Synthesis of C1-symmetric tripod ligands containing a P,P,N donor set -η2-coordination in d8-metal complexes

Article abstract of DOI:10.1002/ejic.200200448

Tripod ligands RC(CH₂X)(CH₂Y)(CH₂Z) (X, Y, Z = NR2, PR2) are accessible from α,β-unsaturated esters R(=CH2)COOR′. The key steps in this synthetic approach are Michael additions of amines and phosphanes to produce RCH(COOR′)(CH2X) (X = NR2, PR2) (2 and 3), followed by hydroxymethylation with paraformaldehyde to result in RC(COOR′)(CH₂OH)(CH₂X) (X = NR₂) (4). Standard transformations of this C₁-symmetric precursor allow for the synthesis of tripod ligands such as PhC(CH₂pz)(CH₂PPh₂)(CH₂PMes) (11). Coordination of these ligands with d⁸-metal ions [nickel(II), palladium(II), rhodium(I)] results in square-planar complexes with the chelate cycles in half-chair, twist-boat or boat conformations, depending on the specific substitution pattern. Coordination through two phosphane donors with the nitrogen donor acting as a dangling arm is generally preferred throughout. Detail preparative procedures and complete characterisation by analytical methods, including X-ray analysis of the coordination compounds, are given. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200200448

FULL PAPER
Synthesis of C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set ؊
η2-Coordination in d8-Metal Complexes
Ralf Faissner,[a] Gottfried Huttner,*[a] Elisabeth Kaifer,[a] and Peter Rutsch[a]
Dedicated to Professor Horst Kisch on the occasion of his 60th birthday
Keywords: Mixed donor sets / Nickel / Palladium / Rhodium / Tripodal ligands
Tripod ligands RC(CH2X)(CH2Y)(CH2Z) (X, Y, Z = NR2, PR2)
are accessible from α,β-unsaturated esters R(=CH2)COORЈ.
The key steps in this synthetic approach are Michael addi-
sults in square-planar complexes with the chelate cycles in
half-chair, twist-boat or boat conformations, depending on
the specific substitution pattern. Coordination through two
tions
of
amines
and
phosphanes
to
produce phosphane donors with the nitrogen donor acting as a dang-
RCH(COORЈ)(CH2X) (X = NR2, PR2) (2 and 3), followed by
hydroxymethylation with paraformaldehyde to result in
RC(COORЈ)(CH2OH)(CH2X) (X = NR2) (4). Standard trans-
formations of this C1-symmetric precursor allow for the syn-
ling arm is generally preferred throughout. Detail prepara-
tive procedures and complete characterisation by analytical
methods, including X-ray analysis of the coordination com-
pounds, are given.
thesis
of
tripod
ligands
such
as
PhC(CH2pz)-
(CH2PPh2)(CH2PMes) (11). Coordination of these ligands
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
with d8-metal ions [nickel(II), palladium(II), rhodium(
I)] re-
Introduction
transformation of these precursors into tripod ligands is
achieved with different kinds of groups R as well as differ-
ent kinds of donor functions X, Y, Z including NRRЈ.
While tripod ligands CH3C(CH2PR2)3 have been known
for a long time,[1] the synthesis of chiral tripodal ligands
CH3C(CH2X)(CH2Y)(CH2Z) (X, Y, Z ϭ donor groups) has
only been developed in the last decade.[2,3] Different syn-
thetic procedures were found to allow access to these com-
pounds. It was observed, however, that the introduction of
nitrogen donors in one or more of the X, Y, Z positions
called for quite specific procedures, dependent both on the
specific precursor and on the specific type of the NRRЈ
function to be introduced.[2b,2d,3g,3h,4] A general drawback
of the strategies so far published for the synthesis of
RC(CH2X)(CH2Y)(CH2Z) resides in the fact that there is
no free choice of the kind of the group R fixed at the back-
bone of the tripodal ligand. Only ligands with R ϭ H,[5]
CH3,[1Ϫ3] and CH2ORЈ[6] are easily available by the pub-
lished routes, while other functions such as benzyl, alkyl or
alkenyl groups have to be introduced into appropriate li-
gand precursors by specific reactions,[7] which do not, how-
ever, in general allow for the consequent introduction of
three different donor groups X, Y, and Z.
