Hydrogen-mediated metal-carbon to metal-boron bond conversion in metal-carboranyl complexes

Article abstract of DOI:10.1021/ja8067098

A hydrogen-mediated Ru-C to Ru-B bond conversion was observed experimentally and supported by the theoretical calculations. Treatment of [η⁵:σ_c-Me₂C(C₅H ₄)(C₂B₁₀H₁₀)]Ru(COD) (1) bearing a Ru-C(cage) σ bond with PR₃ in the presence of H₂ gave Ru-B(cage) bonded complexes [η⁵:σ_B-Me ₂C(C₅H₄)(C₂B₁₀H ₁₀)]RuH₂(PR₃) (R = Cy (2), Ph (3)) (σ_c: Ru-C(cage) σ bond; σ_B: Ru-B(cage) σ bond). Complex 3 was converted to [η⁵: σ_B-Me₂C(C₅H₄)(C ₂B₁₀H₁₀)]Pu(L₂) in the presence of L₂ (L₂ = dPPe (4), PPh₃/P(OEt)₃ (5), PPh₃/pyridine (6)) via liberation of H₂ upon heating. These complexes were fully characterized by various spectroscopic techniques, elemental analyses, and single-crystal X-ray diffraction studies. DFT calculations show that this conversion process is both kinetically and thermodynamically favorable and requires involvement of a hydride ligand.

Full text of DOI:10.1021/ja8067098

Published on Web 10/31/2008
Hydrogen-Mediated Metal-Carbon to Metal-Boron Bond
Conversion in Metal-Carboranyl Complexes
Dongmei Liu,† Li Dang,‡ Yi Sun,†,§ Hoi-Shan Chan,† Zhenyang Lin,*,‡ and
Zuowei Xie*,†
Departments of Chemistry, The Chinese UniVersity of Hong Kong, Shatin, New Territories,
Hong Kong, China, and The Hong Kong UniVersity of Science and Technology, Clear Water
Bay, Kowloon, Hong Kong, China
Received August 25, 2008; E-mail: zxie@cuhk.edu.hk
Abstract: A hydrogen-mediated Ru-C to Ru-B bond conversion was observed experimentally and
supported by the theoretical calculations. Treatment of [η5:σC-Me2C(C5H4)(C2B10H10)]Ru(COD) (1) bearing
a Ru-C(cage) σ bond with PR3 in the presence of H2 gave Ru-B(cage) bonded complexes [η5:σB-
Me2C(C5H4)(C2B10H10)]RuH2(PR3) (R ) Cy (2), Ph (3)) (σC: Ru-C(cage) σ bond; σB: Ru-B(cage) σ bond).
Complex 3 was converted to [η5:σB-Me2C(C5H4)(C2B10H10)]Ru(L2) in the presence of L2 (L2 ) dppe (4),
PPh3/P(OEt)3 (5), PPh3/pyridine (6)) via liberation of H2 upon heating. These complexes were fully
characterized by various spectroscopic techniques, elemental analyses, and single-crystal X-ray diffraction
studies. DFT calculations show that this conversion process is both kinetically and thermodynamically
favorable and requires involvement of a hydride ligand.
Introduction
number of metal-carboranyl and metallacarborane complexes
have been prepared and extensively investigated.5,6
It is well-established that o-carboranes can be readily
converted to the monoanion closo-C2B10H11- and dianion closo-
Reactivity studies show that significantly different from
metal-carbon σ bonds in metal alkyls and metal aryls,7 the
metal-carbon(cage) σ bond in metal-carboranyl complexes is
2-
C2B10H10
via stepwise deprotonation of the cage C-H
protons,1 the dicarbollide ion (nido-C2B9H112-) by selective
removal of one BH vertex,2 the nido-C2B10H122- and arachno-
4-
C2B10H12 through reaction with group 1 metals.3,4 These
(5) (a) Hawthorne, M. F.; Owen, D. A.; Smart, J. C.; Garrett, P. M. J. Am.
Chem. Soc. 1971, 93, 1362. (b) Smart, J. C.; Garrett, P. M.; Hawthorne,
M. F. J. Am. Chem. Soc. 1969, 91, 1031. (c) Zakharkin, L. I.; Orlova,
L. V.; Denisovich, L. I. Zh. Obshch. Khim. 1972, 42, 2217. (d)
Bresadola, S.; Cecchin, G.; Turco, A. Gazz. Chim. Ital. 1970, 100,
682. (e) Bresadola, S.; Rigo, P.; Turco, A. J. Chem. Soc., Chem.
Commun. 1968, 1205. (f) Bresadola, S.; Frigo, A.; Longato, B.; Rigatti,
G. Inorg. Chem. 1973, 12, 2788. (g) Bresadola, S.; Longato, B.;
Morandini, F. J. Organomet. Chem. 1977, 128, C5. (h) Bresadola, S.;
Bresciani-Pahor, N.; Longato, B. J. Organomet. Chem. 1979, 179,
73. (i) Bresadola, S.; Longato, B.; Morandini, F. J. Chem. Soc., Chem.
Commun. 1974, 510. (j) Allegra, G.; Calligaris, M.; Furlanetto, R.;
Nardin, G.; Randaccio, L. Cryst. Struct. Commun. 1974, 3, 69. (k)
Longato, B.; Morandini, F.; Bresadola, S. Inorg. Chem. 1976, 15, 650.
(l) Owen, D. A.; Hawthorne, M. F. J. Am. Chem. Soc. 1970, 92, 3194.
(m) Love, R. A.; Bau, R. J. Am. Chem. Soc. 1972, 94, 8274. (n)
Hawthorne, M. F.; Zheng, Z. P. Acc. Chem. Res. 1997, 30, 267.
(6) For reviews, see: (a) Deng, L.; Xie, Z. Organometallics 2007, 26,
1832. (b) Deng, L.; Xie, Z. Coord. Chem. ReV. 2007, 251, 2452. (c)
Xie, Z. Coord. Chem. ReV. 2006, 250, 259. (d) Hosmane, N. S.;
Maguire, J. A. Organometallics 2005, 24, 1356. (e) Krossing, I.; Raabe,
I. Angew. Chem., Int. Ed. 2004, 43, 2066. (f) Hosmane, N. S.; Maguire,
J. A. Eur. J. Inorg. Chem. 2003, 22, 3989. (g) Wedge, T. J.;
Hawthorne, M. F. Coord. Chem. ReV. 2003, 240, 111. (h) Xie, Z.
Acc. Chem. Res. 2003, 36, 1. (i) Xie, Z. Coord. Chem. ReV. 2002,
231, 23. (j) Valliant, J. F.; Guenther, K. J.; King, A. S.; Morel, P.;
Schaffer, P.; Sogbein, O. O.; Stephenson, K. A. Coord. Chem. ReV.
2002, 232, 173. (k) Grimes, R. N. Coord. Chem. ReV. 2000, 200, 773.
