Selective dynamics of [Rh(1,5-COD)(bidentate)]BF4 complexes via NMR exchange spectroscopy

Article abstract of DOI:10.1016/S0022-328X(99)00329-0

NMR exchange measurements on [Rh(1,5-COD)(bidentate)]BF₄ complexes (bidentate = chiral bis-phosphine, a P,N-phosphino-oxazoline, a P,S-phosphito-thioether and a bis-pyrazolylborate) show selective 1,5-COD dynamics which can be superficially attributed to olefin rotation. It is suggested that the mechanism actually involves: (i) M-L¹ bond breaking (L¹ = N or S-donor); (ii) isomerization of the T-shaped species; (iii) rotation around the remaining M-L² bond and (iv) recomplexation. The solid state structures of the two compounds [M(1,5-COD)(10)]BF₄, M = Rh, Ir and 10=(S,R)-2-[4-(isopropyl)oxazol-2-yl]-2′-diphenylphosphino-1,1′- binaphthyl, were determined by X-ray diffraction methods.

Full text of DOI:10.1016/S0022-328X(99)00329-0

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Journal of Organometallic Chemistry 587 (1999) 244–251
Selective dynamics of [Rh(1,5-COD)(bidentate)]BF4 complexes via
NMR exchange spectroscopy
Massimiliano Valentini, Kumaravel Selvakumar, Michael Wo¨rle, Paul S. Pregosin *
Laboratory of Inorganic Chemistry, ETH Zentrum, CH-8092 Zurich, Switzerland
Received 15 March 1999
Abstract
NMR exchange measurements on [Rh(1,5-COD)(bidentate)]BF4 complexes (bidentate=chiral bis-phosphine, a P,N-phosphino-
oxazoline, a P,S-phosphito-thioether and a bis-pyrazolylborate) show selective 1,5-COD dynamics which can be superficially
attributed to olefin rotation. It is suggested that the mechanism actually involves: (i) MꢀL1 bond breaking (L1=N or S-donor);
(ii) isomerization of the T-shaped species; (iii) rotation around the remaining MꢀL2 bond and (iv) recomplexation. The solid state
structures of the two compounds [M(1,5-COD)(10)]BF4, M=Rh, Ir and 10=(S,R)-2-[4-(isopropyl)oxazol-2-yl]-2%-diphenylphos-
phino-1,1%-binaphthyl, were determined by X-ray diffraction methods. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: [Rh(1,5-COD)(bidentate)]+; 2 D-Exchange NMR; X-ray diffraction
The P,N-complexes 2 [14] and 3 [15] are also dynamic
in solution and these molecules are thought to show
dynamic behaviour that arises via nitrogen dissociation.
1. Introduction
Four-coordinate cationic olefin (and especially 1,5-
COD) tertiary-phosphine complexes of Rh(I) are com-
monly used precursors in homogeneous catalytic
hydrogenation [1–6]. The 13C-NMR characteristics of
these species have been routinely registered over the
years as models for metalꢀolefin bonding [7], and there
are numerous X-ray diffraction studies on these com-
pounds [6,8–15]. However, little attention has been
given to the solution dynamics of this class of cationic
olefin compounds. Chaloner and co-workers [13] have
reported stereochemical non-rigidity in the ferrocene
cation 1; however they attribute this to changes in the
phosphine chelate ring conformation.
We have recently reported the synthesis of the Rh(I)
complexes 4 [16] (a dinuclear species which contains
two PO, PN bidentate ligands) and the exo-norborneol
thioether complex 5 [17].
* Corresponding author. Tel.: +41-1-632291; fax: +41-1-6321090.
E-mail address: pregosin@inorg.chem.ethz.ch (P.S. Pregosin)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00329-0

M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
245
coordination plane of the Rh(I) complex, whereas Fig.
2 shows the Ir(I) complex from behind the 1,5-COD.
