Indium triiodide complexes of bis(diphenylphosphino)ethane (dppe) and its disulfide (dppeS2)

Article abstract of DOI:10.1515/znb-1999-0107

Bis(diphenylphosphino)ethane (dppe) and its disulfide (dppeS₂) react with two equivalents of indium triiodide to give high yields of the corresponding 1:2 adducts. According to crystal structure determinations, both compounds are molecular bis-

Full text of DOI:10.1515/znb-1999-0107

Indium Triiodide Complexes of Bis(diphenyIphosphino)ethane (dppe)
and its Disulfide (dppeS2)
M arcus Sigl, Annette Schier, H ubert Schm idbaur*
Anorganisch-chemisches Institut der Technischen Universität München,
Lichtenbergstrasse 4, D-85747 Garching, Germany
Z. Naturforsch. 54 b, 21-25 (1999); received October 10, 1998
Indium Triiodide, Phosphine Complexes, Phosphine Sulfide Complexes, Conformation, Crystal
Structure
Bis(diphenylphosphino)ethane (dppe) and its disulfide (dppeS2) react with two equivalents
of indium triiodide to give high yields of the corresponding 1:2 adducts. According to crys-
tal structure determinations, both compounds are molecular bis-terminal complexes with the
ligands in an all-trans conformation. Contrary to previous findings for complexes of the
indium trihalides and of GaBr3 and Gal3 with ditertiary phosphines in fixed cis-structure
[bis(diphenylphosphino)ethene or -benzene], no iodide redistribution is observed to give the
ionic species [(dppe)Inl2]+ [InL]- . The molecular structures are also retained in solution.
Introduction
larly attractive, because they may act as bridging
and chelating ligands depending m ainly on the rel-
ative sizes of the ligand span and the radius of the
metal. Our initial studies w ith the gallium and in-
dium trihalides have shown a rich structural diver-
sity, including both m olecular and ionic com plexes
with various ring sizes and coordination num bers
(CN) [6], W hile in phosphine com plexes of InC h
and InB r3 the metal atom reaches CN 6, the m axi-
m um CN for the adducts with M 3 is lim ited to 5,
probably owing to steric congestion.
In order to probe further the ligand capabili-
ties of diphosphines towards M 3 we em ployed
bis(diphenylphosphino)ethane (dppe) and its disul-
fide (dppeS2) as ligands, w here a flexible hydrocar-
bon loop between the donor centers should allow
for a better m atch of the com ponents. M 3 is known
to form a m olecular 1:2 com plex w ith PPh3, the
indium atom of which is in a trigonal bipyram idal
coordination environm ent with the tw o phosphines
occupying the apical positions [5b]. The literature
contains also a report of the 1:1 com plex of Inl3
and dppe which appears as a coordination polym er
[(dppe)Inl3]x, again with pentacoordinate indium
atom s. The 2:3 com plex represents a segm ent of this
polym er (dppe)Inl3(dppe)Inl3(dppe) w ith tw o free
term inal phosphino functions [5c]. The 2:1 com plex
has also been prepared previously, but its structure
is yet unknown [5b, d, e, f].
The trihalides o f the G roup III elem ents E X 3 are
strong Lewis acids w ith a high potential as catalysts
[1]. The catalytic activity can be m odified by care-
fully selecting the right central m etal (E = B, Al,
Ga, In, Tl) and halogen (X = F, Cl, Br, I), but also
by auxiliary ligands L which m ay reduce the ac-
ceptor properties to make reactions more selective
under mild conditions [2]. The role of the ligand L
is often played by the solvent m olecules, typically
diethylether or tetrahydrofuran, or by an auxiliary
com ponent like a dialkylsulfide or a tertiary phos-
phine.
W hile such com plexes X 3E -L are well docu-
m ented for the boron and alum inium halides (E =
B, Al), the corresponding gallium and indium com -
pounds (E = Ga, In) have received m uch less atten-
tion [3]. Since there is current interest in the usage
of gallium and indium halides as m ore selective re-
action prom otors [4], a system atic study of the sto-
ichiom etry, properties and structure of com plexes
o f these halides w ith phosphines is currently under
way [5].
