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Bis(hypersilyl)tin and Bis(hypersilyl)lead Two Electron-Rich Carbene Homologs.

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4: In a similar fashion, a solution of 1-bromo-1.12-dicarha-closu-dodecaborane(l2)
Bis(hypersily1)tin and Bis(hypersilyl)lead,
Two Electron-Rich Carbene Homologs""
(100 mg, 0.45 mmol) in methyl triflate (OSmL, 4.5 mmol) and triflic acid (0.1 mL,
0.06 mmol) was heated under reflux for 10 h. Workup as for 1 afforded 4 as a white
solid (145 mg, 89%). M.p. 251 "C (decomp) (sealed capillary); ' H N M R (360 MHz.
a r'l~Wilhelm
and Wolfgang
C { ' H J N Klinkhammer*
CDCI,):6 =2.11 (brs, ~ H . C H ) . ~ . O ~ , ~ . ~ ~ ( ~ ~ ~ , ~ X ~ ~ H , B C H ,K
(90.5 MHz. CDCI,): 6 =76.2 (CH). 72.7 (CBr), -2.3. -3.6 (vbr, BCH,); "B
Dedicated to Professor Peter I. Paetzold
N M R (160.5 MHz, Et,O): d = -7.2, -9.7 (5B. BCH,); HRMS (El) (miz),calcd.
on the occasion of his 60th birthday
364.2591. found 364.2602 ( M ' ) .
Received: January 12, 1995 [Z76291E]
German version: Angew. Chem. 1995, 107, 1470-1473
Keywords: alkylations . boron compounds . carboranes . electrophilic substitutions
[ I ] a) V. I. Bregadze, Chem. Rev. 1992. 92, 209-223; h) V. V. Grushin, V. I. Bregadze. V. N. Kalinin, J Organornet. Chem. Lib. 20 1988, 20. 1-68. and references therein.
[2] R. N. Grimes. Curhorunur,Academic Press, New York, 1970 pp. 54-180, and
references therein.
[3] F A. Gomez, M. F. Hawthorne, J Org. Chen~.1992. 57, 1384-1390.
[4] a) X. Yang, W Jiang, C. B. Knobler, M. F. Hawthorne, J. A m . Chen?.Sor. 1992,
114,9719-9721; b) J. Muller, K. BaSe,T. F. Magnera, J. Michl, ibid. 1992, 114,
9721 -9722.
(51 a) X. Yang. C. B. Knohler. Z. Zheng. M. F. Hawthorne, J. An?. Chem. SOC.
1994,116,7142-71 59; b) I. T. Chizhevsky, S. E. Johnson. C. B. Knohler, F. A.
Gomez, M. F. Hawthorne, ibid. 1993, f15.6981-6982; c) W. Clegg, W. R. Gill,
J. A. H. McBride, K. Wade, A n p . Clwn?. 1993, 105, 1402-1403; Angerv.
Chen?.Int. Ed Engl. 1993. 32, 1328-1329.
[6] a) R. Koster, G . W. Rotermund, Tetruhedron Lelr. 1964, 1667-1670; b) P.
Binger. ihid. 1966. 2675-2680.
171 a ) V. 1. Stanko. A . I. Klimova, A. N. Kashin. 211. Ohslrch. Khim. 1969, 39,
1895; h) V. 1. Stanko. G . A. Anorova. T. V. Klimova, ihid. 1969, 39. 21432144; c) V. I. Stanko. A. I. Klimova, hid. 1969, 39, 1896.
181 J. PleSek, Z. PlzLk, J. Stuchlik, S. Heimanek. Collect. Czech. Cheni. Commun.
1981.46, 1748-1763.
[9] L. 1. Zakharkin. V. N. Kalinin, L. S. Podvisotskaya. h.Akud. Nuuk SSSRSer.
Khim. 1968.2661.
