(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) (meo-biphep) as a six-electron donor in [Ru(η5-C8H11)(MeO-BIPHEP)]+ cations. coordination of a biaryl double bond, as shown by13C NMR and x-ray crystallography

Article abstract of DOI:10.1021/om960812x

The reaction of the MeO-BIPHEP complex Ru(OAc)₂(1a) (1a = (6,6′-dimethoxybiphenyl-2,2′-diyl)bis(bis(3,5-di-tert-butylphenyl) phosphine), with HBF₄ and 1,5-COD affords [Ru(η⁵-C₈H₁₁)(1a)]BF₄ (4), in which la functions as a 6e donor to Ru(II) via an unexpected coordination of one of the biaryl double bonds. The isopropyl analog [Ru(η⁵-C₈H₁₁)(1b)]CF₃-CO ₂ (6; 1b = (6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diisopropylphosphine)) was prepared by starting from [Ru(CF₃CO₂)₂(1.5-COD)]₂ and reveals the same η⁴-bonding mode. Both complexes were characterized by detailed multidimensional NMR studies, and the X-ray structure for 6 is reported. Although the ³¹P chemical shifts for this new η⁴-bonding mode are informative, the ¹³C resonance positions for the coordinated biaryl carbons are a more reliable criterion for recognizing this type of interaction. These chemical shift data are difficult to obtain using routine ¹³C measurements, and a long-range ¹³C,¹H-correlation is recommended as the method of choice. Complex 4 exhibits dynamic behavior in solution, as shown by 2-D NOESY. This exchange process can be rationalized by assuming that the double bond dissociates; however, complex 6 does not show an analogous exchange process at ambient temperature.

Full text of DOI:10.1021/om960812x

Organometallics 1997, 16, 537-543
537
(6,6′-Dim eth oxybip h en yl-2,2′-d iyl)bis(d ip h en ylp h osp h in e)
(MeO-BIP HEP ) a s a Six-Electr on Don or in
[Ru (η5-C8H11)(MeO-BIP HEP )]+ Ca tion s. Coor d in a tion of
a Bia r yl Dou ble Bon d , As Sh ow n by 13C NMR a n d X-r a y
Cr ysta llogr a p h y
Nantko Feiken, Paul S. Pregosin,* and Gerald Trabesinger
Inorganic Chemistry ETH Zu¨rich, Universita¨tstrasse 6, CH-8092 Zu¨rich, Switzerland
Michelangelo Scalone*
F. Hoffmann-La Roche AG, CH-4070 Basel, Switzerland
Received September 24, 1996X
The reaction of the MeO-BIPHEP complex Ru(OAc)2(1a ) (1a ) (6,6′-dimethoxybiphenyl-
2,2′-diyl)bis(bis(3,5-di-tert-butylphenyl)phosphine), with HBF4 and 1,5-COD affords [Ru(η5-
C8H11)(1a )]BF4 (4), in which 1a functions as a 6e donor to Ru(II) via an unexpected
coordination of one of the biaryl double bonds. The isopropyl analog [Ru(η5-C8H11)(1b)]CF3-
CO2 (6; 1b ) (6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diisopropylphosphine)) was prepared by
starting from [Ru(CF3CO2)2(1,5-COD)]2 and reveals the same η4-bonding mode. Both
complexes were characterized by detailed multidimensional NMR studies, and the X-ray
structure for 6 is reported. Although the 31P chemical shifts for this new η4-bonding mode
are informative, the 13C resonance positions for the coordinated biaryl carbons are a more
reliable criterion for recognizing this type of interaction. These chemical shift data are
difficult to obtain using routine 13C measurements, and a long-range 13C,1H-correlation is
recommended as the method of choice. Complex 4 exhibits dynamic behavior in solution,
as shown by 2-D NOESY. This exchange process can be rationalized by assuming that the
double bond dissociates; however, complex 6 does not show an analogous exchange process
at ambient temperature.
In tr od u ction
a useful complement to the well-known4 BINAP class,
where, for hydrogenation chemistry, there have been
detailed mechanistic studies.5 The preparative chem-
istry for 1 is sufficiently flexible such that the methoxy
group can be replaced by a methyl substituent. More-
over, a variety of R groups can be introduced.2 The
precursor most often used in the catalytic work is of the
form Ru(OAc)2(1) (2) or a related trifluoroacetate com-
plex.
Homogeneous catalysts based on ruthenium com-
plexes are now widely employed in enantioselective hy-
drogenation chemistry.1 Within this context, the bi-
dendate phosphine ligands MeO-BIPHEP (1), are now
We have recently reported6 that Ru(OAc)2(1a ) (2a )
under hydrogenation conditions, i.e., excess HBF4, a
molecular hydrogen atmosphere, and 2-propanol as
solvent, affords the novel five-coordinate bis(solvento)
hydrido complex [RuH(2-propanol)2(1a )]BF4 (3).
recognized to be useful chiral auxiliaries for the enan-
tioselective homogeneous hydrogenation of olefins.2,3
The observed chemical and optical yields are often
excellent, with enantiomeric excesses (ee’s) frequently
>95%. Thus, these MeO-BIPHEP auxiliaries represent
H2
Ru(OAc)2(1a ) + 2HBF4
(60 atm) 8
333 K, PriOH
[RuH(PriOH)2(1a )]BF4 + 2HOAc + HBF4 (1)
The structure for 3 was determined by X-ray diffraction
methods6 and is best described as a distorted square
X Abstract published in Advance ACS Abstracts, J anuary 15, 1997.
