Syntheses and reactivity of cationic borane-ruthenium complexes [(η5-C5R5)Ru(PMe3) 2(η1-BH3·EMe3)][BAr 4f] (R = H, Me; e = N, P; BAr4f = [B{3,5-C6H3(CF3)2}4])

Article abstract of DOI:10.1021/om0604324

Chloride displacement from [(η⁵-C₅R ₅)Ru(PMe₃)₂Cl] by Na[BAr₄ ^f] in the presence of BH₃·EMe₃ afforded cationic borane σ complexes containing an unsupported B-H-Ru bridge, [(η⁵-C₅R₅)Ru(PMe₃) ₂(η¹-BH₃·EMe₃)][BAr ₄^f] (4a: R = H, EMe₃ = PMe₃; 4b: R = Me, EMe₃ = PMe₃; 4c: R = H, EMe₃ = NMe ₃; [BAr₄^f] = [B{3,5-C₆H ₃(CF₃)₂}₄]). Compounds 4a-c were fully characterized, and their structures were determined by X-ray crystallographic analysis. In these complexes, the borane ligand is coordinated to the ruthenium atom through a B-H-Ru three-center two-electron bond. They exhibit fluxional behavior due to site exchange between the BH hydrogen atoms. Complexes 4a and 4c are remarkably stable. However, they are hydrolyzed by a trace amount of water to produce a cationic dihydride, trans-[CpRuH ₂-(PMe₃)₂]⁺ (6, Cp = η⁵-C₅H₅). The reactivity of 4a toward various substrates was investigated.

Full text of DOI:10.1021/om0604324

4420
Organometallics 2006, 25, 4420-4426
Syntheses and Reactivity of Cationic Borane-Ruthenium Complexes
[(η5-C5R5)Ru(PMe3)2(η1-BH3‚EMe3)][BArf4] (R ) H, Me; E ) N, P;
BArf4 ) [B{3,5-C6H3(CF3)2}4])
Yasuro Kawano,* Masahiro Hashiva, and Mamoru Shimoi*
Department of Basic Science, Graduate School of Arts and Sciences, UniVersity of Tokyo,
Meguro-ku, Tokyo 153-8902, Japan
ReceiVed May 18, 2006
Chloride displacement from [(η5-C5R5)Ru(PMe3)2Cl] by Na[BArf4] in the presence of BH3‚EMe3 afforded
cationic borane σ complexes containing an unsupported B-H-Ru bridge, [(η5-C5R5)Ru(PMe3)2(η1-BH3‚
EMe3)][BArf4] (4a: R ) H, EMe3 ) PMe3; 4b: R ) Me, EMe3 ) PMe3; 4c: R ) H, EMe3 ) NMe3;
[BArf4] ) [B{3,5-C6H3(CF3)2}4]). Compounds 4a-c were fully characterized, and their structures were
determined by X-ray crystallographic analysis. In these complexes, the borane ligand is coordinated to
the ruthenium atom through a B-H-Ru three-center two-electron bond. They exhibit fluxional behavior
due to site exchange between the BH hydrogen atoms. Complexes 4a and 4c are remarkably stable.
However, they are hydrolyzed by a trace amount of water to produce a cationic dihydride, trans-[CpRuH2-
(PMe3)2]+ (6, Cp ) η5-C5H5). The reactivity of 4a toward various substrates was investigated.
of this relationship, study of the coordination chemistry of
borane-Lewis base adducts would be of interest in that it might
have an impact not only on boron chemistry but also on basic
coordination chemistry including alkane activation. During the
course of our study on this subject, we have obtained several
borane σ complexes, in which a BH σ bond acts as a
two-electron donor.5-7 For example, the complexes [M(CO)5-
(η1-BH3‚L)] (1: M ) Cr, W; L ) NMe3, PMe3, PPh3) and
[CpMn(CO)2(η1-BH3‚L)] (2: L ) NMe3, PMe3) were synthe-
sized by photolyses of the respective metal carbonyl in the
presence of BH3‚L adducts. They were isolated as crystalline
solids, and their structures were determined by X-ray diffraction.
These compounds are equivalent to transient alkane complexes,
[M(CO)5(alkane)] (A)8 and [CpMn(CO)2(alkane)],9 [CpRe(CO)2-
(alkane)] (B),10 respectively (Chart 1). The coordinated borane
adduct is so labile that compounds 1 and 2 decompose in a few
days at room temperature through borane dissociation.
Theoretical calculations provided information on the nature
of the borane-metal bonding in these complexes. The BH σ
orbital is largely stabilized by interaction with the metal dσ
orbital. On the other hand, the high energy of the BH σ* orbital
prevents metal back-donation into this antibonding orbital. The
borane-metal interaction can thus be described as a combination
of the predominant borane-to-metal electron donation and very
Introduction
Activation of an inert p-block element-hydrogen σ bond by
a transiton metal complex has been an important subject in
organometallic chemistry. In particular, CH bond activation of
alkanes has been attracting much interest.1 How do the most
inert species, alkanes, interact with transition metals? This is
quite a fundamental issue in coordination chemistry. It is also
of importance for the effective use of petroleum resources. In
many cases, alkane activation (oxidative addition/reductive
elimination) is thought to proceed through an intermediate
alkane σ complex.2 However, owing to their extremely labile
nature, investigation of alkane complexes has been performed
at very low temperature or by the use of flash photolysis
techniques.3 Thus, the structure and properties of alkane
complexes have not been established in detail.4
Monoborane-Lewis base adducts, BH3‚L (L ) neutral Lewis
base), are charge-neutral and isoelectronic with alkanes. Because
* Corresponding authors. E-mail: ykawano@mbh.nifty.com; cshimoi@
mail.ecc.u-tokyo.ac.jp.
(1) For example: (a) Shilov, A. E.; Shul’pin, G. B. Chem. ReV. 1997,
97, 2879. (b) Catalysis by Metal Complexes, VI, 21. ActiVation and Catalytic
Reactions of Saturated Hydrocarbons in the Presence of Metal Complexes;
Shilov, A. E., Shul’pin, G. B., Eds.; Kluwer: Dordrecht, 2000.
(2) For example: (a) Ziegler, T.; Tschinke, V.; Fan, L.; Becke, A. D. J.
Am. Chem. Soc. 1989, 111, 9177. (b) Periana, R. A.; Bergmann, R. G. J.
