close

Вход

Забыли?

вход по аккаунту

?

The УNoncoordinatingФ Anion Tf2N Coordinates to Yb2+ A Structurally Characterized Tf2N Complex from the Ionic Liquid [mppyr][Tf2N].

код для вставкиСкачать
Angewandte
Chemie
Structure Elucidation
DOI: 10.1002/anie.200501297
The “Noncoordinating” Anion Tf2N
Coordinates to Yb2+: A Structurally Characterized
Tf2N Complex from the Ionic Liquid
[mppyr][Tf2N]**
Anja-Verena Mudring,* Arash Babai, Sven Arenz, and
Ralf Giernoth
Crystal structures of bis(trifluoromethanesulfonyl)amide
(Tf2N) complexes of transition or f elements are unknown
to date. This is surprising, since a variety of bis(trifluoromethanesulfonyl)amide compounds have been identified to be
excellent Lewis acid catalysts. The Tf2N ion is the conjugate
base of an extremely strong Brønsted acid and has the power
to strengthen the Lewis acidity of a metal center when acting
as a ligand.[1] Lanthanide bis(trifluoromethanesulfonyl)amide
compounds are, for example, used as Lewis acid catalysts for
Diels–Alder reactions, Friedel–Crafts acylations, Fries transpositions, and Baeyer–Villinger oxidations.[2] Much effort
(although to no avail) has been put into the crystallization of
lanthanide bis(trifluoromethanesulfonyl)amides, but so far
the structural identity of these catalysts remains uncertain.[3]
Attempts to crystallize an ytterbium–Tf2N complex from
N,N’-dimethylpropyleneurea (dmpu)/ethyl acetate yielded a
crystal structure with YbIII ions surrounded octahedrally by
six dmpu ligands. The Tf2N ion was, however, only incorporated into this structure as a noncoordinating anion.[4] It is,
therefore, not surprising that the Tf2N ion has often been
considered as weakly or even noncoordinating. The Tf2N ion
shows the feature that is essential for an ion to have a low
tendency to coordinate: delocalization of negative charge
over an extended area of functional groups.[5] The extremely
strong acidity of the corresponding acid Tf2NH has been
attributed to extensive electron delocalization. As a conse-
quence, the term “gas-phase superacid” has been coined for
Tf2NH.[6]
The Tf2N ion has recently gained much attention in the
ongoing search for new room-temperature ionic liquids
(RTILs), since it has become clear that anions with diffuse
charges and negligible possibility to form hydrogen-bonding
interactions have the highest potential to produce ionic
compounds that are liquid at room temperature and below.[7]
RTILs have attracted wide attention as “green” solvents for
catalysis, chemical synthesis, and separations. They have
many favorable properties that are tuneable through the
choice of the cation/anion pair, such as negligible volatility,
high chemical, thermal and (electro)chemical stability, viscosity, density, hydrophobicity. The Tf2N ion has been found
to frequently produce salts with low melting points that have
high fluidity and high ionic conductivity.[8] Ionic liquids based
on the Tf2N ion have gained special attention as they
improve the performance of lithium batteries and fuel
cells.[9] Indeed, most crystal structures of ionic liquids with
the Tf2N ion reveal no substantial hydrogen bonding
between the cation and anion.[10] Displacement factors and
sometimes the tendency to disorder show that the anion is
conformationally highly flexibile, which might be the reason
for the low number of structure determinations containing the
Tf2N ion.[11]
In our ongoing studies to explore the reactivity of rareearth compounds as reagents for organic synthesis and
catalysis in ionic liquids we were able to structurally
characterize the first ytterbium–Tf2N complex. Here, we
present the first homoleptic Tf2N complex obtained by
interaction of YbI2 with the ionic liquid [mppyr][Tf2N]
(mppyr = 1-methyl-1-propylpyrrolidinium).[12]
The complex crystallizes in the monoclinic space group
P21/n with four formula units in the unit cell. The asymmetric
unit of the crystal structure shows YbII being coordinated by
four Tf2N ions through their oxygen atoms (Figure 1), with
two cations of the ionic liquid to balance the charge.[13] To our
knowledge, this is the first structure showing the Tf2N ion
coordinating in a h2-bidentate manner to a metal center to
form discrete anionic molecules. The Yb atom is surrounded
[*] Dr. A.-V. Mudring, Dipl.-Chem. A. Babai
Institut f4r Anorganische Chemie
Universit7t zu K:ln
Greinstrasse 6, 50939 K:ln (Germany)
Fax: (+ 49) 221-470-5083
E-mail: a.mudring@uni-koeln.de
Dipl.-Chem. S. Arenz, Dr. R. Giernoth
Institut f4r Organische Chemie
Universit7t zu K:ln
Greinstrasse 4, 50939 K:ln (Germany)
[**] This work has been supported by the Deutsche Forschungsgemeinschaft (SPP 1166 “Lanthanoidspezifische Funktionalit7ten”
and the Emmy Noether program (R.G.)) and by the Fonds der
Chemischen Industrie (Liebig-Stipendium (A.V.M.) and Sachmittel
(A.V.M. and R.G.)). We would especially like to thank Prof. Dr. G.
