Synthesis and protonation of [RuH(NBD)(2,6-(Ph2PCH2)2C6H3 )]

Article abstract of DOI:10.1021/om020521q

Treatment of [RuCl(PPh₃)(PCh₃)] (PCP = 2,6-(Ph₂PCH₂)₂C₆H₃) with norbornadiene (NBD) in the presence of CuCl produces [RuCl(NBD)(PCP)]. Reaction of [RuCl(NBD)(PCP)] with TlOTf gives [Ru(OTf)(NBD)(PCP)], which reacts with NaBH₄ to produce [RuH(NBD)(PCP)]. Protonation of [RuH(NBD)(PCP)] with acetic acid in the presence of PPh₃ gives norbornene and [Ru(OAc)(PPh₃)(PCP)]. Protonation of [RuH(NBD)(PCP)] with HOTf gives norbornane and [Ru(OTf)(NBD)(PCP)]. Protonation of [RuH(NBD)(PCP)] with HOTf in the presence of MeCN gives norbornene, [Ru(MeCN)(NBD)(PCP)]OTf, and [Ru(MeCN)₃(PCP)]OTf. In the protonation reactions, the NBD is likely hydrogenated through the dihydrogen intermediate [Ru(H₂)(NBD)(PCP)]⁺. A computational study shows that hydrogen transfer from the dihydrogen to the NBD ligand of [Ru(H₂)(NBD)(PCP)]⁺ proceeds through a stepwise mechanism.

Full text of DOI:10.1021/om020521q

Organometallics 2002, 21, 4281-4292
4281
Syn th esis a n d P r oton a tion of
[Ru H(NBD)(2,6-(P h 2P CH2)2C6H3)]
Sheng Hua Liu,† Sze Ming Ng,† Ting Bin Wen,† Zhong Yuan Zhou,‡
Zhenyang Lin,*,† Chak Po Lau,*,‡ and Guochen J ia*,†
Department of Chemistry, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong, and Department of Applied Biology & Chemical
Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Received J uly 2, 2002
Treatment of [RuCl(PPh3)(PCP)] (PCP ) 2,6-(Ph2PCH2)2C6H3) with norbornadiene (NBD)
in the presence of CuCl produces [RuCl(NBD)(PCP)]. Reaction of [RuCl(NBD)(PCP)] with
TlOTf gives [Ru(OTf)(NBD)(PCP)], which reacts with NaBH4 to produce [RuH(NBD)(PCP)].
Protonation of [RuH(NBD)(PCP)] with acetic acid in the presence of PPh3 gives norbornene
and [Ru(OAc)(PPh3)(PCP)]. Protonation of [RuH(NBD)(PCP)] with HOTf gives norbornane
and [Ru(OTf)(NBD)(PCP)]. Protonation of [RuH(NBD)(PCP)] with HOTf in the presence of
MeCN gives norbornene, [Ru(MeCN)(NBD)(PCP)]OTf, and [Ru(MeCN)3(PCP)]OTf. In the
protonation reactions, the NBD is likely hydrogenated through the dihydrogen intermediate
[Ru(H2)(NBD)(PCP)]+. A computational study shows that hydrogen transfer from the
dihydrogen to the NBD ligand of [Ru(H2)(NBD)(PCP)]+ proceeds through a stepwise
mechanism.
In tr od u ction
groups such as alkyls, vinyls,3 and acetylides4 to form
[MHLn] and RH. These reactions have also been pro-
posed or inferred as the key steps in the catalytic
hydrogenation of olefins and acetylenes.5-8 Hydrogen
transfer from a coordinated dihydrogen ligand to the
â-carbons of vinylidene ligands has been proposed for
the reactions of [OsCl2H2(P(i-Pr)3)2] with HCtCR to give
the carbyne complexes [OsCl2H(tCCH2R)(P(i-Pr)3)2] via
the intermediates [OsCl2(H2)(dCdCCHR)(P(i-Pr)3)2].9
This work is related to the reactivity of coordinated
dihydrogen toward olefin ligands. Olefin-dihydrogen
complexes have been suggested as intermediates in
several catalytic reactions.8,10-11 For example, the di-
hydrogen complexes [M(H2)(η4-NBD)(CO)3] (M ) Cr,
Mo, W) have been proposed as the intermediates for
Studies on the reactivity of coordinated dihydrogen
toward organic ligands (e.g. alkyls, vinyls, acetylides,
vinylidenes, olefins) are of fundamental importance,
because such investigations may help to understand the
mechanisms of reactions involving dihydrogen com-
plexes1,2 and to develop new chemistry and catalytic
reactions based on σ-complexes. In the past decade,
significant progress has been made in this direction. It
has been demonstrated with well-defined dihydrogen
complexes that complexes of the type [M(R)(H2)Ln] can
undergo intramolecular hydrogen transfer from the
coordinated dihydrogen ligand to the R-carbon of R
† The Hong Kong University of Science and Technology.
‡ The Hong Kong Polytechnic University.
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10.1021/om020521q CCC: $22.00 © 2002 American Chemical Society
Publication on Web 08/29/2002

4282 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
Sch em e 1
photocatalytic hydrogenation of norbornadiene using
[M(CO)6];10 the complexes [Rh{(2,6-C6H3Me2)NCMe-
CHCMeN(2,6-C6H3Me2)}(H2)(olefin)] were proposed as
the intermediates for catalytic hydrogenation of olefins
using [Rh{(2,6-C6H3Me2)NCMeCHCMeN(2,6-C6H3Me2)}-
(COE)],11 and the complexes [Ru(Tp)(PPh3)(H2)(olefin)]+
were thought to be involved in catalytic hydrogenation
of olefins using [Ru(Tp)(PPh3)x(CH3CN)3-x]+ (x ) 1, 2).8
A few olefin-dihydrogen complexes have been charac-
terized by IR10 and NMR11,12 spectroscopy. To model
reactions involving olefin-dihydrogen complexes, it is
obviously desirable to demonstrate stoichiometric in-
tramolecular hydrogen transfer (from dihydrogen to
olefin ligands) reactions of olefin-dihydrogen com-
plexes. However, very little work has been previously
done in this regard. In our approach to model stoichio-
metric hydrogen transfer from H2 to olefin ligands, we
have studied protonation reactions of [MH(olefin)Ln],12
hoping that the protonation reactions may give [M(H2)-
(olefin)Ln]+ or hydrogen-transferred products. In our
previous study, we have shown that protonation of [Ru-
(Cp*)H(NBD)], where H is cis to both of the double
bonds of NBD, produces the hydrogenated product
nortricyclene.12a In this work, the protonation reactions
of [RuH(NBD)(PCP)] (PCP ) 2,6-(Ph2PCH2)2C6H3) were
investigated. [RuH(NBD)(PCP)] is different from [Ru-
(Cp*)H(NBD)] in that the hydride is only cis to one of
the double bonds of NBD. Thus, this provides us an
opportunity to see how the position of the hydride
relative to the double bonds of NBD may affect the
reactivity. In a related study, Esteruelas et al. have
investigated the protonation reactions of [OsH2(diolefin)-
(P(i-Pr)3)2] (diolefin ) NBD, cyclohexadiene).13
In hydrogenation involving the olefin-dihydrogen
complexes [M(H2)(olefin)Ln], hydrogen transfer from the
coordinated H2 ligand to the olefin ligands could go
through a concerted mechanism or through a stepwise
mechanism in which one of the hydrogens from the
coordinated H2 is first transferred to the olefin ligands
to give the hydrido alkyl complexes [MH(alkyl)Ln]
followed by reductive elimination. However, detailed
pathways for the hydrogen transfer process have rarely
been addressed previously. In this work, we have
studied the reaction pathways for the conversion of [Ru-
(H2)(NBD)(PCP)]+ to [Ru(NBE)(PCP)]+ (NBE ) nor-
bornene) by computational chemistry, to see if the
hydrogen transfer process is stepwise or concerted.
tate olefin NBD and the tridentate PCP ligand have
been used in the study, because such a system may give
complexes with well-defined geometry. A number of
ruthenium15-18 and osmium19 complexes with PCP or
PCP-related ligands have been reported recently. In
these complexes, the PCP ligand is usually coordinated
to the metal centers in a meridional fashion.
The synthetic route to the hydride complex [RuH-
(NBD)(PCP)] (3) is outlined in Scheme 1. Treatment of
[RuCl(PPh3)(PCP)] (1) with NBD in the presence of
(14) See for example: (a) Schlaf, M.; Lough, A. J .; Morris, R. H.
Organometallics 1997, 16, 1253. (b) Bianchini, C.; Masi, D.; Peruzzini,
M.; Casarin, M.; Maccato, C.; Rizzi, G. A. Inorg. Chem. 1997, 36, 1061.
(c) Ayllo´n, J . A.; Gervaux, C.; Sabo-Etienne, S.; Chaudret, B. Organo-
metallics 1997, 16, 2000. (d) Rocchini, E.; Mezzetti, A.; Ru¨egger, H.;
Burckhardt, U.; Gramlich, V.; Del Zotto, A.; Martinuzzi, P.; Rigo, P.
Inorg. Chem. 1997, 36, 711. (e) Gusev, D. G.; Hu¨bener, R.; Orama, O.;
Berke, H. J . Am. Chem. Soc. 1997, 117, 3716 and references therein.
(f) Cappellani, E. P.; Drouin, S. D.; J ia, G.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T. J . Am. Chem. Soc. 1994, 116, 3375.
(15) (a) Dijkstra, H. P.; Albrecht, M.; van Koten, G. Chem. Commun.
2002, 126. (b) Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001,
40, 3750. (c) Dani, P.; Richter, B.; van Klink, G. P. M.; van Koten, G.
Eur. J . Inorg. Chem. 2001, 125. (d) Dani, P.; Toorneman, M. A. M.;
van Klink, G. P. M.; van Koten, G. Organometallics 2000, 19, 5287.
(e) Dani, P.; Albrecht, M.; van Klink, G. P. M.; van Koten, G.
Organometallics 2000, 19, 4468. (f) Dani, P.; Karlen, T.; Gossage, R.
A.; Gladiali, S.; van Koten, G. Angew. Chem., Int. Ed. 2000, 39, 743.
(g) Karlen, T.; Dani, P.; Grove, D. M.; Steenwinkel, P.; van Koten, G.
Organometallics 1996, 15, 5687.
(16) (a) Gusev, D. G.; Dolgushin, F. M.; Antipin, M. Y. Organome-
tallics 2000, 19, 3429. (b) Gusev, D. G.; Madott, M.; Dolgushin, F. M.;
Lyssenko, K. A.; Antipin, M. Y. Organometallics 2000, 19, 1734.
(17) van der Boom, M. E.; Kraatz, H. B.; Hassner, L.; Ben-David,
Y.; Milstein, D. Organometallics 1999, 18, 3873.
Resu lts a n d Discu ssion
Syn th esis of [Ru H(NBD)(P CP )]. As mentioned
previously, we intend to model stoichiometric intramo-
lecular hydrogen transfer from coordinated dihydrogen
to olefin ligands. It is known that protonation of
[RuH2L4] (L ) phosphine, phosphite) can produce the
dihydrogen complexes [RuH(H2)L4]+.14 Thus, we pre-
pared the hydride complex [RuH(NBD)(PCP)], expecting
that subsequent protonation of the hydride complex
would produce the dihydrogen complex [Ru(H2)(NBD)-
(PCP)]+ or hydrogen-transferred products. The biden-
(18) (a) J ia, G.; Lee, H. M.; Xia, H. P.; Williams, I. D. Organome-
tallics 1996, 15, 5453. (b) J ia, G.; Lee, H. M.; Williams, I. D. J .
Organomet. Chem. 1997, 534, 173. (c) Lee, H. M.; Yao, J . Z.; J ia, G.
Organometallics 1997, 16, 3927.
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(b) Liu, S. H.; Yang, S. Y.; Lo, S. T.; Xu, Z.; Ng, W. S.; Wen, T. B.;
Zhou, Z. Y.; Lin, Z.; Lau, C. P.; J ia, G. Organometallics 2001, 20, 4161.
(13) Castillo, A.; Esteruelas, M. A.; On˜ate, E.; Ruiz, N. J . Am. Chem.
Soc. 1997, 119, 9691.
(19) (a) Wen, T. B.; Cheung, Y. K.; Yao, J .; Wong, W. T.; Zhou, Z.
Y.; J ia, G. Organometallics 2000, 19, 3803. (b) Gusev, D. G.; Dolgushin,
F. M.; Antipin, M. Y. Organometallics 2001, 20, 1001. (c) Gauvin, R.
M.; Rozenberg, H.; Shimon, L. J . W.; Milstein, D. Organometallics
2001, 20, 1719.

