Unusual inorganic ring systems of scandium and yttrium containing group 13 metals: Coordination of monomeric Me2InOMe to yttrium

Article abstract of DOI:10.1021/ic701909m

Novel transformations of lanthanide(III) disiloxanediolates with group 13 metal trialkyls are reported. Treatment of the scandium metallacrown complex [{(Ph₂SiO)₂O}₂{Li(DME)}₂] ScCl·THF (1) with AlMe₃

Full text of DOI:10.1021/ic701909m

Inorg. Chem. 2007, 46, 10956−10958
Unusual Inorganic Ring Systems of Scandium and Yttrium Containing
Group 13 Metals: Coordination of Monomeric Me2InOMe to Yttrium†
Stephan Giessmann, Steffen Blaurock, Volker Lorenz, and Frank T. Edelmann*
Chemisches Institut der Otto-Von-Guericke-UniVersita¨t Magdeburg, UniVersita¨tsplatz 2,
D-39106 Magdeburg, Germany
Received September 27, 2007
Novel transformations of lanthanide(III) disiloxanediolates with group
13 metal trialkyls are reported. Treatment of the scandium
neous catalysts1,4 or are catalytically active themselves.5 A
particularly useful ligand in this field is the tetraphenyl-
disiloxanediolate dianion [(Ph2SiO)2O]2-, which gives rise
to a variety of unusual and unexpected structures especially
when combined with alkali metals6 and early transition
metals.2b,6,7 The starting material tetraphenyldisiloxanediol,
Ph2Si(OH)OSiPh2(OH), is readily accessible from cheap
precursors.8 Soluble aluminosiloxanes have become increas-
ingly important in recent years,9 and some exciting chemistry
has been developed by Veith and co-workers around the
polycyclic aluminum tetraphenyldisiloxanediolate derivative
[Ph2SiO]8[AlO(OH)]4.10 A rare example of an indium disi-
loxanediolate, [{(Ph2SiO)2O}2InMe{µ-Li(THF)2}2], was pre-
pared from Ph2Si(OH)OSiPh2(OH) and Li[InMe4].11 Group
3 metal (Sc/Y) and lanthanide complexes containing the
[(Ph2SiO)2O]2- ligand have been investigated in our labora-
tory.12 It was discovered that the small Sc3+ and Y3+ ions
form heterobimetallic complexes in which the group 3 metal
metallacrown complex [
with AlMe3 resulted in an Li
of the heterotrimetallic inorganic ring system [
(THF)2 AlMe2]ScCl THF (2). The related yttrium metallacrown
(Ph2SiO)2O}2{Li(THF)2 2]YCl THF (3) reacts with InMe3 under
the formation of the heterobimetallic Y/In disiloxanediolate complex
(Ph2SiO)2O}2{InMe2(OMe) 2InMe2]Y (4). In the latter, two mono-
{
(Ph2SiO)2O}2{Li(DME)
Al exchange reaction and the formation
(Ph2SiO)2O}2{Li-
}2]ScCl‚THF (1)
−
{
}
‚
[
{
}
‚
[{
}
meric Me2InOMe ligands are stabilized through coordination to
yttrium.
The chemistry of metallasiloxanes derived from silane-
diols, disiloxanediols, and related Si-OH species continues
to be an area of vigorous research activities1-7 because such
compounds are valuable precursors for metal oxides and
silicates2,3 as well as models for silica-supported heteroge-
† Dedicated to Professor Ken Wade on the occasion of his 75th birthday.
* To whom correspondence should be addressed. E-mail:
frank.edelmann@ovgu.de.
(1) Reviews: (a) Murugavel, R.; Voigt, A.; Walawalkar, M. G.; Roesky,
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Giessmann, S.; Gilje, J. W.; Gun’ko, Yu. K.; Jacob, K.; Edelmann, F.
T. Coord. Chem. ReV. 2000, 206-207, 321-368. (c) Duchateau, R.
Chem. ReV. 2002, 102, 3525-3542.
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1989, 1, 199-201. (b) Lazell, M.; Motevalli, M.; Shah, S. A. A.;
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1991, 1, 143-144. (b) Gunji, T.; Kubota, K.-I.; Kishiki, S.-I.; Abe,
Y. Bull. Chem. Soc. Jpn. 2002, 75, 537-543. (c) Gadda, T. M.; Weber,
W. P. Polym. Prepr. (Am. Chem. Soc.. DiV. Polym. Chem.) 2005, 46,
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(4) (a) Yermakov, Y. I.; Kuznetsov, B. N.; Zakharov, V. A. Catalysis by
Supported Complexes; Elsevier: New York, 1981. (b) Hartley, F. R.