Meyer and Prof. Dr. A. Berkessel for their continuous support.
Tf = trifluoromethanesulfonyl, mpyr = 1-methyl-1-propylpyrrolidinium.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Angew. Chem. Int. Ed. 2005, 44, 5485 –5488
Figure 1. Asymmetric unit of the crystal structure of [mppyr]2[Yb(Tf2N)4]; blue: N, yellow: S, gray: C, green: F, orange: Yb, red: O.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5485
Communications
by eight oxygen atoms that form a distorted square antiprism
(Figure 1). The cations surround the anionic [Yb(Tf2N)4]2 units (d(N(5)-N(3)) = 473.3 pm, d(N(5)-N(4)) =
631.0 pm,
d(N(6)-N(1)) = 625.3 pm,
d(N(6)-N(2) =
453.4 pm) (Figure 1) and form a honeycomb-like structure.
The YbO bond lengths range from 241.0 to 251.7 pm, the
latter being to our knowledge the longest YbIIO bond so far
observed (Table 1). Bond lengths of 210–217 pm are found in
Table 1: Selected interatomic distances [pm] for [mppyr]2[Yb(Tf2N)4].
Yb(1)-O(1)
Yb(1)-O(2)
Yb(1)-O(5)
Yb(1)-O(6)
Yb(1)-O(9)
Yb(1)-O(10)
Yb(1)-O(13)
Yb(1)-O(14)
S(1)-N(1)
S(2)-N(1)
S(3)-N(2)
S(4)-N(2)
S(5)-N(3)
S(6)-N(3)
S(7)-N(4)
S(8)-N(4)
242.1(3)
247.6(3)
251.7(3)
243.5(3)
241.0(3)
247.0(3)
250.2(3)
245.6(3)
156.3(4)
156.4(4)
156.5(4)
156.7(4)
156.8(4)
155.8(4)
156.2(4)
156.8(4)
S(1)-O(1)
S(1)-O(3)
S(2)-O(2)
S(2)-O(4)
S(3)-O(5)
S(3)-O(7)
S(4)-O(6)
S(4)-O(8)
S(5)-O(9)
S(5)-O(11)
S(6)-O(10)
S(6)-O(12)
S(7)-O(13)
S(7)-O(15)
S(8)-O(14)
S(8)-O(16)
144.5(3)
142.1(4)
144.3(3)
141.9(3)
143.9(3)
142.0(3)
144.7(3)
140.5(4)
145.0(3)
141.6(3)
144.1(3)
141.5(4)
143.6(3)
141.7(3)
144.1(3)
141.8(4)
aryloxo–ytterbium complexes, while YbO bond lengths in
bridging aryloxo ligands lie in the range 224–234 pm.[14] YbO
bond lengths of 238–239 pm are reported for [Yb(thf)6]2+ with
neutral tetrahydrofuran as a ligand.[15] Unfortunately there
are no structural data for YbII–1,3-diketone complexes
available for comparison. Considering that the ionic radius
of an eightfold coordinate Yb2+ ion corresponds to the one for
an eightfold coordinate La3+ ion, it might be possible to
compare the average YbO bond length of 246.1 pm in
[mppyr]2[Yb(Tf2N)4] to d(La-O) of 247 found for [La(acac)3(H2O)2] (acac = acetylacetonate).[16]
Surprisingly, all the ligands show a cisoid conformation
with respect to the CF3 groups, which fixes the [Yb(Tf2N)4]2
antiprisms along the crystallographic b-axis (Figure 2). The
free acid Tf2NH crystallizes with the CF3 groups being
oriented in a transoid banner to each other.[17] The Tf2N ion
also prefers the transoid conformation in the absence of
suitable coordination centers.[10, 11] This observation is backed
by theoretical calculations (transoid Tf2NH is about
8 kJ mol1 more stable than cisoid Tf2NH, and transoid
Tf2N about 4 kJ mol1 more stable than cisoid Tf2N).[18] It
can thus be concluded that the cisoid conformation of the
Tf2N ion in [mppyr][Tf2N] results from by Yb–Tf2N interactions. The very weak interaction between the metal center
