(2,6-Mes2H3C6)2BiH, a stable, molecular hydride of a main group element of the sixth period, and its conversion to the dibismuthene (2,6-Mes2H3C6)BiBi(2,6-Mes2C6<

Article abstract of DOI:10.1002/1521-3773(20000804)39:15<2771::AID-ANIE2771>3.0.CO;2-7

The first stable organic hydride of a main group element of the sixth period (1) has been prepared by the simple reduction of the corresponding chloride precursor. Interestingly, compound 1 transforms into the dibismuthene 2 when heated [Eq. (1)].

Full text of DOI:10.1002/1521-3773(20000804)39:15<2771::AID-ANIE2771>3.0.CO;2-7

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on an Enraf-Nonius CAD4 diffractometer with CuKa radiation, 6856
of which were independent and used for all calculations. The structure
was solved by direct methods (SHELXS-86[11]) and refined to F 2
anisotropically, the H atoms were refined with a riding model
(SHELXL-93[12]). The final quality coefficient wR2(F 2) was 0.2540,
stability is due to inherent weakness in the element ± hydro-
gen bonds since these are comparable in strength to element ±
carbon bonds[3] and alkyl and aryl derivatives of these
elements are already well-known. It is more probable that
coordinative unsaturation in the hydrides provides a relatively
low-energy decomposition pathway unavailable in the alkyl or
aryl derivatives. If this hypothesis is correct it should be
possible to synthesize stable hydrides of these metals by using
sterically encumbering groups to hinder decomposition. It is
now shown that the use of the sterically encumbering
properties of terphenyl substituents enables the first stable
hydride of bismuth to be prepared and characterized.
Treatment of the very crowded diarylbismuth halide (2,6-
Mes2H3C6)2BiCl (1) with LiAlH4 in Et2O/PhMe solution
affords the hydride derivative (2,6-Mes2H3C6)2BiH (2) in
about 30% yield. The corresponding reaction using LiAlD4
gave the deuteride (2,6-Mes2H3C6)2BiD (3). The compounds
1 ± 3 were characterized by C,H elemental analysis, 1H NMR,
2H NMR (3 only), 13C NMR, and IR spectroscopy and by
X-ray crystallography in the case of 1 and 2.[4] The structure of
1 (Figure 1) provides evidence of high steric congestion at the
with
a
conventional R(F) ˆ 0.0780 for 545 parameters and 91
restraints. One p-tBu group and the triflate are disordered. Crystallo-
graphic data (excluding structure factors) for the structures reported
in this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no. CCDC-132812
(2), CCDC-132813 (3 ´ BrÀ), and CCDC-132814 (4 ´ TfOÀ). Copies of
the data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
[11] G. M. Sheldrick, SHELXS-86, Acta Crystallogr. Sect. A 1990, 46, 467 ±
473.
[12] G. M. Sheldrick, SHELXL-93, University of Göttingen, 1993.
[13] N. Walker, D.Stuart, Acta Crystallogr. Sect. A 1983, 39, 158 ± 166.
[14] S. Pohl, B. Krebs, E. Niecke, Angew. Chem. 1975, 87, 284 ± 285; Angew.
Chem. Int. Ed. Engl. 1975, 14, 261 ± 262.
[15] M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson,
B. G. M. A. Robb, J. R.Cheeseman, T. A. Keith, G. A. Petersson, J. A.
Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrewski,
J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayak-
kara, M. Challacombe, C. Y. Peng, P. Y. Avala, W. Chen, M. W. Wong,
J. L. Andres, E. S. Replogle, R. Gom-perts, R. L. Martin, D. J. Fox,
J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C.
Gonzalez, J. A. Pople, Gaussian 94 (Revision A.1), Gaussian, Inc.,
Pittsburgh, PA, 1995.
[16] Calculated at the CCSD(t)/6-31g*//MP2(fc)/6-31g* level with zero-
point vibrational energy correction at the MP2(fc) level.
[17] R. F. W. Bader, Atoms in Molecules: A Quantum Theory, Oxford
University Press, Oxford, 1990.
[18] V.Romanenko, M. Sanchez, Coord. Chem. Rev. 1997, 158, 275 ± 324.
À
[19] Representative structural data for 4 ´ TfOÀ [CF3SO3] : P N(Mes*)
À
À
À
À
153.5(5), P N(H,Mes*) 162.7(5), P N(heterocycle) 174.4(5), P C
188.3(6) pm.