[RuH(NBD)(2,6-(Ph2PCH2)2C6H3)]
Organometallics, Vol. 21, No. 20, 2002 4283
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
Deta ils for th e Com p lexes [Ru Cl(NBD)(P CP )] (2),
[Ru (OAc)(P P h 3)(P CP )] (6), a n d
[Ru (MeCN)(NBD)(P CP )]OTf (7)
2
6
7
formula
fw
C39H35ClP2Ru C52H45O2P3Ru C42H38F3NO3P2RuS
702.13
895.86
856.80
cryst syst
space group
orthorhombic triclinic
monoclinic
P21/c (No. 14)
P212121
(No. 19)a
P1h (No. 2)
a, Å
b, Å
c, Å
11.923(2)
13.351(3)
c ) 20.299(4) 19.997(3)
90
90
90
3231.3(11)
4
1.443
10.6517(16)
11.0510(16)
15.318(3)
14.450(2)
17.763(3)
90
104.142(3)
90
3812.8(10)
4
1.493
R, deg
â, deg
γ, deg
V, Å3
Z
89.891(3)
78.283(3)
71.252(3)
2177.5(6)
2
d
calcd, g cm-3
1.366
cryst dimens,
0.30 × 0.22 × 0.28 × 0.24 × 0.35 × 0.35 ×
mm
0.20
2.29-27.55
6.94
0.20
1.95-27.52
5.11
0.12
1.37-25.74
6.05
θ range, deg
abs coeff, cm-1
no. of rflns
collected
22 043
14 787
25 335
no. of indep
7449 (Rint
)
9874 (Rint
0.0185)
7955
)
8758 (Rint
0.0342)
5834
)
rflns
0.0267)
no. of obsd rflns 6717
(I > 2σ(I))
no. of params
388
523
478
F igu r e 1. Molecular structure of [RuCl(NBD)(PCP)].
refined
Hydrogen atoms are omitted for clarity.
goodness of fit
on F2
1.008
0.971
1.042
R1 (I > 2σ(I))
0.0261
0.0576
0.0319
0.0743
0.600
0.0474
0.1384
1.391
excess CuCl produced the chloro complex [RuCl(NBD)-
(PCP)] (2), which was isolated as a yellow solid in ca.
80% yield. No reaction was observed between 1 and
NBD if CuCl was not used. Cuprous chloride has been
shown to be a good phosphine scavenger.20 A recent
example of using CuCl as the scavenger of phosphines
was reported by Grubbs et al. in the isolation of [Ru-
(O-t-Bu)2(dCHPh)(PCy3)] from the reaction of [RuCl2-
(dCHPh)(PCy3)2] with KO-t-Bu.20b
wR2 (I > 2σ(I))
largest diff peak, 0.680
e Å-3
largest diff hole, -0.274
-0.328
-0.817
e Å-3
a
Absolute structure parameter: -0.033(18).
Ta ble 2. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Ru Cl(NBD)(P CP )] (2)
Ru(1)-P(1)
Ru(1)-Cl(1)
Ru(1)-C(9)
Ru(1)-C(12)
C(9)-C(14)
C(9)-C(10)
C(12)-C(13)
C(10)-C(15)
2.3816(7)
2.4309(7)
2.210(2)
2.285(3)
1.392(3)
1.545(4)
1.545(4)
1.544(4)
Ru(1)-P(2)
Ru(1)-C(1)
Ru(1)-C(11)
Ru(1)-C(14)
C(11)-C(12)
C(10)-C(11)
C(13)-C(14)
C(13)-C(15)
2.3632(7)
2.120(2)
2.286(2)
2.189(2)
1.370(4)
1.539(4)
1.530(4)
1.546(4)
The structure of 2 has been confirmed by an X-ray
diffraction study. The molecular structure of 2 is
depicted in Figure 1. The crystallographic details and
selected bond distances and angles are given in Tables
1 and 2, respectively. The structure of 2 can be described
as a distorted octahedron in which two vertexes are
occupied by the two double bonds of NBD and three
vertexes are occupied by a meridionally coordinated
PCP ligand. One of the double bonds of NBD is trans to
the chloride, while the other one is trans to the ipso
carbon of the PCP ligand. The bond distances between
ruthenium and the carbons of the double bond trans to
the chloride are slightly shorter than those between
ruthenium and the carbons of the double bond trans to
the aryl ligand, reflecting the stronger trans influence
of the aryl ligand. The Ru-C(olefin) bond distances are
similar to those of reported Ru(η4-NBD) complexes such
as [RuCl2(NBD)(PPh3)2],21 [Ru(η5-C9H7)Cl(NBD)],22 [Ru-
(Cp*)(NBD)(H2O)]BF4,23 and [RuX(NBD)(2,6-(Me2NCH2)2-
C6H3)] (X ) Cl, OTf).24 The structural feature asso-
ciated with the Ru(PCP) fragment is normal compared
P(1)-Ru(1)-P(2)
P(2)-Ru(1)-Cl(1)
C(1)-Ru(1)-P(1)
C(1)-Ru(1)-C(9)
152.49(2) P(1)-Ru(1)-Cl(1)
87.91(2) C(1)-Ru(1)-Cl(1)
79.75(6) C(1)-Ru(1)-P(2)
81.45(2)
93.81(7)
75.71(6)
101.44(9) C(1)-Ru(1)-C(14) 100.80(10)
C(1)-Ru(1)-C(11) 160.23(9) C(1)-Ru(1)-C(12) 158.98(9)
C(9)-Ru(1)-P(1)
119.93(6) C(14)-Ru(1)-P(1)
83.34(7)
83.93(7)
C(11)-Ru(1)-P(1) 118.46(7) C(12)-Ru(1)-P(1)
C(9)-Ru(1)-P(2)
C(11)-Ru(1)-P(2)
77.53(7) C(14)-Ru(1)-P(2) 113.20(7)
87.80(7) C(12)-Ru(1)-P(2) 122.68(7)
C(9)-Ru(1)-Cl(1) 155.46(6) C(14)-Ru(1)-Cl(1) 156.65(7)
C(11)-Ru(1)-Cl(1) 96.43(7) C(12)-Ru(1)-Cl(1)
96.79(8)
C(14)-Ru(1)-C(9)
C(9)-Ru(1)-C(11)
C(9)-Ru(1)-C(12)
36.89(9) C(12)-Ru(1)-C(11) 34.88(10)
63.75(10) C(14)-Ru(1)-C(12) 63.96(11)
75.43(10) C(14)-Ru(1)-C(11) 75.51(10)
to those of other structurally characterized Ru(PCP)
complexes such as [RuCl(PPh3)(PCP)]18b and [Ru(PCP)-
(PCHP)]OTf.15d
Consistent with the solid-state structure, the 31P{1H}
NMR spectrum of 2 in C6D6 showed a singlet at 55.4
(20) (a) Dias, E. L.; Nguyen, S. T.; Grubbs, R. H. J . Am. Chem. Soc.
1997, 119, 3887. (b) Sanford, M. S.; Henling, L. M.; Day, M. W.; Grubbs,
R. H. Angew. Chem., Int. Ed. 2000, 39, 3451. (c) Wakamatsu, H.;
Blechert, S. Angew. Chem., Int. Ed. 2002, 41, 794.
(21) Bergbreiter, D. E.; Bursten, B. E.; Bursten, M. S.; Cotton, F.
A. J . Organomet. Chem. 1981, 205, 407.
1
ppm. The H NMR spectrum in C6D6 showed five NBD
signals: the olefinic protons displayed two signals at
(22) Alvarez, P.; Gimeno, J .; Lastra, E.; Garcia-Granda, S.; Van der
Maelen, J . F.; Bassetti, M. Organometallics 2001, 20, 3762.
(23) Suzuki, H.; Kakigano, T.; Fukui, H.; Tanaka, M.; Moro-oka, Y.
J . Organomet. Chem. 1994, 473, 295.
(24) Sutter, J . P.; J ames, S. L.; Steenwinkel, P.; Karlen, T.; Grove,
D. M.; Veldman, N.; Smeets, W. J . J .; Spek, A. L.; van Koten, G.
Organometallics 1996, 15, 941.