and the oxygen atoms results in the average SO bond lengths
[144.3 pm (coordinating oxygen atoms) and 141.6 pm (noncoordinating oxygen atoms)] being only slightly affected by
coordination to the Yb2+ ion, even when compared to the
neutral amine (d(S-O) = 140.1 pm and 141.7 pm).[17]
The question that arises is: why does the Tf2N ion
coordinate through its oxygen atoms and not through the
deprotonated nitrogen center? In this context, the often-cited
5486
www.angewandte.org
Figure 2. a) Space filling model of Tf2N as found in [mppyr]2[Yb(Tf2N)4]. b) Calculated electrostatic potential of cisoid Tf2N .
Cruickshank model predicts that charge delocalization in
these systems only occurs between the nitrogen and sulfur
atoms.[19] In contrast, Mulliken charges as well as natural
charges obtained from NBO analysis indicate that high partial
charges occur not only at the nitrogen center but also at the
oxygen atoms of the Tf2N ion (Table 2). This charge
Table 2: Mulliken charges and natural charges for cisoid Tf2N at the MP2
and B3LYP level of theory.
Mulliken
C(1)
S(2)
N(3)
S(4)
C(5)
F(6)
F(7)
F(8)
F(9)
O(10)
O(11)
O(12)
O(13)
F(14)
F(15)
B3LYP
MP2
Natural charges
B3LYP
MP2
0.434
1.016
0.715
1.014
0.447
0.199
0.186
0.199
0.206
0.500
0.504
0.507
0.495
0.193
0.207
0.691
1.373
0.885
1.378
0.704
0.284
0.270
0.283
0.291
0.637
0.644
0.647
0.634
0.276
0.293
0.877
2.137
1.209
2.128
0.885
0.358
0.352
0.358
0.363
0.921
0.918
0.916
0.917
0.353
0.363
1.009
2.353
1.306
2.343
1.018
0.399
0.393
0.399
0.404
1.008
1.006
1.003
1.007
0.394
0.405
distribution is further backed by a plot of the electrostatic
potential (Figure 2 a).[20] Thus, electrostatic (high negative
charge on the oxygen atoms, more favorable coordination to
two sulfur atoms than to one nitrogen atom) and steric
reasons (the nitrogen center is well shielded by its surroundings, Figure 2 b) are the origin of the observed coordination
mode of the Tf2N ion.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2005, 44, 5485 –5488
Angewandte
Chemie
These observations show that ionic liquids containing the
bis(trifluoromethanesulfonyl)amide anion (Tf2N) are not as
“innocent” or “noncoordinating” as they are often believed to
be. In the absence of any stronger coordinating ligand, even
the weak bis(trifluoromethanesulfonyl)amide anion coordinates to a metal cation present in solution. This observation is
important, as many reactions in these solvents may be
crucially influenced by complexation. Furthermore, our
observation helps to understand the solvation process of
inorganic salts in ionic liquids, since we are able to show that
the metal cation, in our case Yb2+, dissolves under complexation. The discovery of [mppyr]2[Yb(Tf2N)4] shows not only
the high potential of ionic liquids for the synthesis of complex
compounds with weakly coordinating anions but also the
versatility of ionic liquids as solvents for highly reducing
species as divalent rare-earth iodides.
