Organometallics
ARTICLE
removed under reduced pressure, and the colorless solid residue was
suspended in benzene (5 mL). After filtration, the insoluble material was
extracted with benzene (2 ꢁ 5 mL) and the combined organic phases were
Selected crystallographic data, plots of the molecular structures, and
selected geometric parameters of [Mg2(THF)6Br3][(C6F5)2BH2]
and [Mg(Et2O)2][(C6F5)2BH2]2 2(benzene) and ORTEP plot of
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freeze-dried in vacuo to obtain (C6F5)2BH SMe2 as a colorless flaky solid.
{[Mg2(Et2O)3Br2.4Cl0.6][(C6F5)2BH2]}2. CIF files for [Mg2-
(THF)6Br3][(C6F5)2BH2], {[Mg2(Et2O)3Br2.4Cl0.6][(C6F5)2-
BH2]}2 (toluene) 2CHCl3, and [Mg(Et2O)2][(C6F5)2BH2]2
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Yield: 0.13 g (90%).
All 1H, 11B, and 19F{1H} NMR shift values are in full agreement with
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the published data for (C6F5)2BH SMe2 (cf. the Supporting Informa-
2(benzene). This material is available free of charge via the Internet
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tion for details).15
General Procedure for the Hydroboration of Alk-1-ynes.
{[Mg2(Et2O)3Br2Cl][(C6F5)2BH2]}2 was suspended in a mixture of
benzene (2 mL) and hexane (2 mL). The alk-1-yne (solution in
benzene) and Me3SiCl (solution in hexane) were added at room
temperature via syringe. After the mixture was stirred for 2 h, the
conversion was complete (NMR spectroscopic control). The reaction
mixture was filtered, the insoluble material was extracted with benzene
(2 ꢁ 1 mL), and the combined organic phases were evaporated to
dryness under reduced pressure to obtain the hydroboration product in
pure form.
’ AUTHOR INFORMATION
Corresponding Author
*Fax: þ49 69 798 29260. E-mail: Matthias.Wagner@
chemie.uni-frankfurt.de.
’ ACKNOWLEDGMENT
M.W. acknowledges financial support by the Beilstein Institut,
Frankfurt/Main, Germany, within the research collaboration
NanoBiC.
(C6F5)2BC(H)dC(H)tBu: {[Mg2(Et2O)3Br2Cl][(C6F5)2BH2]}2
(0.10 g, 0.06 mmol), tert-butylacetylene (0.13 M in benzene; 0.95 mL,
0.12 mmol), and Me3SiCl (0.27 M in hexane; 0.50 mL, 0.14 mmol);
yield: 0.036 g (70%). (C6F5)2BC(H)dC(H)Ph: {[Mg2(Et2O)3Br2Cl]-
[(C6F5)2BH2]}2 (0.027 g, 0.017 mmol), phenylacetylene (0.17 M in
benzene; 0.20 mL, 0.033 mmol), and Me3SiCl (0.18 M in hexane;
0.20 mL, 0.037 mmol); yield: 0.012 g (79%). All 1H, 11B, and 19F{1H}
NMR shift values are in full agreement with the published data for these
compounds (cf. the Supporting Information for details).11
’ REFERENCES
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X-ray Crystal Structure Analysis of [Mg2(THF)6Br3]-
[(C6F5)2BH2], {[Mg2(Et2O)3Br2.4Cl0.6][(C6F5)2BH2]}2 (toluene)
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2CHCl3, and [Mg(Et2O)2][(C6F5)2BH2]2 2(benzene). Data were
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collected on a STOE IPDS II two-circle diffractometer with graphite-
monochromated Mo KR radiation. Empirical absorption corrections were
performed using the MULABS28 option in PLATON.29 The structures
were solved by direct methods using the program SHELXS30 and refined
against F2 with full-matrix least-squares techniques using the program
SHELXL-97.31 Five of the six coordinating THF molecules in
[Mg2(THF)6Br3][(C6F5)2BH2] are disordered over two positions with
occupancy factors of 0.51(1), 0.53(3), 0.54(2), 0.60(4), and 0.53(2) for
the major occupied sites. The C atoms of the disordered THF molecules
were isotropically refined. Bond lengths and angles of the disordered THF
molecules were restrained to be equal to those of the nondisordered THF
molecule. In {[Mg2(Et2O)3Br2.4Cl0.6][(C6F5)2BH2]}2 (toluene) 2CHCl3,
the toluene molecule is disordered over two equally occupied positions.
One of the Br atoms (Br(1)) was refined as being fully occupied, the
remaining two halogen positions were refined as being disordered with Cl
but sharing the same coordinates and the same displacement parameters.
The respective site occupation factors refined to 0.704(5) for Br(2) and
0.681(5) for Br(3). If both ratios are artificially forced to 0.5:0.5, several
peaks appear in the residual electron density map slightly below 1 e Åꢀ3 at
distances of ca. 0.5 Å from X(2) and X(3) (cf. Figure 2). If the ratio Brꢀ:Clꢀ
is refined freely, no significant peak arises close to X(2) and X(3). In
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Engl. 1995, 34, 809–811.
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Grimme, S.; Stephan, D. W. Chem. Commun. 2007, 5072–5074.
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(13) Chambers, R. D.; Chivers, T. J. Chem. Soc. 1965, 3933–3939.
(14) (C6F5)2SnMe2 is also accessible from C6F5MgBr and
Br2SnMe2. However, use of C6F5Li and the less expensive Cl2SnMe2
(which can, moreover, be recycled) gives the target compound in higher
purity and better yield.11
[Mg(Et2O)2][(C6F5)2BH2]2 2(benzene), the H atoms bonded to B were
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freely refined.
CCDC reference numbers: 813324 ([Mg2(THF)6Br3][(C6F5)2BH2]),
813325 ({[Mg2(Et2O)3Br2.4Cl0.6][(C6F5)2BH2]}2 (toluene) 2CHCl3),
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and 813326 ([Mg(Et2O)2][(C6F5)2BH2]2 2(benzene)).
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(15) Fuller, A.-M.; Hughes, D. L.; Lancaster, S. J.; White, C. M.
Organometallics 2010, 29, 2194–2197.
’ ASSOCIATED CONTENT
(16) Hoshi, M.; Shirakawa, K.; Okimoto, M. Tetrahedron Lett. 2007,
48, 8475–8478.
(17) Tamborski, C.; Soloski, E. J.; Ward, J. P. J. Org. Chem. 1966,
31, 4230–4232.
S
Supporting Information. Synthesis and crystallization of
b
[Mg2(THF)6Br3][(C6F5)2BH2], three-step synthesis of {[Mg2-
(Et2O)3Br2Cl][(C6F5)2BH2]}2, and synthesis of [Mg(Et2O)2]-
[(C6F5)2BH2]2. 1H, 11B, and 19F{1H} NMR spectra of (C6F5)2BH
(18) Douthwaite, R. E. Polyhedron 2000, 19, 1579–1583. The anion
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SMe2, (C6F5)2BC(H)dC(H)tBu, and (C6F5)2BC(H)dC(H)Ph.
[(C6F5)2BH2]ꢀ has also been obtained by Berke et al. upon reaction of
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dx.doi.org/10.1021/om200186w |Organometallics 2011, 30, 2838–2843