
yield as chunks and aggregates of black intergrown crystals, plus YBr
Y20Br36Ir
4
a reaction between YBr
3
observed several years ago, its quantification proved to be very
challenging owing to the difficulty of growing adequate single crystals.
3
,
1
3
These reaction mixtures ranged from Y
which gave either ∼20% each of nicely shaped black needles of Y
Br10Ir and aggregates of very small black Y20Br36Ir crystals or, with
larger Br:Y ratios, ∼40% of this phase with the balance as chunks of
YIr, YIr , Y Ir YOBr, and even small amounts of YBr . Reaction
mixtures in the range Y Br Ir to Y in
Br10Ir plus ∼15 mg of AlBr
each were heated very slowly and held at 750 °C, then 850 °C, and
3 2 2 2
Br Ir and Y Br Ir compositions,
YOBr (orange transparent plates), Y
another unidentified phase. Higher yields (60-85%) and better crystals
were obtained from reactions loaded as Y Br Ru, Y Br Ru, and Y
Br , which possibly
5
Ru
2
(irregular gray chunks), and
6
-
4
5
7
4
5
3
-
3
Ru, to all of which had been added ∼15 mg of AlBr
3
13
2
5
3
,
3
aided the formation of a gaseous reduced halide that transported metal
values. These systems were heated at 750 °C for 4 d, slowly ramped
to 850 °C and maintained there for 4 d, ramped again (3 deg/h) to 950
3
3
6
3
then 900-950 °C over a total of ∼24-39 d. The one loaded as Y
6
-
°C, and held there for 2 w, followed by a slow cooling to 700 °C before
Br10Ir gave nearly quantitative yield of that phase9 while those with
,16
turning off the furnace. (The slow heating was designed to lessen
nucleation rates, but there is no ensurance that this profile is essential.)
The products of particularly the bromine-richer runs included a small
amount of a compound that exhibited a powder pattern nearly identical
smaller Br:Y ratios gave moderate to high (g80%) yields of Y20Br36
Ir as well as small amounts (e25%) of an unknown phase (or phases).
Crystals of the target phase were still very small or poorly shaped.
Further heating of the products of a Y Br Ir reaction at 975 °C for 36
-
4
5
8
to that of Y20Br36Ir
theoretical yield from a reaction loaded as CsY
deficient) and heated under similar conditions. Other reaction products
included small amounts of YBr , YOBr, and, evidently, Cs Br as
the powder pattern contained the stronger lines calculated according
4
(below).
Y
16Br20Ru
4
was obtained in nearly
d followed by quenching gave instead ∼40% of an unidentified phase.
Temperature gradients or alkali-metal halide fluxes did not aid crystal
formation, the latter producing instead ternary alkali-metal yttrium-
6
Br10Ru (slightly Ru
3
3
Y
2
9
(
III) bromides and Y16Br24Ir
Ir composition heated at 975 °C for 36 d which gave ca. 50% of the
desired phase.
Structural Studies. Y16Br20Ru
4
. The best crystals came from a Y10Br13-
1
4
3
to the structure of Cs
Y
3 2
I
9
.
3 2 9
Cs Y Br (a ) 7.87 Å, c ) 19.68 Å)
was formed quantitatively in all reactions in which CsBr was present
and appeared to function as a useful flux. The oligomer was also
4
. Initial screening of crystals was
done with the aid of oscillation and Laue photographs. A blocklike
black chunk from a stoichiometric reaction was used for data collection
at room temperature on a Rigaku AFC6R diffractometer equipped with
Mo KR radiation. Twenty reflections from a random search indexed
to a primitive tetragonal cell, and Laue class 4/mmm was suggested by
the diffractometer software and confirmed by axial photos. A
hemisphere of data (h,(k,(l) was collected for 1° < 2θ < 50°, followed
by measurement of three ψ scans which indicated a relatively large
(
(
(
10) Meyer, G.; D o¨ tsch, S.; Staffel, T. J. Less-Common Met. 1987, 127,
155.
11) Holland, L. The Properties of Glass Surfaces; Chapman and Hall:
London, 1966; Chapter 4.
12) Schaeffer, H. A. In Concise Encyclopedia of Semiconducting Materials
and Related Technologies; Mahajan, S., Kimerling, L. C., Eds.;
Pergamon Press: Tarrytown, NY., 1992; p 457.
13) Villars, P.; Calvert. L. D. Pearson’s Handbook of Crystallographic
Data for Intermetallic Phases, 2nd ed.; American Society for Metals
International: Metals Park, OH, 1991; Vols. 3 and 4.
(
(15) Steinwand, S. J.; Corbett, J. D. Unpublished research.
(14) Guthrie, D. H.; Meyer, G.; Corbett, J. D. Inorg. Chem. 1981, 20, 1192.
(16) Payne, M. W.; Corbett, J. D. Inorg.Chem. 1990, 29, 2246.

7058 Inorganic Chemistry, Vol. 35, No. 24, 1996
Steinwand and Corbett
Table 1. Selected Crystal Data and Refinement Parameters for
Table 3. Positional and Isotropic-Equivalent Thermal Parameters
Y16Br20Ru
4
, Y20Br24Ir
4
, and Y20Br36Ir
4
for Y16Br24Ir
4
(Fddd)
emp formula
fw
space group, Z
Y4Br5Ru
865.21
P42/nnm
Y4Br6Ir
1027.27
Fddd
(No. 70), 32
Y5Br9Ir
1355.88
I41a
atoma
x
y
z
B
eq (Å2)
Ir
0.0238(2)
0.0073(4)
0.0086(4)
0.0423(4)
0.0092(4)
0.0032(4)
0.0028(4)
0.0245(4)
0.0156(5)
0.0071(5)
0.0177(5)
0.0728(1)
0.0677(3)
-0.0536(2)
-0.0656(2)
-0.0497(2)
-0.0809(2)
0.0592(2)
0.0581(2)
0.0635(3)
-0.0613(2)
-0.0694(3)
0.09899(5)
0.0372(1)
0.8389(1)
0.3444(1)
0.0952(1)
0.1579(1)
0.2273(1)
0.5930(1)
0.3433(2)
0.0307(2)
0.2823(2)
1.40(7)
2.1(2)
1.8(2)
1.8(2)
1.6(2)
2.1(2)
2.0(2)
2.1(2)
2.6(3)
2.4(3)
2.8(2)
Y1
Y2
Y3
Y4
Br1
Br2
Br3
Br4
Br5
Br6
(No. 134), 8
(No. 88), 16
lattice params
a
a (Å)
11.662(1)
11.718(3)
22.361(7)
44.702(2)
11 713(11)
4.66
12.6986(9)
b (Å)
c (Å)
16.997(2)
2311.6(6)
4.92
45.11(1)
7274(3)
4.95
427.11
0.043, 0.050
3
V (Å )
3
dcalc (g/cm )
µ(Mo KR) (cm-1) 383.2
409.95
0.057, 0.055
b
R, Rw
0.032, 0.032
a
Cell constants from 23, 27, and 26 lines in the Guinier patterns,
a
All type 32h positions; origin at 1h .
b
respectively; 22 °C, λ ) 1.540 56 Å. R.) ∑||F
o
| - |F
c
||/∑|F
o
|; R
w
)
2
2
1/2
-2
F
o
[∑w(|F | - |F
c
|) /∑w(F
o
) ] ; w ) σ
but also absences in 0kl (k + l * 2n), h0l (h + l * 2n), hk0 (h + k *
n), h00 (h * 4n), 0k0 (k * 4n), and 00l (l * 4n). Fourteen violations
2
Table 2. Positional and Isotropic-Equivalent Thermal Parameters
of the first three in this group were ignored at this point. The intensity
distribution strongly indicated the presence of a center of symmetry,
and all of these conditions are unique to the space group Fddd.