(2,6-Mes2H3C6)2BiH, a Stable, Molecular
Hydride of a Main Group Element of the Sixth
Period, and Its Conversion to the Dibismuthene
(2,6-Mes2H3C6)BiBi(2,6-Mes2C6H3)**
Ned J. Hardman, Brendan Twamley, and
Philip P. Power*
Figure 1. Structure of 1 (H atoms not shown). Selected bond lengths [Š]
and angles [8]: Bi(1)-C(1) 2.337(7), Bi(1)-C(25) 2.418(8), Bi(1)-Cl(1)
2.483(3); C(1)-Bi(1)-C(25) 123.9(3), C(1)-Bi(1)-Cl(1) 98.43(19), C(25)-
Bi(1)-Cl(1) 86.93(17).
Element derivatives of hydrogen are an important and
fundamental compound class.[1] This is especially true for
main group element hydrides, which are widely used as
reducing agents. However, many such hydrides are currently
unknown as stable species. For example, there are no stable
hydride derivatives of members of the sixth period of the
p-block (e.g., Tl, Pb, or Bi[2]). It is doubtful that their lack of
bismuth center. Although the bismuth center remains pyr-
amidally coordinated (sum of angles at Bi 309.268), there are
very large distortions in the geometry at the C(ipso) carbon
atoms bound to bismuth. Thus, the Bi-C(ipso)-C(ortho)
angles in the C(1) and C(25) terphenyl groups differ by 28.6
and 34.88, respectively. In addition, the C(1) and C(25)
aromatic ring planes deviate by 27 and 108 from the extended
[*] Prof. P. P. Power, N. J. Hardman, Dr. B. Twamley
Department of Chemistry
University of California
Davis, CA 95616 (USA)
À
À
À
line of the Bi(1) C(1) and Bi(1) C(25) bonds. The Bi C bond
lengths of 2.337(7) and 2.418(8) Š are also quite long (cf. ca.
2.28, 2.328(13), and 2.357(14) Š in the crowded molecules
Fax : (‡1)530-752-8995
E-mail: pppower@ucdavis.edu
BiMes3[5], Bi[CH(SiMe3)2]3 and Bi[2,4,6-Ph3C6H2]3[7]) and
the C(1)-Bi-C(25) angle (123.9(3)8) is very wide in compar-
ison to the usual angles seen in trivalent bismuth com-
[6]
[**] This work was supported by the National Science Foundation. The
Bruker SMART 1000 difractometer was funded in part by NSF
Instrumentation Grant CHE-9808259. Mes ˆ 2,4,6-Me3C6H2.
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pounds.[5±7] The Bi Cl distance (2.483(3) Š) is not greatly
broaden these peaks to such an extent that they are not
observable under these conditions.
À
lengthened in comparison to that in [2,4,6-(CF3)3H2C6]2BiCl
(2.463(3) Š).[8] Another interesting feature of the structure is
the large difference of about 11.58 between the two C-Bi-Cl
angles which is almost identical to that in [2,4,6-(CF3)3H2C6]2-
BiCl.[8]
Heating of 2 or 3 led to an interesting elimination reaction.
In contrast to the precursor 1, which melts without noticeable
decomposition at 203 ± 2048C, 2 and 3 undergo a rapid color
change at 135 ± 1368C for 1, and at 138 ± 1398 for 2. In both
cases a purple solid is produced which has identical spectro-
scopic properties to those previously described for the
dibismuthene (2,6-Mes2C6H3)BiBi(2,6-Mes2C6H3). X-ray data
also afforded cell constants and a structure that were
essentially the same as those previously observed.[12] The
yield of the dibismuthene in this reaction is quite high (80%)
so that this elimination reaction represents an alternative
synthetic route to dibismuthenes.[12, 13] At least two plausible
mechanisms for the decomposition of 2 and 3 to the
dibismuthene product may be envisaged as shown in
Scheme 1. One (top pathway) involves initial cleavage of
Replacement of the chlorine atom by a hydrogen atom
results in 2 whose structural parameters suggest that it is
significantly less crowded than 1. The molecule is character-
ized by the presence of a twofold rotational axis of symmetry
through the bismuth atom which bisects the C-Bi-C angle
(Figure 2). The C-Bi-C angle is 114.9(3)8 which is 98 less than
Scheme 1. Two possible mechanisms for the transformation of Ar2BiH to
ˆ
ArBi BiAr (Arˆ 2,6-Mes2C6H3).