The two structures are remarkably similar. The metal
atom is found in a distorted square-planar environment
and the 1,5-COD ligand is significantly rotated with
respect to the N(1)ꢀMꢀP(3) plane, e.g. the angles
P(3)ꢀMꢀC(43), 148.3(2)°, 146.4(2)° and P(3)ꢀMꢀC(44),
175.4(2)° and 176.6(2)° are quite different (the double
bond C(39)ꢀC(40) is trans to N and C(43)ꢀC(44) trans
to P). The coordination bond lengths and remaining bond
angles are in keeping with the literature [6,8–18], although
it is noteworthy that 15a and 15b both show N(1)ꢀMꢀP(3)
angles several degrees below 90°. Binap complexes have
PꢀMꢀP angles \90° [10,19,20]. The complexed double
bonds show CꢀC bond distances which are consistent with
the idea that (i) there is p-back bonding from the metal
to the olefin and (ii) Ir(I) is somewhat electron richer than
Rh(I). As in the two previous structures of this ligand [21],
theoxazolineringisca. perpendiculartotheN(1)ꢀMꢀP(3)
plane and this is best seen in Fig. 2. The PꢀIrꢀN plane
is shown as almost horizontal and the O(1)ꢀCꢀN(1) plane
of the oxazoline can be clearly seen to be forced away
from the former plane.
Both of these compounds show slow and selective
exchange of the olefinic protons 1 and 2, with 5 and 6,
respectively, i.e. apparent rotation of the 1,5-COD
chelate. This type of olefin exchange selectivity has also
been observed [18] for the olefinic protons of the chiral
cation [Rh(norbornadiene)(6)]+.
2.2. NMR spectroscopy for the complexes
1
Table 2 gives a selection of H-, 13C-, and 31P-NMR
data for the 1,5-COD complexes, and includes
It seemed of interest to determine whether similar
molecular dynamics are observable in a wider variety of
chelating cationic 1,5-COD complexes. To this end we
have used the chelating ligands 7–11, to prepare the
compounds [Rh(1,5-COD)(7–11)]BF4, 12–16, as shown
in Scheme 1, and studied their solution characteristics
using NMR exchange spectroscopy.
2. Results
2.1. X-ray structures of 15a,b
The preparation of the Rh(I) (and one Ir(I)) 1,5-COD
complexes followed standard literature procedures. As
auxiliary 10 is relatively new we have grown crystals of
the Rh(I) and Ir(I) P,N-complexes, 15a,b, and determined
their structures via X-ray diffraction. Figs. 1 and 2 show
views for these Rh(I) and Ir(I) cations and Table 1 gives
selected bond angles and bond lengths for these com-
pounds. Fig. 1 provides a view from above the PꢀRhꢀN
Scheme 1. Ligands and their Rh(1,5-COD) complexes as BF4 salts.

246
M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
Table 1
,
Selected bond lengths (A) and bond angles (°) for the cations 15a and
15b a
15a (Rh)
15b (Ir)
MꢀP(3)
MꢀN(1)
2.3103(12)
2.170(4)
2.106(6)
2.146(5)
2.182(6)
2.229(5)
1.270(6)
1.340(6)
1.363(9)
1.376(10)
2.3029(9)
2.151(3)
2.109(4)
2.142(4)
2.156(4)
2.206(4)
1.274(5)
1.339(5)
1.399(7)
1.383(8)
MꢀC(39)
MꢀC(40)
MꢀC(43)
MꢀC(44)
C(1)ꢀN(1)
C(1)ꢀO(1)
C(39)ꢀC(40)
C(43)ꢀC(44)
N(1)ꢀMꢀP3
86.53(11)
97.51(18)
91.89(16)
148.3(2)
175.4(2)
152.0(2)
170.6(2)
94.3(2)
86.62(9)
97.68(13)
92.21(12)
146.4(2)
176.6(2)
150.7(2)
171.0(2)
95.0(2)
P(3)ꢀMꢀC(39)
P(3)ꢀMꢀC(40)
P(3)ꢀMꢀC(43)
P(3)ꢀMꢀC(44)
N(1)ꢀMꢀC(39)
N(1)ꢀMꢀC(40)
N(1)ꢀMꢀC(43)
N(1)ꢀMꢀC(44)
Fig. 1. View of the cation of the rhodium P,N 1,5-COD complex 15a.
93.5(2)
92.6(2)
1J(103Rh,13C, olefin) values which fall in the range 5–13
Hz. The usual NOESY, CꢀH and PꢀH methods were
used to make the necessary assignments [22,23]. The
two bis-phosphine cations, [Rh(1,5-COD)(7)]+ (12) and
[Rh(1,5-COD)(8)]+ (13), and the pyrazolyl borate
a C(39)ꢀC(40) trans to N; C(43)ꢀC(44) trans to P.
analog, 14 were prepared in order to have complexes
with the same two donor atoms.