Scheme 1
Results and Discussion
Ligand Synthesis
α,β-Unsaturated esters RC(ϭCH2)COORЈ are known to
undergo 1,4-addition reactions with different types of HX
compounds, including RRЈNH[8] and R2PH.[9] By applica-
In search of a solution for both of these problems we
studied α,β-unsaturated esters RC(ϭCH2)COORЈ as poten-
tial precursors (see Scheme 1). We now report that the
[a]
Anorganisch-Chemisches Institut der Universität Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: (internat.) ϩ 49-(0)6221/545707
E-mail: g.huttner@indi.aci.uni-heidelberg.de
Scheme 2
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
DOI: 10.1002/ejic.200200448
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R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
FULL PAPER
tion of this strategy, compounds 2 and 3 are obtained from of RЈЈ and NRRЈ in 2 (see Exp. Sect.), while KOtBu was
compounds 1 in high yields (see Scheme 2 and Exp. Sect.). found to be ineffective in this kind of reaction.
The ester function in compounds 2 offers itself for trans-
formation into a CH2XЈ donor entity in later steps of the
reaction. In order to obtain tripod ligands, an additional
functionalisable CH2XЈЈ group has to be added to the cen-
tral position of 2 in such a way that it forms the third ‘‘leg’’
of the desired tripod ligand. Hydroxymethylation is the ob-
vious solution. Reactions of this type are generally quite
efficient, but only in the absence of a CH2NRRЈ substituent
and with aldehyde or ketone functions, rather than an ester
function as present in 2.[10] Unactivated esters of the general
Scheme 4
type of framework as present in 2 Ϫ that is, disubstituted
in the α,αЈ-position Ϫ are only rarely found to be suitable
precursors for hydroxymethylation.[11] Hydroxymethylation
The yields of the transformations of 2 into 4 are between
is generally only successful if they are activated by an addi- 45 and 65% and correspond well to yields reported for the
tional electron-withdrawing group, such as in malonic ester hydroxymethylation of RCH2CORЈ by paraformal-
derivatives, and this type of reaction has accordingly been dehyde.[10]
used as a key step for the construction of specific tripod li-
In the case of 1a, Michael addition and hydroxymethyl-
ation could be performed in a one-pot reaction with pyra-
gands.[3d,7b,7c]
With compound 2, however, it was found that even sub- zole as the HNRRЈ reagent (see Scheme 5),[13] compound
stitution under basic conditions by chloromethyl benzyl 4d being obtained in 65% yield in this way. This type of
ether failed (see Scheme 3).
one-pot reaction was, however, only successful with 1a as
the Michael acceptor and pyrazole as the Michael donor,
and so only 4d Ϫ and not 4aϪ4c Ϫ is accessible by this
simple route.
Scheme 3
Scheme 5
While the direct introduction of a CH2OH group in the
form of formaldehyde or paraformaldehyde is reported to
The compounds 2؊4 have been fully characterised by ele-
1
be less efficient[10,12] than the synthesis of its protected form mental analysis, mass spectrometry and H and 13C NMR
by use of ClCH2OBzl, it still proved possible to find suitable spectroscopy (see Tables 4, 6, 7 and Exp. Sect.).
conditions for the synthesis of 4 from 2 by just this route
Reduction of the ester function in 4 afforded the diols
(Scheme 4). The key to obtaining the necessary reactivity 5, which Ϫ after activation by mesyl chloride Ϫ could be
was the nature of the deprotonation of 2; such depro- transformed into the diphosphanes 6 (see Scheme 6). These
tonation to afford the corresponding enolate is possible diphosphanes are tripod ligands containing two P and one
with NaH/DMF at 20 °C or LDA/THF at Ϫ70 °C. The N donor functions. Their identity was established by their
choice of either one of these bases depends on the nature elemental analyses, mass spectra and NMR spectra (see
Scheme 6
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C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
FULL PAPER
Tables 5Ϫ7 and Exp. Sect.) and by the formation of tripod worked out for the transformation 7b Ǟ 9 Ǟ 10 Ǟ 11 (see
metal complexes (see Coordination Chemistry). Scheme 9). The two phosphide substitution steps give yields
Since compounds 4 already contain three different func- normal for this type of process, with an overall yield of 11
tionalities, their transformation into chiral racemic tripod of 35% based on 7b. To avoid unwanted side reactions dur-
ligands should be possible. The activation of the OH group ing these substitution steps (internal cyclization) the reac-
of 4 by mesyl chloride was found to be quite inefficient in tion temperatures have to be thoroughly controlled (see
this respect: either the yields were very low or, as in the case Exp. Sect., for elemental analysis, NMR spectra, and mass
of 4d, formal elimination of the CH2pz group occurred, to spectra of compounds 7؊11, see Tables 4Ϫ7).
give 3 as the main product (see Scheme 7).
