Transition-metal-promoted reactions of boron hydrides. 17.1 Titanium-catalyzed decaborane-olefin hydroborations

Article abstract of DOI:10.1021/ja011432s

The titanium-catalyzed hydroboration reactions of decaborane with a variety of terminal olefins have been found to result in the exclusive, high-yield formation of monosubstituted decaborane 6-R-B₁₀H₁₃ products, arising from anti-Markovnikov addition of the cage B6-H to the olefin. The titanium-catalyzed reactions are slow, often less than one turnover per hour; however, their high selectivities and yields coupled with the fact that they are simple, one-pot reactions give them significant advantages over the previously reported routes to 6-R-B₁₀H₁₃ compounds. The catalyst also has extended activity with reactions carried out for as long as 13 days, showing little decrease in reactivity, thereby allowing for the production of large amounts of 6-R-B₁₀H₁₃. The titanium-catalyzed reactions of decaborane with the nonconjugated diolefins, 1,5-hexadiene and diallylsilane, were found to give, depending upon reaction conditions and stoichiometries, high yields of either alkenyl-substituted 6-(CH₂=CH(CH₂)₄) -B₁₀H₁₃ (4) and 6-(CH₂=CHCH₂SiMe₂ (CH₂)₃)-B₁₀H₁₃ (5) or linked-cage 6,6′-(CH₂)₆- (B₁₀H₁₃)₂ (6) and Me₂Si(6-(CH₂)₃- B₁₀H₁₃)₂ (7) compounds, respectively. The unique tetra-cage product, Si(6-(CH₂)₃-B₁₀H₁₃)₄ (8), was obtained by the catalyzed reaction of 4 equiv of decaborane with tetraallylsilane. Sequential use of the titanium catalyst and previously reported platinum catalysts (PtBr₂ or H₂PtCl₆·6H₂O with an initiator) provides an efficient pathway to asymmetrically substituted 6-R-9-R′-B₁₀H₁₂ species. The structures of compounds 5, 6, and 8, as well as a platinum derivative, (PSH⁺)₂-commo-Pt- [nido-7-Pt-8-(n-C₈H₁₇₊) B₁₀H₁₁]₂^2-, of 6-(n-octyl)decaborane have been established by single-crystal crystallographic determinations.

Full text of DOI:10.1021/ja011432s

12222
J. Am. Chem. Soc. 2001, 123, 12222-12231
Transition-Metal-Promoted Reactions of Boron Hydrides. 17.1
Titanium-Catalyzed Decaborane-Olefin Hydroborations
Mark J. Pender, Patrick J. Carroll, and Larry G. Sneddon*
Contribution from the Department of Chemistry, UniVersity of PennsylVania,
Philadelphia, PennsylVania 19104-6323
ReceiVed June 11, 2001
Abstract: The titanium-catalyzed hydroboration reactions of decaborane with a variety of terminal olefins
have been found to result in the exclusive, high-yield formation of monosubstituted decaborane 6-R-B10H13
products, arising from anti-Markovnikov addition of the cage B6-H to the olefin. The titanium-catalyzed
reactions are slow, often less than one turnover per hour; however, their high selectivities and yields coupled
with the fact that they are simple, one-pot reactions give them significant advantages over the previously
reported routes to 6-R-B10H13 compounds. The catalyst also has extended activity with reactions carried out
for as long as 13 days, showing little decrease in reactivity, thereby allowing for the production of large
amounts of 6-R-B10H13. The titanium-catalyzed reactions of decaborane with the nonconjugated diolefins,
1,5-hexadiene and diallylsilane, were found to give, depending upon reaction conditions and stoichiometries,
high yields of either alkenyl-substituted 6-(CH2dCH(CH2)4)-B10H13 (4) and 6-(CH2dCHCH2SiMe2(CH2)3)-
B10H13 (5) or linked-cage 6,6′-(CH2)6-(B10H13)2 (6) and Me2Si(6-(CH2)3-B10H13)2 (7) compounds, respectively.
The unique tetra-cage product, Si(6-(CH2)3-B10H13)4 (8), was obtained by the catalyzed reaction of 4 equiv of
decaborane with tetraallylsilane. Sequential use of the titanium catalyst and previously reported platinum catalysts
(PtBr2 or H2PtCl6‚6H2O with an initiator) provides an efficient pathway to asymmetrically substituted 6-R-
9-R′-B10H12 species. The structures of compounds 5, 6, and 8, as well as a platinum derivative, (PSH+)2-
commo-Pt-[nido-7-Pt-8-(n-C8H17)B10H11]22-, of 6-(n-octyl)decaborane have been established by single-crystal
crystallographic determinations.
The development of new, systematic ways to functionalize
routes to both monoalkyl and monoalkenyl decaboranes, as well
as new types of decaborane linked-cage compounds.5
polyboranes, such as decaborane B10H14, with organic substit-
uents has been of great recent interest because of the emerging
uses2 of a variety of organo-polyboranes in such diverse
applications as boron neutron capture agents, noncoordinating
anions, extractants for radioactive wastes, and inorganic polymer
components. We have previously shown that late transition metal
complexes can be used to catalyze the reactions of certain
polyboranes with olefins and acetylenes to provide excellent
routes to alkyl- or alkenyl-substituted products.1 For example,
either chloroplatinic acid or platinum(II) bromide can be used
to catalytically hydroborate terminal olefins with decaborane
to yield 6,9-R2B10H12 derivatives in high yield.3
Early transition metal complexes have also recently been
found to catalyze olefin and acetylene hydroborations with
monoboranes, such as catecholborane (HBCat) or pinacol-
borane.4 For example, He and Hartwig reported4a that Cp2Ti-
(CO)2 catalyzes the hydroboration reactions of HBCat with
acetylenes, while Cp2TiMe2 is an effective catalyst for reactions
of HBCat with olefins. These reports suggested that early-metal
metallocene complexes might also be useful for catalyzing
reactions involving polyboranes, with the possibility that new
types of activities and selectivities might be observed. We report
here our discovery of titanium-catalyzed decaborane-olefin
hydroboration reactions that, in contrast to the previous platinum-
catalyzed decaborane-olefin hydroborations, provide excellent
Experimental Section
All manipulations were carried out using standard high-vacuum or
inert-atmosphere techniques as described by Shriver and Drezdzon.6
Materials. Cp2Ti(CO)2 was purchased from Strem and used as
received. Cp2TiMe2 was prepared according to the literature procedure.7
(4) For examples, see: (a) He, X.; Hartwig, J. F. J. Am. Chem. Soc.
1996, 118, 1696-1702. (b) Hartwig, J. F.; Muhoro, C. N.; He, X.;
Eisenstein, O.; Bosque, R.; Maseras, F. J. Am. Chem. Soc. 1996, 118,
10936-10937. (c) Hartwig, J. F.; Waltz, K. M.; Muhoro, C. N.; He, X.;
Eisenstein, O.; Bosque, R.; Maseras, F. In AdVances in Boron Chemistry;
Siebert, W., Ed.; Royal Society of Chemistry: London, 1997; pp 491-
502. (d) Muhoro, C. N.; Hartwig, J. F. Angew. Chem., Int. Ed. Engl. 1997,
36, 1510-1512. (e) Muhoro, C. N.; He, X.; Hartwig, J. F. J. Am. Chem.
Soc. 1999, 121, 5033-5046. (f) Hartwig, J. F.; Muhoro, C. N. Organo-
metallics 2000, 19, 30-38. (g) Motry, D. H.; Smith, M. R., III. J. Am.
Chem. Soc. 1995, 117, 6615-6616. (h) Motry, D. H.; Brazil, A. G.; Smith,
M. R., III. J. Am. Chem. Soc. 1997, 119, 2743-2744. (i) Lantero, D. R.;
Ward, D. L.; Smith, M. R., III. J. Am. Chem. Soc. 1997, 119, 9699-9708.
(j) Lantero, D. R.; Miller, S. L.; Ch, J.-Y.; Ward, D. L.; Smith, M. R., III.
Organometallics 1999, 18, 235-247. (k) Pereira, S.; Srebnik, M. Orga-
nometallics 1995, 14, 3127-3128. (l) Pereira, S.; Srebnik, M. J. Am. Chem.
Soc. 1996, 118, 909-910. (m) Bijpost, E. A.; Duchateau, R.; Teuben, J. H.
J. Mol. Catal. A: Chem. 1995, 95, 121-128. (n) Erker, G.; Noe, R.;
Wingbermu¨hle, D.; Petersen, J. L. Angew. Chem., Int. Ed. Engl. 1993, 32,
1213-1215. (o) Binger, P.; Sandmeyer, F.; Kru¨ger, C.; Kuhnigk, J.;
Goddard, R.; Erker, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 197-198.
(5) Part of this work was previously communicated, see: Pender, M.;
Wideman, T.; Carroll, P. J.; Sneddon, L. G. J. Am. Chem. Soc. 1998, 120,
9108-9109.
(1) For previous papers in this series, see: Kadlecek, D.; Carrol, P. J.;
Sneddon L. G. J. Am. Chem. Soc. 2000, 122, 10868-10877 and references
therein.
(2) Plesek, J. Chem. ReV. 1992, 92, 269-278.
