The first monomeric β-diketiminate stabilized four-coordinated bismuth(III) bistrifluoromethanesulfonate

Article abstract of DOI:10.1002/zaac.201100463

The sterically encumbered β-diketiminate bismuth(III) bistriflate, LBi(OSO₂CF₃)₂ [L = HC{(CMe)N(2, 6-iPr ₂C₆H₃)}₂] (2) was prepared from a facile one-pot reaction between potassium β-diketiminate LK (1) and bismuth(III) triflate. It was characterized by elemental analysis, FT-IR, ¹H NMR,¹³C NMR, and ¹⁹F NMR spectroscopy. The molecular structure of 2 was further confirmed by single-crystal X-ray crystallography. The solid-state structure of 2 reveals a first structurally characterized monomeric β-diketiminate supported group 15 bistriflate. The coordination number of bismuth is four. Copyright

Full text of DOI:10.1002/zaac.201100463

SHORT COMMUNICATION
DOI: 10.1002/zaac.201100463
The First Monomeric β-Diketiminate Stabilized Four-Coordinated
Bismuth(III) Bistrifluoromethanesulfonate
Paladugu Suresh,[a] Arruri Sathyanarayana,[a] Ganesan Prabusankar,*[a]
Olivier Hernandez,[b] and Stéphane Golhen[b]
Keywords: Bismuth; β-Diketiminate; Metal triflate; Main-group chemistry
Abstract. The sterically encumbered β-diketiminate bismuth(III) bi- molecular structure of 2 was further confirmed by single-crystal X-ray
striflate, LBi(OSO2CF3)2 [L = HC{(CMe)N(2,6-iPr2C6H3)}2] (2) was
crystallography. The solid-state structure of 2 reveals a first structurally
prepared from a facile one-pot reaction between potassium β-diketim- characterized monomeric β-diketiminate supported group 15 bistrifl-
inate LK (1) and bismuth(III) triflate. It was characterized by elemental
ate. The coordination number of bismuth is four.
1
analysis, FT-IR, H NMR,13C NMR, and 19F NMR spectroscopy. The
Introduction
β-Diketiminates have become one of the most versatile and
popular class of ancillary ligands for main group and transition
metal chemistry.[1,2] Complexes of bulky β-diketiminates have
tended to have unusual structure and bonding environments
and have also afforded highly active catalysts for a variety of
chemical transformations.[2] In the last decade, this rekindled
interest came to light, mainly due to the isolation of stable and
soluble low valent main group derivatives.[1,2] Although the
heavier group 13 and 14 β-diketiminate molecules were suc-
cessfully synthesized and stabilized, only few compounds of
group 15 elements with β-diketiminate ligands have been in-
vestigated so far.[1,2] In particular, β-diketiminate supported
triflate derivatives of phosphorus(III) are known for some ex-
tend (Figure 1, I–III),[3] while the similar chemistry is not
known with arsenic, antimony, and bismuth, mainly due to the
lack of suitable starting precursors or highly unstable nature of
the reactions/products.
Figure 1. Known β-diketiminate supported triflate derivatives of group
15 molecules.
Results and Discussion
In this paper, we describe the facile synthesis and characteri-
zation of low-valent bismuth(III) bistriflate with bulky β-diket-
The imine-supported bismuth(III) triflates have shown
promising application in organic synthesis.[4] Up to now only
ten molecules of β-diketiminate (or similar types of ligand)
stabilized bismuth derivatives are known in the literature.[5]
The first hexacoordinated monomeric β-diketiminate ligand
with nitrogen-based pendant arms [{HC(Et2NCH2CH2NCMe)
2}BiCl2] was reported by Roesky and his co-workers in
2007.[5a] Later different derivatives of penta- or hexacoordi-
nated β-diketiminate (or similar types of ligand) stabilized bis-
muth halides were reported. In particular, β-diketiminate stabi-
lized bismuth(III) bistriflate (IV) is the only example known
in the literature (reported by Zhu and his research group after
submission of this article), where the central bismuth atom is
pentacoordinated.[5c] However, the structurally characterized
tetracoordinated (or less) β-diketiminate derivatives of bismuth
triflates are not reported yet.
iminate ligand, LBi(OSO2CF3)2 [L
= HC{(CMe)N(2,6-
iPr2C6H3)}2] (2). To the best of our knowledge molecule 2
represent the first example of a monomeric β-diketiminate sta-
bilized group 15 bistriflate.
