Rhodium COD complexes of mixed donor set tripod ligands: Coordination chemistry and catalysis

Article abstract of DOI:10.1016/S0022-328X(98)00882-1

The reaction of the novel mixed tripod ligands RCH₂C(CH₂X)(CH₂Y)(CH₂Z) 1-6 (X, Y, Z=PPh₂, NR₂, pyrazol-1-yl; R=H, OH) with [Rh^I(COD)Cl]₂ is investigated. The resulting rhodium COD complexes [(1-6)Rh(COD)]PF₆, 7 are characterized by NMR spectroscopy, mass spectra and elemental analysis. In addition, X-ray structure analysis is performed on several compounds 7, where in contrast to the behavior of the parent compound triphos [MeC(CH₂PPh₂)₃], the potential tripod ligands 2-6 are found to coordinate in a bidentate mode. {η²-P,O-[HOCH₂C(CH₂PPh₂)(CH ₂NEt₂)₂]Rh(COD)]}PF₆, 7i exhibits the first structurally characterized example of an intramolecular hydrogen bond between a non-coordinated and a coordinated donor atom. The activities of the complexes 7 as catalyst precursors in the homogeneous hydrogenation of diphenylacetylene and (Z)-α-N-acetamidocinnamic acid are tested and rationalized with respect to a proposed reaction mechanism.

Full text of DOI:10.1016/S0022-328X(98)00882-1

Journal of Organometallic Chemistry 571 (1998) 231–241
Rhodium COD complexes of mixed donor set tripod ligands:
coordination chemistry and catalysis1
Albrecht Jacobi, Gottfried Huttner *, Ute Winterhalter
Anorganisch-Chemisches Institut der Uni6ersita¨t Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Received 19 May 1998
Abstract
The reaction of the novel mixed tripod ligands RCH2C(CH2X)(CH2Y)(CH2Z) 1–6 (X, Y, Z=PPh2, NR2, pyrazol-1-yl; R=H,
OH) with [RhI(COD)Cl]2 is investigated. The resulting rhodium COD complexes [(1–6)Rh(COD)]PF6, 7 are characterized by
NMR spectroscopy, mass spectra and elemental analysis. In addition, X-ray structure analysis is performed on several compounds
7, where in contrast to the behavior of the parent compound triphos [MeC(CH2PPh2)3], the potential tripod ligands 2–6 are found
to coordinate in a bidentate mode. {p2-P,O-[HOCH2C(CH2PPh2)(CH2NEt2)2]Rh(COD)]}PF6, 7i exhibits the first structurally
characterized example of an intramolecular hydrogen bond between a non-coordinated and a coordinated donor atom. The
activities of the complexes 7 as catalyst precursors in the homogeneous hydrogenation of diphenylacetylene and (Z)-h-N-acetami-
docinnamic acid are tested and rationalized with respect to a proposed reaction mechanism. © 1998 Elsevier Science S.A. All
rights reserved.
Keywords: Mixed donor set ligands; Rhodium COD complexes; Hydrogen bonding; Hydrogenation
1. Introduction
coordination mode, which is preferred by neopentane
based trisphosphane ligands, is more of an impediment
for this type of catalytic transformation ([3]c, [4]).
This result can mainly be ascribed to the in general
nondissociative character of p3-chelating triphos, which
leaves the corresponding fragments unable to create
free coordination sites at the metal center ([3]c). In the
case of an ‘arm-off’ process, as recently found under
hydroformylation conditions [5], where one of the three
phosphine arms in triphos creates a free site for sub-
strate binding, the similarity of the phosphine donors
with respect to their kinetic lability makes the forma-
tion of the active p2-coordinated species an unselective
process ([4]d).
In the case of bidentate chelate ligands, a way to
faciliate and possibly even control this dissociation
process, is the use of hemilabile ligands with two elec-
tronically different donor groups (e.g. phosphine and
phosphinoxide, amine or ether functions) ([6]). In addi-
tion, this type of ligands with soft and hard donor
Neopentane based tripod ligands of the general con-
stitution RC(CH2X)(CH2Y)(CH2Z) with X, Y, Z being
donor groups have been shown to complex transition
metals in a facial coordination mode [1]. In their metal
templates, tripod-M, one half of the coordination
sphere is blocked effectively by the ligand cage, while
the individual types of donor groups affect the shape of
the remaining coordination space [2]. This fact, to-
gether with the prominent ability of trisphosphanes
(e.g. triphos) to stabilize various transition metals in
different oxidation states [1], makes tripod ligands ideal
candidates for catalytic applications [3]. However, it
was found for rhodium catalized hydrogenation and
hydroformylation reactions of olefins, that the trihapto
* Corresponding author. Tel.: +49 622 1548481; fax: +49 622
1545707.
1 Dedicated to Prof. Dr. Dr. h.c. muet. E.O. Fischer on the
occasion of his 80th birthday.
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00882-1

232
A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
Scheme 1.
functions creates distinctive electronic conditions at the
reactive positions trans to a certain donor function at
the metal. This can lead to higher selectivities, as shown
for example in the industrial synthesis of h-olefins
(SHOP ([6]b)) (Scheme 1).
Herein we report the synthesis and structural charac-
terisation of rhodium(I) complexes with mixed-donor
set hemilabile ligands which are potential tripods [7]. In
addition, rhodium(I) complexes of the chelating diphos
ligands 1a (dppp) and 1b are prepared as standard
catalyst precursors to be compared with the hemilabile
systems.
2. Results and discussion
The synthesis of rhodium(I) complexes 7 was per-
formed according to a modified literature procedure
([4]d). The diphos ligands of type 1 react with half an
equivalent of di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I) ([8]) and one equivalent of potassium
hexafluorophosphate to form the complexes 7a and 7b
(Scheme 2). The presence of a pseudo-four-coordinate
structure in 7a and 7b, where the metal center is
surrounded by a chelating diphos and the COD coli-
gand, can be deduced from their respective NMR data:
Fig. 1. Molecular structure of the cations of 7b and 7c in the solid state. Selected bond distances (pm), bond angles (°) and torsion angles (°).

