Synthesis and reactions of diphosphinidenecyclobutene ruthenium complexes relevant to catalytic hydrosilylation of terminal alkynes

Article abstract of DOI:10.1021/om800119f

The complex [RuCl(μ-Cl)(CO)(DPCB-OMe)]₂ (1a), bearing a low-coordinated phosphorus ligand (DPCB-OMe = 1,2-bis(4-methoxyphenyl)-3,4- bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene), is readily reduced to [RuH(μ-Cl)(CO)(DPCB-OMe)]₂ (2a) by the reaction with water and HSiMe₂Ph. The reaction proceeds via a [RuCl₂(CO)(H ₂O)(DPCB-OMe)] intermediate, which is characterized by X-ray diffraction analysis. Complexes 1a and 2a serve as highly efficient catalysts for Z-selective hydrosilylation of phenylacetylene. The reason for the high catalyst efficiency of DPCB-OMe complexes has been investigated by reaction and structure analysis of the presumed intermediate [Ru(CH=CHPh)Cl(CO)(DPCB-OMe)] (3a). It has been found that 3a has ample space to associate with hydrosilane and, therefore, readily undergoes metathesis between Ru-C and H-Si bonds. This structural feature in conjunction with the strong π-accepting ability of the DPCB-OMe ligand leads to highly efficient catalysis for Z-selective hydrosilylation of terminal alkynes.

Full text of DOI:10.1021/om800119f

Organometallics 2008, 27, 2321–2327
2321
Synthesis and Reactions of Diphosphinidenecyclobutene Ruthenium
Complexes Relevant to Catalytic Hydrosilylation of Terminal
Alkynes
Akito Hayashi, Takahiko Yoshitomi, Kazutoshi Umeda, Masaaki Okazaki, and
Fumiyuki Ozawa*
International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto
UniVersity, Uji, Kyoto 611-0011, Japan
ReceiVed February 9, 2008
The complex [RuCl(µ-Cl)(CO)(DPCB-OMe)]2 (1a), bearing a low-coordinated phosphorus ligand
(DPCB-OMe ) 1,2-bis(4-methoxyphenyl)-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene),
is readily reduced to [RuH(µ-Cl)(CO)(DPCB-OMe)]2 (2a) by the reaction with water and HSiMe2Ph.
The reaction proceeds via a [RuCl2(CO)(H2O)(DPCB-OMe)] intermediate, which is characterized by
X-ray diffraction analysis. Complexes 1a and 2a serve as highly efficient catalysts for Z-selective
hydrosilylation of phenylacetylene. The reason for the high catalyst efficiency of DPCB-OMe
complexes has been investigated by reaction and structure analysis of the presumed intermediate
[Ru(CHdCHPh)Cl(CO)(DPCB-OMe)] (3a). It has been found that 3a has ample space to associate
with hydrosilane and, therefore, readily undergoes metathesis between Ru-C and H-Si bonds. This
structural feature in conjunction with the strong π-accepting ability of the DPCB-OMe ligand leads
to highly efficient catalysis for Z-selective hydrosilylation of terminal alkynes.
gain high catalytic activity.6 On the other hand, we recently found
that [RuCl(µ-Cl)(CO)(DPCB-OMe)]2 (1a), bearing a low-coordi-
nated phosphorus ligand (DPCB-OMe),7 exhibits much higher
catalyst efficiency.8 For example, reaction of PhCt CH with
HSiMe2Ph in CH2Cl2 in the presence of 1a (0.25 mol %) is
completed within 10 min at room temperature to afford (Z)-
PhCHdCHSiMe2Ph in 98% selectivity,8a whereas the same
reaction using 2m (5 mol %) instead of 1a takes 2 h for
completion.4c
Scheme 1 shows the mechanism of catalytic hydrosilylation,
which is illustrated on the basis of previous mechanistic
observations using [RuHCl(CO)(PPh3)3] catalyst (2n).9 The
Z-selective catalytic cycle is presumed to involve silyl complex
4 as the key intermediate, although participation of polynuclear
species derived from 4 cannot be excluded.6 Thus, trans-
insertion of alkyne into the Ru-Si bond of 4 (process (iv)),10,11
followed by metathesis between the Ru-C bond of 5 and the
Si-H bond of hydrosilane (process (v)),9b affords (Z)-alkenyl-
silane. Complex 4 may be isolated,4c but this catalytically active
species is generally prepared in situ from 2 via alkenyl complex
Introduction
Catalytic hydrosilylation of terminal alkynes is a simple and
efficient way of synthesizing alkenylsilanes, which are widely
used in organic synthesis.1 While the reaction generally adopts
a syn-addition process to afford (E)-alkenylsilanes, anti-addition
giving (Z)-alkenylsilanes has also been documented using rhodium,2
iridium,3 and ruthenium catalysts.4,5 As for ruthenium, Oro et al.
reported a pioneering work showing highly Z-selective hydrosi-
lylation of phenylacetylene catalyzed by [RuHCl(CO)(PiPr3)2]
(2m).4a This catalysis is applicable to several aromatic and aliphatic
acetylenes,4c,d but a relatively large amount of 2m is needed to
* To whom correspondence should be addressed. E-mail: ozawa@
scl.kyoto-u.ac.jp.
(1) (a) Ojima, I.; Li, Z.; Zhu, J. The Chemistry of Organic Silicon
Compounds; Wiley: New York, 1998; p 1687. (b) Marciniec, B. Compre-
hensiVe Handbook on Hydrosilylation; Pergamon: Oxford, 1992; p 130.
(c) Denmark, S. E.; Baird, J. D. Chem.-Eur. J. 2006, 12, 4954.
(2) (a) Takeuchi, R.; Tanouchi, N. J. Chem. Soc., Perkin Trans. 1 1994,
2909. (b) Mori, A.; Takahisa, E.; Kajiro, H.; Hirabayashi, K.; Nishihara,
Y.; Hiyama, T. Chem. Lett. 1998, 443. (c) Mori, A.; Takahisa, E.; Kajiro,
H.; Nishihara, Y.; Hiyama, T. Macromolecules 2000, 33, 1115. (d) Faller,
J. W.; D’Alliessi, D. G. Organometallics 2002, 21, 1743. (e) Mori, A.;
Takahisa, E.; Yamamura, Y.; Kato, T.; Mudalige, A. P.; Kajiro, H.;
Hirabayashi, K.; Nishihara, Y.; Hiyama, T. Organometallics 2004, 23, 1755.