[lo] Crystallographic data for 1: C,,H,,B,,, M = 312.60, cubic. space group Pu3,
a = 12.859(1)
V = 2126
Z = 4 ( 1 6 molecule per asymmetric unit),
= 0.98 gcm-3. T = 25 C. p = 3.0 cm-'. Data were collected on a Synto a maximum
tex PT diffractometer using Cu,, radiation ( i = 1.5418
20 = 11 5 , giving 484 unique reflections, of which 370 reflections with I > 3a(I)
were retained for qtructure analysis. The data were corrected for Lorentz and
polarization effects and for secondary extinction but not for absorption. The
structure was solved by direct methods. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included in calculated positions. The
final discrepancy index was R = 0.085, R, = 0.110. Because of the high symmetry required by this space group for the molecule. there is disorder. and one
of the two unique icosahedral atoms has been described as carbon with 1/3
occupancy and boron with 2i3 occupancy and with both carbon and boron
constrained to the same values of .x, y. z , and displacement parameters. The
largest peak on a final difference electron density map was 0.9 e k ' . Crystallographic data for 2: C,,H,,B,,, M = 284.54, orthorhomhic. space group
Ccmh (No. 64, standard setting Ccmu). ( I =13.930(3), b =15.440(3), c =
9.089(3)& V=1954.9(8)A3. 2 = 4 , pL,,,,=0.97gcm-',
T=25'C. p =
2.90 cm-'. Data were collected on a Rigaku AFC5 diffractometer using Cu,,
radiation ( i = 1.5418A) to a maximum 20 =110", giving 650 unique reflections, of which 488 reflections with I > 3a(I) were retained for structure analysis. The data were corrected for Lorentz and polarization effects and for
secondary extinction hut not for absorption. The structure was solved by direct
methods. All non-hydrogen atoms were refined anisotropically. Methyl hydrogen atoms were included in calculated positions. and the carboranyl hydrogen
atom was included in the located position. The final discrepancy index was
R = 0.077, R, = 0.119. The largest peak on a final difference electron density
map was 0.1 I e k ' . Further details of the crystal structure investigations may
he obtained from the Director of the Cambridge Crystallographic Data Centre.
12 Union Road, GB-Cambridge CB2 1EZ (UK), on quoting the full journal
[ I l l W. Jiang, C. B. Knobler, C. E. Curtis, M. D. Mortimer. M. F. Hawthorne.
Inor,q Chem., in press
[I21 R. R. Srivastava, D. S. Wilbur. Abstracts of Papers. 208th National Meeting
of the American Chemical Society, Washington DC, American Chemical Soci-
ety. Washington DC. 1994, p. 208.
Molecular compounds of divalent tin and lead (stannylenes
and plumbylenes, respectively) with solely electropositive 0bonded substituents tend to oligomerize or to disproportionate,
respectively. It has previously been possible to stabilize such
systems by introduction of sterically demanding groups or additional coordinative saturation of the central atom. Typical examples are bis(trimethylsilyl)methyl and bis(trimethylsily1)amino derivatives,". stannylenes and plumbylenes bearing
aryl s u b s t i t ~ e n t s ,41[ ~or~intermolecularly donor-stabilized compounds such as Sn[P(CMe,),],[5a1 or Sn[E(SiMe,),], (E = P,
As) .[5b, Furthermore, several heteroleptic plumbylenes and
stannylenes are known.[61In the solid state the homoleptic stannylenes are either dimeric or monomeric, in the gas phase those
studied to date have only been monomeric. The corresponding
lead compounds were observed as monomers in all aggregate
statesL7]Stannylenes and plumbylenes with stronger electropositive substituents were to date unknown. The synthesis and the
structural characterization of two such derivatives, namely
bis(hypersily1)tin ( l ) ,and bis(hypersily1)lead (2), is the subject
of this communication.
Geanangel et al. reported in 1992 on the attempt to synthesize
2 from lead@) chloride and the thf solvate of hypersilyllithium.
However, in the course of a redox process they obtained
1,l,I ,4,4,4-hexamethyl-2,2,3,3-tetrakis(trimethylsi~yl)tetrasi~ane
(3) and lead only.['] It also proved not possible to synthesize the
corresponding stannylene 1 by this
however, a
product that could be described as an LiCl adduct of 1 was
isolated, namely the heteroleptic lithium stannanide 4.[9b1
Recently, during the synthesis of a hypersilylthallium compound we avoided similiar problems by replacing thallium chloride with thallium bis(trimethylsilyl)amide.['ol Thus, we tried to
apply the same method to synthesizing the desired tin(I1) and
lead@) compounds.
If lead bis[bis(trimethylsilyl)amide] is treated with the hypersilyl derivative of a heavy alkali metal["' in n-pentane at
-6O"C, a clear blue solution is produced together with an al-
:C) VCH K~rlugsgesellschafimbH, 0-69451 Weinheim, 1995
Dr. K. W. Klinkhammer, Dr. W. Schwarz
Institut fur Anorganische Chemie der Universitat
Pfaffenwaldring 55, D-70550 Stuttgart (Germany)
Telefax: Int. code + (711) 685-4241
e-mail: karl.kiinkhammer(u;
We thank Prof. Dr. G. Becker for his splendid support. - For the term "hypersilyl" see citation 5 in ref. [lo].