(3) Mazighi, K.; Carroll, P. J.; Sneddon, L. G. Inorg. Chem. 1993, 32,
1963-1969.
(6) Shriver, D. F.; Drezdzon, M. A. Manipulation of Air-SensitiVe
Compounds; 2nd ed.; Wiley: New York, 1986.
(7) Erskine, G. J.; Wilson, D. A.; McCowan, J. D. J. Organomet. Chem.
1976, 114, 119-125.
10.1021/ja011432s CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/15/2001

Titanium-Catalyzed Decaborane-Olefin Hydroborations
J. Am. Chem. Soc., Vol. 123, No. 49, 2001 12223
Table 1. Summary of Reaction Conditions and Results
decaborane
(g, mmol)
Cp2Ti(CO)2
(g, mmol)/mol %
time (h)/
temp (°C)
% conversion/
TONc
product (g, mmol)/
isolated yield (%)
reaction
olefin
1a
1b
1ca
1da
2a
2ba
3a
3b
4a
4b
5
1-hexene (25 mL)
1-hexene (13 mL)
1-hexene
1-hexene
1-octene (20 mL)
1-octene
AllylTMS (20 mL)
AllylTMS (2.9 mL)b
1,5-hexadiene (16 mL)
1,5-hexadiene (75 mL)
Allyl2SiMe2 (18 mL)
1,5-hexadiene (1.38 g)b
Allyl2SiMe2 (0.63 g)b
Allyl4Si (0.10 g)b
0.516, 4.22
1.00, 2.18
0.051, 0.42
0.054, 0.44
2.34, 19.2
0.052, 0.42
0.24, 2.0
0.24, 2.0
0.19, 1.6
5.15, 42.1
1.50, 12.3
4.13, 33.8
1.10, 9.0
(0.049, 0.21)/5.0
21/90
24/80
14/70
15/75
64/90
16/90
16/83
48/90
24/90
21/90
36/83
144/90
288/88
192/90
100/20
100/8
0/0
1 (0.82, 4.0)/94
1 (1.52, 7.37)/89.7
no reaction
1 not isolated
2 (3.92, 16.8)/88
2 not isolated
3 (0.37, 1.6)/79
3 (0.42, 1.8)/88
4 (0.28, 1.4)/88
4 (7.94, 38.9)/92.3
5 (2.96, 11.3) 91.9
6 (5.08, 15.6) 92.0
7 (1.48, 3.85) 85.5
8 (0.19, 1.1) 54
(0.244, 1.03)/12.6
(0.0049, 0.021)/5.0
(0.0010, 0.0043)/0.97
(0.10, 0.43)/2.3
(0.0022, 0.0093)/2.2
(0.039, 0.17)/8.5
(0.023, 0.098)/4.9
(0.021, 0.090)/5.6
(0.4695, 2.006)/4.76
(0.1316, 0.5622)/4.57
(0.380, 1.62)/4.79
(0.160, 0.685)/7.61
(0.039, 0.17)/8.1
10/10
100/45
40/18
95/11
100/20
100/18
100/21
100/22
100/21
100/13
90/11
6
7
8
0.25, 2.1
a NMR scale reaction. b Toluene or benzene used as solvent. c TON ) turnover number, as determined by 64.2 MHz 11B NMR.
Platinum(II) bromide and H2PtCl6‚6H2O were purchased from Aldrich
and used as received. All olefins were purchased from Aldrich, Sigma,
or Gelest and were dried over CaH2 and vacuum transferred prior to
use. Decaborane was freshly sublimed before use. Reaction solvents
were obtained from Fischer and dried using standard procedures. Other
solvents were also obtained from Fischer and used as received unless
noted otherwise.
B6), 9.9 (d, 2, B1,3), 8.3 (d, 1, B9), 0.7 (d, 2, B5,7), -3.2 (d, 2, B8,
1
10), -34.2 (d, 1, B2), -39.1 ppm (d, 1, B4). H NMR (200.1 MHz,
C6D6): 1.44 (m, 2, CH2), 1.18 (m, 12, CH2), 0.79 (t, 3, CH3), -1.9
ppm (s, 4, BHB). IR (NaCl plates, cm-1): 2900 (vs), 2830 (vs), 2550
(vs), 1970 (w), 1940 (b,w), 1895 (b,m), 1550 (s), 1530 (s), 1495 (s),
1455 (b,vs), 1405 (s), 1375 (m), 1345 (w), 1305 (b,w), 1090 (s), 995
(vs), 955 (s), 930 (m), 910 (m), 900 (m), 880 (w), 855 (m), 830 (m),
805 (s), 715 (s), 700 (s), 680 (s).
1
Physical Measurements. H NMR spectra at 200.1 MHz and 11B
NMR spectra at 64.2 MHz were obtained on a Bruker AF-200 Fourier
transform spectrometer. The 11B NMR chemical shifts are relative to
external BF3‚Et2O (0.00 ppm), with a negative sign indicating an upfield
6-(Me3Si(CH2)3)-B10H13, 3. mp 36.5-38.0 °C. Anal. Calcd for
C6H27B10Si: C, 30.48; H, 11.93. Found: C, 30.50; H, 12.47. 11B NMR
(64.2 MHz, C6D6): 25.4 (s, 1, B6), 11.0 (d, 2, B1,3), 9.2 (d, 1, B9),
1.0 (d, 2, B5,7), -2.5 (d, 2, B8,10), -33.4 (d, 1, B2), -37.9 ppm (d,
1
shift. Chemical shifts for H NMR spectra are based on 7.16 ppm for
1
C6D6 (relative to Me4Si at 0.00 ppm). Gas chromatography/mass
spectrometry was performed on a Hewlett-Packard 5890A gas chro-
matograph (equipped with a cross-linked methylsilicone column)
interfaced to a Hewlett-Packard 5970 mass-selective detector. Infrared
spectra were recorded on a Perkin-Elmer 1430 infrared spectropho-
tometer. Elemental analyses were performed at the University of
Pennsylvania microanalysis facility. High-resolution mass spectra were
recorded on a VG-ZAB-E high-resolution mass spectrometer using
negative ionization techniques.
1, B4). H NMR (200.1 MHz, C6D6): 1.61 (m, 2, CH2), 1.19 (m, 2,
CH2), 0.60 (m, 2, CH2), 0.05 (s, 9, CH3), -2.4 ppm (s, 4, BHB). IR
(NaCl plates, CCl4, cm-1): 2960 (w), 2930 (m), 2540 (s), 2480 (m,
sh), 1250 (m), 1160 (w), 1100 (w), 990 (m).
6-(CH2dCH(CH2)4)-B10H13, 4. Oil. Exact mass 12C6 H24 B10: m/z
calcd, 206.2808; measd, 206.2840. 11B NMR (64.2 MHz, C6D6): 25.9
(s, 1, B6), 10.1 (d, 2, B1,3), 8.5 (d, 1, B9), 0.8 (d, 2, B5,7), -2.9 (d,
1
11
1
2, B8,10), -34.2 (d, 1, B2), -38.9 ppm (d, 1, B4). H NMR (200.1
MHz, C6D6): 5.66 (m, 1, dCHs), 4.95 (m, 2, CH2d), 1.97 (m, 2,
CH2), 1.40 (m, 4, CH2), 1.11 (m, 2, CH2), -1.89 ppm (s, 4, BHB). IR
(NaCl plates, cm-1): 3070 (m), 2960 (m), 2910 (vs), 2840 (s), 2560
(vs), 1975 (b,w), 1945 (b,w), 1895 (b,m), 1635 (s), 1550 (s), 1530 (s),
1490 (vs), 1430 (b,s), 1410 (s), 1350 (w), 1255 (w), 1090 (s), 995
(vs), 950 (s), 905 (vs), 875 (m), 850 (m), 830 (m), 805 (s), 715 (s),
700 (s), 685 (s), 630 (m), 620 (m).
Table 1 contains a summary of the conditions and results of the
reactions of decaborane with olefins in the presence of catalytic amounts
of Cp2Ti(CO)2. Detailed descriptions of typical reactions and the
spectroscopic data for the products of all reactions are presented below.
Reactions with Monoolefins. 6-(n-C6H13)-B10H13, 1. In a typical
reaction, a 50 mL round-bottom flask equipped with a high-vacuum
Teflon stopcock was charged under an inert atmosphere with 0.049 g
(0.21 mmol) of Cp2Ti(CO)2, 0.516 g (4.22 mmol) of decaborane, and
25 mL of 1-hexene. The flask was cooled to -196 °C and evacuated.
The reaction flask was sealed and brought to room temperature, and
the body of the flask was completely submerged in a 90 °C oil bath.