(3) (a) Tanke, R. S.; Crabtree, R. H. J. Am. Chem. Soc. 1990, 112, 7984.
(b) Jun, C.-H.; Crabtree, R. H. J. Organomet. Chem. 1993, 447, 177. (c)
Sridevi, V. S.; Fan, W. Y.; Leong, W. K. Organometallics 2007, 26, 1157.
(4) (a) Esteruelas, M. A.; Herrero, L. A.; Oro, L. A. Organometallics
1993, 12, 2377. (b) Na, Y.; Chang, S. Org. Lett. 2000, 2, 1887. (c)
Katayama, H.; Taniguchi, K.; Kobayashi, M.; Sagawa, T.; Minami, T.;
Ozawa, F. J. Organomet. Chem. 2002, 645, 192. (d) Katayama, H.; Nagao,
M.; Moriguchi, R.; Ozawa, F. J. Organomet. Chem. 2003, 676, 49. (e) Aricó,
C. S.; Cox, L. R. Org. Biomol. Chem. 2004, 2, 2558. (f) Maifeld, S. V.;
Tran, M. N.; Lee, D. Tetrahedron Lett. 2005, 46, 105.
(6) Martin, M.; Sola, E.; Lahoz, F. J.; Oro, L. A. Organometallics 2002,
21, 4027.
(7) DPCB-OMe: 1,2-bis(4-methoxyphenyl)-3,4-bis[(2,4,6-tri-tert-bu-
tylphenyl)phosphinidene]cyclobutene. See for review: Ozawa, F.; Yoshifuji,
M. Dalton Trans. 2006, 4987.
(8) (a) Nagao, M.; Asano, K.; Umeda, K.; Katayama, H.; Ozawa, F. J.
Org. Chem. 2005, 70, 10511. (b) Katayama, H.; Nagao, M.; Nishimura,
T.; Matsui, Y.; Umeda, K.; Akamatsu, K.; Tsuruoka, T.; Nawafune, H.;
Ozawa, F. J. Am. Chem. Soc. 2005, 127, 4350.
(9) (a) Maruyama, Y.; Yamamura, K.; Nakayama, I.; Yoshiuchi, K.;
Ozawa, F. J. Am. Chem. Soc. 1998, 120, 1421. (b) Maruyama, Y.;
Yamamura, K.; Sagawa, T.; Katayama, H.; Ozawa, F. Organometallics
2000, 19, 1308.
(5) Ruthenium catalysts giving 2-silyl-1-alkenes have also been reported:
(a) Trost, B. M.; Ball, Z. T J. Am. Chem. Soc. 2001, 123, 12726. (b) Trost,
B. M.; Ball, Z. T. J. Am. Chem. Soc. 2003, 125, 30. (c) Trost, B. M.; Ball,
Z. T. J. Am. Chem. Soc. 2005, 127, 17644. (d) Kawanami, Y.; Sonoda, Y.;
Mori, T.; Yamamoto, K. Org. Lett. 2002, 4, 2825. (e) Menozzi, C.; Dalko,
P. I.; Cossy, J. J. Org. Chem. 2005, 70, 10717.
(10) Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J.
Organometallics 1996, 15, 1793.
(11) (a) For the mechanism of trans-insertion, see: (a) Ref 3a. (b) Ojima,
I.; Clos, N.; Donovan, R. J.; Ingellina, P. Organometallics 1990, 9, 3127.
(c) Chung, L. W.; Wu, Y.-D.; Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc.
2003, 125, 11578.
10.1021/om800119f CCC: $40.75
2008 American Chemical Society
Publication on Web 04/16/2008

2322 Organometallics, Vol. 27, No. 10, 2008
Hayashi et al.
Scheme 1
the Mes* groups are oriented orthogonal to the diphosphin-
idenecyclobutene skeleton and their rotation is sterically hin-
dered,15 the appearance of two signals may be taken as a strong
indication of the presence of two different ligands at the apical
positions of the Ru(DPCB-OMe) moiety. On the other hand,
the 31P{1H} NMR spectrum exhibited only one singlet at δ
143.9, showing the coordination of the same ligands trans to
the phosphorus atoms. Consequently, it is concluded that 1a is
a dinuclear complex symmetrically bridged by two µ-Cl ligands.
The DPCB-OMe ligand adopts chelate coordination to the
equatorial positions, whereas the CO and Cl ligands share the
apical positions of each ruthenium center. Similar structures have
been observed for related diphosphine complexes by X-ray
analysis.13,16 Unlike diphosphine analogues, which are flexible
in solution and readily transformed into other geometrical
isomers, 1a was structurally stable in CD2Cl2 at room temperature.
Complex 1a readily reacted with PPh3 (1 equiv/Ru) in CH2Cl2
at room temperature to afford 6a (eq 2) in 98% yield. The
31P{1H} NMR spectrum exhibited three sets of signals at δ 29.8
(dd, JPP ) 439 and 24 Hz), 125.3 (dd, JPP ) 24 and 12 Hz),
and 136.6 (dd, JPP ) 439 and 12 Hz), which are assigned to
PPh3 (δ 29.8) and DPCB-OMe (δ 125.3 and 136.6), respectively.
The signal pattern clearly indicates the trans,cis-disposition of
PPh3 against DPCB-OMe. Thus, the PPh3 ligand is introduced
to the equatorial position.
3 for a stability reason. Alkyne insertion into 2 (process (i))
proceeds spontaneously, whereas the subsequent reaction of 3
with hydrosilane (process (ii)) is a significantly slow process
when catalyst 2m, bearing bulky PiPr3 ligands, is employed as
catalyst.4a Thus, the low catalyst efficiency of 2m is mainly due
to the poor reactivity of [Ru(CHdCHR)Cl(CO)(PiPr3)2] (3m)
toward hydrosilane.12 The complex [Ru(CHdCHR)Cl(CO)(PPh3)2]
(3n), bearing less bulky PPh3 ligands, is sufficiently reactive, but
predominantly undergoes C-Si bond formation process (iii) giving
(E)-alkenylsilane.9b
This paper deals with the reason for the high catalyst
efficiency of 1a. On the basis of the mechanistic information
described above, we set the following objectives: (i) the
formation process of a hydrido complex (2a) from 1a; (ii) the
reactivity of 2a toward PhCt CH. It has been found that 1a is
cleanly converted to [RuH(µ-Cl)(CO)(DPCB-OMe)]2 (2a) by
the aid of water and HSiMe2Ph.
