AgOC(CF3)3 and AgOSiiPr3 - Synthesis and characterization of a donor-free silver(I) alkoxide and silyl oxide

Article abstract of DOI:10.1002/anie.200600805

Over 30 years after the first successful syntheses of Cu^I alkoxides and silyl oxides, the first homologous Ag^I compounds were synthesized and characterized (see scheme). AgOC(CF₃)₃ was furthermore found to be a promising precursor for chemical vapor deposition processes and the deposition of AgF (Chemical Equation Presented).

Full text of DOI:10.1002/anie.200600805

Angewandte
Chemie
CuMes þ HOR ! CuOR þ MesH
ð1Þ
Silver Alkoxides and Silyl Oxides
contrast, the syntheses of the homologous silver compounds
in this work were performed by metathesis of the respective
DOI: 10.1002/anie.200600805
AgOC(CF ) and AgOSiiPr —Synthesis and
alkaline metal alkoxide LiOC(CF
and a suitable silver(I) salt. The solids were mixed in a glove
box and suspended in CH Cl with exclusion of light. Initially,
3
) or silyl oxide NaOSiiPr
3
3
3
3
3
Characterization of a Donor-Free Silver(I)
Alkoxide and Silyl Oxide**
2
2
the synthesis of the alkoxide was attempted using relatively
inexpensive AgF. However, no reaction was observed at first,
and only upon treatment in an ultrasonic bath at 508C
overnight, the suspension turned dark brown. After filtration
and removal of the solvent, three to five very small crystals
remained. The crystals were identified as the desired product,
but with a very poor yield of less than 1%. Therefore,
Andreas Reisinger, Daniel Himmel, and Ingo Krossing*
Transition-metal alkoxides and silyl oxides are important
synthons in organometallic synthesis as well as precursors for
[
1]
electronic or ceramic materials. However, information on
the structures and properties of donor-free coinage metal(I)
alkoxides and silyl oxides is still sparse and so far limited to
insoluble AgF was replaced by the more soluble AgBF , and
4
[
18]
[19]
the desired products AgOC(CF ) (1) and AgOSiiPr (2)
3
3
3
[
2–8]
I
were formed in good yields after stirring at room temperature
Eq. (2)].
Cu.
Several of these homoleptic Cu alkoxides and silyl
[
oxides were successfully tested for chemical vapor deposition
[
6,9]
I
(
CVD) processes.
Of the Cu alkoxides and silyl oxides,
CH2Cl2
MOR þ AgBF ƒƒ ƒƒ !AgOR þ MBF M ¼ Li or Na
4
4
only CuOCR and CuOSiR (R = CH and C H ) have been
3
3
4–8]
3
6
5
ð2Þ
[
R ¼ CðCF Þ or SiiPr
3
3
3
structurally characterized.
In all cases, the compounds are
tetranuclear species and form approximately square-planar
eight-membered rings in the solid state. Such square-planar
ring structures have also been observed for Cu and Ag silyl
After filtration and concentration of the filtrate, large
amounts of colorless and light-sensitive 1·0.5CH Cl and 2
2
2
[
10]
amides. However, when donors such as CO, alkenes, or
phosphanes were supplied, the ring structure was lost and,
depending on the R group and the donor molecule, hetero-
crystallized in the cooled filtrate and were characterized by
NMR, IR, Raman spectroscopy, and X-ray crystallogra-
[
18,19]
phy.
The alkoxide 1 crystallized from the CH Cl solution
2 2
[
11,12]
cubane-type aggregates
or dinuclear four-membered ring
as a weakly bound hemisolvate while the silyl oxide 2
[
7,12,13]
[20]
structures were formed. Monomeric and dimeric phos-
phane-stabilized Au alkoxides
crystallized solvent-free.
Solvent-free crystals of 1 were
I
[14]
[2]
and silyl oxides with
obtained by complete evaporation of the solvent and
ꢀ2
aurophilic interactions are also known, but have not been
structurally characterized.
subsequent sublimation at 1308C and 10 mbar. Under the
same conditions, 2 decomposed with formation of a silver
mirror.