(l) Saxena, A. K.; Maguire, J. A.; Hosmane, N. S. Chem. ReV. 1997,
97, 2421. (m) Saxena, A. K.; Hosmane, N. S. Chem. ReV. 1993, 93,
1081. (n) Hosmane, N. S.; Maguire, J. A. In ComprehensiVe Orga-
nometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds;
Elsevier: Oxford, 2007: Vol. 3, p175. (o) Grimes, R. N. In Compre-
hensiVe Organometallic Chemistry II; Abel, E. W., Stone, F. G. A.,
Wilkinson, G., Eds; Pergamon: New York, 1995; Vol. 1, p 373.
anionic ligands can bond to d- and f-block transition metal ions
in a σ-, η5-, η6-, and η7-fashion, respectively, constituting a very
rich and versatile coordination chemistry. As a result, a large
† The Chinese University of Hong Kong.
‡ The Hong Kong University of Science and Technology.
§ Current address: Department of Chemistry, Queen’s University, King-
ston, Ontario K7L 3N6, Canada.
(1) (a) Boone, J. L.; Brotherton, R. J.; Petterson, L. L. Inorg. Chem. 1965,
4, 910. (b) Heying, T. L.; Ager, J. W.; Clark, S. L.; Alexander, R. P.;
Papetti, S.; Reid, J. A.; Trotz, S. I. Inorg. Chem. 1963, 2, 1097. (c)
Stanko, V. I.; Klimova, A. I. Zh. Obshch. Khim. 1965, 35, 1141.
(2) (a) Wiesboeck, R. A.; Hawthorne, M. F. J. Am. Chem. Soc. 1964, 86,
1642. (b) Hawthorn, M. F.; Wegner, P. A.; Stafford, R. C. Inorg. Chem.
1965, 4, 1675. (c) Dunks, G. B.; Hawthorne, M. F. Acc. Chem. Res.
1973, 6, 124. (d) No¨th, H.; Vahrenkamp, H. Chem. Ber. 1966, 99,
1049. (e) Fussstetter, H.; No¨th, H.; Wrackmeyer, B.; McFarlane, W.
Chem. Ber. 1977, 110, 3172. (f) Wei, X.; Carroll, P. J.; Sneddon, L. G.
Organometallics 2006, 25, 609. (g) Yoo, J.; Hwang, J.-W.; Do, Y.
Inorg. Chem. 2001, 40, 568. (h) Teixidor, F.; Go´mez, S.; Lamrani,
M.; Vin˜as, C.; Sillanpa¨a¨, R.; Kiveka¨s, R. Organometallics 1997, 16,
1278. (i) Shen, H.; Chan, H.-S.; Xie, Z. Organometallics 2008, 27,
1157. (j) Lee, Y.-J.; Lee, J.-D.; Ko, J.; Kim, S.-H.; Kang, S. O. Chem.
Commun. 2003, 1364. (k) Teixidor, F.; Vin˜as, C.; Benakki, R.;
Keveka¨s, R.; Sillanpa¨a¨, R. Inorg. Chem. 1997, 36, 1719.
(3) (a) Dunks, G. B.; Wiersema, R. J.; Hawthorne, M. F. J. Am. Chem.
Soc. 1973, 95, 3174. (b) Tolpin, E. I.; Lipscomb, W. N. Inorg. Chem.
1973, 12, 2257. (c) Churchill, M. R.; DeBoer, B. G. Inorg. Chem.
1973, 12, 2674. (d) Chui, K.; Li, H.-W.; Xie, Z. Organometallics 2000,
19, 5447.
(4) (a) Evans, W. J.; Hawthorne, M. F. J. Chem. Soc., Chem. Commun.
1974, 38. (b) Ellis, D.; Lopez, M. E.; McIntosh, R.; Rosair, G. M.;
Welch, A. J. Chem. Commun. 2005, 1917.
9
10.1021/ja8067098 CCC: $40.75
2008 American Chemical Society
J. AM. CHEM. SOC. 2008, 130, 16103–16110 16103

A R T I C L E S
Liu et al.
inert toward various unsaturated molecules.6c,g,8 For instance,
the following relative reactivity is observed in [η5:σC-
Me2C(C5H4)(C2B10H10)]TiR(NMe2): Ti-C(alkyl) > Ti-N .
Ti-C(cage), although the distances of Ti-C(alkyl) and
Ti-C(cage) are almost identical.9 The Zr-C(cage) bond in [η5:
σC-Me2A(C9H6)(C2B10H10)]Zr(NMe2)2 (A ) C, Si) does not
show any activity toward unsaturated molecules.8e-i Alkynes
do not insert into the Ru-C(cage) σ bond in [η5:σC-
Me2C(C5H4)(C2B10H10)]Ru(CH3CN)2.10 Alkynes and alkenes do
not react with the Ni-C(cage) σ bond either.11 The inertness
of such metal-carbon(cage) σ bonds can be probably ascribed
to the presence of a sterically demanding icosahedral cage which
protects the metal-carbon bond from attack of electrophiles.8e,9,10
These results may lead one to believe that the prevalent M-C
σ-bonded metal-carboranyl complexes reported in the literature
are likely thermodynamic products.
We have recently discovered an unprecedented transformation
of the Ru-C(cage) σ bond to the Ru-B(cage) σ bond in the
presence of dihydrogen gas during the course of hydrogenolysis
of [η5:σC-Me2C(C5H4)(C2B10H10)]Ru(COD). DFT calculations
show that this process is both kinetically and thermodynamically
favorable and dihydrogen plays a key role in this transformation.
These findings are reported in this article.
Figure 1. Molecular structure of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2PCy3
(2) (thermal ellipsoids drawn at the 30% probability level).
Scheme 1
Results and Discussion
[η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PR3). It has been re-
ported that the Ru-C(cage) σ-bonded complex [η5:σC-
Me2C(C5H4)(C2B10H10)]Ru(COD) (1) (σC: Ru-C(cage) σ bond)
does not react with PCy3 (Cy ) cyclohexyl) or PPh3 even at
refluxing THF probably due to steric reasons.12 However, in
the presence of H2, 1 reacted readily with PR3 in THF at 60 °C
to give the Ru-B(cage) σ-bonded dihydride complexes [η5:
σB-Me2C(C5H4)(C2B10H10)]RuH2(PR3) (σB: Ru-B(cage) σ bond;
R ) Cy (2), Ph (3)) in 87-88% isolated yields (Scheme 1).
They are very sensitive to air and moisture, but remain stable
under inert atmosphere for months. Both 2 and 3 are soluble in
THF and aromatic solvents but are insoluble in hexane.
In addition to the resonances of Me2C and PCy3 (in 2) or
PPh3 (in 3) protons, four multiplets in the range of 5.26-4.18
ppm corresponding to the protons of cyclopentadienyl ring, one
characteristic broad singlet at ca. 3.30 ppm assignable to the
cage CH proton and one doublet of doublet at -10.58 ppm with
2
2JPH ) 30.0 Hz and JHH ) 3.0 Hz in 2 and -9.6 ppm with
2JPH ) 30.0 Hz and JHH ) 3.0 Hz in 3 attributable to the
2
Ru-H2 hydrido protons, were observed in the 1H NMR spectra.