(2)
On the other hand, when 1a was treated with carbon
monoxide in CH2Cl2, a new carbonyl ligand was incorporated
into the apical coordination site (eq 3). The reaction proceeded
instantly at room temperature to give 7a, exclusively. Since the
complex could not be isolated, its structure was identified by
IR and NMR spectroscopy. The 31P{1H} NMR spectrum
showed a singlet at δ 123.6. The IR spectrum exhibited a weak
ν(CO) band at 2112 cm-1 together with strong absorption at
2042 cm-1, indicating a slightly bent arrangement of the CO
ligands in mutually trans positions.
Complex 7a gradually isomerized to thermodynamic product
7a′, which was isolated as reddish-orange crystals in 81% yield.
The 31P{1H} NMR spectrum exhibited two sets of signals at δ
128.5 and 136.5. The IR spectrum showed two ν(CO) bands at
2069 and 2005 cm-1. These spectroscopic data are consistent
with the cis,cis,cis-configuration around ruthenium.
Preparation of [RuH(µ-Cl)(CO)(DPCB-OMe)]2 (2a). Com-
plex 1a was reduced by HSiMe2Ph in CH2Cl2 at room
temperature. Preliminary attempts using dry CH2Cl2 ([H2O] <
Results and Discussion
Preparation of [RuCl(µ-Cl)(CO)(DPCB-OMe)]2 (1a). The
title compound was prepared referring to the synthetic procedure
reported for the dppf analogue [RuCl(µ-Cl)(CO)(dppf)]2 (eq 1).13
A toluene solution of [Ru(η3-allyl)Cl(CO)3] and DPCB-OMe
(1 equiv/Ru) was heated under reflux for 2 h. The resulting
[Ru(η3-allyl)Cl(CO)(DPCB-OMe)] was then reacted with an
Et2O solution of dry HCl (3 equiv/Ru) at room temperature,
causing gradual precipitation of 1a in 62% yield. Similarly,
[RuCl(µ-Cl)(CO)(DPCB)]2 and [RuCl(µ-Cl)(CO)(DPCB-CF3)]2
were prepared in 52 and 30% yields, respectively.14
(12) Complex 3m is the only ruthenium species detected in the reaction
solution using catalyst 2m.4a On the other hand, the silyl complex
[Ru(SiMe2Ph)Cl(CO)(PiPr3)2] (4m) prepared from [RuCl2(CO)(PiPr3)2] and
LiSiMe2Ph shows extremely high catalytic activity.4c
(13) Cadierno, V.; Crochet, P.; Díez, J.; García-Garrido, S. E.; Gimeno,
J. Organometallics 2003, 22, 5226.
(14) DPCB: 1,2-diphenyl-3,4-bis[(2,4,6-tri-tert-butylphenyl)phosphin-
idene]cyclobutene. DPCB-CF3: 1,2-bis(4-trifluoromethylphenyl)-3,4-bis[(2,4,6-
tri-tert-butylphenyl)phosphinidene]cyclobutene.
(1)
(15) Ozawa, F.; Kawagishi, S.; Ishiyama, T.; Yoshifuji, M. Organome-
tallics 2004, 23, 1325.
(16) (a) Drouin, S. D.; Amoroso, D.; Yap, G. P. A.; Fogg, D. E.
Organometallics 2002, 21, 1042. (b) Samantha, D. D.; Sebastien, M.; Dino,
A.; Yap, D. P. A.; Fogg, D. E. Organometallics 2005, 24, 4721. (c)
Gottschalk-Gaudig, T.; Folting, K.; Caulton, K. G. Inorg. Chem. 1999, 38,
5241.
1
In the H NMR spectrum of 1a, the tert-butyl groups at the
ortho positions of 2,4,6-tri-tert-butylphenyl substituents (Mes*)
were observed as two singlet signals at δ 1.61 and 1.64. Since

Diphosphinidenecyclobutene Ruthenium Complexes
Organometallics, Vol. 27, No. 10, 2008 2323
equiv/Ru) and proceeded even at 0 °C with a relatively small
amount of HSiMe2Ph (25 equiv/Ru). Thus, it is reasonable that
the aqua complex 8a is in equilibrium with the hydroxy complex
9a, which reacts with HSiMe2Ph via a four-membered transition
state (A) to afford 2a and silanol. Actually, when 8a was treated
with DBU (1 equiv/Ru) in the absence of HSiMe2Ph, the
31P{1H} NMR signal of 8a at δ 134.4 instantly decreased, and
a new singlet assignable to 9a appeared at δ 145.2 (8a/9a )
45/55).
(3)
Reaction of 2a with Phenylacetylene and HSiMe2Ph.
Complex 2a generated in situ from 8a and HSiMe2Ph (100
equiv/Ru) in CH2Cl2 was treated with excess phenylacetylene
(105 equiv/Ru) at 0 °C. GLC analysis revealed the formation
of styrene and (Z)- and (E)-styrylsilanes together with a small
amount of PhCt CSiMe2Ph (1%). As seen from the time-course
in Figure 2, styrene (4%, 5 equiv/Ru) and (E)-styrylsilane (6%)
are formed only at the initial stage, whereas the amount of (Z)-
styrylsilane continuously increases until the end of the reaction.20
Scheme 3 reasonably accounts for the product distribution
in Figure 2. Similarly to the monophosphine systems in Scheme
1, the DPCB-OMe complex 2a readily undergoes insertion of
phenylacetylene (process (i)). As indirect evidence, it was
observed that the RuH signal of 2a instantly disappears upon
treatment with phenylacetylene (1 equiv/Ru) at -30 °C. The
styryl complex 3a subsequently reacts with HSiMe2Ph via two
reaction processes, (ii) and (iii), giving styrene and (E)-
styrylsilane, respectively. Process (ii) irreversibly converts 3a
to 4a, whereas process (iii) reproduces 2a and then 3a. As a
result, all ruthenium species are shifted to 4a, and thereafter
the (Z)-styrylsilane formation via processes (iv) and (v) is
exclusively operative. In this case, a stoichiometric amount of
styrene should be formed, while a catalytic amount of styrene
(5 equiv/Ru) was generated in reality. This is probably due to
the presence of a side reaction converting 4a to 2a with the aid
of water or HOSiMe2Ph (process (vi)). Actually, the formation
of a comparable amount of PhMe2SiOSiMe2Ph (5 equiv/Ru)
was observed in the reaction system.21
3 mM) occasionally formed a hydride species, but the reaction
was not reproducible. Eventually, 1a was cleanly converted to
2a in the presence of a small amount of water, where the aqua
complex 8a serves as a key intermediate (Scheme 2).