a
4 2
for Y16Br20Ru (P4 /nnm)
eqb (Å2)
atom Wyckoff posn
x
y
z
B
SHELXS-86 provided a solution of all eleven atoms. Their identities
were clearly defined by geometry, peak heights, distances, and bonding
environments, and refinement of first positional and then isotropic
Ru
Y1
Y2
Y3
Br1
Br2
Br3
Br4
8m
8m
8m
16n
16n
8m
8m
8l
0.1481(1) -x
0.1369(1) -x
0.1167(1) -x
0.31976(7) 0.87(3)
0.47892(8) 1.13(4)
0.15603(9) 1.03(4)
thermal parameters yielded R ) 0.076, R ) 0.092. The B values
w
0.1329(1) 0.0815(1) 0.32681(7) 1.00(5)
0.1245(1) 0.3481(1) 0.33899(6) 1.28(6)
were very small, negative for the Ir and one Y, until the secondary
extinction coefficient was refined. Anisotropic refinement led to non-
positive-definite ellipsoids for several atoms, and the ellipsoids of others
were large in the x-y plane. Space groups Fdd2 and F222 resulted in
major correlation problems between parameters that were equivalent
-0.1124(1) -x
-0.1222(1) -x
0.1196(1) x
0.3395(1)
1.48(5)
1.53(4)
1.24(4)
0.0212(1)
1
/
2
a
Origin at 2/m. b
2
B
eq ) (8π /3)∑
i
∑
j
U
ij
a
i
*a
j
i j
* ba ba .
1
in Fddd. An alternate monoclinic cell C2 /c resulted in similar R values
and did not eliminate the extreme thermal parameter problems.
Weissenberg photographs of the h0l, h1l, and h2l nets confirmed the
cell dimensions and appropriate absences, but the first also showed a
significant number of streaked spots in a net that did not correspond to
the aligned crystal. These were taken to be indicative of a satellite on
the data crystal. The h1l and h2l photographs were much cleaner and
consistent with the F-centered cell.
transmission coefficient range, 0.194-1.00. Intensity statistics strongly
indicated a centrosymmetric space group, and the data set exhibited
systematic absences for an n-glide perpendicular to the c axis, that is
hk0 for h + k ) 2n + 1, while 12 reflections violated a 0kl (k + l )
2
n) condition. Initial solutions were sought in P4/nmm and P4/n. Rav
was only slightly lower for 4/m than for 4/mmm (16.5% vs 17.1% for
17
I > 0). Direct methods (SHELXS-86 ) provided several solutions with
One source of the refinement problems was thought to be systematic
errors in the observed structure factors from inadequate absorption
corrections, particularly if the apparent satellite was a significant fraction
of the “crystal”. Therefore, the ABSN93 program was applied, followed
by data reduction in the CHES solution package.18 The main advantage
of the former is that it incorporates information regarding the size, shape,
and absorption coefficient of the crystal in a 2θ-dependent spherical
correction to the data, and this is then modified according to the ψ-scan
measurements. Refinement of positional and isotropic thermal param-
eters with this data set yielded R ) 0.084 and larger B values. A
difference-Fourier map computed after a problem-free anisotropic
reasonable bond lengths and coordinations, but the refinements
converged at 25%. The solution in the space group P4
disregarding the noted 0kl violations, yielded clearly defined Y16Ru
cluster units. The location of the halide atoms and the refinement were
straightforward and resulted in final R/R ) 3.22, 3.21%. The largest
positive peak in the final difference Fourier map was 1.62 e/Å , located
2
/nnm,
4
w
3
3
2
.27 Å from Br2, while the largest negative one was -2.09 e/Å . Only
four reflections had final ||F
o
| - |F || values greater than 5σ(F). No
c
serious problems with absorption were suggested by the anisotropic
thermal ellipsoid values; the greatest ratios of the principal axes were
1
.49 for Y1 and 1.64 for Br4, both for U11/U33. Some data collection
3
refinement revealed several peaks of e3.8 e/Å in a ring about the Ir
and refinement parameters are given in Table 1, and the positional and
isotropic-equivalent thermal parameters are listed in Table 2.
The powder pattern calculated from the structure model was in
excellent agreement with the observed patterns. Lattice parameters
based on 23 unique lines and a tetragonal cell resulted in dimensions
of a ) 11.662(1) Å and c ) 16.997(2) Å, values that were used in the
distance and angle calculations.
atom. Application of a DIFABS19 correction to the isotropic results
as recommended yielded R/R ) 6.3%/6.4% and a cleaner ∆F map.
w
Only 17 of 1182 unique reflections had ||F
o
| - |F || values greater
c
than 5σ(F). Many of these were of the 0kl type, and removal of two
that had particularly large differences, possibly because of the satellite
w
crystal, decreased R and R to 5.74% and 5.53%. The largest peak in
3
the final difference map was 2.24 e/Å , 1.75 Å from Br1, and the
thermal ellipsoids were very uniform except for small and reasonable
anisotropic effects for bromine atoms in unique bonding situations. The
powder pattern calculated from the structural model agreed very well
with the observed pattern. This contains three strong lines at low angles,
only about six others with I g 0.1Imax, and many weaker lines. Lattice
parameters utilized were calculated from 27 indexed lines measured
Y
16Br24Ir
4
. The correct solution of this structure took some extra
care and consideration. The Laue photograph of a somewhat large
(
0.16 × 0.20 × 0.28 mm) crystal cut from an aggregate suggested a
large unit cell, and the search procedure on the Rigaku diffractometer
yielded an F-centered orthorhombic cell with axes of about 11.72 Å,
2
2.39 Å, and 44.69 Å. Diversionary indications of a primitive cell
were found to arise from tails on the strong reflections coupled with
on a multiphasic Guinier pattern. The positional parameters for Y16
Br24Ir are listed in Table 3.
20Br36Ir . A preliminary study on the diffractometer gave a body-
centered tetragonal cell, a ) 12.69 Å, c ) 45.09 Å, that matched data
-
the large c axis. A quadrant of data ((h,k,l) were collected on the
-
1
4
F-centered cell to 2θ e 50° with a scan speed of 8° min because of
the relatively weak diffracting power of the crystal. The average of
three ψ scans was employed for absorption correction. The data set
after reduction exhibited not only absences appropriate to F-centering
Y
4
(
18) Karcher, B. Ph.D. Dissertation, Iowa State University, Ames, IA, 1981.
(17) Sheldrick, G. M. SHELXS-86, Programs for Structure Determination.
Jacobson, R. A. Private communication.
Universit a¨ t G o¨ ttingen, Germany, 1986.
(19) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.

Oligomeric Rare-Earth-Metal Halide Clusters
Inorganic Chemistry, Vol. 35, No. 24, 1996 7059
Table 4. Positional and Isotropic-Equivalent Thermal Parameters
a
4 1
for Y20Br36Ir (I4 a)
atom
x
y
z
B
eq (Å2)
Ir
Y1
Y2
Y3
Y4
Y5
Br1
Br2
Br3
Br4
Br5
Br6
Br7
Br8
Br9
0.1265(2)
0.1411(4)
0.1690(5)
0.2373(5)
0.1769(5)
0.1518(4)
0.2465(5)
0.1389(6)
0.1603(5)
0.1548(4)
0.2314(5)
0.1280(6)
0.1515(5)
0.1569(5)
0.1425(5)
0.2106(2)
0.2057(5)
0.1970(5)
0.0242(5)
0.2028(5)
0.2004(5)
0.0003(5)
0.1982(6)
0.1947(5)
0.2023(5)
0.0177(5)
0.1891(6)
0.1815(5)
0.1939(5)
0.2031(5)
0.15110(5)
0.2118(1)
0.0899(1)
0.1537(1)
0.3454(2)
0.7171(1)
0.2178(1)
0.9080(1)
0.2800(1)
0.0231(1)
0.5919(1)
0.4069(1)
0.6565(1)
0.7784(1)
0.5311(1)
0.6(1)
0.7(2)
0.7(3)
0.7(2)
0.7(3)
1.4(3)
1.6(3)
1.7(3)
1.7(3)
1.3(3)
1.0(3)
1.2(3)
1.7(3)
1.6(3)
1.6(3)
a
All atoms in 16f positions.
calculated by TREOR20 from 29 lines in the powder pattern. The 43
strong peaks located by the random search procedure on a better crystal
consistently gave a c/2 cell, but axial photographs showed that the larger
cell was correct. A quadrant of data ((h,k,l) were collected to 2θ e
-
1
5
0° without conditions and with a reduced scan speed of 8° min ,
and three ψ-scan measurements were secured and averaged. Although
about 7% of all possible violations of the body-centering condition
were observed, many in the 0kl and h0l nets, these “violations” all
differed by l ) 1 from intense allowed peaks. This problem originated
with streaks along c* or overlapping scan ranges because of the large
cell size. The data also exhibited systematic absences for most
reflections of the type hk0 (h, k * 2n) and 001 (l * 4n), and intensity
statistics indicated a centrosymmetric space group. The suggested space
Figure 1. (a) The Y16Ru
its derivation from (b) a truncated tetrahedron or from (c) a pairwise
condensation of four Y
Ru atoms are quarter-shaded and the vertices shared during condensation
are black in (c).