A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
233
Scheme 2.
The 31P-NMR spectra of 7a and 7b show just one
doublet at small positive l values which is in accord
with two chemically equivalent phosphorus atoms cou-
pled to 103Rh and a septet for the PF6− counterion at l
around −145 (see Section 3) [9]. Consistently two
broad signals with a 2:1 ratio for the methylene and the
olefinic COD protons are found in their 1H-NMR
spectra (see Section 3). Crystals of 7b which were
suitable for X-ray diffraction could be obtained after
column chromatography of the crude product over
silica gel with dichloromethane/diethylether 1:1 and
vapour gas diffusion of petroleum ether 40/60 into a
dichloromethane solution of purified 7b.
The mixed donor set PPN tripod ligands 2a, 2b and
4a show a coordination behavior at the rhodium center
which is similar to the one observed for the diphos
ligands 1. The respective 31P-NMR spectra of the new
complexes 7c, 7d and 7e again show just one doublet at
positive l values (c. f. 7a, 7b). The fact, that the amine
donor is not coordinated in these compounds and thus
is in a dangling arm position is prooved by X-ray
structure determination in the case of 7c (see below).
While 7b is found to crystalize in spacegroup P21
with one molecule in the crystallographically indepen-
dent unit, in 7c the mirror plane of its crystallographic
space group P21/m is found as a symmetry element of
the cation (Fig. 1, Table 1). Despite this fact, the
conformations of 7b and 7c in the solid state are very
similar (Fig. 1, Table 1). In both cases the ligands react
to form six membered chelate rings in a chair confor-
mation with the phenyl rings in an achiral arrangement
(see Table 1, torsion angles). The coordination of the
metal center is pseudo square planar and the Rh–P
bond lengths and P–Rh–P angles are in the expected
range in each case (Table 1) [9]. The relative positions
of the coligand in 7b and 7c as well as the orientation
of the phenyl rings at the phosphorus centers are
comparable. In conclusion, the dangling amino arm
function in 7c does not seem to influence the coordina-
tion sphere of the metal in these complexes. The con-
formation of the COD ligands in 7b and 7c is different
(Fig. 1). Conformations of both types have previously
been reported in the literature ([4]c).
Complex 7d is obtained as a yellow microcrystalline
solid, while 7e is a viscous, orange-coloured oil; any
attempt to grow single crystals suitable for X-ray dif-
fraction failed. However, a comparison of the NMR
data of 7c with the data of 7d and 7e leads to the
proposal of an analoguos p2-P,P coordination mode
for the PPN ligands in 7d and 7e (Scheme 2).
Ligand 3 reacts with half an equivalent of di-v-
chloro-bis-(p4-1,5-cyclooctadiene)-dirhodium(I)
and
one equivalent of potassium hexafluorophosphate to
form the compound 7f (Scheme 3). After chromato-
graphic workup and recrystallisation 7f can be obtained
in high yield in the form of large yellow crystals suit-
able for X-ray structure analysis. It is found, that the
potentially tripodal ligand 3 is forming a pseudo square
planar coordination sphere at the rhodium, leaving one
pyrazolyl donor uncoordinated (Fig. 2).
While this type of p2-coordination was observed for
Pt(II) [10] and Pd(II) [11] complexes of tris-(pyrazol-1-
yl)methane (with a fast exchange of coordinated and
Table 1
Selected bond distances (pm), bond angles (°) and torsion angles (°)
for 7b, and 7c
7b
7c
Rh–P1
Rh–P2
230.3(4) Rh–P1
231.7(4)
230.3(2)
Rh–C31
Rh–C32
Rh–C35
221.1(17) Rh–C21
229.8(17) Rh–C22
218.7(18)
224.6(8)
224.0(8)
Rh–C36
232.0(17)
P1–Rh–P2
90.7(1) P1–Rh–P1A
89.4(1)
93.1
P1–Rh–C31/C32
P2–Rh–C35/C36
Rh–P1–C11–C6
Rh–P1–C17–C12
Rh–P2–C23–C18
93.5
92.0
P1–Rh–C21/C22
−96.1(13) Rh–P1A–C11A–C6A −100.1(7)
0.0(12) Rh–P1A–C17A–C12A −173.8(6)
90.1(14) Rh–P1–C11–C6
100.1(7)
173.8(6)
Rh–P2–C29–C24 −179.3(14) Rh–P1–C17–C12

234
A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
Scheme 3.
uncoordinated donors in the case of Pd(II)), [Ir(-
COD)Cl]2 reacts with tris-(pyrazol-1-yl)methane to
form p2- as well as p3-coordinated derivatives, which
equilibrate in solution [12]. In contrast to the complexes
of tris-(pyrazol-1-yl)methane, which form six membered
chelate rings, ligand 3 necessarily forms an eight mem-
bered chelate cycle in 7f (Fig. 2). The conformation of
the ring is comparable to an extended chair form. As a
consequence of the hybridisation of the aromatic pyra-
zol systems, the ring atoms C1, N11, N1 and Rh as well
as C2, N22, N2 and Rh, respectively lie in one plane
(Fig. 2). The bite angle of the ligand is with 84.9°
significantly smaller than the bite angle in the six mem-
bered diphos chelates of 7b and 7c (see above). The
weak trans effect of the nitrogen donors in 7f gives rise
to much shorter Rh–C(COD) bonds than in 7b and 7c,
where the olefins are in competition with phosphorus
donor groups (Fig. 2, Table 1).