17
Complex 1a readily combined with residual water in CH2Cl2
to give an equilibrium mixture of 1a and 8a ([8a]2/[1a][H2O]
) 24), from which red crystals of 8a were precipitated. Figure
1 shows the X-ray structure. Two complex molecules in a unit
j
cell (space group P1, Z ) 2) are associated with each other by
O-H · · · Cl type hydrogen bonds (O2 · · · Cl2′ ) 3.193(6) Å).
Each molecule adopts a slightly distorted octahedral configu-
ration around ruthenium. The CO and H2O ligands at the apical
positions are tilted away from the bulky Mes* groups (C1-Ru-O2
) 171.9(2)°). The Ru-O2(aqua) distance is within the range of
ruthenium aqua complexes (2.11–2.25 Å).18
Treatment of 8a with HSiMe2Ph (100 equiv/Ru) in CD2Cl2
at room temperature led to selective formation of 2a, along with
HOSiMe2Ph and PhMe2SiOSiMe2Ph as byproducts.19 The use
of excess HSiMe2Ph was essential to obtain 2a cleanly;
otherwise the reaction was a significantly slow process involving
partial decomposition of ruthenium species. Accordingly, 2a
could not be isolated, but its formation was indicated by the
appearance of a triplet signal assignable to RuH at δ –8.44 (JPH
) 12 Hz) in the 1H NMR spectrum. Since the 31P NMR signal
(1H nondecoupled) was observed as a doublet with the same
JPH coupling at δ 160.8, 2a was assigned to a dinuclear complex
bearing a hydride ligand at the apical position of each ruthenium
center (Scheme 2). The complex readily reacted with PPh3 to
give 10a, which was independently prepared from 6a and fully
characterized. The RuH signal of 10a was observed at δ –9.81
(ddd, JPH ) 155, 30, and 18 Hz). The 31P{1H} NMR signals
showed an ABX pattern that is consistent with meridional
coordination of phosphorus atoms of DPCB-OMe and PPh3
ligands.
The Reason for High Catalyst Efficiency of the DPCB-
OMe Complex. It has been found that DPCB-OMe styryl
complex 3a generated from 2a and phenylacetylene reacts
smoothly with HSiMe2Ph even at 0 °C. The observed reactivity
is clearly higher than that of monophosphine analogues.6,9 Since
it was previously observed that the reactivity of [Ru(alkenyl)-
Cl(CO)(PPh3)2] complexes toward hydrosilane is strongly
affected by steric conditions around ruthenium,9b the structure
of 3a was examined by DFT calculations using a model
compound (3a′) having 2,6-dimethylphenyl groups instead of
2,4,6-tri-tert-butylphenyl groups (Mes*).
Figure 3 shows the optimized structures of 3a′ and related
dppe complex 3b, together with the X-ray structure of
[Ru(CHdCHC6H4OMe-p)Cl(CO)(PPh3)2] (3n′).9b Complexes
3a′ and 3b have very similar structures to each other. Both
complexes adopt a square-pyramidal configuration around
ruthenium having one of the phosphorus atoms at the apical
Although the aqua complex 8a was involved, the formation
of 2a was prevented by excess water (10 equiv/Ru). On the
other hand, the reaction was effectively accelerated by DBU (1
(17) Commercial grade CH2Cl2 containing ca. 25 mM of water as
confirmed by the Karl-Fischer analysis.
(18) (a) Stanko, J. A.; Chaipayungpundhu, S. J. Am. Chem. Soc. 1970,
92, 5580. (b) Boniface, S. M.; Clark, G. R.; Collins, T. J.; Roper, W. R. J.
Organomet. Chem. 1981, 206, 109. (c) Harding, P. A.; Preece, M.; Robinson,
S. D. Inorg. Chim. Acta 1986, 118, L31. (d) Bergmeister, J. J., III; Hanson,
B. E. ; Merola, J. S. Inorg. Chem. 1990, 29, 4831. (e) Kölle, U.; Flunkert,
G.; Görissen, R.; Schmidt, M. U.; Englert, U. Angew. Chem., Int. Ed. 1992,
31, 440. (f) Sun, Y.; Taylor, N. J.; Carty, A. J. Inorg. Chem. 1993, 32,
4457. (g) Mahon, M. F.; Whittlesey, M. K.; Wood, P. T. Organometallics
1999, 18, 4068. (h) Goicoechea, J. M.; Mahon, M. F.; Whittlesey, M. K.;
Anil Kumar, P. G.; Pregosin, P. S. Dalton Trans. 2005, 588.
(20) The Z-selectivity of styrylsilane reaches 94% at the end of the
reaction; the value is somewhat lower than that observed at room temperature
(98%).8a
(21) It has been confirmed that the amounts of styrene and
PhMe2SiOSiMe2Ph are nearly twice the amount of residual water in the
system, showing the following stoichiometry:
(19) Siloxane (PhMe2SiOSiMe2Ph may be formed by dehydrative
dimerization of silanol (HOSiMe2Ph) catalyzed by HCl, which is generated
from 8a in the formation of 9a.

2324 Organometallics, Vol. 27, No. 10, 2008
Scheme 2. Reaction Processes for Conversion of 1a to 2a
Hayashi et al.
position. The styryl ligand is situated trans to the other
phosphorus atom; the P-Ru-C angles are 175.5° (3a′) and
171.9° (3b), respectively. As a result, the front side of the
RuCHdCHPh moiety is widely opened. In contrast, complex
3n′ is apparently more crowded and the ruthenium center is
sterically protected by PPh3 ligands. Accordingly, it is
reasonable that 3a associates easily with hydrosilane to cause
C-H and C-Si bond formation processes (ii) and (iii). This
structural feature is very probably due to the chelate
coordination of the DPCB-OMe ligand with a small bite angle
(ca. 83°). Since the dppe complex 3b has similar steric
conditions around ruthenium, we next examined the catalytic
activity of [RuCl(µ-Cl)(CO)(dppe)]2 (1b) toward hydrosily-
lation of terminal alkynes.
Table 1 lists the results. The dppe complex 1b is somewhat
less reactive than 1a, but much more efficient than 2m, bearing
PiPr3 ligands (runs 1–3). As for the product selectivity, 1b is
inferior to 1a, especially for the reactions of para-substituted
phenylacetylenes and 1-octyne (runs 4–11).
As seen from Scheme 1, the ratio of (Z)- and (E)-alkenylsi-
lanes is controlled by the relative ease of processes (ii) and (iii).