4284 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
Sch em e 2
2.90 and 4.94 ppm, the bridgehead protons displayed
only one signal at 2.70 ppm, and the methylene protons
displayed two signals at 0.65 and 0.88 ppm. The 1H
NMR data of NBD are in agreement with the structure
in which the two methylene protons of NBD are non-
equivalent but the two bridgehead protons of NBD are
equivalent.
Reported compounds closely related to 2 are [RuX-
(NBD)(2,6-(Me2NCH2)2C6H3)] (X ) Cl, OTf; see struc-
ture A shown in Scheme 1 for their geometry), which
were reported recently by van Koten et al.24 Unlike
complex 2, the tridentate 2,6-(Me2NCH2)2C6H3 ligand
in A adopts a pseudofacial coordination mode and the
double bonds of NBD are trans to the nitrogen atoms
of the aryldiamine ligand.
To convert 2 to the hydride complex [RuH(NBD)-
(PCP)] (3), we have treated complex 2 with NaBH4. The
reaction in THF is very sluggish, and no reaction was
observed between 2 and NaBH4 at room temperature.
The expected hydride 3 along with some uncharacter-
ized phosphorus-containing species were produced when
a mixture of 2 and NaBH4 was refluxed in THF for 8 h.
Apparently, the chloride is bound to the ruthenium very
tightly so that the metathesis reaction could not occur
easily. In an alternative approach to prepare hydride
complex 3, we have treated complex 2 with TlO2CH,
hoping that complex 3 may be obtained via the formate
intermediate [Ru(O2CH)(NBD)(PCP)]. Formation of
[MHLn] by elimination of CO2 from formate complexes
[M(O2CH)Ln] are known reactions.25 As expected, reac-
tion of 2 with TlO2CH in THF produced the formate
complex [Ru(O2CH)(NBD)(PCP)] (4). The presence of the
formate ligand in complex 4 is indicated by the 1H NMR
spectrum, which showed the signal of O2CH at 7.97 ppm
(in C6D6). The formate complex 4 presumably has a
coordination sphere similar to that of 2, as judged on
the basis of the NMR data. The hydride complex 3 was
produced when the formate complex 4 was refluxed in
benzene for 16 h. However, the reaction is not clean and
small amounts of uncharacterized compounds were also
produced under the reaction conditions.
the 31P{1H} NMR spectrum in CD2Cl2 exhibited a
singlet at 76.9 ppm. Reported hydride complexes with
a NBD ligand related to 3 include [MClH(NBD)(PPh3)2]
(M ) Ru,26 Os27), [M(OTf)H(NBD)(PPh3)2] (M ) Ru,
Os),27 [Ru(Cp*)H(NBD)],12a and [OsH2(NBD)(P(i-Pr)3)2].13
P r oton a tion of [Ru H(NBD)(P CP )] w ith Acetic
Acid . Protonation of hydride complexes is one of the
most common pathways to prepare dihydrogen com-
plexes.1 It is also known that protonation of the olefin-
hydride complexes [MH(olefin)Ln] could give either
dihydrogen complexes or dihydride complexes, depend-
ing on the electron richness of the metal centers. For
example, protonation of [Ru(Cp*)H(COD)] produces [Ru-
(Cp*)(H2)(COD)]+;12a protonation of the more electron-
rich complex [OsH2(NBD)(P(i-Pr)3)2] produces the tri-
hydride complex [OsH3(NBD)(P(i-Pr)3)2]+.13 Since [RuH-
(H2)(dppe)2]+ contains a dihydrogen ligand14f and NBD
is less electron-donating than dppe, it is reasonable to
expect that protonation of 3 will generate the dihydro-
gen complex [Ru(H2)(NBD)(PCP)]+, which may undergo
hydrogen transfer reactions to give norbornene and the
metal fragment [Ru(PCP)]+. To obtain easily charac-
terizable metal complexes, the protonation was per-
formed with acetic acid in the presence of PPh3, in the
hope that the metal fragment [Ru(PCP)]+, if produced,
will combine with acetate and/or PPh3 to give well-
defined stable complexes. A control experiment shows
that 3 is unreactive toward PPh3. In the presence of
PPh3, complex 3 slowly reacted with excess CD3CO2D
to give [Ru(O2CCD3)(PPh3)(PCP)] (6d 3) and partially
deuterated norbornene (see Scheme 2). The norbornene
It was found that the hydride complex 3 could be
easily prepared from the reactions of NaBH4 with [Ru-
(OTf)(NBD)(PCP)] (5), which was in turn prepared by
1
treating 2 with TlOTf. Complex 5 has H and 31P{1H}
NMR data very similar to those of complex 2, indicating
that they have similar coordination spheres. The hy-
dride complex 3 has been characterized by NMR spec-
troscopy and elemental analysis. Its structure can be
1
readily assigned on the basis of the NMR data. The H
NMR spectrum in CD2Cl2 showed the hydride signal as
2
a triplet at -11.53 ppm with a J (PH) value of 22.5 Hz.
Thus, the hydride is cis to the two PPh2 groups. In the
31C{1H} NMR spectrum, the methylene carbons of PCP
exhibit a virtual triplet at 47.2 ppm, suggesting that
the PCP is meridionally coordinated to ruthenium.18c
The 13C NMR data of NBD of 3 indicate that the two
double bonds are nonequivalent but the two bridgehead
CH’s are equivalent. Thus, 3 must have a structure
similar to that of 2. In agreement with the structure,
2
1
generated can be readily identified by H and H NMR
2
spectra. The H NMR spectrum of the NBE generated
2
in the reaction shows a H signal at 0.97 ppm, indicating
that the deuterium is only incorporated at the endo
position of NBE.28 The results also indicate that the
(25) See for example: (a) Ogo, S.; Makihara, N.; Kaneko, Y.;
Watanabe, Y. Organometallics 2001, 20, 4903. (b) Lo, H. C.; Leiva, C.;
Buriez, O.; Kerr, J . B.; Olmstead, M. M.; Fish, R. H. Inorg. Chem. 2001,
40, 6705. (c) J ia, G.; Meek, D. W.; Gallucci, J . C. Inorg. Chem. 1991,
30, 403.
(26) Hallman, P. S.; McGarvey, B. R.; Wilkinson, G. J . Chem. Soc.
A 1968, 3143.
(27) Lo, S. T.; Xu, Z.; Wen, T. B.; Ng, W. S.; Liu, S. H.; Zhou, Z. Y.;
Lin, Z.; Lau, C. P.; J ia, G. Organometallics 2000, 19, 4523.