The 13C NMR data were consistent with the H NMR results.
1
The 11B{1H} NMR spectra showed a 1:1:1:2:2:2:1 pattern for
2 and a 1:1:1:1:2:3:1 pattern for 3. The proton-coupled 11B NMR
exhibited clearly a singlet at 10.75 ppm for 2 and at 9.37 ppm
for 3, indicating that no proton is bonded to this boron atom.
The above spectroscopic data suggested that the Ru atom may
be bonded to the cage B rather than the cage C atom. The 31P
NMR spectra displayed one signal at 82.2 ppm for 2 and 51.3
ppm for 3. The characteristic Ru-H absorption at 1958 cm-1
in 2 and 1990 cm-1 in 3 was also observed in the solid-state
IR spectra.13 Their compositions were confirmed by elemental
analyses.
(7) For reviews, see: (a) Schrock, R. R.; Parshall, G. W. Chem. ReV. 1976,
76, 243. (b) Cotton, F. A. Chem. ReV. 1957, 55, 551. (c) Newkome,
G. R.; Puckett, W. E.; Gupta, V. K.; Kiefer, G. E. Chem. ReV. 1986,
86, 451.
(8) (a) Usatov, A. V.; Martynova, E. V.; Dolgushin, F. M.; Peregudov,
A. S.; Antipin, M. Y.; Novikov, Y. N. Eur. J. Inorg. Chem. 2002,
2565. (b) Usatov, A. V.; Martynova, E. V.; Dolgushin, F. M.;
Peregudov, A. S.; Antipin, M. Y.; Novikov, Y. N. Eur. J. Inorg. Chem.
2003, 29. (c) Wang, X.; Jin, G.-X. Chem.sEur. J. 2005, 11, 5758.
(d) Wang, X.; Jin, G.-X. Organometallics 2004, 23, 6319. (e) Wang,
H.; Li, H.-W.; Xie, Z. Organometallics 2003, 22, 4522. (f) Wang, Y.;
Wang, H.; Wang, H.; Chan, H.-S.; Xie, Z. J. Organomet. Chem. 2003,
683, 39. (g) Wang, H.; Wang, H.; Li, H.-W.; Xie, Z. Organometallics
2004, 23, 875. (h) Wang, H.; Chan, H.-S.; Xie, Z. Organometallics
2005, 24, 3772. (i) Deng, L.; Chan, H.-S.; Xie, Z. J. Am. Chem. Soc.
2005, 127, 13774.
Single-crystal X-ray diffraction studies revealed that the Ru
atom is η5-bound to the cyclopentadienyl ring, σ-bound to one
cage boron atom and two hydrogen atoms, and coordinated to
one P atom in a four-legged piano stool geometry. Figures 1
and 2 show the molecular structures of 2 and 3, respectively.
Table 1 summarizes the selected bond distances and angles. The
Ru-B(cage) distances of 2.075(3)/2.087(3) Å in 2 and 3 are
very comparable to that of 2.110(1) Å in transoid-(p-cyme-
(9) Wang, H.; Wang, Y.; Chan, H.-S.; Xie, Z. Inorg. Chem. 2006, 45,
5675.
(10) (a) Sun, Y.; Chan, H.-S.; Zhao, H.; Lin, Z.; Xie, Z. Angew. Chem.,
Int. Ed. 2006, 45, 5533. (b) Sun, Y.; Chan, H.-S.; Dixneuf, P. H.;
Xie, Z. Organometallics 2006, 25, 2719.
(11) (a) Deng, L.; Chan, H.-S.; Xie, Z. J. Am. Chem. Soc. 2006, 128, 7728.
(b) Qiu, Z.; Xie, Z. Angew. Chem., Int. Ed. 2008, 47, 6572.
(12) Sun, Y.; Chan, H.-S.; Dixneuf, P. H.; Xie, Z. Organometallics 2004,
23, 5864.
(13) These data are similar to those reported in the following literature: Abdur-Rashid,
K.; Abbel, R.; Hadzovic, A.; Lough, A. J.; Morris, R. H. Inorg. Chem. 2005,
44, 2483.
9
16104 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Metal-Carbon to Metal-Boron Bond Conversion
A R T I C L E S
In addition to the signals assignable to L2 and Me2C-, four
multiplets in the range of 5.46-3.35 ppm attributable to the
Cp ring protons and a characteristic broad singlet at 2.35 ppm
in 4, 3.12 ppm in 5, and 2.52 ppm in 6 corresponding to the
1
cage CH proton were observed in the H NMR spectra. Their
13C NMR data were consistent with the above results. The
11B{1H} NMR spectra showed a pattern of 1:1:1:2:3:1:1 for 4
and 1:1:1:1:3:2:1 for both 5 and 6. The unique 11B NMR signal
of the B atom bonded to the Ru atom was assigned by
comparison of the 1H decoupled and coupled 11B NMR spectra.
The chemical shift of this boron was found to be shifted to the
lower field, 15.0 ppm in 4, 15.6 ppm in 5, and 18.2 ppm in 6.
Single-crystal X-ray analyses revealed that the Ru atom is
η5-bound to the cyclopentadienyl ring, σ-bound to one cage
boron atom, and coordinated to two P atoms in 4 and 5 or one
P atom and one N atom in 6 in a distorted tetrahedral geometry.
The structures of 4-6 are shown in Figures 3-5, respectively.
The average Ru-C(ring) and Ru-B(cage) distances and the
Cent-Ru-B(cage) and Cring-Cbridge-Bcage angles in 4-6 are
similar to each other, as indicated in Table 1. These measured
values are also close to those observed in 2 and 3. The P-Ru-P
angle of 95.2(1)° in 5 is much larger than that of 82.3(1)° in 4
but is similar to that of 93.6(1)° in [η5:σC-Me2C(C5H4)-
(C2B10H10)]Ru[P(OEt)3]222 and 95.8(1)° in [η5:σC-Me2C(C5H4)-
(C2B10H10)]Ru[PPh2(OEt)]2.22 The P-Ru-N angle of 96.3(1)°
in 6 is similar to the P-Ru-P angle of 95.2(1)° in 5 but is
larger than that of 89.3(2)° in [η5:σ-Me2C(C5H4)(C2B10H10)]-
Ru(NH2Prn)(PPh3).22
Figure 2. Molecular structure of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2PPh3
(3) (thermal ellipsoids drawn at the 30% probability level).