Although donor-free copper(I) alkoxides and silyl oxides
[
3]
have been known for a long time, no homologous com-
pounds with silver or gold have been reported, with the
The successful sublimation of 1 indicates that applications
as precursors for CVD processes should be possible. A
thermogravimetric analysis of 1 indicated that the alkoxides
decompose upon heating with separation of the volatile
[
2,15]
exception of two phosphane adducts.
However, homo-
I
leptic Ag alkoxides and silyl oxides might, analogously to the
copper compounds, be versatile reagents in organometallic
synthesis. For example, such alkoxides and silyl oxides could
be useful reagents for the synthesis of new weakly coordinat-
ing anions that complement the known alkoxy aluminates of
[
21,22]
[23]
epoxide C F O
and solid AgF. The formation of C F O
4 8
4
8
was verified by an independent decomposition experiment
and gas-phase IR analysis of the volatiles formed. Since the
solvent-free silver alkoxide is light-sensitive, it is best stored
as its hemisolvate and wrapped in aluminum foil in a freezer
at ꢀ208C. With these precautions the compound is stable over
months. Without these precautions, compound 1 turns brown
within 30 minutes and completely black over night. The silyl
oxide is also light-sensitive, but can be stored in the dark for
several hours at room temperature without decomposition.
For longer storage, it should also be kept at ꢀ208C.
F
ꢀ
F
[16]
the type [Al(OR ) ] (R = fluorinated alkyl or aryl group).
4
In recent years, these compounds have been widely and very
[
17]
successfully used in our group. Furthermore, they might be
promising precursors for Ag CVD processes, since only few
volatile Ag compounds are currently known.
I
Most Cu alkoxides and silyl oxides were synthesized by
the reaction of mesitylcopper (CuMes) with the respective
alcohol or silanol and elimination of MesH [Eq. (1)]. By
[
24,25]
In the solid state,
the dominating structural element
of 2 also consists of a square-planar centrosymmetric eight-
membered (AgO) ring with O-Ag-O angles close to 1808
4
[
*] A. Reisinger, Dr. D. Himmel, Prof. I. Krossing
Institut für Anorganische und Analytische Chemie
Albert-Ludwigs-Universität
(
av. 173.18) and Ag-O-Ag angles close to 908 (av. 96.58;
Figure 1).
Unlike the Cu structures and the silyl oxide 2,
[4,7,8]
the
79104 Freiburg (Deutschland)
alkoxide 1 does not form isolated square-planar rings, rather a
one-dimensional polymeric structure built from distorted
eight-membered rings that are connected through rectangular
Fax: (+49)761/203-6001
E-mail: krossing@uni-freiburg.de
[
**] This work was supported by the Deutsche Forschungsgemeinschaft,
the Schweizer Nationalfonds, the EPFL, and the University of
Freiburg.
[
24,26]
four-membered rings (Figure 2).
Within the eight-mem-
bered rings the averaged AgꢀO bonds (221.2 pm) are
Angew. Chem. Int. Ed. 2006, 45, 6997 –7000
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6997

Communications
Figure 1. Sections of the solid-state structure of 2. Thermal ellipsoids
are drawn at the 50% probability level. Bond lengths are given in pm.
elongated by 13.3 pm compared to those of the silyl oxide
(
207.9 pm). However, the elongation is more pronounced for
Figure 2. Sections of the solid-state structure of 1: eight-membered
the silver centers with T-shaped geometry (221.1 and
ring (left) and polymeric ring structure (right, CF groups omitted for
3
2
2
32.5 pm) than for the ones with linear geometry (213.5 and
17.7 pm; Figure 2). This difference is accompanied by longer
clarity). Thermal ellipsoids are drawn at the 50% probability level.
Bond lengths are given in pm.
ring-connecting AgꢀO bonds (249.4 pm), which are shorter
than the CuꢀO bonds of the related CuOtBu structure
(
251.5 pm). Accordingly, the O-Ag-O and Ag-O-Ag angles
interesting and potentially useful compounds. Because of
deviate from the ideal values of 1808 and 908 (162.58 and
their facile preparation, 1 and 2 are attractive reagents for
1
00.68, Table 1).
The synthesis and full characterization of the silver
CVD processes or syntheses including new alkoxy or siloxy
F
metalates by reaction with Lewis acids M(OR ) or elemental
n
alkoxide AgOC(CF3)3 and the silyl oxide AgOSiiPr give
halides such as SbCl . A more complete discussion of the
3
5
the first structural information on these basic, but very
spectroscopic data, additional quantum chemical calculations
on the formation and stability of both compounds, as well as
first applications are in progress.