In order to obtain hemilabile rhodium complexes
with both, hard and soft donor functions coordinating
to the metal center, PNN ligands 4b, 5b and 6 were
used in complexation reactions of the above type. Lig-
and 5b is of the standard neopentane tripod type, while
4b and 6 have an additional OH function at the back-
bone, that is as well capable of interacting with the
metal center ([6]a). Ligands 4b, 5b and 6 react with the
rhodium salt to form complexes 7g, 7h and 7i as
yellow–orange
coloured
microcrystalline
solids
(Schemes 4 and 5). The metal coordination of the
phosphorus donor can in all three cases be deduced
Fig. 3. Molecular structure of 7g in the solid state. Selected bond
distances (pm), bond angles (°) and torsion angles (°): Rh–P1 229.4
(5),Rh–N22 212.9(13), Rh–C18 240.4(20), Rh–C19 201.4(14), Rh–
C22 214.6(13), Rh–C23 211.7(14), P1–Rh–N22 99.8(3), P1–Rh–
Fig. 2. Molecular structure of 7f in the solid state. Selected bond
distances (pm), bond angles (°) and torsion angles (°): Rh–N1
211.2(2), Rh–N2 208.7(2), Rh–C15 211.5(3), Rh–C16 214.1(2), Rh–
C19 213.1(2), Rh–C20 213.7(2), C15–C16 138.6(4), C19–C20
138.9(4), N1–Rh–N2 84.9(1), N1–Rh–C19/C20 95.2, N2–Rh–C15/
C16 92.5, N1–N11–N22–N2–5.8, Rh–N1–N11–C1 23.6(3), Rh–
N2–N22–C2 −7.8(3).
C18/C19
85.7,
N22–Rh–C22/C23
80.4,
Rh–N22–N2–C2
−20.2(17), N22–N2–C2–C4 −67.2(14), N2–C2–C4–C1 102.4(14),
C2–C4–C1–P1 −62.6(16), C4–C1–P1–Rh 45.5(12), C1–P1–Rh–
N22 −60.9(12), P1–Rh–N22–N2 68.7(14), Rh–P1–C11–C6
72.5(11), Rh–P1–C17–C12 15.9(16).

A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
235
increase of the bite angle from around 88° in
4b*Mo(CO)4 to around 100° in 7g.
In the case of the PNN% tripod ligand 5b the ques-
tion, whether the aromatic or the aliphatic amine func-
tion is coordinated in addition to the phosphorus donor
in complex 7h, cannot be answered unambiguously.
1
The H-NMR spectrum does not allow to differentiate
between coordinated and uncoordinated donor groups
due to strong overlapping in the aliphatic region (see
Section 3).
The coordination behavior of the PNN hydroxy
tripod ligand 6 incorporating one PPh2 group and two
NEt2 groups is in strong contrast to the results found
with 4b at Rh(I) (Figs. 3 and 4). The X-ray structure of
complex 7i exhibits an p2-P,O binding mode, the metal
again being in a pseudo square planar geometry (Fig.
4). The P1–Rh–O5 bite angle of 89° is in the range
found for chelating bisphosphanes in the compounds 7b
and 7c while the Rh–P1 bond length is with 227 pm
somewhat shorter than usual (Fig. 4). The weak trans
effect of the oxygen donor is reflected by a significant
shortening of the Rh–C bonds trans to O1 (212 pm)
compared to the Rh–C bonds trans to P1 (224 pm).
The alcohol function of the ligand is deprotonated
upon coordination, while one of the amino groups is
protonated and thus acting as a proton donor in a
hydrogen bond with the metal bound oxygen (Fig. 4).
The second NEt2 group in 7i is not coordinated and
points away from the metal center. The bridging hydro-
gen H55 was located by difference Fourier techniques
and its position was refined by least-squares. Although
Fig. 4. Molecular structure of 7i in the solid state. Selected bond
distances (pm), bond angles (°) and torsion angles (°): Rh–P1
227.0(1), Rh–O1 204.3(2), Rh–C18 225.3(3), Rh–C19 223.0(3), Rh–
C22 213.2(3), Rh–C23 211.4(3), N3–H55 106.7, O5–H55 160.4,
N3–H55–O5 148.7, P1–Rh–O5 89.0(1), P1–Rh–C18/C19 96.4, O5–
Rh–C22/C23 87.8, Rh–P1–C1–C4 53.1(2), P1–C1–C4–C5
−
4.1(4), C1–C4–C5–O5 −63.7(4), C4–C5–O5–Rh 72.9(3),
C5–O5–Rh–P1 −14.0(2), O5–Rh–P1–C1 −39.6(1), P1–C1–C5–
O5 −59.1, O5–C5–C3–N3 13.6, Rh–P1–C11–C6 88.4(3), Rh–P1–
C17–C12 16.3(3).
this hydrogen bond is strong in the solid state (dN–O
=
1
257 pm), no signal could be assigned in the H-NMR
spectrum (probably due to strong overlap in the
aliphatic region) nor could an appropriate band be
found in the IR spectrum of 7i. The hydrogen bond
seems to influence the six-membered chelate cycle,
which is found in an unusual twisted boat form, as
indicated by the respective torsion angles (Fig. 4) [13].
The adjacent six-membered cycle built up by hydrogen
bonding is in a clear boat type arrangement, which is
described by a small torsion angle O5–C5–C3–N3 of
only 13.6° (Fig. 4).
from an upfield shift in the 31P-NMR spectra of Dl
around 45 ppm compared to the free ligand [9]. In
addition a 1J(Rh,P) coupling of around 150 Hz is
found in each case (see Section 3). The interpretation of
1
the H-NMR spectra (200 MHz) of 7g, 7h and 7i poses
some difficulties as the low energy barrier for the
rotation of the COD coligand leads to broad signals for
the olefinic and methylene protons which strongly over-
lap with the methylene groups of the tripod ligand
1
([4]c). Nevertheless, the signal groups in the H-NMR
The torsion angles Rh–P1–C11–C6 and Rh–P1–
C17–C12 account for the rotational position of the two
phenyl groups at P1. They are closely similar for the
complexes 7g and 7i, although these two compounds
incorporate different chelate ring sizes and bite angles
(Figs. 3 and 4).