After 21 h, 11B NMR analysis showed no unreacted decaborane. The
reaction was stopped and exposed to air. The reaction mixture was
then eluted down a silica gel column with 500 mL of hexanes. The
bulk of the volatiles was removed by rotary evaporation. Volatiles were
further removed on the high-vacuum line overnight. GC/MS analysis
of the remaining yellow oil, 0.82 g (4.0 mmol, 94% yield), showed
6-(n-C6H13)-B10H13 as the only product. Anal. Calcd for C6H26B10: C,
6-(CH2dCHCH2SiMe2(CH2)3)-B10H13, 5. Oil. Anal. Calcd for
C8H30B10Si: C, 36.60; H, 11.52. Found: C, 36.88; H, 11.92. 11B NMR
(64.2 MHz, C6D6): 24.7 (s, 1, B6), 10.3 (d, 2, B1,3), 8.5 (d, 1, B9),
0.3 (d, 2, B5,7), -3.2 (d, 2, B8,10), -34.2 (d, 1, B2), -38.7 ppm (d,
1, B4). 1H NMR (200.1 MHz, C6D6): 5.80 (m, 1, dCHs), 4.96 (m, 2,
CH2d), 1.56 (m, 4, CH2), 1.18 (m, 2, CH2), 0.62 (m, 2, CH2), 0.03 (s,
6, CH3), -2.3 ppm (s, 4, BHB). IR (NaCl plates, cm-1): 3050 (w),
2930 (m), 2900 (s), 2860 (m), 2550 (vs), 1970 (b,w), 1930 (b,w), 1890
(b,w), 1620 (m), 1545 (w), 1490 (s), 1405 (m), 1330 (w), 1240 (s),
1185 (w), 1145 (m), 1085 (w), 1020 (w), 995 (s), 950 (w), 920 (m),
880 (m), 820 (vs), 720 (w), 690 (m), 630 (m).
6-(n-C8H17)-B10H13, 2. In a separate experiment designed to deter-
mine the robustness of the Cp2Ti(CO)2 catalyst, a 500 mL round-bottom
flask, equipped with a high-vacuum Teflon stopcock, was charged under
an inert atmosphere with 0.056 g (0.24 mmol) of Cp2Ti(CO)2, 39.0
mL (249 mmol) of 1-octene, and 1.33 g (10.9 mmol) of decaborane.
The flask was cooled to -196 °C and evacuated. The reaction flask
was then brought to room temperature, and the body of the flask was
completely submerged in an 85 °C oil bath. After ∼45 min, the reaction
mixture had changed from reddish brown to dark green. A total of
7.11 g (58.2 mmol) of decaborane was added in increments over the
course of 12 days (see Table 2). After 307 h, all decaborane had been
consumed. When the reaction mixture was exposed to the air, the
solution changed from green to orange, and a precipitate formed. The
mixture was eluted down a silica gel column with toluene until no
1
11
34.92; H, 12.70. Found C, 35.09; H, 11.26. Exact mass 12C6 H26 B10:
m/z calcd, 208.2965; measd, 208.2973. 11B NMR (64.2 MHz, C6D6):
25.9 (s, 1, B6), 10.9 (d, 2, B1,3), 9.2 (d, 1, B9), 1.0 (d, 2, B5,7), -2.5
(d, 2, B8,10), -33.4 (d, 1, B2), -38.0 ppm (d, 1, B4). 1H NMR (200.1
MHz, C6D6): 1.48 (m, 2, CH2), 1.30 (m, 6, CH2), 1.10 (m, 2, CH2),
0.92 (t, 3, CH3), -2.45 ppm (s, 4, BHB). IR (NaCl plates, cm-1): 2920
(vs), 2900 (vs), 2830 (vs), 2540 (vs), 1970 (w), 1930 (b,w), 1890 (b,m),
1540 (m), 1520 (m), 1490 (vs), 1445 (b,s), 1410 (s,sh), 1370 (m), 1340
(w), 1200 (w), 1085 (s), 990 (vs), 950 (s), 925 (m), 910 (m), 875 (m),
850 (m), 830 (m), 800 (m), 760 (w), 710 (s), 700 (m), 680 (m).
6-(n-C8H17)-B10H13, 2. Oil. Anal. Calcd for C8H30B10: C, 40.99; H,
12.90. Found: C, 41.20; H, 13.40. Exact mass 12C8 H30 B10: m/z calcd,
1
11
236.3278; measd, 236.3277. 11B NMR (64.2 MHz, C6D6): 25.5 (s, 1,

12224 J. Am. Chem. Soc., Vol. 123, No. 49, 2001
Pender et al.
Table 2. Summary of 13 Day Titanium-Catalyzed Reaction of
Decaborane with 1-Octene
with 0.039 g (0.17 mmol) of Cp2Ti(CO)2, 0.10 g (0.52 mmol) of
tetraallylsilane, 0.25 g (2.1 mmol) of decaborane, and 10 mL of toluene
freshly vacuum distilled from Na/benzophenone. The reaction flask was
evacuated at -196 °C and then sealed. After initially warming to room
temperature, the body of the flask was submerged in a 90 °C oil bath.
After 8 days, the reaction mixture was cooled to room temperature,
exposed to air, and eluted down a silica gel column with 300 mL of
hexanes followed by 300 mL of toluene. Following the removal of
volatiles, 0.19 g of product remained, corresponding to a 54% isolated
yield. Crystals were grown from a 3:1 mixture of benzene and heptane
at -10 °C. mp 139-140.5 °C. Anal. Calcd for C12H76B40Si: C, 21.16;
H, 11.25. Found C, 22.53; H, 11.98. LRMS (electrospray) for
time (h)
total turnovers
B10H14 mmol added
0
43
96
139
187
307
0
34
71
97
140
244
10.9
11.6
16.2
9.2
10.3
0
product was visible by TLC in the fractions. The bulk of the volatiles
was removed via rotary evaporation. Volatiles were further removed
on a high-vacuum line overnight. GC/MS analysis of the remaining
brown oil, 12.36 g (52.7 mmol, 90.5% yield), showed 6-(n-C8H17)-
B10H13 to be the only product.
Reactions of 6-(n-C8H17)-B10H13 with Lewis Bases. A 2.0 mL
aliquot of a 0.020 M solution of 6-(n-octyl)decaborane in toluene was
stirred with 5.0 mL of dimethyl sulfide overnight at 90 °C. A 11B NMR
spectrum taken at this time showed no reaction. This reaction was
repeated with equal quantities of diethyl sulfide and acetonitrile, but
no reaction was observed by 11B NMR analysis. As was previously
observed for reactions with 6,9-R2-B10H12,3 the reaction of 6-(n-octyl)-
1
11
28Si12C12 H76
B
38
(P-2H): m/z calcd, 686; measd, 686. 11B NMR (64.2
MHz, C6D6): 25.8 (s, 1, B6), 11.2 (d, 3, B1,3 and B9), 1.3 (d, 2, B5,7),
-2.2 (d, 2, B8,10), -33.3 (d, 1, B2), -37.6 ppm (d, 1, B4). 1H NMR
(200.1 MHz, C6D6): 1.92 (m, 8, CH2), 1.32 (m, 8, CH2), 0.99 (m, 8,
CH2), -2.1 (s, 8, BHB), -2.5 ppm (s, 8, BHB). IR (NaCl, CCl4, plates,
cm-1): 2920 (w), 2900 (m), 2880 (w), 2560 (s), 1490 (m), 1420 (b,w),
1240 (m), 1210 (w), 1140 (w), 1000 (w), 970 (sh,w), 670 (w).
Syntheses of 6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12, 9. PtBr2-
Catalyzed Reaction. A 100 mL reaction tube equipped with a high-
vacuum Teflon stopcock was charged under an inert atmosphere with
0.024 g (0.066 mmol, 3.5 mol %) of PtBr2, 0.43 g (1.9 mmol) of 6-(n-
octyl)decaborane, and 3.13 g (26.5 mmol) of allylbenzene. The reaction
flask was cooled to -196 °C, evacuated, and then warmed to room
temperature. The body of the reaction tube was then submerged in a
60 °C oil bath. After 4 h, 11B NMR analysis showed that all of the
6-(n-octyl)decaborane had been consumed. The reaction mixture was
eluted through a silica gel plug and then through activated carbon with
a 1:1 mixture of benzene and hexanes. The bulk of the volatiles was
removed by rotary evaporation. Volatiles were further removed on the
high-vacuum line overnight. GC/MS analysis of the remaining light
brown oil, 0.64 g (1.8 mmol, 97% yield, 29 turnovers), showed 6-(n-
C8H17)-9-(C6H5-(CH2)3)-B10H12 (9) as the only product. Exact mass
decaborane with triethylamine resulted in deprotonation to form the
-
monoanion, i.e., 6-(n-C8H17)-B10H12
.