[RuH(NBD)(2,6-(Ph2PCH2)2C6H3)]
Organometallics, Vol. 21, No. 20, 2002 4285
Sch em e 3
F igu r e 2. Molecular structure of [Ru(OAc)(PPh3)(PCP)].
Hydrogen atoms of PPh3 and PCP are omitted for clarity.
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Ru (OAc)(P P h 3)(P CP )] (6)
Ru(1)-P(1)
Ru(1)-P(3)
Ru(1)-O(1)
O(1)-C(9)
2.3271(6)
2.2862(6)
2.1688(15)
1.268(3)
Ru(1)-P(2)
Ru(1)-C(1)
Ru(1)-O(2)
O(2)-C(9)
2.3154(6)
2.045(2)
2.3192(16)
1.259(3)
complexes such as 2 (150.4(1)°), [RuCl(PPh3)(PCP)]
(152.49(2)°),18b and [Ru(PCP)(PCHP)]OTf (153.64(3)°).15d
The solid-state structure of 6 is maintained in solution,
as suggested by the NMR data. In particular, the 1H
NMR spectrum in C6D6 showed virtual triplet signals
at 3.24 and 3.82 ppm for the methylene protons of the
PCP ligand and a singlet signal at 1.03 ppm for the CH3
group. The 31P{1H} NMR spectrum in C6D6 showed a
doublet at 46.8 ppm for PPh2 and a triplet at 53.4 ppm
for PPh3.
P(2)-Ru(1)-P(1) 159.70(2)
P(3)-Ru(1)-P(1)
C(1)-Ru(1)-P(1)
C(1)-Ru(1)-P(3)
O(2)-Ru(1)-P(1)
O(2)-Ru(1)-P(2)
96.76(2)
83.25(6)
89.22(6)
94.18(5)
95.49(4)
P(3)-Ru(1)-P(2)
C(1)-Ru(1)-P(2)
O(1)-Ru(1)-P(1)
O(1)-Ru(1)-P(2)
96.13(2)
81.30(6)
85.20(4)
84.79(4)
O(1)-Ru(1)-P(3) 170.11(5)
C(1)-Ru(1)-O(1) 100.64(7)
O(2)-Ru(1)-P(3) 111.88(4)
C(1)-Ru(1)-O(2) 158.89(7)
O(1)-C(9)-C(10) 119.5(2)
O(1)-Ru(1)-O(2)
58.24(6)
We have monitored the protonation reaction of 3 with
CD3CO2D by 31P{1H} and 1H NMR spectroscopy. The
experiments reveal that the Ru-H in 3 readily under-
goes H/D exchange with CD3CO2D to give [RuD(NBD)-
(PCP)] (3d 1) and that the H/D exchange reaction is
faster than the hydrogenation reaction. For example,
after a mixture of 3 and 5.7 equiv of CD3CO2D in CD2-
Cl2 was allowed to stand for 25 min, about 80% of
hydride 3 was converted to [RuD(NBD)(PCP)] and only
about 5% [Ru(O2CCD3)(PPh3)(PCP)] (6d 3) was produced
along with NBE at this stage. After 40 h, complex 3 is
completely converted to [Ru(O2CCD3)(PPh3)(PCP)] and
partially deuterated NBE (see Scheme 2). As suggested
O(2)-C(9)-C(10) 120.5(3)
O(2)-C(9)-O(1)
120.0(2)
87.54(14)
63.42(12)
C(9)-O(1)-Ru(1)
O(1)-C(9)-Ru(1)
94.19(13) C(9)-O(2)-Ru(1)
56.60(11) O(2)-C(9)-Ru(1)
deuterium is transferred to the NBD ligand from the
same side of the metal. The production of [Ru(O2CCD3)-
(PPh3)(PCP)] (6d 3) in the protonation has been con-
firmed by the 31P{1H} and H NMR spectra.
1
The acetate complex [Ru(O2CCH3)(PPh3)(PCP)] (6)
has been prepared alternatively from the reaction of 2
with AgO2CMe. The structure of 6 has been confirmed
by X-ray diffraction. The crystallographic details and
selected bond distances and angles are given in Tables
1 and 3, respectively. As shown in Figure 2, complex 6
has a distorted-octahedral structure with a bidentate
acetate ligand and a meridionally coordinated PCP
ligand. The acetate is unsymmetrically bound to ruthe-
nium with Ru-O distances of 2.1688(15) and 2.3192-
(16) Å. The O(1)-Ru(1)-O(2) angle (58.24(6)°) is close
to those in reported ruthenium complexes with a biden-
tate carboxylate ligand.29 The P(1)-Ru-P(2) bond angle
is 159.70(2)°, which is larger than those in Ru(PCP)
1
by the H NMR, the endo positions of the NBE gener-
ated in the protonation reaction have about 25% of
hydrogen and 75% of deuterium. It should be mentioned
that we have not been able to detect by NMR spectros-
copy any intermediates of the protonation reactions, as
the NMR spectra collected during the process only
showed the signals of complexes 3, 3d 1, 6d 3, and
norbornene.
As mentioned previously, protonation of 3 is expected
to give the dihydrogen complex [Ru(H2)(NBD)(PCP)]+.
The H/D exchange between 3 with CD3CO2D likely
involves the intermediate [Ru(HD)(NBD)(PCP)]+. As
shown in Scheme 3, reaction of 3 with CD3CO2D could
produce the η2-HD complex [Ru(η2-HD)(NBD)(PCP)]+
(28) Laszlo, P.; Schleyer, P. v. R. J . Am. Chem. Soc. 1964, 86, 1171.
(29) See for example: (a) Sanford, M. S.; Valdez, M. R.; Grubbs, R.
H. Organometallics 2001, 20, 5455. (b) Gonza`lez-Herrero, P.; Webern-
do¨rfer, B.; Ilg, K.; Wolf, J .; Werner, H. Organometallics 2001, 20, 3672.
(c) Kuznetsov, V. F.; Yap, G. P. A.; Alper, H. Organometallics 2001,
20, 1300.

4286 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
Sch em e 4
by monitoring the protonation reaction at 225 K by
NMR. However, the reaction is too fast, and only [Ru-
(OTf)(NBD)(PCP)] (4) was identified as the major
phosphorus-containing product under the reaction con-
ditions.
Rea ction of [Ru (OTf)(NBD)(P CP )] w ith H2. If
norbornane were formed from the dihydrogen interme-
diate [Ru(H2)(NBD)(PCP)]OTf, one would expect that
reaction of [Ru(OTf)(NBD)(PCP)] with H2 should also
produce norbornane. Indeed, such an expectation has
been confirmed experimentally. As indicated by 1H
NMR, norbornane was generated when a CD2Cl2 solu-
tion of [Ru(OTf)(NBD)(PCP)] was exposed to H2 for 20
min. We have also monitored the hydrogenation process
by NMR. Again, the 1H and 31P{1H} NMR spectra
collected during the process only show the signals of the
starting material [Ru(OTf)(NBD)(PCP)] and final prod-
ucts. In other words, under a H2 atmosphere, [Ru(OTf)-
(NBD)(PCP)] rather than [Ru(H2)(NBD)(PCP)]+ is the
NMR-observable species before hydrogenation. The
results suggest that the affinity of OTf- to [Ru(NBD)-
(PCP)]+ is higher than that of H2 and that hydrogen
transfer can occur readily to give hydrogenated product
once [Ru(H2)(NBD)(PCP)]+ is formed. The lower affinity
of H2 for the [Ru(NBD)(PCP)]+ fragment together with
the high reactivity of [Ru(H2)(NBD)(PCP)]+ prevents us
from detecting [Ru(H2)(NBD)(PCP)]+ by NMR experi-
ments.
(B), which can then be deprotonated by CD3CO2- to give
3d 1. Similar mechanisms have been proposed previ-
ously, for example, for the H/D exchange of [W(D2)(CO)3-
(P-Pr)3)2] with H2O30 and for the H/D exchange of
[Ru(Tp)(H2)(PPh3)2]+ with D2O.8
In the reaction of 3 with CD3CO2D, the NBE could
also be formed through the intermediate [Ru(η2-H2)-
(NBD)(PCP)]+ or its isotopomers. For example, NBE-
d2 could be formed from [Ru(η2-D2)(NBD)(PCP)]+ (C)
(Scheme 3). Such a proposition is consistent with the
fact that protonation of 3 with CD3CO2D gives deuter-
ated NBE in which the deuterium atoms are at the endo
positions of NBE. The fact that the NBD ligand of 3 can
only be hydrogenated slowly and that 3 and/or 3d 1 are
the only NMR-observable species before hydrogenation
even in the presence of excess acetic acid suggests that
the acidity of acetic acid is not strong enough to generate
the dihydrogen intermediate in a substantial amount.
P r oton a tion of 3 w ith HOTf. If the intermediate
[Ru(H2)(NBD)(PCP)]+ is involved in the hydrogenation
of the NBD ligand, one would expect that protonation
of 3 with a stronger acid should speed up the reaction.
To test this idea, we have studied the protonation
reaction of 3 with the strong acid HOTf in CD2Cl2. As
confirmed by NMR, 3 indeed reacted with HOTf rapidly
at room temperature to give [Ru(OTf)(NBD)(PCP)] (5)
and norbornane along with some uncharacterized phos-
phorus-containing species (Scheme 4). Formation of [Ru-
(OTf)(NBD)(PCP)] in the protonation reaction strongly
suggests that the dihydrogen complex [Ru(H2)(NBD)-
(PCP)]OTf was produced as the initial product in the
protonation reaction. One can easily see that displace-
ment of the H2 ligand in [Ru(H2)(NBD)(PCP)]OTf by
OTf- can lead to [Ru(OTf)(NBD)(PCP)]. Production of
norbornane in the protonation reaction can also be
related to the dihydrogen complex. The dihydrogen
intermediate [Ru(H2)(NBD)(PCP)]OTf may undergo hy-
drogen transfer from the H2 to the NBD ligand to give
[Ru(OTf)(NBE)(PCP)], which then reacts with a H2
molecule released from the formation of [Ru(OTf)(NBD)-
(PCP)] to give the fully hydrogenated product norbor-
nane and the unsaturated [Ru(PCP)]+ fragment. We
have attempted to detect the dihydrogen intermediate
It should be noted that we were unable to characterize
the metal-containing products in the reaction. After a
CD2Cl2 solution of [Ru(OTf)(NBD)(PCP)] was exposed
to H2 for 20 min, the 31P{1H} NMR spectrum showed
several new peaks likely associated with solvated [Ru-
(PCP)]+ species. Indeed, addition of CD3CN to the
reaction mixture produced [Ru(CD3CN)3(PCP)]+. How-
ever, if a CD2Cl2 solution of [Ru(OTf)(NBD)(PCP)] was
exposed to H2 for 18 h, all the starting material [Ru-
(OTf)(NBD)(PCP)] was consumed and only norbornane
1
could be identified. The 31P{1H} and H signals associ-
ated with the metal-containing products are featureless.
P r oton a tion of 3 w ith HOTf in th e P r esen ce of
CH3CN. In a further effort to verify that the dihydrogen
complex [Ru(H2)(NBD)(PCP)]OTf is the most likely
initial product in the protonation reaction of 3 with
HOTf, we have protonated [RuH(NBD)(PCP)] with
HOTf in the presence of acetonitrile. It is expected that
[Ru(MeCN)(NBD)(PCP)]OTf (7) would be produced if
[Ru(H2)(NBD)(PCP)]OTf were formed in the protonation
reaction. In dichloromethane in the presence of aceto-
nitrile, 3 reacted with HOTf, giving [Ru(MeCN)(NBD)-
(PCP)]OTf (7) and [Ru(MeCN)3(PCP)]+ (8) along with
NBE, as confirmed by NMR spectroscopy (Scheme 4).
The complex [Ru(MeCN)(NBD)(PCP)]OTf (7) has been
synthesized alternatively from the reaction of [Ru(OTf)-
(NBD)(PCP)] with acetonitrile. The structure of 7 has
been confirmed by an X-ray diffraction study. The
molecular structure of 7 is depicted in Figure 3. The
crystallographic details and selected bond distances and
angles are given in Tables 1 and 4, respectively. The
structure of 7 can be described as a distorted octahedron
with an CH3CN ligand trans to one of the double bonds
of NBD. The structural features associated with PCP
and NBD in complex 7 are very similar to those of
complex 2. The Ru-N(1) and N(1)-C(61) bond distances
(30) Kubas, G. J .; Burns, C. J .; Khalsa, G. R. K.; Van der Sluys, L.
S.; Kiss, G.; Hoff, C. D. Organometallics 1992, 11, 3390.