Process (iii) affords (E)-alkenylsilane via C-Si bond formation,
whereas process (ii) leads to C-H bond formation giving silyl
complex 4 as the carrier of the Z-selective catalytic cycle. These
processes must involve an alkenyl complex coordinated with
hydrosilane (11) as the common intermediate (Scheme 4). It is
likely that DPCB-OMe, as a strong π-acceptor ligand,15
effectively stabilizes the electron-rich silyl complex 4 to facilitate
process (ii) leading to Z-selective hydrosilylation.
Figure 1. ORTEP drawing of 8a · CH2Cl2 with thermal ellipsoids
at the 50% probability level. All hydrogen atoms and the
molecule of CH2Cl2 are omitted for clarity. Selected bond
distances (Å) and angles (deg): Ru-P1 ) 2.356(3), Ru-P2 )
2.348(4), Ru-Cl1 ) 2.391(4), Ru-Cl2 ) 2.440(3), Ru-O2 )
2.194(6), Ru-C1 ) 1.832(7), C1-O1 ) 1.129(8), P1-Ru-P2
) 83.01(12), Cl1-Ru-Cl2 ) 90.41(12), C1-Ru-O2 ) 171.9(2),
Ru-C1-O1 ) 174.2(6).
Conclusion
We have observed that complex 1a is cleanly reduced by
water and hydrosilane, where aqua complex 8a and hydroxy
complex 9a serve as key intermediates (Scheme 2). A similar
process has been reported for iridium systems.22 The resulting
hydride 2a catalyzes conversion of phenylacetylene into (E)-
and (Z)-styrylsilanes and styrene. The formation of (E)-
styrylsilane and styrene is finished at the initial stage, and
thereafter (Z)-styrylsilane is selectively formed (Figure 2).
Scheme 3 rationalizes this phenomenon. First, complex 2a
undergoes insertion of phenylacetylene to give styryl complex
3a, which subsequently reacts with hydrosilane via two reaction
processes, (ii) and (iii). These processes are competitively
operative with each other. However, since process (iii) repro-
duces 3a whereas process (ii) exclusively converts 3a to silyl
complex 4a, all catalytic species are ultimately shifted to the
Z-selective catalytic cycle. DFT calculations have suggested that
3a has ample space to associate with hydrosilane (Figure 3).
This structural feature is remarkable as compared with mono-
phosphine complexes and should be responsible for the high
catalyst efficiency of 1a.
Figure 2. Time-course of the reaction of phenylacetylene (0.52
mmol) with HSiMe2Ph (0.49 mmol) catalyzed by 2a (4.9 µmol).
The reaction was conducted in CH2Cl2 (0.5 mL) at 0 °C and
followed by GLC using toluene as an internal standard.
(22) Luo, X.-L.; Crabtree, R. H. J. Am. Chem. Soc. 1989, 111, 2527.

Diphosphinidenecyclobutene Ruthenium Complexes
Organometallics, Vol. 27, No. 10, 2008 2325
Figure 3. Comparison of calculated (3a′, 3b) and X-ray structures (3n′) of styryl complexes.
Scheme 3. Hydrosilylation Mechanism of Phenylacetylene Catalyzed by 2a
Table 1. Catalytic Hydrosilylation of RCt CH with HSiMe2Pha
Scheme 4
catalystb
conversionc product ratiod
run alkyne (R) (mol %) solvent time
(%)
[Z/E/gem]
1
2
3
4
5
6
7
8
9
Ph
Ph
Ph
1a (0.25) CH2Cl2 10 min
1b (0.25) CH2Cl2 40 min
100
100
100
100
100
100
48
100
66
100
8
98/1/1
96/4/0
97/3/0
99/1/0
49/51/0
97/1/2
72/28/0
97/1/2
62/32/6
97/1/2
36/64/0
2m (5)
CH2Cl2 2 h
toluene 2 h
toluene 2 h
4-MeOC6H4 1a (1)
4-MeOC6H4 1b (1)
4-CF3C6H4 1a (0.5) toluene 5 h
4-CF3C6H4 1b (0.5) toluene 5 h
4-MeO2C6H4 1a (0.25) CH2Cl2 3 h
4-MeO2C6H4 1b (0.25) CH2Cl2 5 h
10 n-C6H13
11 n-C6H13
1a (1)
1b (1)
toluene 5 h
toluene 5 h
a Reactions were run with RCt CH (1.05 mmol), HSiMe2Ph (1 mmol),
and solvent (1 mL) at room temperature. b 1a: [RuCl(µ-Cl)(CO)(DPCB-
OMe)]2; 1b: [RuCl(µ-Cl)(CO)(dppe)]2; 2m: [RuHCl(CO)(PiPr3)2].
c Determined by GLC. d Determined by 1H NMR spectroscopy.
gem-isomer: CH2dCR(SiMe2Ph).
unless otherwise noted. NMR spectra were recorded on a Varian
Mercury 300 spectrometer (1H NMR 300 MHz, 13C NMR 75.5
MHz, 31P NMR 121.5 MHz). IR spectra were recorded on a JASCO
FT/IR-410 instrument. Elemental analysis was performed by the
ICR Analytical Laboratory, Kyoto University. The compounds
Experimental Section
General Considerations. All manipulations were performed
under a nitrogen atmosphere using conventional Schlenk techniques

2326 Organometallics, Vol. 27, No. 10, 2008
Hayashi et al.
[Ru(η-C3H5)Cl(CO)3]23 and DPCB-Y (Y ) OMe, H, CF3)15 were
synthesized according to the literature.
31P{1H} NMR (CD2Cl2, 20 °C): δ 29.8 (dd, JPP ) 439 and 24
Hz), 125.3 (dd, JPP ) 24 and 12 Hz), 136.6 (dd, JPP ) 439 and 12
Hz). Anal. Calcd for C73H87Cl2O3P3Ru: C, 68.64; H, 6.86. Found:
C, 68.59; H, 7.10.
Preparation of [RuCl(µ-Cl)(CO)(DPCB-OMe)]2 (1a). A solu-
tion of [Ruη3-C3H5)Cl(CO)3] (154 mg, 0.590 mmol) and DPCB-
OMe (484 mg, 0.594 mmol) in toluene (5.9 mL) was refluxed for
2 h with stirring. The dark red solution was cooled to room
temperature, and a solution of dry HCl in Et2O (1.1 M, 1.61 mL,
1.77 mmol) was added. The mixture was stirred at room temperature
overnight to give a red precipitate of 1a, which was collected by
filtration, washed with Et2O (3 mL × 2) at -30 °C, and dried under
vacuum (370 mg, 62%). The complexes [RuCl(µ-Cl)(CO)(dppe)]2
(1b), [RuCl(µ-Cl)(CO)(DPCB)]2 (1c), and [RuCl(µ-Cl)(CO)(DPCB-
CF3)]2 (1d) were similarly prepared in 49, 52, and 30% yields,
respectively. The complexes were identified by NMR and IR
spectroscopy and elemental analysis, while the 13C{1H} NMR
spectra were not observed for solubility reasons.
