Preparation and crystal structure of new one-dimensional Ta selenide: [Ta(Se2)2]2TaBr6

Article abstract of DOI:10.1016/S0277-5387(98)00172-7

Compound [Ta(Se₂)₂]₂TaBr₆ was prepared from elements by high temperature (450°C) stoichiometric reaction in high yield. The structure has been determined by single crystal X-ray diffraction. It contains infinite positively charged chains Ta(Se₂)₂. . . separated by octahedral TaBr₆^- anions. The slightly alternating Ta-Ta distances within the chains [3.182(2)-3.234(2) A] show a considerable degree of metal-metal interaction along the chain.

Full text of DOI:10.1016/S0277-5387(98)00172-7

Polyhedron Vol[ 06\ No[ 10\ pp[ 2624Ð2627\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII] S9166!4276"87#99061!6
Preparation and crystal structure of new one!
dimensional Ta selenide] ðTa"Se1#1Ł1TaBr5
Maxim Sokolov\ab Hideo Imoto\b Taro Saitob\ꢀ and Vladimir Fedorova
aInstitute of Inorganic Chemistry of the Russian Academy of Sciences\ pr[ Lavrentyeva 2\ 529989
Novosibirsk\ Russia
bDepartment of Chemistry\ School of Science\ The University of Tokyo\ Hongo\ Bunkyo!ku\
Tokyo 002!9922\ Japan
"Received 05 January 0887^ accepted 11 April 0887#
Abstract*Compound ðTa"Se1#1Ł1TaBr5 was prepared from elements by high temperature "349>C# stoichio!
metric reaction in high yield[ The structure has been determined by single crystal X!ray di}raction[ It contains
−
in_nite positively charged chains Ta"Se1#1[ [ [ separated by octahedral TaBr5 anions[ The slightly alternating
TaÐTa distances within the chains ð2[071"1#Ð2[123"1# AýŁ show a considerable degree of metalÐmetal interaction
along the chain[ Þ 0887 Elsevier Science Ltd[ All rights reserved
Keywords] crystal structure^ tantalum complexes^ selenium complexes^ bromides^ one!dimensional materials[
———————————————————————————————————————————————
INTRODUCTION
EXPERIMENTAL
Chemistry and solid state physics of low!dimensional
materials is a well established _eld of research activity
ð0\ 1Ł[ Chalcogenides and chalcohalides of Group 4
transition elements have so far furnished dozens of
one!dimensional materials\ the prominent examples
being TaSe2 ð2Ł and a remarkable family of {{interca!
lated|| selenides "NbSe3#yI "y ꢁ 1Ð3# ð3Ł[ The polymeric
NbS1Cl1 has a Nb1"S1#13¦ core and was one of the _rst
well!characterized transition metal chalcohalides ð4Ł[
It has recently been shown to be a convenient lead!in
compound into the still largely unexplored area of
molecular niobium chalcogen complexes ð09\ 00Ł[
The corresponding Ta chemistry is far less developed[
Well characterized products are Ta"Te1#1I ð5Ł\
ðTa"Te1#1Ł3I1"TaI5# ð6Ł\ ðTa"Se1Ł1Ł1I ð01Ł and
ðTa"Te1#1Ł5I3"TaI5# ð8Ł[ Here we report synthesis and
crystal structure of a novel one!dimensional Ta
selenide bromide\ ðTa"Se1#1Ł1TaBr5 "0# as a result of
our investigations in Ta:Se:X1 "X ꢁ Cl\ Br# systems[
A mixture of Ta powder "0[99 g\ 4[42 mmol#\ gray
Se "0[05 g\ 03[58 mmol# and Br1 "9[17 ml\ 4[32 mmol#
was placed in a quartz tube which then was sealed
under vacuum and heated at 349>C for 0 week[ A
temperature gradient was maintained[ The tube was
cooled at 19>C h−0 rate to promote crystal growth[
After cooling down\ almost complete transport into
the cooler end of the tube was observed[ The com!
pound crystallizes in the form of long "up to 0 cm#\
thin black needles[ The yield was 89)[ The elemental
analysis agreed with the formula Ta2Se7Br5 "0#[ The
compound can be handled in air for a limited period
but must be stored under nitrogen to avoid degra!
dation which releases HBr and H1Se in moist air[
Small amounts of bronze!colored TaSe1 and red
TaBr4 "less than 4)# also form as byproducts but can
be easily separated manually from the main product[
The electrical conductivity of crystals of 0 at room
temperature was measured by a two!point contact
method^ s ꢁ 09−3 −0 cm−0
V [
0 Further details of the crystal structure can be ordered
from Fachinformationszentrum Karlsruhe\ 65233 Eggenstein!
Leopoldshafen "e!mail] crysdataÝ_z!karlsruhe[de# under
the depository number CSD!397485[
ꢀ Author to whom correspondence should be addressed[
Fax] ¦70!2!2703!1516^ E!mail] imotoÝchem[s[u!tokyo[
ac[jp[
Crystal structure determination of 0
The structure was determined by the single crystal
X!ray crystallography[ X!ray data were measured at
184 K on a Rigaku AFC!4R di}ractometer with
2624