Tertiary phosphines are versatile ligands w hich
are com m ercially available in
a large variety of
functionalities. D itertiary com pounds are particu-
* Reprint requests to Prof. Dr. H. Schmidbaur.
0932-0776/99/0100-0021 $ 06.00 (c) 1999 Verlag der Zeitschrift für Naturforschung, Tübingen ■www.znaturforsch.com
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M. Sigl et al. ■Indium Triiodide Complexes of Bis(diphenylphosphino)ethane
nance which appears at m uch higher field (b -27.1)
22
Ph\ /Ph
Ph Ph
\
/
S>— Inl,
^P
than the resonance of the parent ligand (6 -12.5).
This is an unusual phenom enon for phosphine co-
ordination to m ost M ain G roup and Transition M et-
als, but there is precedent for the same effect in the
particular case of other heavy Main G roup M etals,
including gallium and indium trihalide com plexes
[6 ]. It therefore appears that this behaviour is com -
m on for M ain G roup M etals in the low er parts of
the Periodic Table. Several high level theoretical
studies are currently under way in several laborato-
ries to rationalize the data in term s of the electronic
characteristics of heavy elem ents.
+
2 lnl3
(1 )
l3ln—P
P
3
/ \
/
\
Ph Ph
Ph Ph
Ph\ /Ph
Ph Ph
\
/
P = S -ln l3
P = S
(2 )
+
2 lnl3
/
3ln—S=/P\
S=/P\
Ph Ph
2
Ph Ph
Results
Solutions o f com pound 2 in chloroform also show
only a singlet signal in the 31P { 1H } N M R spectrum
(6 48.9), but only slightly shifted down-field relative
to the resonance of free (dppeS2) because the co-
ordination does not occur at the phosphorus center.
The 'H and l3C { 'H } N M R spectra of 1 and 2 show
no anom alies and are not significantly tem perature-
dependent.
Two equivalents of indium triiodide react with
one equivalent of (dppe) or (dppeSo) in anhydrous
toluene at 80°C to give high yields of the expected
1:2 com plexes as colourless crystals w ith high m elt-
ing points (1: m.p. 241°C, 2: m.p. 226 °C, with de-
com position).
Both com pounds are very sensitive to moisture
as solids and in solution and must be handled in a
rigorously dried inert atm osphere.
Crystals of 1 are m onoclinic, space group P2]/n,
w ith Z = 4 form ula units in the unit cell. The lat-
tice is com posed of individual m olecules w ith no
sub-van der W aals contacts. The m olecules have
no crystallographically im posed symm etry, but the
structure approaches quite closely the sym m etry
Solutions o f com pound 1 in dichlorom ethane
show in the 31P { 1H} N M R spectrum a singlet reso-
Fig. 1. Molecular structure of compound l.(ORTEP draw-
ing with 50% probability ellipsoids, Ho-atoms are omitted
for clarity). Selected bond lengths [A] and angles [°]:
Inl-PI 2.6035(12), Inl-II 2.6523(6). In 1-12 2.6833(5),
In 1-13 2.7023(6), In2-P2 2.5966(12), In2-I4 2.6843(6),
In2-I5 2.6773(5), In2-I6 2.6685(5), PI-Cl 1.836(4),
C1-C2 1.530(6), C2-P2 1.828(4); P l-Inl-Il 108.95(3),
P 1-In 1-12 98.59(3), Pl-Inl-I3 103.41(3), Il-Inl-I2
120.73(2), II-In 1-13 112.20(2), I2-Inl-I3 110.65(2),
P2-In2-I4 104.84(3), P2-In2-I5 117.15(2), P2-In2-I6
106.53(3). I4-In2-I5 113.78(2). I4-In2-I6 113.31(2). 15-
In2-I6 117.15(2).
Fig. 2. Molecular structure of compound 2.(ORTEP draw-
ing with 50% probability ellipsoids, Ph-// atoms are omit-
ted for clarity). Selected bond lengths [A] and angles
[°]: In-Sl 2.5322(13), In-11 2.6859(5), In-12 2.6901(6),
In-13 2.6733(5), Pl-Sl 2.011(2), Pl-Cl 1.807(5), C l-C l'
1.521(9);Sl-In-Il 98.88(3),Sl-In-I2 109.58(4),Sl-In-I3
108.06(4), II-In-12 110.00(2), II-In-13 111.47(2). I2-In-
13 117.24(2), In-Sl-PI 111.11(6).