Preparation of [RuCl2(CO)2(DPCB-OMe)] (7a and 7a′). The
CO gas was passed through a suspension of 1a (200 mg, 0.0985
mmol) in CH2Cl2 (5.0 mL) at room temperature. The mixture
quickly changed to a red homogeneous solution. The 31P{1H} NMR
spectrum showed the selective formation of 7a. IR (CH2Cl2): 2112
1
(w), 2042 cm-1 (s). H NMR (CD2Cl2, 20 °C): δ 1.43 (s, 18H,
p-tBu), 1.65 (s, 36H, o-tBu), 3.70 (s, 6H, OMe), 6.42 (br, 8H, Ar),
7.56 (m, 4H, m-PAr). 31P{1H} NMR (CD2Cl2, 20 °C): δ 123.6 (s).
The solution of 7a thus prepared was stirred for 7 h at room
temperature. Volatile substances were removed under reduced
pressure. The residue was dissolved in a minimum amount of
CH2Cl2, layered with Et2O, and allowed to stand at room temper-
ature to give orange crystals of 7a′ (167 mg, 81%). Mp: 224 °C.
1
1a. Mp: 246 °C. IR (KBr): 1995 cm-1 (s). H NMR (CD2Cl2,
20 °C): δ 1.36 (s, 36H, p-tBu), 1.61 (s, 36H, o-tBu), 1.64 (s, 36H,
o-tBu), 3.68 (s, 12H, OMe), 6.37 (d, JHH ) 9.2 Hz, 8H, Ar), 6.43
(d, JHH ) 9.2 Hz, 8H, Ar), 7.40 (s, 4H, m-PAr), 7.44 (s, 4H, m-PAr).
31P{1H} NMR (CD2Cl2, 20 °C): δ 143.9 (s). Anal. Calcd for
1
IR (KBr): 2069 (s), 2005 cm-1 (s). H NMR (CDCl3, 20 °C): δ
1.41 (s, 18H, p-tBu), 1.63 (s, 18H, o-tBu), 1.66 (s, 18H, o-tBu),
3.71 (s, 3H, OMe), 3.72 (s, 3H, OMe), 6.38–6.48 (m, 8H, Ar),
7.48–7.54 (m, 4H, m-PAr). 13C{1H} NMR (CDCl3, 20 °C): δ 31.4,
31.5, 33.9, 34.0, 34.3, 34.3, 35.5, 38.5 (d, JPC ) 2 Hz), 38.9 (d,
JPC ) 2 Hz), 38.9 (d, JPC ) 2 Hz), 39.3 (d, JPC ) 2 Hz), 55.2
(OMe), 113.8, 113.8, 121.9 (d, JPC ) 9 Hz), 122.4 (d, JPC ) 9
Hz), 122.6 (d, JPC ) 9 Hz), 122.9 (d, JPC ) 9 Hz), 123.4, 123.5,
124.9, 125.1, 129.1 (d, JPC ) 1 Hz), 129.2 (d, JPC ) 1 Hz), 129.4
(d, JPC ) 1 Hz), 129.5 (d, JPC ) 1 Hz), 153.8 (m, P ) CC), 157.2,
157.6, 159.4 (d, J ) 3 Hz), 159.7 (d, J ) 2 Hz), 160.5 (d, J ) 4
Hz), 160.6 (d, J ) 4 Hz), 175.8 (dd, JPC ) 57 and 19 Hz, PdC),
176.9 (dd, JPC ) 41 and 16 Hz, PdC), 189.7 (dd, JPC ) 147 and
12 Hz, CO), 192.4 (dd, JPC ) 17 and 13 Hz, CO). 31P{1H} NMR
(CDCl3, 20 °C): δ 128.5 (s), 136.5 (s). Anal. Calcd for
C60H82Cl2O5P2Ru: C, 64.50; H, 7.40. Found: C, 64.32; H, 7.01.
Preparation of [RuCl2(CO)(H2O)(DPCB-OMe)] (8a). Com-
plex 1a (15.0 mg, 7.38 µmol) was dissolved in CH2Cl2 (1.0 mL)
containing a small amount of water (ca. 25 mM)17 and allowed to
stand at room temperature. Red crystals of 8a were precipitated
over hours. The product was collected by filtration, washed with
Et2O, and dried under vacuum (15.0 mg, 98%). Mp: 255 °C. IR
(KBr): 1989 cm-1 (s). 1H NMR (CD2Cl2, 20 °C): δ 1.46 (s, 18H,
p-tBu), 1.61 (s, 18H, o-tBu), 1.68 (s, 18H, o-tBu), 2.73 (br, 2H,
H2O), 3.73 (s, 6H, OMe), 6.45 (d, JHH ) 7.2 Hz, 4H, Ar), 6.51 (d,
JHH ) 8.4 Hz, 4H, Ar), 7.59 (s, 2H, m-PAr), 7.61 (s, 2H, m-PAr).
31P{1H} NMR (CD2Cl2, 20 °C): δ 134.4 (s). Anal. Calcd for
C55H74Cl2O4P2Ru: C, 63.94; H, 7.22. Found: C, 64.23; H, 7.05.
C
110H144Cl4O6P4Ru2: C, 65.08; H, 7.15. Found: C, 64.98; H, 7.10.
1
1b. Mp: 250 °C. IR (KBr): 1977 cm-1 (s). H NMR (CD2Cl2,
20 °C): δ 2.63 (m, 4H, CH2), 3.00 (m, 4H, CH2), 7.41 (m, 24H,
Ph), 7.78 (m, 8H, Ph), 7.94 (m, 8H, Ph). 31P{1H} NMR (CD2Cl2,
20 °C): δ 65.5 (s). Anal. Calcd for C54H48Cl4O2P4Ru2: C, 54.19;
H, 4.04. Found: C, 53.93; H, 4.17.