2625
Maxim Sokolov et al[
Table 1[ Bond lengths "Aý# and some characteristic angles ">#
graphite!monochromated MoKa radiation "lꢁ
9[60958 Aý# with the vÐ1u scan mode[ The DIFABS
program was used for absorption correction[ A slight
decay "4[31) in intensity# was detected during the
data collection and the data were corrected accord!
ingly[ The structure was solved by direct methods
"SHELX!75# ð07Ł[ The full!matrix re_nements were
performed with the teXsan programs ð08Ł[ Crystal
data and re_nement results are given in Table 0[ Selec!
ted interatomic distances are given in Table 1[
Ta"0#ÐTa"0#
Ta"0#ÐTa"1#
Ta"0#ÐSe"0#
Ta"0#ÐSe"6#
Ta"1#ÐTa"1#
Ta"1#ÐSe"3#
Ta"1#ÐSe"4#
Ta"1#ÐSe"7#
Ta"1#ÐSe"5#
Ta"2#ÐBr"2#
Ta"2#ÐBr"3#
Se"0#ÐSe"1#
Se"2#ÐSe"3#
2[087"1#
2[123"1#
1[542"2#
1[589"2#
2[071"1#
1[543"2#
1[591"2#
1[587"1#
1[620"2#
1[355"2#
1[405"2#
1[234"3#
1[242"3#
Ta"0#ÐSe"4#
Ta"0#ÐSe"1#
Ta"0#ÐSe"5#
Ta"0#ÐSe"7#
Ta"1#ÐSe"2#
Ta"1#ÐSe"6#
Ta"2#ÐBr"0#
Ta"2#ÐBr"1#
Ta"2#ÐBr"4#
Ta"2#ÐBr"5#
Se"4#ÐSe"7#
Se"5#ÐSe"6#
1[602"2#
1[515"1#
1[482"2#
1[482"1#
1[514"1#
1[484"2#
1[407"2#
1[419"2#
1[389"2#
1[387"2#
1[253"3#
1[264"3#
RESULTS AND DISCUSSION
Figure 0 shows the ORTEP drawing of the structure
of 0[ The Ta atoms form linear chains running along
the c!axis with slightly alternating TaÐTa distances
2[087"1#\ 2[123"1# and 2[071"1# Aý[ The sequence
Ta"0#ÐTa"0#ÐTa"1#
Ta"0#ÐTa"1#ÐTa"1#
TaÐSeÐTa
068[24"5#
068[25"5#
50[10"7#Ð64[33"6#
41[78"7#
is Ta"0#ÐTa"0#ÐTa"1#ÐTa"1#ÐTa"0#ÐTa"0# [ [ [\ Ta"0#Ð Se"6#ÐTa"1#ÐSe"5#
Se"6#ÐTa"1#ÐSe"7#
Se"4#ÐTa"1#ÐSe"6#
Se"1#ÐTa"0#ÐSe"4#
Se"0#ÐTa"0#ÐSe"7#
BrÐTaÐBr "cis#
70[92"7#
096[60"7#
054[14"8# and 67[77"7#
82[29"7# and 029[56"8#
76[8"0#Ð82[9"0#
Ta"1# being the largest distance[ Se"0# and Se"1# are
bridging Ta"0# atoms\ two Ta"1# atoms are bridged
by Se"2# and Se"3# whereas four non!equivalent Se
atoms ðSe"4#\ Se"5#\ Se"6# and Se"4#Ł connect Ta"0#
with Ta"1#[ The closest analog to 0 is ðTa"Se1#1Ł1I\
BrÐTaÐBr "trans#
064[2"0#Ð067[0"0#
Ä
where all the distances are equal at 2[195"0# A ð01Ł[
Each Ta atom is coordinated to eight Se atoms of
four diselenide bridges[ The SeÐSe distances in the
Se1 ligands vary between 1[24Ð1[27 Aý which can be
compared with 1[39 Aý in ðTa"Se1#1Ł1I ð01Ł[ It has
already been pointed that Se1 groups are rather ~exible
and use their p!antibonding orbitals to serve as an
electronic pool for adjacent metal chains ð0Ł[ The sig!
ni_cantly shorter SeÐSe distance in 0 than in closely
related ðTe"Se1#1Ł1I can thus be explained by stronger
electronic demand of metal chains in the bromine
compound[ The four Se atoms of each bridging pair
of the Se1 ligands lie approximately in planes per!
pendicular to the chains of Ta atoms\ thus forming a
Table 0[ Crystal data and re_nement results for 0
Formula
Ta2Se7Br5
00[128 "1#
01[736 "1#
6[190 "0#
091[40 "0#
87[93 "0#
69[38 "0#
843[1 "2#
1
Ä
a "A#
Ä
b "A#
Ä
c "A#
a ">#
b ">#
g ">#
2
Ä
V "A #
Z
Formula weight
Space group
0542[84
¹
P0 "No[ 1#
F999
0391[99
4[645
300[41
4712
Calculated density "g cm−2
#
m "cm−0
Re~ections collected
Unique
#
4450
Observed ðI × 1[99s"I#Ł
2869
Re~ections:parameters ratio
14[67
9[952
9[947
Ra
b
Rw
aR ꢁ S=Fo−Fc=:SFo[
Fig[ 0[ ORTEP drawing of two repeating units of 0[ Thermal
ellipsoids are drawn at the 49) probability level[
1 0:1
bRw ꢁ ðSw"Fo−Fc#1:SwFo Ł
[