For the ferrocene phosphine complex 12, NOE spec-
troscopy, using the o-phenyl PPh2 and the PCy2
aliphatic protons, allows the four non-equivalent 1,5-
COD olefinic protons and carbons 1,2 and 5,6 to be
assigned. Exchange spectroscopy [24] on this bis-phos-
phine compound reveals no olefin exchange at ambient
temperature. Complex 12 contains relatively good P-
donors, as evidenced by the observed relatively high-
frequency 13C chemical shifts of the olefin carbons (i.e.
the chelating phosphine has the expected trans influ-
ence). Assuming ‘olefin rotation’ to be the mechanism
for the dynamics noted above, it is not obvious why it
should be suppressed in 12. In the MeOꢀBiphep com-
plex 13, the two non-equivalent 1,5-COD olefinic reso-
nances arise due to the axial and equatorial orientation
of the P-phenyl substituents. Complex 13 is not ex-
pected to show exchange due to ‘rotation’ but is a
useful compound in that its 2 D spectrum confirms that
no other exchange is observed.
On the other hand, the pyrazolyl-borate, 14, P,N, 15
and P,S-chelate complexes, 16, all show the selective
olefin exchange noted above for 4–6 (protons 1 and 2,
with
5
and 6, respectively), although routine
1J(103Rh,13C, olefin) values are observed. Fig. 3 shows
1
sections of the H-NMR exchange spectra for 15a (top)
and 16 (bottom). In both of these, there are two
relatively high-frequency absorptions (olefin protons
trans to P), which are in selective slow exchange with
Fig. 2. View of the cation of the iridium P,N 1,5-COD complex 15b.

M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
247
two lower frequency signals. The bis pyrazolyl-borate
derivative 14 (Fig. 4), shows two COD olefin environ-
ments, 1 and 6 on one side of the NꢀRhꢀN plane and
2 and 5 on the other (see 17). Its 2 D exchange
spectrum is especially clear in that the pairwise ex-
change of both olefinic and aliphatic resonances is
clearly observed. These dynamics exchange the two
olefin (or methylene groups) on the side of the BꢀPh
with the two on the side of the BꢀMe.
fragment) is expected to be relatively slow. We have no
direct evidence for MꢀL1 bond breaking; however, a
mechanism related to ours has been postulated in
Pdꢀallyl chemistry (i.e. allyl rotation is not proposed)
[22,25].
With the chelating bis-phosphines, 12 and 13, con-
taining two relatively strong donors, RhꢀP dissociation
is less likely, and thus the dynamics are not observed.
1,5-COD olefin rotation, which would involve breaking
two bonds simultaneously, is excluded based on the
observations of the bis-phosphine complexes. It is al-
ways possible that a five-coordinate species is responsi-
ble for the observed dynamics. The fifth ligand might
come from the BF4 anion; however, traces of water
must also be considered. To this end we have added
more than a 10-fold excess of water to the previously
recorded solution of 14 and remeasured the exchange
spectrum. The result is unchanged within the experi-
mental error, i.e. a significant increase in the concentra-
tion of water does not accelerate (or hinder) the
exchange dynamics. As one expects the water to
solvolyse the BF4 anion, this result also represents
indirect evidence that the BF4− is not involved.