0570-0833/95/1212-f334 $ 10.00+ .25/0
Angew. Chem. Inr. Ed. Engl. 1995, 34, No. I 2
most colorless crystal paste. From this solution black, coffin-lid
shaped crystals precipitate on concentration and cooling to
- 60°C.
The correct elemental analysis and the molecular ion identified as the heaviest ion by mass spectrometry confirm the identity of the compound as 2. 'H, and 13CNMR spectra of freshly
prepared solutions of the diamagnetic compound show the expected singlets. After a short while, however, one observes the
appearance of further resonances, which according to reference
samples originate mostly from silane 3. An absorption measurement in the UV/Vis range showed in addition to some intensive
bands which are also found in other hypersilyl derivatives in the
areas below 350 nm, two further, less intensive absorptions at
578 (c = 620) and 1056 nm ( E = 370).
A reaction carried out in an analogous way with tin
bis[bis(trimethylsilyl)amide] gave initially a green, and then later
a violet-brown solution[' 21 from which, small black quadratic
crystal platelets crystallized at - 60 "C. Here too the elemental
analysis gave correct results and the molecular ion could be
identified by mass spectrometry as that for 1. While as expected
a singlet appears in the ' H and 13C NMR spectra of the diamagnetic'I3] compound, it was not possible to obtain any satisfying
'"Si or "9Sn NMR spectra in the temperature range between
-60 and + 30°C. Therefore, a t present it is not possible to
make any statements concerning aggregation in solution by
N M R spectroscopy. The UV/Vis spectrum is similiar to that of
2. However, the absorption maxima (559 nm ( E = 580) and 838
nm (t: = 120)) are shifted to shorter wavelengths as could be
expected. As no further absorptions occur even with more concentrated samples, the tin compound 1 is assumed to be largely
monomeric in solution as is the lead compound 2. A cryoscopic
molar mass determination confirmed these presumptions.
The crystal structure analyses carried out to elucidate the
constitution of the compounds show them to be the expected
bis(hypersily1)lead (2) and bis(hypersily1)tin (1). While the lead
compound is monomeric,[7a1bis(hypersily1)tin dimerizes in the
solid state to the distannene, tetrakis(hypersily1)ditin (Sn-Sn)
The molecules of compound 2 (Fig. I), like the other structurally characterized molecular lead@) compounds, are bent
(5),[15] the only structurally
characterized silyl-substituted
lead compound to date.
That overloading of the cen-
tral atom in 2 with the very
voluminous hypersilyl substituents has a distinct influence
on the geometry of the molecule can be recognized by a considerable tilting of this substituent towards the Pb-Si bond axis.
Thus, in addition to two Pb-Si-Si angles compressed to nearly
90", one angle is widened up to 130". A similiar although less
pronounced variance is observed for the Si-Si-Si angles.
The Si,Sn-SnSi, backbone (Fig. 2 a) of the bis(hypersily1)tin
dimer (l), (Fig. 2 b) shows a unique strongly distorted trans-
Fig. 2. a) Newman projection of the Sn,Si,-framework of ( I ) , . b) Molecular structure of(l)2in the crystal (thermal ellipsoids at 50% probability level) Selected bond
lengths [pm] and angles ["I: Snl-Snl' 282.47(6), Snl-Sil 266.67[11). Snl-Si2
267.81 (1I ) , Sil-Snl -Snl' 108.25(3), Si2-Snl-Snl' 123.25(3),Sil-Snl-Si2 120.46(4),
Snl-SiZ-Si21 106.19(5), Snl-Si2-Si22 131.88(6), Snl-Si2-Si23 9Y.78(5). Snl-SilSill 112.06(5). Snl-Sil-Sil2 115.51(5), Snl-SiI-SilS 112.35[5)
Fig. 1 Molrculiir structureof2in thecrystal [thermalellipsoidsat 50% probability
level). Selected bond lengths [pm] and angles ['I of one of four symmetry-independent molecules: Pbl -Sill 270.0(3), Pbl-Si12 270.4(3), Sill-Pbl-Sil2 113.56(10),
Pbl-Sil N i l 3 9Y h ( 2 ) . Pbl-Silt-Sil4 104.8(2), Pbl-SilI-Sil5 125.0(2). Pbl-SillSi16 129.2(2). I'hl -Sil2-S117 98.3(2), Pbl -Sil?-SilX 101.62(2).