(1) Kitamura, M.; Noyori, R. In Modern Synthetic Methods; Schef-
fold, R., Ed.; Springer-Verlag: Berlin, 1989; Vol. 5, p 116. Genet, J . P.
Acros Org. Acta 1995, 1 , 4. Mudalige, D. C.; Rettig, S. J .; J ames, B.
R.; Cullen, W. R. J . Chem. Soc., Chem. Commun. 1993, 830. Cashman,
R. S. M.; Butler, I. R.; Cullen, W. R.; J ames, B. R.; Charland, J . P.;
Simpson, J . Inorg. Chem. 1992, 31, 5509.
(2) Schmid, R.; Broger, E. A.; Cereghetti, M.; Crameri, Y.; Foricher,
J .; Lalonde, M.; Mueller, R. K.; Scalone, M.; Schoettel, G.; Zutter, U.
Pure Appl. Chem. 1996, 68, 131. Heiser, B.; Broger, E. A.; Crameri, Y.
Tetrahedron: Asymmetry 1991, 2, 51. BIPHEP is the generic name
suggested.
(4) Ohta, T.; Tonomura, Y.; Nozaki, K.; Takaya, H.; Mashima, K.
Organometallics 1996, 15, 1521. Zhang, X.; Uemura, T.; Matsumura,
K.; Sayo, N.; Kumobayashi, H.; Takaya, H. Synlett 1994, 501. Kita-
mura, M.; Tokunaga, M.; Noyori, R. J . Am. Chem. Soc. 1993, 115, 144.
Ohta, T.; Miyake, T.; Seido, N.; Kumobayashi, H.; Akutagawa, S.;
Takaya, H. Tetrahedron Lett. 1992, 33, 635. Mashima, K.; Hino, T.;
Takaya, H. J . Chem. Soc., Dalton Trans 1992, 2099. Ohta, T.; Takaya,
H.; Noyori, R. Inorg. Chem. 1988, 27, 566.
(5) (a) Ashby, M. T.; Khan, M. A.; Halpern, J . Organometallics 1991,
10, 2011. (b) Ashby, M. T.; Halpern, J . J . Am. Chem. Soc. 1991, 113,
589.
(6) Currao, A.; Feiken, N.; Macchioni, A.; Nesper, R.; Pregosin, P.
S.; Trabesinger, G. Helv. Chim. Acta 1996, 79, 1587.
(3) Mezzetti, A.; Tschumper, A.; Consiglio, G. J . Chem. Soc., Dalton
Trans. 1995, 49. Mezzetti, A.; Costella, L.; Del Zotto, A.; Rigo, P.;
Consiglio, G. Gazz. Chim. Ital. 1993, 123, 155.
S0276-7333(96)00812-6 CCC: $14.00 © 1997 American Chemical Society

538 Organometallics, Vol. 16, No. 4, 1997
Feiken et al.
pyramid. This is a rare example of a chiral hydrido bis-
(solvento) complex.
As 1a stabilizes the five-coordinate coordinatively
unsaturated complex 3, and since there is little known
on Ru(II)-organometallic chemistry with MeO-BIPHEP
ligands, we attempted to prepare complexes of 1 con-
taining 1,5-COD. We report here NMR and X-ray
studies for two ruthenium complexes of 1 in which an
unusual MeO-BIPHEP coordination mode is observed.
Resu lts a n d Discu ssion
NMR Stu d ies on [Ru (η5-C8H11)(1a )]BF 4. In me-
thylene chloride, Ru(OAc)2(1a ) reacts with 1,5-COD and
HBF4 to afford 4 in good yield.
2HBF4
Ru(OAc)2(1a ) + 1,5-COD
8 4 + 2HOAc + HBF4
CH2Cl2
(2)
F igu r e 1. 31P NMR spectra for 4 (upper trace) and 6 (lower
trace). Note the relatively large differences between the two
2
31P chemical shifts. The J (P,P) values are 47 and 40 Hz
for 4 and 6, respectively (500 MHz, CD2Cl2; 4 at 193 K, 6
at room temperature).