Multicage Syntheses. 6,6′-(CH2)6-(B10H13)2, 6. A 500 mL round-
bottom flask, equipped with a high-vacuum Teflon stopcock, was
charged under an inert atmosphere with 0.380 g (1.62 mmol) of Cp2-
Ti(CO)2, 4.13 g (33.8 mmol) of decaborane, 1.38 g (16.9 mmol) of
1,5-hexadiene, and 25 mL of toluene freshly vacuum distilled from
Na/benzophenone. The flask was evacuated while being cooled at -196
°C. The flask was then sealed and brought to room temperature, and
then the body of the flask was submerged in a 90 °C oil bath. After
∼6 days, 11B NMR analysis showed that all decaborane had been
consumed. The reaction mixture was exposed to air and eluted down
a silica gel column with toluene. The bulk of the volatiles was removed
by rotary evaporation. Volatiles were further removed on the high-
vacuum line overnight. GC/MS analysis of the remaining peach-colored
solid, 5.08 g (15.6 mmol, 92.0% yield), showed 6,6′-(CH2)6-(B10H13)2
to be the only product. Crystals were grown from a 1:1 heptane and
benzene solution at -10 °C. mp 95.5-96.5 °C. Anal. Calcd for
C6H38B20: C, 22.07; H, 11.73. Found: C, 21.44; H, 11.86. Exact mass
12
11
C
17
1H40 B10: m/z calcd, 354.4061; measd, 354.4075. 11B NMR (64.2
MHz, C6D6): 23.9 (s, 2, B6,9), 8.4 (d, 2, B1,3), -2.4 (d, 4, B5,7,8,10),
1
-36.8 ppm (d, 2, B2,4). H NMR (200.1 MHz, C6D6): 7.11 (m, 5,
Ph), 2.61 (t, 2, CH2), 1.83 (m, 2, CH2), 1.44 (m, 4, CH2), 1.19 (m, 12,
CH2), 0.80 (t, 3, CH3), -1.8 ppm (s, 4, BHB). IR (NaCl plates, cm-1):
3050 (w), 3010 (m), 2910 (vs), 2840 (s), 2550 (vs), 1920 (vb,w), 1600
(w), 1520 (m), 1500 (s), 1490 (s), 1450 (s), 1410 (s), 1350 (w), 1260
(w), 1095 (s), 1080 (m), 1030 (w), 995 (s), 960 (w), 900 (w), 840 (w),
810 (b,w), 745 (s), 730 (m), 700 (s).
12C6 H38 B20: m/z calcd, 330.4835; measd, 330.4849. 11B NMR (64.2
MHz, C6D6): 25.4 (s, 1, B6), 9.9 (d, 2, B1,3), 8.2 (d, 1, B9), 0.4 (d, 2,
B5,7), -3.2 (d, 2, B8,10), -34.3 (d, 1, B2), -39.0 ppm (d, 1, B4). 1H
NMR (200.1 MHz, C6D6): 1.56 (m, 4, CH2), 1.40 (m, 4, CH2), 1.15
(m, 4, CH2), -2.4 ppm (s, 8, BHB). IR (NaCl plates, CCl4, cm-1):
2940 (m), 2910 (m), 2860 (w), 2560 (s), 1355 (b,m), 1260 (m), 1095
(m), 1020 (m), 760 (m).
1
11
H2PtCl6‚6H2O-Catalyzed Reaction. A 100 mL reaction tube
equipped with a high-vacuum Teflon stopcock was charged under an
inert atmosphere with 0.0121 g (0.023 mmol) of H2PtCl6‚6H2O, 4.0
mL of allylbenzene, and 0.15 g (0.64 mmol) of 6-(n-octyl)decaborane.
The tube was cooled to -196 °C and evacuated on a high-vacuum
line. The flask was warmed to room temperature and then immersed
in a 65 °C oil bath and stirred for 22 h. Analysis by 11B NMR showed
the formation of 6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (9) to be less than
50% complete (14 turnovers).
H2PtCl6‚6H2O Catalyst with Decaborane Initiator. A 100 mL
reaction tube equipped with a high-vacuum Teflon stopcock was
charged under an inert atmosphere with 0.0268 g (0.052 mmol) of H2-
PtCl6‚6H2O, 3.23 g of allylbenzene, 0.31 g (1.3 mmol) of 6-(n-octyl)-
decaborane, and 0.0094 g (0.070 mmol) of decaborane. The reaction
tube was cooled to -196 °C and evacuated on a high-vacuum line.
The tube was warmed to room temperature and then immersed and
stirred in a 65 °C oil bath. Analysis by 11B NMR showed the reaction
to be complete after 14 h. TLC analysis indicated that, in addition to
the major product 6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (9), small
amounts of 6,9-(C6H5-(CH2)3)-2-B10H12 were also produced, with the
latter compound resulting from the platinum-catalyzed reaction of
allylbenzene with the B10H14 initiaitor. After separation by flash filtering
through a silica gel column, 0.41 g of a mixture was obtained, which
corresponds (assuming the ratio of products is equal to the ratio of
starting decaborane and 6-(n-octyl)decaborane) to an isolated yield of
83% (25 turnovers).
(CH3)2Si(6-(CH2)3-B10H13)2, 7. A 100 mL round-bottom flask,
equipped with a high-vacuum Teflon stopcock, was charged under an
inert atmosphere with 0.160 g (0.685 mmol) of Cp2Ti(CO)2, 1.10 g
(9.00 mmol) of decaborane, 0.63 g (4.5 mmol) of diallyldimethylsilane,
and 10 mL of toluene freshly vacuum distilled from Na/benzophenone.
The flask was evacuated while being cooled at -196 °C and then sealed.
After initially warming to room temperature, the body of the flask was
submerged in an 88 °C oil bath. After 12 days, 11B NMR analysis
showed that the reaction was complete. The reaction mixture was
exposed to air and eluted down a silica gel column with 200 mL of
toluene. The bulk of the volatiles was removed by rotary evaporation.
Volatiles were further removed on the high-vacuum line overnight to
yield 1.48 g (3.85 mmol, 85% yield) of a peach-colored solid. mp
109.0-110.5 °C. Exact mass 12C8 H44
B
28Si: m/z calcd, 388.5073;
20
1
11
measd, 388.5088. 11B NMR (64.2 MHz, C6D6): 24.6 (s, 1, B6), 10.4
(d, 2, B1,3), 8.7 (d, 1, B9), 0.4 (d, 2, B5,7), -3.1 (d, 2, B8,10), -34.1
1
(d, 1, B2), -38.6 ppm (d, 1, B4). H NMR (200.1 MHz, C6D6): 1.68
(m, 4, CH2), 1.24 (m, 4, CH2), 0.72 (m, 4, CH2), 0.12 (s, 6, CH3),
-2.5 ppm (s, 8, BHB). IR (NaCl plates, cm-1): 2940 (m), 2900 (m),
2880 (sh,w), 2560 (s), 1490 (m), 1420 (b,w), 1240 (m), 1210 (b,w),
1150 (w), 1085 (w), 1000 (m), 940 (w), 690 (w).
Si(6-(CH2)3-B10H13)4, 8. A 50 mL round-bottom flask, equipped with
a high-vacuum Teflon stopcock, was charged under an inert atmosphere
H2PtCl6‚6H2O Catalyst with Triethylsilane Initiator. A 100 mL
reaction tube equipped with a high-vacuum Teflon stopcock was

Titanium-Catalyzed Decaborane-Olefin Hydroborations
J. Am. Chem. Soc., Vol. 123, No. 49, 2001 12225
Table 3. Crystallographic Data Collection and Structure Refinement Information
5
6
8
10
formula
C8B10H30Si
262.51
monoclinic
C2/c (No. 15)
8
C6B20H38
326.56
C12B40H76Si
681.22
monoclinic
P21/n (No. 14)
4
PtC44B20H98N4O2
1126.55
monoclinic
P21/c (No. 14)
4
formula weight
crystal class
triclinic
space group
P1h (No. 2)
2
Z
cell constants
a
13.5697(3) Å
14.9807(5) Å
17.6395(3) Å
10.0173(9) Å
14.2662(10) Å
8.1422(6) Å
94.144(4)°
104.290(3)°
82.144(6)°
1116.1(2) Å3
0.40 cm-1
12.1547(1) Å
30.8009(2) Å
12.7664(1) Å
14.1449(5) Å
16.7051(5) Å
25.5823(12) Å
b
c
R
â
94.442(2)°
102.918(1) Å3
95.5610(10)°
γ
V
µ
3575.1(2) Å3
1.09 cm-1
4658.47(6) Å3
0.65 cm-1
6016.4(4) Å3
23.70 cm-1
0.32 × 0.20 × 0.03
1.244 g/cm3
2336
crystal size, mm
Dcalc
0.30 × 0.28 × 0.20
0.975 g/cm3
1136
0.34 × 0.20 × 0.08
0.972 g/cm3
348
0.45 × 0.18 × 0.15
0.971 g/cm3
1448
F(000)
radiation
Mo KR
Mo KR
Mo KR
Mo KR
λ ) 0.71069 Å
5.44-50.7°
180
λ ) 0.71069 Å
5.16-50.70°
200
λ ) 0.71069 Å
5.14-50.7°
200
λ ) 0.71069 Å
4.88-50.7°
200
2θ range
temperature, K
hkl collected
-16 e h e 16;
-18 e k e 18;
-21 e l e 20
12 056
-12 e h e 12;
-17 e k e 17;
-9 e l e 9
8368
-14 e h e 14;
-36 e k e 36;
-15 e l e 15
32 624
-16 e h e 16;
-17 e k e 20;
-29 e l e 30
39 097
no. reflections measured
no. unique reflections
no. observed reflections
no. reflections used in refinement
no. parameters
3226 (Rint ) 0.0330)
3002 (F > 4σ)
3226
3697 (Rint ) 0.0324)
3178 (F > 4σ)
3697
8432 (Rint ) 0.0395)
7340 (F > 4σ)
8432
10 576 (Rint ) 0.0832)
9170 (F > 4σ)
10 576
292
388
478
650
R indices (F > 4σ)a
R1 ) 0.0496
wR2 ) 0.1131
R1 ) 0.0538
wR2 ) 0.1155
1.150
R1 ) 0.0665
wR2 ) 0.1518
R1 ) 0.0776
wR2 ) 0.1590
1.161
R1 ) 0.0895
wR2 ) 0.1982
R1 ) 0.1039
wR2 ) 0.2067
1.172
R1 ) 0.0987
wR2)0.1782
R1 ) 0.1153
wR2 ) 0.1850
1.283
R indices (all data)a
GOF
final difference peaks, e/Å3
+0.124, -0.288
+0.168, -0.146
+0.299, -0.262
+3.119, -1.585
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑w(Fo - Fc2)2/∑w(Fo )2}1/2
.