monomers. The Si-Pb-Si angles determined lie between 113.6
and 115.7' and are therefore considerably more obtuse than in
other plumbylenes181 studied so far. The Pb-Si bond lengths
vary only slightly between 268 and 271 pm and are about 5 pm
longer than those in bis[ (hypersilyl)diphenyllead](Ph -Pb)
bent conformation (crystallographic C2 symmetry). The dihedral angle ( T ) between the planes defined by a tin atom and the
central silicon atoms of the bound hypersilyl group is 63.2", the
angle ( K ) between these planes and the Sn-Sn bond 28.6". In the
only structurally characterized stannylene dimer to date,
the bis(trimethylsily1)methyl
derivative 6,"' Lappert et a1
observed the theoretically exp e ~ t e d [ ~undistorted
transbent arrangement ( T = 0';
K = 41"). Torsions about the
central element -element bond, although considerably less pronounced, have so far only been detected in related sterically
strongly loaded alkenes, disilenes, and digermenes." 61 As exis longer than in 6 and lies
pected, the Sn-Sn distance in (l)217b1
with 282 pm in the range of "normal" Sn-Sn single bonds in
distannanes." 'I The Sn-Si bond lengths and the Si-Sn-Si angle
in (1)2 do not differ much from the values of the lithium stannanide 3 synthesized by Cowley et al.[9b1
E-xperimental Procedure
1 ' A solution of Sn[N(SiMe,),], (1.53 g, 3.49 mmol) in n-pentane a t -60°C was
quickly added to a thoroughly stirred suspension of KSi(SiMe,), (2.00 g,
6 97 mmol) [1I] in n-pentane (20 mL). The resulting lime green mixture was stirred
for 1 h at this temperature and then for 30 min at 0 ' C. The resulting violet-brown
solution was pipetted off from the colorless crystal paste and concentrated to 10 mL
by removal of the solvent under vacuum. After 15 h at - 60 "C black crystal platelets
of (I), precipitated from the solution (1.22g. 1.99 mmol. yield 57%). Decomp.
1 3 0 ' C ; correct elemental analysis; ' H N M R (250.133 MHz, [DJbenzene, 27 C.
TMS): d = 0.60, 'J(Si,H) = 6.1 Hz; I3C N M R (62.896 MHz. [DJbenzene, 27'C,
TMS): 6 = 5.5; EI-MS (70 eV; sample 360 K ; source 510 K): m / r (Yo):
73 (100)
731, 614 (1.3) [ M i ] .
[Me,Si+], 247 (7) [(Me,Si),Si+]. 541 (2.7) [M'
2: The reaction was carried ont in a way similar to that for (I), [KSi(SiMe,), (2.00 g,
6.97 mmol) and Pb[N(SiMe,),], (1.84 g, 3.49 mmol], however, because ofthe better
solubility of the product the solution should be concentrated to 5 mL. After 15 h at
-60°C. black. coffin-lid shaped crystals of 2 (1.83 g, 2.60 mmol. 75%) were isolated. Decomp. 1 W C : correct elemental analysis; ' H N M R (250.133 MHz,
[DJhenzene. 27 C. TMS): d = 0.54. 'J(Si,H) = 6.6 Hz; I3C NMR (62.896 MHz.
[DJbenzene. 27 'C. TMS): d = 8.5. 'J(Si.C) = 44.5; EI-MS (70eV; sample 350 K ;
source 400 K): mi: (%). 73 (loo), 247 (19), 455 (4) [(Me,Si),SiPb'], 702.2 (1.7)
Received: February 1. 1995 [Z77061E]
German version. Angew. Chem. 1995. 107. 1448-1451
Keywords: distannenes . hypersilyl derivatives plumbylenes .
[l] T. Fjeldberg, A. Haaland, B. E. R. Schilling, M. F. Lappert, A. J. Thorne.
J Chem. Soc. Dalton Trans. 1986, 1551.
[2] C. D. Schaeffer. Jr.. J. J. Znckerman. 1 Am. Chem. Soc. 1974. 96, 7160; D. E.
Goldberg, D. H. Harris, M. F Lappert, K. M. Thomas, J . Chem. Suc. Chem.
Commun. 1976, 261; M. F. Lappert, P. P. Power, M. J. Slade. L. Hedberg.
V. Schomaker, ihid. 1979, 369.
[3] H. Griitzmacher, H . Pritzkow, F. T. Edelmann, 0rganome.tuNic.v1991. 10, 23;
S. Brooker, J.-K. Buijink, F. T. Edelmann, ihid. 1991. 10, 25.
[4] M. Weidenbruch. J. Schlaefke, A. Schdfer. K. Peters, H. G . von Schnering.