Coordination Chemistry
Tripod ligands containing nitrogen and phosphorus
donor functions in one and the same ligand are known to
form tripodal coordination compounds. This has been dem-
onstrated with Mo(CO)3 as the coordinated entity.[3g,3h]
With d8-ions as the metal constituents, square-planar coor-
dination of the metal ion is generally preferred and is ex-
clusively observed for tripod ligands containing a P,P,N
Scheme 7
donor set.[4b,15] With this type of η2-coordination of a tri-
pod ligand containing different types of donor functions, it
is not clear a priori which kinds of donor functions will
The mechanism of this reaction has not yet been studied,
be coordinated.
but MePPh2 and MeP(ϭO)Ph2 have been observed (31P
Compounds 6, 8, and 11 offer the opportunity to address
this question. The coordination behaviour of this type of
NMR, GC/MS) as accompanying products.
In contrast, activation by means of the Appel reaction[14]
compounds with respect to nickel(), palladium(), and
transformed 4 into 7 in fair yields (see Scheme 8). The direct
rhodium() was therefore analysed.
substitution of the chloride function of 7 by diphenylphos-
phide was successful for 7a, while with 7b, with its pyrazolyl
functionality, sluggish reactivity, and partial decomposition
was observed. For 7a, with its diethylamine function, a clear
transformation into 8 (63% yield) was accomplished (see
Scheme 8).
A more general route is based on the reduction of the
ester group as the first step. The activation of the resulting
alcohol function by mesyl chloride was followed by the sub-
stitution of the mesylate by diarylphosphide. The remaining
chlorine function could then be substituted by a different
diarylphoshide. The reaction sequence has been fully Scheme 10
Scheme 8
Scheme 9
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
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R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
FULL PAPER
Figure 1. Two views of the X-ray structure of compound 12a (left, half-chair conformation) and 12b (right, twist-boat conformation);
top: general view; bottom: view showing the conformation of the six-membered chelate cycle (phenyl groups are not shown for the sake
of clarity)
Tripod ligands 6a, 6b, and 11 each contain a P,P,N donor use of [(nbd)RhCl]2, give the readily crystallised, diamag-
set. Complexation with aqueous NiCl2 resulted in orange netic compounds 13 (yellow) and 14·PF6 (orange)
to red, square-planar nickel() complexes 12 in which the (Scheme 11).
two phosphane functions are coordinated exclusively while
NMR (1H, 13C, 31P) spectra of 13 reveal the expected
the nitrogen-functionalised ‘‘leg’’ is a dangling substituent resonances as sharp signals even at 30 °C (see Tables 4 and
(see Scheme 10). The same type of coordination behaviour 6). The ethyl groups of the NEt2 entity are diastereotopic,
has already been observed for other ligands of the type consistent with the proposed structure. Diastereotopic dif-
RC(CH2PPh2)2(CH2X). Phosphorus coordination is pre- ferentiation of the ethyl groups in 14·PF6 is only observable
ferred over coordination of ligand groups X such as NRRЈ, below Ϫ30 °C (see Tables 4 and 6), while above this tem-
OH, OMe, and SR.[3e,16]
perature some dynamic process gives rise to considerable
The structures of 12a and 12b as determined by X-ray broadening of the peaks such that the diastereotopic differ-
crystallography are shown in Figure 1. entiation is no longer observable. The dynamic process is
Interestingly, the conformations of the chelate cycles are presumably due to a change in the conformation of the che-
different for the two compounds Ϫ being a half-chair form late cycle.[17,18]
in 12a and a twist-boat form in 12b (see Table 1). The rela-
tive stability of these types of conformations has recently dination of the palladium atom and reveals that the chelate
been analysed thoroughly.[17]
cycle has a twist-boat conformation (see Figure 2, Table 1).