1
1c. Mp: 235 °C. IR (KBr): 1994 cm-1 (s). H NMR (CD2Cl2,
20 °C): δ 1.34 (s, 36H, p-tBu), 1.62 (s, 36H, o-tBu), 1.64 (s, 36H,
o-tBu), 6.51 (d, JHH ) 7.6 Hz, 8H, o-Ar), 6.87 (t, JHH ) 7.8 Hz,
8H, m-Ar), 7.08 (t, JHH ) 7.4 Hz, 4H, p-Ar), 7.38 (s, 4H, m-PAr),
7.41 (s, 4H, m-PAr). 31P{1H} NMR (CD2Cl2, 20 °C): δ 153.3 (s).
Anal. Calcd for C106H136Cl4O2P4Ru2: C, 66.65; H, 7.18. Found: C,
66.50; H, 7.07.
1
1d. Mp: 235 °C. IR (KBr): 2009 cm-1 (s). H NMR (CD2Cl2,
20 °C): δ 1.34 (s, 36H, p-tBu), 1.62 (s, 36H, o-tBu), 1.64 (s, 36H,
o-tBu), 6.61 (d, JHH ) 8.4 Hz, 8H, o-Ar), 7.14 (d, JHH ) 8.4 Hz,
8H, m-Ar), 7.43 (s, 8H, m-PAr). 31P{1H} NMR (CD2Cl2, 20 °C):
δ 164.9 (s). Anal. Calcd for C110H134Cl4F12O2P4Ru2: C, 60.49; H,
6.18. Found: C, 60.30; H, 6.00.
Preparation of [RuCl2(CO)(PPh3)(DPCB-OMe)] (6a). A solu-
tion of 1a (101 mg, 0.0497 mmol) and PPh3 (26.1 mg, 0.100 mmol)
in CH2Cl2 (3.2 mL) was stirred for 5 min at room temperature.
Volatile materials were removed under reduced pressure. The
residue was dissolved in a minimum amount of CH2Cl2, layered
with pentane, and allowed to stand at room temperature to give
orange crystals of 6a (124 mg, 98%). Mp: 175 °C. IR (KBr): 1964
Preparation of [Ru(OH)(µ-Cl)(CO)(DPCB-OMe)]2 (9a)
(NMR Tube Reaction). Complex 1a (5.0 mg, 2.46 µmol) was
dissolved in CD2Cl2 (0.5 mL) containing a small amount of water
(ca. 25 mM), and a solution of 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) in CD2Cl2 (48.9 mM, 101 µL, 4.93 µmol, 1 equiv/Ru) was
added at 0 °C. The color of the solution instantly changed from
red to deep red. The 31P{1H} NMR spectrum showed the formation
of a new species assignable to 9a in addition to 8a (8a/9a ) 45/
1
cm-1 (s). H NMR (CD2Cl2, 20 °C): δ 1.27 (s, 9H, o-tBu), 1.41
(s, 9H, o-tBu), 1.46 (s, 9H, p-tBu), 1.48 (s, 9H, p-tBu), 1.63 (s, 9H,
o-tBu), 1.70 (s, 9H, o-tBu), 3.67 (s, 3H, OMe), 3.71 (s, 3H, OMe),
6.34 (d, 2H, JHH ) 8.7 Hz, Ar), 6.42 (d, 2H, JHH ) 8.7 Hz, Ar),
6.49 (d, 2H, JHH ) 8.7 Hz, Ar), 6.60 (d, 2H, JHH ) 8.7 Hz, Ar),
7.10 (t, 6H, JHH ) 6.6 Hz, Ph), 7.31 (t, 3H, JHH ) 6.6 Hz, Ph),
7.53–7.66 (m, 10H, m-PAr and Ph). 13C{1H} NMR (CD2Cl2, 20
1
55). H NMR (CD2Cl2, 20 °C): δ 1.41 (s, 36H, p-tBu), 1.64 (br,
72H, o-tBu), 3.68 (s, 12H, OMe), 6.37–6.42 (m, 16H, Ar), 7.47 (s,
4H, m-PAr), 7.50 (s, 4H, m-PAr). 31P{1H} NMR (CD2Cl2, 20 °C):
δ 145.2 (s).
°C): δ 31.5, 31.6, 34.2, 34.3, 34.7, 35.0, 35.6, 35.7, 39.0 (d, JPC
2 Hz), 39.2 (d, JPC ) 2 Hz), 39.9 (d, JPC ) 2 Hz), 39.9 (d, JPC
)
)
2 Hz), 55.5 (OMe), 55.5 (OMe), 113.7, 113.7, 114.0, 114.1, 123.2
(d, JPC ) 8 Hz), 123.3 (d, JPC ) 8 Hz), 124.5 (d, JPC ) 8 Hz),
125.9 (d, JPC ) 8 Hz), 126.5, 127.3, 127.3, 127.6 (d, JPC ) 10
Preparation of [RuH(Cl)(CO)(DPCB-OMe)]2 (2a) (NMR
Tube Reaction). Complex 1a (5.0 mg, 2.46 µmol) was dissolved
in CD2Cl2 (0.5 mL) containing a small amount of water (ca. 25
mM). HSiMe2Ph (67.2 mg, 0.493 mmol, 100 equiv/Ru) was added
at 0 °C, and the mixture was allowed to stand at room temperature
for 1 h. The NMR spectra showed the selective formation of 2a.
1H NMR (CD2Cl2, -5 °C): δ -8.44 (t, JPH ) 12 Hz, 1H, RuH).
31P NMR (CD2Cl2, -5 °C): δ 160.8 (d, JPH ) 12 Hz).
Hz), 129.8 (d, JPC ) 2 Hz), 129.9 (d, JPC ) 2 Hz), 130.2 (d, JPC
)
3 Hz), 130.3 (d, JPC ) 2 Hz), 130.4 (d, JPC ) 2 Hz), 132.9 (d, JPC
) 3 Hz), 133.5 (d, JPC ) 3 Hz), 135.6 (d, JPC ) 9 Hz), 153.4 (m,
PdCC), 154.9, 157.6 (d, JPC ) 2 Hz), 157.8, 159.3, 160.7 (d, JPC
) 3 Hz), 160.7 (d, JPC ) 3 Hz), 177.6 (m, PdC), 198.9 (m, CO).
The same reaction was examined in the presence of DBU. A
solution of 2a was prepared from 1a (5.0 mg, 2.46 µmol) and
(23) Sbrana, B.; Braca, G.; Piacenti, F.; Pino, P. J. Organomet. Chem.
1968, 13, 240.