4
4
cluster ( 4h 2m symmetry) in Y16Br20Ru and
6
Ru octahedra. bc is vertical, ∼[110] view. The
were applied prior to data analysis. The data were analyzed with a
21
nonlinear least-squares-fitting program.
group I4
No trial models obtained from SHELXS-86 provided a reasonable
solution, or in space groups I4/m and I 4h either, but well-defined Y16Ir
units were found using I4 , and 20 other atoms were located with
1
/a was later confirmed by Weissenberg photographs.
Results and Discussion
4
Y16Br20Ru4. The structure of Y16Br20Ru4 consists of Y16-
Ru4 clustersssmall bits of a hypothetical intermetallic
compoundswithin a sphere of 36 bromine ligands that isolate
each unit from, and bridge to, neighboring Y Ru clusters. The
1
subsequent difference-Fourier calculations. However, the converged
isotropic refinement at R ) 6.1% showed strong correlations. The
presence of additional inversion centers and a glide plane relating the
16
4
positions showed that the symmetry was indeed I4
isotropic refinement converged at R ) 5.6%, R
1
/a, for which the
) 6.4%. Two
phase is isostructural with Y16I20Ru4, which has only been briefly
w
7
described, and is also found for Sc16Br20Z4 for Z ) Fe, Os
subsequent problems with non-positive-definite ellipsoids were solved
with a DIFABS absorption correction after which the isotropic and
(
Experimental Section). The tetragonal unit cell contains two
1
3
1
3
cluster units, one centered at ( /4, /4, /4) and the other at ( /4,
anisotropic refinements converged at R ) 4.26% and R ) 5.02%,
w
1
3
/
4, /4). The 20-atom metal cluster shown in Figure 1a consists
respectively. The relative sizes and shapes of the Br atom ellipsoids
were consistent with their varying functionalities in the structure. The
largest positive and negative peaks in the final difference Fourier
of a 16-atom polyhedron of Y atoms centered by a relatively
large tetrahedron of Ru atoms. The outer yttrium cluster can
be described as a truncated tetrahedron [4 Y1 + 8 Y3] on which
each of the four nearly hexagonal faces created by the truncation
is further capped by a Y2 atom, i.e., a tetracapped truncated
tetrahedron Y16, Figure 1b. The real cluster in this case has
4h 2m (D ) symmetry with the S axis vertical. The bond
3
3
calculation were 1.16 e/Å , 1.46 Å from Br7, and -1.49 e/Å . Only
one reflection had ||F
o
| - |F || > 5σ(F).
c
The powder pattern calculated from the structural model was in
excellent agreement with that observed, and lattice parameters were
calculated from 26 indexed lines. The pattern of one reaction product
in the Y-Br-Ru system also contained many strong low-angle lines
2
d
4
distances in Y16Br20Ru4 are listed and compared with those in
Y16I20Ru4 in Table 5; a comparable listing of angles is given in
the Supporting Information.
An alternative description, emphasizing the importance of
Y-Ru bonding within the structure, generates the metal cluster
from four Ru-centered Y6 octahedra via pairs of edge-sharing
biclusters that are further condensed at 90° with respect to each
other. This is depicted in Figure 1c. The yttrium atoms that
are shared in both steps of this last route are shaded in Figure
characteristic of the Y20Br36Ir
strong lines from the pattern of that multiphasic sample refined to give
the plausible a ) 12.701(3) Å, c ) 45.23(6) Å for Y20Br36Ru
The positional and isotropic-equivalent displacement parameters for
are listed in Table 4. The Supporting Information contains
more details than given in Table 1 plus the anisotropic displacement
4
structure type (see Syntheses), and nine
4
.
Y20Br36Ir
4
o c
parameters and angles for all three structures. These and the F /F
data are also available from J.D.C.
Magnetic Susceptibilities. Powdered samples (∼35 mg) were
enclosed in a He-filled and sealed silica apparatus in which the sample
was held between the faces of two silica rods. Data were collected on
Quantum Design MPMS SQUID magnetometer from 6 to 300 K with
field strength of 3 T. Diamagnetic sample holder and core corrections
1
a and solid in Figure 1c. The Y6Ru “octahedra” that
conceptually make up Y16Br20Ru4 (and Y16I20Ru4) undergo
substantial distortion in the process, although the Ru interstitials
in both still describe tetrahedra within experimental error. Each
Ru atom shifts toward the center of the polyhedron and the other
(
20) Werner, P. E. TREOR-V5. Department of Structure Chemistry,
Arrhenius Laboratory, University of Stockholm, Stockholm, Sweden,
(21) K o¨ ckerling, M. Unpublished research, Iowa State University, Ames,
IA, 1993.
1984.

7060 Inorganic Chemistry, Vol. 35, No. 24, 1996
Steinwand and Corbett
a,b
Table 5. Important Bond Distances (Å) in Y16Br20Ru
4
and Y16
I20Ru
4
Y
16Br20Ru
4
Y
16
I20Ru
4
Y16Br20Ru
4
16 4
Y I20Ru
Ru-Ru (×2)
Ru-Ru
3.357(2)
3.360(3)
2.712(2)
2.798(2)
2.831(2)
2.686(2)
2.757
2.712(2)
3.731(5)
3.685(2)
3.629(2)
3.672
3.113(2)
2.905(2)
3.019(2)
2.992
2.798(2)
2.831(2)
3.685(2)
4.398(4)
4.458(3)
3.715(2)
3.736(2)
3.712
3.572(3)
3.572(3)
2.714(3)
2.804(2)
2.837(3)
2.684(2)
2.760
2.714(3)
3.870(2)
3.769(2)
3.662(2)
3.746
3.467(3)
3.097(2)
3.223(2)
3.221
2.804(7)
2.837(3)
3.769(2)
4.284(2)
4.337(3)
3.794(2)
3.803(2)
3.789
Y3-Ru
Y3-Y1
Y3-Y2
Y3-Y2
Y3-Y3
Y3-Y3
dh Y3-Y
2.686(2)
3.629(2)
3.715(2)
3.736(2)
3.535(3)
3.779(3)
3.679
2.937(2)
2.953(2)
3.118(2)
2.890(3)
2.981(1)
2.976
3.134(2)
2.937(2)
2.953(2)
3.118(2)
3.113(2)
2.890(3)
2.905(2)
3.015(2)
3.019(2)
2.981(1)
2.684(2)
3.662(2)
3.794(2)
3.803(2)
3.581(3)
3.920(3)
3.752
3.123(2)
3.132(2)
3.417(2)
3.115(2)
3.218(2)
3.201
3.309(2)
3.123(2)
3.132(2)
3.417(2)
3.467(3)
3.115(2)
3.097(2)
3.199(3)
3.223(2)
3.218(2)
Ru-Y1
Ru-Y2
Ru-Y2 (×2)
Ru-Y3 (×2)
dh Ru-Y
i-a
i-a
a-i
i-a
i-i
Y1-Ru
Y1-Y1
Y1-Y2 (×2)
Y1-Y3 (×2)
dh Y1-Y
Y3-X1
Y3-X1
Y3-X1
Y3-X2
Y3-X4
a-i
Y1-X2
dh Y3-X
i-i
i-a
Y1-X3 (×2)
X1 -Y2
i-i
i-a
Y1-X4 (×2)
X1 -Y3
i-a
dh Y1-X
X1 -Y3
a-i
Y2-Ru (×2)
X1 -Y3
a-i
Y2-Ru
X2 -Y1
i-a
Y2-Y1 (×2)
Y2-Y2
X2 -Y3 (×2)
i-i
X3 -Y1 (×2)
i-i
Y2-Y2 (×2)
Y2-Y3 (×2)
Y2-Y3 (×2)
X3 -Y2
i-i
X4 -Y1 (×2)
i-i
X4 -Y3 (×2)
c
dh Y2-Y
X-X
>3.71
3.687
3.000
>3.94
3.761
3.219
i-a
c
Y2-X1 (×2)
3.134(2)
3.015(2)
3.094
3.309(2)
3.199(3)
3.272
dh Y-Y
i-i
Y2-X3
dh Y2-X
dh Y-X
a
Reference 6. b a and i designate outer (terminal) and inner (bridging or capping) connectivities of the halide to Y atoms. c Y2-Y2 distances not
included.