X-ray analysis of 13 establishes the square-planar coor-
Compound 8 has three different potential donor substitu- The X-ray structure of 14؉ similarly establishes the pseudo-
ents within the tripodal framework: coordination is con- square-planar coordination of the rhodium atom. The che-
ceivable for the PPh2, the NEt2 and the ester groups. Com- late cycle is found to have the unconventional boat form,
pound 8 was found to react with (dme)NiCl2 to give a vi- with the sterically more demanding methoxycarbonyl group
olet, paramagnetic compound, which Ϫ due to its insuffi- axial and the methyl group in the equatorial position (see
cient crystallisation properties Ϫ could not be obtained in Figure 2, Table 1). The methoxycarbonyl group is orien-
analytically pure form. In contrast, palladium(), intro- tated such that the normal to its plane points toward the
duced by use of (cod)PdCl2, and rhodium(), introduced by rhodium centre (see Figure 2). The distance between the
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Eur. J. Inorg. Chem. 2003, 1681Ϫ1693

C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
FULL PAPER
Table 1. Selected bond lengths [pm], bond angles [°] and torsion angles [°] of compounds 12a, 12b, 13, and 14
12a [M ϭ Ni][a]
12b [M ϭ Ni][a]
13 [M ϭ Pd][a]
14·PF6 [M ϭ Rh][a]
MϪCl
MϪP
MϪN
MϪC
219.4(1); 221.6(1)
215.8(1); 216.8(1)
Ϫ
Ϫ
219.8(1); 219.9(1)
215.1(1); 215.7(1)
Ϫ
Ϫ
229.8(1)[b]
221.8(1)
213.8(1)
Ϫ
;
239.1(1)[c]
Ϫ
228.8(1)
223.8(2)
210.7(2)[b]
;
212.3(2)[b]
223.4(2)[c]; 224.0(2)[c]
P1ϪMϪP2/N
Cl1ϪMϪCl2
P1ϪMϪCl1
P2/NϪMϪCl2
P1ϪMϪCl2
96.1(1)
92.1(1)
85.9(1)
86.2(1)
175.1(1)
176.3(1)
91.8(1)
94.5(1)
87.4(1)
87.6(1)
170.9(1)
172.4(1)
93.5(1)
89.9(1)
85.6(1)
92.4(1)
167.1(1)
172.9(1)
91.1(1)
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
P2/NϪMϪCl1
Chelate cycle[d]
MϪ2Ϫ3Ϫ4
2Ϫ3Ϫ4Ϫ5
half-chair (2,6 ϭ P)
ϩ44.1(4)
Ϫ72.2(5)
ϩ67.2(5)
Ϫ36.9(4)
ϩ8.4(2)
λ-twist boat (2,6 ϭ P)
ϩ67.9(2)
Ϫ35.3(2)
Ϫ30.0(2)
ϩ65.0(2)
Ϫ25.4(1)
Ϫ25.8(1)
Ϫ47.7
λ-twist boat (2 ϭ P, 6 ϭ N)
ϩ59.6(3)
Ϫ30.8(3)
Ϫ40.1(4)
ϩ71.0(3)
Ϫ27.6(2)
Ϫ25.7(1)
Ϫ51.3
boat (2 ϭ P, 6 ϭ N)
ϩ13.3(2)
Ϫ74.0(2)
ϩ64.2(2)
ϩ7.6(2)
Ϫ48.8(2)
ϩ34.7(2)
Ϫ8.3
3Ϫ4Ϫ5Ϫ6
4Ϫ5Ϫ6ϪM
5Ϫ6ϪMϪ2
6ϪMϪ2Ϫ3
3Ϫ2Ϫ6Ϫ5
Ϫ10.8(2)
Ϫ2.3
[a]
[b]
[c]
[d]
Standard deviations in units of the least significant digit are given in each case. trans to N. trans to P. A consistent numbering
scheme (torsion angles) for all the compounds as depicted below is used for the sake of easier comparison:
phosphorus-containing saturated chelate cycles in
mind,[17,18] equilibria between different ring conformations
are the most probable explanation for the temperature de-
pendence of the behaviour of the NMR spectra of 14·PF6.
Conclusion
It has been shown that α,β-unsaturated esters RC(ϭ
CH2)COORЈ may serve as starting materials for the syn-
thesis of tripod ligands RC(CH2X)(CH2Y)(CH2Z). The
procedure allows for the incorporation of different types of
substituents R in the backbone and also allows the intro-
duction of donor functions X ϭ NR2 in the presence of
Scheme 11
rhodium atom and the carboxy group (RhϪO: 348.7 pm different potential phosphorus donor functions (Y, Z).
and 350.2 pm) is too large to be interpreted in terms of
Ligands of this type Ϫ containing a P,P,N donor set Ϫ
any direct bonding between these partners while it is short coordinate to d8-metal ions through their two phosphorus
enough for some type of secondary interaction to be as- donor groups, resulting in a square-planar coordination
sumed (see Table 2).
with the amine function acting as a dangling arm.
Ligands containing a P,N,O donor set (O ϭ part of a
Boat conformations as observed for 14؉ have not yet
been found in crystal structures of rhodium complexes with carboxy group) form complexes in which P,N donors serve
six-membered phosphorus-containing saturated chelate as ligands in six-membered chelate cycles. For the d8-metal
cycles, while their inherent relative stability in some cases ions PdII and RhI the coordination is square-planar. The O
has been indicated by a thorough molecular dynamics ana- donor is not involved in direct bonding to the metal atom
lysis.[17b] With the dynamic behaviour of six-membered but may engage in secondary interaction with it.
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
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R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
FULL PAPER
Figure 2. Two views of the X-ray structure of compound 13 (left, twist-boat conformation) and the cation 14؉ (right, boat conformation);
top: general view; bottom: view showing the conformation of the six-membered chelate cycle (phenyl groups are not shown for the sake
of clarity)
Experimental Section
Table 2. Selected bond lengths [pm], bond angles [°] and torsion
angles [°] of the ester groups in compounds 13 and 14
General Remarks: All manipulations involving phosphanes were
carried out under argon by use of standard Schlenk techniques.