Ta ble 1. 1H a n d 13C NMR Da ta for th e η5-C8H11
Liga n d s in 4 a n d 6a
4
6
position
1H
13C
1H
13C
Complex 4 affords satisfactory microanalytical and mass
spectral data, with the molecular ion found at m/e
1239.7. The 31P NMR spectrum (see Figure 1), shows
a routine AX spin system; however, the phosphorus
chemical shifts, at 69.6 ppm and -11.2 ppm (!) are
unexpected, with the latter coming in a region often
9
10
11
12
13
14
exo
endo
15
exo
endo
16
4.14
5.08
5.37
0.95
2.32
57.8
89.8
114.7
97.7
69.5
4.16
4.92
5.27
0.85
2.84
49.6
85.4
114.3
99.2
62.3
-
0.79
-0.83
ca. 21
ca. 18
ca. 25
1.87
1.54
associated with uncoordinated phosphine. The BF4
anion was also confirmed via its 19F NMR spectrum.
Initially, we considered an acetate complex; however,
it was clear from infrared and 13C measurements that
this anion was not present.
0.48
-0.42
1.09
0.02
19.4
29.5
exo
endo
1.94
1.60
The nature of the organometallic ligand in 4 was not
immediately obvious; however, a routine 2-D 13C,1H
correlation showed only three aliphatic CH2 type sig-
nals, a clear indication that the 1,5-COD ligand had
been transformed. There are five CH-absorptions in the
region 57-114 ppm, and these 13C chemical shift data
are strongly suggestive of the ruthenium-cyclooctadienyl
fragment Ru(η5-C8H11);7 the following diagram shows
one of the shielded protons of this fragment at -0.42
ppm:
a
Chemical shifts in ppm, relative to TMS.
absorptions, at -0.42 ppm, as an apparent quartet, is
-
typical10-12 for the η5-C8H11 ligand coordinated to
ruthenium. This represents yet another example of the
anisotropic effect of a π-system on aliphatic protons.13
Interestingly, there is a second proton at even lower
frequency, -0.83 ppm, stemming from one of the CH2
groups. Further, one of the η5-CH resonances appears
at very low frequency at 0.95 ppm. The NMR charac-
-
teristics for this η5-C8H11 ligand are given in Table 1.
At this point, we considered a possible five-coordinate
structure, e.g., [Ru(η5-C8H11)(1a )]BF4, since 1a can
stabilize five-coordination; however, we noted two non-
1
The H spectrum, assigned via NOESY (and ROESY,
as the molecule is moderately large and moves slowly8,9
at 193 K) plus the usual forms of proton correlation spec-
troscopy, confirms the presence of this η5 six-electron
donor in that one of the two observed low-frequency
(9) Ernst, R. R.; Bodenhausen, G.; Wokaun, A. In Principles of
Nuclear Magnetic Resonance in One and Two Dimensions; Clarendon
Press, Oxford, U.K., 1987, pp 516-538.
(10) Bouachir, F.; Chaudret, B.; Dahan, F.; Agbossou, F.; Tkatch-
enko, I. Organometallics 1991, 10, 455.
(11) Cox, D. N.; Roulet, R. J . Chem. Soc., Chem. Commun. 1988,
951.
(12) Ro¨thlisberger, M. S.; Salzer, A.; Bu¨rgi, H. B.; Ludi, A. Orga-
nometallics 1986, 5, 298.
(13) Pretsch, E.; Seibl, J .; Simon, W. Strukturaufkla¨rung organischer
Verbindungen; Springer-Verlag: Berlin, 1986.
(7) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: London, 1981; p 246.
(8) Hull, W. E. In Methods in Stereochemical Analysis; Croasmun,
W. R., Carlson, R. M. K., Eds.; VCH: New York, 1987, Vol. 9, p 153.
(b) Macura, S.; Ernst, R. R. Mol. Phys. 1980, 41, 95.

MeO-BIPHEP as a Six-Electron Donor in Ru Cations
Organometallics, Vol. 16, No. 4, 1997 539
Ta ble 2. 1H a n d 13C NMR Da ta for th e
MeO-BIP HEP Liga n d s in 4 a n d 6a
4
6
position
1H
13C
position
1H
13C
1
2
3
4
5
6
95.1
157.6
102.3
133.7
120.6
74.5
1
2
3
4
5
6
95.9
166.9
100.8
132.8
119.3
76.4
6.47
7.68
7.35
6.25
7.57
6.80
13C resonances for the coordinated double bond, C(7)-
C(8), are found at 101.8 and 76.5 ppm for C(7) and C(8),
respectively, i.e., close to those values mentioned above,
suggesting that our 13C values for 4 are reasonable for
this type of bonding. Although the observed bonding
is unprecedented for BIPHEP ligands, we note that
Pathak et al.15 have recently reported the solid-state
structure for [Ru(Cp)(BINAP)]CF3SO3, in which they
find the same type of six-electron donation from the
BINAP ligand. They also note widely dispersed 31P
chemical shifts (74.0 and 14.1 ppm) but did not consider
the 13C approach to the solution structure proof. In
retrospect, the 31P data are a useful indication (but not
proof) of the unusual coordination mode.