* Dr. G. Prabusankar
Fax: +91-4023016032
E-Mail: prabu@iith.ac.in
[a] Department of Chemistry
Indian Institute of Technology-Hyderabad
ODF Estate
Yeddumailaram, Andhra Pradesh, 502205, India
[b] Sciences Chimiques de Rennes, UMR 6226, CNRS
Université de Rennes 1
263 Avenue du Général Leclerc CS 74205
35042 Rennes Cedex, France
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201100463 or from the au-
thor.
Z. Anorg. Allg. Chem. 2012, 638, (3-4), 617–620
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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G. Prabusankar et al.
SHORT COMMUNICATION
A monomeric β-diketiminate derivative of bismuth(III) bi- namely O(4) and F(4) for the S(2)/S(2)i-containing triflate and
striflate (2) was obtained in 40–47% yield from the reaction O(3) and F(1) for the S(1)/S(1)i-containing triflate. An ORTEP
of potassium β-diketiminate, LK (1) with bismuth(III) triflate drawing (see Figure 2) shows the disorder experienced by the
in toluene (Scheme 1). However high yield synthesis of 2 with S(1)-containing triflate. For clarity, only one component of
THF coordinated central bismuth atom was reported at the S(2)-containing triflate is drawn. It is worth mentioning that
same time from the reaction between LBiCl2 and silver triflate the methyl carbon atom C(1) also splits into two positions as
in toluene/THF mixture at –15 °C.[5c] Molecule 2 is stable in C(1a) and C(1b). The central bismuth atom is four-coordinated
a inert atmosphere for several weeks and soluble in polar and and the coordination sphere is composed of two nitrogen atoms
mid polar organic solvents such as benzene, toluene, fluoro- of the chelating β-diketiminate anion and two triflate oxygen
benzene, THF, and CH2Cl2. The analytically pure dark orange atoms. The coordination arrangement of the bismuth atom can
crystals of 2 were obtained from toluene solution of the reac- be described as distorted disphenoidal (“seesaw”) arrangement
tion mixture. The purity of sample was confirmed by elemental with O–Bi–O bond angles of 170.69(10)°, implying stereo-
analysis. Compound 2 was further characterized by FT-IR, 1H, chemical activity of the lone pair on the bismuth atom. Unlike
13C, and 19F NMR spectroscopy. A singlet signal at δ = I–III, the triflate moieties in 2 are covalently linked with the
–78.1 ppm in the 19F NMR spectrum corresponding to the trifl- bismuth atom (similar to IV).[3]
ate group fluorine atoms, as well as absorption bands in the
FT-IR spectrum at 1372, 1351, and 1224 cm–1, indicate the
presence of a monodentate triflate ligand, covalently linked to
the bismuth(III) atom.[6] However, compound 2 underwent
slow decomposition when it was dissolved in fresh solvent and
1
formed a small amount of gray turbid. Thus, the H and 13C
NMR spectra of 2 exhibit peak broadening and additional sig-
nals (for example in 13C NMR, five, two, and four signals
were obtained for isopropyl CH, diketiminate methyl and iso-
propyl CH3, respectively) in addition to all expected ligand
resonances. Some of these signals may stem from decomposi-
tion of 2 in solution. The structure of 2 was further confirmed
by single-crystal X-ray diffraction technique.