All solvents were dried by standard methods[19] and distilled under
argon. The solvents CDCl3 and CD2Cl2 used for NMR spectro-
scopic measurements were degassed by three successive ‘‘freeze-
13 [M ϭ Pd][a]
14·PF6 [M ϭ Rh][a]
C5ϪO1 (CϭO)
C5ϪO2 (CϪO)
C6ϪO2 (CϪO)
MϪC5
MϪO1
MϪO2
119.9(4)
134.6(4)
145.8(4)
485.4
559.2
533.3
120.0(3)
133.7(3)
145.1(3)
313.9
348.7
350.2
˚
pump-thaw’’ cycles and dried over 4 A molecular sieves. NMR:
Bruker Advance DPX 200 at 200.12 MHz (1H); 50.323 MHz
(13C{1H}); 81.015 MHz (31P{1H}); T ϭ 303 K unless stated other-
wise; chemical shifts (δ) with respect to CDCl3 (1H: δ ϭ 7.27; 13C:
δ ϭ 77.0 ppm) and CD2Cl2 (1H: δ ϭ 5.32 ppm; 13C: δ ϭ 53.5 ppm)
as internal standards. 31P chemical shifts (δ) with respect to 85%
H3PO4 (31P: δ ϭ 0 ppm) as external standard. FT-IR: Biorad Exca-
libur FTS 3000 spectrophotometer (samples in solutions between
CaF2 windows). MS: Finnigan MAT 8230. EI (70 eV). FAB
(xenon; matrix: 4-nitrobenzyl alcohol). Melting points: Gallen-
kamp MFB-595010; uncorrected values. Elemental analyses:
Microanalytical Laboratory of the Organic-Chemical Institute,
University of Heidelberg.
C2ϪC5ϪO1
C2ϪC5ϪO2
O1ϪC5ϪO2
C6ϪO2ϪC5
124.6(3)
111.6(3)
123.6(3)
116.7(3)
123.9(2)
112.6(2)
123.3(2)
116.6(2)
C6ϪO2ϪC5ϪO1
C6ϪO2ϪC5ϪC2
Ϫ3.4(5)
Ϫ0.1(3)
ϩ3.5(3)
Ϫ8.7(2)
[a]
Standard deviations in units of the least significant digit are
given in each case.
Crystallographic Structure Determinations: Suitable crystals were
taken directly out of the mother liquor, immersed in perfluorinated
polyether oil, and fixed to a glass capillary. The measurements were
carried out with an EnrafϪNonius Kappa CCD diffractometer,
with graphite-monochromated Mo-Kα radiation used throughout.
The conformations of the six-membered chelate cycles
comprise the conventional half-chair and twist-boat forms
as well as the unconventional boat form.
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C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
Table 3. Crystallographic data of compounds 12a, 12b, 13, and 14
FULL PAPER
Compound
12a
12b
13
14·PF6
Empirical formula (without solvate)
Formula mass [g/mol]
Solvate
Crystal size [mm]
Crystal system
Space group
Lattice constants:
a [pm]
C33H39Cl2NNiP2
641.2
1 CH2Cl2; 0.5H2O
0.15ϫ0.15ϫ0.05
orthorhombic
Pca21 (no. 29)
C37H34Cl2N2NiP2
698.2
Ϫ
0.10ϫ0.10ϫ0.10
monoclinic
P21/n (no. 14)
C22H30Cl2NO2PPd
548.8
Ϫ
0.10ϫ0.02ϫ0.02
monoclinic
P21/n (no. 14)
C29H38F6NO2P2Rh
711.5
Ϫ
0.20ϫ0.20ϫ0.15
orthorhombic
Pcba (no. 61)
2153.9 (4)
1124.4 (2)
1411.8 (3)
90
3419 (1)
4
1075.6 (2)
1900.5 (4)
1642.5 (3)
97.54 (3)
3328 (1)
4
1252.3 (3)
1383.4 (3)
1354.3 (3)
92.85 (3)