[11]
Received: April 13, 2005
Published online: July 26, 2005
.
Keywords: coordination modes · fluorinated ligands ·
ionic liquids · lanthanides · rare earth metals
[12]
[1] K. Mikami, O. Kotera, Y. Motoyama, M. Tanaka, Inorg. Chem.
Commun. 1998, 1, 10.
[2] a) H. Kobayashi, J. Nie, T. Sonoda, Chem. Lett. 1995, 307;
b) D. B. Baudry, A. Dormond, F. Duris, J. M. Bernard, J. R.
Desmurs, J. Fluorine Chem. 2003, 121, 233; c) M. J. Earle, U.
Hakala, B. J. McAuley, M. Nieuwenhuyzen, A. Ramani, K. R.
Seddon, Chem. Commun. 2004, 1368.
[3] D. B. Baudry, A. Dormond, F. Duris, J. M. Bernard, J. R.
Desmurs, J. Fluorine Chem. 2003, 121, 233.
[4] Generally the crystallization of lanthanide sulfonylaminates
seems to be difficult: see ref. [1] and Y. Hasegawa, T. Ohkubo, K.
Sogabe, Y. Kawamura, Y. Wada, N. Nakashima, S. Yanagida,
Angew. Chem. 2000, 112, 365; Angew. Chem. Int. Ed. 2000, 39,
357.
[5] a) I. Krossing, I. Raabe, Angew. Chem. 2004, 116, 2116; Angew.
Chem. Int. Ed. 2004, 43, 2066; b) S. H. Strauss, Chem. Rev. 1993,
93, 927.
[6] a) I. A. Koppel, R. W. Taft, F. Ania, S.-Z. Zhu, L.-Q. Hu, K.-S.
Sung, D. D. DesMarteau, L. M. Yagupolskii, Y. L. Yagupolskii,
N. V. IgnatMv, N. V. Kondratenko, A. Y. Volkonskii, V. M.
Vlasov, R. Notario, P.-C. Maria, J. Am. Chem. Soc. 1994, 116,
3047; b) D. D. DesMarteau, J. Fluorine Chem. 1995, 72, 203.
[7] a) P. Bonhote, A. Dias, N. Papageorgiou, K. Kalyanasundaram,
M. GrNtzel, Inorg. Chem. 1996, 35, 1168; b) M. J. Earle, K. R.
Seddon, Pure Appl. Chem. 2000, 72, 1391; c) P. Wasserscheid, W.
Keim, Angew. Chem. 2000, 112, 3926; Angew. Chem. Int. Ed.
Engl. 2000, 39, 3772; d) J. D. Holbrey, W. M. Reichert, R. D.
Rogers, Dalton Trans. 2004, 2267.
[8] V. R. Koch, C. Nanjundah, G. Battista Appetecchi, B. Scorsati, J.
Electrochem. Soc. 1995, 142, L116.
[9] a) J. L. Nowinski, P. Lightfoot, P. G. Bruce, J. Mater. Chem. 1994,
4, 1579; b) J. R. Atloms, C. R. Sides, S. E. Creager, J. L. Harris,
W. T. Penningtion, B. H. Thomas, D. D. DesMarteau, J. New
Mater. Electrochem. Syst. 2003, 6, 9.
[10] Crystal structures of purely organic compounds: a) J. J. Golding,
D. R. MacFarlane, L. Spiccia, M. Forsyth, B. W. Skelton, A. H.
White, Chem. Commun. 1998, 15, 1593; b) V. Montanari, D. D.
DesMareteau, W. T. Pennington, J. Mol. Struct. 2000, 550/551,
337; c) C. M. Forsyth, D. R. MacFarlane, J. J. Golding, J. Huang,
J. Sun, M. Forsyth, Chem. Mater. 2002, 14, 2103; d) J. A.
Angew. Chem. Int. Ed. 2005, 44, 5485 –5488
[13]
[14]
Schlueter, U. Geiser, H. H. Wang, A. M. Kini, B. H. Ward, J. P.