Figure 2. Molecular structure of 2. Hydrogen atoms and the disordered
component of the second triflate molecule are omitted for the sake of
clarity. Selected bond length /Å and angles /° for 2: Bi1–N1, 2.168(3);
O3–Bi1, 2.360(3); O4–Bi1, 2.373(3); O1–S1, 1.431(4); O2–S1,
1.428(5); O3–S1, 1.455(3); O4–S2, 1.581(3); O5–S2, 1.425(5); O6–
S2, 1.412(5); N1–Bi1–N1, 87.30(14); O3–Bi1–O4, 170.69(10); S1–
O3–Bi1, 154.66(15); S2–O4–Bi1, 112.99(16).
Scheme 1. Synthesis of 2.
The O–Bi bond lengths are not equal, the distance of the
The dark orange crystals of 2 suitable for X-ray structure O(3)–Bi(1) bond [2.360(3) Å] is slightly shorter than that of
analysis were obtained from toluene at –30 °C over a period the O(4)–Bi(1) bond [2.373(3) Å]. The average O–Bi bond
of 15 days. Molecule 2 crystallized in the Pnma orthorhombic length [2.367(3) Å] of 2 is considerably shorter (av. 2.407 Å)
space group.[7,8] The solid-state structure of 2 is illustrated in than that of IV,[5c] however nearly similar to that of [{2,6-
Figure 2. The asymmetric unit cell contains one half molecule. (tBuOCH2)C6H3}Bi(OSO2CF3)2] [2.377(7) Å].[9] The C3N2Bi
The central Bi3+ cation is lying onto a mirror plane. One oxy- ring is in boat conformation. This boat conformation can also
gen and one fluorine atom of each triflate ion [O(4), F(4), and be found in many other derivatives of these ligands from group
O(3), F(1)], as well as C(13) atom of diimine anion are lying 15 metals[5] and from different elements of the periodic
onto the same mirror plane. A strong disorder is observed for table.[1–3] The folding of the C3N2Bi ring can be attributed to
both triflate ions, each is modeled by two disordered compo- the greater steric interactions from 2,6-iPr2C6H3 groups and
nents, the occupation factors of all atoms of the latter moieties triflate moieties.[10] Thus, the β-diketiminate ligand in complex
being refined (and further fixed) to 0.5. Obviously, for each 2 is symmetrically coordinated to the bismuth atom with Bi–
triflate molecule, the oxygen and fluorine atoms lying onto the N bond lengths of 2.168(3) Å. It is also important to note that
mirror plane are shared by the two disordered components, the observed Bi–N bond lengths in IV are similar [2.237(3)
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© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2012, 617–620

Four-Coordinated Bismuth(III) Bistrifluoromethanesulfonate
NMR (C6D6, 250 MHz): δ = 7.15–7.0 (m, 6 H, Ar), 4.80 (s, 1 H, γ-
CH), 3.37–3.26 (sept, 4 H, CHCH3), 1.80 (s, 6 H, CCH3), 1.13, 1.18
(d, 12 H, CHCH3). 13C NMR (C6D6, 62.9 MHz): δ = 163.3 (CN),
142.5, 142.3, 124.9 (Ar), 122.3 (CF3), 104.0 (γ-CH), 29.7, 28.0, 27.8,
27.2, 27.0 (CHMe2), 25.1, 24.2 (CH3), 23.3, 22.4, 22.0, 19.9 (iPr-CH3).
19F NMR (C6D6, 235.3 MHz): δ = –78.1 ppm (OSO2CF3). IR (neat):
ν˜ = 2937 (m), 2902 (w), 2845 (w), 1584 (w), 1515(s), 1451 (m), 1372
(w), 1351 (w), 1224 (vs), 1181 (s), 1169 (s), 1092 (w), 1049 (w), 1016
(s), 991 (m), 967 (w), 927 (w), 791 (m), 752 (m), 629 (s), 572 (w),
532 (w), 512 (m), 435 (w) cm–1.
and 2.230(6) Å] and (av. 2.234 Å) much larger than 2. The
bismuth atoms lie significantly out of the C3N2 planes so there
are considerable dihedral angles between the C3N2 and BiN2
arrays. The bond lengths within the backbone of the β-diketim-
inate ligand fall in the range of corresponding distances of
single and double bonds, which reflects substantial electron
delocalization.