7
1′
2′
3′
4′
5′
6′
7′
3.34
56.9
7
1′
2′
3′
4′
5′
6′
7′
3.58
55.6
139.7
168.3
112.7
131.4
122.5
135.4
58.0
134.4
158.4
113.6
131.1
121.6
132.7
55.4
6.19
6.93
7.09
6.76
7.43
7.07
3.69
7.18
7.62
6.53
7.06
7.51
7.30
7.52
8.39
8.08
7.83
3.43
2.69
1.54
1.68
-0.25
0.67
0.93
3.16
1.18
1.59
3.13
0.99
0.93
ortho-R
para-R
ortho-â
para-â
ortho-γ
ortho-γ′
para-γ
ortho-δ
ortho-δ′
para-δ
R-CH
R-CH3
R-CH3′
â-CH
â-CH3
â-CH3′
γ-CH
γ-CH3
γ-CH3′
δ-CH
δ-CH3
δ-CH3′
The 1H phase-sensitive NOESY16 for 4 at ambient
temperature reveals a slow exchange process in which
the halves of the MeO-BIPHEP ligand are exchanged
(see Figure 2). Since the isomerization product has
exactly the same structure, one observes only one set
of resonances. Interestingly, there is no exchange
a
Chemical shifts in ppm, relative to TMS. 7 ) MeO.
protonated 13C resonances at 74.5 ppm, as a strong
doublet, and 95.1 ppm, as a very weak triplet, for which
we had, as yet, no satisfactory explanation. A long-
range 13C,1H correlation revealed connectivity between
both of these nonprotonated carbons and the proton
ortho to the P atom.
-
involving any of the η5-C8H11 protons; i.e., the allyl
protons do not exchange among themselves and the CH2
protons do not exchange with the allyl protons, so that
we can exclude a process involving sequential migra-
tion of H+(or H-) during the isomerization. Presum-
ably, the biaryl double bond dissociates, thus making
room for its counterpart in the second biaryl ring;
however, this, by itself, does not rationalize our obser-
vations. A mechanism which contains both an η5-C8H11
“rotation”17 by 180° plus a switch in biaryl olefin
donation satisfies our observations, e.g. eq 3. The
Further, the biphenyl proton ortho to the methoxy group
correlated with the weak triplet signal at 95.1 ppm, and
we show these connectivities in the fragment above. The
13C signals for C(1′) (139.7 ppm) and C(6′) (135.4 ppm)
are at higher frequency. Given these assignments (see
Table 2 for details), we conclude that the C(1)-C(6)
biaryl double bond is coordinated to the metal, thereby
affording an 18e coordinatively saturated complex and
thus making the ligand 1a a six-electron donor to the
metal. Consistent with this bonding mode we note that
the signals for the carbons ortho to the methoxy groups,
at 102.3 and 112.7 ppm, are relatively far apart,
suggestive of two different types of biaryl rings. The
low-frequency 31P signal at -11.2 ppm is associated with
the unexpected coordination mode.
flexibility of coordinated 1a is noteworthy in that its
(15) Pathak, D. D.; Adams, H.; Bailey, N. A.; King, P. J .; White, C.
J . Organomet. Chem. 1994, 479, 237.
(16) For applications of 2-D exchange spectroscopy see: Barbaro,
P.; Currao, A.; Herrmann, J .; Nesper, R.; Pregosin, P. S.; Salzmann,
R. Organometallics 1996, 15, 1879. Barbaro, P.; Pregosin, P. S.;
Salzmann, R.; Albinati, A.; Kunz, R. W. Organometallics 1995, 14,
5160. Herrmann, J .; Pregosin, P. S.; Salzmann, R.; Albinati, A.
Organometallics 1995, 14, 3311. Pregosin, P. S.; Salzmann, R.; Togni,
A. Organometallics 1995, 14, 842. Breutel, C.; Pregosin, P. S.; Salz-
mann, R.; Togni, A. J . Am. Chem. Soc. 1994, 116, 4067. Ru¨egger, H.;
Pregosin, P. S. Magn. Reson. Chem. 1994, 32, 297. Lianza, F.;
Macchioni, A.; Pregosin, P. S.; Ru¨egger, H. Inorg. Chem. 1994, 33, 4999.
(17) “Rotation” is used to convey an image; there may be an η3-π-
allyl intermediate. Moreover, one could also imagine that the BIPHEP,
species 1a dissociates the double bond and a phosphorus donor to afford
a 14-electron complex which affects the necessary transformation
without any η5-C8H11 isomerization (we thank Prof. A. Togni for calling
our attention to this possibility); however, this is, to our knowledge,
unprecedented, whereas there are examples of η5-C8H11 to η3-C8H11
transformation.10,18,19
By coincidence, we recently14 recorded the 13C NMR
spectrum for the dinuclear tungsten-palladium com-
plex 5 (X ) Cl, and related derivatives). The observed
(14) Macchioni, A.; Pregosin, P. S.; Engel, P. F.; Mecking, S.; Pfeffer,
M.; Daran, J .; Vaissermann, J . Organometallics 1995, 14, 1637.

540 Organometallics, Vol. 16, No. 4, 1997
Feiken et al.
F igu r e 3. ORTEP plot for the cation of 6. Note that the
exo proton of the central CH2 group is situated over the
η5-C8H11 π-system.