H. Marsmann. Angew. Chem. 1994, 106, 1938; Angew. Chem. In!. Ed. Enxl.
1994,33. 1846.
[5] a) W-W. du Mont. H.-J. Kroth, Angew Chem. 1977,89,832; Angew. Chem. Inr.
Ed. Engl. 1977, 16, 792; b) S. C. Goel. M. Y Chiang, D. J. Rauscher, W. E.
Buhro, J Am. Chem Soc. 1993. f15,160; c) M. Westerhausen, M. M. Enzelberger, W Schwarz, J Organomel. Chem. 1995, 485, 185.
[6] Review: M. F. Lappert, Main Group M e [ . Chem. 1994, 17, 183.
171 For a b initio calculations on the stability of dimers see for example: a) G. J.
Trinquier. J. Am. Chrm. Soc. 1990. ff2.1039; b) T. L. Windus, M. S. Gordon,
L Am. Chem. Soc. 1992. 114.9559.
[XI S. P. Mallela, 1. Bernai, R. A. Geanangel, Inorg. Chem. 1992. 31, 1626.
[9] S. P. Mallela and R. A. Geanangel claimed the isolation of a colorless(!) T H F
adduct of 1 [fnorg. Chem. 1990, 29, 35251. Our own results (1 forms a brown
T H F solution) and the reported extreme Il9Sn highfield shift led us to doubt
its identity. b) A. A. Arif, A. H. Cowley, T. M. Elkins, J. Orgunomet. Chem.
1987,325, C11.
[lo] S. Henkel, K. W. Klinkhammer, W. Schwarz, Angew. Chrm. 1994, 106. 721 ;
Angew. Chem. I n t . Ed. Engl. 1994, 33. 681. For earlier usage of bis(trimethy1si1yl)amides in the syntheses of stannylenes and plumbylenes see for example
ref. [6].
[ I l l K. W. Klinkhammer, W. Schwarz. Z. Anorg. Allg. Chem. 1993, 619, 1777;
K. W. Klinkhdmmer, W, Schwarz, J A m . Chem. Soc., submitted.
[12] The reaction of bis[bis(trimethylsilyl)amides] with hypersilanides is strongly
dependent on the temperature and the solvent. Larger quantities of unknown
paramagnetic compounds are formed in pentaue above - 30 "C. In the presence of toluene additional interesting products are found: At temperatures
below - 30°C mainly solvated alkali metal tris[tris(trimethylsilyl)silyl]stannanides or -plumbanides are obtained in addition to 1 and 2, respectively. At
higher temperatures the main products are alkali metal derivatives of benzylbis[tris(trimethyIsilyl)silyl]stanndne or -plumbane.
[13] a) How much distannene (I), is already present in the triplet state at room
temperature remains an unclarified question. In the EPR spectrum of the solid.
no triplet resonances were observed in the temperature range between 4 and
300 K. However, ah initio calculations performed on the model system
reveal only a small energy difference of about
25 kJmol-' in favor of the singlet state [13b] in the observed Si,Sn-SnSi,
backbone conformation in the solid, so that a measurable population of the
triplet state at room temperaturecannot be excluded. b) MP2; quasi-relativistic
pseudopotentials on Sn(46e core) and Si(l0e core) and appropriate basis sets
from G . Igel-Mann. H. Stoll. H. Preuss, Mul. Phys. 1988, 65, 1321; basis sets
for H from T. H. Dunning, J C k m . Phys. 1970, 19, 553.
[141 Crystal structure analyses: (I),. a = 27.884(3) h =13.106(1), c = 23.173(2) A,
B =126.203(6)', V = 6 8 3 3 3 1 ) A3, Z = 4. monoclinic. space group C2/c (no.
151, F(000) = 2592, pralcd
= 1.194 gem-', p = 1.03 mm-'. four-circle diffrac-
VCH Verlagsgesellschaft mhH, 0-69451 Weinheim, 1995
tometer P2, (Syntex), 3 ' < 2 0 < 5 6 . Mo,,. Wyckoff scan, T = -100°C.