Ru atoms, so that trans angles Y1-Ru-Y2 and Y2-Ru-Y3
in the bromide become 165.5 and 164.2° (×2), respectively,
and the related cis angles are notably smaller than 90°. The
Y1 atoms follow the movements of the Ru atoms, maintaining
apical positions, while the Y2 atoms deviate farthest from ideal
octahedral geometry. The Y2-Y2 distances that make up the
shared edges of the imagined biclusters are more than 0.7 Å
greater than other Y-Y distances that define each “octahedron”
Three types of R16Z4 distortions in these compounds can be
systematized as (1) the effects of cluster condensation of R6Z
in all Y Z units, (2) the result of changes in halide size, and
1
6 4
(3) more complex effects based on both the relative sizes of
host R and interstitial Z and electronic factors. Details for the
last will follow the presentation of results on new R19X28Z4
15
compounds, but the first two are easily perceived in Y16Br20-
Ru4 and Y16I20Ru4, which lie at one extreme in a series of eight
oligomer structures. Although ideal octahedra fit together
perfectly to form a tetramer, Figure 1c, this would leave the
apical Y1 with only four Y neighbors, the waist Y3 with five,
and the fused Y2 vertices with nine. Such a disparity in degrees
of metal bonding is uncommon in rare-earth-metal halide cluster
chemistry. However, the observed shift of the apical Y1 atom
pairs toward each other and toward the center of the oligomer
can be imagined to give an additional Y1-Y1 bond without
loss, while the Ru atoms follow and move toward each other
in order to maintain suitable Y-Ru distances. Short Ru-Y2
distances that would otherwise develop from this shift are
avoided by motion of the Y2 atoms outward, with virtual loss
of the shared equatorial Y2-Y2 bond between atoms that
already have an unusually high number of Y neighbors. This
fictitious scenario thus allows Y-Y interactions to be optimized
without sacrificing what is probably the dominant Y-Ru
bonding. Interestingly, the largest distortions observed upon
substitution of Br by I are the marked (0.14 Å) increases in the
relevant Y1-Y1 and Y3-Y3 distances that appear upon
pairwise bicluster condensation coupled with ∼0.12 Å decreases
in the two types of Y2-Y2 distances, meaning the cluster
“breathes” less. The transition from bromide to iodide is
accompanied by 0.08 and 0.21 Å increases in average Y-Y
and Ru-Ru distances. In many octahedral cluster halides, the
replacement of Br (or Cl) by I causes an increase in cluster
(>0.50 Å greater in the iodide), while a second set of slightly
longer Y2-Y2 separations constitute the edges shared between
bioctahedra. Neither of these longer Y2-Y2 distance types is
marked in Figure 1a or considered in distance averages.
Bond distances within the clusters are comparable to those
found in other reduced rare-earth-metal halide compounds. The
Y-Ru distances in Y16Br20Ru4 range from 2.686(2) to 2.831-
(2) Å (to Y2), with an average of 2.757 Å, substantially identical
to those in the iodide cluster. These distances are well within
the range of those observed in other Ru-centered Y octahedra,
as in Y6I10Ru22 and Y3I3Ru, and are shorter than the sum of
23
2
4
Pauling’s single-bond metallic radii, 2.862 Å. The Y-Ru
interactions appear to be the fixed and strong features of the
bonding. Distances between neighboring Y atoms in the
bromide range from 3.535(3) to 3.779(3) Å with dh Y-Y ) 3.687
Å, which corresponds to a Pauling bond order of 0.17. The
latter dimensions appear to be primarily fixed by the size of
the interstitial. Each Y1 and Y3 is bonded to five other Y atoms
in the cluster, while Y2 is bonded to, and nearly coplanar with,
six other Y atoms, which results in a slight increase in the
average Y2-Y distance. The Ru-Ru separations of 3.36 Å
correspond to a Pauling bond order of 0.04 and imply that Ru-
Ru bonding is negligible. Thus, Z4 tetrahedra in some subse-
quent figures are outlined solely to provide geometric reference.
(
(
22) Hughbanks, T.; Corbett. J. D. Inorg. Chem. 1989, 28, 631.
23) Payne, M. W.; Dorhout, P. K.; Kim, S.-J.; Hughbanks, T. R.; Corbett,
J. D. Inorg. Chem. 1992, 31, 1389.
1
size as a result of increased matrix or steric effects because of
increased packing limitations (X‚‚‚X repulsions) in the infinite
(24) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY., 1960; p 403.
crystalline array.

Oligomeric Rare-Earth-Metal Halide Clusters
Inorganic Chemistry, Vol. 35, No. 24, 1996 7061
Figure 2. Two bonding modes for bromine atoms (open ellipsoids)
in Y16Br20Ru : (a) Br3 atoms capping Y1-Y1-Y2 triangular faces
4
and (b) Br1 atoms capping Y2-Y3-Y3 triangular faces and bonding
exo to Y3 in an adjacent cluster.
On the basis of prior experience with isolated clusters,1,2 the
halides in the Y16X20Ru4 (and other) phases would be expected
to bond to free metal orbitals on the surfaces of the clusters by
bridging metal edges as well as bonding exo at Y vertices in
other oligomers, thus insulating these units from each other and
preventing further condensation. However, these oligomers
demonstrate a new halide bonding mode for clusters of the early
metals, the capping of triangular Y faces by Br3 and Br1,
presumably because of the reduced proportion of halogen
available. A µ3-halide bonding mode on a cluster of group 3
Figure 3. (a) [110] view showing the bonding modes of Br2 (crossed)
i-a
i-i
4
as Br and Br4 (shaded) atoms as Br in Y16Br20Ru (Y open, 70%
ellipsoids). (b) The Y16Ru cluster with its coordination environment
4
of 36 Br atoms, showing Br as open, Y as shaded, and Ru as cross-
hatched ellipsoids. Heavy lines emphasize the strong octahedral-like
bonding about each Ru.
1
-3
or 4 elements has hitherto been realized mainly in Gd2Cl3
and Y4Br4Os,2 in which infinite chains are generated when
octahedra share metal edges and square antiprismatic clusters
share square faces, respectively. As shown in Figure 2a, three-
bonded Br3 atoms cap four Y1-Y2-Y2 faces on each
oligomer, while Br1 atoms cap eight of twelve Y2-Y3-Y3
triangular faces around the waist (those with the longer
intracluster Y3-Y3 edges), Figure 2b. The Br1 atoms are also
bonded exo to Y3 atoms of neighboring clusters and so are
5
i-a
a-i
designated as Br and Br connections, noting that the “inner”
4
Figure 4. Cubic-close-packed description of a Y16Ru cluster and
nearby bromine atoms viewed parallel to the layers.
i-i
functions are µ3, not µ2. Figure 3a illustrates how Br4 atoms
(
shaded) simultaneously bridge Y1-Y3 edges on two oligomers,
i-a
a-i
16 4
environment of 36 Br atoms about each Y Z is found in the
following two structures as well.
while Br2
and the complementary Br2
atoms (crossed
i-i
ellipsoids) symmetrically located about pairs of Br4 (and an
inversion center) bridge Y3-Y3 edges of one oligomer while
occupying the exo site at Y1 cluster apices in an adjacent
oligomer.
