A new structural form of tin in a double O-capped cluster

Article abstract of DOI:10.1021/ja0287478

Two new cyanorhenate complexes of potential utility in constructing magnetic and photomagnetic materials are reported. Reaction of (Bu₄N)CN with [ReCl₆]^2- in acetonitrile affords yellow (Bu₄N)₃[Re(CN)₇] (1), featuring the pentagonal bipyramidal complex [Re(CN)₇]^3-. The spectral and magnetic properties of 1 indicate that the complex has an S = 1/2 ground state with considerable anisotropy in the g tensor. In aqueous solution, 1 reacts with Mn²⁺ ions to generate the three-dimensional cyano-bridged solid [fac-Mn(H₂O)₃][cis-Mn(H₂O)₂][Re(CN)₇]·3H₂O (2) containing diamagnetic [Re(CN)₇]^4-. Addition of KIO₄ to the reaction solution, originally intended to prevent reduction of the rhenium during solid formation, instead yields white (Bu₄N)₃[Re(CN)₈] (3). As crystallized in K₃[Re(CN)₈]·2MeCN (4·2MeCN), the diamagnetic [Re(CN)₈]^3- complex adopts a nearly perfect square antiprismatic coordination geometry. In solution, this species behaves analogously to the isoelectronic [M(CN)₈]^4- (M = Mo, W) complexes, apparently converting to a dodecahedral geometry and photooxidizing under UV radiation to give paramagnetic [Re(CN)₈]^2-. Copyright

Full text of DOI:10.1021/ja0287478

Published on Web 02/07/2003
A New Structural Form of Tin in a Double O-Capped Cluster
Vadapalli Chandrasekhar,*,† Viswanathan Baskar, and Jagadese J. Vittal‡
†
Department of Chemistry, Indian Institute of Technology, Kanpur-208016, India, and Department of Chemistry,
National UniVersity Of Singapore, Singapore 117543
Received September 30, 2002 ; E-mail: vc@iitk.ac.in
Rings, cages, and clusters containing organooxotin motifs in
general and distannoxane motifs in particular have been attracting
considerable attention in recent years.1 In addition to the interest
arising from the potential utility of these assemblies in the
-3
4
preparation of new materials there has also been a significant
interest in exploiting the remarkable structural plasticity of these
stannoxane motifs. Thus, for example the four-membered distan-
2 2
noxane motif Sn O is found in a number of structural forms such
5
a
5b-d
5e,f
5f,g
as the ladder, drum,
cube, O-capped cluster, football
6
cage etc. Although, many structural forms containing the Sn O
2
2
unit have been discovered so far the inter-relationship between these
various forms has not been delineated in any great detail. However,
some clues do exist. Thus, the partial hydrolysis of an organotin-
tricarboxylate, RSn(O
RSn(O CR′) , which undergoes further transformation to a drum
RSn(O)O CR′]
OH)O PPh O][Ph
2 3 2 2
CR′) affords first a ladder [(RSn(O)O CR′) -
2
3 2
]
7
[
(
2
6
. Trinuclear O-capped clusters such as [{n-BuSn-
PO ] have been isolated in the reaction of
2
2
}
3
2
2
5
f
n-butylstannonic acid and diphenylphosphinic acid. The structural
relationship between the drum and the O-capped cluster is that the
latter represents a hydrolysis product of the hexameric drum. Two
units of the O-capped cluster can be joined to each other in a face-
face manner with a rearrangement in the phosphinate bridges and
Sn-O bonds to afford the drum. We now report an unprecedented
Figure 1. DIAMOND view of 1. The hydrogen atoms of the n- butyl and
the phenyl groups have been removed. The disordered carbon atoms on
the tin atoms labeled Sn1 and Sn1A have also been omitted for clarity.
Selected bond lengths [Å] and bond angles [deg] are: Sn(2)-O(3) 2.053-
(
1), Sn(2)-O(2) 2.163(1), Sn(2)-O(1) 2.201(2), Sn(2)-O(6) 2.064(2), Sn-
2)-O(5) 2.071(2), Sn(1)-O(3) 2.090(3), Sn(1)-O(1) 2.152(3), Sn(1)-
(
O(4) 2.081(2), P(1)-O(6) 1.515(2), P(1)-O(5) 1.519(2), P(1)-O(4)
1.525(2), O(3)-Sn(2)-O(5) 88.19(7), O(6)-Sn(2)-O(5) 88.40(7), O(6)-
Sn(2)-O(2) 88.51(8), O(5)-Sn(2)-O(2) 161.10(7), O(6)-Sn(2)-O(1)
structural form of tin viz., a double O-capped cluster [{(n-BuSn)
PhO) O} {HPO ], 1, where two O-capped tin clusters each
containing a Sn unit are linked in a back-back manner by the
intervention of bridging phosphonate ligands. The synthesis and
X-ray crystal structure of this compound are discussed in the
following account. The structural relationship of the cage 1 obtained
in the present study with that of other structures known, particularly
the football cage, is also discussed.