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M. Sigl et al. • Indium Triiodide Complexes of Bis(diphenylphosphino)ethane
23
Table I. Crystal data, data collection, and structure refinement for compounds 1 and 2.
1
2
Crystal data
Formula
M,
Crystal system
Space group
a (A)
*(A)
c (A)
a (° )
C26lT 4l6l n ^ S .
1453.55
monoclinic
P2\/c
12.184(1)
14.640(1)
11.962(1)
90
1389.43
monoclinic
P2 ]/n
10.460(1)
15.481(1)
22.920(2)
90
98.67(1)
90
114.97(1)
90
ß ( ° )
7
O
3669.1(5)
2.515
4
1934.3(3)
2.496
2
V (A )
Pcalc (gem 3 )
Z
F(000)
1316
2515
^ ( M o A 'q ) (cm-1)
64.08
61.87
Data collection
T (°C)
-74
+21
Scan mode
hkl Range
uJ - 0
u - 2 0
-1 2 — 12,-10 — 0, -28 — 28
-1 4 — 15, 0 — 18,-15 — 0
0.62
0.62
sin($/A)max (A-1)
Measured reflections
Unique reflections
Refls. used for refinement
Absorption correction
8479
3984
6624 [Rint = 0.0309]
6615
psi-scans
0.56/0.99
3810 [/?int = 0.0200]
3801
psi-scans
0.84/0.99
Tmin / T^max
Refinement
Refined parameters
Final R values [I > 2cr(1)]
R \[i]
325
180
0.0275
0.0275
wR2[b]
0.0611
0.0588
< 0.001
< 0.001
(shift/error)max
o
/9fin(max/min) (eA-3)
1.135/-1.442
0.735/-0.742
{[Iw (F02 - F c2)2]/I[w (F 02)2]}'/2;
[al R\ = KIIFol - IFJI / IlFol; [b| wR2 =
w = l/[cr2(F02) + (ap) 2 + bp]\p = (F02 +
2Fc2)/3; a = 0.0269 (1), 0.0245 (2); b = :9.84 (1), 3.09 (2).
requirem ents of an inversion center (point group
Q , Fig. 1). The ligand is in an extended staggered
all-trans conform ation. Both the phosphorus and in-
dium atom s are strictly tetra-coordinated and show
no significant distortions from tetrahedral geom e-
tries. It is most im portant to note that a structure
o f this type is found although there is a choice be-
tween this m olecular form and an ionic alternative
[(dppe)Inl2]+ [InLt]- . The solubility properties and
the NM R data are consistent with a non-ionic dinu-
clear structure also for the solution state.
which has a crystallographically im posed center of
inversion (Fig. 2). This again calls for an extended
ligand with tetrahedral chain m em bers -PPhb-CI-b-
C Fh-PPfb- in the staggered all-trans conform ation.
The M 3 units are attached to the sulfur atom s with
an angle P-S-In = 111.11(6)°. The dim ensions of
the Inl3 units are virtually the same in com pounds
1 and 2.
Conclusions
Crystals of 2 are also m onoclinic, space group
P2i/c, with Z = 2 form ula units in the unit cell. The
lattice contains individual m olecules the structure of
The present results have shown that both dppe and
its disulfide form m olecular dinuclear com plexes
with indium triiodide w ith quasi-centrosym m etrical
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24
M. Sigl et al. • Indium Triiodide Complexes of Bis(diphenylphosphino)ethane
structures involving extended all-trans ligands. A c-
cording to low tem perature 1|P NM R studies there
is no evidence for an equilibrium with ionic com -
ponents in which the ligands are chelating a metal
atom . This is at variance w ith the findings for the
corresponding com plexes of bidentate ligands in
w hich the two donor centers are fixed in a cis
position at a rigid backbone. It therefore appears
that even w ithin a closely analogous series of com -
pounds there may be fundam ental changes in the
structural principle.