Figure 3b shows the 36 Br atoms that surround each
macrocluster, the Y-Ru and Y-Br connections being drawn
heavier to emphasize the octahedral network about each Y atom
and what are probably the stronger bonding interactions. The
Y2 atoms, which already have 6 Y and 3 Ru neighbors, lack a
direct exo bond to another bromine but rather have three
neighboring µ3-Br1 atoms (Figure 2b). The exo Y-Br bonds
A geometric close-packed arrangement of halide (and inter-
stitial) atoms is a regular feature of cluster halide structural
chemistry and can also be found in all three structures described
herein, normal to the four pseudo-3-fold axes that pass through
each Y2 and the Z4 tetrahedron, [2 2h 3] in the present case.
Figure 4 depicts how Y atoms fill the pseudooctahedral holes
between ccp Br + Ru layers that neighbor groups of Ru atoms,
resulting in Y coordination by six heteroatoms (Figure 3b). The
Y layers are offset slightly toward the Ru positions which
themselves are shifted out of the Br layer while some Br atoms
are displaced within the layers.
1
are longer, in accordance with general observations that bonding
of the interstitial atom to each metal vertex always appears to
be “winning” over that to the opposing exo halogen. The same
Overall, each oligomer is connected to eight others through
i-a
a-i
two types of bromines. The Br1 and Br1 bridges pictured
in Figure 5a join translationally related oligomers within the
1
(25) Dorhout, P. K.; Corbett, J. D. J. Am. Chem. Soc. 1992, 114, 1697.
a-b plane into a square network at z ) /4, with a second layer

7062 Inorganic Chemistry, Vol. 35, No. 24, 1996
Steinwand and Corbett
Figure 5. Intercluster bonding in Y16Br20Ru
4
(a) via Br1 atoms to form
i-a
i-i
a square network within the a-b plane and (b) via Br2 and Br4
(
dotted) atoms in a pseudotetrahedral arrangement of clusters along bc .
bb is horizontal in both views.
Figure 6. ∼[ 1h 00] view of the unit cell of orthorhombic Y16Br24Ir
4
illustrating the face-centered nature of the cluster packing. bb is
horizontal; bc is vertical. All Br and Ir atoms are omitted for clarity.
3
at z ) /4 directly above and below the holes of the first layer
(
at (a/2, (b/2) to give an ..AB.. stacking pattern. Each cluster
i-i
i-a
a-i
is bridged via Br4 , Br2 , and Br2 to four neighbors in
the adjacent layers to form a pseudotetrahedral array, as shown
in Figure 5b, the clusters being rotated by 90° around bc to bring
the Y3-Y1-Y3 triangles face to face (Figure 3a). The shortest
intercluster Y-Y distances occur in this direction between Y1
atoms, 4.57 Å. Four other clusters not connected to the central
one form a second pseudotetrahedron, oriented such that Y2-
centered hexagons are face to face. Accordingly, each cluster
sits in an approximately cuboctahedral environment of eight
near-neighbor and four more distant clusters.
Y16Br24Ir4. Formation of a new example of a structure built
of R16Z4 clusters is driven by a simple change: the four
additional electrons derived from a change of interstitial from
Ru to Ir are matched by four additional bromides so that the
oligomers remain isoelectronic. The new structure maintains
an environment around each cluster very similar to that in Y16-
Br20Ru4, but the Br atoms are shared in a manner that
accommodates four more per cluster.
Figure 7. [110] view of a Y16Ir
four types of Y atoms indicated bc vertical; 222 (D
Compare Figure 1a.
4
cluster unit in Y16Br24Ir
4
with the
2
) symmetry).
and Y1-Y4 bond lengths differ by 0.10(1) Å, and the two Y2-
Y1 distances, by 0.06(1) Å. The three independent Ir-Ir
distances range from 3.294(4) to 3.328(4) Å.
Most average bond distances within the Y16Ir4 clusters are
slightly larger than those found above but still smaller than those
observed in Y16I20Ru4. The unique six-bonded Y2 atoms again
have larger Y2-Y and Y2-Ir separations, and the Y2-Y2
(non-bonding) distances are nearly 0.1 Å larger in the Y16Ir4
cluster than in Y16Ru4. The average Y-Ir distance, 2.787 Å,
is 0.030 Å larger than the previous average Y-Ru distance,
fairly consistent with Pauling’s single-bond radii,24 which
increase ∼0.02 Å from Ru to Ir; the average Ir-Ir bond order
is still only 0.05. The placement of the Ir atoms is evidently
dictated largely by optimization of their bonding to Y. The
Y6Ir “octahedra” that make up the oligomeric Y16Ir4 are more
irregular than previously, with the Ir atoms displaced more
toward the center of the oligomer so that the trans angles across
each “octahedron” (Y2-Ir-Y) are 1.6-2.4° less than above.
As in all oligomers, each Ir atom is distinctly closer to the metal
The face-centered orthorhombic unit cell of Y16Br24Ir4 (Fddd)
shown in Figure 6 contains eight Y16Ir4 units. These are
1
1
1
7
centered around sites of 222 (D2) symmetry at ( /8, /8, /8), ( /
8
7
7
, /8, /8) (and other symmetry-related points) vs 4h 2m for the
macrocluster in Y16Br20Ru4. The units are internally quite
similar to those described for Y16Br20Ru4 with only modest
distortions. Each cluster now contains four crystallographically
distinct Y atoms, as seen in Figure 7 with different shadings
for each type. The truncated tetrahedron is formed by Y1, Y3,
and Y4 atoms, while the pseudohexagonal faces are again
capped by Y2 atoms. Perpendicular 2-fold axes parallel to ba ,
bb , and bc axes bisect pairs of Y3-Y3, Y4-Y4, and Y1-Y1
edges, respectively. Distances within the structure are given
in Table 6, while the corresponding angles are in the Supporting
Information. The loss of mirror symmetry is evident; Y1-Y3

Oligomeric Rare-Earth-Metal Halide Clusters
(Å)
Inorganic Chemistry, Vol. 35, No. 24, 1996 7063
Table 6. Closer Atom Separations in Y16Br24Ir
4
Ir-Ir
3.294(4)
3.322(4)
3.328(4)
2.771(7)
2.825(6)
2.821(6)
2.833(7)
2.724(5)
2.750(6)
2.787
3.76(1)
3.757(7)
3.697(8)
3.590(7)
3.689(8)
3.69
2.771(7)
2.828(8)
2.891(7)
2.901(9)
3.04(1)
2.817(8)
2.90
Y2-Y1
3.757(7)
3.697(8)
4.49(1)
4.47(1)
4.54(1)
3.749(7)
3.793(8)
3.735(7)
3.749(8)
3.747
2.825(6)
2.821(6)
2.833(7)
3.013(8)
2.966(9)
3.122(7)
3.03
Y3-Ir
2.724(5)
3.144(7)
2.932(7)
2.909(8)
2.903(9)
2.79(1)
2.93
3.689(8)
3.735(7)
3.749(8)
3.620(7)
3.81(1)
3.71
2.750(6)
2.890(9)
2.874(7)
2.873(8)
3.075(8)
2.90(1)
2.92
Br1-Y2a
Br1-Y4
Br1-Y4
Br2-Y1
Br2-Y1
3.013(8)
2.890(9)
2.874(7)
2.828(8)
2.891(7)
2.966(9)
3.122(7)
3.144(7)
2.932(7)
2.909(8)
2.903(9)
2.873(8)
3.075(8)
2.901(9)
3.04(1)
a
Ir-Ir
Y2-Y1
Y2-Y2
Y2-Y2
Y2-Y2
Y2-Y3
Y2-Y3
Y2-Y4
Y2-Y4
Y3-Br3
Y3-Br3
Y3-Br3
Y3-Br4
Y3-Br6
dh Y3-Br
b
b
b
Ir-Ir
Ir-Y1
Ir-Y2
Ir-Y2
Ir-Y2
Ir-Y3
Ir-Y4
dh Ir-Y
a
Br2-Y2
a
Br3-Y2
Br3-Y3
a
Y4-Y1
Y4-Y2
Y4-Y2
Y4-Y3
Y4-Y4
dh Y4-Y
Br3-Y3
Br3-Y3
Br4-Y3
Br4-Y4
b
dh Y2-Y
Y1-Y1
Y1-Y2
Y1-Y2
Y1-Y3
Y1-Y4
dh Y1-Y
Y1-Ir
Y1-Br2
Y1-Br2
Y1-Br5
Y1-Br5
Y1-Br6
dh Y1-Br
Y2-Ir
Y2-Ir
Y2-Ir
a
Br4-Y4
a
a
a
Y2-Br1
Y2-Br2
Y2-Br3
dh Y2-Br
Y3-Y1
Y3-Y2
Y3-Y2
Y3-Y3
Y3-Y4
dh Y3-Y
Y4-Ir
Br5-Y1
Br5-Y1
a
Y4-Br1
Y4-Br1
Y4-Br4
Y4-Br4
Y4-Br5
dh Y4-Br
Br5-Y4
Br6-Y1
Br6-Y3
Br1-Br1
Br-Br
2.90(1)
2.817(8)
2.79(1)
3.59(1)
g3.70(1)
a
3.590(7)
3.749(7)
3.793(8)
3.81(1)
3.620(7)
3.70
a
dh Y-B rb
dh Y-Y
2.937
3.721
a
Corresponds to a Br atom trans to Ru. b Nonbonding distances not included in averaging.