Conclusions
Supporting Information (see footnote on the first page of this article):
IR and NMR spectra of 2. Images of the molecular structure of 2, the
coordination geometry of bismuth in 2, and the space-filling model of
2.
The facile synthesis and structural characterization of the
first β-diketiminate bistriflate of bismuth(III) is reported
herein. In contrast to the β-diketiminate phosphorus triflates
(I–III), compound 2 features four-coordinated monomeric β-
diketiminate bismuth atom. The solid-state structure of 2 indi-
cates that the triflate ligands are covalently linked to the central
bismuth atom.
Acknowledgements
We thank the Department of Science and Technology (DST-FT 4842)
and Indian Institute of Technology-Hyderabad for financial support of
this research. PS thank CSIR for the fellowship. AS thank UGC for the
fellowship. We gratefully acknowledge Dr. Olivier Hernandez and Dr.
Stéphane Golhen for structural refinement. We are indebted to Dr. Su-
resh Babu Kalidindi and Mr. Adinarayana Doddi for FT-IR measure-
ment.
Experimental Section
General Considerations: All manipulations were carried out in an
atmosphere of purified argon using standard Schlenk and glove box
techniques. The solvents were dried with an MBraun Solvent Purifica-
tion System. LK (1) was prepared accordingly to previously reported
methods.[11] 2,6-Diisopropylaniline (Aldrich), 2,4-pentanedione (Ald-
rich), potassium hydride (Acros), and bismuth(III) triflate (ABCR)
were purchased from commercial sources. IR measurement (neat) was
carried out with a Bruker Alpha-P Fourier transform spectrometer. Ele-
mental analyses were performed with the Euro EA Elemental Analysis.
NMR spectra were recorded with a Bruker Avance DPX-250 spec-
trometer at 25 °C unless otherwise stated. Chemical shifts are given
relative to TMS and were referenced to the solvent resonances as in-
ternal standards. The 19F NMR spectrum was referenced to a 19F reso-
nance of the external HSC6F5 reference (C6F5SH δ = 59.7 ppm).[12]
References
[1] For selected examples: a) L. Bourget-Merle, M. F. Lappert, J. R.
Severn, Chem. Rev. 2002, 79, 3031–3065; b) C. Cui, H. W. Roe-
sky, H.-G. Schmidt, M. Noltemeyer, H. Hao, F. Cimpoesu, Angew.
Chem. Int. Ed. 2000, 39, 4274–4276; c) Y. Peng, H. Fan, V. Jan-
cik, H. W. Roesky, R. Herbst-Irmer, Angew. Chem. Int. Ed. 2004,
43, 6190–6192; d) Y. Peng, H. Fan, H. Zhu, H. W. Roesky, J.
Magull, C. E. Hughes, Angew. Chem. Int. Ed. 2004, 43, 3443–
3445; e) N. J. Hardman, B. E. Eichler, P. P. Power, Chem. Com-
mun. 2000, 1991–1992; f) C. Gemel, T. Steinke, M. Cokoja, A.
Kempter, R. A. Fischer, Eur. J. Inorg. Chem. 2004, 4161–4176;
g) S. P. Green, C. Jones, A. Stasch, Science 2007, 318, 1754–
1757; h) Y. Wang, B. Quillian, P. Wei, H. Wang, X.-J. Yang, Y.
Xie, R. B. King, P. v. R. Schleyer, H. F. Schaefer-III, G. H. Robin-
son, J. Am. Chem. Soc. 2005, 127, 11944–11945; i) M. S. Hill,
P. B. Hitchcock, R. Pongtavornpinyo, Science 2006, 311, 1904–
1907; j) T. W. Hayton, G. Wu, J. Am. Chem. Soc. 2008, 130,
2005–2014; k) G. Prabusankar, C. Gemel, P. Parameswaran, C.