[RuH(NBD)(2,6-(Ph2PCH2)2C6H3)]
Organometallics, Vol. 21, No. 20, 2002 4287
formed by displacement of the H2 ligand in [Ru(H2)-
(NBD)(PCP)]OTf with MeCN. Apparently, some of the
[Ru(H2)(NBD)(PCP)]OTf also undergoes a hydrogen
transfer reaction in the presence of MeCN to give
norbornene and [Ru(MeCN)3(PCP)]+. In agreement with
the proposition, protonation of 3 with DOTf in the
presence of CD3CN produced partially deuterated NBE
in which the deuteriums are at the endo positions. It is
understandable that norbornene rather than norbor-
nane was formed in the protonation reaction, because
norbornene can be displaced by acetonitrile before it can
be hydrogenated further to norbornane.
Com m en ts on th e P r oton a tion Rea ction s. We
have studied the protonation reactions of [RuH(NBD)-
(PCP)] with acetic acid and HOTf. The products of the
protonation reactions are dependent on the acids used
and reaction conditions. For example, protonation of
[RuH(NBD)(PCP)] with acetic acid in the presence of
PPh3 gives norbornene and [Ru(OAc)(PPh3)(PCP)], pro-
tonation of [RuH(NBD)(PCP)] with HOTf gives norbor-
nane and [Ru(OTf)(NBD)(PPh3)(PCP)], and protonation
of [RuH(NBD)(PCP)] with HOTf in the presence of
MeCN gives norbornene, [Ru(MeCN)(NBD)(PCP)]OTf,
and [Ru(MeCN)3(PCP)]OTf. All the products can be
related to the reactive dihydrogen intermediate [Ru(H2)-
(NBD)(PCP)]+.
F igu r e 3. Molecular structure of [Ru(MeCN)(NBD)-
(PCP)]+. Hydrogen atoms are omitted for clarity.
It is noted that [Ru(OTf)(NBD)(PCP)] and [Ru(MeCN)-
(NBD)(PCP)]OTf were produced when [RuH(NBD)-
(PCP)] was protonated with HOTf in the absence or
presence of MeCN. However, [Ru(OAc)(NBD)(PCP)] was
not produced in the protonation of [RuH(NBD)(PCP)]
with acetic acid. The difference may be related to the
basicities of OAc- and OTf-. As mentioned previously,
when [RuH(NBD)(PCP)] was treated with CD3CO2D,
[RuH(NBD)(PCP)] undergoes an H/D exchange reaction
with CD3CO2D to give [RuD(NBD)(PCP)], and [RuX-
(NBD)(PCP)] (X ) H, D) are the only NMR-observable
species before hydrogenation. These observations sug-
gest that the acidity of acetic acid is not strong enough
to generate a substantial amount of [Ru(H2)(NBD)-
(PCP)]+ but acetate anion can function as a base to
deprotonate the dihydrogen complex [Ru(H2)(NBD)-
(PCP)]+, if generated, to give back the hydride complex
[RuH(NBD)(PCP)]. In other words, acetate will depro-
tonate [Ru(H2)(NBD)(PCP)]+ rather than displace the
H2 ligand. Thus, [Ru(OAc)(NBD)(PCP)] was not pro-
duced when 3 is treated with acetic acid. On the other
hand, HOTf is a strong acid that can protonate 3
completely to give the dihydrogen complex [Ru(H2)-
(NBD)(PCP)]+ and OTf- is a weak base that could not
deprotonate the dihydrogen complex. Once the dihydro-
gen complex [Ru(H2)(NBD)(PCP)]+ was formed, the
dihydrogen ligand could be readily displaced. Therefore,
[Ru(OTf)(NBD)(PCP)] and [Ru(MeCN)(NBD)(PCP)]OTf
were produced when 3 was treated with HOTf.
Ta ble 4. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for [Ru (MeCN)(NBD)(P CP )]OTf (7)
Ru(1)-P(1)
Ru(1)-C(1)
Ru(1)-C(51)
Ru(1)-C(54)
N(1)-C(61)
C(51)-C(52)
C(52)-C(53)
C(55)-C(56)
C(53)-C(57)
2.3642(11)
2.109(4)
2.323(4)
2.223(4)
1.133(5)
1.365(6)
1.533(6)
1.551(6)
1.555(6)
Ru(1)-P(2)
Ru(1)-N(1)
Ru(1)-C(52)
Ru(1)-C(55)
C(61)-C(62)
C(54)-C(55)
C(53)-C(54)
C(51)-C(56)
C(56)-C(57)
2.3721(11)
2.044(3)
2.311(4)
2.225(4)
1.451(6)
1.379(6)
1.535(6)
1.538(6)
1.539(6)
P(1)-Ru(1)-P(2)
C(1)-Ru(1)-P(1)
C(1)-Ru(1)-P(2)
153.63(4) N(1)-Ru(1)-C(1)
80.38(12) N(1)-Ru(1)-P(1)
77.47(11) N(1)-Ru(1)-P(2)
90.93(13)
81.44(9)
84.79(9)
C(1)-Ru(1)-C(51) 154.40(15) N(1)-Ru(1)-C(51) 104.26(14)
C(1)-Ru(1)-C(52) 160.32(16) N(1)-Ru(1)-C(52) 102.59(14)
C(1)-Ru(1)-C(54)
C(1)-Ru(1)-C(55)
C(61)-N(1)-Ru(1) 175.4(3)
99.36(15) N(1)-Ru(1)-C(54) 157.08(14)
96.83(15) N(1)-Ru(1)-C(55) 162.38(15)
N(1)-C(61)-C(62) 179.5(5)
and Ru(1)-N(1)-C(61) angle (175.4(3)°) are similar
to those in acetonitrile complexes such as [Ru(Cp)-
(CH3CN)2(PR3)]+ (R ) Cy, Me)31a and [Ru(2,9-dimethyl-
1,10-phenanthroline)2(CH3CN)2](PF6)2.31b The solid-
state structure is fully supported by the NMR data. The
structure of complex 8 is proposed on the basis of the
NMR data. In particular, the 31P{1H} NMR spectrum
displayed a singlet at 49.5 ppm. The 1H NMR spectrum
showed a virtual triplet for the methylene protons of
PCP at 3.98 ppm, indicating that the complex has a
symmetric structure with a meridionally bound PCP
ligand.
The experimental results described above strongly
suggest that the dihydrogen complex [Ru(H2)(NBD)-
(PCP)]+ is the active species in the hydrogenation of the
coordinated NBD ligand. Scheme 5 summarizes the
possible reaction pathways for the hydrogenation pro-
cess. The hydrogen transfer from the coordinated H2 to
the NBD ligand of [Ru(H2)(NBD)(PCP)]+ (D) could go
through a concerted mechanism (path B) or through a
stepwise one in which one of the hydrogens from the
Formation of [Ru(MeCN)(NBD)(PCP)]OTf is consis-
tent with the proposition that [Ru(H2)(NBD)(PCP)]OTf
was initially produced in the protonation reaction, as
[Ru(MeCN)(NBD)(PCP)]OTf can be thought of as being
(31) (a) Ru¨ba, E.; Simanko, W.; Mauthner, K.; Soldouzi, K. M.;
Slugovc, K.; Mereiter, K.; Schmid, K.; Kirchner, K. Organometallics
1999, 18, 3843. (b) Pezet, F.; Daran, J . C.; Sasaki, I.; Ait-Haddou, H.;
Balavoine, G. G. A. Organometallics 2000, 19, 4008.