Figure 8. [110] view of three bonding modes of bromine in Y16Br24
Ir
respectively) on only one cluster, while Br3 caps Y2-Y3-Y3 faces
and bonds exo to Y3 in another.
-
4
. Br1 and Br2 cap triangular faces (Y2-Y4-Y4 and Y2-Y1-Y1,
atoms in the Y1-Y3-Y4 truncated faces than to the three Y2
atoms that make up the large opposed face of the surrounding
4
Figure 9. View of how the Br4 and Br5 atoms in Y16Br24I bridge the
Y3-Y4 and Y1-Y4 edges and bond exo to Y4 and Y1 in adjacent
clusters, respectively, while Br6 bridges only Y1-Y3 edges of the
cluster.
“
octahedron”.
Six crystallographically different Br atoms adopt four bonding
modes, and their altered functionalities make up the major
differences from the previous structure. As shown in Figure 8,
four each of Br1, Br2, and Br3 atoms cap triangular faces, as
previously; however, the Br1 and Br2 atoms are bonded to only
one cluster, while Br3 atoms are simultaneously bonded exo to
Y3 atoms in neighboring clusters in a manner identical to that
adopted by Br1 in Y16Br20Ru4 (Figure 2b). Figure 9 illustrates
how the Br4, Br5, and Br6 atoms edge-bridge all of the
triangular faces generated by truncation of the tetrahedron (Y1-
Y3-Y4). The Br4 and Br5 atoms are additionally bonded exo
to Y4 and Y1 atoms, respectively, in adjacent clusters, similar
to the behavior of Br2 in Y16Br24Ru4. Finally, four Br6 atoms
bridge Y1-Y3 edges on only one cluster. The average Y-Br
distance is 2.937 Å, 0.063 Å less than that in Y16Br20Ru4 yet
still larger than the sum of crystal radii, 2.86 Å (for six-
-
26
coordinate Br ). The distance contraction is consistent with
the increased number of Br atoms per cluster and the ensuing
reduction in their average coordination number. The exo Y-Br
distances trans to Y-Ru bonds are again significantly longer
than others, >2.96 Å.
Every Y16Ir4 cluster is connected to ten neighbors via Br
bridges rather than the eight previously. Six of these lie in a-b
Figure 10. [00 1h ] view of a pseudo-hcp cluster network in Y16Br24Ir
4
1
(
z ) /
8
) with interbridging by Br3 and Br4 (compare Figures 8 and
9
). ba is horizontal.
planes to form a pseudo close-packed layer, Figure 10. These
(26) Shannon, R. P. Acta Crystallogr. 1976, A32, 751.
layers are in turn connected along bc by four pair of Br5 bridges

7064 Inorganic Chemistry, Vol. 35, No. 24, 1996
Steinwand and Corbett
Figure 11. [ 1h 00] view of intercluster bridging connections in Y16Br24
4
-
i-a
Ir along bc (vertical) via Br5 atoms.
about each cluster, Figure 11, and these connections generate
the shortest intercluster distances, 4.51 Å for Y1-Y1. This
quasi-tetrahedral arrangement is similar to that in Y16Br20Ru4,
Figure 5b, but the rotation angles between cluster pairs now
deviate from 90°, and the reduced and more open bridging along
bc results in a large expansion of the cell in that direction. The
Figure 12. [ 1h 00] view of the tetragonal unit cell in Y Br Ir ,
2
0
36
4
illustrating the body-centered nature of the cluster packing. The structure
1
3
5
7
is built of Y Ir clusters and YBrch4/2Brcl chains. For clarity, only Br
layers in Figure 10 stack along bc at z ) /8, /8, /8, /8 with the
16
4
2/2
1
1
atoms (open ellipsoids) in the latter chains are pictured. bb is horizontal;
bc is vertical.
individual clusters actually related by diamond glides at /4, /4,
z, etc. As can be qualitatively perceived in Figure 6, the second
1
1
1
cluster layer is in effect shifted by - /4, /4, /4 with the clusters
rotated by roughly 90° with respect to those in the first layer.
1
1
1
The third layer is translated by /4, /4, /4 from the second, with
the clusters oriented as in the first layer, and so forth.
The two Y16Z4 examples also exhibit dimensional relation-
ships because of related cluster packing and intercluster bridging.
The strongest relationship is within the a-b planes, where the
cluster orientation and intercluster Br bonding modes along ba
and bb in Y16Br20Ru4, Figure 5a, and ba in Y16Br24Ir4, Figure 10,
are identical with a common cell length of ∼11.7 Å. The
pseudohexagonal (close-packed) a-b plane for Ir can be
obtained from the Ru network by displacement of every other
(
(
identical) row of clusters in the tetragonal Y16I20Ru4 by b/2
or a/2), a change that roughly doubles the repeat along bb to
∼
22.4 Å. This shift means the formerly interlayer-bridging Br2
Figure 13. The Y Ir cluster ( 4h symmetry) in Y Br Ir with four
16
4
20
36
4
atoms (Figure 3a) now bridge clusters within one layer, while
the tricapping Br1 atoms (Figure 2b) no longer participate in
intercluster bonding along bb . The c-axis length of Y16Br24Ir4
is close to twice its b repeat because of the similarities in the
bridging modes of Br5 and Br4, respectively. The relationship
with c in Y16Br20Ru4 is more complex because of the different
bonding modes.
crystallographically distinct Y atoms indicated. ba is horizontal; bc is
vertical.
cl
within the chains and Br , between chains and the Y16Ir4
clusters, while all other anions have been omitted from this view.
1
1
The familiar Y16Ir4 clusters centered around (0, /4, /8), (1/2,
1
3
/4, /8), etc. now possess 4h (S4) symmetry along bc and are made
up of four crystallographically distinct Y atoms, as marked in
Figure 13. The bb axis lies nearly normal to the figure and bisects
the two Y2-Y4 edges near the center.