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 6
Ru-P(1)
2.368(2)
2.299(5)
2.235(6)
2.173(5)
2.174(6)
1.401(9)
1.417(9)
1.504(10)
1.479(9)
1.453(7)
Ru-P(2)
2.339(1)
2.366(5)
2.200(6)
2.244(6)
1.416(9)
1.425(10)
1.504(9)
1.486(10)
1.359(6)
1.354(6)
Ru-C(1)
Ru-C(2)
Ru-C(27)
Ru-C(32)
Ru-C(34)
C(31)-C(32)
C(33)-C(34)
C(28)-C(29)
C(30)-C(31)
C(1)-C(2)
Ru-C(31)
Ru-C(33)
C(27)-C(34)
C(32)-C(33)
C(27)-C(28)
C(29)-C(30)
O(1)-C(3)
O(2)-C(13)
F igu r e 2. Aromatic section of the 2-D NOESY for 4
showing the exchange cross-peaks. The “open” cross-peaks
arise from NOE and the filled-in cross-peaks from ex-
change. There are two exchange processes. The halves of
the ligand 1a are in equilibrium; i.e., cross-peak A indicates
the exchange between 3 and 7, plus exchange of the
nonequivalent ortho protons of the di-tert-butylphenyl
rings, as shown by cross-peak B (300 MHz, CD2Cl2; room
temperature, mixing time 0.6 s).
P(1)-Ru-P(2)
P(1)-Ru-C(2)
P(2)-Ru-C(2)
Ru-P(1)-C(1)
Ru-P(1)-C(15)
96.9(1)
71.0(1)
80.7(1)
65.4(2)
114.8(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
45.2(1)
107.8(1)
Ru-P(2)-C(9)
Ru-P(1)-C(18)
104.4(2)
135.4(2)
X-r a y Str u ctu r e of 6. The isopropyl analog [Ru(η5-
C8H11)(1b)]CF3CO2 (6) could be prepared by starting
from [Ru(CF3CO2)2(1,5-COD)]2:
ability to act as a 6e donor might well help it stabilize
reactive intermediates. Equally important, in this con-
nection, is the relative ease with which 1a can resume
its “normal” bis(phosphine) coordination mode via double-
bond dissociation.
0.5[Ru(CF3CO2)2(1,5-COD)]2 + 1b f
[Ru(η5-C8H11)(1b)]CF3CO2
+ CF3CO2H (4)
6
We observe a second type of relatively slow dynamic
process occurring simultaneously at room temperature.
This involves restricted rotation around the P-C(ipso)
bonds for two of the four 3,5-disubstituted tert-butylphe-
nyl rings:
Suitable crystals could be obtained from CHCl3/EtOH/
pentane solution, and the solid-state structure was
determined by X-ray diffraction methods. An ORTEP
plot for the cation is shown in Figure 3. Table 3
contains a list of selected bond lengths and bond angles,
whereas Table 4 shows experimental parameters for the
structure determination. A molecule of CF3CO2H coc-
rystallizes with the complex.
The immediate coordination sphere consists of the two
P atoms, the biaryl double bond, C(1)-C(2), and the η5-
-
pentadienyl moiety of the C8H11 ligand. Of the two
These four nonequivalent ortho protons are, naturally,
also involved in the exchange mentioned above, in that
we observe cross-peaks linking these spins to the two
sets of equivalent ortho protons. All eight ortho protons
are nonequivalent at 193 K, the temperature for which
the assignments are reported. Although this type of
restricted rotation is rare, we have noted it previously
in the complex [RuH(p-cymene)(1a )]BF4.6
Ru-P separations, Ru-P(1) ) 2.368(2) Å and Ru-P(2)
) 2.339(1) Å, the Ru-P(1) adjacent to the coordinated
double bond is (a) longer than Ru-P(2) and (b) signifi-
cantly longer than that found by Pathak et al. (2.332-
(3)Å) in [Ru(Cp)(BINAP)]CF3SO3.15 The two biaryl
Ru-C distances, Ru-C(1) ) 2.299(5) Å and Ru-C(2)
) 2.366(5) Å, are also relatively long when compared
to both (a) conventional Ru-C bond lengths in

MeO-BIPHEP as a Six-Electron Donor in Ru Cations
Organometallics, Vol. 16, No. 4, 1997 541
Ta ble 4. Cr ysta l Da ta for Com p ou n d 6
the biphenyl proton ortho to the P atom. The figure also
reveals that the proton ortho to the methoxy group
(sharp doublet at ca. 6.25 ppm) correlates with the
coordinated biaryl carbon at 95.9 ppm. Figure 4 rep-
resents a rare example of the use of a 2-D long-range
13C,1H correlation to find an extremely weak 13C reso-
nance. The conventional 13C spectrum for 6 does not
provide convincing evidence for the existence of a signal
at 95.9 ppm.23 Given all of these NMR data, we
conclude that coordinated 1b is also a six-electron donor
in solution for 6.
formula
fw
C38H52F6O6P2Ru
881.83
cryst syst
space group
a, Å
orthorhombic
P212121 (No. 19)
11.771(4)
16.221(5)
20.783(5)
3968(2)
b, Å
c, Å
V, Å3
Z
4
F
calcd, g cm-3
F(000)
1.476
1824
0.0417, 0.0566
a
residual R, Rw
Surprisingly, 6 also shows two low-frequency protons.