3
-
(
3
2
3 4
}
1
67.31(7), O(5)-Sn(2)-O(1) 85.57(7), Sn(2)-O(3)-Sn(1) 108.32, P(1)-
O(4)-Sn(1) 127.91(11), O(4)-P(1)-O(6B) 111.07(11), O(4)-P(1)-O(5A)
12.28(10).
3
1
8
Scheme 1
In view of the reported isolation of the double cube [{n-BuSnS-
(
O
2
PPh
2 3 2 2
)} O] Sn in the reaction of [n-BuSnO(OH)] with Ph P(O)H
9
in the presence of sulfur we probed an analogous reaction involving
n-BuSnO(OH)] and (PhO)
2
P(O)H but without the use of sulfur.1
0a
[
We discovered that the reaction proceeds to afford a completely
unprecedented product which involves an in situ P-O bond
observed in the 119Sn NMR are indicative of the CO
environment around tin.
The X-ray crystal structure analysis of 1 shows that it has a cage-
type of architecture. A DIAMOND view of 1 is shown in Figure
coordination
5
2-
cleavage leading to the generation of a [HPO
phenol. Thus, the compound isolated [{(n-BuSn)
HPO ], 1, has a Sn:P ratio of 6:4 and Sn:OPh ratio of 1:1. We
3
]
ion along with
3
(PhO) O}
3
2
-
{
3 4
}
were also able to obtain 1 in a direct route involving the reaction
of [n-BuSnO(OH)] with phenol and phosphorous acid (Scheme
1
. Selected metric parameters are summarized in the figure caption.
The molecular structure of 1 consists of two tritin motifs viz., {(n-
BuSn) (PhO) O} that are connected to each other by means of four
tripodal HPO ligands. The poles of the cage comprise of three tin
centers held together by a µ -oxygen. Further three phenoxides are
10b
1
). It may be noted that we have recently demonstrated the utility
3
3
of phosphonate ligands in the assembly of multimetallic clusters
3
11
involving transition metal ions. Compound 1 is thermally stable
and does not decompose until 290 °C. In addition it is quite
lipophilic and is soluble in a wide range of organic solvents. The
3
2
involved as bridging ligands; a µ -oxygen of each phenoxide binds
two adjacent tin atoms.
Thus, the tritin subunit of the cage consists of three Sn
that are nearly perpendicular to each other. This is similar to the
molecular structure of the O-capped cluster reported earlier. The
most important structural variation comes in the linking of the two
1
1
presence of P-H is confirmed by H NMR (δ 7.13; J(P-H): 690
2 2
O rings
Hz) and 31P NMR (δ 0.57). The high negative chemical shifts
5
f
†
Indian Institute of Technology.
National University Of Singapore.
‡
2392
9
J. AM. CHEM. SOC. 2003, 125, 2392-2393
10.1021/ja0287478 CCC: $25.00 © 2003 American Chemical Society

C O MMU N I C A T I O N S
Acknowledgment. We are thankful to Department of Science
and Technology, New Delhi, India, for financial support. This paper
is dedicated to Prof. G. Mehta on the occasion of his 60th birthday.
Supporting Information Available: X-ray crystallographic file
(
CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
References
(
1) (a) Janssen, J.; Magull, J.; Roesky, H. W. Angew. Chem., Int. Ed. 2002,
1, 1365. (b) Wraage, K.; Pape, T.; Herbst-Irmer, R.; Noltemeyer, M.;
4
Schmidt, H.-G.; Roesky, H. W. Eur. J. Inorg. Chem. 1999, 869.
2) (a) Dakternieks, D.; Jurkschat, K.; Schollmeyer, D.; Wu, H. Organome-
tallics 1994, 13, 4121. (b) Mehring, M.; Paulus, I.; Zobel, B.; Sch u¨ rmann,
M.; Jurkschat, K.; Duthie, A.; Dakternieks, D. Eur. J. Inorg. Chem. 2001,
(
153. (c) Mehring, M.; Sch u¨ rmann, M.; Reuter, H.; Dakternieks, D.;
Jurkschat, K. Angew. Chem., Int. Ed. Engl. 1997, 36, 1112. (d) Schulte,
M.; Sch u¨ rmann, M.; Dakternieks, D.; Jurkschat, K. Chem. Commun. 1999,
1291.