2343 (1)
4
2218.7 (4)
1621.6 (3)
1625.7 (3)
90
5849 (1)
8
b [pm]
c [pm]
β [°]
V [106·pm3]
Z
dX [g·cmϪ3
T [K]
]
1.426
200
1.393
200
1.558
293
1.616
200
Scan range [°]
3.6 Յ 2θ Յ 54.9
ω-scan, ∆ω ϭ 1.0°
30 sec/frame
7860
7544
6782
I Ն 2σ
348
1.42
3.3 Յ 2θ Յ 54.0
ω-scan, ∆ω ϭ1.0°
5 sec/frame
14564
7251
6095
I Ն 2σ
400
0.72
3.7/10.3
4.2 Յ 2θ Յ 60.2
ω-scan, ∆ω ϭ1.0°
10 sec/frame
11921
6845
4985
I Ն 2σ
257
0.89
4.6/11.4
3.7 Յ 2θ Յ 55.8
ω-scan, ∆ω ϭ1.0°
10 sec/frame
13968
6966
5451
I Ն 2σ
409
0.40
Method
Scan speed
No. of measured reflections
No. of unique reflections
No. of observed reflections
Observation criterion
No. of param. refined
Resid. el. dens. [10Ϫ6e·pmϪ3
]
R1/Rw [%] (refinement on F2)
6.6/15.2
3.4/8.5
1
Table 4. Chemical shifts (δ values), integrals [x H], and coupling constants J in the H NMR spectra of 4, 7, 8, 13, and 14
No.[a]
4a[b]
4b[b]
4c[b]
4d[b]
7a[b]
7b[b]
8[b]
CH2N [2 H]
CH2X [2 H]
OCH3 [3 H] CqCH3 [3 H] OH [1 H] Aryl-H
Others
2.84 d, 3.49 d, 4.40 br. s,
2JH,H ϭ 13.9
X ϭ OH
2.49 d, 3.02 d, 3.61 d, 3.81 d,
2JH,H ϭ 14.0
2.41 d, 3.02 d, 3.68 d, 3.91 d,
2JH,H ϭ 13.8
4.61 d, 5.02 d, 3.93 d, 4.17 d,
2JH,H ϭ 14.4
2.64 d, 2.73 d, 3.69 d, 3.79 d,
2JH,H ϭ 14.2
4.80 d, 5.13 d, 4.06 d, 4.34 d,
2JH,H ϭ 14.1
2.67 d, 2.85 d, 2.35 d, 2.50Ϫ2.66 m,
2JH,H ϭ 13.7
2.77 d, 2.99 d, 2.43 d, 3.20 d,
2JH,H ϭ 14.3 2JH,H ϭ 16.0, X ϭ PPh2
3.70 s
3.63 s
3.70 s
3.74 s
3.70 s
3.81 s
3.49 s
3.74 s
4.09 s
Ϫ
6.49 br. s 7.29 m [5 H]
1.38Ϫ1.45 m, 1.54 br. s, 2.42Ϫ2.69 m
[10 H], piperidine-H
0.93 t, 2.40Ϫ2.60 m [10 H],
3JH,H ϭ 7.1, NEt2
1.04 s
1.07 s
Ϫ
5.44 br. s
5.55 br. s
Ϫ
Ϫ
2JH,H ϭ 11.3, X ϭ OH
1.36Ϫ1.42 m, 1.49Ϫ1.52 m,
2.38Ϫ2.54 m [10 H], piperidine-H
6.22 t, 7.31 d, 7.55 d [3 H],
3JH,H ϭ 2.0, pyrazole-H
0.95 t, 2.53 q [10 H],
2JH,H ϭ 11.0, X ϭ OH
4.61 br. s 7.33Ϫ7.39 m [5 H]
2JH,H ϭ 12.2, X ϭ OH
1.25 s
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
Ϫ
2JH,H ϭ 10.8, X ϭ Cl
3JH,H ϭ 7.1, NEt2
7.07Ϫ7.11 m [2 H], 6.12 t, 6.99 d, 7.52 d [3 H],
7.35Ϫ7.38 m [3 H]
3JH,H ϭ 2.0, pyrazole-H
7.35Ϫ7.51 m [10 H] 0.97t, 2.50Ϫ2.66m [10 H],
3JH,H ϭ 7.1, NEt2
7.45Ϫ7.73 m [8 H], 1.44 t, 1.75 t, 2.70Ϫ4.30 m [10 H],
8.13Ϫ8.24 m [2 H]
2JH,H ϭ 10.9, X ϭ Cl
1.25 s
1.04 s
1.43 s
2JH,H ϭ 10.8, X ϭ PPh2
13[c]
3JH,H ϭ 7.1, NEt2
14[c] [d] 2.26 d, 3.50 d, 2.47 d, 3.33 d,
2JH,H ϭ 14.7 2JH,H ϭ 15.7, X ϭ PPh2
7.32Ϫ7.63 m [8 H], 1.03 t, 1.62 t, 2.05Ϫ3.10 m [10 H],
7.86Ϫ7.95 m [2 H]
3JH,H ϭ 7.1, NEt2
1.53 br. s,[e] 2.83 br. s,[f]
3.71 br. s,[f] 3.77 br. s,[g]
4.00 br. s,[g] 5.20 br. s,[f] 5.32 br. s,[f]
[8 H], norbornadiene-H
[a]
[b]
[c]
s ϭ singlet, d ϭ doublet, t ϭ triplet, m ϭ multiplet, br. s ϭ broad signal; coupling constants in Hz.