One of these arises from the cyclooctadienyl exo-CH
positioned over the η5 moiety, as mentioned above. The
second stems from one of the four Pri methine reso-
nances.
a
R ) ∑(|Fo| - |Fc|)/∑|Fo|; Rw ) ∑(w1/2(|Fo| - |Fc|)/w1/2(|Fo|).
Ru-arene,18-20 Ru-olefin,21 or Ru-butadienyl22 com-
pounds (ca. 2.10-2.30 Å) and (b) the analogous binaph-
thyl carbons in [Ru(Cp)(BINAP)]CF3SO3 (2.258(7) and
2.281(9) Å). These long Ru-C(1) and Ru-C(2) bond
lengths are consistent with a weak interaction.
The C-C separations (Å) within the coordinated
biaryl ring suggest localized double bonds:
The positioning of the η5-C8H11- group relative to the
P-Ru-P plane (A vs B) represents a subtle structural
problem. The X-ray results clearly show that A is
The corresponding values for the second biaryl ring
involving carbons C(8)-C(13) are all much closer in
value and lie in the range ca. 1.38(1)-1.41(1) Å. Both
biaryl rings are perfectly flat.
The angle between the planes of the two biaryl rings
is 104.6°. This angle is understandable in that the ring
with the coordinated double bond is rotated toward the
ruthenium, so as to facilitate complexation. There is
an unexpected distortion in that the angle between the
lines formed by C(2)-C(5) and C(8)-C(11) might be
expected to be ca. 0°. In 6, this angle is 32° and
presumably arises due to the strained complexation
mode of this BIPHEP ligand.
correct in the solid state. In solution, one should
observe NOE’s from the isopropyl methine protons
(shown as CH in the fragments below) to the endo C(14)
-
and C(16) CH2 protons of the η5-C8H11 ligand:
The coordinated η5-C8H11- ligand has Ru-C separa-
tions in the range 2.173(5)-2.244(6) Å and C-C dis-
tances within the η5 moiety of 1.401(9)-1.425(10) Å, in
keeping with literature expectations.10,12,18 One of the
CH2 protons lies above the π-system of the coordinated
hydrocarbon. We note that the linkages from the
methoxy oxygen atoms to the ring carbons, O(1)-C(3)
) 1.359(6) Å and O(2)-C(13) ) 1.354(6) Å, are es-
sentially identical.
If the A structure is correct, there will be NOE’s from
endo-14 (and endo-16) to the δ and γ CH’s . If B is
correct, then there will be NOE’s from endo-14 to R and
â and from endo-16 to δ and γ. Unfortunately, the endo
protons are poorly resolved and resonate close to some
of the CH methines, so that the “normal” NOESY was
ambiguous. However, a ROESY measurement, com-
bined with Hartmann-Hahn transfer24-26 of the NOE
NMR Stu d ies on [Ru (η5-C8H11)(1b)]CF 3CO2 (6).
In many ways the NMR characteristics for 6 are similar
to those for 4. The two 31P resonances are widely
dispersed, 70.9 and 8.9 ppm (although less so than for
-
4), and the five 13CH absorptions from the η5-C8H11
ligand fall in the range 49.6-114.3 ppm.
The long-range 13C,1H correlation (see Figure 4),
again reveals connectivity between the two nonproto-
nated coordinated carbons at 76.4 and 95.9 ppm and
(23) It is not suprising that the coordinated biphenyl carbon C(1)
observed at ca. 95 ppm is very weak in intensity. It has no close-by
proton to facilitate relaxation, and it will be split by both 31P spins.
The analogous C(6) 13C signal for [Ru(Cp)(BINAP)]CF3SO3 was not
observed (personal communication from C. White). The 13C spin directly
attached to phosphorus, ca. 75 ppm, has a proton neighbor. We have
observed the expected doublet for C(6) in both 4 and 6.
(24) Pregosin, P. S.; Ru¨egger, H. Magn. Reson. Chem. 1994, 32, 297.
(25) Neuhaus, D.; Keeler, J . J . Magn. Reson. 1986, 68, 568.
(26) Cavanagh, J .; Keeler, J . J . Magn. Reson. 1988, 80, 186.
(18) Ashworth, T. V.; Chalmers, A. A.; Liles, D. C.; Meintjies, E.;
Singleton, E. Organometallics 1987, 6, 1543.
(19) Bennett, M. A.; Matheson, T. W.; Robertson, G. B.; Smith, A.
K.; Tucker, P. A. Inorg. Chem. 1981, 20, 2353.
(20) Yamamoto, Y.; Sato, R.; Matsuo, F.; Sudoh, C.; Igoshi, T. Inorg.