(
(
(
3) (a) Chandrasekhar, V.; Nagendran, S.; Baskar, V.; Coord. Chem. ReV.
2002, 235, 1. (b) Holmes, R. R. Acc. Chem. Res. 1989, 22, 190.
4) Ribot, F.; Baron, C. E.; Sanchez, C. Phosphorus, Sulfur, Silicon Relat.
Elem. 1999, 150-151, 41 and references therein.
5) (a) Holmes, R. R.; Schmid, C. G.; Chandrasekhar, V.; Day, R. O.; Holmes,
J. M. J. Am. Chem. Soc. 1987, 109, 1408. (b) Chandrasekhar, V.; Day, R.
O.; Holmes, R. R. Inorg. Chem. 1985, 24, 1970. (c) Chandrasekhar, V.;
Nagendran, S.; Bansal, S.; Kozee, M. A.; Powell, D. R. Angew. Chem.,
Int. Ed. 2000, 39, 1833. (d) Day, R. O.; Chandrasekhar, V.; Kumara
Swamy, K. C.; Holmes, J. M.; Burton, S. D.; Holmes, R. R. Inorg. Chem.
Figure 2. Comparison of the crystal structure of 1, the double O-capped
b) with the O-capped (a), the drum (c), and the football cage (d) In this
(
DIAMOND representation, violet represent the tin atoms, red the oxygens
and yellow represents the phosphorus atoms. In all the structures only the
tin-oxygen core is shown for clarity.
1
988, 27, 2887. (e) Kumara Swamy, K. C.; Day, R. O.; Holmes, R. R. J.
Am. Chem. Soc. 1987, 109, 5546. (f) Day, R. O.; Holmes, J. M.;
Chandrasekhar, V.; Holmes, R. R.; J. Am. Chem. Soc. 1987, 109, 940.
poles in the present structure by the bridging phosphonate groups.
Thus, each phosphonate binds in a bridging mode using two of its
oxygens to link two tins from the same pole and one tin from the
opposite pole. All the six tin centers are thus effectively stitched
(
g) Holmes, R. R.; Kumara Swamy, K. C.; Schmid, C. G.; Day, R. O. J.
Am. Chem. Soc. 1988, 110, 7060.
(
6) (a) Baron, C. E.; Ribot, F.; Steunou, N.; Sanchez, C.; Fayon, F.; Biesemans,
M.; Martins, J. C.; Willem, R. Organometallics, 2000, 19, 1940. (b) Ribot,
F.; Toledano, P.; Maquet, J.; Sanchez, C. Inorg. Chem. 1995, 34, 6371.
(c) Ribot, F.; Sanchez, C.; Willem, R.; Martins, J. C.; Biesemans, M.
3
with each other by means of four tripodal HPO ligands. Conse-
quently, two cyclic rings each containing six oxygen atoms
sandwich a central rim of four phosphorus atoms. The average
Inorg. Chem. 1998, 37, 911. (d) Baron, C. E.; Ribot, F.; Sanchez, C. J.
Organomet. Chem. 1998, 567, 137. (e) Dakternieks, D.; Zhu, H.; Tiekink,
E. R. T.; Colton, R. J. Organomet. Chem. 1994, 476, 33.
(
7) Chandrasekhar, V.; Schmid, C. G.; Burton, S. D.; Holmes, J. M.; Day, R.
O.; Holmes, R. R. Inorg. Chem. 1987, 26, 1050.
(µ
3
)O-Sn bond length is 2.065 Å, while the average (µ )O-Sn
2
(
8) Crystal data for 1. The structure was solved by direct methods and refined
bond length is 2.172 Å. These values are comparable to literature
precedents.5 The average Sn-O distance involving the bridging
phosphonate is 2.072 Å.
2
12
by using full-matrix least-squares on F (SHELX97 ). Monoclinic, space
group C2/m, a ) 16.9713(7) Å, b ) 15.6743(6) Å, c ) 14.2523(6) Å,
f,6
3
3
â ) 105.5550°, V ) 3652.4(3) Å , Z ) 2, Fcalcd ) 1.787 Mg/m , T )
2
23(2) K, reflections collected ) 14858, 5373 independent reflections
R(int) ) 0.0242], Mo KR radiation, λ ) 0.71073 Å, θ range for data
collection ) 1.80-30.00°, absorption correction - Sadabs(Sheldrick,
It is interesting to compare the double-O-capped structure found
in the present instance with that of the foot-ball cage and the drum
[
1
996), final R indices [I > 2σ(I)] R1 ) 0.0282, wR2 ) 0.0615, R indices
(Figure 2). As noted vide supra the fusion of two O-capped clusters
(
1
all data) R1 ) 0.0349, wR2 ) 0.0630, largest diff. peak and hole )
-3
.125 and -0.394 e‚ Å . The hydrogen on the phosphorus atom was
in a face-face manner affords the hexameric drum. The football
cage on the other hand is dodecanuclear. Both 1 and the football
located from the difference maps and the positions were refined. All the
other hydrogens were fixed at calculated positions.