Am. Chem. Soc. 1986, 108, 7332. (c) Bullock, R. M.; Headford, C. E. L.;
Hennessy, K. M.; Kegley, S. E.; Norton, J. R. J. Am. Chem. Soc. 1989,
111, 3897. (d) Gould, G. L.; Heinekey, D. M. J. Am. Chem. Soc. 1989,
111, 5502. (e) Wick, D. D.; Reynolds, K. A.; Jones, W. D. J. Am. Chem.
Soc. 1999, 121, 3974. (f) Mobley, T. A.; Schade, C. Bergmann, R. G. J.
Am. Chem. Soc. 1995, 117, 7822.
(5) Shimoi, M.; Nagai, S.; Ichikawa, M.; Kawano, Y.; Katoh, K.; Uruichi,
M.; Ogino, H. J. Am. Chem. Soc. 1999, 121, 11704.
(6) Kakizawa, T.; Kawano, Y.; Shimoi, M. Organometallics 2001, 20,
3211.
(7) Yasue, T.; Kawano, Y.; Shimoi, M. Angew. Chem., Int. Ed. 2003,
42, 1727.
(3) For example: (a) Kubas, G. J. Metal Dihydrogen and σ-Bond
Complexes; Kluwer Academic/Plenum Publishers: New York, 2001; pp
365-415. (b) Hall, C.; Perutz, R. N. Chem. ReV. 1996, 96, 3125, and
references therein.
(4) Two reports have documented crystallographic evidence of significant
interactions between an alkane and a metal center. In these works, however,
the metal-coordinated hydrogen atoms were not located directly. (a)
n-Heptane-double A-frame porphyrin iron(II) complex: Evans, D. R.;
Drovetskaya, T.; Bau, R.; Reed, C. A.; Boyd, P. D. W. J. Am. Chem. Soc.
1997, 119, 3633. (b) Alkane-macrocyclic ligand uranium(III) complexes:
Castro-Rodriguez, I.; Nakai, H.; Gantzel, P.; Zakharov, L. N.; Rheingold,
A. L.; Meyer, K. J. Am. Chem. Soc. 2003, 125, 15734.
(8) For example: (a) Graham, M. A.; Poliakoff, M.; Turner, J. J. J. Chem.
Soc. (A) 1971, 2939. (b) Sun, X.-Z.; Grills, D. C.; Nikiforov, S. M.;
Poliakoff, M.; George, M. W. J. Am. Chem. Soc. 1997, 119, 7521. (c) Zaric,
S.; Hall, M. B. J. Phys. Chem. A 1997, 101, 4646.
(9) (a) Klassen, J. K.; Selke, M.; Sorensen, A. A.; Yang, G. K. J. Am.
Chem. Soc. 1990, 112, 1267. (b) Johnson, F. P. A.; George, M. W.;
Bagratashvili, V. N.; Vereshchagina, L. N.; Poliakoff, M. MendeleeV
Commun. 1991, 26.
(10) (a) Sun, X.-Z.; Grills, D. C.; Nikiforov, S. M.; Poliakoff, M.; George,
M. W. J. Am. Chem. Soc. 1997, 119, 7521. (b) Geftakis, S.; Ball, G. E. J.
Am. Chem. Soc. 1998, 120, 9953. (c) Lawes, D. J.; Geftakis, S.; Ball, G. E.
J. Am. Chem. Soc. 2005, 127, 4134.
10.1021/om0604324 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 08/01/2006

Syntheses of Cationic Borane-Ruthenium Complexes
Organometallics, Vol. 25, No. 18, 2006 4421
Chart 1
Scheme 2
Chart 2
Scheme 1
little back-donation.5,6 At this point, σ complexes of borane
adducts are quite different from those of three-coordinate
boranes, e.g., [(η5-C5H4Me)Mn(CO)2(HBX2)] (HBX2 ) HB-
(1,2-O2C6H4), pinacolborane, HB(cyclo-C6H11)2)11 and [Cp2Ti-
(HB(1,2-O2C6H4))2],12,13 in which the vacant boron p orbital
accepts metal electron back-donation. Such a bonding scheme
suggests a high affinity of tetracoordinate borane adducts toward
positively charged metal fragments.
an electron-donating borane adduct (particularly the hydridic
BH hydrogen). Thus, the M-H interaction is weak while the
BH bond remains strong. Consequently, neutral borane com-
plexes readily lose the borane ligand. On the other hand, in the
cationic system 3 the metal center is so eletrophilic that it
effectively accepts the electron density from the borane and
strongly interacts with a BH hydrogen. Accordingly, the M-H
interaction is enhanced while the B-H bond is considerably
weakened. If a positively charged but inherently electron-rich
metal center was used, stable borane complexes containing a
well-balanced B-H-M bridge could be obtained (Scheme 2).
On the basis of this working hypothesis, we attempted to
synthesize new borane complexes of the [(C5R5)Ru(PMe3)2]+
(R ) H, Me) metal fragment.17 As expected, we found that this
16-electron cation forms highly stable complexes with borane
adducts.
While our research project was in progress, closely related
compounds [(η5-C5R5)Ru(η2-BH2X‚PPh2CH2PPh2)]+ (C) and
[(η5-C5R5)Ru(L)(η1-BH2X‚PPh2CH2PPh2)]+ (D) (X ) H, Cl)
were reported by Weller and co-workers (Chart 2).18,19 In C
and D, the phosphineborane moiety coordinates to the ruthenium
atom through a monodentate or a bidentate mode and is
supported by the diphosphine to form a chelate ring. Compound
C (X ) H) shows interesting H/D exchange on boron when it
is exposed to a D2 atmosphere. Some derivatives bearing a
diphosphine-supported borane ligand have also been reported
by Weller (E)20 and Barton (F, G).21 In addition, we have
reported a cationic copper complex that contains chelating
diborane(4) ligands (H).22
We have already reported a cationic manganese-borane
system, [Mn(CO)4(PR3)(η1-BH3‚PMe3)][BArf4] (3, PR3 ) PMe2-
Ph, PEt3).7 Manganese boryls [Mn(CO)4(PR3)(BH2‚PMe3)]
undergo protonation with a Bro¨nsted acid with a weakly
coordinating anion, [H(OEt2)2][BArf4], to produce the σ com-
plexes. Compounds 3 decompose at room temperature in a few
days to give a neutral hydride [MnH(CO)4(PR3)] and minor
products including [BH2‚2PMe3]+ (Scheme 1). This indicates
the occurrence of heterolytic cleavage of the metal-coordinated
BH bond to form H- and [BH2‚PMe3]+. Owing to the high
electrophilicity of the cationic metal center, the electron density
of the borane ligand is drawn to the central metal through the
bridging hydrogen atom. Such polarization induces the hetero-
lytic cleavage of BH.14 This BH bond activation is characteristic
of the cationic systems and is in sharp contrast to the neutral
borane complexes, which show borane dissociation exclusively.