Supported Metal Complexes; Reidel: Boston, MA, 1985. (c) Iwasawa,
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Edelmann, F. T. Angew. Chem. 1992, 104, 600-601; Angew. Chem.,
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(6) (a) Motevalli, M.; Shah, D.; Sullivan, A. C. J. Chem. Soc., Dalton
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Motevalli, M.; Sanganee, M.; Sullivan, A. C. J. Organomet. Chem.
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Sullivan, A. C. J. Chem. Soc., Dalton Trans. 1989, 2347-2352. (b)
Motevalli, M.; Shah, D.; Shah, S. A. A.; Sullivan, A. C. J. Chem.
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M.; Shah, S. A. A.; Simon, C. K. S.; Sullivan, A. C. J. Chem. Soc.,
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Angew. Chem. 1995, 107, 2761-2763; Angew. Chem., Int. Ed. Engl.
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10956 Inorganic Chemistry, Vol. 46, No. 26, 2007
10.1021/ic701909m CCC: $37.00
© 2007 American Chemical Society
Published on Web 11/17/2007

COMMUNICATION
Scheme 1
is located in the center of an inorganic ring system formed
by two lithium disiloxanediolate units. Additional chloro
functions and solvent molecules are arranged in the trans
positions. Thus, these complexes can be regarded as metal-
lacrown derivatives of scandium and yttrium. We report here
the initial results of reactions of these species with group 13
metal trialkyls, leading to the formation of unusual inorganic
ring systems containing two (Y/In) or three (Sc/Al/Li)
different metal atoms.
Figure 1. Molecular structure of [{(Ph2SiO)2O}2{Li(THF)2}AlMe2]ScCl‚
THF (2). Selected bond lengths (Å) and angles (deg): Sc-O1 2.186(3),
Sc-O3 2.018(3), Sc-O4 2.019(3), Sc-O6 2.182(3), Sc-O7 2.271(3), Sc-
Cl 2.434(1), Al-O1 1.837(3), Al-O6 1.836(3), Li-O4 2.023(9), Li-O3
2.036(9), O1-Sc-O6 73.3(1), O3-Sc-O4 90.3(1), O1-Al-O6 90.4 (1),
O3-Li-O4 89.6(3), C1-Al-C2 117.6(2), O(THF)-Li-O(THF) 105.7-
(4), O1-Sc-O3 98.6(1), O4-Sc-O6 96.6(1), O7-Sc-Cl 175.1(1),
O3-Sc-O6 168.8(1), O4-Sc-O1 166.8(1).
Treatment of the scandium complex 112c (Scheme 1) with
an excess of trimethylaluminum in toluene afforded a
colorless solution, from which colorless, block-shaped single
crystals could be isolated in 50% yield.13 This reaction was
initially performed with the aim of replacing the chloro ligand
in the trans position by a methyl group. However, an X-ray
crystal structure determination14 revealed the presence of a
unique heterotrimetallic (Sc/Al/Li) disiloxanediolate complex
2, as illustrated in Scheme 1.
The most surprising result of this reaction was the
replacement of one Li(DME)+ unit in 1 by an AlMe2+ moiety
under retention of the chloro function in the trans position.
Despite the use of an excess of AlMe3, only one lithium
was replaced. The fate of the latter, however, is not clear. If
a stoichiometric amount of methyllithium is formed in the
course of this reaction, it could add to AlMe3 to form
LiAlMe4,15 a reaction that would account for the fairly low
isolated yield of 2. Another plausible reaction pathway would
involve the formation of a MeLi-DME adduct, which
has been reported to exhibit reduced reactivity and solubil-
ity.16 Like the starting material 1, the trimetallic product
2 also adopts the metallacrown form with the central Sc3+
ion accommodated well within the plane of the slightly
puckered inorganic ring system (Figure 1). As in the starting
material 1, one THF ligand and the chloride ion occupy
the trans positions. Figure 1 also clearly shows how the
central metallacrown core is efficiently shielded by eight
phenyl substituents and three coordinated THF molecules,
which accounts for the high solubility of the complex in
toluene.