'H NMR (CDCI3, 20°C): b 2.45 (A2XX'A'2, 2 H, CH2);
7.58 - 7.85 (m, 10 H, Ph). ,3C{'H} NMR (v.s.): b 23.2
(AXX\ CH2); 123.8, 130.5, 132.4, 135.0 (all AXX’, for
Ph-C). 31P{'H} NMR (v.s.): b 48.9 (s).
C26H.4l6ln^P2S. (1453.55)
Calcd C 21.48 H 1.66 S4.41 %,
Found C 21.40 H 1.72 S 4.28 %.
Crystal structure determinations
Specimens of suitable quality and size of compounds
1 and 2 were mounted in glass capillaries and used for
measurements of precise cell constants and intensity data
collection on an Enraf Nonius CAD4 diffractometer (Mo-
Ka radiation, A(Mo-ATQ) = 0.71073 A) . During data col-
lection, three standard reflections were measured period-
ically as a general check of crystal and instrument sta-
bility. No significant changes were observed for either
compound. Lp correction was applied and intensity data
were corrected for absorption effects. The structures were
solved by direct methods and completed by full-matrix-
least squares techniques against F2.The thermal motion of
all non-hydrogen atoms was treated anisotropically. All H
atoms of compound 1 were placed in idealized calculated
positions and allowed to ride on their corresponding car-
bon atoms with fixed isotropic contributions ( U jSO(fix) = 1-5
x U eq of the attached C atom), whereas the CH2 atoms of
compound 2 were located and refined with isotropic con-
tributions. Further information on crystal data, data col-
lection and structure refinement are summarized in Table
I. Important interatomic distances and angles are shown in
the corresponding Figure Captions. Anisotropic thermal
parameters, tables of distances and angles, and atomic
coordinates have been deposited with Fachinformation-
szentrum Karlsruhe, Gesellschaft für wissenschaftlich-
technische Information mbH, D-76344 Eggenstein-Leo-
poldshafen. The data are available on request on quoting
CSD No. 410282 (1) and 410283 (2).
Experimental Part
All experiments were carried out in standard equip-
ment with rigorous exclusion of air and moisture. The
starting materials are commercially available. The dppeS2
was prepared following a literature procedure [7],
[ 1,2-Bis(diphenylphosphino)ethane](Inl->,)2 (\)
Indium triiodide (307 mg, 0.619 mmol) is added to
a solution of dppe (123 mg, 0.310 mmol) in 20 ml of
toluene. The resulting mixture is stirred at 80°C for 1 h.
Upon cooling to -30°C a colourless precipitate is formed
which is collected after 1 d (0.31 g, 72% yield) and re-
crystallized from chloroform/pentane (m.p. 241 °C). !H
NMR (CD2C12, 20°C): b 3.08 [d, 7(P,H) = 3 Hz, 2 H,
CH2]; 7.53 - 7.94 (m, 10 H, Ph). I3C {‘H} NMR (v.s.): 6
23.9 [d, 7(P,C) = 24 Hz, CH2]; 121.9 [d, 7(P,C) =44 Hz,
C ip so ], 130.6 [d, J = 11 Hz, Cmetal, 133.7 [d, J = 10 Hz,
Corthol, 133.8 [s, Cpara]• 31P{'H} NMR (v.s.): b -21A (br.
s). 31P{'H} NMR (CD2CI2, -80°C): b -25.7 (br. s).
C26H74l6ln2P2 (1389.43)
Calcd C 22.47 H 1.74 %,
Found C 21.94 H 1.62%.
[1,2-Bis(diphenylphosphino)ethane disulfide](Inh)2 (2)
Infs (250 mg, 0.505 mmol) is added to a solution of
dppeS2(117 mg, 0.252 mmol) in 10 ml of chloroform. The
mixture is stirred for 10 h at 20°C. A colourless precipitate
is formed (0.30 g, 82% yield), which is recrystallized from
dichloromethane/diethylether (m.p. 226°C, decomp.).
Acknowledgement
This work was supported by Fonds der Chemischen
Industrie. The authors are grateful to Mr. J. Riede for
establishing the X-ray data sets.