N(hk4 = 8519. from which 7364 > -lu(I), Lorenz- and polarization correction. no absorption correction. The structure was solved by direct methods
(SHELXS-86) refined with full-matrix least squares based on Fz values
(SHELXL93) ((l), surprisingly crystallizes isotypically t o tetrakis(hypersilyl)dithallium(Tl- T / )which comprises two valence electrons less [lo]). Sn, Si,
and C atoms were refined anisotropically; the hydrogen atoms, except those
which belong to a disordered trimethylsilyl group were found und their positional parameters were freely refined. The tin atom is slightly disordered; the
occupation factor for the major position refined to 0.9812(9). 433 parameters.
57 restraints. residual electron density: 0.776,'-0.621 e k 3 , R1[F0>4u(Fn)]=
0.044. ~ R 2 = 0 . 0 9 1 , GOF=1.10. 2: u=16.222(3), h=22.130(3). C =
22.380(4) A, I= 110.61(3), /I =100.57(3), y = 100.35(3)". V=7127(1) A3.
2 = 8. triclinic. space group PT (no. 2). F(000) = 2848. pc4,ce= 1.309 gcm-'.
p = 5.04 m m - l . four-circle diffractometer P2, (Syntex), 6.5 < 20 < 45',
N(hk[) =18628, from which
Wyckoff scan, T = -1OO'C.
18406 > -3u(1). Lorenz and polarization correction. empirical absorption
correction (IJscan, inin.imax. transmission: 0.63/0.99). All the examined crystals were twinned about (1 0 7) by pseudomeroedry. In the individual used for
the final structure solution, the refined volume proportion of the minority
component was however very small [0.0131(5)]. The structure was solved by
direct methods (SHELXS-86) refined with fullmatrix least squares based on 6:
values (SHELXL93). Pb. SI.and C atoms were refined anisotropically; the
hydrogen atoms were calculated at ideal positions and included in the refinement according to a ridmg model (AFIX 137) with fixed isotopic displacement
parameters. In two out of four symmetry independent molecules the lead atom
shows a positional disorder which was carried by a split model calculation.
1068 parameters, 64 restraints. residual electron density: 1.874/-1.074 e k 3 .
RI[F, > 4a(Fn)] = 0.067, uR2 = 0.141, G O F =1.10 Further details of the
crystal structure investigations may be obtained from the Fachinformationszentrum Karlsruhe. D-76344 Eggenstein-Leopoldshafen (Germany), on quoting the depository numbers CSD-141531 (1)2 and CSD-141530 (2).
[15] S. P. Mallela. R. A. Geanangel, Inorg. Chem. 1993. 32. 602.
[I61 For examples see: M. Kira, T. Maruyama. C. Kabuto, K.Ebdta, H. Sakurai.
Angew. Chem. 1994,106.1575; Angew. Chem. Int. Ed. Engl. 1994.33.1489, and
references therein.
[I71 See for example: S. P. Mallela, R. A. Geanangel, Inurg. Chem. 1993. 32. 5623.
Transition Metal Catalyzed Diboration
of VinyIarenes**
R. Thomas Baker,* Paul Nguyen, Todd B. Marder,*
and Stephen A. Westcott*
Dedicated to Dr. George W Parshall
on the occasion qf his 65th birthday
Following the discovery of rhodium-catalyzed hydroboration
of alkenes and alkynes,"] subsequent studies have investigated
analogous metal-mediated additions of boron- heteroatom
bonds.['] Although tetraalkoxydiboranes cannot be added to
C-C multiple bonds by conventional reaction^,'^] a report published by Suzuki et al. in 1993 described a platinum-catalyzed
variant using a bis(pinaco1ate) derivative.[2d1 Unfortunately,
['I Dr. R. T. Baker
Central Research and Development
Dupont Science and Engineering Laboratories
Experimental Station. Wilmington. DE 39880-0328 (USA)
Telefax: Int. code + (302)695-8281
Prof. T. B. Marder, P. Nguyen
Department of Chemistry, University of Waterloo
Waterloo, Ontario N2L 3G1 (Canada)
Dr. S. A. Westcott
Department of Chemistry. University of North Carolina
Chapel Hill. N C 27514 (USA)
Contribution No. 6936 from Central Research and Development. Dupont
Science and Engineering Laboratories. We thank Todd W. Hunt. John Nguyen,
and Fred Davidson for expert technical assistance. T. B. M. acknowledges
support from the Natural Sciences and Engineering Research Council
(NSERC) of Canada. P. N. and S. A. W. thank the NSERC for their respective
predoctoral and postdoctoral fellowships.
0570-0833jY5/12f2-1336 3 10.00+ ,2510
Angew. Chem. In!. Ed. Engl. 1995, 34, No. f 2
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