2
2
charged under an inert atmosphere with 0.0217 g (0.042 mmol) of H2-
PtCl6‚6H2O, 8.0 mL of allylbenzene, 0.25 g (1.1 mmol) of 6-(n-octyl)-
decaborane, and 0.04 g of a 17% solution of triethylsilane in
allylbenzene (0.059 mmol Et3SiH). The reaction tube was cooled to
-196 °C and evacuated on a high-vacuum line. The reaction flask was
warmed to room temperature and immersed in a 65 °C oil bath. After
the solution was stirred for 7 h, 11B NMR analysis showed complete
reaction to form 6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (9). Following
separation of products by column chromatography (silica gel, hexanes:
toluene 3:1), 0.59 g of product was obtained, which corresponds to an
isolated yield of 90% (26 turnovers).
(w), 1540 (w), 1500 (m), 1430 (w), 1395 (w), 1290 (w), 1240 (w),
1195 (w), 1170 (w), 1110 (w), 1090 (w), 1050 (w), 1020 (m), 860
(vs), 840 (vs), 830 (vs), 710 (w), 700 (w), 680 (m).
Crystallographic Data for Compounds 5, 6, 8, and 10. Single
crystals of 6-(CH2dCHCH2SiMe2(CH2)3)-B10H13 (5, UPenn 3164), 6,6′-
(CH2)6-(B10H13)2 (6, UPenn 3133), Si(6-(CH2)3-B10H13)4 (8, UPenn
3175), and (PSH+)2-commo-Pt-[nido-7-Pt-8-(n-C8H17)-B10H11]2 (10,
2-
UPenn 3138) were grown as described above. Suitably sized crystals
were mounted and transferred to the diffractometer.
Collection and Reduction of the Data. As described in Table 3,
X-ray intensity data for 5, 6, 8, and 10 were collected on a Rigaku
R-AXIS IIc area detector employing graphite-monochromated Mo KR
radiation (λ ) 0.71069 Å). Indexing was performed on a series of
oscillation images. A hemisphere of data was collected using 8°, 10°,
5°, and 4° oscillation angles for 5, 6, 8, and 10, respectively, with a
crystal-to-detector distance of 82 mm. Oscillation images for each
compound were processed using bioteX,8 producing a listing of
unaveraged F2 and σ(F2) values which were then passed on to the
teXsan9 program package for further processing and structure solution
on a Silicon Graphics Indigo R4000 computer. The intensity data were
corrected for Lorentz and polarization effects, but not for absorption.
Solution and Refinement of the Structures. Each structure was
solved by direct methods (SIR92).10 Refinement was by full-matrix
least-squares based on F2 using SHELXL-93.11 All reflections were
used during refinement (F2’s that were experimentally negative were
(PSH+)2-commo-Pt-[nido-7-Pt-8-(n-C8H17)-B10H11]22-, 10. A two-
neck round-bottom flask equipped with a vacuum adapter, stir bar, and
septum was charged with 0.39 g (1.7 mmol) of 6-(n-octyl)decaborane
and evacuated on the high-vacuum line. On the Schlenk line, 15 mL
of dry THF was syringed into the flask, which was then cooled to -78
°C. An excess (∼1.5-fold) of NaH was added under a positive pressure
of nitrogen. This mixture was allowed to stir for 1.5 h while warming
to room temperature. The mixture was then filtered and the filtrate
transferred to a 100 mL Schlenk tube. To this tube was added, with
rapid stirring, 25 mL of a CH3CN solution containing 0.36 g (1.7 mmol)
of proton sponge (PS) and 0.32 g (0.85 mmol) of (COD)PtCl2. This
mixture was stirred for 16 h. Solvent was removed, and the remaining
crude product was then recrystallized from CH2Cl2 to yield 0.37 g of
a brown/yellow solid, which corresponds to a 40% yield based on
starting Pt. Crystals were grown from a pentane and methylene chloride
solution (1:1) at -10 °C. Anal. Calcd for C44H94B20N4Pt: C, 48.46;
H, 8.69; N, 5.14. Found: C, 48.35; H, 8.67; N, 4.62. LRMS
replaced by F2 ) 0). The weighting scheme for 5 was w ) 1/[σ2(Fo )
2
+ 0.0456P2 + 2.9033P]; for 6, w ) 1/[σ2(Fo ) + 0.0571P2 + 0.4865P];
2
12
11
(electrospray) for
C B
1H74 14N2196Pt (P-PSH+): m/z calcd, 880;
(8) BioteX: A suite of Programs for the collection, Reduction and
Interpretation of Imaging Plate Data; Molecular Structure Corp.: The
Woodlands, TX, 1995.
(9) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corp.: The Woodlands, TX, 1985 and 1992.
(10) SIR92: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidoro, G. J. Appl. Crystallogr. 1994,
27, 435.
30 20
measd, 880. 11B NMR (64.2 MHz, C6D6): 7.6 (s), -2.9 (broad), -23.3
(d), -27.9 ppm (d). 1H NMR (200.1 MHz, C6D6): 19.16 (s, 2, NHN),
8.03 (m, 4, naphth), 7.74 (m, 8, naphth), 3.20 (s, 24, CH3), 1.72 (m, 4,
CH2), 1.57 (m, 24, CH2), 0.87 (m, 6, CH3), -1.7 (s, 2, BHB), -2.2
ppm (s, 2, BHB). IR (NaCl plates, CCl4, cm-1): 3020 (s), 2940 (m),
2650 (s), 2620 (vs), 2460 (w), 1620 (w), 1590 (w), 1580 (m), 1560

12226 J. Am. Chem. Soc., Vol. 123, No. 49, 2001
Pender et al.
for 8, w ) 1/[σ2(Fo ) + 0.0692P2 + 3.2471P]; and for 10, w ) 1/[σ2-
2
B10H13 compounds.12 Their 1H NMR spectra all show the
characteristic cage and substituent resonances that are consistent
with anti-Markovnikov addition of the olefin at the 6-boron
position.
(Fo ) + 0.0198P2 + 81.0910P], where P ) (Fo + 2Fc2)/3.
For all compounds, non-hydrogen atoms were refined anisotropically.
For 5 and 6, hydrogen atoms were refined isotropically. For 8, hydrogen
atoms were included as constant contributions to the structure factors
and were not refined. For 10, hydrogen atoms were refined according
to a “riding” model except for the cage hydrogens, H9, H10, H11, H89,
H1011, H9′, H10′, H11′, H89′, and H1011′, which were included as
constant contributions to the structure factors and were not refined.
Crystal and refinement data, refined positional parameters, and bond
distances and angles are presented in Tables S1-16 (Supporting
Information).
2
2
Compounds 1, 2, and 3 were not characterized crystallo-
graphically; however, the structure of 2 was confirmed by an
X-ray structural characterization of its platinum derivative, 10.
Mazighi et al.3 earlier showed that the commo-Pt-[nido-7-Pt-
8,11-(n-C5H11)2-B10H10]22- complex is formed upon reacting 2
-
equiv of 6,9-R2-B10H11 with PtCl2(COD). As shown in eqs 2
and 3, when 6-(n-C8H17)-B10H13 was reacted in a similar manner,
the proton sponge (PS) salt, (PSH+)2-commo-Pt-[nido-7-Pt-8-
(n-C8H17)-B10H11]2- (10) was obtained in a 40% isolated yield.
Results
Reactions with Monoolefins. As summarized in Table 1,
decaborane was found to react (eq 1) with simple terminal
olefins, such as 1-hexene, 1-octene, and allyltrimethylsilane, in
the presence of catalytic amounts of Cp2Ti(CO)2 to yield
monoalkyldecaboranes of the formula 6-RCH2CH2-B10H13.
6-(n-C8H17)-B10H13 + NaH f
Na+[6-(n-C8H17)-B10H12]- + H2 (2)
2Na+[6-(n-C8H17)-B10H12]- + 2PS + PtCl2(COD) f
(PSH+)2-commo-Pt-[nido-7-Pt-8-(n-C8H17)-B10H11]2
2-
Cp2Ti(CO)2
+
B10H14 + RCHdCH2
8 6-RCH2CH2-B10H13 (1)
10
2NaCl + COD (3)
The reactions were monitored by 11B NMR and stopped when
the initial starting decaborane was consumed. For each reaction,
an initial induction period of at least 1 h was observed that was
accompanied by a characteristic color change of the reaction
mixture from dark red to dark green. Generally, the reactions
were complete in 24 h at 90 °C when using ∼5 mol % catalyst
and an excess of olefin. Quantitative conversion of decaborane
to the 6-R-B10H13 products was observed in the 11B NMR
spectra of the reaction solutions. Separation of the catalyst by
flash filtration of the reaction solution through a silica gel plug,
followed by removal of volatiles under vacuum, afforded typical
isolated yields of ∼90%.