Existence of this decomposition route hampers isolation of 3
in pure forms and thus its crystallographic analysis. Relevant
heterolytic activation of H2 and hydrosilanes on highly elec-
trophilic [M(CO)5-n(PR3)n]+ (M ) Mn, Re, n ) 1, 2) has been
reported by Kubas and co-workers.15,16
The aforementioned findings and insight into the M-H-B
linkage imply the following inference. When the metal center
is electron-rich (charge-neutral), it can interact only weakly with
(11) Schlecht, S.; Hartwig, J. F. J. Am. Chem. Soc. 2000, 122, 9435.
(12) (a) Hartwig, J. F.; Muhoro, C. N.; He, X.; Einstein, O.; Bosque, R.;
Maseras, F. J. Am. Chem. Soc. 1996, 118, 10936. (b) Muhoro, C. N.;
Hartwig, J. F. Angew. Chem., Int. Ed. 1999, 38, 1510. (c) Muhoro, C. N.;
He, X.; Hartwig, J. F. J. Am. Chem. Soc. 1999, 121, 5033.
(13) Lam, W. H.; Lin, Z. Organometallics 2000, 19, 2625.
(14) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789
(15) Huhmann-Vincent, J.; Scott, B. L.; Kubas, G. J. J. Am. Chem. Soc.
1998, 120, 6808.
(16) (a) Huhmann-Vincent, J.; Scott, B. L.; Kubas, G. J. Inorg. Chim.
Acta 1999, 294, 240. (b) Fang, X.; Huhmann-Vincent, J.; Scott, B. L.; Kubas,
G. J. J. Organomet. Chem. 2000, 609, 95. (c) Fang, X.; Scott, B. L.; John,
K. D.; Kubas, G. J. Organometallics 2000, 19, 4141.
(17) Davies, S. G.; Mcnally, J. P.; Smallridge, A. J. AdV. Organomet.
Chem. 1990, 30, 1.
(18) Merle, N.; Kocok-Ko¨hn, G.; Mabon, M. F.; Frost, C. G.; Ruggerio,
G. D.; Weller, A. S. Dalton Trans. 2004, 3883.
(19) Merle, N.; Frost, C. G.; Kocok-Ko¨hn, G.; Willis, M. C.; Weller, A.
S. J. Organomet. Chem. 2005, 690, 2829.
(20) Ingleson, M.; Patmore, N. J.; Ruggerio, G. D.; Frost, C. G.; Mahon,
M. F.; Willis, M. C.; Weller, A. S. Organometallics 2001, 20, 4434.
(21) (a) Macias, R.; Rath, N. P.; Barton, L. Angew. Chem., Int. Ed. 1999,
38, 162. (b) Volkov, O.; Mac´ıas, R.; Rath, N. P.; Barton L. Inorg. Chem.
2002, 41, 5837.

4422 Organometallics, Vol. 25, No. 18, 2006
Kawano et al.
Results and Discussion
Synthesis and Structures of Cationic Ruthenium Borane
Complexes 4a-c. Treatment of [CpRu(PMe3)2Cl] with Na-
[BArf4] in the presence of BH3‚PMe3 in dichloromethane gave
an orange solution with concurrent precipitation of NaCl. After
filtration of the salt, the solution was concentrated and cooled
to -30 °C to yield a new borane complex, [CpRu(PMe3)2(η1-
BH3‚PMe3)][BArf4] (4a), as yellow crystals in 73% yield. In a
similar manner, the pentamethylcyclopentadienyl derivative 4b
and the BH3‚NMe3 analogue of 4a, complex 4c, were obtained
in moderate yield (eq 1).
Figure 1. Structure of the cationic moiety of [CpRu(PMe3)2(η1-
BH3‚PMe3)][BArf4] (4a). One of the disordered Cp ligands is
displayed. The thermal ellipsoids are drawn at the 30% probability
level. The methyl hydrogen atoms are omitted for the sake of clarity.
Surprisingly, 4a and 4c were air-stable in the solid state. These
compounds also showed remarkable thermal stability in solution.
They do not reveal any signs of decomposition after 1 week in
dry dichloromethane-d2. Compound 4b was somewhat heat-
sensitive, so that its preparation had to be carried out below
-15 °C.
Crystals suitable for X-ray diffraction study were grown by
slow diffusion of hexane vapor into their 1,2-dichloroethane
(4a and 4c) or dichloromethane (4b) solutions. Figures 1-3
exhibit the structures of the cationic moieties of 4a, 4b, and
4c, respectively. The key structural parameters are listed in Table
1. In crystals of 4a and 4b, the cation is loosely packed in a
cavity made by the bulky anions. Accordingly, they have rather
large thermal ellipsoids despite the data collection being
performed at 153 K. As shown in the figures, the cations adopt
a three-legged piano stool geometry, and the borane ligand is
coordinated to the ruthenium atom through a B-H-Ru three-
center two-electron bond. The hydrogen atoms attached to boron
were found by the difference Fourier syntheses, and their
positions were refined isotropically. The three complexes have
similar structures. In 4b, however, the borane ligand is pushed
down by the methyl groups on the five-membered ring, so that
it is located at the position opposite the Cp* ligand.
Figure 2. Structure of the cationic moiety of [Cp*Ru(PMe3)2(η1-
BH3‚PMe3)][BArf4] (4b). The thermal ellipsoids are drawn at the
30% probability level. The methyl hydrogen atoms are omitted for
clarity.