ne)Ru{σ:σS:σB-SS(HCCH)C2B10H10},14 2.100(3) Å in Ru(Bcat)2-
(CO)2(PPh3)2,15 and 2.093(3) Å in Ru(Bcat)2(CO)(CN-p-
tolyl)(PPh3)2.15 The average Ru-C(ring) distances of 2.249(2)/
2.239(3) Å in 2/3 are close to that of 2.230(4) Å in 1 and
2.263(2) Å in [η5-Me2C(C5H3)(C2B10H10)]RuH(PPh3)2.16 The
Ru-Cent distances of 1.898/1.887 Å in 2/3 are very similar to
that of 1.910 Å in [η5-Me2C(C5H3)(C2B10H10)]RuH(PPh3)2,16
1.907 Å in [η5-C5D4(MeC2B10H10)]RuD(PPh3)2,17 1.881 Å in
(Cp)(MeC2B10H10)Ru(PMe2Ph)2,18 and 1.889 Å in CpRuH-
(PPh3)2.19 The average Ru-H distances of 1.44(3)/1.52(3) Å
in 2/3 compare to that of 1.55(2) Å (Ru-D distance) in [η5-
C5D4(MeC2B10H10)]RuD(PPh3)2,17 1.54(1) Å in [η5-Me2C-
(C5H3)(C2B10H10)]RuH(PPh3)2,16 1.55(3) Å in (C5H4CH2CH2-
NMe2)RuH(PPh3)2,20 and 1.51(4) Å in CpRuH(PPh3)2.19 The
Cent-Ru-B(cage) angles of 114.6/114.1° in 2/3 are slightly
larger than the Cent-Ru-C(cage) angle of 111.8° in 1 and the
Cent-Ru-Cl angle of 112.2° in Cp*RuCl(COD).21 The
Cring-Cbridge-Bcage angles of 109.0(2)/109.4(2)° in 2/3 are
comparable to the Cring-Cbridge-Ccage angles of 108-120°
observed in [η5:σC-Me2C(C5H4)(C2B10H10)]Ru(L2) (L2 ) bi-
dentate phosphines, bipyridine, phosphites, amines, nitriles,
bidentate amines, and amines/phosphines).12,22
We have previously synthesized the Ru-C(cage) σ-bonded
complex [η5:σC-Me2C(C5H4)(C2B10H10)]Ru(dppe) (8)12 by con-
ventional ligand substitution reaction of [η5:σC-Me2C(C5H4)-
(C2B10H10)]Ru(COD) (1) with dppe, which allows a direct
comparison between the two closely related isomers 4 and 8 as
they are different only in the cage atom bonded to the Ru atom.
1
They showed significant differences in their H, 13C, 11B, and
31P NMR spectra due to changes in molecular symmetry. For
1
example, in the H NMR spectra, two multiplets of the Cp
protons and one singlet of the Me2C- unit were found in 8,
whereas four multiplets and two singlets were observed in 4.
The 11B NMR spectra showed a 2:4:4 pattern in 8 and a 1:1:
1:2:3:1:1 pattern in 4. Only one signal at 81.0 ppm was observed
in the 31P NMR spectrum of 8, while two peaks at 89.3 and
87.6 ppm were found in 4. Single-crystal X-ray analyses
indicated that complexes 4 and 8 are isomorphous and isos-
tructural if the differences in cages C and B atoms are ignored.
The Cent-Ru-B(cage)/P-Ru-P/Cring-Cbridge-Bcage angles of
113.6/82.3(1)/109.1(4)° in 4 are very close to the values of
114.3° (Cent-Ru-C(cage)), 82.1(1)° (P-Ru-P), and 108.5(5)°
(Cring-Cbridge-Ccage) observed in 8. The average Ru-Cent
distance of 2.259(6) Å in 4 is slightly longer than that of
2.218(7) Å in 8. However, the Ru-B(cage) distance of 2.088(6)
Å in 4 is much shorter than the Ru-C(cage) distance of 2.141(5)
Å in 8. It is noted that 8 cannot be converted to 4 in the presence
of H2 as 8 does not react with H2, suggestive of the importance
of formation of ruthenium hydride in the aforementioned
Ru-C(cage) to Ru-B(cage) transformation.
[η5:σB-Me2C(C5H4)(C2B10H10)]Ru(L2). In the presence of a
coordinating ligand, [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PPh3)
(3) was readily converted to [η5:σB-Me2C(C5H4)(C2B10H10)]-
Ru(L2) in high yields (L2 ) dppe (1,2-bis(diphenylphosphino)-
ethane) (4), PPh3/P(OEt)3 (5), PPh3/pyridine (6)) upon heating in
toluene through liberation of dihydrogen, as shown in Scheme 2.
(14) Herberhold, M.; Yan, H.; Milius, W.; Wrackmeyer, B. Chem.sEur.
J. 2002, 8, 388.
(15) Rickard, C. E. F.; Roper, W. R.; Williamson, A.; Wright, L. J.
Organometallics 2000, 19, 4344.
(16) Sun, Y.; Chan, H.-S.; Dixneuf, P. H.; Xie, Z. Chem. Commun. 2004,
2588.
(17) Basato, M.; Biffis, A.; Tubaro, C.; Graiff, C.; Tiripicchio, A. Dalton
Trans. 2004, 4092.
(18) Basato, M.; Biffis, A.; Buscemi, G.; Callegaro, E.; Polo, M.; Tubaro,
C.; Venzo, A.; Vianini, C.; Graiff, C.; Tiripicchio, A.; Benetollo, F.
Organometallics 2007, 26, 4265.
[{[η5:σB-Me2C(C5H4)(C2B10H10)]RuH(PPh3)}{K(DME)}]2. Treat-
ment of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PPh3) (3) with 2
equiv of KH in refluxing THF gave, after recrystallization from
DME, an ionic complex [{[η5:σB-Me2C(C5H4)(C2B10H9)]RuH-
(PPh3)}{K(DME)}]2 (7) in 85% isolated yield (Scheme 3). The
possible path way for the formation of 7 may include the
reductive elimination of 3 upon heating with liberation of H2,
(19) Smith, K.-T.; Rømming, C.; Tilset, M. J. Am. Chem. Soc. 1993, 115,
8681.
(20) Ayllon, J. A.; Sayers, S. F.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret,
B.; Clot, E. Organometallics 1999, 18, 3981.
(21) Serron, S. A.; Luo, L.; Li, C.; Cucullu, M. E.; Stevens, E. D.; Nolan,
S. P. Organometallics 1995, 14, 5290.
(22) Sun, Y.; Chan, H.-S.; Dixneuf, P. H.; Xie, Z. J. Organomet. Chem.