An X-ray structural study confirmed the structure shown in
the ORTEP representation in Figure 1. The platinum acts as a
common vertex in two 11-vertex cages, with each cage bound
in an η4 fashion to the formal Pt2+ center. In agreement with
their nido (26 skeletal electrons) electron counts, each PtB10
cage has an open-cage structure based on an icosahedron missing
one vertex. The alkyl groups of the two cages are oriented on
opposite sides of the platinum. The Pt-B8 bond length in 10
(2.34(2) Å) is similar to the Pt-B8 and Pt-B11 bond lengths
in commo-Pt-[nido-7-Pt-8,11-(n-C5H11)2-B10H10]22- (2.400(11)
and 2.370(14) Å), while the Pt-B11 length in 10 (2.275(12)
Å) is significantly shorter and similar to those observed for Pt-
B8 and Pt-B11 (2.273(3) and 2.295(3) Å) in the parent commo-
The titanium-catalyzed reactions are slow (typically less than
one turnover per h), but the catalyst was found to be very long-
lived. For example, as shown in Table 2, 11B NMR analysis of
an experiment where ∼10-12 mmol samples of decaborane
were added every 2 days (total decaborane added: 7.11 g, 58.2
mmol) to a reaction mixture containing only 0.24 mmol of Cp2-
Ti(CO)2 (0.41 mol %) and an excess of 1-octene (39.0 mL, 249
mmol) showed no significant decrease in the rate of formation
of 6-(n-octyl)decaborane over 13 days (244 total catalyst
turnovers). Workup of the reaction as described above gave the
oily, liquid product in a 90.5% isolated yield (12.4 g).
Even when the reactions were carried out for extended times,
the titanium-catalyzed reactions proved to be highly selective
in yielding only monosubstituted decaborane products, 6-R-
B10H13 resulting from anti-Markovnikov addition to the olefin.
For example, GC/MS analysis of the 13 day reaction described
above confirmed 6-(n-octyl)decaborane as the sole product. The
titanium catalyst was found to be inactive for olefins containing
halide, oxygen, nitrile, or N-H groups, due to deactivation of
the catalyst by a process most reasonably involving the direct
reaction of these species at the electrophilic titanium center.
The compositions of all products were established by
elemental analysis and/or exact mass determinations. Both the
Cs symmetry pattern and the downfield singlet at ∼26 ppm
observed in 11B NMR spectra of all products are consistent with
the attachment of an alkyl group to the 6-position of the
decaborane framework, and these spectra are in agreement with
previous studies of the structures and NMR properties of 6-R-
Pt-[nido-7-Pt-B10H12]2 complex.13
2-
Reactions with Polyenes: 1,5-Hexadiene and Diallylsilane.
The titanium-catalyzed reactions of decaborane with noncon-
jugated diolefins, such as 1,5-hexadiene and diallylsilane, gave,
depending upon reaction conditions and stoichiometries, high
yields of either alkenyl-substituted or linked-cage products.
When 1,5-hexadiene or diallylsilane was used in excess, the
alkenyl-substituted products 6-(CH2dCH(CH2)4)-B10H13 (4) and
6-(CH2dCHCH2SiMe2(CH2)3)-B10H13 (5) were produced, re-
spectively, in excellent (∼90%) isolated yields (eqs 4 and 5).
As shown in Table 1, both reactions were carried out with
conditions similar to those described above.
Cp2Ti(CO)2
B10H14 + xs H2CdCH-(CH2)2-CHdCH2
8
6-(H2CdCH-(CH2)4)-B10H13
(4)
(5)
4
Cp2Ti(CO)2
B10H14 + xs Me2Si(CH2CHdCH2)2
8
6-(CH2dCHCH2SiMe2(CH2)3)-B10H13
5
(12) (a) Gaines, D. F.; Bridges, A. N. Organometallics 1993, 12, 2015-
2016. (b) Bridges, A. N.; Powell, D. R.; Dopke, J. A.; Desper, J. M.; Gaines,
D. F. Inorg. Chem. 1998, 37, 503-509.
(13) (a) Klanberg, F.; Wegner, P. A.; Parshall, G. W.; Muetteries, E. L.
Inorg. Chem. 1968, 7, 2072-2077. (b) MacGregor, S. A.; Yellowlees, L.
J.; Welch, A. J. Acta Crystallogr. 1990, C46, 1399-1405.
(11) Sheldrick, G. M. SHELXL-93, Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1993.

Titanium-Catalyzed Decaborane-Olefin Hydroborations
J. Am. Chem. Soc., Vol. 123, No. 49, 2001 12227
2-
Figure 1. ORTEP drawing of the structure of the anion of compound (PSH+)2-commo-Pt-[nido-7-Pt-8-(n-C8H17)B10H11]2 (10). Selected bond
lengths (Å) and angles (°): Pt7-B2, 2.218(12); Pt7-B3, 2.242(12); Pt7-B8, 2.387(13); Pt7-B11, 2.275(12); Pt7-B8′, 2.34(2); Pt7-B11′, 2.287-
(13); B8-B3, 1.79(2); B3-B2, 1.85(2); B2-B11, 1.78(2); B8-B9, 1.81(2); B9-B10, 1.95(2); B10-B11, 1.86(2); C1-B8, 1.60(2); C1-B8-Pt7,
118.4(9); B8-Pt7-B8′, 178.3(5); B2-Pt7-B2′, 179.2(5).
The 11B NMR spectra observed for 4 and 5 are similar to
those of the monoalkyldecaboranes 1, 2, and 3, with a
characteristic singlet at a shift near 25 ppm corresponding to
the substituted B6 boron. Their 1H NMR spectra likewise show
the resonances for the cage and -CH2- (and (CH3)2Si for 5)
protons, but they also exhibit multiplet resonances centered near
4.9 and 5.7 ppm that are characteristic of a vinyl group.
Supporting this interpretation, both compounds exhibit CdC
stretching bands, 1635 (4) and 1620 cm-1 (5), in their infrared
spectra.
As shown in the ORTEP drawing in Figure 2, the structure
of 5 was confirmed by means of a single-crystal X-ray
crystallographic determination. As can be seen in the figure,
Figure 2. ORTEP drawing of the structure of 6-(CH2dCHCH2SiMe2-
(CH2)3)-B10H13 (5). Selected bond lengths (Å) and angles (°): C15-
C16, 1.320(3); C14-C15, 1.484(3); Si-C14, 1.890(2); B6-C11,
hydroboration of only one of the allyl groups of diallylsilane
by the decaborane B6-H unit has occurred to yield a compound
1.577(3); B5-B6, 1.803(3); B5-B10, 1.981(3); B9-B10, 1.784(4);
in which the decaborane cage is substituted at the 6-boron
B7-B8, 1.969(3); B6-B7, 1.798(3); C14-C15-C16, 126.0(2); C13-
Si-C14, 110.74(9); C14-Si-C18, 109.33(10); C14-Si-C17, 108.12.
position by the CH2dCHCH2SiMe2(CH2)3- group. The pres-
ence of the terminal double bond is confirmed by the planar
nature of the H2C(16)dC(15)Hs unit and the C15-C16 bond
length of 1.320(3) Å. All other bond lengths and angles in this
compound are comparable to those reported for 6-Thx-B10H13
(Thx ) CMe2CHMe2).12
By both changing the reaction stoichiometry and carrying out
the reactions for longer times, complete hydroboration of 1,5-
hexadiene and diallylsilane could easily be achieved to produce
the linked cage compounds, 6,6′-(CH2)6-(B10H13)2 (6) and Me2-
Si(6-(CH2)3-B10H13)2 (7), respectively (eqs 6 and 7).
Likewise, the synthesis of 7 was achieved in an 85% isolated
yield by reacting a 2:1 ratio of decaborane to diallyldimethyl-
silane for 12 days at 88 °C using 7.6 mol % Cp2Ti(CO)2 (13
total turnovers).
The 11B NMR spectra observed for 6 and 7 are nearly
identical to those of 4 and 5, but the 1H NMR spectra for 6 and
7 do not contain the vinyl proton resonances found in the later
compounds. Likewise, their IR spectra do not have bands in
the 1600 cm-1 region.
Cp2Ti(CO)2
The structure of 6,6′-(CH2)6-(B10H13)2 was established by a
single-crystal X-ray determination as shown in the ORTEP
diagram in Figure 3. Both of the two independent molecules in
the unit cell are shown in the figure. The structures differ only
in the conformation of the linking alkyl group. Anti-Markovni-
kov addition at the 6-vertex of decaborane is again confirmed.