(
9) Kumara Swamy, K. C.; Day, R. O.; Holmes, R. R. J. Am. Chem. Soc.
cage have exactly identical pole structures comprising of two Sn
3
1988, 110, 7543.
motifs. Whereas in the football cage structure the two poles are
connected to each other by means of an equator made up of the
(
10) Synthesis: Compound 1 has been prepared by two synthetic routes. (a)
n-Butylstannonic acid (2.20 g, 10.5 mmol) and diphenyl phosphite (1.64
g, 7.00 mmol) were taken in 100 mL of toluene and heated under reflux.
After about 45 min the solution became clear. Heating was continued for
a further period of 5 h. At this stage the reaction mixture was allowed to
cool to room temperature and filtered. The filtrate was reduced to one-
tenth of its initial volume (10 mL) in Vacuo and kept for crystallization
at room temperature. Within a period of 3-4 weeks colorless blocklike
crystals were formed which were separated by filtration. The crystals were
{
6
(RSn) O12} motif, in the present instance it is replaced by an
inorganic phosphonate (HPO
tetrahedral and contains a HO
3
)
4
motif where each phosphorus is
3
coordination environment. Interest-
ingly, despite the diverse equator motifs the cage dimensions in 1
and the football cage are similar. Thus, the distance between the
diametrically opposite tin atoms (in the equator) in the football
cage is 6.407 Å. In 1 the corresponding atoms P1 and P1B are
purified further by quickly washing them with chloroform (3 mL). Yield
1
0.70 g (20%). Mp 290-292 °C dec; H NMR (CDCl
3
, ppm) 0.50-0.73
(
m, 18H, CH
3
of n-Bu), 0.80-1.46 (m, 36H, CH
2
of n-Bu), 6.83-7.35
1
31
(
m, 30H, phenyl), 7.13 (d, 4H, J(H-P) ) 690 Hz); P NMR (CDCl
3
,
1
119
separated by a distance of 6.337 Å. Also the interpolar µ
distances in 1 and in the football are 3.778 and 3.984 Å,
respectively. In 1 the presence of µ -OPh represents a situation
3
-O
ppm) 0.57 (d, J(P-H) ) 688 Hz); Sn NMR (CDCl
3
, ppm) -532.7
(
88 20 4
m), -551.3 (m), -563.6 (m); elemental analysis Calcd for C60H O P -
Sn
6
: C 36.66%, H 4.51%; found: C 36.11%, H 4.09%. (b) n-Butylstan-
nonic acid (0.93 g, 4.45 mmol), phenol (0.42 g, 4.46 mmol), and
phosphorous acid (0.24 g, 2.92 mmol) were taken in 60 mL of toluene
and refluxed. A Dean-Stark apparatus was used to remove the water
formed in the reaction by azeotropic distillation. Workup of the reaction
mixture as described in the previous preparation afforded a white solid.
Yield 0.45 g (31%). The spectroscopic and analytical data for the
compound obtained in this preparation matched with those given in the
above procedure.
2
where the polar hydroxyls of the O-capped cluster or the football
cage6 are completely replaced by a phenoxide. In this regard this
is the first instance where such a replacement has been unambigu-
ously recorded.
e
Thus, in conclusion, we have isolated and structurally character-
ized a double O-capped cluster, which represents a new structural
form. The current synthetic methodology also opens up possibilities
for assembling nanobuilding blocks for the design of tin-based
hybrid organic-inorganic materials through the use of biphenols.
These studies are currently in progress.
(
11) (a) Chandrasekhar, V.; Kingsley, S. Angew. Chem., Int. Ed. 2000, 39,
2320. (b) Chandrasekhar, V.; Kingsley, S.; Rhatigan, B.; Lam, M. K.;
Rheingold, A. L. Inorg. Chem. 2002, 41, 1030.
(
12) Sheldrick, G. M. SHELX97, Programs for Crystal Structure Analysis;
Institut f u¨ r Anorganische Chemie der Universit a¨ t G o¨ ttingen: Germany,
1998.
JA0287478
J. AM. CHEM. SOC.
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