3. Discussion
For several of the complexes inverse spectroscopy via
the olefinic proton resonances was employed to obtain
the rhodium-103 chemical shifts and, for 16, this result
is shown in Fig. 5. It is interesting to note that there are
very strong cross-peaks arising from all four SCH2
resonances (in addition to cross-peaks from the COD
protons). Our experience [17] suggests that the three-
bond RhꢀSꢀCꢀH interactions can be \2 Hz, so that,
generally speaking, 103Rh-chemical shifts in thioether
complexes might well be easily accessible. Since the
dynamics noted above are relatively slow (estimated to
be B0.5/s), and the spin-spin coupling to 103Rh in 16
relatively large, RhꢀS bond breaking (the first step in
Since very different complexes such as 4 and 5
(amongst others) as well as 14–16 reveal related 1,5-
COD dynamics, the chemistry involved has some gener-
ality. We attribute these results to a mechanism whose
first step involves RhꢀL1 bond breaking (L1=N or S
donor) to form a three-coordinate species (see Scheme
2). Rearrangement of the T-shape three-coordinate
formed is followed by rotation around the remaining
Pꢀ or NꢀRh bond. Recombination of the N (or S) L1
donor completes the mechanism. This sequence (and
especially step 3, the rotation of a large structural
Table 2
Selected olefin NMR data for the 1,5-COD complexes
a
l
12
13 b
14 c
4.47
4.47
3.61
3.61
15a d
15b e
16 f
5.74
5.95
5.10
3.67
(H-1)
(H-2)
(H-5)
(H-6)
5.56
5.36
4.32
3.32
4.81
5.12
5.05
3.13
3.30
5.22
4.42
2.97
3.06
4.50
4.81
4.50
(C-1)
(C-2)
(C-5)
(C-6)
97.6
93.3
95.8
98.0
102.8
98.0
78.0
99.1 (q)
97.6 (q)
82.5 (d)
77.4 (d)
89.7
82.4
72.8
62.4
113.6
78.0
80.2
80.2
116.5
92.1
86.6
101.2
102.8
(P)
21.4
25.7
–
21.7 (d)
18.5 (s)
137.6 (d)
53.5 a
a 1J(Rh,P), PCy2=150 Hz, 2J(P,P)=32 Hz, PPh2 resonance is broad.
b 1J(Rh,P)=146 Hz, 1J(Rh,C, olefin)=7.8 Hz.
c 1J(Rh,C, olefin)=ca. 13 Hz.
d 1J(Rh,C, olefin)=8.1, 8.7, 12.4 and 12.2 Hz for the 99.1, 97.6, 82.5 and 77.4 ppm signals, respectively.
e 2J(P,C)=10.7 and 15.0 Hz, respectively, for the 89.7 and 82.4 ppm signals.
f 1J(Rh,C, olefin)=5.0, 5.7, 10.1 and 9.2 Hz for the 116.5, 113.6, 92.1 and 86.6 ppm signals, respectively.

248
M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
Fig. 4. Section of the exchange spectrum for the N,N compound 14.
The exchange cross-peaks are indicated by rectangles. In this complex
the olefinic and aliphatic protons of the 1,5-COD are well resolved.
The four different aliphatic CH2 signals show pairwise exchange (400
MHz, CD2Cl2).
recorded with Bruker DPX-250, 300 and 400 MHz
spectrometers. Chemical shifts are given in ppm and
coupling constants (J) in Hz. The phase-sensitive two-
Fig. 3. Sections of the exchange spectrum for the P,N compound 15a
(top) and the P,S complex 16 (bottom). The exchange cross-peaks are
indicated by arrows. In each case there are four non-equivalent
1,5-COD olefinic protons (two at high frequency, trans to P and two
at low frequency, trans to either N or S), which are in selective
exchange (400 MHz, CD2Cl2).
1
dimensional H-NOESY and 31Pꢀ1H (and 13Cꢀ1H) cor-
relation experiments were carried out at 400 MHz
[22,23].
4.2. X-ray crystallographic studies
the suggested mechanism) is not in contradiction to the
observed cross-peaks due to the three-bond coupling.
In conclusion, several, but not all, of the Rh(1,5-
COD)(L1,L2 chelate)+ cations are dynamic, with the
NMR observations consistent with apparent rotation of
the 1,5-COD. However, we suggest that a different
mechanism involving RhꢀL1 bond breaking is opera-
tive, so that, taken together with molecules such as 2–5
a general mechanistic picture is slowly emerging.
Table 3 shows crystal data and structure refinement
parameters for 15a(Rh) and 15b(Ir). Intensity data for
both complexes were collected on a Siemens SMART
PLATFORM equipped with a CCD detector. An empiri-
cal absorption correction was performed with SADABS
[27]. The Bruker program package SHELXTL Version 5
[28] was used for the structure solution (direct meth-
4. Experimental
4.1. General
All manipulations were carried out under an argon
atmosphere. Diethyl ether was distilled from sodium-
benzophenone ketyl, CH2Cl2 from CaH2, and hexane
from sodium. (S,R)-2-[4-(Isopropyl)oxazol-2-yl]-2%-
diphenylphosphino-1,1%-binapthyl (10) was prepared as
reported earlier [21]. Ligand 11 has been prepared in
our laboratory and its synthesis and further chemistry
will be reported separately. [Rh(COD)2]BF4 and [Ir-
(COD)2]BF4 were prepared [26] from [Rh(COD)Cl]2
and [Ir(COD)Cl]2, respectively.