This finding is probably caused by the steric interac-
tion of one phenyl ring with the bulky COD coligand,
which restricts the value of Rh–P1–C11–C6 to around
80°. A small value of Rh–P1–C17–C12 (around 16°) is
found as a consequence of the gearing of the phenyl
rings at P1 (Fig. 4) ([2]a).
spectra of 7g, 7h and 7i show the expected integral
ratios (see Section 3).
Single crystals of 7g are obtained after recrystallisa-
tion from dichloromethane at 0°C (see Section 3). Due
to bad crystal quality and disordered solvent molecules,
the result of the crystal structure analysis of 7g allows
only for a qualitative interpretation of the structural
features (see Table 4). The hydroxy tripod ligand 4b is
found in an p2-P,N-coordination mode (Fig. 3). A
comparison of the chelate cycle in 7g with the crystal
structure of 4b*Mo(CO)4 ([7]b), in which the ligand is
found to be p2-P,N-coordinated as well, shows an

236
A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
Scheme 4.
3. Catalysis
lacetylene and (Z)-h-N-acetamidocinnamic acid. The
conversion rates for the hydrogenation of dipheny-
lacetylene with compounds 7 are found to be lower
than the rates obtained for triphos rhodium compounds
(Table 2) ([3]c). The diphos system 7a is the most
active, while the presence of additional N or O donor
groups seems to inhibit the reaction (Table 2). Complex
7g, forming a P,N chelate, is almost as active as the P,P
chelate 7c, which means, that a diphos fragment is not
neccessary to obtain catalytic activity. 7g is also the
only catalyst producing an appreciable amount of cis-
stilbene, although the product distributions cannot be
rationalized with the data at hand ([3]c).
Tripod rhodium complexes with three electronically
equivalent donors were employed in catalytic hydro-
genations of various olefins ([3]a–d, [4]c, d, [14]). While
chelating olefins of the enamide type showed poor
results with all systems tested ([4]c, d, [14]), the hydro-
genation of simple non-chelating olefins such as 1-hex-
ene proved more active with [(triphos)RhH(C2H4)]
([3]c). This is presumably due to the fact, that non-
chelating olefines need no phosphine dissociation to
accomplish the hydrogenation reaction.
On the other hand, the Halpern-mechanism for the
catalytic hydrogenation of chelating enamides with
diphos rhodium complexes [15] would, in adaption to a
tripodal system, require the dissociation of one coordi-
native bond (not admitting the intermediacy of 20-elec-
tron species) to allow the addition of H2 [16]. In the
proposed substrate catalyst complex ([4]d) this dissocia-
tion could affect either one of the tripod donor groups
or the olefin carbonyl function.
The hydrogenation of (Z)-h-N-acetamidocinnamic
acid was performed in an hydrogenation apparatus,
which allowed the measurement of the H2 consump-
tion. In contrast to the results for the hydrogenation of
diphenylacetylene, the compounds incorporating
a
pyrazolyl residue were all catalytically inactive (no con-
version after 120 h, see Table 3). While 7b with the
neopentane diphos chelate affected quantitative conver-
sion of the substrate in only 20 min, the hemilabile PPN
system 7c took 1.5 h and the tripodal [(triphos)Rh-
In order to test this hypothesis, the hemilabile Rh(I)
systems 7 were used in the hydrogenation of dipheny-
Scheme 5.

A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
237
Table 2
Hydrogenation of diphenylacetylene
Catalyst
Conversion (%)
Crude compositiona
1,2-Diphenylethane (%)
cis-Stilbene (%)
trans-Stilbene (%)
Diphenylacetylene (%)
7a
83
50
22
42
46
8
9
B5
B5
B5
14
33
40
9
17
51
78
58
7cb
7ec
7gd
10
18
Reaction conditions, 2 mmol diphenylacetylene; 0.02 mmol catalyst; 25 ml THF; 20°C; hydrogen pressure 30 bar; reaction time 3 h; 1 mol%
catalyst.
a The fraction of cis-stilbene was only roughly estimated due to overlapping signals in the aromatic region (200 MHz).
b 1 Bar, 100% conversion after 4 days.
c 1 Bar, 100% conversion after 5 days.
d 1 Bar, 100% conversion after 5 days.
(COD)]PF6 reached 100% conversion only after 168 h
(Table 3). This order of reactivity supports the pro-
posed dissociation of either a solvent molecule (7b) or a
donor group of the ligand {7b, [(triphos)Rh-
(COD)]PF6} as the rate determining step during the
catalytic cycle [15,16]. In accordance with this idea,
breaking a labile Rh–N bond in catalyst 7b is more
facile than breaking a Rh–P bond in [(triphos)-
Rh(COD)]PF6 and leads to a strongly increased activity
of 7b.
Finally, it must be stated that the rhodium catalysed
hydrogenation does not seem to be the right choice of
a catalytic application for the new hemilabile tripod
ligands. Nevertheless it was shown, that a lot of differ-
ent coordination modes can be realised with the various
P,N ligands, including a new type of ‘secondary’ inter-
action of a free donor group with a metal bound donor
group in the case of 7i [17]. Thus the concept of
hemilabile chelate ligands can be extended to tripod
ligands, making the finding of new applications for this
concept a worthwhile task.
standard. MS (EI): Finnigan MAT 8320; Fast-Atom-
Bombardment (FAB) xenon, matrix: 4-nitrobenzyl-al-
cohol. Melting points (m.p.): Gallenkamp MFB-595
010, melting points are uncorrected. Elemental analy-
ses: Microanalytical Laboratory of the Organisch-
Chemisches Institut, Universita¨t Heidelberg. The silica
gel (Kieselgel z.A. 0.06–0.2 mm, J.T. Baker Chemicals
B.V.) used for chromatography was degassed at 1 mbar
for 24 h and saturated with argon. Di-v-chloro-bis-(p4-
1,5-cyclooctadiene)-dirhodium(I) was prepared accord-
ing to a literature procedure [8]. 1,3-Bis-(diphenyl-
phosphanyl)propane and 2,2-bis-(diphenylphosphanyl-
methyl)propane were purchased from Lancaster Chemi-
cals. All other chemicals were obtained from
commercial suppliers and used without further purifica-
tion.