2006, 691, 3071.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 16105

A R T I C L E S
Liu et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2-7
2
3
4
5
6
7
av. Ru-Cring
Ru-Bcage
2.249(2)
2.075(3)
1.44(3)
2.239(3)
2.087(3)
1.53(3)
2.259(6)
2.088(6)
2.272(4)
2.128(4)
2.228(2)
2.094(2)
2.250(4)
2.018(5)
1.56(4)
1.899
1.597(5)
1.969(6)
1.743(6)
1.726(6)
1.725(6)
95.6(1)
116.1
av. Ru-H
Ru-Centa
1.898
1.887
1.910
1.622(7)
1.900(8)
1.687(8)
1.702(8)
1.733(9)
92.8(2)
113.6
1.921
1.646(6)
1.898(5)
1.642(6)
1.736(6)
1.745(6)
95.5(1)
112.9
1.871
1.623(3)
1.876(3)
1.681(3)
1.720(3)
1.731(3)
94.4(1)
C(1)-C(2)
1.634(3)
1.863(3)
1.667(3)
1.724(4)
1.731(4)
1.633(4)
1.858(4)
1.687(4)
1.718(4)
1.721(4)
C(1)-B(3)
C(1)-B(4)
C(1)-B(5)
C(1)-B(6)
P-Ru-Bcage
Cent-Ru-Bcage
P(1)-Ru-P(2)
Cring-Cbridge-Bcage
111.5(1)
114.6
112.5(1)
114.1
114.7
82.3(1)
109.1(4)
95.2(1)
108.8(3)
96.3(1)b
108.8(2)
109.0(2)
109.4(2)
108.9(3)
a Cent: the centroid of the cyclopentadienyl ring. b Angle of P-Ru-N.
Table 2. Crystal Data and Summary of Data Collection and Refinement for 2-7
2·0.5C7H8
3·C6H6
4
5
6
7
formula
C
31.5H59B10PRu
C34H43B10PRu
C36H44B10P2Ru
C34H50B10O3P2Ru
C33H40B10NPRu
C64H92B20K2O4P2Ru2
cryst size (mm) 0.50 × 0.40 × 0.20 0.50 × 0.40 × 0.30 0.50 × 0.40 × 0.30 0.30 × 0.20 × 0.10 0.40 × 0.30 × 0.20 0.40 × 0.30 × 0.20
fw
677.9
triclinic
P(-1)
691.8
monoclinic
P21/n
9.291(1)
26.196(2)
4.601(1)
90
93.20(1)
90
747.8
monoclinic
P21
9.153(2)
17.736(4)
11.175(2)
90
90.96(3)
90
777.8
monoclinic
P21/n
10.750(2)
20.386(4)
18.477(4)
90
102.82(3)
90
690.8
triclinic
P(-1)
1483.9
triclinic
P(-1)
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
9.913(1)
12.582(1)
15.460(1)
97.57(1)
98.19(1)
110.54(1)
1752.5(2)
2
10.434(1)
10.750(1)
15.093(2)
97.23(1)
90.23(1)
92.51(1)
1677.8(3)
2
11.304(2)
12.737(4)
14.163(2)
77.41(1)
68.63(1)
78.16(1)
1835.6(4)
1
3548.3(5)
4
1.295
1813.8(6)
2
1.369
3948.5(1)
4
1.309
Z
Dcalcd, Mg/m3
1.285
1.367
1.342
radiation (λ), Å Mo KR (0.71073)
Mo KR (0.71073)
3.1 to 56.0
0.511
Mo KR (0.71073)
4.4 to 50.0
0.548
Mo KR (0.71073)
3.1 to 51.0
0.511
Mo KR (0.71073)
4.0 to 56.0
0.541
Mo KR (0.71073)
3.1 to 50.0
0.613
2θ range, deg
2.7 to 50.0
0.515
714
µ, mm-1
F(000)
1424
768
1608
708
764
no. of obsd
no. of params
6113
414
8548
423
3514
442
6485
451
7959
415
6434
428
goodness of fit 1.014
1.043
1.024
1.097
1.050
1.030
R1
wR2
0.029
0.081
0.039
0.096
0.031
0.078
0.047
0.126
0.030
0.074
0.042
0.094
Scheme 2
the Ru-H proton in addition to the resonances of Me2C-, DME,
and PPh3 groups. The 13C NMR spectrum is consistent with
1
the H NMR results. A pattern of 1:1:1:1:4:2 was observed in
the 11B{1H} NMR spectrum. Its 31P NMR spectrum displayed
one signal at 77.6 ppm.
followed by reaction with KH.23 This result suggested that KH
is not strong enough to deprotonate the cage CH proton.
The 1H NMR spectrum of 7 showed four multiplets at 5.46,
5.00, 4.80, and 4.21 ppm assignable to the Cp protons, one broad
singlet at 3.25 ppm corresponding to the cage CH proton, and
one doublet at -11.75 ppm with 2JPH ) 30.0 Hz attributable to
Figure 3. Molecular structure of [η5:σB-Me2C(C5H4)(C2B10H10)]Ru(dppe)
(4) (thermal ellipsoids drawn at the 30% probability level).
9
16106 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Metal-Carbon to Metal-Boron Bond Conversion
A R T I C L E S
in 3. The Ru-B(cage) distance of 2.018(5) Å is comparable to
that of 2.087(3) Å in 3.
Reaction Pathway/Density Functional Theory (DFT) Cal-
culations. The above conversion from the metal-carbon to
metal-boron bond in metal-carboranyl complexes, shown in
Scheme 1, is totally unexpected, and similar reactions have never
been observed before. To better understand the conversion
process, we carried out DFT calculations. It is reasonably
assumed that the initial event for the conversion is a simple
ligand substitution of COD by H2/PR3 (R ) Cy or Ph) leading
to the formation of a ruthenium dihydride intermediate (A), from
which a metal-carbon to metal-boron conversion then occurs
to give 2 or 3 (Scheme 4). Our DFT calculations based on PMe3
models indeed indicate that the simple ligand substitution is
thermodynamically favorable (Scheme 5).
Figure 7 shows the energy profile calculated for the conver-
sion from the metal-carbon bonded intermediate A to the
metal-boron bonded species B′ and then to its more stable trans
isomer B, a model complex for 2 or 3. It can be seen that the
conversion is both kinetically and thermodynamically favorable.
The conversion is a one-step process assisted by one of the two
hydride ligands, in which B-H bond breaking and C-H bond
forming occur simultaneously.
Figure 4. Molecular structure of the anion in [η5:σB-Me2C(C5H4)-
(C2B10H10)]Ru(PPh3)(P(OEt)3) (5) (thermal ellipsoids drawn at the 30%
probability level).
The result that the metal-boron bonded isomer B is
thermodynamically more stable than the metal-carbon bonded
isomer A is quite unexpected in view of the fact that M-C
σ-bonded metal-carboranyl complexes are far more prevalent
than the M-B σ-bonded metal-carboranyl complexes. The
findings here have the following important implication. The
prevalent M-C σ-bonded metal-carboranyl complexes reported
in the literature are likely kinetic products. They normally do
not undergo isomerization to the thermodynamically more stable
M-B σ-bonded metal-carboranyl complexes, due to a kinetic
reason. In the absence of a hydride ligand, very high barriers
for the isomerization are clearly expected.