Preparation and crystal structure of new one!dimensional Ta Selenide] ðTa"Se1#1Ł1TaBr5
2626
ðTaBr3"diars#1ŁðTaBr5Ł\ this anion forms almost perfect
Ä
octahedron "TaÐBr 1[38 A# ð03Ł[ The distortions may
be due to additional Se[ [ [Br contacts "the shortest
Ä
one\ between Se"4# and Br"4#\ is 2[051"3# A#\ which
may also favor the observed stacking pattern for the
Se3 rectangles[ The contacts of this kind fall well shor!
ter than the corresponding sum of van!der Waals radii
and are a well established feature in the chemistry of
heavier chalcogens ð04Ł[
Since the bond distances in the anion show the
−
oxidation state of the Ta atom in the TaBr5 unit to
be _ve\ a positive charge ¦0 should he assigned to
the ðTa"Se1#1Ł1 unit[ It means that the Ta atoms have
the oxidation state ¦3[4 which leaves 9[4 e per one
TaÐTa bond "if we consider the diselenium bridges as
Se11−#[ If we take into account the donation of an
extra electron density from the bridging ligands it
will give us less negative charge on the Se1 unit and
correspondingly stronger bonding interaction
Fig[ 1[ Structure projection on the xyO plane[
rectangle with two short and two long sides[ The
dihedral angles between each pair of adjacent Se3 units
are close to 34> to minimize repulsion between Se
atoms and to increase the overlap with 4d orbitals of
Ta ð5Ł[ These restrictions still leave enough room for
di}erent modes of stacking of the Se3 rectangles in the
chain ð5Ł[ In 0 "Fig[ 1# the stacking pattern is the same
as found in the structure of ðNb"Te1#1ŁI ð5Ł but di}ers
from those observed for other Ta"Se1#1 and Ta"Te1#1
between tantalum atoms[ This is in keeping with the
Ä
observed distances of about 2[19 A for
0 and
ðTa"Se1#1Ł1I with the same formal oxidation state[ It is
thus considerably shorter than that in ðTa"Te1#1ŁI
Ä
"2[22Ð2[24 A# where the oxidation state is ¦4 which
implies zero bonding order[ Accordingly\ preliminary
resistivity measurements on the single crystals of 0
gave value which may indicate semiconductive
chains ð5\ 01Ł[ The chains are separated by slightly behavior[
−
distorted TaBr5 anions "the TaÐBr distances are in
The prepared material thus belongs to the by now
Ä
the range 1[36Ð1[41 A#[ In
a
relevant complex extensive family of one!dimensional structures\ hav!
Fig[ 2[ Unit cell drawing of 0[