Diphosphinidenecyclobutene Ruthenium Complexes
Organometallics, Vol. 27, No. 10, 2008 2327
Table 2. Crystallographic Data for 8a · CH2Cl2
(dd, JPP ) 19 and 15 Hz). Anal. Calcd for C77H98ClO4P3Ru: C,
70.22; H, 7.50. Found: C, 70.05; H, 7.69.
formula
fw
C56H76Cl4O4P2Ru
1117.98
Reaction of 2a with Phenylacetylene and HSiMe2Ph. A
solution of 2a (4.92 µmol) was prepared from 1a (5.0 mg, 2.46
µmol), HSiMe2Ph (67.2 mg, 0.493 mmol), and wet CH2Cl2 (0.5
mL). Phenylacetylene (52.8 mg, 0.517 mmol) was added at 0 °C,
and the amounts of organic compounds in the system were analyzed
at intervals by GLC using toluene as an internal standard.
DFT Calculations. The geometry optimization of compounds
3a′ and 3b was carried out with the program package Gaussian
9824 using B3LYP in conjunction with the SDD basis set and
effective core potential for Ru and 6-31G(d) basis set for other
atoms.
X-ray Structural Analysis of 8a. The X-ray diffraction study
was performed on a Rigaku Mercury CCD diffractometer with
graphite-monochromated Mo KR radiation (γ ) 0.71070 Å). The
intensity data were collected at 173 K and corrected for Lorentz
and polarization effects and absorption (numerical). The structure
was solved by DIRDIF9925 and refined by full-matrix least-squares
procedures on F2 for all reflections (SHELXL-97).26 Hydrogen
atoms except for those of the H2O ligand were placed using AFIX
instructions. Crystallographic data have been deposited with the
Cambridge Crystallographic Center: CCDC No. 671813. A sum-
mary of the data is given in Table 2.
cryst size, mm
cryst syst
a (Å)
0.10 × 0.06 × 0.05
triclinic
14.556(15)
14.86(2)
b (Å)
c (Å)
15.45(2)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
space group
Z
81.08(11)
64.64(9)
71.75(10)
2869(6)
j
P1 (#2)
2
dcalcd (g cm-3
)
1.294
0.557
3.15–27.48
22 289
12 235 (Rint ) 0.0593)
0.9464–0.9727
µ (Mo KR) (mm-1
θ range (deg)
no. of reflns collected
no. of unique reflns
transmn factor
)
no. of reflns with I > 2σ(I)
8335
624
1.119
no. of variables
goodness-of-fit on F2
final R indices (I > 2σ(I))
R indices (all data)
R1 ) 0.0797, wR2 ) 0.2292
R1 ) 0.1178, wR2 ) 0.3074
CD2Cl2 (0.5 mL) containing a small amount of water (ca. 25 mM)
at room temperature. HSiMe2Ph (0.123 mmol, 25 equiv/Ru) and
DBU (4.93 µmol, 1 equiv/Ru) were successively added, and the
sample solution was allowed to stand at room temperature. The
31P{1H} NMR spectrum showed exclusive formation of 2a (δ
160.8).
Acknowledgment. This work was supported by Grants-
in-Aid for Scientific Research on Priority Areas (No.
18064010, “Synergy of Elements”) from the Ministry of
Education, Culture, Sports, Science, and Technology, Japan.
Preparation of [RuH(Cl)(CO)(PPh3)(DPCB-OMe)] (10a). To
a solution of 6a (62.0 mg, 0.0485 mmol) in CH2Cl2 (2.5 mL) was
added HSiMe2Ph (13.2 mg, 0.0970 mmol). The solution was stirred
at 40 °C for 1.5 h. Volatile materials were removed under reduced
pressure. The residue was washed with pentane and recrystallized
from Et2O/pentane to give 10a as an orange powder (46.0 mg, 78%).
Supporting Information Available: Tables with Cartesian
coordinates of the optimized structures of 3a′ and 3b; crystal-
lographic data of 8a in cif format. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
Mp: 145 °C. IR (KBr): 1938 cm-1 (CO). H NMR (CD2Cl2, 20
OM800119F
°C): δ -9.81 (ddd, JPH ) 155, 30 and 18 Hz, 1H, RuH), 1.19 (s,
9H, o-tBu), 1.40 (s, 9H, p-tBu), 1.45 (s, 9H, p-tBu), 1.52 (s, 9H,
o-tBu), 1.55 (s, 9H, o-tBu), 1.78 (s, 9H, o-tBu), 3.67 (s, 3H, OMe),
(24) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery Jr., J. A.;
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.; Chen, W.; Wong, M. W.; Andres, J. L.; Gonzalez,
C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 98, ReVision
A.9; Gaussian, Inc.: Pittsburgh, PA, 1998.
3.70 (s, 3H, OMe), 6.34 (d, JHH ) 9.2 Hz, 2H, Ar), 6.42 (d, JHH
8.8 Hz, 2H, Ar), 6.56 (d, JHH ) 8.0 Hz, 2H, Ar), 6.58 (d, JHH
)
)
7.2 Hz, 2H, Ar), 7.14–7.18 (m, 6H, Ph), 7.27–7.31 (m, 3H, Ph),
7.37 (s, 2H, m-PAr), 7.49 (s, 2H, m-PAr), 7.61–7.66 (m, 6H, Ph).
13C{1H} NMR (CD2Cl2, 20 °C): δ 31.8, 31.8, 34.7, 34.7, 35.7,
39.1, 39.5, 39.6, 39.7, 55.6 (OMe), 55.7 (OMe), 113.8, 114.1, 123.0
(d, JPC ) 5 Hz), 123.3 (d, JPC ) 5 Hz), 124.2 (d, JPC ) 5 Hz),
124.7 (d, JPC ) 5 Hz), 127.9 (d, JPC ) 10 Hz), 129.7 (d, JPC ) 5
Hz), 129.8, 130.3 (d, JPC ) 5 Hz), 135.4 (d, JPC ) 10 Hz), 135.9,
136.3, 152.7 (m, PdCC), 155.3, 157.7, 157.8, 158.8, 160.3 (d, JPC
) 3 Hz), 160.4 (d, JPC ) 3 Hz), 176.9–177.7 (m, PdC),
201.9–202.3 (m, CO). 31P{1H} NMR (CD2Cl2, 20 °C): δ 48.8 (dd,
JPP ) 362 and 15 Hz), 148.2 (dd, JPP ) 362 and 19 Hz), 150.0
(25) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; García-Grana, S.;
Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF99 Program System;
University of Nijmegen: The Netherlands, 1999.
(26) Sheldrick, G. M. SHELXL-97; University of Göttingen: Germany,
1997.