À
the bismuth aryl bond, followed by dimerization of the
Figure 2. Structure of 2 (only H attached to Bi is shown). Selected bond
lengths [Š] and angles [8]: Bi(1)-C(1) 2.314(7), Bi(1)-H(1) 1.94(2); C(1)-Bi-
C(1A) 114.9(3).
bismuth fragments to form a dibismuthane, which then
eliminates hydrogen to form the dibismuthene. The second
(bottom pathway) involves the concerted elimination of the
arene followed by rapid dimerization of the bismuthenes to
give the product. However the obervation of a deuterated
arene coproduct upon heating a solution of 2 or 3, combined
with the lack of visually observable H2 evolution, favors the
pathway involving the initial elimination of ArH (ArD).
À
the corresponding angle in 1. In addition, the Bi C bond
(2.314(7) Š) is slightly shorter than those in 1. Moreover, the
difference between the Bi-C(ipso)-C(ortho) angles is just 6.58
À
and the deviation of the Bi C(ipso) vector from the plane of
the C(ipso) ring is 12.48. Peaks which correspond to the
disordered hydrogen atom could be located at two disordered
positions with respect to the axis 1.94 Š distant from bismuth.
Although this distance is comparable to the 1.865 Š calcu-
lated for BiH3[9], the difference in the scattering power of
bismuth and hydrogen is such that the reliability of such
assignments is limited.[10]
Experimental Section
All work was carried out under anaerobic and anhydrous conditions.
1: A solution of Li(2,6-Mes2C6H3) (1.35 g, 4.21 mmol)[14] in toluene (20 mL)
was added dropwise to a suspension of BiCl3 (0.66 g, 2.1 mmol) in toluene
(10 mL) at about 08C. The mixture was warmed to room temperature and
stirred overnight. The mixture was filtered through celite and the solvent
was removed under reduced pressure. The residue was extracted with
hexane (80 mL) and the pale yellow solution was warmed to dissolve the
precipitates. Cooling to room temperature over a period of 2h afforded
X-ray diffraction quality, pale yellow crystals of 1. Yield 0.69 g, 36%. M.p.
À
The presence of a Bi H moiety in 2 is proven by a strong IR
absorption band at 1759 cmÀ1 which is in remarkably good
agreement with the theoretically predicted value (1760 cmÀ1)
for BiH3.[11] In contrast, the IR spectrum of 3 displayed no
absorbance at this frequency. Instead, a strong peak was
observed at 1260 cmÀ1 which is close to the value predicted
(1248 cmÀ1) on the basis of the difference in reduced mass
203 ± 2048C (decomp); IR: nÄ ˆ 288 cmÀ1 (Bi Cl); 1H NMR (300 MHz,
À
CDCl3): d ˆ 1.74 (s, 12H; o-CH3), 1.82(s, 12H; o-CH3), 2.33 (s, 12H; p-
3
CH3), 6.82(s, 8H; m-Mes), 7.17 (d, JH,H ˆ 7.8 Hz, 4H; m-C6H3), 7.33 (t,
3JH,H ˆ 6.9 Hz, 2H; p-C6H3); 13C {1H} NMR (75 MHz, C6D6): d ˆ 21.47 (p-
CH3), 22.48 (o-CH3), 22.50 (o-CH3), 128.6 (m-Mes), 129.1 (p-C6H3), 134.0
(m-C6H3), 136.5 (o-C6H3), 137.0 (o-Mes), 137.4 (o-Mes), 140.2( i-Mes), 149.6
(p-Mes), 201.5 (i-C6H3); satisfactory C,H analysis.
between 2 (Bi H) and 3 (Bi D). Unfortunately, 1H or
2H NMR spectra of 2 or 3 did not display signals that could
be assigned to the hydrogen or deuterium attached to
bismuth. Possibly, the large quadrupole moment of the 209Bi
nucleus (100%, I ˆ 9/2, quadrupole moment À0.4 Â
10À28 mÀ2) and the low local symmetry at the bismuth center
À
À
2: A solution of LiAlH4 (1.5 g, 39.5 mmol) in Et2O (30 mL) was added to a
rapidly stirred solution of 1 (3.41 g, 3.75 mmol) in toluene (40 mL) with
cooling to about 08C. The solution immediately became black on addition
of LiAlH4. Stirring was continued overnight at room temperature, where-
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upon the solvent was removed under reduced pressure. The residue was
extracted with C6H6 (50 mL), and the resultant red supernatant liquid was
decanted. The red solution was concentrated to about 5 mL at which point
a colorless solid precipitated. Hexane (50 mL) was added and the solution
was heated to dissolve the majority of the precipitates. The solution was
then decanted (608C) and allowed to cool slowly to room temperature
affording X-ray diffraction quality, colorless crystals of 2. Yield 0.96 g,
[11] P. Schwerdtfeger, L. J. Laakkonen, P. Pyykkö, J. Chem. Phys. 1992, 96,
6807.