All bond lengths and angles are in the normal ranges and
comparable to those found in 5 and 6-Thx-B10H13.12
2B10H14 + H2CdCH-(CH2)2-CHdCH2
8
6,6′-(CH2)6-(B10H13)2
(6)
(7)
6
Cp2Ti(CO)2
2B10H14 + Me2Si(CH2CHdCH2)2
8
Me2Si(6-(CH2)3-B10H13)2
7
Reaction with Si(CH2CHdCH2)4: Synthesis of Si(6-
(CH2)3-B10H13)4. The unique, tetracage product, Si(6-(CH2)3-
B10H13)4 (8) was obtained by the reaction of 4 equiv of
decaborane with tetraallylsilane for 8 days at 90 °C in the
The reaction of a 2:1 ratio of decaborane to 1,5-hexadiene in
the presence 4.8 mol % Cp2Ti(CO)2 at 90 °C was complete in
6 days (21 total turnovers) and afforded 6 in 92% isolated yield.

12228 J. Am. Chem. Soc., Vol. 123, No. 49, 2001
Pender et al.
Figure 3. ORTEP drawing of the structure of 6,6′-(CH2)6-(B10H13)2 (6). Selected bond lengths (Å): B6-C11, 1.570(3); B5-B6, 1.802(4); B5-
B10, 1.985(4); B9-B10, 1.781(5); B7-B8, 1.992(4); B6-B7, 1.794(4).
presence of 8.1 mol % Cp2Ti(CO)2 (12 total turnovers) (eq 8).
structure. All other bond lengths and angles in 8 are comparable
to those found in 5, 6, and 6-Thx-B10H13.12
Cp2Ti(CO)2
Synthesis of an Asymmetrically Substituted Dialkylde-
caborane. As discussed earlier, Mazighi and co-workers have
shown that chloroplatinic acid and platinum bromide are
effective catalysts for the hydroboration of olefins with decabo-
rane to form products of the formula 6,9-R2-B10H12.3 The fact
that the titanium and platinum catalysts give high yields of
mono- and dialkyldecaboranes, respectively, suggested that these
catalysts could be used in tandem to provide a route to
asymmetrically substituted dialkyldecaboranes. Thus, following
the synthesis of a 6-R-B10H13 compound with the titanocene-
catalyzed reaction, a different substituent could be introduced
at B(9) by reacting the monoalkyldecaborane with a second
olefin in the presence of a platinum catalyst. With this aim in
mind, the chloroplatinic acid-catalyzed reaction of 6-(n-C8H17)-
B10H13 (2), which was obtained from the Cp2Ti(CO)2-catalyzed
reaction of decaborane with octene, with allylbenzene was
examined. However, the first attempt to synthesize the expected
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 product showed the platinum-
catalyzed reaction to be surprisingly slow. Thus, after reaction
for 22 h at 65 °C with 3.7 mol % catalyst, less than 50%
conversion was observed (eq 9).
4B10H14 + Si(CH2CHdCH2)4
8
Si(6-(CH2)3-B10H13)4
(8)
8
The reaction progress was monitored by 11B and H NMR.
Since the reaction involves the successive hydroboration of the
four allyl groups, intermediate species were observed during
the course of the reaction, but the reaction was not stopped until
complete hydroboration was achieved. The final solid product
was isolated by eluting the reaction mixture down a silica gel
column with hexanes followed by toluene and was obtained in
1
a 54% isolated yield. The 11B and H NMR and IR spectra
observed for 8 are similar to those observed for 6,6′-(CH2)6-
(B10H13)2.
1
The structure shown in the ORTEP representation (Figure
4) was confirmed by means of a single-crystal X-ray determi-
nation. As can be seen in the figure, complete hydroboration
of tetraallylsilane was achieved to produce a tetradecaboranyl
silane. The C-Si-C angles around the silicon center are
approximately tetrahedral, ranging from 105° to 114°, but the
four cages are not, in fact, tetrahedrally oriented. Instead, the
four linking -(CH2)3- chains adopt configurations in the solid
state that allow the four cages to be nearly coplanar. This is
clearly shown by the fact that the four angles B6A-Si-B6B
(96.33(5)°), B6B-Si-B6C (65.43(5)°), B6C-Si-B6D (127.3-
(5)°), and B6D-Si-B6A (77.31°(5)) sum to 366.37°, which is
remarkably close to the 360° value expected for a planar
6-(n-C8H17)-B10H13
+
CH2dCHCH2-C6H5 3.7 mol % H PtCl ‚6H O8
2
6
2
22 h, 65 °C
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (<50% conv)
(9)
9

Titanium-Catalyzed Decaborane-Olefin Hydroborations
J. Am. Chem. Soc., Vol. 123, No. 49, 2001 12229
6-(n-C8H17)-B10H13 +
3.8 mol %
CH2dCHCH2-C6H5 H PtCl ‚6H O/Et SiH init8
2
6
2
3
7 h, 65 °C
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (100% conv)
(11)
9
Best results were obtained when a PtII source, 3.5 mol %
PtBr2, was used as the catalyst. No initiator was needed, and
the reaction went to completion in only 4 h at 60 °C (28 total
turnovers) (eq 12).
3.5 mol % PtBr2
6-(n-C8H17)-B10H13 + CH2dCHCH2-C6H5
8
4 h, 60 °C
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (100% conv)
(12)
9
Workup of the reaction by simply filtering the reaction
mixture through a silica gel column and activated carbon,
followed by evaporation of volatiles, gave the final product in
97% isolated yield.
Discussion
Figure 4. ORTEP drawing of the structure of Si(6-(CH2)3-B10H13)4
(8). Selected bond lengths (Å) and angles (°): Si-C1a, 1.883(3); C3a-
B6a, 1.565(4); B5a-B6a, 1.806(4); B5a-B10a, 1.980(5); B9a-B10a,
1.780(5); B7a-B8a, 1.976(5); B6a-B7a, 1.794(5); C1a-Si-C1b,
111.34(13); C1a-Si-C1c, 105.29(13); C1a-Si-C1d, 110.04(13);
C1b-Si-C1c, 109.02(12); C1b-Si-C1d, 107.00(13); C1c-Si-C1d,
114.22(14).
The titanium-catalyzed decaborane-olefin hydroboration
reactions provide a new route for the controlled, high-yield
functionalization of decaborane that is complementary to the
previously established platinum systems. Whereas PtBr2 and H2-
PtCl6‚6H2O yield predominately dialkyldecaboranes,3 the reac-
tions employing dicarbonyltitanocene afford exclusively mono-
substituted decaboranes. The titanium-catalyzed reactions are
slow, often less than one turnover per hour (see Table 1);
however, their high selectivities and yields coupled with the
fact that they are simple, one-pot reactions give them significant
advantages over the previously reported routes to 6-R-B10H13
compounds.12 The robustness of the catalyst also allows its use
for the complete hydroboration of polyenes, as illustrated by
the synthesis of the unique tetracage compound, Si(6-(CH2)3-
B10H13)4 (8), and, as a result, may now enable efficient routes
to dendritic materials based on the polyboranes.
Recent studies by a number of workers have clearly shown
that the mechanistic steps involved in the early-metal-catalyzed
hydroboration reactions of olefins with monoboranes4 are
distinct from those observed for late-transition-metal-catalyzed
hydroboration reactions.15 Thus, although both the platinum and
titanium complexes catalyze decaborane-olefin hydroborations,
they most probably do so by significantly different mechanistic
steps.
A possible catalytic cycle for the reaction of decaborane with
alkenes, based on Hartwig’s proposed mechanism4f for the Cp2-
TiMe2- and Cp2Ti(CO)2-catalyzed hydroborations of alkenes and
alkynes with catecholborane, is illustrated in Figure 5. Thermally
induced loss of CO from Cp2Ti(CO)2 (A) would produce the
initial coordinately unsaturated monocarbonyl complex Cp2Ti-
(CO) (B). With coordinately unsaturated late transition metals,
boranes can react via oxidative addition of a BH group, but
such a process is less likely with an early metal. In the case of
the catecholborane reactions with Cp2TiMe2, the borane instead
binds to the titanium to form a catalytically active σ-complex
Cp2Ti-(σ-(H-BCat))2.4b,e,f Since, even in the absence of olefin,
decaborane was observed to react with Cp2Ti(CO)2 to form an
initial, highly reactive (and as yet uncharacterized) complex,
the formation of either Cp2Ti-σ-(H-B10H13)CO (C) or, with loss
Such a result does not seem reasonable since, under similar
conditions, a reaction of decaborane with excess olefin and
chloroplatinic acid would have gone to completion to form the
6,9-R2-B10H12 product.
The initial steps in both the chloroplatinic acid-catalyzed
hydrosilylation14 and hydroboration1,3 of olefins are thought to
be similar and to involve the initial reduction of chloroplatinic
acid (PtIV) to a catalytically active PtII species. Consistent with
this step, an induction period is observed in both the chloro-
platinic acid-catalyzed hydrosilylations14 and polyborane hy-
droborations,1,3 during which time the active PtII species is
generated. The sluggish reaction of 6-(n-C8H17)-B10H13 and
allylbenzene with H2PtCl6‚6H2O suggested that the initial
reduction step was slow. That is, in contrast to B10H14, the 6-(n-
C8H17)-B10H13 reactant apparently does not effectively reduce
PtIV to the catalyically active PtII species. Supporting this idea,
it was found that when a small amount of decaborane was added
as an initiator to reactions with 6-(n-C8H17)-B10H13, the induction
period was greatly reduced, and excellent conversions to the
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 product 9 were observed
(eq 10).