Chem. 1996, 35, 2329.
(21) Faller, J . W.; Chase, K. J . Organometallics 1995, 14, 1592.
(22) Brisdon, B. J .; Walton, R. A. Polyhedron 1995, 14, 1259.

542 Organometallics, Vol. 16, No. 4, 1997
Feiken et al.
F igu r e 4. Section of the long-range 13C,1H correlation (500
MHz, CD2Cl2, room temperature, optimized for J ) 8.3 Hz,
magnitude spectrum) for 6 showing the key cross-peaks
which link the resonances for the coordinated biaryl carbon
to several of the biaryl proton resonances, via 2J (13C,1H)
and, more importantly, 3J (13C,1H). The intense signal in
the 13C direction stems from one of the five η5-C8H11
pentadienyl carbons.
F igu r e 5. (a, top) Section of the NOESY spectrum of 6
(300 MHz, CD2Cl2, room temperature, mixing time 0.8 s)
showing no cross-peaks from the Pri methines to the two
exo protons. This is as expected. (b, bottom) ROESY/
Hartmann-Hahn spectrum of 6 (500 MHz, CD2Cl2, room
temperature, spinlock 0.4 s, carrier frequency at 1.75 ppm),
in which the magnetization is transferred selectively from
the δ- and γ-CH’s to the endo resonances (not seen) and
then again to the exo spins, as shown (see text).
from the endo protons to their corresponding exo protons
(which are well-resolved), clarified the question and
revealed A to be correct (see Figure 5). The NOE
spectrum is shown in the top trace and the ROESY/
Hartmann-Hahn spectrum in the lower trace. The
magnetization is transferred selectively from the δ- and
γ-CH’s to the endo resonances via ROE (not seen) and
then again, via Hartmann-Hahn, to the exo-14 and exo-
16 spins, as shown.
recorded with a Bruker DPX-300 spectrometer. 19F (188.3
MHz) NMR spectra were recorded with a Bruker AC200
spectrometer. The two-dimensional studies were carried out
at 500 MHz for 1H. Chemical shifts are given in ppm, and
coupling constants (J ) are given in Hz. The ROESY/Hart-
mann-Hahn spectrum (500 MHz, CD2Cl2) was measured at
room temperature, with a 0.4 s spinlock and the carrier
frequency set at 1.75 ppm. IR spectra were recorded with a
Perkin-Elmer 882 infrared spectrophotometer. Elemental
analyses and mass spectroscopic studies were performed both
at ETHZ and by the Analytical Research Services at Hoff-
manLa Roche.
In contrast to the case for 4 the 2-D NOESY for 6
shows no exchange at ambient temperature.
Con clu sion s
We have shown that the ligands 1 can function as 6e
donors to Ru(II) via an unexpected coordination of one
of the biaryl double bonds. This mode of bonding might
contribute to the capability of BIPHEP and BINAP type
ligands to stabilize otherwise reactive species. Although
the 31P NMR characteristics for this new η4-bonding
mode have empirical value, the 13C chemical shifts for
the two biaryl carbons in question are a more reliable
criterion.
X-r a y Str u ctu r e An a lysis of [Ru (η5-C8H11){(R)-1b)}]-
CF 3COO‚CF 3COOH, 6. Crystallographic data are collected
in Table 4. Orange-brown crystals (0.25 × 0.4 × 0.8 mm)
suitable for X-ray determination were grown by slow diffusion
of pentane into a CHCl3/EtOH solution of 6. Geometry and
intensity data were collected at 233 K on a Siemens R3m/V
diffractometer equipped with a graphite monochromator using
Mo KR (0.710 73 Å) radiation. Unit cell parameters were
determined from the least-squares refinement of a set of 20
centered reflections. Two standard reflections were monitored
periodically; they showed no change during data collection.
Data were collected using the ω-scan mode with a ω-scan width
of 0.50° and ω-scan speed of 1.50-19.53° min-1; 5362 reflec-
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All reactions were performed
under an atmosphere of Ar using standard Schlenk techniques.
Dry and oxygen-free solvents were used. Ru(OAc)2(1a ), 2 was
provided by F. Hoffman La Roche, Basel, Switzerland. Routine
1H (300.13 MHz) and 31P (121.5 MHz) NMR spectra were

MeO-BIPHEP as a Six-Electron Donor in Ru Cations
Organometallics, Vol. 16, No. 4, 1997 543
tions were measured (index ranges 0 e h e 15, 0 e k e 21, 0
e l e 27), 4716 of which were unique with F > 5.0σ(F). The
selected crystal had the linear absorption coefficient µ(Mo KR)
in vacuo afforded an orange powder in 87% yield. MS (FAB):