The Ru‚‚‚B(1) interatomic distances are 2.586(5), 2.611(6),
and 2.648(3) Å for 4a, 4b, and 4c, respectively. These values
are much longer than the ruthenium-boron bond distance of a
related borylruthenium complex, [Cp*Ru(CO)2(BH2‚PMe3)]
(2.243(8) Å),23 as well as Braunschweig’s compounds [CpRu-
(CO)2B(NMe2)BCl(NMe2)] and [CpRu(CO)2B(Cl)NSiMe3-
BClN(SiMe3)2] (2.173(3) and 2.115(2) Å, respectively).24 They
are also substantially longer than the ruthenium-silicon separa-
tion of a silane σ complex prepared by Lemke, [CpRu(PMe3)2-
(HSiCl3)]+, 2.329(1) Å.25 Therefore, it is quite reasonable to
describe the borane-metal interaction in 4 as an end-on, η1
coordination. Weller’s complexes [(η5-C5R5)Ru(L)(η1-BH3‚
dppm)] (R ) H, Me, L ) PMe3, P(OMe)3, see Chart 2, D)
have similar ruthenium-boron interatomic distances (2.499-
Figure 3. Structure of the cationic moiety of [CpRu(PMe3)2(η1-
BH3‚NMe3)][BArf4] (4c). The thermal ellipsoids are drawn at the
30% probability level.
(8)-2.5904(19) Å).18 The long Ru‚‚‚B separation reflects minor
back-donation into the high-lying BH σ* orbitals.
Structural optimization of 4a at the DFT/B3LYP level of
theory reproduced the X-ray structure well, although the
orientation of the borane ligand differs slightly probably because
of packing effects (Figure 4). In the optimized structure, the
ruthenium-coordinated BH has a bond distance of 1.274 Å,
which is longer than the terminal BH bonds (1.199, 1.205 Å,
Table 2). In the crystal structures, the bridging BH bond length
is also comparable to or longer than the terminal BH, although
the standard deviations are large (see Table 1). These phenomena
(22) Shimoi, M.; Katoh, K.; Tobita, H.; Ogino, H. Inorg. Chem. 1990,
29, 814.
(23) Yasue, T.; Kawano, Y.; Shimoi, M. Chem. Lett. 2000, 58.
(24) (a) Braunschweig H.; Koster M.; Wang R. Inorg. Chem. 1999, 38,
415. (b) Braunschweig H.; Kollann, C.; Klinkhammer K. W. Eur. J. Inorg.
Chem. 1999, 1523.
(25) (a) Lemke, F. R. J. Am. Chem. Soc. 1994, 116, 11183. (b) Freeman
S. T. N.; Lemke F. R.; Brammer, L. Organometallics 2002, 21, 2030.

Syntheses of Cationic Borane-Ruthenium Complexes
Organometallics, Vol. 25, No. 18, 2006 4423
Table 1. Selected Interatomic Distances (Å) and Bond
Angles (deg) for [(η5-C5R5)Ru(PMe3)2(η1-BH3‚EMe3)][BArf4]
(4a-c)
Table 2. Selected Structural Parameters in the
DFT-Optimized Geometry of the Cations 4a and 5a
4a
Ru‚‚‚B
2.764
1.274
1.996
127.04
Ru-H
1.802
1.199, 1.205
2.420, 2.445
4a
4b
4c
B-H(brid)
B-P
B-H(term)
Ru-P
CNT-Rua
Ru-P(1)
Ru-P(2)
1.845(11)
2.2729(14)
2.3112(13)
2.586(5)
1.92(4)
1.28(4)
1.26(5)
1.30(5)
1.885(5)
2.3069(15)
2.2779(16)
2.611(6)
1.83(4)
1.27(4)
1.26(6)
1.22(6)
1.862(3)
2.2996(8)
2.2773(8)
2.648(3)
1.65(3)
1.37(3)
1.07(3)
1.07(3)
Ru-H-B
Ru‚‚‚B(1)
Ru-H(B1)
B(1)-H(B1)
B(1)-H(B2)
B(1)-H(B3)
B(1)-Eb
5a
Ru-B
B-H
Ru-P
2.318
1.211, 1.207
2.421, 2.428
Ru-H(hydrido)
B-P
B-Ru-H
1.604
2.032
128.65
1.913(5)
1.927(6)
1.615(3)
CNT-Ru-P(1)a
CNT-Ru-P(2)a
CNT-Ru-H(B1)a
CNT-Ru-B(1)a
P(1)-Ru-H(B1)
P(1)-Ru-B(1)
119.7(3)
126.7 (4)
123.7(14)
120.5(4)
80.8(13)
104.80(14)
99.0(13)
81.96(12)
95.20(5)
106(3)
119(3)
114(3)
121(3)
89(2)
105(3)
100(2)
125.8(2)
123.6(2)
128.4(17)
116.3(2)
91.7(11)
82.28(16)
79.1(12)
104.77(16)
95.30(9)
113(5)
115(3)
122(3)
113(4)
95.8(18)
102(3)
122.74(12)
122.62(12)
130.0(13)
122.11(13)
94.4(11)
80.94(7)
81.1(12)
104.05(7)
94.61(3)
123(2)
123(2)
106(2)
114(2)
99.8(14)
106.8(16)
103.8(18)
substantially higher than that between [Cr(CO)5] and BH3‚PMe3
(78.6 kJ mol-1).29 This should be responsible for the stability
of compounds 4.
Solution Behavior of Borane Complexes 4. In the 11B NMR
spectra of 4, the signal of the ruthenium-coordinated borane
appeared at 5-10 ppm higher field in comparison to the
corresponding free borane. Such a chemical shift change of the
11B NMR signal on coordination has also been found in borane
complexes that we prepared.5-7 In the 1H NMR, compounds 4
display the signals of Cp, ruthenium-coordinated PMe3, boron-
coordinated PMe3 or NMe3, and the BArf4 anion at reasonable
positions. At 18 °C, 4a exhibits only one BH resonance at -4.51
ppm as a boron-coupled broad hump with 3H intensity,
indicating rapid exchange between them. This signal collapsed
into the baseline at -40 °C, and at -90 °C two distinct signals
appeared at -15.53 and 0.77 ppm, which are attributed to the
metal-coordinated and terminal BH hydrogen atoms. The energy
of activation for the fluxional process was estimated to be 38
( 1 kJ mol-1 at 233 K. Likewise, the activation barrier for the
BH exchange of 4b was 36 ( 1 kJ mol-1 at 226 K. For the
amineborane complex 4c, the coalescence point was 10 °C, so
that the BH signal was not found deceptively at ambient
temperature. However, they were observed at -17.04 and 2.06
ppm at -100 °C (∆Gq ) 46 ( 1 kJ mol-1 at 283 K). Similar
fluxional behaviors have been observed in other complexes of
borane adducts, and the barrier for the exchange varies depend-
ing on the metal fragment and Lewis base on boron.5-7,27,30
Girolami and co-workers have reported dynamic behavior of
a methyl(hydride) osmium complex, [Cp*OsH(Me)(PMe2CH2-
PMe2)]+.31 In the 1H NMR spectrum, this compound shows line
broadening of the methyl and hydride signals above -100 °C,
indicating generation of an intermediate methane complex
(through an arrested reductive elimination) and site exchange
between the methane hydrogen atoms. A theoretical study
showed that the methane σ complex lies ca. 25 kJ mol-1 above
the (methyl)hydride (eq 2).32,33
P(2)-Ru-H(B1)
P(2)-Ru-B(1)
P(1)-Ru-P(2)
Ru-H(B1)-B(1)
H(B1)-B(1)-H(B2)
H(B1)-B(1)-H(B3)
H(B2)-B(1)-H(B3)
E-B(1)-H(B1)b
E-B(1)-H(B2)b
E-B(1)-H(B3)b
104(3)
a CNT ) the centroid of the Cp or Cp* ligand. For 4a, one of the
disordered Cp rings is exhibited. b E ) P(3) (4a, 4b), N (4c).