Experimentally, it was also found that liberation of dihydro-
gen in 2 and 3 readily occurred in the presence of coordination
ligands (Scheme 2). Our DFT calculation results show that the
ligand substitution is indeed thermodynamically favorable
(Scheme 6).
Conclusion
An unexpected hydrogen-mediated Ru-C to Ru-B bond
conversion is observed in metal-carboranyl complexes for the
first time. In the absence of dihydrogen, [η5:σC-Me2C(C5H4)-
(C2B10H10)]Ru(COD) is very thermally stable. Dihydrogen is
the promoter of this transformation. Such a process leads to a
change in molecular symmetry, resulting in significantly dif-
ferent patterns in NMR spectra between two metal-carboranyl
isomers containing either M-C or M-B bonds, although they
have very similar solid-state structures. DFT calculations show
such a conversion is both kinetically and thermodynamically
favorable and a hydride ligand is crucial to the conversion.
Figure 5. Molecular structure of [η5:σB-Me2C(C5H4)(C2B10H10)]-
Ru(PPh3)(Py) (6) (thermal ellipsoids drawn at the 30% probability level).
Scheme 3
Experimental Section
Single-crystal X-ray diffraction study revealed that 7 is a
centrosymmetric dimer with an inversion center at the midpoint
of the K(1)-K(1A) connectivity. Each Ru atom is η5-bound to
the cyclopentadienyl ring, σ-bound to the cage boron atom and
one doubly bridging hydrogen atom, and coordinated to one
PPh3 in a three-legged piano stool geometry (Figure 6). The
average Ru-C(ring)/Ru-H distances of 2.250(4)/1.56(4) Å and
Cring-Cbridge-Bcage angle of 108.9(3)° are similar to the corre-
sponding values of 2.239(3)/1.53(3) Å and 109.4(2)° observed
General Procedures. All experiments were performed under an
atmosphere of dry nitrogen with the rigid exclusion of air and
moisture using standard Schlenk or cannula techniques, or in a
glovebox. All organic solvents were freshly distilled from sodium
benzophenone ketyl immediately prior to use. [η5:σC-Me2C(C5H4)-
(C2B10H10)]Ru(COD) was prepared according to literature method.12
(23) For the reaction of Ru3(CO)12 with KH, see: Bricker, J. C.; Payne,
M. W.; Shore, S. G. Organometallics 1987, 6, 2545.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 16107

A R T I C L E S
Liu et al.
Figure 6. Molecular structure of [{[η5:σB-Me2C(C5H4)(C2B10H10)]RuH(PPh3)}{K(DME)}]2 (7) (thermal ellipsoids drawn at the 30% probability level).
Scheme 4
Scheme 5
Figure 7. Energy profile calculated for the conversion of the model complex
A to B. A schematic illustration of the bond breaking and forming process
is given in the pane window on the upper-right side. The calculated relative
free energies and electronic energies (in parentheses) are given in kcal/
mol.
for phosphorus chemical shifts. Elemental analyses were performed
by MEDAC Ltd., Middlesex, U.K.
Preparation of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PCy3) (2).
A Schlenk flask with a Teflon valve was charged with [η5:σC-
Me2C(C5H4)(C2B10H10)]Ru(COD) (1; 0.23 g, 0.50 mmol), PCy3
(0.14 g, 0.50 mmol), THF (10 mL), and dihydrogen. The flask was
closed and heated at 60 °C for 12 h until the color of the solution
was changed from brown to pale yellow. After removal of THF,
the residue was washed with n-hexane. Recrystallization from a
THF/toluene solution gave 2 (0.5 toluene) as almost colorless
1
crystals (0.28 g, 88%): H NMR (C6D6) δ 5.26 (m, 1H), 4.84 (m,
1H), 4.67 (m, 1H), 4.53 (m, 1H) (C5H4), 3.30 (s, 1H) (cage CH),
All other chemicals were purchased from either Aldrich or Acros
Chemical Co. and used as received unless otherwise noted. Infrared
spectra were obtained from KBr pellets prepared in the glovebox
1.94-0.91 (m, 39H) (C(CH3)2 + Cy), -10.58 (dd, 2H, 2JPH ) 30.0
2
Hz, JHH ) 3.0 Hz) (Ru-H2); 13C{1H} NMR (C6D6) δ 84.6, 83.7,
1
1
82.5, 82.2 (C5H4), 65.1 (cage C), 40.1 (C(CH3)2), 39.4 (d, JCP
)
on a Perkin-Elmer 1600 Fourier transform spectrometer. H and
2
13C NMR spectra were recorded on a Bruker DPX 300 spectrometer
at 300.0 and 75.5 MHz, respectively. 11B and 31P NMR spectra
were recorded on a Varian Inova 400 spectrometer at 128.0 and
162.0 MHz. All chemical shifts were reported in δ units with
references to the residual protons of the deuterated solvents for
proton and carbon chemical shifts, to external BF3 ·OEt2 (0.00 ppm)
for boron chemical shifts, and to external 85% H3PO4 (0.00 ppm)
31.5 Hz), 32.0 (d, JCP ) 9.4 Hz), 31.5, 30.3, 27.9, 27.1 (PCy +
C(CH3)2); 31P{1H} NMR (C6D6) δ 82.2; 11B NMR (C6D6) δ 11.2
(s, 1B), -1.8 (d, J ) 147 Hz, 1B), -4.0 (d, J ) 133 Hz, 1B),
-7.0 (d, J ) 151 Hz, 2B), -9.6 (d, J ) 159 Hz, 2B), -10.7 (d, J
) 140 Hz, 2B), -14.4 (d, J ) 156 Hz, 1B); IR (KBr, cm-1) ν
2576 (vs) (B-H), 1958 (m) (Ru-H). Anal. Calcd for C28H55B10PRu
(2): C, 53.22; H, 8.77. Found: C, 52.80; H, 8.45.
9
16108 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008

Metal-Carbon to Metal-Boron Bond Conversion
A R T I C L E S
2
Scheme 6
129.0, 127.4 (d, JCP ) 9.2 Hz), 123.0 (aryl C), 81.1, 77.4, 77.3,
2
76.7 (C5H4), 63.0 (cage C), 60.6 (d, JCP ) 9.2 Hz, OCH2), 40.6
(C(CH3)2), 33.8, 27.7 (C(CH3)2), 15.9 (CH2CH3); 31P{1H} NMR
2
2
(CDCl3) δ 145.0 (d, JPP) 68.4 Hz, 1P), 54.5 (d, JPP) 68.4 Hz,
1P); 11B NMR (CDCl3) δ 15.6 (s, 1B), -3.2 (d, J ) 171 Hz, 1B),
-4.6 (d, J ) 147 Hz, 1B), -7.9 (d, J ) 143 Hz, 1B), -10.6 (d, J
) 141 Hz, 3B), -12.0 (d, J ) 133 Hz, 2B), -15.0 (d, J ) 151
Hz, 1B); IR (KBr, cm-1) ν 2533 (vs) (B-H). Anal. Calcd for
C34H50B10O3P2Ru (5): C, 52.50; H, 6.48. Found: C, 52.78; H, 6.17.