Y20Br36Ir4. The continuation of this series to an even
bromide-richer phase contains a very similar Y16Ir4 core, but
the sharing of bromine between oligomers is further reduced
by the novel incorporation of a YBr3 component as infinite-
chain units. The chains evidently contain only yttrium(III), and
the compound can be expressed as Y16Br24Ir4‚4YBr3. The body-
centered tetragonal unit cell of Y20Br36Ir4 depicted in Figure
The lack of mirror symmetry within the cluster is most
pronounced in the Y1-Y3-Y4 faces generated by truncation
of the imagined Y tetrahedron (Figure 1b). The Y1-Y3
distance is nearly 0.05 Å longer than Y1-Y4, Table 7, while
the Y2-Y distances in the hexagonal faces are still essentially
equivalent by mirror symmetry. The same is true of the Ir4
core, where the Ir-Ir edges that parallel the Y1-Y1 edges are
0.018(4) Å longer than the rest, in line with a general but slight
1
2 contains four oligomeric units along with the infinite zigzag
III ch
cl
chains of Y Br 4/2Br 2/2 octahedra sharing cis edges that run
ch
alternately along ba and bb . The designated Br atoms bridge

Oligomeric Rare-Earth-Metal Halide Clusters
(Å)
Inorganic Chemistry, Vol. 35, No. 24, 1996 7065
Table 7. Important Bond Distances in Y20Br36Ir
4
Ir-Ir (×2)
3.348(4) Y2-Y3 3.767(8) Y4-Y1
3.651(9)
3.737(8)
3.771(9)
3.634(8)
3.780(7)
3.715
Ir-Ir
3.366(5) Y2-Y4 3.737(8) Y4-Y2
2.743(6) Y2-Y4 3.771(9) Y4-Y2
Ir-Y1
Ir-Y2
Ir-Y2
Ir-Y2
Ir-Y3
Ir-Y4
dh Ir-Y
2.817(6) dh Y2-Y
2.836(8) Y2-Ir
2.841(7) Y2-Ir
2.756(7) Y2-Ir
3.748
Y4-Y3
2.743(6) Y4-Y3
2.817(6) dh Y4-Y
2.836(8) Y4-Ir
2.732(8)
a
a
2.732(8) Y2-Br4 3.022(8) Y4-Br2 3.133(9)
a
2.788
3.75(1) Y2-Br6 2.96(1) Y4-Br3 2.96(1)
3.00 Y4-Br5 2.90(1)
Y2-Br5 3.01(1) Y4-Br2 2.85(1)
a
Y1-Y1
Y1-Y2 (×2) 3.745(8) dh Y2-Br
Y1-Y3
Y1-Y4
dh Y1-Y
3.696(7) Y3-Y1 3.696(7) Y4-Br6 2.85(1)
3.651(9) Y3-Y2 3.721(8) dh Y4-Br
2.94
4.05(1)
4.08(1)
b
b
3.714
Y3-Y2 3.767(8) Y5-Y5
Y1-Ir
2.743(6) Y3-Y4 3.634(8) Y5-Y5
Y1-Br1
Y1-Br3
Y1-Br3
Y1-Br4
Y1-Br4
dh Y1-Br
2.946(9) Y3-Y4 3.780(7) Y5-Br1 2.86(1)
a
3.093(8) dh Y3-Y
2.85(1) Y3-Ir
3.720
Y5-Br7 2.74(1)
Figure 15. Bonding of Br2 and Br3 atoms in Y Br Ir which bridge
20
36
4
2.756(7) Y5-Br8 2.770(9)
the Y3-Y4 and Y1-Y4 edges, respectively, while bonding exo to Y4
vertices in adjacent clusters (Y labels as in Figure 13).
2.874(8) Y3-Br1 2.908(9) Y5-Br8 2.78(1)
2.861(9) Y3-Br2 2.90(1) Y5-Br9 2.786(9)
2.925
Y3-Br5 2.867(9) Y5-Br9 2.781(9)
Y2-Y1 (×2) 3.745(8) Y3-Br6 2.91(1) dh Y5-Br
2.79
3.726
b
a
Y2-Y2 (×3) 4.50(1) Y3-Br7 2.972(9) dh Y-Y
b
c
Y2-Y3
3.721(8) dh Y3-Br
2.911
Br6-Br6 3.60(1)
a
b
Br atom positioned trans to an Ir atom. Longer distances not
c
included in averaging. All other Br-Br distances are g3.73 Å.
4
Figure 14. Bonding modes of Br4, Br5, and Br6 in Y20Br36Ir which
cap triangular faces (Y1-Y2-Y1, Y2-Y3-Y4, and Y2′-Y3-Y4,
respectively) within the hexagon about Y2 on only one cluster. ba is
horizontal; bc is vertical.
compression of the cluster along bc that is reflected in ∼0.04 Å
differences in particular Y-Y distances. Despite these minor
differences, the overall geometry of the clusters in Y20Br36Ir4
is very similar to that in Y16Br24Ir4. The average Y-Y
intracluster distance of 3.726 Å (Pauling bond order ) 0.15) is
nearly identical to that in Y16Br24Ir4 (3.721 Å), and the same is
true for the average Y-Ir distances. The Ir-Ir distances are
slightly longer (by ∼0.04 Å) than previously, in parallel with
the small expansion in Y-Y separations. The trans Y-Ir-Y
angles across the imagined octahedral components are inter-
mediate to those cited previously.
Figure 16. (a) 0 1h 0 view of the bonding between the clusters and the
ch
cl
YBr 4/2Br 2/2 chains in Y20Br36Ir . Br1 bridges the Y1-Y3 cluster edges
4
while bonding to the isolated Y5, and Br7 is exo to both a Y3 vertex
and the Y5 atom. Pairs of Br8 and Br9 bond exclusively within the
chain, bridging cis edges of the Y5-centered octahedron ( ba is horizontal).
ch
cl
(
b) The cluster-chain interconnectivity along the zigzag YBr 4/2Br 2/2
chains. Clusters are alternately connected on both sides of and above
and below the chain.
Nine types of Br atoms exhibit five basic bonding modes.
Those of µ3-Br4, -Br5, and -Br6 are defined in Figure 14, each
capping four Y3 faces on the cluster. Appropriate to the increase
in bromine content, none of the eight Br5 and Br6 atoms per
cluster that cap two-thirds of the Y2-Y3-Y4 faces around the
waist of the cluster now bridge to another cluster, whereas half
of these do in Y16Br24Ir4 and all do in Y16Br20Ru4. All means
of direct intercluster bridging are shown in Figure 15; four Br2
Br9 (keyed by shading) generate and connect the YBr3 chains
to the clusters. Four Br1 atoms that bridge Y1-Y3 edges on
the clusters are also exo to the Y5 atoms that center the
ch
cl
a-a
YBr 4/2Br 2/2 chains, while four Br7 atoms bridge Br
between Y3 on each oligomer and Y5. The unbranched zigzag
chains themselves, Figure 16b, can be viewed as Y2Br10
“dimers” intrabridged by Br9 pairs and connected at both ends
by pairs of Br8 bridges on cis edges. (A variation of this chain
i-a
atoms as Br bridge Y3-Y4 edges while also bonding exo to
Y4 atoms in four neighboring clusters so as to form nets normal
2
7
1
to bc , the same functionalities as previously (Figure 10), while
style occurs in ZrCl4. ) These novel chains lie at z ∼ 0, /4,
/2, and /4 between the cluster layers (below); compare Figures
12 and 16b. Four chains bridge to each oligomer, two below
i-a
1
3
Br3 atoms bridge each cluster to four others in the c direction
( 4h symmetry). Figure 16a illustrates how Br1, Br7, Br8, and

7066 Inorganic Chemistry, Vol. 35, No. 24, 1996
Steinwand and Corbett
Figure 18. Molar magnetic susceptibilities as a function of temperature
Figure 17. [00 1h ] view of the square net Y16Ir
4
clusters in Y20Br36Ir
). ba is horizontal.