Parakka, R. G. Daugherty, M. E. Kelly, P. G. Nixon, R. W.
Winter, G. L. Gard, L. K. Montgomery, H.-J. Koo, M.-H.
Whangbo, J. Solid State Chem. 2002, 168, 524; e) M. G.
Davidson, P. R. Raithby, A. L. Johnson, P. D. Bolton, Eur. J.
Inorg. Chem. 2003, 3445; f) D. D. DesMarteau, W. T. Pennington, V. Montanari, B. H. Thomas, J. Fluorine Chem. 2003, 122,
57; g) J. D. Holbrey, W. M. Reichert, R. D. Rogers, Dalton Trans.
2004, 2267.
Crystal structures of metal–organic compounds: a) J. L. Nowinski, P. Lightfoot, P. G. Bruce, J. Mater. Chem. 1994, 4, 1579;
b) A. Haas, C. Klare, P. Betz, J. Bruckmann, C. Kruger, Y.-H.
Tsay, F. Aubke, Inorg. Chem. 1996, 35, 1918; c) L. Xue, C. W.
Padgett, D. D. DesMareau, W. T. Penningtion, Solid State Sci.
2002, 4, 1535; d) D, Brouilette, D. E. Irish, N. J. Taylor, G.
Perron, M. Odziemkowski, J. E. Desnoyers, Phys. Chem. Chem.
Phys. 2002, 4, 6063; e) Z. Zak, A. Ruzicka, Z. Kristallogr. 1998,
213, 217; f) M. G. Davidson, P. R. Raithby, A. L. Johnson, P. D.
Bolton, Eur. J. Inorg. Chem. 2003, 3445; g) L. Xue, C. W.
Padgett, D. D. DesMarteau, W. T. Pennington, Acta Crystallogr.
Sect. C 2004, 60, m200; h) L. Xue, D. D. DesMarteau, W. T.
Pennington, Solid State Sci. 2005, 7, 311; i) D. D. DesMarteau
et al., CCDC-247563, private communication; j) A. Babai, A.-V.
Mudring, J. Alloys Compd., submitted; k) A. Babai, A.-V.
Mudring, Chem. Mater., in press.
Synthesis: YbI2 was prepared by reduction of YbI3 with Yb
metal in a sealed tantalum container jacketed with an evacuated
silica tube. YbI3 was prepared from ytterbium (chips, Chempur,
99.5 %) and iodine (Riedel de HNen, 99.8 %) according to the
procedure described in: G. Meyer, Chem. Rev. 1988, 88, 93].
[mppyr][Tf2N] was prepared according to the procedure in D. R.
Mac Farlane, P. Meakin, J. Sun, N. Amini, M. Forsyth, J. Phys.
Chem. B 1999, 103, 4164. Storage and manipulation of the
starting materials and products were handled under dry-box
conditions under dry argon (MBraun, Garching, Germany).
YbI2 + 4 [mppyr][Tf2N]![mppyr]2[Yb(Tf2N)4] + 2 [mppyr][I]
The reaction of YbI2 (0.2 mmol, 87 mg) with [mppyr][Tf2N]
(4.8 mmol, 1 g) was carried out in a evacuated and sealed silica
tube at 393 K for 48 h. Colorless single crystals of [mppyr]2[Yb(Tf2N)4] formed as the single, insoluble product after
subsequent cooling (2 K min1) of the mixture to room temperature. The product was separated by filtration. Estimated yield:
66 %; m.p. 107 8C; IR (KBr): ñ = 1473 (s), 1433 (s), 1352 (vs),
1331 (vs), 1231 (vs), 1197 (vs), 1144 (vs), 1058 (vs), 972 (w),
940 (w), 797 (m), 763 (w), 742 (m), 652 (s), 618 (s), 608 (s),
599 (s), 574 (s), 515 cm1 (s).
Crystal data: A suitable single crystal (0.3 Q 0.2 Q 0.2 mm) was
mounted in a glass capillary. Intensity data were collected on an
IPDS diffractometer (Stoe, Darmstadt, Germany) at 120(2) K.