[
20]
Table 1: Selected average bond lengths d [pm] and angles a [8] of 1 and
[
8]
[5]
2
compared to those in CuOtBu and CuOSi(CH ) .
3 3
CuOtBu
1
CuOSi(CH3)3
2
Experimental Section
All manipulations were performed using grease-free Schlenk or
d1(M-O)
d2(M-O)
dcov(M-O)
d(O-(C/Si))
a(O-M-O)
a(M-O-M)
181.2
251.5
183
145.6
175.6
93.6
221.2
249.4
200
138.4
162.5
100.6
184.4
–
183
163.8
175.8
93.9
207.9
–
200
163.6
173.1
96.5
glove-box techniques and a dinitrogen atmosphere (H O and O <
2
2
1
ppm). CH Cl was rigorously dried by multiple additions of 20-g
[
a]
2 2
quantities of P O and subsequent distillation and degassing prior to
2
5
use. Solvents were added by condensation techniques. NMR spectra
were recorded in CD Cl at room temperature on a BRUKER
2
2
AVANCE 400 spectrometer, and data are given in ppm relative to the
1
13
27
19
[
a] dcov =sum of covalent radii.
solvent signals ( H, C), aqueous AlCl ( Al), and CFCl ( F). IR
3
3
6
998 www.angewandte.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2006, 45, 6997 –7000

Angewandte
Chemie
spectra were obtained as a nujol mull between CsIplates on a
BRUKER VERTEX 70 IR spectrometer. Raman spectra were
recorded on a BRUKER RAM II Raman module using a liquid-
nitrogen-cooled, highly sensitive Ge detector. Single-crystal structure
determinations were carried out on a BRUKER KAPPA APEX II
diffractometer using graphite-monochromated MoKa radiation.
[18] LiOC(CF3)3 (1.35 g, 5.136 mmol) and AgBF4 (1.00 g,
5.137 mmol) were mixed in a glove box and weighed into one
side of a two-bulb frit-plate flask with a glass stem that was
closed with two greaseless YOUNG valves and wrapped in
aluminum foil to exclude light. The mixture was suspended in
CH Cl (ca. 30 mL) and stirred overnight at room temperature.
2
2
The next day, the solution was filtered, and all solvent was
removed. The resulting white product was dried quickly (max.
15 min) in vacuo since drying over a longer period (1 h) already
caused decomposition, most probably because of exposure to
light. Single crystals were obtained by sublimation at about
Received: March 1, 2006
Published online: September 22, 2006
Keywords: fluorinated ligands · silver · structure elucidation
ꢀ2
.
1
4
308C and 10 mbar. Yield of isolated product: 1.71 g,
X-ray diffraction
1
3
1
.437 mmol (86%). C{ H} NMR (63 MHz): d = 82.0 (dez,
2
1
19
JCF = 26.9 Hz), 122.9 ppm (q, JCF = 293.3 Hz);
F NMR
(
(
376 MHz): d = ꢀ75.94 ppm (s); IR (CsI plates, nujol): n˜ = 405
[
1] L. G. Hubert-Pfalzgraf, Coord. Chem. Rev. 1998, 178–180, 967;
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(
2
s), 1303 (ms), 1377 (ms), 1460 (s), 2726 (w), 2850 (vs), 2900 (vs),
947 cm (vs); Raman: n˜ = 108 (mw), 168 (w), 220 (mw), 300
S. Weidner, K. Kunze, D. Kaefer, J. Hans, V. Huch, Coord. Chem.
Rev. 1994, 137, 297.
ꢀ1
(
(
m), 329 (m), 361 (w), 506 (vw), 539 (m), 573 (vw), 680 (w), 726
vw), 770 (ms), 806 (vw), 984 (w), 1008 (vw), 1114 (vw), 1165 (w),
[
2] H. Schmidbaur, J. Adlkofer, A. Shiotani, Chem. Ber. 1972, 105,
3
389.
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58.
1
2
240 (vw), 1262 (vw), 1290 (vw), 1315 (m), 2757 (m), 2845 (vw),
909 (m), 2937 cm (m).