Solvent CHCl3. Solvent
[d]
[e]
[f]
[g]
CH2Cl2. Measuring temperature Ϫ40 °C. CH2 group. Olefinic CH group. Bridgehead CH group.
The data were processed with the standard Nonius software,[20] and
the calculations were performed with the SHELXT PLUS software
package. Structures were solved by direct methods with the
SHELXS-97 program and refined with the SHELXL-97 pro-
gram.[21] Graphical handling of the structural data during solution
were refined by full-matrix, least-squares calculations. Data relating
to the structure determinations are collected in Table 3. Figures 1
and 2 were prepared with WinRay-32.[23] Crystallographic data (ex-
cluding structure factors) for the structures reported in this paper
have been deposited with the Cambridge Crystallographic
and refinement was performed with XMPA.[22] Atomic coordinates Data Centre as supplementary publication nos. CCDC-191480
and anisotropic thermal parameters of the non-hydrogen atoms to -191483. Copies of the data can be obtained free of charge
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1687

R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
Table 5. Chemical shifts (δ values), integrals [x H] and coupling constants J in the H NMR spectra of 5, 6, and 9؊12
FULL PAPER
1
No.[a] CH2N [2 H] CH2X
5a[b] 2.52 s
CH2Y
CqCH3 [3 H] OH [2 H]
Aryl-H
Others
2
3.58 pt [4 H], JH,H ϭ 11.3, X ϭ Y ϭ OH
3.90 br. s [4 H], X ϭ Y ϭ OH
0.79 s
Ϫ
4.97 br. s
Ϫ
1.03 t, 2.54 q [10 H],
3JH,H ϭ 7.1, NEt2
5b[b] 4.72 s
2.30Ϫ3.10 br. s 7.28Ϫ7.44 m [5 H] 6.19 t, 7.09 d, 7.55 d [3 H]
3JH,H ϭ 2.0 pyrazole-H
6a[b] 2.54 s
2.45 m [4 H], X ϭ Y ϭ PPh2
0.98 s
Ϫ
Ϫ
7.33Ϫ7.50 m [20 H] 0.99 t, 2.64 q [10 H],
3JH,H ϭ 7.0, NEt2
6.86Ϫ7.01 m [5 H], 6.06 t, 6.90 d, 7.49 d [3 H],
6b[b] 5.04 s
2.81 d, 2.97 d [4 H], JH,H ϭ 14.3, X ϭ Y ϭ PPh2
Ϫ
2
3
7.17Ϫ7.34 m [20 H] JH,H ϭ 2.0, pyrazole-H
9[b] 4.56 d, 4.65 d, 3.75 d, 3.94 d [2 H],
3.80 d, 3.97 d [2 H],
2JH,H ϭ 11.5, Y ϭ Cl
4.07 d, 4.24 d [2 H],
2JH,H ϭ 11.5, Y ϭ Cl
Ϫ
4.31 br. s [1H] 7.28Ϫ7.39 m [5 H] 6.19 t, 7.15 d, 7.53 d [3 H],
3JH,H ϭ 2.0, pyrazole-H
2
2JH,H ϭ 14.3 JH,H ϭ 12.0, X ϭ OH
10[b] 4.57 d, 4.96 d, 2.79 br. s [2 H],
2JH,H ϭ 14.0 X ϭ PPh2
Ϫ
Ϫ
7.14Ϫ7.35 m [15 H] 6.14 t, 7.09 d, 7.53 d [3 H],
3JH,H ϭ 2.0, pyrazole-H
6.57Ϫ6.60 m [4 H], 2.18 br. s [18 H],
6.77Ϫ7.37 m [15 H] aryl-CH3,
6.01 t, 6.77Ϫ7.37 m, 7.49 d
11[b] 4.95 br. s
2.85 d, 2.95 d [2 H],
2JH,H ϭ 14.4, X ϭ PPh2 JH,H ϭ 14.4, Y ϭ PMes2
3.09 d, 3.36 d [2 H],
Ϫ
Ϫ
2
3
[3 H], JH,H ϭ 2.0,
pyrazole-H
2
12a[c] 2.15 s
12b[c] 3.87 s
2.22 d, 3.80 br. s [4 H], JH,H ϭ 15.2, X ϭ Y ϭ PPh2 0.27 s
Ϫ
Ϫ
7.40Ϫ7.73 m [16 H], 0.91 t, 2.49 q [10 H],
8.48Ϫ8.51 m [4 H] 3JH,H ϭ 7.0, NEt2
6.81Ϫ7.13 m [5 H], 5.91 t, 6.40 d, 7.33Ϫ7.67 m
2
2.74 d, 2.99 d [4 H], JH,H ϭ 15.1, X ϭ Y ϭ PPh2
Ϫ
3
7.40Ϫ8.20 m [20 H] [3 H], JH,H ϭ 2.0,
pyrazole-H
[a]
[b]
s ϭ singlet, d ϭ doublet, t ϭ triplet, m ϭ multiplet, br. s ϭ broad signal, pt ϭ pseudo-triplet; coupling constants in Hz.