120 K: monoclinic, space group P21/n; a = 1122.01(4), b =
2260.21(9),
c = 2188.47(9) pm,
b = 102.209(3)8,
V=
5.4244(4) nm3 ; Z = 4; 1calcd = 1.8978 g cm3 ; 1.80 < q < 27.198;
IPDS II, MoKa radiation (l = 71.073 pm); T = 120(2) K;
F(000) = 3056; m = 2.177 mm1; 56 375 reflections were measured, of which 11 822 were unique. R1 = 0.0436 and wR2 =
0.1109 for [I0 > 2s(I0)]. The data were processed with the
program systems SHELX-97 [G. M. Sheldrick, SHELX-97,
UniversitNt GRttingen, 1997] and X-Seed [L. J. Barbour, J.
Supramol. Chem. 2001, 1, 189]. Numerical absorption correction
after crystal shape optimization was performed by using the
programs XRED and XSHAPE [Stoe, XRED 1.01 and
XSHAPE 1.01, Darmstadt, 1996]. CCDC-268479 contains the
supplementary 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.
G. B. Deacon, C. M. Forsyth, P. C. Junk, B. W. Skelton, A. White,
Chem. Eur. J. 1999, 5, 1452.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5487
Communications
[15] C. E. PleTnik, S. Liu, J. Liu, X. Chen, E. A. Meyers, S. G. Shore,
Inorg. Chem. 2002, 41, 4936.
[16] T. Phillips, D. E. Sands, W. F. Wagner, Inorg. Chem. 1968, 7, 2295.
[17] A. Haas, C. Klare, P. Betz, J. Bruckmann, C. Kruger, Y.-H. Tsay,
F. Aubke, Inorg. Chem. 1996, 35, 1918.
[18] All calculations were performed using the Gaussian03 program
package [Gaussian 03 (Revision B.04), M. J. Frisch, G. W. Trucks,
H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman,
J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M.
Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M.
Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida,
T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E.
Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A.
Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S.
Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick,
A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q.
Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong,
C. Gonzalez, J. A. Pople, Gaussian, Inc., Pittsburgh, PA, 2003].
The structure of cisoid Tf2N has been fully optimized at the MP2/
6-311 + G* and B3LYP/6-311 + G* levels of theory. MP2 =
second-order Møller–Plesset perturbation theory (a) W. J.
Hehre, L. Radom, P. v. R. Schleyer, J. A. Pople, Ab Initio
Molecular Orbital Theory, Wiley, New York, 1986; b) J. B.
Foresman, E. Frisch, Exploring chemistry with electronic structure methods, 2nd ed., Gaussian, Pittsburgh, PA, 1996), B3LYP is
a density functional theory (DFT) method (R. G. Parr, Y. Yang,
Density-functional theory of atoms and molecules, Oxford
University Press, New York, 1989) using BeckeVs three-parameter nonlocal exchange functional (A. D. Becke, J. Chem. Phys.
1993, 98, 5648) with the nonlocal correlation of Lee, Yang, and
Parr (C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785). All
the stationary points were positively identified for minima (no
imaginary frequency) or transition states (only one imaginary
frequency).
[19] D. W. J. Cruickshank, J. Chem. Soc. 1961, 5486.
[20] In order to evaluate second-order interactions natural bond
orbital (NBO) analysis was performed at the respective level
(a) A. E. Reed, R. B. Weinstock, F. Weinhold, J. Chem. Phys.
1985, 83, 735; b) J. E. Carpenter, F. Weinhold, J. Mol. Struct.
(THEOCHEM) 1988, 169, 41). Atomic charges have been
estimated using NPA method (A. E. Reed, L. A. Curtiss, F.
Weinhold, Chem. Rev. 1988, 88, 899).
5488
www.angewandte.org
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2005, 44, 5485 –5488
Документ
Категория
Без категории
Просмотров
1
Размер файла
148 Кб
Теги
complex, уnoncoordinatingф, characterized, structurale, ioni, coordinated, anion, mppyr, yb2, liquid, tf2n
1/--страниц
Пожаловаться на содержимое документа