[
ꢀ1
9
[
19] NaOSiiPr (392 mg, 2.00 mmol) and AgBF (395 mg, 2.03 mmol)
3
4
[
[
4] T. Greiser, E. Weiss, Chem. Ber. 1976, 109, 3142.
5] M. J. McGeary, R. C. Wedlich, P. S. Coan, K. Folting, K. G.
Caulton, Polyhedron 1992, 11, 2459.
were mixed in a glove box and weighed into one side of a two-
bulb frit-plate flask with a glass stem that was closed with two
greaseless YOUNG valves and wrapped in aluminum foil to
exclude light. The mixture was suspended in CH Cl (20 mL) and
[
6] K. W. Terry, C. G. Lugmair, P. K. Gantzel, T. D. Tilley, Chem.
Mater. 1996, 8, 274.
2
2
stirred for 1 hour at room temperature in the dark. The solution
was filtered, and all solvent was removed. Yield of isolated
[
[
7] C. Lopes, M. Hakansson, S. Jagner, Inorg. Chem. 1997, 36, 3232.
8] M. Hakansson, C. Lopes, S. Jagner, Inorg. Chim. Acta 2000, 304,
1
product: 368 mg, 1.31 mmol (65%). H NMR (400 MHz): d =
178.
3
3
0
.97 (d, JHH = 7.2 Hz), 0.81 ppm (sept, JHH = 7.2 Hz);
[
9] I. J. Drake, K. L. Fujdala, S. Baxamusa, A. T. Bell, T. D. Tilley, J.
Phys. Chem. B 2004, 108, 18421; K. L. Fujdala, I. J. Drake, A. T.
Bell, T. D. Tilley, J. Am. Chem. Soc. 2004, 126, 10864; P. M.
Jeffries, G. S. Girolami, Chem. Mater. 1989, 1, 8.
1
3
1
C{ H} NMR (63 MHz): d = 19.8 (s), 15.0 ppm (s); IR (CsI
plates): n˜ = 409 (w), 466 (w), 511 (m), 657 (vs), 878 (m), 952 (vs),
9
2
91 (m), 1070 (m), 1156 (vw), 1237 (s), 1361 (s), 1377 (s), 1462 (s),
717 (vw), 2858 (vs), 2929 cm (vs).
ꢀ1
[
10] M. Veith, K. L. Woll, Chem. Ber. 1993, 126, 2383.
[
[
20] A. Reisinger, I. Krossing, unpublished results; a detailed
discussion of the solvent-containing structure will take place in
an upcoming full paper.
[
11] R. L. Geerts, J. C. Huffman, K. Folting, T. H. Lemmen, K. G.
Caulton, J. Am. Chem. Soc. 1983, 105, 3503; M. Hakansson, C.
Lopes, S. Jagner, Organometallics 1998, 17, 210.
21] The silver alkoxide was decomposed, and the volatile fragments
were characterized by IR spectroscopy. Comparison of the
[
[
[
12] C. Lopes, M. Hakansson, S. Jagner, Inorg. Chim. Acta 1997, 254,
361.
[
22]
observed bands with those of C F O shows a very good overall
4
8
13] T. H. Lemmen, G. V. Goeden, J. C. Huffman, R. L. Geerts, K. G.
Caulton, Inorg. Chem. 1990, 29, 3680.
14] B. R. Sutherland, K. Folting, W. E. Streib, D. M. Ho, J. C.
Huffman, K. G. Caulton, J. Am. Chem. Soc. 1987, 109, 3489; S.
Komiya, M. Iwata, T. Sone, A. Fukuoka, J. Chem. Soc. Chem.
Commun. 1992, 1109.
agreement: n˜ = 720 (w), 799 (m), 984 (m), 1027 (s), 1092 (s), 1202
ꢀ
1
(
mw), 1225 (w), 1262 (m), 1289 (w), 1316 (w), 1339 cm (w).
[
[
22] J. T. Hill, J. Fluorine Chem. 1977, 9, 97.
23] The differential temperature analysis measurements were per-
formed with a NETZSCH STA 429 DSC/DTA unit. About
20 mg of 1 was used for the experiment; preparation of the
[
15] D. A. Edwards, R. M. Harker, M. F. Mahon, K. C. Molloy, J.