Preparation of [η5:σB-Me2C(C5H4)(C2B10H10)]Ru(PPh3)(Py) (6).
Pyridine (0.08 g, 1.00 mmol) was added to a toluene solution (10
mL) of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PPh3) (3; 0.32 g, 0.50
mmol), and the mixture was heated to reflux for 2 days. After
removal of the solvent, the residue was washed with hexane and
recrystallized from DME at room temperature to give 6 as pale
1
yellow crystals (0.28 g, 81%): H NMR (benzene-d6) δ 9.10 (m,
2H), 6.59 (m, 1H), 6.05 (m, 2H) (C5H5N), 7.56 (m, 6H), 6.99(m,
9H) (aryl H), 4.57 (m, 1H), 4.39 (m, 2H), 3.35 (m, 1H) (C5H4),
2.52 (s, 1H) (cage CH), 1.46 (s, 3H), 0.79 (s, 3H) (C(CH3)2);
13C{1H} NMR (benzene-d6) δ 159.2, 135.2, 134.5, 129.4 (d, JCP
1
) 31.3 Hz), 127.7 (d, 2JCP ) 8.0 Hz), 122.9, 117.3 (aryl C), 93.6,
89.3, 73.1, 72.9 (C5H4), 63.7, 61.6 (cage C), 41.7 (C(CH3)2), 33.8,
28.9 (C(CH3)2); 31P{1H} NMR (benzene-d6) δ 66.9; 11B NMR
(benzene-d6) δ 18.2 (1B), -2.2 (d, J ) 159 Hz, 1B), -4.3 (d, J )
149 Hz, 2B), -9.6 (d, J ) 132 Hz, 3B), -11.4 (d, J ) 160 Hz,
2B), -14.6 (d, J ) 148 Hz, 1B); IR (KBr, cm-1) ν 2557 (vs)
(B-H). Anal. Calcd for C33H40B10NPRu (6): C, 57.37; H, 5.84; N,
2.03. Found: C, 57.55; H, 5.64; N, 1.76.
Preparation of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PPh3) (3).
This complex was prepared as almost colorless crystals from [η5:
σC-Me2C(C5H4)(C2B10H10)]Ru(COD) (1; 0.23 g, 0.50 mmol), PPh3
(0.13 g, 0.50 mmol), THF (10 mL), and dihydrogen using the same
procedures reported for 2: yield 0.30 g (87%). Single crystals of
3·C6H6 suitable for X-ray analyses were grown from a benzene
1
solution: H NMR (C6D6) δ 7.63 (m, 6H), 7.09 (m, 9H) (aryl H),
5.21 (m, 1H), 4.87 (m, 1H), 4.40 (m, 1H), 4.18 (m, 1H) (C5H4),
3.20 (s, 1H) (cage CH), 1.25 (s, 3H), 0.84 (s, 3H) (C(CH3)2), -9.60
(dd, 2H, 2JPH ) 30.0 Hz, 2JHH ) 3.0 Hz) (Ru-H2); 13C{1H} NMR
Preparation of [{[η5:σB-Me2C(C5H4)(C2B10H10)]RuH(PPh3)}-
{K(DME)}]2 (7). To a THF (10 mL) solution of [η5:σB-Me2C-
(C5H4)(C2B10H10)]RuH2(PPh3) (3; 0.32 g, 0.50 mmol) was added
KH powder (0.04 g, 1.00 mmol), and the mixture was then heated
to reflux for 3 days. After filtration and removal of THF, the residue
was recrystallized from DME to give 7 as yellow crystals (0.32 g,
1
2
(C6D6) δ 139.6 (d, JCP ) 49.7 Hz), 133.6 (d, JCP ) 11.4 Hz),
129.8, 117.4 (aryl C), 85.3, 85.1, 84.1 (C5H4), 64.9 (cage C), 40.0
(C(CH3)2), 32.3, 29.6 (C(CH3)2); 31P{1H} NMR (C6D6) δ 63.3;
11B NMR (C6D6) δ 9.6 (s, 1B), -1.8 (d, J ) 138 Hz, 1B), -3.6
(d, J ) 145 Hz, 1B), -6.5 (d, J ) 126 Hz, 1B), -10.3 (d, J ) 137
Hz, 2B), -10.8 (d, J ) 110 Hz, 3B), -13.8 (d, J ) 133 Hz, 1B);
IR (KBr, cm-1) ν 2582 (vs) (B-H), 1990 (m) (Ru-H). Anal. Calcd
for C34H43B10PRu (3 + C6H6): C, 59.03; H, 6.26. Found: C, 58.84;
H, 5.78.
1
85%): H NMR (pyridine-d5) δ 8.17 (m, 6H), 7.25 (m, 9H) (aryl
H), 5.46 (m, 1H), 5.00 (m, 1H), 4.80 (m, 1H), 4.21 (m, 1H) (C5H4),
3.48 (s, 5H), 3.25 (s, 6H) (DME + cage CH), 1.64 (s, 3H), 1.34
(s, 3H) (C(CH3)2), -11.75 (d, 2JPH ) 30.0 Hz, 1H) (Ru-H); 13C{1H}
NMR (pyridine-d5) δ 134.9 (d, 1JCP ) 22.5 Hz), 129.4, 127.8, 127.3
2
Preparation of [η5:σB-Me2C(C5H4)(C2B10H10)]Ru(dppe) (4). A
toluene solution (15 mL) of [η5:σB-Me2C(C5H4)(C2B10H10)]-
RuH2(PPh3) (3; 0.32 g, 0.50 mmol) and dppe (0.20 g, 0.50 mmol)
was heated to reflux for 5 days. After removal of toluene, the residue
was washed with hexane (10 mL). Recrystallization from a CH2Cl2
solution gave 4 as yellow crystals (0.30 g, 80%): 1H NMR (CDCl3)
δ 7.86-6.96 (m, 20H) (aryl H), 5.46 (m, 1H), 5.28 (m, 1H), 5.19
(m, 1H), 4.53 (m, 1H) (C5H4), 2.35 (s, 1H) (cage CH), 2.77 (m,
2H), 2.10 (m, 2H) (CH2CH2), 1.49 (s, 3H), 1.15 (s, 3H) (C(CH3)2);
(d, JCP ) 8.3 Hz) (aryl C), 87.5, 85.5, 79.7, 77.8, 76.9 (C5H4),
64.5 (cage C), 68.2, 66.1 (DME), 40.9 (C(CH3)2), 33.8, 30.7
(C(CH3)2); 31P{1H} NMR (pyridine-d5) δ 77.8; 11B NMR (pyridine-
d5) δ -4.4 (d, J ) 157 Hz, 1B), -6.4 (d, J ) 168 Hz, 1B), -9.1
(d, J ) 150 Hz, 1B), -11.5 (d, J ) 178 Hz, 3B), -19.7 (d, J )
134 Hz, 3B), -43.1 (s, 1B); IR (KBr, cm-1) ν 2572 (vs) (B-H).
Anal. Calcd for C64H92B20K2O4P2Ru2 (7): C, 51.80; H, 6.25. Found:
C, 52.21; H, 6.25.