Figure 4. DFT-optimized structures and relative energy (given in
kJ mol-1) of 4a and 5a.
are in agreement with the decrease of the bond order of the BH
bond on coordination to the metal. Moreover, the coordinated
BH bond appears to be more elongated in 4a-c than in neutral
borane complexes 1 and 2, in which the corresponding bond
distances are found to be 1.12-1.19 Å (X-ray) or around 1.25
Å (DFT).5,6,26,27 This is probably attributed to the pronounced
polarization of the BH bond caused by the coordination to an
electrophilic, positively charged ruthenium center.
DFT calculations also showed that a structural isomer, the
trans-boryl(hydride) (5a), was at an energy minimum, but it
was 80.6 kJ mol-1 higher than 4a (Figure 4). This indicates
that oxidative addition of BH3‚PMe3 to [RuCp(PMe3)2]+ is
unfavorable. In contrast, isoelectronic [Cp*Ru(PMe3)2H(Me)]+
adopts a methyl(hydride) structure with a trans geometry. No
bonding interaction is found between the methyl and hydrido
ligands.28 The binding energy between [CpRu(PMe3)2]+ and
BH3‚PMe3 was calculated to be 109 kJ mol-1. This value is
The fluxional behavior and optimized geometry of the
osmium-methane complex resemble those of 4. However, the
relative stability of the σ complex and oxidative addition product
is reversed in 4 and Girolami’s compound.
(26) (a) Katoh, K.; Shimoi, M.; Ogino, H. Inorg. Chem. 1992, 31, 670.
(b) Shimoi, M.; Katoh, K.; Ogino, H. J. Chem. Soc., Chem. Commun. 1990,
811.
(27) Kawano, Y.; Kakizawa, T.; Yamaguchi, K.; Shimoi, M. Chem. Lett.
2006, 35, 568.
(28) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J.
E. J. Am. Chem. Soc. 1987, 109, 1444.
(29) Kawano, Y.; Shimoi, M. Manuscript in preparation.
(30) Shimoi, M.; Katoh, K.; Kodama, G.; Kawano, Y.; Ogino, H. J.
Organomet. Chem. 2002, 659, 102.
(31) Gross, C. L. Girolami, G. S. J. Am. Chem. Soc. 1998, 120, 6605.
(32) Martin, R. L. J. Am. Chem. Soc. 1999, 121, 9459.
(33) Szilagyi, R. K.; Musaev, D. G.; Morokuma, K. Organometallics
2002, 21, 555.

4424 Organometallics, Vol. 25, No. 18, 2006
Kawano et al.
Scheme 3
Scheme 5
Scheme 6
Scheme 4
Reactivity of Ruthenium Borane Complexes. Despite the
high thermal stability, compounds 4a and 4c are hydrolyzed
by a trace amount of water to be converted into a cationic
dihydride, trans-[CpRuH2(PMe3)2]+ (6),34 in several days.
Hydrolysis of the deuterium-labeled derivative [CpRu(PMe3)2-
(η1-BD3‚PMe3)][BArf4] provided the monodeuteride, [CpRuHD-
(PMe3)2]+. This implies heterolytic cleavage of the coordinated
BH bond assisted by the attack of water (Scheme 3). Presum-
ably, a water molecule attacks the boron atom to generate a
neutral hydride [CpRuH(PMe3)2] and [BH2(OH2)‚PMe3]+. The
electron-rich hydride is protonated by the oxonium ion to
produce 6.
The hydrolysis of 4 is closely akin to heterolytic activation
of a hydrosilane on an iron complex, [Cp*Fe(CO)(PEt3)-
(HSiEt3)]+, reported by Brookhart. The in-situ-generated silane
complex decomposes in the presence of trace water to produce
[Cp*Fe(CO)(PEt3)(η2-H2)]+. The primary step of this reaction
was thought to involve heterolytic cleavage of the coordinated
SiH bond; thereby [Cp*FeH(CO)(PEt3)] and [SiEt3]+ were
generated. The silylium ion is coordinated with water in the
system, and the resulting silyloxonium ion [SiEt3‚OH2]+ pro-
tonates the hydride.35
Reaction of 4a with diphenylsilane resulted in rapid formation
of the dihydride 6 with dissociation of BH3‚PMe3 (Scheme 4).
When Ph2SiD2 was used, the dideuteride complex formed,
indicating that the hydride ligands came from silane. Thus, the
borane-silane exchange took place on ruthenium and was
followed by double SiH activation. In fact, the SiHCl3 complex
[CpRu(PMe3)2(HSiCl3)]+ has been isolated and structurally
authenticated by Lemke.25 Note that addition of Ph2SiH2 or Ph3-
SiH to the manganese-borane complex [CpMn(CO)2(η1-BH3‚
NMe3)] (2) provided the corresponding silane complex as a
stable product.6
When 4a or 4c was treated with [PPh4]Cl in dichloromethane,
the chloro complex [CpRu(PMe3)2Cl] was produced with borane
dissociation. If heterolytic cleavage of BH occurred during this
reaction, BH2Cl‚PMe3 should be formed, leaving a hydride on
ruthenium. However, only simple ligand exchange was observed
in this case (Scheme 5). On one hand, the triflate [PPh4](OSO2-
CF3) did not react with 4a, indicating that BH3‚PMe3 coordinates
to [CpRu(PMe3)2]+ more strongly than the triflate ion.