4288 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
Sch em e 5
On the other hand, the calculations suggest that con-
version of 9 to 11 through a stepwise process is feasible.
Figure 4 shows the reaction steps for the conversion of
9 to 11 through 10 (the model complex of E proposed in
Scheme 5), together with the relative free energies and
reaction energies (in parentheses) calculated for all the
species. It is clear that the relative free energies do not
differ too much from the relative reaction energies. Our
calculations are based on the gas-phase model. The
calculated results are used to simulate the reactions in
solution. Therefore, relative free energies that consider
the entropy effect and thermal/zero-point energy cor-
rections will be used in the following discussion.
As shown in Figure 4, the stepwise mechanism
involves two steps: one hydrogen atom from the coor-
dinated H2 is transferred to NBD to form intermediate
10 through transition state TS1 with a barrier of 19.08
kcal/mol, and then the second hydrogen transfer com-
pletes the hydrogenation of one of the two double bonds
of NBD to form the NBE complex 11. The barrier of the
second hydrogen transfer is only 6.77 kcal/mol. The first
hydrogen transfer is therefore the rate-determining step
in the reaction. After the rate-determining barrier is
surmounted, the reaction proceeds easily by having the
second hydrogen transfer. The conversion from 9 to 11
is exothermic and irreversible. In view of the large
energy difference between 9 and 11 and the small
barriers connecting them, it is not too surprising that
the dihydrogen complex [Ru(H2)(NBD)(PCP)]+ was not
detected in the experiments.
Figure 5 shows the optimized structures with selected
structural parameters for all the related species. Com-
plex 9 is a typical octahedral dihydrogen complex with
a short H-H distance of 0.868 Å. The first transition
state (TS1) corresponds to a dihydride species in which
one of the hydrides is 1.645 Å from the receiving carbon
of NBD. The intermediate 10 can be described as a
pentagonal bipyramid (PB) in which one hydride and
one olefin ligand form the axle of the PB structure and
the PCP and agostic ligand lie on the equatorial plane.
The intermediate is formally seven-coordinated with a
Ru(IV) center. An osmium analogue, the formally seven-
coordinated Os(IV) complex [OsH2(η3-C6H9)(P(i-Pr)3)2]+
with an agostic interaction, has recently been reported
by Esteruelas et al.13 Interestingly, when the second
hydrogen is transferred to form 11, the PCP ligand
changes from a meridional arrangement to a facial
arrangement. The P-Ru-P angles in 9 and 10 are 157.3
and 149.8°, respectively. However, the P-Ru-P angles
become 100.7 and 101.7° in TS2 and 11, respectively.
The facial arrangement of a PCP ligand is not unusual,
as some Os complexes with a facially coordinated PCP
ligand have been characterized by X-ray diffraction in
our laboratory.32 In addition, the aryldiamine ligand 2,6-
(Me2NCH2)2C6H3, which is analogous to PCP, adopts a
pseudofacial arrangement in the complexes [RuX(NBD)-
(2,6-(Me2NCH2)2C6H3)] (X ) Cl, OTf; see structure A
in Scheme 1 for their geometry).24 The facial arrange-
ment of the PCP ligand in TS2 and 11 can be related
to the special structural features of the agostic NBE
ligand.
coordinated H2 is transferred to the NBD to give the
hydrido alkyl complex [RuH(C7H9)(PCP)]+ (E) followed
by reductive elimination (path A). Scheme 5 does not
consider the involvement of the PPh3/CH3CN coordina-
tion. This is justified, because additional ligands are not
necessary for the hydrogenation to occur. As supporting
evidence, the NBD ligand of RuH(NBD)(PCP) is hydro-
genated when treated with HOTf without addition of
other ligands.
Com p u ta tion a l Stu d y. Scheme 5 gives two possible
reaction pathways for the hydrogenation process. The
detailed pathways for the hydrogen transfer process,
however, could not be determined experimentally. To
examine the feasibility of the two proposed reaction
pathways, the structural and energetic aspects of the
possible reaction pathways for the conversion of the
complex [Ru(H2)(NBD)(2,6-(H2PCH2)2C6H3)]+ (9) to the
assumed product [Ru(NBE)(2,6-(H2PCH2)2C6H3)]+ (11)
have been studied by density functional calculations at
the B3LYP level of theory. Here, 9 and 11 are the model
complexes of D and F proposed in Scheme 5, respec-
tively. We also hope to clarify whether the hydrogena-
tion goes through a stepwise or concerted mechanism.
When the one-step concerted pathway was considered,
attempts to locate the transition state were not suc-
cessful. We have explored the potential energy surface
in the vicinity of the possible concerted transition
structure. In doing so, we obtained a series of partially
optimized structures having various predefined H‚‚‚C
distances. Here, H denotes the transferring hydrogens
and C denotes the hydrogen-receiving carbons of the
coordinated NBD ligand. Among these partially opti-
mized structures, the highest energy structure along the
concerted reaction coordinate has the two H‚‚‚C dis-
tances at 1.585 Å and is 70 kcal/mol above the dihydro-
gen complex 9. Frequency calculations based on this
structure give three imaginary frequencies (-1060.6,
-704.3, and -9.4 cm-1). The two larger imaginary
frequencies correspond to the asymmetric and sym-
metric motions of the two transferring hydrogens along
the direction of the concerted reaction coordinate. In
view of the high-energy area in the vicinity of the
possible transition structure for the concerted pathway
and the frequency calculations discussed above, we can
conclude that a transition state corresponding to the
one-step hydrogenation does not exist. Thus, conversion
of 9 to 11 through a concerted process is unlikely.
Su m m a r y a n d Con clu d in g Rem a r k s. We have
prepared the hydride complex [RuH(NBD)(PCP)] and
(32) Wen, T. B.; Zhou, Z. Y.; J ia, G. Unpublished results.

[RuH(NBD)(2,6-(Ph2PCH2)2C6H3)]
Organometallics, Vol. 21, No. 20, 2002 4289
F igu r e 4. Schematic illustration of the reaction pathways with calculated relative free energies (kcal/mol) and reaction
energies (kcal/mol, in parentheses) for species involved in the reaction.
F igu r e 5. Optimized structures with selected bond distances (Å) and angles (deg) together with relative stabilities.
studied its protonation reactions. When [RuH(NBD)-
(PCP)] is protonated, the NBD ligand is hydrogenated.
Both theoretical and experimental results support the
proposal that [Ru(H2)(NBD)(PCP)]+ was the initial
protonation product and was involved in the hydrogena-
tion of NBD in the protonation reaction. These results
include the following: (i) [RuH(NBD)(PCP)] can undergo
H/D exchange with CD3CO2D to give [RuD(NBD)(PCP)],