A similar reaction carried out with the yttrium metalla-
crown precursor 3 and an excess of trimethylindium took
an entirely different course. In this case, colorless prism-
shaped crystals were isolated in 81% yield by slow concen-
tration of the filtered reaction mixture.17 An 1H NMR
spectrum of the product indicated the incorporation of three
(13) Preparation of 2: A total of 0.36 g (0.30 mmol) of [{(Ph2SiO)2O}2-
{Li(DME)}2]ScCl‚THF (1) was dissolved in 10 mL of THF. To the
clear, colorless solution was added 0.06 g (0.83 mmol) of neat AlMe3
via syringe under vigorous stirring at ambient temperature, and stirring
was continued for 30 min. Slow concentration of the solution in the
drybox afforded colorless, block-shaped crystals suitable for X-ray
diffraction. Yield: 0.20 g (50%). Mp: 154 °C (dec). Anal. Calcd for
C70H86AlClLiO11ScSi4 (Mr ) 1330.08): C, 63.21; H, 6.52. Found:
(15) (a) Karsch, H. H.; Appelt, A.; Mu¨ller, G. Organometallics 1985, 4,
1624-1632. (b) Fryzuk, M. D.; Giesbrecht, G. R.; Rettig, S. J.
Organometallics 1997, 16, 725-736. (c) Bo¨ttcher, P.; Roesky, H. W.;
Walawalkar, M. G.; Schmidt, H.-G. Organometallics 2001, 20, 790-
793.
1
C, 62.70; H, 6.46. H NMR (400.1 MHz, THF-d8, 20 °C): δ 8.04-
6.77 (m, 40H, Ph), 3.53 (4H, THF), 1.67 (4H, THF), -1.01 (6H,
AlMe). 13C NMR (100.6 MHz, THF-d8, 20 °C): δ 140.03 (ipso-C,
Ph), 135.80, 134.80, 129.59, 127.97 (Ph), 127.23 (br m), 68.12 (THF),
26.27 (THF). 29Si NMR (79.5 MHz, THF-d8, 20 °C): δ -42.8. IR
(KBr): 3437, 3069, 3049, 3001, 2978, 2930, 2888, 1592, 1568, 1488,
1460, 1429, 1370, 1307, 1244, 1183, 1124, 1116, 1050, 1026, 997,
(16) Walfort, B.; Lameyer, L.; Weiss, W.; Herbst-Irmer, R.; Bertermann,
R.; Rocha, J.; Stalke, D. Chem.sEur. J. 2001, 7, 1417-1423.
(17) Preparation of 4: Toluene (30 mL) was added to a dry mixture of
0.54 g (0.41 mmol) of [{(Ph2SiO)2O}2{Li(THF)2}2]YCl‚THF (3) and
0.13 g (0.81 mmol) of InMe3. The resulting yellowish suspension
was stirred for 60 h at ambient temperature and for an additional
4 h at reflux temperature. Filtration through a thin layer of Celite
resulted in a clear yellow solution. Slow concentration of the filtrate
inside the drybox afforded colorless prisms suitable for X-ray
diffraction. Yield: 0.47 g (81%). Mp: 106 °C (dec). Anal. Calcd for
C56H64In3O8Si4Y (Mr ) 1410.80): C, 47.68; H, 4.57. Found: C, 46.88;
930, 873, 744, 717, 701, 678, 620, 571, 523, 490, 450 cm-1
.
(14) Data collection for 2: C70H86AlClLiO11ScSi4, Mr ) 1330.08, crystal
dimensions 0.40 × 0.20 × 0.20 mm3, monoclinic (C2/c), a ) 28.680-
(6) Å, b ) 22.212(4) Å, c ) 25.817(5) Å, â ) 117.09(3)°, V ) 14643-
(5) Å3, Z ) 8, Fcalcd ) 1.207 g mm-3, µ ) 0.269 mm-1, Mo KR
radiation, λ ) 0.710 73 Å, T ) 180(2) K, reflections measured )
62 950, unique reflections ) 19 787 (Rint ) 0.1505), absorption
correction ) spherical, final R indices R1 ) 0.0597 and wR2 )
0.1460, largest difference peak and hole ) +1.583 and -0.352 e Å-3
.
H, 4.51. H NMR (400.1 MHz, C6D6, 20 °C): δ 8.50-6.50 (m, Ph,
1
Data collection for 4: C56H64In3O8Si4Y, Mr ) 1410.80, crystal
dimensions 0.40 × 0.30 × 0.20 mm3, monoclinic (C2/c), a ) 19.832-
(4) Å, b ) 12.054(2) Å, c ) 26.508(5) Å, â ) 103.29(3)°, V ) 6167-
(2) Å3, Z ) 4, Fcalcd ) 1.520 g mm-3, µ ) 2.165 mm-1, Mo KR
radiation, λ ) 0.710 73 Å, T ) 173(2) K, reflections measured )
37 383, unique reflections ) 8332 (Rint ) 0.0969), absorption
correction ) none, final R indices R1 ) 0.0465 and wR2 ) 0.1107,
40H), 2.10 (s, OMe, 6H), -0.01 (d, InMe, 12 H), -0.43 (d, InMe,
6H). 13C NMR (100.6 MHz, C6D6, 20 °C): δ 137.65-136.76 (m, Ph,
ipso-C), 136.16, 135.12, 134.90, 130.76-130.16 (m), 129.29-127.54
(m, Ph), 21.38 (OMe), -1.73, -4.96 (InMe). 29Si NMR (79.5 MHz,
C6D6, 20 °C): δ -34.67, -35.34. IR (KBr): 3437, 3069, 3050,
3001, 2923, 2811, 159 1, 1568, 1486, 1450, 1429, 1385, 1306, 1252,
1182, 1123, 1058, 1035, 1018, 996, 921, 743, 716, 700, 533, 493,
largest difference peak and hole ) +1.435 and -1.440 e Å-3
.