4.2. X-ray structure determinations
The measurements were carried out on a Siemens P4
four circle diffractometer (equipped with a low temper-
ature device) with graphite monochromated Mo–Kh
radiation. All calculations were performed using the
SHELXT PLUS [19] software package. Structures were
solved by direct methods with the SHELXS-86 pro-
gram ([19]a) and refined with the SHELX-93 program
([19]b). Graphical handling of the structural data dur-
4. Experimental part
4.1. General
All manipulations were carried out under an argon
atmosphere by means of standard Schlenk techniques.
Solvents were dried by standard methods [18] and
distilled under argon. The solvents CDCl3 and CD2Cl2
used for the NMR spectroscopic measurements were
degassed by three successive ‘freeze-pump-thaw’ cycles
Table 3
Hydrogenation of (Z)-h-N-acetamidocinnamic acid
Catalyst
Reaction time (h) Conversion (%)
[(Triphos)Rh(COD)]PF6
168
20
0.3
1.5
120
100
100
100
100
0
7a
7b
7c
7e
7f
˚
and dried over 4-A molecular sieves. NMR: Bruker
Avance DPX 200 at 200.13 MHz (1H), 50.323 MHz
(13C{1H}), 81.015 MHz (31P{1H}), T=298K, chemical
shifts (l) in ppm with respect to CHCl3 (1H: l=7.27,
13C: l=77.0) and CH2Cl2 (1H: l=5.32, 13C: l=53.5)
as internal standards. 31P chemical shifts (l) in ppm
with respect to 85% H3PO4 (31P: l=0) as external
120
120
0
0
7g
Reaction conditions, 1 mmol AAC; 25 ml MeOH; 20°C; 1 bar H2; 1
mol% catalyst.

238
A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
Table 4
Crystal data for 7b, 7c, 7f, 7g, and 7i
Compound
Formula
7b
7c
7f
7g
7i
C
37H42P3F6Rh
C39H47NP3F6Rh C22H30N6F6Rh
C31H37N4OP2F6Rh*CH C33H51N2P2F6Rh
2Cl2*Et2O
Molecular mass (g)
Crystal size (mm)
Crystal system
Space group (no.)
a (pm)
b (pm)
c (pm)
h (°)
i (°)
796.53
0.2×0.2×0.25
Monoclinic
P21 (4)
112.38(1)
150.85(1)
114.21(2)
90
112.55(1)
90
1788.1(4)
2
839.63
0.3×0.3×0.2
Monoclinic
P21/m (11)
108.67(3)
174.30(5)
116.97(3)
90
107.72(1)
90
2110.4(10)
2
626.39
0.3×0.3×0.1
Triclinic
760.50
0.2×0.1×0.2
Monoclinic
P21 (4)
94.61(2)
174.91(3)
221.38(6)
90
81.03(2)
90
3618.6(14)
2
770.62
0.4×0.4×0.3
Monoclinic
P21/c (14)
128.44(1)
98.26(2)
281.31(4)
90
100.65(1)
90
3489.1(9)
4
(
P1 (2)
94.12(3)
108.41(4)
130.75(4)
74.13(2)
76.98(1)
83.05(2)
1247.8(7)
2
k (°)
V (106 pm3)
Z
Dcalc. (g cm−3
T (K)
)
1.479
298
1.447
200
1.667
200
1.527
200
1.448
200
No. of reflections for cell parameter
37
25
25
25
48
refinment
Scan range
3.952q552.0°
ꢀ=7
3840
4.352q550.0°
ꢀ=8
4051
3.952q550.5°
ꢀ=5
4786
4.452q556.5°
ꢀ=12
6048
5.152q551.0°
ꢀ=8
6785
Scan speed (° min−1
)
No. of reflections measured
No. of unique reflections
3654
3839
4486
5676
6485
No. of reflections observed
Observation criterion
No. of parameters refined
Residual electron density (10−6e pm−3
R1/Rw (%) (refinement on F2)
2903
I=2|
438
0.68
3.5/9.4
2863
I=2|
337
1.10
6.9/18.5
4062
I=2|
445
0.77
2.5/6.2
2829
I=2|
441
5362
I=2|
427
0.73
3.7/10.7
)
1.88
12.8/26.6a
a Due to badly resolved, disordered solvent molecules.
ing solution and refinement was done with XPMA [20].
An absorption correction („-scan, D„=10°) was ap-
plied to all data. Atomic coordinates and anisotropic
parameters of the non-hydrogen atoms were refined by
full-matrix least-squares calculations. Data for the
structure determination are compiled in Table 4.
tion was chromatographed over silica gel. After elution
of small amounts of side products (not further charac-
terized) with dichloromethane, the main product was
eluted with dichloromethane/diethylether 1:1 as a sharp
orange-coloured band, which gave upon removal of the
solvent 570 mg (0.74 mmol, 74%) 7a as an orange-
coloured microcrystalline solid, m.p. 190°C (decompo-
sition). Anal. Found: C, 53.86; H, 5.42; P, 11.94.