6-(n-C8H17)-B10H13
+
4.0 mol %
H2PtCl6‚6H2O//B10H14
CH2dCHCH2-C6H5
init8
14 h, 65 °C
6-(n-C8H17)-9-(C6H5-(CH2)3)-B10H12 (100% conv)
(10)
9
Likewise, when a small amount of Et3SiH, which is known
to reduce PtIV to PtII in chloroplatinic acid-catalyzed hydrosi-
lylations,14 was added to a similar reaction, the reaction was
found to go to completion in only 7 h, with product 9 then
obtained in 90% isolated yields (eq 11).
(15) For recent reviews on metal-catalyzed hydroboration reactions,
see: (a) Beletskaya, I.; Pelter, A. Tetrahedron 1997, 53, 4957-5026. (b)
Burgess, K.; Ohlmeyer, M. J. Chem. ReV. 1991, 91, 1179-1191.
(14) Speir, J. L. AdV. Organomet. Chem. 1979, 17, 407-448.

12230 J. Am. Chem. Soc., Vol. 123, No. 49, 2001
Pender et al.
Figure 6. Possible synergistic bonding interactions between decaborane
and the Cp2Ti fragment.
As depicted in Figure 6, bonding interactions similar to those
proposed for Cp2Ti(σ-H-BCat)2 can be envisioned in a deca-
borane σ-complexes such as C and D. Thus, both a σ-donation
from the B-H bond to the titanium and back-donation from
the titanium to an acceptor orbital centered on the B6(9) boron
could be synergistic bonding components. Titanium-to-boron
back-bonding at these sites is consistent with the fact that the
decaborane 6 and 9 borons are known to be Lewis acidic. For
example, as shown in eq 13, decaborane readily reacts with
bases, such as dimethyl sulfide or acetonitrile, to form adducts
at these positions.17
Figure 5. Possible reaction mechanism for titanium-catalyzed deca-
borane-olefin hydroborations.
of an additional CO, the Cp2Ti-(σ-(H-B10H13))2 (D) complex is
reasonable. Dissociation of CO from C, or B10H14 from D,
would generate the same coordinately unsaturated 16 e-
complex E, which could then bind olefin to form the 18 e-
complex F. Rearrangement of this formal Ti(II) complex to the
Ti(IV) metallacyclopentane structure G could occur in a manner
similar to that proposed for the catecholborane complex.
Reductive elimination would yield the final 6-R-B10H13 product,
with the remaining metal fragment then reacting with another
equivalent of decaborane to regenerate E and continue the cycle.
The question then arises: Why do the platinum-catalyzed
decaborane-olefin reactions yield 6,9-dialkyldecaboranes, while
the titanium reactions yield exclusively, even under forcing
conditions, monosubstituted 6-R-B10H13 products? Given the
separation and opposite orientation of the 6 and 9 BH groups,
sterics would seem to be an unimportant factor in these
differences. Therefore, the answer to the question may lie in
the differences in the modes of decaborane activation by late-
metal and early-metal centers. Platinum(II) can activate boranes
(or silanes) via an oxidative-addition step,14 and for this process,
it is unlikely that there is any significant difference in reactivity
of the 9 B-H positions of B10H14 and 6-R-B10H13. As a result,
dialkyl products, 6,9-R2-B10H12, are produced in the platinum-
catalyzed reactions. Under more forcing conditions, even higher
alkylated products resulting from reactions at the other BH
positions are obtained.3 On the other hand, as discussed above,
instead of undergoing oxidative addition, catecholborane is
activated at the titanium center by forming the Cp2Ti-(σ-(H-
BCat))2 σ-complex. Extended Hu¨ckel calculations4b,e on model
compounds have provided evidence that the HBCat fragment,
indeed, functions as a σ-donor from the B-H bond to the
titanium LUMO d(x2-y2) orbital, but also that there is significant
back-donation of electron density from the titanium HOMO
d(xy) orbital to the vacant LUMO p-orbital centered on the boron
that provides significant stabilization.16 Thus, the stability of
the Cp2Ti(σ-H-BCat)2 complex results from the fact that the
catecholborane can function not only as a σ-donor but also as
an acceptor.
B10H14 + 2SMe2 9
∆8 6,9-B10H12(SMe2)2 + H2 (13)
Since similar interactions are possible at both the 6 and 9
positions, the question then becomes: Why do the titanium-
catalyzed reactions stop after substitution at the 6-position? That
is, why does substitution at the 6-position affect reaction at the
9-position? Given again the separation of the 6 and 9 borons,
an influence on the electronic properties of the B9 boron by a
substituent introduced at the 6 boron might seem surprising.
However, “antipodal” effects, in which a substituent on one side
of a cluster strongly influences the chemical shift and/or
chemical properties of a group on the opposite side of the cage,
are well established18 and are a consequence of the delocalized
nature of cluster bonding. Consistent with the presence of such
an antipodal effect in 6-R-B10H13, it was found (eq 14) in a
series of experiments that 6-(n-octyl)-B10H13 was completely
unreactive toward bases such as dimethyl sulfide or acetonitrile
under conditions in which decaborane readily reacts to form
6,9-B10H12L2 adducts. Thus, attachment of an alkyl group at
the 6 boron results in a decrease in the Lewis acidity at the B9
site.
6-(n-C8H17)-B10H13 + xs SMe2 9
∆8 No Reaction (14)
This lower Lewis acidity of the B9 position of 6-R-B10H13
would thus be unfavorable for the formation of a Cp2Ti(9-(σ-
H-B10H12R)) complex, since the stabilization obtained from
back-donation to the B9 boron would be decreased. Since such
(16) Back-donation of the Ti d(xy) orbital into the B-H σ* orbital might
also be possible, but the calculations reported4e by Hartwig et al. indicate
that, at least for the Cp2Ti(σ-H-BCat)2 complex, the vacant boron p-orbital
is significantly lower in energy.
(17) (a) Knoth, W. H.; Muetteries, E. L. J. Inorg. Nucl. Chem. 1961,
20, 66-72. (b) Cragg, R. H.; Fortuin, M. S.; Greenwood, N. N. J. Chem.
Soc. A 1970, 1817-1821. (c) Pace, R. J.; Williams, J.; Williams, R. L. J.
Chem. Soc. 1961, 2196-2204. (d) Hawthorne, M. F.; Pilling, R. L.; Grimes,
R. N. J. Am. Chem. Soc. 1967, 89, 1067-1074.
(18) See, for example: Herma´nek, S. Chem. ReV. 1992, 92, 325-362
and references therein.

Titanium-Catalyzed Decaborane-Olefin Hydroborations
J. Am. Chem. Soc., Vol. 123, No. 49, 2001 12231
a complex is the intermediate in the proposed reaction scheme
in Figure 5 that is required for the hydroboration of an olefin
by the B9-H unit, reaction does not occur, and, as a result,
monoalkyldecaboranes are the only product of the reaction.
temperatures required for the decaborane reactions prevents
decaborane-alkyne hydroboration.
Cp2TiMe2 had also been found to be a better catalyst than
Cp2Ti(CO)2 for the hydroboration of olefins with catecholborane.4a
However, in our studies of the Cp2TiMe2-catalyzed reactions
of decaborane with alkenes, little reaction was observed at room
temperature. At higher temperatures, the formation of 6-R-
B10H13 products was observed, but no temperature was found
which would give complete conversion before catalyst decom-
position.
Hartwig showed that with catecholborane, Cp2Ti(CO)2 was
actually a better catalyst for the hydroboration of alkynes than
alkenes.4a Unfortunately, we found no activity for the reactions
of decaborane with alkynes. This is most likely due to the fact
that the decaborane reactions require higher temperatures (>70
°C) than the catecholborane reactions (room temperature).
Alkynes readily react at room temperature with Cp2Ti(CO)2 to
form Cp2Ti(CO)(η2-R2C2) complexes,19 and such species are
thought to be important initial intermediates in the catalyzed
catecholborane alkyne reactions.4a,f However, above 30 °C and
in the presence of excess alkyne, these complexes are known
to decompose to Cp2Ti(C4R4) metallacycles.18 Thus, the insta-
bility of required Cp2Ti(CO)(η2-R2C2) intermediates at the
Acknowledgment. We thank the National Science Founda-
tion for support of this work. We also thank Dr. Joe Barendt at
Callery Chemical Co. and Dr. Tom Baker for gifts of deca-
borane.
Supporting Information Available: Tables listing refined
positional and thermal parameters, bond distances, and bond
angles for compounds, 5, 6, 8, and 10 (PDF). This material is
available free of charge via the Internet at http://pubs.acs.org.
(19) (a) Fachinetti, G.; Floriani, C.; Marchetti, F.; Mellini, M. Dalton
Trans. 1978, 1398-1403. (b) Fachinetti, G.; Floriani, C J. Chem. Soc.,
Chem. Commun. 1974, 66-67.
JA011432S