478, 428 cm-1
.
Inorganic Chemistry, Vol. 46, No. 26, 2007 10957

COMMUNICATION
crown ring system, while the other two were converted into
Me2InOMe ligands, probably through methylation of a
siloxide oxygen during the course of the reaction. However,
the latter assumption is purely speculative at this stage, and
clearly more work is needed in order to gain more insight
into the reaction pathways leading to the novel complexes 3
and 4.
The significantly lower solubility of 4 in toluene as
compared to 2 can be traced back to the much less effective
shielding of the “inorganic” metallacrown core by phenyl
substituents. The most remarkable structural feature of 4,
however, is the complex stabilization of two monomeric
Me2InOMe ligands. Free liquid dimethylindium methoxide
was first reported by Coates and co-workers18 in 1956 and
later shown by Weidlein and co-workers19 to have a trimeric
In3O3 ring structure. In 4, two monomeric Me2InOMe units
are stabilized through interaction with disiloxanediolate
oxygens and coordination of the methoxy groups to yttrium.
In summary, transformations of heterobimetallic group 3
metal disiloxandiolates with trialkyls of aluminum and
indium have been shown to yield novel bi- or trimetallic
inorganic ring systems. The Sc/Al/Li complex 2 was formed
via an unexpected Li-Al exchange reaction. Complex
stabilization of monomeric Me2InOMe was observed in the
novel Y/In disiloxanediolate derivative 4. The two initial
reactions reported here were selected in order to get a first
impression of the scope of this chemistry. Given the large
variety of potential precursors, it can be readily anticipated
that further research in this area will produce many more
surprising and exciting results in the future.
Figure 2. Molecular structure of [{(Ph2SiO)2O}2{InMe2(OMe)}2InMe2]Y
(4). Selected bond lengths (Å) and angles (deg): Y-O1 2.290(3), Y-O3
2.277(3), Y-O4 2.223(3), In1-O3 2.208(3), In2-O4 2.161(3), In2-O1#
2.211(3), O4-Y1-O4# 101.39(16), O3-Y1-O1# 115.88(9), O4-Y1-
O3 97.81(11), O4-Y1-O1# 74.56(11), O4#-Y1-O3 151.07(10), O3-
Y1-O1, 84.01(10), O4-Y1-O1 90.15(11), O1#-Y1-O1 155.98(14), O3-
Y1-O3# 74.10(13), C25#-In1-C25 138.8(4), O3-In1-O3# 76.85(14),
C28-In2-C27 137.8(2), O4-In2-O1# 77.40(11), In1-O3-Y1 104.52-
(11), In2-O4-Y1 104.51(14), In2#-O1-Y1 100.74(12) (# denotes
symmetry-related atoms).
Scheme 2
Acknowledgment. This work was generously supported
by the Deutsche Forschungsgemeinschaft (SPP 1166
“Lanthanoid-spezifische Funktionalita¨ten in Moleku¨l und
Material”).
InMe2 units in two different ways (the intensity ratio of the
InCH3 resonances was 2:1) and replacement of all coordi-
nated THF. Again, unequivocal structural characterization
proved to be possible only with the aid of an X-ray diffrac-
tion study,14 which revealed the formation of a novel
inorganic ring system 4 containing both yttrium and indium
(Scheme 2).
Supporting Information Available: ORTEP drawings and
X-ray structural data as well as complete CIF files for 3 and 4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
In the molecular structure of 4 (Figure 2), the central
yttrium is coordinated by six oxygen atoms in a slightly
distorted octahedral fashion. The crystal structure analysis
IC701909M
(18) Coates, G. E.; Whitcombe, R. A. J. Chem. Soc. 1956, 3351-3354.
(19) Mann, G.; Olapinski, H.; Ott, R.; Weidlein, J. Z. Anorg. Allg. Chem.
1974, 410, 195-205.
+
confirmed the incorporation of three InMe2 moieties. One
+
of them had replaced a Li(THF)2 unit within the metalla-
10958 Inorganic Chemistry, Vol. 46, No. 26, 2007