C35H38P3F6Rh (768.50): Anal. Calc.: C, 54.70; H, 4.98;
P, 12.09%. 1H-NMR (CD2Cl2): 2.01–2.79 [m, 12H,
methylene-H(COD), CH2P], 4.65 [bs, 4H, olefin-
H(COD)], 7.20–7.58 (m, 20H, aromatic H). 13C-NMR:
no spectrum obtained because of the low solubility of
7a in CD2Cl2. 31P-NMR (CD2Cl2): +8.2 (d, 2P,
1JRhP=142 Hz), −145.6 (sept, 1P, 1JPF=712 Hz,
PF6−).
4.3. [1,3-Bis-(diphenylphosphanyl)propane-rhodium(I)-
p4-1,5-cyclooctadiene]hexafluoro-phosphate (7a)
A total of 247 mg (0.5 mmol) di-v-chloro-bis-(p4-1,5-
cyclooctadiene)-dirhodium(I) was dissolved in 5 ml
dichloromethane. In a second flask 190 mg (1.03 mmol)
potassium hexafluorophosphate was dissolved in 5 ml
acetone adding 0.2 ml of water. This solution was
added to the orange-coloured rhodium(I) solution. A
colourless potassium chloride precipitate was formed
during 5 min, while the colour of the reaction mixture
4.4. [2,2-Bis-(diphenylphosphanylmethyl)-propane-
rhodium(I)-p4-1,5-cyclooctadiene]hexafluorophosphate
(7b)
faded.
A
total of 412 mg (1 mmol) 1,3-bis-
ml
(diphenylphosphanyl)propane 1a ([8]a) in
5
dichloromethane was then added. After stirring at
room temperature for 1 h, the solvents were removed in
vacuo (10−1 mbar). The residue was taken up in ace-
tone and dried over sodium sulfate. The insoluble
potassium chloride was removed by filtering the solu-
tion over kieselgur. The resulting orange-coloured solu-
Compound 7b was prepared as described above for
7a. Starting materials: 440 mg (1 mmol), 2,2-bis-
(diphenylphosphanylmethyl)-propane 1b ([8]b), 247 mg
(0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hexa-

A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
239
fluorophosphate. Chromatographic workup (see above)
gave upon removal of the solvent 570 mg (0.71 mmol,
71%) 7b as an orange-coloured microcrystalline solid.
Recrystallisation afforded 500 mg (0.63 mmol, 63%) of
7b in the form of orange-coloured crystals suitable for
X-ray structural analysis, m.p. 179°C (decomposition).
Anal. Found: C, 55.61; H, 5.59; P, 11.54.
C37H42P3F6Rh (796.56): Anal. Calc.: C, 55.79; H, 5.31;
moval of the solvent 590 mg (0.71 mmol, 71%) 7d as a
yellow microcrystalline solid. m.p. 185°C (decomposi-
tion). Anal. Found2: C, 51.26; H, 5.24; N, 1.54.
C38H45NP3F6Rh (825.60): Anal. Calc.: C, 55.28; H,
5.49; N, 1.70%. MS (FAB), m/z (%) [frag.]: 680 (100)
[{(2b)Rh(COD)}+], 572 (29) [{(2b)Rh}+], 494 (37)
[{(2b)Rh}+ –Ph]. 1H-NMR (CDCl3): 0.50 (s, 3H,
CqCH3), 1.15 (bs, NH), 1.99–2.60 (m, 17H, methylene-
H(COD), CH2P, CH2N, NMe), 4.52 [bs, 4H, Olefin-
H(COD)], 7.30–7.78 (m, 20H, aromatic H). 13C-NMR:
no spectrum obtained because of the low solubility of
1
P, 11.67%. H-NMR (CD2Cl2): 0.69 (s, 6H, CqCH3),
2.37–2.47 [m, 12H, methylene-H(COD), CH2P], 4.58
[bs, 4H, olefin–H(COD)], 7.22–7.74 (m, 20H, aromatic
H). 13C-NMR: no spectrum obtained because of the
low solubility of 7b in CD2Cl2. 31P-NMR (CD2Cl2):
+15.1(d, 2P, 1JRhP=142 Hz), −144.1 (sept, 1P,
1JPF=712 Hz, PF6−).
1
7d. 31P-NMR (CDCl3): +13.7 (d, 2P, JRhP=141 Hz),
1
−144.2 (sept, 1P, JPF=712 Hz, PF6−).
4.7. p2-(P,P)-[2,2-Bis-(diphenylphosphanylmethyl)-
2-(pyrazol-1-yl-methyl)-1-propanol-rhodium(I)-
p4-1,5-cyclooctadiene]hexafluorophosphate (7e)
4.5. p2-P,P-[2,2-Bis-(diphenylphosphanylmethyl)-
dimethylpropanamin-rhodium(I)-p4-1,5-cyclooctadiene]-
hexafluorophosphate (7c)
Compound 7e was prepared as described above for
7a. Starting materials: 525 mg (1 mmol) 4a ([7]b), 247
mg (0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) gave 800 mg (0.91 mmol, 91%) 11e in the form
of orange-coloured oil. Anal. Found: C, 53.60; H, 5.28;
N, 3.64%. C40H44N2OP3F6Rh (878.63): Anal. Calc.: C,
54.68; H, 5.05; N, 3.19%. MS (FAB), m/z (%) [frag.]:
733 (100) [{(4a)Rh(COD)}+], 625 (96) [{(4a)Rh}+],
547 (24) [{(4a)Rh}+ –Ph], 440 (25) [{(4a)Rh}+ –PPh2].