[12] B. Twamley, C. D. Sofield, M. M. Olmstead, P. P. Power, J. Am. Chem.
Soc. 1999, 121, 3357.
[13] N. Tokitoh, Y. Arai, R. Okazaki, S. Nagase, Science 1997, 277, 78.
[14] K. Ruhlandt-Senge, J. J. Ellison, R. J. Wehmschulte, F. Pauer, P. P.
Power, J. Am. Chem. Soc. 1993, 115, 11353.
29.3%. M.p.: on heating the crystals became red at 1308C and purple at
1
1398C (decomp); IR: nÄ ˆ 1759 cmÀ1 (s, Bi H); H NMR (400 MHz, C6D6):
À
d ˆ 1.85 (s, 12H; o-CH3), 1.88 (s, 12H; o-CH3), 2.24 (s, 12H; p-CH3), 6.81,
3
3
6.82(8H; m-Mes), 6.84 (d, JH,H ˆ 7.2Hz, 4H; m-C6H3), 7.01 (t, JH,H
ˆ
7.6 Hz, 2H; p-C6H3); 13C {1H} NMR (100 MHz, C6H6): d ˆ 21.29 (p-CH3),
21.87 (o-CH3), 126.396 (m-C6H3), 128.306 (p-C6H3), 129.09 (m-Mes), 135.79
(o-Mes), 136.62( o-C6H3), 144.3 (i-Mes), 150.9 (p-Mes), 153.2( i-C6H3);
satisfactory C,H analysis.
Synthesis of (E)-a,b-Unsaturated Esters and
Amides with Total Selectivity Using Samarium
Diiodide**
3: LiAlD4 (0.25 g, 5.95 mmol) was added by using a solids addition tube to a
solution of 1 (5.27 g, 5.8 mmol) in toluene (40 mL) at about À788C. The
solution was allowed to warm slowly to room temperature overnight and
stirring was continued for 30 h by which time the supernatant liquid had
become red. This solution was filtered and the supernatant liquid was
pumped to dryness. The resulting solid was extracted with hexane/toluene
(3/1) (3 Â 80 mL). Colorless, X-ray diffraction quality, crystals of 3 were
obtained from these solutions upon cooling to À208C. Yield 0.52g, 10%.
Â
Â
Â
Â
Jose M. Concellon,* Juan A. Perez-Andres, and
Humberto Rodríguez-Solla
The development of methods for the stereoselective
formation of carbon ± carbon double bonds could be consid-
ered one of the most important challenges in organic syn-
thesis.[1] The synthesis of a,b-unsaturated esters[2] is generally
M.p.: on heating the crystals became red at 1328C and purple at 1398C;.
1
IR: nÄ ˆ 1260 cmÀ1 (s, Bi D); H NMR (400 MHz, C6D6): d ˆ 1.85 (s, 12H;
À
o-CH3), 1.88 (s, 12H; o-CH3), 2.24 (s, 12H; p-CH3), 6.81, 6.82(8H; m-Mes),
6.84 (d, 3JH,H ˆ 7.2Hz, 4H; m-C6H3), 7.01 (t, 3JH,H ˆ 7.6 Hz, 2H, p-C6H3); 13
C
[3]
ˆ
achieved by C C bond formation with Wittig, Horner±
{1H} NMR (100 MHz, C6D6): d ˆ 21.29 (p-CH3), 21.87 (o-CH3), 126.396 (m-
C6H3), 128.306 (p-C6H3), 129.09 (m-Mes), 135.79 (o-Mes), 136.62( o-C6H3),
144.3 (i-Mes), 150.9 (p-Mes), 153.2( i-C6H3); satisfactory C,H analysis.
Emmons,[4] Heck,[5] or Peterson[6] reactions, or with the Cope
rearrangement,[7] from acetylenic compounds[8] or a-sulfanyl-
ester derivatives.[9] However, in most of these papers, total
control of the stereoselectivity of the carbon ± carbon double
bond formation remained unresolved.[3a, b, d, 4±6c, 8a, 9b,c, 10] Some
methodologies are limited by their poor generality,[7, 8b, 9a, 11]
and other papers describe the preparation of a,b-unsaturated
esters in which the substitution pattern of the olefin is quite
simple (monosubstituted or 1,2-disubstituted).[3c, 6d] Only a
few examples of the synthesis of a-substituted a,b-unsatu-
Received: March 13, 2000 [Z14843]
[1] N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed.,
Butterworth-Heinemann, Oxford, 1987, Chapter 3.