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M. Sigl et al. ■Indium Triiodide Complexes of Bis(diphenylphosphino)ethane
25
[5] a) M. A. Brown, J. A. Castro, D. G. Tuck, Can. J.
Chem. 75, 333 (1997);
[1] a) L. A. Paquette, Encyclopedia of Reagents for Or-
ganic Synthesis, p. 153, Wiley, New York (1995);
b) J. A. Miller, in A. J. Downs, Chemistry of Alu-
minium, Gallium, Indium, and Thallium, p. 372,
Chapman & Hall, London (1993).
[2] a) J. A. Jegier, D. A. Atwood, Inorg. Chem. 36,2034
(1997);
b) M. A. Brown, E. J. Wells, D. G. Tuck, Can. J.
Chem. 74, 1535 (1996);
c) I. A. Degnan, N. W. Alcock, S. M. Roe, M. G. H.
Wallbridge, Acta Crystallogr. C48, 995 (1992);
d) A. J. Carty, Can. J. Chem. 45, 345 (1967);
e) A. J. Carty, Can. J. Chem. 45, 3187 (1967);
f) A. Balls, N. N. Greenwood, B. P. Straughan, J.
Chem. Soc. (A) 1968, 753;
b) J. A. Jegier, D. A. Atwood, Inorg. Chem. 35,4277
(1996);
c) T. Aida, S. Inoue, Acc. Chem. Res. 29, 39 (1996);
d) Y. Hayashi, J. J. Rohde, E. J. Corey, J. Am. Chem.
Soc. 118, 5502(1996).
g) U. Flörke, H.-J. Haupt, Z. Kristallogr. 196, 299
(1991);
h) R. L. Wells, S. R. Aubuchon, S. S. Kher, M. S.
Lube, P S. White, Chem. Mater. 7, 793 (1995);
i) M. V. Veidis, G. J. Palenik, J. Chem. Soc., Chem.
Commun. 1969, 586;
j) W. Clegg, N. C. Norman, N. L. Pickett, Acta
Crystallogr. C50, 36 (1994);
k) N. W. Alcock, I. A. Degnan, O. W. Howarth,
M. G. H. Wallbridge, J. Chem. Soc., Dalton Trans.
1992, 2775;
[3] a) D. G. Tuck in A. J. Downs, Chemistry of Alu-
minium, Gallium, Indium, and Thallium, p. 430,
Chapman & Hall, London (1993);
b) D. G. Tuck in G. Wilkinson, R. D. Gillard, J. A.
McCleverty, Comprehensive Coordination Chem-
istry, Vol. 3, 126, Pergamon Press, Oxford (1987);
c) D. G. Tuck in G. Wilkinson, F. G. A. Stone,
E. W. Abel, Comprehensive Organometallic Chem-
istry, Vol. 1, 683, Pergamon Press, Oxford (1982);
d) A. J. Carty, D. G. Tuck in S. J. Lippard, Progress
in Inorganic Chemistry, Vol. 19,243, Wiley & Sons,
New York (1975).
1) A. J. Carty, D. G. Duck, J. Chem. Soc. (A) 1966,
1081;
m) W. T. Robinson, C. J. Wilkins, Z. Zeying, J.
Chem. Soc., Dalton Trans. 1988, 2187.
[6] a) M. Sigl, A. Schier, H. Schmidbaur, Eur. J. Inorg.
Chem. 1998, 203;
[4] a) T.-P. Loh, J. Pei, G.-Q. Cao, J. Chem. Soc., Chem.
Commun. 1996, 1819;
b) T.-P. Loh, J. Pei, M. Lin, J. Chem. Soc., Chem.
Commun. 1996, 2315;
b) M. Sigl, A. Schier, H. Schmidbaur, Z. Natur-
forsch. 53b, (1998) submitted;
c) H. Schmidbaur, W. Findeiß, Chem. Ber. 99, 2187
c) M. Sigl, A. Schier, H. Schmidbaur, Z. Natur-
forsch. 53b, (1998) submitted.
[7] M. Preisenberger, A. Bauer, H. Schmidbaur, Chem.
Ber. 130, 955 (1997).
(1966);
d) M. G. Voronkov, S. U. Basenko, Zh. Obshch.
Khim. 65, 1482(1995).
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