4
4 4
(K) at 3 T for Y16Br20Ru (solid rectangles) and Y20Br36Ir (open
1
as interbridged by Br2 atoms (z ) /
8
rectangles). The data for the latter prior to application of the diamagnetic
core correction are also shown as crosses.
and two above. The Y5-Y5 distances along the chains, 4.05
Å within and 4.08 Å between dimers, are insignificant as far as
bonding.
phase powder pattern, was apparently Y20Br36Ru4, which would
contain 56 electrons per oligomer. Isostructural oligomeric
phases were not seen in comparable explorations with intersti-
tials Cr, Mn, Re, and Pt, while Fe in a metal-richer system gave
Each Y16 cluster is also directly bridged to eight neighboring
clusters. Figure 17 depicts the square cluster network generated
1
by Br2 bridges (Figure 15) normal to bc at z ) /8. Other like
28
something resembling Y2Br2Fe ( )ˆ Gd2Br2C ) and Ni, possibly
3
5
7
layers at z ) /8, /8, and /8 are related by alternating a- and
b-glide planes. The result in Figure 17 can also be generated
from the more compact net in Y16Br20Ru4 (Figure 5a) by a 28°
16
Y6Br10Ni, which is known for the iodide. Some of these
failures could be attributed to unfavorable electron counts, but
the better explanation is that the negative results really reflect
the presence of competitive phases that are more stable. The
rationalization of the 60-electron needs in cluster MO terms
i-a
clockwise rotation of the clusters and repositioning of the Br
bridges. The direct interlayer connections by Br3 atoms along
bc are very similar to the interconnections by Br5 in Y16Br24Ir4
shown in Figure 11, but they utilize different edges of the faces
produced by truncation on one layer. The c axes of the two
phases are accordingly very similar in length.
7
has already appeared, and more will follow along with results
for Sc19Br28Z4 phases (Z ) Fe, Ru, Os) in which paramagnetic
29
6
1-electron clusters are necessary.
Support for closed-shell configurations in Y16Br20Ru4 and Y20-
The surprising variety of structures reported here clearly arises
from the number of ways in which the essential bonding needs
of the oligomers can be met both internally (in electron count)
and externally in filling surface bonding orbitals with different
combinations of edge-bridging, face-capping, and exo-bonding
bromine atoms. The change in Y:Br proportions from 4:5
through 4:6 to 5:9 in the compounds described is accompanied
by progressively fewer shared or multiply-bonded bromine
atoms. Thus, among the 36 bromines that cover all of these
oligomeric clusters (Figure 3b), 32 are shared with/bonded to
other oligomers in Y16Br20Ru4, 24 are shared with/bonded to
clusters in Y16Br24Ir4, and only 16 are bonded to other clusters
in Y20Br36Ir4 plus 8 more that are bridged to the YBr3 chains.
The thermodynamic and kinetic interrelationships among these
phases and with respect to other compounds, Y6Br10Z particu-
larly, are obviously complex too (see SynthesissExperimental
Section). One striking feature that distinguishes among the three
synthetically is that Y16Br24Ir4 was obtained only when a flux
of A3Y2Br9 or AYBr6 (A ) Cs-K) was used, while Y20Br36Ir4
was never seen under these conditions because, without large
composition changes, the flux formation produces an unfavor-
ably lower YBr3 activity.
Br36Ir4 has been secured in the present work through magnetic
susceptibility studies that demonstrate these do not exhibit
Curie-Weiss paramagnetism. Their susceptibility data as a
function of temperature (6-300 K) are shown in Figure 18.
The properties of both can be better described in terms of
temperature-independent paramagnetism over ca. 50-300 K or
more after the usual core corrections, with ø300 values of 8.54
-3
-3
×
10 and 1.06 × 10 emu/mol for Y16Br20Ru4 and Y20Br36-
Ir4, respectively. The value for the former appears somewhat
large. This sample had been hand-selected from a mixture of
∼
80% of the target phase with ∼5% of an unknown “Y5Br9-
Ru” and therefore may be less pure, but any impurities must
behave similarly. The smaller øTIP value for Y16Br24Ir4‚4YBr3
comes from a selected sample that appeared from its powder
pattern to contain only the fairly innocent impurities YBr3 and
AlBr3. The magnitude of the data for the latter compound before
correction for core diamagnetism is also shown in the figure to
illustrate how small the differences are.
We are encouraged to attribute these results to Van Vleck
type paramagnetism induced by the magnetic field because of
numerous observations of comparable øTIP values for other
cluster phases, both closed- and open-shell. The isomorphous
Another dominant factor is the evident stability of these
-4
Y16I20Ru4 was earlier found to give øTIP ∼ 4.9 × 10 emu
oligomers with 60 cluster-based electrons, e.g., 16‚3 - 20 +
-1
7
mol over 60-310 K, 6% of that found here for the bromide.
8
‚4 ) 60 in Y16Br20Ru4. (This assignment does not require an
n-
Two different cesium salts containing isolated Zr6Br15Be
clusters, one paramagnetic, yielded TIP values of (4.68-5.41)
ionic picture but requires only that Br valence levels are low-
lying and filled.) The one exception, seen only once in a mixed-
(
28) Schwanitz-Sch u¨ ller, U.; Simon, A. Z. Naturforsch. 1985, B40, 710.
(
27) Hulliger, F. Structural Chemistry of Layer-Type Phases; D. Reidel
(29) Steinwand, S. J.; Martin, J. D.; Corbett, J. D. To be submitted for
publication.
Publishing Co.: Dordrecht, Holland, 1976; p 333.

Oligomeric Rare-Earth-Metal Halide Clusters
Inorganic Chemistry, Vol. 35, No. 24, 1996 7067
4
-1 30
×
10- emu (mol of clusters) . Recently, ø0 terms of (6.6-
constant amount for each cluster size. Finally, TIP behavior is
also found for a number of binary cluster halides, Nb6Cl14 for
example.
-
4
-1
9
.6) × 10 emu mol have been deduced from data for three
3
3
(
)
Curie-Weiss) paramagnetic bicluster phases, Cs2La10I17Z2 (Z
Ni, Os) and La10I15Os2,31 and 1.52 × 10 emu/mol of
-3
We will subsequently report on the novel, paramagnetic
1
5
paramagnetic La12I17Fe2 pertains to two isolated clusters of the
oligomers found in Sc Br Z phases (Z ) Fe, Ru, Os). These
1
9
28 4
i-i
31
8
La6I12Fe type with considerable I bridging. We have not
found any good evidence for electron delocalization and metal-
like behavior in any of these compounds. An older classic study
of five paramagnetic niobium and tantalum cluster halide phases
20 28 4
are derived from the unique Gd I Mn (see Introduction) by
systematic introduction of one disordered cation vacancy into
+
the small clusters (Sc Br ) in order to compensate for four
3
8
additional electrons from the interstitials.
n-
that contain M6X18 units yielded similar ø0 values of (4.8-
-
4
-1 32
Acknowledgment. The authors are indebted to J. E. Osten-
son for measurement of the magnetic data. This research was
supported by the National Science Foundation, Solid State
Chemistry, via Grants DMR-9207361 and -9510278, and was
carried out in the facilities of Ames Laboratory, U.S. Department
of Energy.
6
∼
.5) × 10 emu mol .
These were also corrected (by
-
4
-1
(2.2-2.7) × 10 emu mol ) for the estimated diamagnetic
contributions from bonding electron pairs within the clusters
(
Langevin terms), which depend only on the number and size
of the filled cluster MOs. Such additions would raise the results
for all of the other centered clusters quoted above by about a
Supporting Information Available: Tables of crystallographic and
refinement data, anisotropic displacement parameters, and intracluster
bond angles for all three compounds (9 pages). Ordering information
is given on any current masthead page.
(
30) Qi, R.-Y.; Corbett, J. D. Inorg. Chem. 1995, 34, 1646.
(31) Lulei, M.; Martin, J. D.; Corbett, J. D. J. Solid State Chem. 1996,
125, 249.
(
(
32) Converse, J. G.; McCarley, R. E. Inorg. Chem. 1970, 9, 1361.
33) Simon, A.; Schnering, H.-G.; W o¨ hrle, H.; Sch a¨ fer, H. Z. Anorg. Allg.
Chem. 1965, 339, 155.
IC960650X