Routine 1H-, 13C- and 31P-NMR spectra were
Scheme 2.

M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
249
described with 1.5 carbon equivalents. All non-hydro-
gen atoms except the atoms belonging to the disordered
atoms were refined with anisotropic thermal displace-
ment parameters. All hydrogen atoms were placed at
calculated positions, and refined (riding model) with
different isotropic thermal displacement parameters for
each group.
4.2.1. Complex 15a
A solution of [Rh(COD)2]BF4 (20 mg, 0.05 mmol)
and ligand 10 (28 mg, 0.05 mmol) in CH2Cl2 (2 ml) was
stirred at room temperature (r.t.) for 2 h. The solvent
was evaporated i.v. and the residue was washed with
hexane. The complex (15a) obtained was recrystallised
from CH2Cl2ꢀether. Yield: 38 mg, 91%. MS (FAB): 760
(M+ꢀBF4−) (100), 652 [M+ꢀ(COD+BF4−)] (40). A
single crystal suitable for X-ray diffraction was ob-
tained by slow diffusion of ether into the CH2Cl2
solution. Anal. Calc. for C46H44NOBF4PRh (847.54):
C, 65.19; H, 5.23; N. 1.65. Found: C, 65.12; H, 5.32; N,
Fig. 5. Inverse 103Rh spectrum for 16 showing the numerous contacts
due to J(103Rh,1H) coupling. The separation of the two horizontal
cross-peaks represents the one-bond rhodiumꢀphosphorus coupling
constant. There are four strong cross-peaks in the region ca. 2.83–
3.48 ppm, stemming form the four non-equivalent SCH2 protons.
ods), structure refinement (full-matrix least-squares on
F2) and molecular graphics. In 15a the BF4 molecule is
disordered. Further, a disordered solvent (dichloro-
methane) molecule was found and described with 6.3
carbon equivalents per formula unit. Disorder of a part
of the solvent molecules was also found in 15b and
1
1.55. H-NMR (CD2Cl2, 298 K, 400 MHz): 5.12 (br,
2
3
H-1), 5.05 (br, H-2), 4.14 (dd, JHH=11.1, JHH=7.9,
2
3
cis CHO), 3.63 (t, JHH=11.0, JHH=9.3, trans CHO),
3.30 (br, H-6), 3.13 (br, H-5), 3.08 (m, CHN), 2.38 (m,
H-8), 2.22 (m, H-3), 2.06 (m, H-3% and H-8%), 1.94 (m,
Table 3
Crystal data and structure refinement for 15a(Rh) and 15b(Ir)
Identification code
15a(Rh)
15b(Ir)
Empirical formula
Formula weight
Temperature (K)
C46H44BF4NOPRh·CH2Cl2
932.44
293(2)
C46H44BF4NOPIr·0.5C4H10O·1.5C
991.88
233(2)
,
Wavelength (A)
0.71073
Orthorhombic
P212121
0.71073
Orthorhombic
P212121
Crystal system
Space group
Unit cell dimensions
,
a (A)
10.8193(16)
17.826(3)
23.002(4)
4436.3(12)
10.7634(16)
17.422(3)
23.516(4)
4409.8(11)
,
b (A)
,
c (A)
V (A )
3
,
Z
4
4
Dcalc. (Mg m−3
)
1.396
0.48
1912
0.58×0.36×0.30
1.45–26.40
1.494
3.119
1992
1.20×0.60×0.30
1.45–29.89
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm3)
Theta range for data collection (°)
Index ranges
Reflections collected
−135h513, −215k59, −275l527
23816
−95h515, −235k522, −325l531
32182
Independent reflections
Completeness
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
8813 [Rint=0.0342]
98.3% to theta=26.40°
Full-matrix least-squares on F2
8813/19/514
11382 [Rint=0.0411]
92.4% to theta=29.89°
Full-matrix least-squares on F2
11382/0/533
1.041
1.072
R1=0.0497, wR2=0.1223
R1=0.0703, wR2=0.1364
−0.05(3)
R1=0.0310, wR2=0.0737
R1=0.0358, wR2=0.0765
−0.014(5)
Absolute structure parameter
Largest difference peak and hole (e A
−3
,
)
0.726 and −0.515
0.786 and −1.173

250
M. Valentini et al. / Journal of Organometallic Chemistry 587 (1999) 244–251
CH-i-Pr and H-4), 1.71 (m, H-4%, H-7, and H-7%),
1.13 (d, 3JHH=6.8, Me), 0.87 (d, 3JHH=6.8, Me).