4290 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
under vacuum. Yield: 0.21 g, 82%. Anal. Calcd for C40H36O2P2-
Ru: C, 67.50; H, 5.10. Found: C, 67.54; H, 5.26. 1H NMR
(300.13 MHz, C6D6): δ 0.56 (d, J (HH) ) 8.2 Hz, 1H, CHH),
0.91 (d, J (HH) ) 8.2 Hz, 1H, CHH), 2.67 (s, 2H, CH), 2.74 (s,
2H, dCH), 4.16 (m, 2H, CH2P), 4.27 (m, 2H, CH2P), 5.97 (s,
2H, dCH), 7.11-7.76 (m, 20H, PPh2), 7.97 (s, 1H, O2CH). 31P-
{1H} NMR (121.49 MHz, C6D6): δ 59.4 (s).
[Ru (OTf)(NBD)(P CP )] (5). A mixture of 2 (1.0 g, 1.4 mmol)
and TlOTf (1.0 g, 2.8 mmol) in CH2Cl2 (60 mL) was stirred for
1.5 h. The insoluble TlCl was removed by filtration. The
volume of the filtrate was reduced to ca. 3 mL under vacuum.
Addition of hexane (30 mL) to the residue produced a brownish
yellow solid, which was collected by filtration, washed with
hexane, and dried under vacuum overnight. Yield: 1.0 g, 86%.
1H NMR (300.13 MHz, CD2Cl2): δ 0.75 (br s, 1H, CH2), 0.96
(br s, 1H, CH2), 2.64 (s, 2H, CH), 2.73 (s, 2H, dCH), 4.26 (br,
2H, CH2P), 4.45 (br, 2H, CH2P), 5.50 (s, 2H, dCH), 7.27-8.12
(m, 20H, PPh2). 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 55.2
(br s).
[Ru H(NBD)(P CP )] (3). Meth od A. A mixture of 5 (0.70
g, 0.86 mmol) and NaBH4 (0.30 g, 7.9 mmol) in THF (60 mL)
was stirred at room temperature for 1 h. The mixture was
filtered through Celite. The solvent of the filtrate was removed
completely. Addition of MeOH (60 mL) to the residue produced
a brownish yellow solid, which was collected by filtration,
washed with MeOH (3 × 10 mL), and dried under vacuum
overnight to give pure 3. Yield: 0.45 g, 79%.
Meth od B. A mixture of 2 (0.20 g, 0.28 mmol) and NaBH4
(0.10 g, 2.63 mmol) in THF (30 mL) was refluxed for 8 h. The
solvent was then removed completely, and the residue was
extracted with benzene (20 mL). The volume of the extract
was reduced to 3 mL. Addition of hexane (20 mL) to the residue
produced a brownish yellow solid, which was collected by
filtration, washed with hexane and MeOH, and dried under
vacuum overnight to give 0.095 g of crude product. The NMR
spectra show that the crude product contains mainly complex
3 along with other unidentified phosphorus-containing species.
Meth od C. A solution of 4 (0.02 g, 0.028 mmol) in C6D6 in
an NMR tube was heated for 16 h. Then NMR spectra were
collected. The NMR spectra show that 3 was produced along
with some minor phosphorus-containing species. Charateriza-
tion data for 3 are as follows. Anal. Calcd for C39H36P2Ru: C,
70.15; H, 5.43. Found: C, 70.15; H, 5.59. 1H NMR (300.13
MHz, CD2Cl2): δ -11.53 (t, J (PH) ) 22.5 Hz, 1H, RuH), 0.56
(s, 2H, CH2), 2.23 (s, 2H, CH), 3.16 (s, 2H, dCH), 3.44 (s, 2H,
dCH), 3.73 (br d, J (HH) ) 15.9 Hz, 2H, CH2P), 4.47 (br d,
J (HH) ) 15.9 Hz, 2H, CH2P), 7.26-7.80 (m, 20H, PPh2). 31P-
{1H} NMR (121.49 MHz, CD2Cl2): δ 76.9 (s). 13C{1H} NMR
(75.5 MHz, CD2Cl2): δ 47.2 (t, J (PC) ) 16.2 Hz, CH2P), 48.2
(s, bridgehead CH), 54.0 (s, dCH), 58.5 (s, dCH), 60.3 (s, CH2),
127-134 (m, Ph).
[Ru (O2CMe)(P P h 3)(P CP )] (6). A mixture of 2 (0.16 g, 0.18
mmol) and TlOAc (0.20 g, 0.76 mmol) in CH2Cl2 (35 mL) was
stirred for 1 h. The TlCl was removed by filtration. The volume
of the filtrate was reduced to ca. 3 mL under vacuum. Addition
of hexane (30 mL) to the residue produced a yellow solid, which
was collected by filtration, washed with hexane, and dried
under vacuum. Yield: 0.14 g, 88%. Anal. Calcd for C52H45O2P3-
Ru: C, 69.71; H, 5.06; Found: C, 69.90; H, 5.13. 1H NMR
(300.13 MHz, C6D6): δ 1.03 (s, 3H, CH3), 3.24 (dt, J (HH) )
16.8 Hz, J (PH) ) 4.3 Hz, 2H, CH2P), 3.82 (dt, J (HH) ) 16.8
Hz, J (PH) ) 5.6 Hz, 2H, CH2P), 6.81-7.41 (m, 35H, PPh2,
PPh3). 31P{1H} NMR (121.49 MHz, C6D6): δ 46.8 (d, J (PP) )
30.0 Hz), 53.4 (t, J (PP) ) 30.0 Hz).
(ii) protonation of [RuH(NBD)(PCP)] in the presence of
MeCN produced [Ru(MeCN)(NBD)(PCP)]+, (iii) proto-
nation of [RuH(NBD)(PCP)] with deuterated acids
produced partially deuterated norbornene in which the
deuterium is only incorporated at the endo position, (iv)
hydrogenated product was obtained when [Ru(OTf)-
(NBD)(PCP)] was treated with H2, and (v) the compu-
tational study confirms that [Ru(H2)(NBD)(PCP)]+ is a
reasonable species. The computational study also sug-
gests that hydrogen transfer from the dihydrogen to the
NBD ligand of [Ru(H2)(NBD)(PCP)]+ most likely pro-
ceeds by first transferring one of the hydrogens from
the coordinated H2 to the NBD to give the hydrido alkyl
complex [RuH(C7H9)(PCP)]+, which is then followed by
reductive elimination.
We have previously shown that protonation of [Ru-
(Cp*)H(NBD)] produces nortricyclene through the di-
hydrogen intermediate [Ru(Cp*)(H2)(NBD)]+, where H2
is cis to both of the double bonds of NBD.12a In this
regard, it is interesting to note that norbornene is
produced when [RuH(NBD)(PCP)] is protonated. The
latter reaction may involve the dihydrogen complex [Ru-
(H2)(NBD)(PCP)]+, where H2 is only cis to one of the
double bonds of NBD. It has also been suggested that
norbornene and nortricyclene can be formed from mer-
and fac-[M(H2)(η4-NBD)(CO)3] (M ) Cr, Mo, W), respec-
tively.10 These results suggest that the relative positions
of the NBD olefinic functions to that of the H2 ligand
are important in determining the structures of the
hydrogenation products (norbornene and nortricylene).
Exp er im en ta l Section
All manipulations were carried out at room temperature
under a nitrogen atmosphere using standard Schlenk tech-
niques, unless otherwise stated. Solvents were distilled under
nitrogen from sodium-benzophenone (hexane, diethyl ether,
THF, benzene) or calcium hydride (dichloromethane, CHCl3).
The starting material [RuCl(PPh3)(PCP)] was prepared ac-
cording to a literature method.18b Microanalyses were per-
formed by M-H-W Laboratories (Phoenix, AZ). 1H, 13C{1H}, and
31P{1H} NMR spectra were collected on a Bruker ARX-300
spectrometer (300 MHz). 1H and 13C NMR chemical shifts are
relative to TMS, and 31P NMR chemical shifts are relative to
85% H3PO4.
[Ru Cl(NBD)(P CP )] (2). A mixture of [RuCl(PPh3)(PCP)]
(1.70 g, 1.95 mmol), NBD (1.0 mL, 9.8 mmol), and CuCl (1.0
g, 10 mmol) in CH2Cl2 (90 mL) was stirred for 6 h. The
insoluble material was then removed by filtration through
Celite, and the volume of the filtrate was reduced to ca. 3 mL.
Addition of hexane (60 mL) to the residue caused precipitation
of a greenish yellow solid. The solid was collected by filtration,
washed with hexane (2 × 10 mL), and dried under vacuum
overnight. Yield: 1.1 g, 80%. Anal. Calcd for C39H35ClP2Ru:
1
C, 66.71; H, 5.02. Found: C, 66.70; H, 4.94. H NMR (300.13
MHz, C6D6): δ 0.65 (d, J (HH) ) 8.0 Hz, 1H, CHH), 0.88 (d,
J (HH) ) 8.0 Hz, 1H, CHH), 2.70 (s, 2H, CH), 2.90 (s, 2H, d
CH), 4.20 (m, 2H, CH2P), 4.32 (m, 2H, CH2P), 4.94 (s, 2H, d
CH), 7.22 (br m, 12H, PPh2), 8.02 (br m, 8H, PPh2). 31P{1H}
NMR (121.49 MHz, C6D6): δ 55.4 (s).
[Ru (O2CH)(NBD)(P CP )] (4). A mixture of 2 (0.25 g, 0.36
mmol) and TlO2CH (0.25 g, 1.0 mmol) in THF (30 mL) was
stirred for 4 h. The THF was then removed under vacuum. To
the residue was added benzene (30 mL). The mixture was
stirred for 15 min and then filtered through Celite. The volume
of the filtrate was reduced to ca. 3 mL under vacuum. Addition
of hexane (60 mL) to the residue produced a yellow solid, which
was collected by filtration, washed with hexane, and dried
[Ru (CH3CN)(NBD)(P CP )]OTf (7). A mixture of 5 (0.70
g, 0.86 mmol) and CH3CN (1 mL) in CH2Cl2 (35 mL) was
stirred for 2 h. The volume of the reaction mixture was reduced
to ca. 3 mL. Addition of hexane (60 mL) to the residue caused
precipitation of a yellow solid. The solid was collected by
filtration, washed with hexane (2 × 10 mL), and dried under
vacuum overnight. Yield: 0.60 g, 81%. Anal. Calcd for C42H38F3-