1H-NMR (CD2Cl2): 2.01–2.50 (m, 14H, methylene–
H(COD), CH2P, CH2N), 3.64 (m, 2H, CH2O), 4.59 [m,
4H, olefin–H(COD)], 6.22 (s, 1H, CHpz), 7.29–7.81
(m, 22H, CHpz, aromatic H). 13C-NMR (CD2Cl2): 27.4
(m, CH2P), 30,5 [bs, Cmethylene(COD)], 43.8 (s, Cq), 58.3
(m, CH2N), 65.9 (m, CH2O), 102.1, 103.6 [2bs,
Colefin(COD)], 105.7, 105.9 (2s, CH(4)pz), 129.1–140.1
(m, aromatic C, CH(5)pz, CH(3)pz). 31P-NMR
(CD2Cl2): +15.0 (d, 2P, 1JRhP=143 Hz), −144.2
Compound 7c was prepared as described above for
7a. Starting materials: 484 mg (1 mmol) 2a ([7]a), 247
mg (0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) gave upon removal of the solvent 490 mg (0.58
mmol, 58%) 7c as an orange-coloured microcrystalline
solid. Recrystallisation afforded 400 mg (0.48 mmol,
48%) of 7c in the form of orange-coloured crystals
suitable for X-ray structural analysis, m.p. 165°C. Anal.
Found: C, 55.69; H, 5.78; N, 1.60; P, 10.97.
C39H47NP3F6Rh (839.63): Anal. Calc.: C, 55.79; H,
5.64; N, 1.67; P, 11.07%. MS (FAB), m/z (%) [frag.]:
694 (100) [{(2a)Rh(COD)}+], 586 (92) [{(2a)Rh}+],
509 (22) [{(2a)Rh}+ –Ph], 401 (23) [{(2a)Rh}+ –PPh2].
1H-NMR (CDCl3): 0.39 (s, 3H, CqCH3), 1.73–2.70 (m,
20H, methylene–H(COD), CH2P, CH2N, NMe2), 4.28,
5.39 [2bs, 4H, olefin–H(COD)], 7.07–7.89 (m, 20H,
aromatic H). 13C-NMR (CDCl3): 27.1 (bs, CqCH3),
30,5 [bs, Cmethylene(COD)], 34.4 (m, CH2P), 40.9 (s, Cq),
49.1 (s, NCH3), 75.2 (m, CH2N), 100.0, 104.4 [2bs,
Colefin(COD)], 128.5–135.1 (m, aromatic C). 31P-NMR
1
(sept, 1P, JPF=712 Hz, PF6−).
4.8. p2-[1,1,1-Tris-(pyrazol-1-yl-methyl)ethan-rhod-
ium(I)-p4-1,5-cyclooctadiene] hexafluorophosphate (7f)
1
(CDCl3): +13.8 (d, 2P, JRhP=141 Hz), −144.2 (sept,
1
1P, JPF=712 Hz, PF6−).
Compound 7f was prepared as described above for
7a. Starting materials: 270 mg (1 mmol) 3 ([7]b), 247 mg
(0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) gave upon removal of the solvent 610 mg (0.97
mmol, 97%) 7f as a yellow microcrystalline solid. Re-
crystallisation afforded 490 mg (0.78 mmol, 78%) of 7f
in the form of yellow crystals suitable for X-ray struc-
tural analysis, m.p. 200–205°C (decomposition). Anal.
4.6. p2-P,P-[2,2-Bis-(diphenylphosphanylmethyl)-
methylpropanamin-rhodium(I)-p4-1,5-cyclooctadiene]-
hexafluorophosphate (7d)
Compound 7d was prepared as described above for
7a. Starting materials: 470 mg (1 mmol) 2b ([7]a), 247
mg (0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) allowed the elution of 7d as a sharp yellow band
with dichloromethane/THF 1:1 which gave upon re-
2 Carbon and hydrogen values were notoriously low, presumably
due to the incorporation of KCl.

240
A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
Found: C, 41.91; H, 4.82; N, 13.20; P, 4.86%.
C22H30N6PF6Rh (626.39): Anal. Calc.: C, 42.18; H,
4.83; N, 13.42; P, 4.94%. MS (FAB), m/z (%) [frag.]:
yellow microcrystalline solid. m.p. 190°C (decomposi-
tion). Anal. Found: C, 49.32; H, 5.65; N, 4.10%.
C32H44N3P3F6Rh (749.56): Anal. Calc.: C, 51.28; H,
5.92; N, 5.61%. MS (FAB), m/z (%) [frag.]: 604 (100)
[{(5)Rh(COD)}+], 494 (17) [{(5)Rh}+]. 1H-NMR
(CDCl3): 0.10 (s, 3H, CqCH3), 1.73–3.09 [m, 24H,
methylen–H(COD), CH2P, CH2N, NMe2], 3.71, 4.86
[2m, 4H, Olefin–H(COD)], 4.55, 5.51 (2m, 2H, CH2pz),
5.90 (bs, 1H, CH(4)pz), 7.20–7.89 (m, 10H, aromatic
H). 13C-NMR: no spectrum obtained because of the
low solubility of 7h. 31P-NMR (CDCl3): +16.2 (d, 1P,
1JRhP=149.0 Hz), −144.2 (sept, 1P, 1JPF=712 Hz,
PF6−).