13C-NMR (CD2Cl2, 298 K, 400 MHz): 99.1 (q,
1JRhC=8.1, 2JPC=12.4, C-1), 97.6 (q, 1JRhC=8.7,
4.2.4. Complex 12
This ferrocene complex was prepared in a similar
manner to 16. From 20 mg of the [Rh(1,5-COD)2]BF4
and 30 mg of 7 were obtained 38 mg (86%) of the
product. Anal. Calc. for C44H56BF4P2FeRh (892.43): C,
59.22; H, 6.32. Found: C, 59.05; H, 6.39. MS (FAB):
1
2JPC=11.2, C-2), 82.5 (d, JRhC=12.4, C-5), 77.4 (d,
1JRhC=12.2, C-6), 72.3 (s, CHN), 71.9 (s, CHO), 32.2
(s, CH-i-Pr), 30.6 (s, C-4), 30.5 (s, C-7), 29.5 (s, C-8),
29.3 (s, C-3), 20.9 (s, Me), 15.7 (s, Me). 31P-NMR
805 (M+ꢀBF4−) (62.4), 695 (100). H-NMR (CD2Cl2,
1
298 K, 400 MHz): 5.56 (br, H-1), 5.36 (br, H-2), 4.32
(br, H-5), 3.86 (br, Cp), 3.32 (H-6), 2.43 (m, H-4 and
H-4%), 2.34 (m, H-3%), 2.20 (m, H-3), 1.79 (m, H-8), 1.77
(m, H-7 and H-7%), 1.28 (m, H-8%). 13C-NMR (CD2Cl2,
298 K, 400 MHz): 101.2 (s, C-6), 97.6 (s, C-1), 95.8 (s,
C-5), 93.3 (s, C-2), 71.8 (s, Cp). 31P-NMR (CD2Cl2, 298
K, 400 MHz): 53.5 (d, 1JRhP=150, PCy2), 21.4 (q,
1JRhP=149, 2JPP=32, Pph2). 103Rh-NMR (CD2Cl2,
1
(CD2Cl2, 298 K, 400 MHz): 21.7 (d, JRhP=147 Hz).
4.2.2. Complex 15b
This was prepared in similar manner to 15a using
[Ir(COD)2]BF4 (25 mg, 0.05 mmol). Yield: 45 mg,
95%. MS (FAB): 845 (M+ꢀBF4−) (100). Single crystal
suitable for X-ray diffraction was obtained from
CH2Cl2ꢀether. Anal. Calc. for C46H44NOBF4PIr
(936.86): C, 58.97; H, 4.73; N, 1.50. Found: C, 58.83;
1
1
298 K, 400 MHz): −229 (t, JRhP=150, JRhP=148).
H, 4.85; N, 1.53. 1H-NMR (CD2Cl2, 298 K, 400
4.2.5. Complex 14
2
MHz): 5.22 (br, H-1), 4.42 (br, H-2), 4.18 (t, JHH
=
This was kindly provided by Dr H. Ru¨egger [29].
1H-NMR (CD2Cl2, 298 K, 400 MHz): 4.47 (br, H-1
and H-2), 3.61 (br, H-5 and H-6), 2.48 (s, Me), 2.40
(m, H-8 and H-8%), 1.67 (m, H-4 and H-4%), 1.44 (m,
H-3 and H-3%), 1.25 (m, H-7 and H-7%), 0.43 (s, BꢀMe).
13C-NMR (CD2Cl2, 298 K, 400 MHz): 80.2 (8s, C-5
and C-6), 78.0 (s, C-1 and C-2), 30.4 (s, C-8), 30.3 (s,
C-4), 29.0 (s, C-7), 28.8 (s, C-3), 15.1 (s, Me), 11.6 (s,
B-Me). 103Rh-NMR (CD2Cl2, 298 K, 400 MHz): 1134
(s).