[2] For example bismuthane, BiH3, is unstable at temperatures above
À608C and its chemistry has not been developed: S. M. Godfrey,
C. A. McAuliffe, A. G. Mackie, R. G. Pritchard, Chemistry of Arsenic,
Antimony and Bismuth (Ed.: N. C. Norman), Blackie-Chapman Hall,
London, 1998, Chapter 3.
ˆ
rated esters in which the C C bond is trisubstituted have been
reported.[12]
Recently, we described a stereoselective synthesis of (Z)-
vinyl halides by treatment of O-acetylated 1,1-dihaloalkan-2-
ols with samarium diiodide; this was the first general stereo-
selective b-elimination reaction promoted by SmI2.[13, 14] Here
we report a new methodology to obtain a,b-unsaturated esters
2 with total stereoselectivity, by treatment of the easily
available 2-halo-3-hydroxyesters 1 with samarium diiodide
[Eq. (1)]. We also describe preliminary results of the synthesis
of related a,b-unsaturated amides.
[3] J. Huheey, E. A. Keiter, R. L. Keiter, Inorganic Chemistry Principles
of Structure and Reactivity, 4th ed., Harper Collins, New York, 1993,
AppendixE; W. E. Dasent Inorganic Energetics, 2nd ed., Cambridge
University Press, Cambridge, 1982; J. F. Liebman, J. A. M. Simoes,
S. W. Slayden; ªThermochemistry of organo-arsenic, antimony and
bismuth compoundsº: The Chemistry of organic arsenic, antimony and
bismuth compounds (Ed.: S. Patai), Wiley, Chichester, 1994, Chap-
ter 4, pp. 153 ± 168.
[4] Crystal data for 1 and 2 at 90 K with MoKa radiation (l ˆ 0.71073 Š): 1,
a ˆ 12.3231(8), b ˆ 20.3292(14), c ˆ 16.137(11) Š, b ˆ 102.977(2)8,
Z ˆ 4, space group P21/n, R1 ˆ 0.0596 for 3994 data with I > 2(s)I; 2,
a ˆ 21.0073(12), b ˆ 44.156(3), c ˆ 8.1877(5) Š, Z ˆ 8, space group
Fdd2, R1 ˆ 0.046 for 2402 data with I > 2s(I). Crystallographic data
(excluding structure factors) for the structures reported in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-143879 and CCDC-
143880. Copies of the data can be obtained free of charge on
application to CCDC, 12Union Road, Cambridge CB21EZ, UK (fax:
(‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
When a solution of SmI2 in THF was added dropwise to
several 2-halo-3-hydroxyesters 1 (prepared by reaction be-
tween the corresponding lithium enolates of a-haloesters and
Â
Â
Â
[*] Dr. J. M. Concellon, Dr. J. A. Perez-Andres, H. Rodríguez-Solla
Â
Â
Departamento de Química Organica e Inorganica
Facultad de Química, Universidad de Oviedo
33071 Oviedo (Spain)
[5] D. M. Hawley, G. Ferguson, J. Chem. Soc. A 1968, 2059.
[6] B. Murray, J. Hvoslef, H. Hope, P. P. Power, Inorg. Chem. 1983, 22,
3421.
[7] X.-W. Li, G. Lorberth, W. Massa, S. Wocadlo, J. Organomet. Chem.
1995, 485, 141.
[8] K. H. Whitmire, D. Labahn, H. W. Roesky, M. Noltemeyer, G. M.
Sheldrick, J. Organomet. Chem. 1991, 402, 55.
[9] K. Balasubramanian, D. Dai, J. Chem. Phys. 1990, 93, 1837.
[10] Attempts to grow crystals suitable for neutron diffraction studies are
in progress.
Fax : (‡349)8-510-34-46
E-mail: jmcg@sauron.quimica.uniovi.es
Â
[**] We thank the II Plan Regional de Investigacion del Principado de
Â
Asturias (PB-PGI99-01) and the Ministerio de Educacion y Cultura
Â
(PB97-1278) for financial support. J.M.C. thanks Carmen Fernandez
for her help. H.R.S. thanks the Universidad de Oviedo for
predoctoral fellowship.
a
Supporting information for this article is available on the WWW under
http://www.wiley-vch.de/home/angewandte/ or from the author.
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