Chem. Soc. Dalton Trans. 1997, 3509.
measurement and weighing were done in a glove box. The DTA
ꢀ1
curves were recorded at a heating rate of 5 Kmin . During the
heating period no distinct steps could be observed, but there was
a continuous loss of mass between 110 and 2408C. The dark
brownish-black residue had approximately 39% of its original
weight. This weight fits best for the formation of the gaseous
[
16] T. J. Barbarich, S. T. Handy, S. M. Miller, O. P. Anderson, P. A.
Grieco, S. H. Strauss, Organometallics 1996, 15, 3776; S. M.
Ivanova, B. G. Nolan, Y. Kobayashi, S. M. Miller, O. P. Ander-
son, S. H. Strauss, Chem. Eur. J. 2001, 7, 503; I. Krossing, H.
Brands, R. Feuerhake, S. Koenig, J. Fluorine Chem. 2001, 112,
epoxide C F O (63%) and solid AgF (37%). Formation of either
8
3; I. Krossing, Chem. Eur. J. 2001, 7, 490; I. Krossing, I. Raabe,
Angew. Chem. 2004, 116, 2116; Angew. Chem. Int. Ed. 2004, 43,
066.
17] I. Krossing, A. Reisinger, Inorg. Chem. Focus II 2005, 65; I . [24] CCDC-299939 and CCDC-299940 contain the supplementary
4 8
Ag
O (33%) or Ag (31%) would be accompanied by a higher
2
2
mass loss and, therefore, seems unlikely.
[
Krossing, J. Am. Chem. Soc. 2001, 123, 4603; I. Krossing, I.
Raabe, Angew. Chem. 2001, 113, 4544; Angew. Chem. Int. Ed.
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Angew. Chem. 2003, 115, 5725; Angew. Chem. Int. Ed. 2003, 42,
[25] Crystal-structure determination of AgOSiiPr : BRUKER
3
KAPPA APEX II, graphite-monochromated MoKa radiation,
T= 100(2) K, 85655 reflections, Lorentz, polarization, and
ꢀ
1
numerical absorption corrections, m = 1.728 mm , direct meth-
ods with SHELXS-97 (G. M. Sheldrick, SHELXS-97, Program
for the Solution of Crystal Structures, Universität Göttingen,
5725; M. Gonsior, I. Krossing, L. Müller, I. Raabe, M. Jansen, L.
van Wüllen, Chem. Eur. J. 2002, 8, 4475.
Angew. Chem. Int. Ed. 2006, 45, 6997 –7000
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 6999

Communications
2
1
997), refinement against F with SHELXL-97(G. M. Sheldrick,
SHELXL-97, Program for the Refinement of Crystal Structures,
Universität Göttingen, 1997), orthorhombic, space group Pbca,
Z = 8, a = 1515.4(3), b = 1306.5(3), c = 2440.3(5) pm, V=
3
ꢀ1
4
.8314(17) nm , 1
= 1.546 gcm , 2qmax = 55.068, reflections:
calcd
85655 collected, 5530 unique (Rint = 0.0206), 18 restraints, 430
parameters, R1 = 0.0190, wR2 (all data) = 0.0404, GOF = 1.275.
[
26] Crystal-structure determination of AgOC(CF ) : BRUKER
3
3
KAPPA APEX II, graphite-monochromated MoKa radiation,
T= 100(2) K, 19041 reflections, Lorentz, polarization, and
ꢀ
1
numerical absorption corrections, m = 2.825 mm , direct meth-
2
ods with SHELXS-97, refinement against F with SHELXL-97,
¯
triclinic, space group P1, Z = 2, a = 681.08(14), b = 1012.2(2), c =
1
3
1
092.0(2) pm, a = 85.76(3), b = 89.62(3), g = 88.93(3)8, V=
3
ꢀ1
.9901(11) nm , 1
= 3.034 gcm , 2qmax = 61.248, reflections:
calcd
9041 collected, 4000 unique (Rint = 0.0475), 271 parameter,
R1 = 0.0352, wR2 (all data) = 0.0493, GOF = 1.133.
7000 www.angewandte.org
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Angew. Chem. Int. Ed. 2006, 45, 6997 –7000