Reactions of 4a with two-electron donors lead to simple
ligand substitution (Scheme 6). Compound 4a reacted with CO
and CH3CN to yield the corresponding carbonyl and acetonitrile
complexes,36 respectively. These reactions required about 12 h
for completion, unlike neutral borane derivatives, 1 and 2.
Formation of the acetonitrile complex contrasts with Weller’s
compounds [CpRu(PR3)(η1-BH3‚PPh2CH2PPh2)][PF6] (R ) Me,
OMe), which were prepared by addition of BH3‚PPh2CH2PPh2
and PR3 to the acetonitrile adduct [CpRu(NCMe)3][PF6].18 The
reaction between 4a and 4-(dimethylamino)pyridine (dmap)
produced [CpRu(PMe3)2(dmap)]+. However, it changed into a
complicated mixture after 2 h at ambient temperature. Treatment
of 4a with phenylacetylene afforded the vinylidene complex
[CpRu(PMe3)2(dCdCHPh)]+.37 Rearrangement of terminal
alkyne π complexes to vinylidene derivatives is well known.38
Also in this system, replacement of the borane ligand by the
alkyne initially probably took place.
(34) (a) Lemke, F. R.; Brammer, L. Organometallics 1995, 14, 3980.
(b) Brammer, L.; Klooster, W. T.; Lemke, F. R. Organometallics 1996,
(36) Bruce, M. I.; Wong, F. S.; Skelton, B. W.; White, A. H. J. Chem.
Soc., Dalton Trans. 1981, 1398.
15, 1721.
(37) Treichel, P. M.; Komar, D. A. Inorg. Chim. Acta 1980, 42, 277.
(38) Bustero, E.; Carbo´, J. J.; Lledo´s, A.; Mereiter, K.; Puerta, M. C.
Valerga, P. J. Am. Chem. Soc. 2003, 125, 3311.
(35) Scharrer, E.; Chang, S.; Brookhart, M. Organometallics 1995, 14,
5686.

Syntheses of Cationic Borane-Ruthenium Complexes
Organometallics, Vol. 25, No. 18, 2006 4425
Table 3. Crystal Data for Compounds 4a, 4b, and 4c
4a
4b
4c
empirical formula
fw
C46H47B2F24P3Ru
1271.44
yellow
153(2)
0.71073
monoclinic
P21/n
14.010(7)
25.638(16)
15.420(9)
90
94.33(3)
90
5523(5)
4
C51H57B2F24P3Ru
1341.57
yellow-orange
153(2)
0.71073
monoclinic
P21/c
12.668(3)
12.786(3)
37.507(6)
90
100.204(7)
90
C46H47B2F24NP2Ru
1254.48
yellow
153(2)
0.71073
triclinic
P1h
13.281(4)
13.699(4)
15.245(4)
90.169(11)
106.835(12)
95.719(11)
2640.1(13)
2
cryst color
temperature/K
wavelength
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
5979(2)
4
1.490
0.451
Z
D(calcd)/Mg m-3
abs coeff/mm-1
F(000)
1.529
0.484
2552
1.578
0.476
1260
2712
cryst size/mm
θ range/deg
index ranges
0.40 × 0.20 × 0.10
3.03 to 27.49
0 e h e 18,
0 e k e 33,
-19 e l e 19
12 591
0.40 × 0.30 × 0.25
3.19 to 27.49
0 e h e 16,
0 e k e 16,
-48 e l e 47
13 612
0.40 × 0.20 × 0.15
2.99 to 27.48
0 e h e 17,
-17 e k e 17,
-19 e l e 18
11 949
no. of indep reflns
no. of params
820
1.009
868
1.029
762
1.057
GooF on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole/e Å-3
R1 ) 0.0486, wR2 ) 0.1380
R1 ) 0.0691, wR2 ) 0.1494
1.041 and -0.591
R1 ) 0.0619, wR2 ) 0.1547
R1 ) 0.1036, wR2 ) 0.1795
0.970 and -1.128
R1 ) 0.0348, wR2 ) 0.1019
R1 ) 0.0421, wR2 ) 1110
0.506 and -0.964
5H, C5H5), 1.48 (vt, 2JPH ) 4.6 Hz, 18H, Ru-PMe3), 1.36 (d, 2JPH
) 11.5 Hz, 9H, BH3‚PMe3), -4.51 (br, 3H, BH). The BH resonance
split into two signals at -15.53 (1H, B-H-M) and 0.77 ppm (2H,
terminal BH) at -90 °C. 11B{1H} NMR (160.35 MHz, CD2Cl2):
Experimental Section
All manipulations were carried out under high vacuum or dry
nitrogen atmosphere. Reagent-grade hexane was distilled under a
nitrogen atmosphere from sodium-benzophenone ketyl immediately
before use. Dichloromethane was dried over CaH2 and distilled
before use. CD2Cl2 was dried over 4 Å molecular sieves and
vacuum-transferred into NMR tubes. BH3‚PMe3,39 [CpRu(PMe3)2-
Cl],40 [Cp*Ru(PMe3)2Cl],41 and Na[BArf4]42 were prepared accord-
ing to the literature. BH3‚NMe3, PhCtCH, AgOSO2CF3 (Wako
Pure Chemicals), 4-(dimethylamino)pyridine (Tokyo Kasei), Ph2-
SiH2, Ph2SiD2, and [PPh4]Cl (Aldrich) were purchased and used
without further purification. NMR spectra were recorded on a JEOL
R-500 spectrometer. IR spectra were recorded on a Jasco FTIR-
350 spectrometer.
NMR Data for [BArf4]-. 1H NMR (500 MHz, CD2Cl2): δ 7.73
(s, 8H, ortho-H), 7.57 (s, 4H, para-H). 13C NMR (125 MHz, CD2-
Cl2): δ 161.9 (q, 1JBC ) 49.8 Hz, ipso-C), 135.1 (s, ortho-C), 129.1
(q, 2JCF ) 31.5 Hz, meta-C), 124.7 (q, 1JCF ) 272.6 Hz, CF3). 11B-
{1H} NMR (160.35 MHz, CD2Cl2): δ -6.5. These data are
essentially identical for compounds 4a-4c and, therefore, will not
be repeated in the following paragraphs.