Flener, G. Frenking, R. A. Fischer, Angew. Chem. Int. Ed. 2009,
48, 5526–5529; l) G. Prabusankar, A. Kempter, C. Gemel, M.-K.
Schröter, R. A. Fischer, Angew. Chem. Int. Ed. 2008, 47, 7234–
7237; m) S. Gonzalez-Gallardo, G. Prabusankar, T. Cadenbach,
C. Gemel, M. v. Hopffgarten, G. Frenking, R. A. Fischer, Metal-
Metal Bonding (Ed.: G. Parkin), Springer, 2010, vol. 136, pp.
147–188; n) A. Meltzer, C. Praesang, M. Driess, J. Am. Chem.
Soc. 2009, 131, 7232–7233; o) N. W. Aboelella, E. A. Lewis,
A. M. Reynolds, W. W. Brennessel, C. J. Cramer, W. B. Tolman,
J. Am. Chem. Soc. 2002, 124, 10660–10661; p) P. L. Holland,
Can. J. Chem. 2005, 83, 296–301; q) P. L. Holland, Acc. Chem.
Res. 2008, 41, 905–914; r) Inorg. Synth. (Ed.: T. B. Rauchfuss),
Wiley, 2010, vol. 35, pp 1–54.
Single crystals were mounted on
a Goniometer KM4/Xcalibur
equipped with Sapphire2 (large Be window) detector (Mo-Kα radiation
source, λ = 0.71073 Å). The crystal structure of 2 was measured with
an Oxford Xcalibur 2 diffractometer. Data were collected at 108 K and
structure was solved by direct methods using the SIR-97 program[13]
and refined with a full-matrix least-squares method on F2 using the
SHELXL-97 program.[14]
Crystallographic data (excluding structure factors) for the structure in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
number CCDC-840264 (Fax: +44-1223-336-033; E-Mail: deposit@-
ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
Synthesis of LBi(OSO2CF3)2 (2): To a mixture of LK (1) (1.5 g,
3.589 mmol) and Bi(OSO2CF3)3 (2.35 g, 3.589 mmol), toluene
(60 mL) was added under vigorous stirring at room temperature. The
white turbid reaction mixture was maintained under this condition for
36 h and during this time the color of the reaction mixture changed
to dark orange with a small amount of tan-colored precipitate. After
filteration, filtrate was dried and orange residue was dissolved in tolu-
ene (4 mL) at 65 °C. The clear orange solution was stored at –30 °C
over a period of 15 days to get dark orange crystals. Yield 40–47%
[based on Bi(OSO2CF3)3]. M.p. 250–252 °C (became brown at
198 °C). Anal. for C31H41N2S2O6F6Bi (924.21): calcd. C 40.25; H
[2] a) P. Brignou, J.-F. Carpentier, S. M. Guillaume, Macromolecules
2011, 44, 5127–5135; b) R. E. Cowley, N. A. Eckert, S. Vaddadi,
T. M. Figg, T. R. Cundari, P. L. Holland, J. Am. Chem. Soc. 2011,
133, 9796–9811; c) A. Jana, S. P. Sarish, H. W. Roesky, D.
Leusser, I. Objartel, D. Stalke, Chem. Commun. 2011, 47, 5434–
5436; d) N. Ajellal, C. M. Thomas, T. Aubry, Y. Grohens, J.-F.
Carpentier, New J. Chem. 2011, 35, 876–880; e) K.-C. Chang, C.-
F. Lu, P.-Y. Wang, D.-Y. Lu, H.-Z. Chen, T.-S. Kuo, Y.-C. Tsai,
1
4.47; N 3.03; S 7.0%; found: C 40.19; H 4.32; N 2.97; S 6.88%. H
Z. Anorg. Allg. Chem. 2012, 617–620
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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G. Prabusankar et al.