m/e found 1239.7 (M+), calcd 1240.8. IR (cm-1, KBr): 1587,
1512 (η5-C8H11; m, sh), 1150-1000 (BF4-; s, br). 31P NMR
(CD2Cl2, 298 K): 69.3 (d, 47) and -9.6 ppm (d, 47). 19F NMR
(CD2Cl2, 298 K): -153.7 (s, 25%, BF4-) and -153.8 ppm (s,
75%, BF4-). Anal. Calcd for C78H107BF4O2P2Ru: C, 70.62; H,
8.14. Found: C, 69.86; H, 7.94.
[Ru (η5-C8H11){(R)-1b}]CF 3COO‚CF 3COOH (6). To a so-
lution of (R)-Pri-MeOBIPHEP (1b; 1.51 g, 3.36 mmol) in 15
mL of THF was added [Ru(CF3COO)2(1,5-COD)]2 (1.62 g, 1.85
mmol). After 6 h at 40 °C the yellow-brown reaction mixture
was evaporated to dryness. The residue was stirred vigorously
with pentane (4 × 10 mL) and redissolved in 3 mL of CH2Cl2.
Slow addition of 20 mL of pentane yielded an orange-brown
powder (2.64 g) in 89% yield. MS (electrospray): m/e found
655.5 (M+), calcd 654.8. IR (cm-1): 1587, 1518, (sharp, η5-
C8H11), 1698, 1140 (CF3COO-, br), 1782, 1189 (CF3COOH, br).
31P NMR (CDCl3, 298 K): 70.8 (d, 40) and 9.2 ppm (d, 40). 19F
NMR (CDCl3, 298 K): 75.96 ppm (s). Anal. Calcd for
) 0.55 mm-1
.
The structure was determined by direct
methods and subsequent Fourier maps. Full-matrix least-
squares refinement was employed with all non-hydrogen atoms
anisotropic and hydrogens in calculated positions. The weight-
2
ing scheme w ) 1/σ2(Fo) + 0.001|Fo| gave satisfactory agree-
ment analyses. Final R and Rw values are 0.0417 and 0.0566,
respectively: goodness of fit 1.41, maximum ∆/σ 0.14, largest
difference peak 0.90 e Å-3, largest difference hole -0.46 e Å-3
,
data-to-parameter ratio 9.8:1. Data collection, cell refinement,
data reduction, structure solution, structure refinement, mo-
lecular graphics and preparation of material for publication
used SHELXTL PLUS (VMS).27
[Ru (OAc)2{(R)-1a }] (2a ). To a solution of 1a (4.99 g, 4.83
mmol) in 100 mL of toluene was added [Ru(OAc)2(p-cymene)]
(1.75 g, 4.95 mmol). After 96 h at 100 °C the reaction mixture
was evaporated to dryness, the residue was dissolved in 70
mL of hexane, and this solution was then filtered over Celite.
Concentration of the filtrates to ca. 20 mL and cooling to -20
°C for 1 h yielded a yellow-brown powder (5.12 g) in 85% yield.
C
38H52F6O6P2Ru: C, 51.76; H, 5.94; P, 7.02. Found: C, 51.24;
H, 5.95; P, 6.80.
MS (EI): m/e found 1250.5 (M+), calcd 1250.6. IR (cm-1
,
Ack n ow led gm en t. P.S.P. thanks the Swiss Na-
tional Science Foundation, the ETH Zurich, and F.
Hoffmann-La Roche AG for financial support. We also
thank F. Hoffmann-La Roche AG for a gift of BIPHEP
ligands and the complex Ru(OAc)2(1a ), as well as
J ohnson Matthey for the loan of precious metals. We
especially thank P. Scho¨nholzer and Dr. M. Hennig for
the X-ray structure determination of 6 and Ms. E.
Hoermann for excellent experimental assistance.
KBr): 1587, 1412 (COO; shoulder), 1455 (P-aryl; shoulder).
31P{1H} NMR (CDCl3, 298 K): 68.3 ppm (s). Anal. Calcd for
C
75H102O6P2Ru: C, 71.07; H, 8.22; P, 4.95. Found: C, 71.06;
H, 7.96; P, 4.78.
Syn th esis of [Ru (η5-C8H11){(R)-1a }][BF 4] (4). To a solu-
tion of Ru(OAc)2(1a ) (189 mg, 0.151 mmol) in 4 mL of CH2Cl2
was added 10 equiv of 1,5-COD (185 µL, 1.5 mmol). After 5
min 2.1 equiv of HBF4‚Et2O (0.32 mmol, 43 µL of a 7.3 M
solution in diethyl ether) was added. After 4 h the reaction
mixture was evaporated to dryness; the residue was washed
twice with 3 mL of hexane and then redissolved in 4 mL of
CH2Cl2. After washing with water (3 × 4 mL) and drying over
MgSO4, the solution was filtered over Celite and evaporated
to dryness. Washing twice with 2 mL of hexane and drying
Su p p or tin g In for m a tion Ava ila ble: Tables of bond
lengths and angles, complete atomic coordinates, anisotropic
displacement coefficients, and isotropic displacement coef-
ficients for hydrogen atoms for 6 (9 pages). Ordering informa-
tion is given on any current masthead page.
(27) Sheldrick, G. M. SHELXTL PLUS; Siemens Analytical X-ray
Instruments, Inc., Madison, WI, 1990.
OM960812X