Synthesis of [CpRu(PMe3)2(η1-BH3‚PMe3)][BArf4] (4a). An
H-shaped reaction tube separated with a glass filter was charged
with [CpRu(PMe3)2Cl] (35.4 mg, 0.100 mmol), Na[BArf4] (89.0
mg, 0.100 mmol), and BH3‚PMe3 (12.0 mg, 0.133 mmol). Into the
reaction vessel, dichloromethane (3 mL) was introduced under high
vacuum at -196 °C. The resulting mixture was warmed gradually
and stirred at -84 °C for 1 h and then at room temperature for 3
h. A white precipitate of NaCl was filtered, and the orange filtrate
was concentrated to ca. 1 mL. The solution was diluted with hexane
(1 mL) and cooled to -25 °C to provide 4a (91.3 mg, 0.072 mmol,
72%) as yellow crystals. 1H NMR (500 MHz, CD2Cl2): δ 4.59 (s,
1
δ -47.0 ppm (br d, JBP ) 68 Hz). 31P{1H} NMR (202.35 MHz,
CD2Cl2): δ 5.1 (Ru-PMe3), -3.2 (br, BH3‚PMe3). 13C NMR (125
MHz, CD2Cl2): δ 79.1 (C5H5), 22.4 (vt, JPC ) 16.0 Hz, Ru-PMe3),
1
11.4 (d, JPC ) 40.3 Hz, BH3‚PMe3). IR (Nujol mull): ν(BH)
2454.0, 2408.2 cm-1. Anal. Calcd for C46H47B2F24P3Ru: C, 43.45;
H, 3.73. Found: C, 43.35; H, 3.85. The mass spectrum of this
compound (FAB, sulfolane) gave poor data probably due to its easy
fragmentation. The same was encountered in 4b and 4c.
Synthesis of [Cp*Ru(PMe3)2(η1-BH3‚PMe3)][BArf4] (4b). A
dichloromethane solution of [Cp*Ru(PMe3)2Cl] (42.3 mg, 0.100
mmol), Na[BArf4] (88.8 mg, 0.100 mmol), and BH3‚PMe3 (11.2
mg, 0.125 mmol) was stirred under high vacuum at -84 °C for 1
h and then at -15 °C for 1 day. After filtration of NaCl, the filtrate
was concentrated, diluted with hexane, and cooled to -80 °C to
yield 4b (82.4 mg, 0.061 mmol, 61%) as yellow-orange crystals.
1H NMR (500 MHz, CD2Cl2): δ 1.56 (s, 15H, C5Me5), 1.42 (vt,
2JPH ) 4.6 Hz, 18H, Ru-PMe3), 1.39 (d, 2JPH ) 11.0 Hz, 9H, BH3‚
PMe3), -4.62 (br, 3H, BH). The last resonance was divided into
two peaks at -15.62 and 0.49 ppm at -100 °C. 11B{1H} NMR
1
(160.35 MHz, CD2Cl2): δ -41.8 (br, d, JBP ) 73 Hz). 31P{1H}
NMR (202.35 MHz, CD2Cl2): δ 1.9 (Ru-PMe3), -3.3 (q, br, BH3‚
PMe3). 13C NMR (125 MHz, CD2Cl2): δ 90.9 (C5Me5), 21.8 (dd,
JPC ) 15.5, 14.5 Hz, Ru-PMe3), 12.8 (d, JPC ) 40.3 Hz, BH3‚
PMe3), 11.6 (C5Me5). IR (Nujol mull): ν(BH) 2466.0, 2421.1 cm-1
.
Anal. Calcd for C51H57B2F24P3: C, 45.66; H, 4.28. Found: C, 44.98;
H, 4.42.
Synthesis of [CpRu(PMe3)2(η1-BH3‚NMe3)][BArf4] (4c). This
compound was prepared by a method similar to that used for 4a,
using BH3‚NMe3 instead of BH3‚PMe3. Yellow crystalline 4c (75.6
mg, 0.06 mmol, 70%) was obtained from [CpRu(PMe3)2Cl] (30.4
mg, 0.086 mmol), Na[BArf4] (77.8 mg, 0.088 mmol), and BH3‚
(39) Hewitt, F.; Holliday, A. K. J. Chem. Soc. 1953, 530.
(40) Treichel, P. M.; Komar, D. A.; Vincenti, P. J. Synth. React. Inorg.
Met. Org. Chem. 1984, 14, 383.
(41) Tilley, T. D.; Grubbs, R. H.; Bercaw, J. Organometallics 1984, 3,
274.
(42) Brookhart, M. Grant, B.; Vople, A. F., Jr. Organometallics 1992,
11, 3920.
1
NMe3 (9.0 mg, 0.123 mmol). H NMR (500 MHz, CD2Cl2): δ
2
4.61 (s, 5H, C5H5), 2.60 (s, 9H, NMe3), 1.48 (vt, JPH ) 4.6 Hz,
18H, PMe3). At -100 °C, the bridging and terminal BH resonances
were observed at -17.04 and 2.06 ppm, respectively (2:1 intensity).

4426 Organometallics, Vol. 25, No. 18, 2006
Kawano et al.
11B{1H} NMR (160.35 MHz, CD2Cl2): δ -17.5 ppm (br). 31P NMR
(202.35 MHz, CD2Cl2): δ 4.7. 13C NMR (125 MHz, CD2Cl2): δ
79.1 (C5H5), 22.2 (vt, JPC ) 15.9 Hz, PMe3), 39.9 (NMe3). IR (Nujol
mull): ν(BH) 2481.5, 2437.3 cm-1. Anal. Calcd for C46H47B2F24-
NP2Ru: C, 44.04; H, 3.78; N, 1.12. Found: C, 44.17; H, 3.92; N,
0.93.
Hydrolysis of 4a and 4c. Dilute solutions of 4a and 4c in wet
dichloromethane-d2 were allowed to stand at room temperature, and
1H and 11B NMR spectra were recorded periodically. After 5 days,
the resonances of trans-[CpRuH2(PMe3)2]+ appeared with disap-
pearance of those of 4.
(dmap)]+ (CD2Cl2) are as follows: δ 7.85, 6.30 (d, J ) 7.3 Hz,
2H × 2, ring protons of dmap), 4.53 (s, 5H, C5H5), 2.97 (s, 6H,
2
dmap), 1.49 (vt, JPH ) 5.3 Hz, 9H, PMe3).