[RuH(NBD)(2,6-(Ph2PCH2)2C6H3)]
Organometallics, Vol. 21, No. 20, 2002 4291
NO3P2SRu: C, 58.88; H, 4.47; N, 1.64. Found: C, 58.66; H,
4.63; N, 1.65. 1H NMR (300.13 MHz, CD2Cl2): δ 0.69 (d, J (HH)
) 8.9 Hz, 1H, CHH), 0.90 (d, J (HH) ) 8.9 Hz, 1H, CHH), 1.35
(s, 3H, CH3), 2.52 (s, 2H, CH), 2.99 (s, 2H, dCH), 4.06 (m, 2H,
CH2P), 4.46 (m, 2H, CH2P), 5.19 (s, 2H, dCH), 7.35-8.02 (m,
20H, PPh2). 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 54.4 (s).
P r oton a tion of [Ru H(NBD)(P CP )] w ith CD3CO2D in
th e P r esen ce of P P h 3 in CD2Cl2 a n d Id en tifica tion of
species were produced. The 1H NMR spectra of the reaction
1
mixtures showed signals of norbornane. The H NMR signals
of norbornane appearing in the 1H NMR spectrum are as
1
follows. H NMR (300.13 MHz, CD2Cl2): δ 1.28 (m, 6H, CH2),
1.57 (m, 4H, CH2), 2.29 (br, 2H, bridgehead CH).
P r oton a tion of [Ru H(NBD)(P CP )] w ith HOTf in th e
P r esen ce of CD3CN in CD2Cl2 a n d Id en tifica tion of NBE
1
by H NMR. In an NMR tube charged with [RuH(NBD)(PCP)]
1
NBE by H NMR. In an NMR tube charged with [RuH(NBD)-
(20 mg, 0.030 mmol), CD3CN (0.05 mL), and CD2Cl2 (0.5 mL)
was added DOTf (5 µL, 0.06 mmol) through a microsyringe.
The mixture was allowed to stand for 30 min, and then NMR
spectra were collected. The NMR spectra show that [Ru(CD3-
CN)(NBD)(PCP)]OTf (7d 3), [Ru(CD3CN)3(PCP)]OTf (8d 3), and
NBE are formed in a ratio of 3:2:2. NMR signals of 7d 3 are as
follows. 31P{1H} NMR (121.49 MHz, CD2Cl2): δ 54.5 (s). 1H
NMR (300.13 MHz, CD2Cl2): δ 0.76 (d, J (HH) ) 8.9 Hz, 1H,
CHH), 0.96 (d, J (HH) ) 8.9 Hz, 1H, CHH), 2.63 (s, 2H, CH),
3.09 (s, 2H, dCH), 4.14 (m, 2H, CH2P), 4.55 (m, 2H, CH2P),
5.23 (s, 2H, dCH), 7.03-8.01 (m, Ph, mixed with those of 8d 3).
NMR signals of 8d 3 are as follows. 31P{1H} NMR (121.49 MHz,
CD2Cl2): δ 49.5 (s). 1H NMR (300.13 MHz, CD2Cl2): δ 3.94 (t,
4H, J (PH) ) 3.9 Hz, CH2P), 7.03-8.01 (m, Ph, mixed with
those of 7d 3). NMR signals of NBE are as follows. 1H NMR
(300.13 MHz, CD2Cl2): δ 1.00 (br, 2H, endo-CH2), 1.15 (br, 1H,
CH2), 1.35 (br, 1H, CH2), 1.69 (br, 2H, exo-CH2), 2.93 (s, 2H,
bridgehead CH), 6.03 (s, 2H, dCH).
P r oton a tion of [Ru H(NBD)(P CP )] w ith HOTf in th e
P r esen ce of CH3CN in CH2Cl2 a n d Id en tifica tion of
com p lexes 7 a n d 8 by NMR. In an NMR tube charged with
[RuH(NBD)(PCP)] (20 mg, 0.030 mmol), CH3CN (0.05 mL), and
CH2Cl2 (0.5 mL) was added HOTf (5 µL, 0.06 mmol) through
a microsyringe. The mixture was allowed to stand for 30 min.
The volatile materials were removed under vacuum. To the
residue was added CD2Cl2 (0.5 mL), and then NMR spectra
were collected. The NMR spectra show that [Ru(CH3CN)(PCP)-
(NBD)]OTf (7) and [Ru(CH3CN)3(PCP)]OTf (8) are present in
a ratio of 3/2. NMR signals of 7 are as follows. 31P{1H} NMR
(121.49 MHz, CD2Cl2): δ 54.5 (s). 1H NMR (300.13 MHz, CD2-
Cl2): δ 0.78 (d, J (HH) ) 8.9 Hz, 1H, CHH), 0.99 (d, J (HH) )
8.9 Hz, 1H, CHH), 1.42 (s, 3H, CH3CN, mixed with those of
8), 2.64 (s, 2H, CH), 3.11 (s, 2H, dCH), 4.16 (m, 2H, CH2P),
4.57 (m, 2H, CH2P), 5.25 (s, 2H, dCH), 7.20-8.02 (m, Ph,
mixed with those of 8). NMR signals of 8 are as follows. 31P-
{1H} NMR (121.49 MHz, CD2Cl2): δ 49.5 (s, [Ru(CH3CN)3-
(PCP)]OTf). 1H NMR (300.13 MHz, CD2Cl2): δ 1.42 (s, 9H,
CH3CN, mixed with those of 7), 3.98 (t, 4H, J (PH) ) 3.9 Hz,
CH2P), 7.20-8.02 (m, Ph, mixed with those of 7).
P r oton a tion of [Ru H(NBD)(P CP )] w ith DOTf in th e
P r esen ce of CH3CN in CH2Cl2 a n d Id en tifica tion of
Deu t er a t ed NBE by 2H NMR . To an NMR tube charged
with [RuH(NBD)(PCP)] (20 mg, 0.030 mmol), CH3CN (0.05
mL), and CH2Cl2 (0.7 mL) was added DOTf (5 µL, 0.06 mmol)
through a microsyringe. The mixture was allowed to stand for
1 h. After the solution was treated with NaOH, the volatile
portion was separated by vacuum transfer. The 2H NMR (61.25
MHz, CH2Cl2) of the resulting solution showed a singlet at 0.95
ppm.
Cr ysta llogr a p h ic An a lysis. Crystals suitable for X-ray
diffraction were grown from CH2Cl2 solutions of [RuCl(NBD)-
(PCP)] (2), [Ru(OAc)(PPh3)(PCP)] (6), and [Ru(MeCN)(NBD)-
(PCP)]OTf (7) layered with hexane. All of the intensity data
were collected on a Bruker SMART CCD area detector with
graphite-monochromated Mo KR radiation at room tempera-
ture and corrected for absorption by SADABS (Siemens Area
Detector Absorption).33 All structures were solved by direct
methods, expanded by difference Fourier syntheses, and
refined by full-matrix least squares on F2 using the Bruker
SHELXTL (version 5.10)34 program package. All non-hydrogen
(PCP)] (20 mg, 0.030 mmol), PPh3 (20 mg, 0.076 mmol), and
CD2Cl2 (0.7 mL) was added CD3CO2D (10 µL, 0.17 mmol)
through a microsyringe. The mixture was allowed to stand for
1
40 h. H and 31P{1H} NMR spectra were then collected. The
NMR spectra showed that [Ru(O2CCD3)(PPh3)(PCP)] and
partially deuterated norbornene were present. NMR signals
of [Ru(O2CCD3)(PPh3)(PCP)] are as follows. 31P{1H} NMR
(121.49 MHz, CD2Cl2): δ 44.8 (d, J (PP) ) 30.5 Hz, PCP of [Ru-
(O2CCD3)(PPh3)(PCP)]), 53.2 (t, J (PP) ) 30.5 Hz, PPh3 of
[Ru(O2CCD3)(PPh3)(PCP)]). 1H NMR (300.13 MHz, CD2Cl2): δ
3.25 (dt, J (HH) ) 16.8 Hz, J (PH) ) 4.3 Hz, 2H, CH2P), 3.81
(dt, J (HH) ) 16.8 Hz, J (PH) ) 5.6 Hz, 2H, CH2P), 7.24-8.12
(m, Ph). NMR signals of NBE are as follows. 1H NMR (300.13
MHz, CD2Cl2): δ 0.95 (s, 0.5 H, residual endo-H, most of the
H at this position has been replaced with deuterium), 1.20 (d,
J (HH) ) 8.1 Hz, 1H, CH2), 1.41 (d, J (HH) ) 8.1 Hz, 1H, CH2),
1.71 (s, 2H, exo-H), 2.93 (s, 2H, CH), 6.10 (s, 2H, dCH). The
volatile portion of the reaction mixture can be separated by
vacuum transfer. The 1H NMR spectrum of the vacuum-
transferred solution indicates that norbornene is the only
volatile organic product formed in the reaction and that the
endo positions of NBE obtained under the reaction conditions
have about 25% of H and 75% of D.
P r oton a tion of [Ru H(NBD)(P CP )] w ith CD3CO2D in
th e P r esen ce of P P h 3 in CH2Cl2 a n d Id en tifica tion of
2
Deu ter a ted NBE by H NMR. In an NMR tube charged with
[RuH(NBD)(PCP)] (20 mg, 0.030 mmol), PPh3 (20 mg, 0.076
mmol), and CH2Cl2 (0.7 mL) was added CD3CO2D (10 µL, 0.17
mmol) through a microsyringe. The mixture was allowed to
stand for 40 h. After the solution was treated with NaOH, the
volatile portion of the reaction mixture was separated by
vacuum transfer. The 2H NMR spectrum (61.25 MHz, CH2-
Cl2) of the resulting solution showed a singlet at 0.97 ppm.
P r oton ation of [Ru H(NBD)(P CP )] with HOTf in CD2Cl2
1
a n d Id en tifica tion of Nor bor n a n e by H NMR. In an NMR
tube charged with [RuH(NBD)(PCP)] (20 mg, 0.030 mmol) and
CD2Cl2 (0.5 mL) was added HOTf (5 µL, 0.06 mmol) through
a microsyringe. The mixture was allowed to stand for 10 min,
and then NMR spectra were collected. The 31P{1H} NMR
spectrum (CD2Cl2, 121.49 MHz) showed a broad signal at 55.8
ppm assignable to [Ru(OTf)(NBD)(PCP)] and several other
signals of unidentified species in the region 35-84 ppm. The
1H NMR spectrum (CD2Cl2, 300.13 MHz) showed signals of
[Ru(OTf)(NBD)(PCP)] and norbornane. The 1H integrations
suggest that [Ru(OTf)(NBD)(PCP)] and norbornane are present
in a ratio of ca. 1:0.9. Selected 1H NMR signals of [Ru(OTf)-
(NBD)(PCP)]: δ 2.54 (br, bridgehead CH of NBD), 2.63 (br,
dCH of NBD), 4.09 (br, CH2 of PCP), 4.25 (br, CH2 of PCP).
1H NMR signals of norbornane: δ 1.19 (m, 6H, CH2), 1.47 (m,
4H, CH2), 2.19 (br, 2H, bridgehead CH).
Hyd r ogen a tion of [Ru (OTf)(NBD)(P CP )]. A CD2Cl2
solution (0.5 mL) of [Ru(OTf)(NBD)(PCP)] was generated in
situ in an NMR tube by mixing [RuCl(NBD)(PCP)] (20 mg,
0.028 mmol) and AgOTf (10 mg, 0.039 mmol) for 30 min. The
mixture was then stored under 1 atm of H2 for 20 min, and
NMR spectra were collected. The NMR spectra showed that
[Ru(OTf)(NBD)(PCP)] and norbornane were present in a ratio
of ca. 1.1:1 along with several other uncharacterized phospho-
rus-containing species. NMR spectra were collected again after
the mixture was stored under H2 for 18 h. The 31P NMR
spectrum shows that [Ru(OTf)(NBD)(PCP)] was no longer
present and a complicated mixture of phosphorus-containing
(33) Sheldrick, G. M. SADABS, Empiracal Absorption Correction
Program; University of Go¨ttingen, Go¨ttingen, Germany, 1996.

4292 Organometallics, Vol. 21, No. 20, 2002
Liu et al.
atoms were refined anisotropically. Hydrogen atoms were
placed in ideal positions and refined as riding atoms, except
those for the acetonitrile ligand in 7, which were located from
the difference Fourier map and constrained to ride on the
respective carbon (C62). In the case of 7, after initial full-
matrix least-squares refinement, the OTf anion exhibited
distorted CF3 and SO3 groups, due to the large thermal motion
of the terminal O and F atoms, and was subjected to fixed C-F
and S-O distance restraints in the further refinement.
Further crystallographic details are summarized in Table 1.
Com p u ta tion a l Deta ils. In the calculations, the phenyl
groups of the PCP ligand have been modeled using hydrogen
atoms. Geometry optimizations and frequency calculations
have been performed for all species (reactants, intermediates,
transition states, and products) involved in the reaction. All
calculations have been carried out at the B3LYP level of
density functional theory.35 The LANL2DZ effective core
potentials and basis sets36 were used to describe the Ru and
P atoms, while the standard 6-31G basis set37 was used for C
and H atoms. Polarization functions were added for hydrogen
(ê(p) ) 1.1)38 involved in the transfer processes. Transition
states are confirmed by frequency calculations with the same
density functional theory, effective core potentials, and basis
sets. All calculations were performed using the Gaussian 98
program39 installed on Pentium III/IV personal computers with
Linux (Red Hat) operating systems.
Ack n ow led gm en t. We acknowledge financial sup-
port from the Hong Kong Research Grants Council.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic details, bond distances and angles, atomic coordi-
nates and equivalent isotropic displacement coefficients, and
anisotropic displacement coefficients for [RuCl(NBD)(PCP)] (2),
[Ru(OAc)(PPh3)(PCP)] (6), and [Ru(MeCN)(NBD)(PCP)]OTf
(7); data are also available as files in CIF format. This ma-
terial is available free of charge via the Internet at http://
pubs.acs.org.
OM020521Q
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