Dalton Trans. 2011, 40, 2324–2331; f) M. Helou, G. Moriceau, [7] CrysAlis171.NET, Oxford Diffraction Ltd., version 1.171.33.32
SHORT COMMUNICATION
Z. W. Huang, S. Cammas-Marion, S. M. Guillaume, Polym.
Chem. 2011, 2, 840–850; g) A. P. Dove, V. C. Gibson, E. L. Mar-
shall, A. J. P. White, D. J. Williams, Chem. Commun. 2001, 283–
284; h) S. D. Allen, D. R. Moore, E. B. Lobkovsky, G. W. Coates,
J. Am. Chem. Soc. 2002, 124, 14284–14285; i) J. Lewin´ski, Z.
Ochal, E. Bojarski, E. Tratkiewicz, I. Justyniak, J. Lipkowski,
Angew. Chem. Int. Ed. 2003, 42, 4643–4646; j) A. P. Dove, V. C.
Gibson, E. L. Marshall, H. S. Rzepa, A. J. P. White, D. J. Wil-
(release 27-01-2009 CrysAlis171.NET).
[8] X-ray crystal structure analysis of 2: C31H41BiF6N2O6S2, M =
924.76, Orthorhombic, space group Pnam, a = 10.3572(2) Å, b =
17.5304(5) Å, c = 19.2510(7) Å, V = 3495.32(18) Å3, Z = 4, ρcalcd.
= 1.757 g/cm3, T = 108(2) K, F(000)= 1832, μ(Mo-Kα) =
5.240 mm–1, block, 23575 reflections measured, 4069 unique (Rint
= 0.0481), 290 parameters, R1 = 0.0264 [I Ͼ 2σ(I)], wR2 = 0.0440
[I Ͼ 2σ(I)], GOF = 0.858.
´
liams, J. Am. Chem. Soc. 2006, 128, 9834–9843; k) S. Gong, H. [9] L. Dostál, P. Novák, R. Jambor, A. Ru˚zˇicˇka, I. Clsarˇová, R. Jirá-
Ma, Dalton Trans. 2008, 3345–3357; l) J. Spielmann, F. Buch, S.
Harder, Angew. Chem. Int. Ed. 2008, 47, 9434–9438; m) M. R.
Crimmin, M. Arrowsmith, A. G. M. Barrett, I. J. Casely, M. S.
Hill, P. A. Procopiou, J. Am. Chem. Soc. 2009, 131, 9670–9685.
[3] a) D. Vidovic, Z. Lu, G. Reeske, J. A. Moore, A. H. Cowley,
Chem. Commun. 2006, 3501–3503; b) Z. Lu, M. Findlater, A. H.
Cowley, Chem. Commun. 2008, 184–186.
[4] S. Kobayashi, T. Ogino, H. Shimizu, S. Ishikawa, T. Hamada, K.
Manabe, Org. Lett. 2005, 7, 4729–4731.
[5] a) L. W. Pineda, V. Jancik, S. Nembenna, H. W. Roesky, Z. Anorg.
Allg. Chem. 2007, 633, 2205–2209; b) P. B. Hitchcock, M. F. Lap-
sko, J. Holecˇek, Organometallics 2007, 26, 2911–2917.
[10] M. Stender, B. E. Eichler, N. J. Hardman, P. P. Power, J. Prust, M.
Noltemeyer, H. W. Roesky, Inorg. Chem. 2001, 40, 2794–2799.
[11] M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead,
H. W. Roesky, P. P. Power, J. Chem. Soc. Dalton Trans. 2001,
3465–3469.
[12] W. Beck, K. H. Stetter, S. Tadros, K. E. Schwarzhans, Chem. Ber.
1967, 100, 3944–3954.
[13] A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C. Gia-
covazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115–119.
pert, G. Li, Inorg. Chim. Acta 2010, 363, 1230–1235; c) Y. Li, [14] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
H. Zhu, G. Tan, T. Zhu, J. Zhang, Eur. J. Inorg. Chem. 2011, 34,
5265–5272.
Received: October 20, 2011
[6] G. A. Lawrance, Chem. Rev. 1986, 86, 17–33.
Published Online: January 5, 2012
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