1
481 (100) [{(3)Rh(COD)}+], 373 (6) [{(3)Rh}+]. H-
NMR (CDCl3): 1.00 (s, 3H, CqCH3), 2.06–2.71 (m, 8H
methylene–H(COD), 4.27 [bs, 4H, olefin–H(COD)],
4.62 (m, 4H, CH2N), 4.75, 5.63 (2bs, 2H, CH2N), 6.41
(m, 3H, CH(4)pz), 7.54–8.38 (m, 6H, CH(3)pz,
CH(5)pz). 13C–NMR (CDCl3): 18.5 (bs, CqCH3), 31.0
[bs, Cmethylene(COD)], 41.8 (s, Cq), 60.9, 61.4 (2bs,
CH2N), 84.6, 86.9 [2bs, Colefin(COD)], 106.3, 108.7 (2s,
CH(4)pz), 132.9–140.7 (m, aromatic C, CH(5)pz,
1
CH(3)pz). 31P-NMR (CDCl3): −143.9 (sept, JPF
=
712 Hz, PF6−).
4.11. p2-(P,O)-[2,2-Bis-(diethylaminomethyl)-
3-(diphenylphosphanylmethyl)-1-propanol] rhodium
(I)p4-1,5-cyclooctadiene]hexafluorophosphate (7i)
4.9. p2-(P,N)-[2-(Diphenylphosphanylmethyl)-
2,2-bis-(pyrazol-1-yl-methyl)-1-propanol-rhodium(I)-
p4-1,5-cyclooctadiene]hexafluorophosphate (7g)
Compound 7i was prepared as described above for
7a. Starting materials: 415 mg (1 mmol) 6 ([7]b), 247 mg
(0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) allowed the elution of 7i as a sharp yellow band
with dichloromethane/THF 1:1 which gave upon re-
moval of the solvent 650 mg (0.84 mmol, 84%) 7i as a
yellow microcrystalline solid. Recrystallisation afforded
540 mg (0.70 mmol, 70%) of 7i in the form of yellow
needles suitable for X-ray structural analysis, m.p. 120–
130°C (decomposition). Anal. Found: C, 51.09; H, 6.69;
N, 3.59; P, 7.96%. C33H51N2P2F6Rh (770.62): Anal.
Calc.: C, 51.43; H, 6.67; N, 3.64; P, 8.04%. MS (FAB),
m/z (%) [frag.]: 625 (100) [{(6)Rh(COD)}+], 513 (15)
[{(6)Rh}+], 415 (22) [(6)+]. 1H-NMR (CDCl3): 1.11
(m, 12H, CH2CH3), 2.12–3.01 [m, 22H, methylene–
H(COD), CH2P, CH2N, CH2CH3], 3.81 (s, 2H, CH2O),
5.15 [m, 4H, olefin–H(COD)], 7.54–7.70 (m, 10H,
aromatic H). 13C-NMR (CDCl3): 10.8 (s, NCH2CH3),
28.5 [bs, Cmethylene(COD)], 31.0 (m, CH2P), 33.1 (s,
CH2N), 42.0 (s, Cq), 49.0 (s, NCH2CH3), 63.7 (s,
CH2O), 72.0 (bs, CH2N), 108.2 [bs, Colefin(COD)],
129.6–133.8 (m, aromatic C). 31P-NMR (CDCl3): +
Compound 7g was prepared as described above for
7a. Starting materials: 405 mg (1 mmol) 4b ([7]b), 247
mg (0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) gave upon removal of the solvent 620 mg (0.81
mmol, 81%) 7g as a yellow microcrystalline solid. Re-
crystallisation at 0°C afforded 420 mg (0.55 mmol,
55%) of 7g in the form of yellow crystals suitable for
X-ray structural analysis, m.p. 170°C (decomposition).
Anal. Found: C, 49.12; H, 5.15; N, 7.27; P, 7.97%.
C31H37N4OP2F6Rh (760.50): Anal. Calc.: C, 48.96; H,
4.90; N, 7.37; P, 8.15%. MS (FAB), m/z (%) [frag.]: 615
(100) [{(4b)Rh(COD)}+], 507 (21) [{(4b)Rh}+]. 1H-
NMR (CD2Cl2): 2.21–2.90 (m, 10H, methylene–
H(COD), CH2N), 3.14, 5.05 [m, 4H, olefin–H(COD)],
3.72 (m, 2H, CH2P), 4.43 (bs, OH), 5.19 (bs, 2H,
3
CH2O), 6.41 (s, 1H, JHH=2.1 Hz, CH(4)pz), 7.49–
7.97 (m, 14H, aromatic H, CH(3)pz, CH(5)pz). 13C-
NMR: no spectrum obtained because of the low
solubility of 7f. 31P-NMR (CD2Cl2): +16.9 (d, 1P,
1JRhP=147 Hz), −144.0 (sept, 1P, 1JPF=712 Hz,
PF6−).
1
1
17.7 (d, 1P, JRhP=164 Hz), −144.2 (sept, 1P, JPF
=
4.10. p2-P,N-[2-(Dimethylaminomethyl)-2-(diphenyl-
phosphanylmethyl)-2-(3,5-dimethyl-pyrazol-1-yl-
methyl)-ethan-rhodium(I)-p4-1,5-cyclooctadiene]-
hexafluorophosphate (7h)
710 Hz, PF6−).
4.12. Hydrogenation experiments
The hydrogenations were performed under the condi-
tions given in Tables 2 and 3. Final conversions were
determined by 1H-NMR. The hydrogenations of
diphenylacetylene were performed in a HR100 steel
Compound 7h was prepared as described above for
7a. Starting materials: 394 mg (1 mmol) 5 ([7]b), 247 mg
(0.5 mmol) di-v-chloro-bis-(p4-1,5-cyclooctadiene)-
dirhodium(I), 190 mg (1.03 mmol) potassium hex-
afluorophosphate. Chromatographic workup (see
above) allowed the elution of 7d as a sharp yellow band
with dichloromethane/THF 1:1 which gave upon re-
moval of the solvent 680 mg (0.90 mmol, 90%) 7h as a
laboratory
autoclave
(Berghof/Maasen
GmbH)
equipped with a manometer and inlet and outlet valves.
The solutions were prehydrogenated for 1 h at room
temperature and normal pressure. The hydrogenations
of (Z)-h-N-acetamidocinnamic acid were performed at

A. Jacobi et al. / Journal of Organometallic Chemistry 571 (1998) 231–241
241
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Marhan (Normag). The consumption of H2 was moni-
tored during the reaction.
Acknowledgements
We are grateful to the German Science Foundation
(DFG), SFB 247, the VW Foundation (Stiftung Volk-
swagenwerk) and the Fonds der Chemischen Industrie
for financial support. The technical support by Th.
Jannack (mass spectrometry) and the Microanalytical
Laboratory of the Institute of Organic Chemistry is
gratefully acknowledged. We wish to thank Degussa
AG for a generous loan of RhCl3 ·3H2O.
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