10.6, 3JHH=9.3, cis CHO), 3.72 (t, 2JHH=10.6,
3JHH=9.4, trans CHO), 3.39 (m, CHN), 3.06 (br,
H-6), 2.97 (br, H-5), 2.24 (m, H-8), 2.19 (m, CH-i-
Pr), 2.05 (m, H-3), 1.95 (m, H-8% and H-4), 1.77 (m,
3
H-4%), 1.70 (m, H-7), 1.58 (m, H-3%), 1.38 (d, JHH
=
6.7, Me), 1.34 (m, H-7%), 0.92 (d, 3JHH=6.7, Me).
2
13C-NMR (CD2Cl2, 298 K, 400 MHz): 89.7 (d, JPC
=
2
10.7, C-1), 82.4 (d, JPC=15.0, C-2), 74.9 (s, CHN),
72.8 (s, C-5), 72.6 (s, CHO), 62.4 (s, C-6), 34.4 (s,
C-4), 32.6 (s, C-8), 30.6 (s, CH-i-Pr), 29.2 (s, C-7),
28.1 (s, C-3), 22.6 (s, Me), 16.7 (s, Me). 31P-NMR
(CD2Cl2, 298 K, 400 MHz): 18.5 (s).
5. Supplementary material
4.2.3. Complex 16
Two full numbering schemes for the diffraction re-
sults on 15a and 15b (2 pages), plus tables of atomic
coordinates, bond lengths, bond angles, anisotropic
displacement parameters and hydrogen coordinates for
15a and 15b (17 pages) are available on request from
the author.
A solution of [Rh(COD)2]BF4 (20 mg, 0.05 mmol)
and ligand 11 (25 mg, 0.05 mmol) in CH2Cl2 (2 ml) was
stirred at r.t. for 2 h. The solvent was evaporated i.v.
and the residue was washed with hexane. Complex 16
was obtained as small needles from CH2Cl2ꢀether.
Yield: 30 mg, 77%. MS (FAB): 707 (M+ꢀBF4−) (100).
Anal. Calc. for C38H37O3BF4PSRh (794.46): C, 57.45;
1
H, 4.96. Found: C, 57.34; H, 4.91. H-NMR (CD2Cl2,
Acknowledgements
298 K, 400 MHz): 5.92 (m, CHO), 5.95 (br, H-2), 5.74
(br, H-1), 5.10 (br, H-5), 3.67 (br, H-6), 3.48 (br d,
2JHH=13.9, cis SCH2), 3.37 (m, CH2ꢀEt), 3.17 (m,
CH2ꢀEt), 2.83 (q, 2JHH=14.0, 3JHH=11.0, trans
SCH2), 2.60 (m, H-3 and H-4), 2.49 (m, H-8 and H-8%),
2.45 (m, H-4%), 2.38 (m, H-3%), 2.20 (m, H-7%), 2.03 (m,
H-7), 1.66 (t, 3JHH=7.4, 3JHH=7.7, Me). 13C-NMR
P.S.P. thanks the Swiss National Science Foundation
and the ETH Zurich for financial support. We also
thank F. Hoffmann–La Roche AG, Basel, for the
MeOꢀBiphep ligand, Professor A. Togni for ferrocene
ligand 7 as well as Johnson Matthey for the loan of
RhCl3. Special thanks are due Dr Heinz Ru¨egger for
the loan of complex 14 and for helpful discussions.
1
(CD2Cl2, 298 K, 400 MHz): 116.5 (q, J(Rh,C), 5.0,
2J(P,C), 12.9, C-2), 113.6 (q, 1J(Rh,C), 5.7, 2J(P,C),
12.9, C-1), 92.1 (d, 1J(Rh,C), 10.1, C-5), 86.6 (d,
1J(Rh,C), 9.2, C-6), 80.1 (s, CHO), 40.8 (s, SCH2), 35.8
(s, CH2ꢀEt), 32.0 (s, C-8), 31.4 (s, C-7), 28.9 (s, C-4),
28.7 (s, C-3), 15.2 (s, Me) 31P-NMR (CD2Cl2, 298 K,
400 MHz): 137.6 (d, 1JRhP=195). 103Rh-NMR
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