X-ray Structure Determination. All single crystals were im-
mersed in Paraton-N oil and sealed under nitrogen in thin-walled
glass capillaries. Data were collected at 293 K on a Bruker SMART
1000 CCD diffractometer using Mo KR radiation. An empirical
absorption correction was applied using the SADABS program.24
All structures were solved by direct methods and subsequent Fourier
difference techniques and refine anisotropically for all non-hydrogen
atoms by full-matrix least-squares on F2 using the SHELXTL
program package.25 For the noncentrosymmetric structure of 4, the
appropriate enantiomorph was chosen by refining Flack’s parameter
x toward zero.26 The cage carbon atoms were located by comparing
the bond lengths as the average distance between the carbon and
carbon/boron atoms would appear shorter than that between the
boron atoms. All hydrogen atoms were geometrically fixed using
the riding model. Complexes 2 and 3 showed the solvation of half
1
13C{1H} NMR (CDCl3) δ 132.7 (d, JCP ) 37.6 Hz), 132.5 (d,
2
1JCP ) 40.4 Hz), 132.2, 131.1 (d, JCP ) 10.5 Hz), 129.5, 128.3
2
(d, JCP ) 9.0 Hz), 128.1, 127.6 (aryl C), 90.8, 81.5, 78.9, 75.6
(C5H4), 68.3, 61.7 (cage C), 41.1 (C(CH3)2), 33.8, 28.6 (C(CH3)2),
25.9 (t, 1JCP ) 35.4 Hz) (CH2CH2); 31P{1H} NMR (CDCl3) δ 89.3,
87.6; 11B NMR (CDCl3) δ 15.0 (s, 1B), -2.7 (d, J ) 136 Hz, 1B),
-4.4 (d, J ) 135 Hz, 1B), -8.6 (d, J ) 157 Hz, 2B), -10.0 (d, J
) 133 Hz, 3B), -12.4 (d, J ) 132 Hz, 1B), -14.7 (d, J ) 155
Hz, 1B); IR (KBr) νBH 2563 (s) cm-1. Anal. Calcd for
C36H44B10P2Ru (4): C, 57.82; H, 5.93. Found: C, 57.70; H, 5.79.
Preparation of [η5:σB-Me2C(C5H4)(C2B10H10)]Ru(PPh3)[P(OEt)3]
(5). Triethyl phosphate (0.17 g, 1.00 mmol) was added to a toluene
solution (10 mL) of [η5:σB-Me2C(C5H4)(C2B10H10)]RuH2(PPh3) (3;
0.32 g, 0.50 mmol), and the mixture was heated to reflux for 12 h.
After removal of the solvent, the residue was washed with hexane
and recrystallized from CH2Cl2 at room temperature to give 5 as
pale yellow crystals (0.30 g, 77%): 1H NMR (CDCl3) δ 7.42-7.27
(m, 15H) (aryl H), 4.79 (m, 1H), 4.65 (m, 1H), 4.43 (m, 1H), 3.99
(m, 1H) (C5H4), 3.73 (m, 6H) (OCH2), 3.12 (s, 1H) (cage CH),
(24) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Go¨ttingen,
Germany, 1996.
(25) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure Deter-
mination Software Programs; Bruker Analytical X-ray systems, Inc.:
Madison, WI, 1997.
3
1.45 (s, 3H), 1.23 (s, 3H) (C(CH3)2), 1.09 (t, J ) 6.9 Hz, 9H)
1
(CH2CH3); 13C{1H} NMR (CDCl3) δ 134.2 (d, JCP ) 35.4 Hz),
(26) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
9
J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008 16109

A R T I C L E S
Liu et al.
toluene and one benzene. Crystal data and details of data collection
and structure refinements are given in Table 2. Further details are
included in the Supporting Information.
are indeed connecting two relevant minima. The effective core
potentials (ECPs) of Hay and Wadt with double- valence basis
sets (LanL2DZ)29 were used to describe Ru and P. Polarization
functions were also added for Ru ( f ) 1.235) and P ( d ) 0.387).30
The 6-31G basis set was used for all the other atoms.31 All the
calculations were performed with the Gaussian03 software pack-
age.32
Computational Details. Full geometry optimizations of all the
model complexes were done at the Becke3LYP (B3LYP) level of
density functional theory (DFT).27 Frequency calculations had also
been performed at the same level of theory to identify all the
stationary points as minima (zero imaginary frequency) or transition
states (one imaginary frequency) and to provide free energy at
298.15 K, which include entropic contributions by taking into
account the vibrational, rotational, and translational motions of the
species under consideration. Transition states were located using
the Berny algorithm. Intrinsic reaction coordinates (IRC)28 were
calculated for the transition states to confirm that such structures
Acknowledgment. This work was supported by grants from
the Research Grants Council of The Hong Kong Special Admin-
istration Region (Project No. 403906 to Z.X. and HKUST 601507
to Z.L.).
Supporting Information Available: Complete ref 32; crystal-
lographic data in CIF format for 2·0.5C7H8, 3·C6H6, 4, 5, 6,
and 7. This material is available free of charge via the Internet
at http://pubs.acs.org.
(27) (a) Becke, A. D. Phys. ReV. A 1988, 38, 3098. (b) Miehlich, B.; Savin,
A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200. (c) Lee,
C.; Yang, W.; Parr, G. Phys. ReV. B 1988, 37, 785.
(28) (a) Fukui, K. J. Phys. Chem. 1970, 74, 4161. (b) Fukui, K. Acc. Chem.
Res. 1981, 14, 363.
JA8067098
(29) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1995, 82, 299.
(30) (a) Ehlers, A. W.; Bo¨hme, M.; Dapprich, S.; Gobbi, A.; Ho¨llwarth,
A.; Jonas, V.; Ko¨hler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking,
G. Chem. Phys. Lett. 1993, 208, 111. (b) Ho¨llwarth, A.; Bo¨hme, M.;
Dapprich, S.; Ehlers, A. W.; Obbi, A. G.; Jonas, V.; Ko¨hler, K. F.;
Stegmann, R.; Veldkamp, A.; Frenking, G. Chem. Phys. Lett. 1993,
208, 238.
(31) (a) Gordon, M. S. Chem. Phys. Lett. 1980, 76, 163. (b) Hariharan,
P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213. (c) Binning,
R. C., Jr.; Curtiss, L. A. J. Comput. Chem. 1990, 11, 1206.
(32) Frisch, M. J.; Gaussian 03, revision B05; Gaussian, Inc.: Pittsburgh,
PA, 2003.
9
16110 J. AM. CHEM. SOC. VOL. 130, NO. 47, 2008