2627
Maxim Sokolov et al[
2[ Bjerkelund\ E[ and Kjekshus\ A[\ Acta Chem[
Scand[\ 0854\ 08\ 690[
3[ Gressier\ P[\ Meerchaut\ A[\ Guemas\ L[\ Rouxel\
L[ and Monceau\ P[\ J[ Solid State Chem[\ 0873\
40\ 030[
4[ von Schnering\ H[!G[ and Beckmann\ W[\ Z[
Anor`[ All`[ Chem[\ 0855\ 236\ 120[
5[ Tremel\ W[\ Chem[ Ber[\ 0881\ 014\ 1054[
6[ Liu\ S[!X[\ Huang\ D[!P[\ Huang\ C[!C[ and
Huang\ J[!L[\ Polyhedron\ 0885\ 04\ 1184[
7[ Tremel\ W[ and Stork\ K[!L[\ Z[ Naturforsch[\
0882\ 37b\ 0044[
ing positively charged metalÐdichalcogen chains sep!
arated by counteranions "Fig[ 2#[ As for the latter\
both simple small anions "like I−# and large complex
ones "PtI5 ð7Ł\ TaI5 ð6\ 8Ł\ TaBr5−# are e}ective in
the stabilization of this type of structure[ It seems
possible that other anions of various shape and size
may be good candidates as well[
1−
−
In conclusion it may be mentioned that the synthesis
of 0 is one of the rare cases when Nb and Ta do
not behave in a similar way[ Thus\ in the reaction
conditions similar to those used in the present study\
Nb forms NbSe1Br1\ a coordination polymer where
Nb1"Se1#1 cluster units are linked by bromine atoms
similar to NbS1Cl1 ð02Ł[ On the other hand it was not
possible to prepare the Ta analog of NbS1Cl1\ only
TaS2 and TaCl4 could be detected ð02Ł[ One of the
reasons may be the greater reluctance of Ta to form
low oxidation states\ in keeping with the overall trend
in the periodic table[
8[ Huang\ J[!L[\ Liu\ S[!X[\ Huang\ D[!P[\ Huang\
C[!C[\ Jie`ou Huaxue\ 0884\ 03\ 231[
09[ Sokolov\ M[\ Virovets\ A[\ Nadolinnyi\ V[\ Heg!
etschweiler\ K[\ Fedin\ V[\ Podberezskaya\ N[ and
Fedorov\ V[\ Inor`[ Chem[\ 0883\ 22\ 2492[
00[ Sokolov\ M[\ Hernandez!Molina\ R[\ Elsegood\
M[ R[ J[\ Heath\ S[ L[\ Clegg\ W[ and Sykes\ A[
G[\ J[ Chem[ Soc[ Dalton Trans[\ 0886\ 1948[
01[ Gressier\ P[\ Guemas\ L[ and Meerchaut\ A[\ Acta
Cryst[ B\ 0871\ 27\ 1766[
02[ von Schnering\ H[!G[ and Beckmann\ W[\ Z[
Anor`[ All`[ Chem[\ 0855\ 236\ 114[
03[ Drew\ M[ G[ B[\ Walters\ A[ P[ and Wilkins\ J[
D[\ Acta Cryst[\ 0864\ 20b\ 213[
04[ Krebs\ B[ and Ahlers\ F[!P[\ in Advances in Inor!
`anic Chemistry\ Vol[ 24\ ed[ A[ G[ Sykes[ Aca!
demic Press\ 0889\ p[ 124[
Acknowled`ements*We thank the Japan Society for the Pro!
motion of Science for a research fellowship to M[ S[ Financial
support by the Russian Foundation for Basic Research
"grant RFBR!8592!21843# is also acknowledged[
05[ Grenouilleau\ J[ P[\ Meerchaut\ A[\ Guemas\ L[
and Rouxel\ J[\ J[ Solid State Chem[\ 0876\ 55\
182[
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