Reaction of 4a with Phenylacetylene. The reaction of 4a (13.8
mg, 0.011 mmol) with phenylacetylene (1.1 mg, 0.011 mmol) was
1
monitored by the means of NMR spectroscopy. The resulting H
and 13C NMR spectra showed the occurrence of an instantaneous
reaction to afford [CpRu(PMe3)2(dCdCHPh)]+ in quantitative
yield.
X-ray Crystal Structure Determination. Crystals of 4a, 4b,
and 4c were grown by slow diffusion of hexane into 1,2-
dichloroethane (4a, 4c) or dichloromethane (4b) solutions. Intensity
data were collected on a Rigaku RAPID imaging plate diffracto-
meter using graphite-monochromated Mo KR radiation (λ )
0.71073 Å). Data collection was carried out at -120 °C. Crystal
data, data collection parameters, and convergence results are listed
in Table 3.
Numerical absorption corrections were applied on the crystal
shapes. The structures of all complexes were solved by the direct
method and refined on F2. All non-hydrogen atoms were located
and refined applying anisotropic temperature factors. Coordinates
of hydrogen atoms bound to the boron atom were determined by
the difference Fourier syntheses and were refined isotropically.
Positions of other hydrogen atoms were idealized by using riding
models. Some of the CF3 groups in the [BArf4]- anion were
disordered around the local C3 axis. In 4a, the cyclopentadienyl
group was also disordered over the two sites. Refinement of the
positions of the carbon atoms was accomplished by the use of a
rigid model with a regular pentagon. Calculations were performed
using the program package SHELX 97.43
DFT Calculations. The geometries of [CpRu(PMe3)2(η1-BH3‚
PMe3)]+ (4a), trans-[CpRu(H)(PMe3)2(BH2‚PMe3)]+ (5a), [CpRu-
(PMe3)2]+, and BH3‚PMe3 were optimized at the B3LYP level of
theory, a density functional theory (DFT) type of calculation based
on hybrid functionals. A basis set with an approximation of effective
core potentials, LanL2DZ, was employed for all the atoms.
Vibration analyses were then performed to characterize the station-
ary points. Calculations were performed with the Gaussian 98W
package of programs.44
Reaction of 4a with Ph2SiH2 or Ph2SiD2. To a dichloromethane-
d2 (0.5 mL) solution of 4a (6.2 mg, 0.005 mmol) was added Ph2-
SiH2 (1.3 mg, 0.007 mmol) via a microsyringe at room temperature,
and the 1H NMR spectrum was recorded immediately. The spectrum
indicated formation of trans-[CpRuH2(PMe3)2]+. Likewise, Ph2SiD2
1
2
was added to a solution of 4a. In the H and H NMR spectra of
the resulting mixture, the signals of trans-[CpRuD2(PMe3)2]+ were
observed.
Reaction of 4a with [PPh4]Cl. An NMR tube was charged with
4a (5.9 mg, 0.005 mmol) and [PPh4]Cl (2.0 mg, 0.005 mmol), and
CD2Cl2 (0.5 mL) was introduced under vacuum at -196 °C. After
1
warming the mixture to room temperature, the H and 11B NMR
spectra were recorded. They indicated quantitative formation of
[CpRu(PMe3)2Cl] and BH3‚PMe3. A similar reaction of 4c produced
[CpRu(PMe3)2Cl] and BH3‚NMe3 quantitatively.
Preparation of [PPh4](OSO2CF3). Samples of [PPh4]Cl (250
mg, 0.67 mmol) and AgOSO3CF3 (171 mg, 0.67 mmol) were
combined in CH2Cl2 (15 mL) and stirred at room temperature for
80 min. After filtration of precipitated AgCl, the filtrate was
concentrated to ca. 1 mL. To the solution, hexane (3 mL) was added
to provide [PPh4](OSO2CF3) (282 mg, 0.58 mol, 86%) as a white
powder.
Reaction of 4a with [PPh4](OSO2CF3). Samples of 4a (37 mg,
0.029 mmol) and [PPh4](OSO2CF3) (15 mg, 0.029 mmol) were
dissolved in CD2Cl2 (0.5 mL). The solution was allowed to stand
for 24 h, and the 1H and 11B NMR spectra were recorded. However,
no reaction was observed.
Reaction of 4a with Carbon Monoxide. A CH2Cl2 (0.5 mL)
solution of 4a (21 mg, 0.017 mmol) was placed in an NMR tube
connected to a Young’s stopcock. The reaction vessel was evacuated
and refilled with carbon monoxide. The contents were left at room
temperature with occasional shaking. After 12 h, the yellow color
of 4a disappeared to give a very pale yellow solution. The solution
was evaporated to dryness, and acetone-d6 was introduced into the
Acknowledgment. This work was financially supported by
a Grant-in-Aid for Scientific Research (No. 15350193) from
the Japanese Ministry of Education, Science, Sports, and
Culture.
Supporting Information Available: Crystallographic informa-
tion files (CIF) for 4a, 4b, and 4c. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
NMR tube. The H NMR spectrum indicated nearly quantitative
formation of [CpRu(PMe3)2(CO)]+.
Reaction of 4a with Acetonitrile. In an NMR tube, 4a (17 mg,
0.013 mmol) was dissolved in acetonitrile (0.3 mL). The resulting
solution was allowed to stand at room temperature for 12 h.
Acetonitrile was removed under vacuum, and the residue was
OM0604324
(43) (a) Sheldrick, G. M. SHELXS-97; University of Go¨ttingen, 1997.
(b) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen, 1997.
(44) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.;
Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A.
D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi,
M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.;
Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick,
D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.;
Ortiz, J. V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi,
I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M.
W.; Johnson, B. G.; Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon,
M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revision A.11; Gaussian,
Inc.: Pittsburgh, PA, 1998.
1
redissolved in CDCl3 (0.5 mL). The H NMR spectrum of the
yellow solution indicated almost quantitative formation of [CpRu-
(PMe3)2(NCMe)]+.
Reaction of 4a with 4-(Dimethylamino)pyridine (dmap).
Samples of 4a (10.8 mg, 0.009 mmol) and dmap (1.4 mg, 0.012
mmol) were combined in CD2Cl2 at -196 °C in an NMR tube.
The mixture was warmed to ambient temperature, and the reaction
1
was monitored by H NMR spectroscopy. After 10 min, 50% of
4a was consumed, and signals of [CpRu(PMe3)2(dmap)]+ appeared
along with those of free BH3‚PMe3. The spectrum changed into
that of a complex mixture after 2 h. 1H NMR data of [CpRu(PMe3)2-