Solvent
[c]
CHCl3. Solvent CH2Cl2.
3
on application to the CCDC, 12 Union Road, Cambridge
(CDCl3): δ ϭ 0.93 ppm (t, 6 H, NCH2CH3, JH,H ϭ 7.0 Hz), 1.08
CB2 1EZ, UK [Fax: (internat.)
deposit@ccdc.cam.ac.uk].
ϩ
44-1223/336033; E-mail:
(d, 3 H, CHCH3, 3JH,H ϭ 7.1 Hz), 2.30 (dd, 2JH,H ϭ 12.7, 3JH,H ϭ
6.3 Hz, 1 H, CH2NEt), 2.34 (q, JH,H ϭ 7.0 Hz, 4 H, NCH2CH3,),
3
2.50Ϫ2.73 (m, 2 H, CHCH3 and CH2NEt), 3.62 (s, 3 H, OCH3).
13C NMR (CDCl3): δ ϭ 12.3 ppm (s, NCH2CH3), 15.8 (s, CHCH3),
39.4 (s, CHCH3), 47.8 (s, NCH2CH3), 51.7 (s, OCH3), 57.3 (s,
CH2NEt), 177.0 (s, CϭO).
Materials: Silica gel (Kieselgel 32Ϫ63 µm, ICN Biomedicals
GmbH) used for chromatography was degassed at 1 mbar for 24 h
and saturated with argon. A solution of nBuLi in hexane (2.5 )
[25]
was used for deprotonations. HPPh2,[24] HPMes2 and methyl 2-
Methyl 2-Methyl-3-(1-piperidino)propanoate (2c): Starting ma-
terials: 1b, piperidine. The mixture was heated to 90 °C for 6 h.
Yield: 76.0 g (0.41 mol, 82%), b.p. 54 °C (0.2 mbar). 1H NMR
phenylacrylate (1a)[26] were prepared according to or by adaptation
of literature procedures. All other chemicals were obtained from
commercial suppliers and used without further purification.
Boiling range of the petroleum ether used: 40Ϫ60 °C. For 1H NMR
data see Tables 4 and 5, for 13C NMR data see Table 6, and for
analytical data see Table 7.
3
(CDCl3): δ ϭ 1.10 ppm (d, JH,H ϭ 7.0 Hz, 3 H, CHCH3),
1.35Ϫ2.33 (m, 10 H, piperidine-H), 2.21 (dd, 2JH,H ϭ 12.3, 3JH,H ϭ
2
3
6.3 Hz, 1 H, CH2N), 2.53 (dd, JH,H ϭ 12.3, JH,H ϭ 8.3 Hz, 1 H,
3
CH2N), 2.62 (sext, 1 H, JH,H ϭ 7.1 Hz, CHCH3), 3.63 (s, 3 H,
OCH3). 13C NMR (CDCl3): δ ϭ 16.0 ppm (s, CHCH3), 24.8, 26.3,
55.0 (3 ϫ s, piperidine-C), 38.3 (s, CHCH3), 51.7 (s, OCH3), 62.7
(s, CH2N), 177.0 (s, CϭO).
Ligand Syntheses
General Procedure for the Synthesis of 2: The α,β-unsaturated ester
1a or 1b (0.5 mol) was mixed with the secondary amine (1.1 equiv.),
and hydroquinone (1.0 g) in the case of 1b. The solution was heated
and, after cooling, the crude product was distilled under reduced
pressure through a 15-cm Vigreux column, yielding the β-amino
esters 2 as colourless liquids.
Methyl 2-Methyl-3-(1-pyrazolyl)propanoate (2d): Starting materials:
1b, pyrazole. The mixture was heated under reflux for 60 h. Yield:
1
68.4 g (0.41 mol, 82%), b.p. 48 °C (0.2 mbar). H NMR (CDCl3):
3
δ ϭ 1.07 ppm (d, JH,H ϭ 7.1 Hz, 3 H, CHCH3), 3.02 (sext, 1 H,
2
3JH,H ϭ 7.1 Hz, CHCH3), 3.57 (s, 3 H, OCH3), 4.08 (dd, JH,H
ϭ
Methyl 2-Phenyl-3-(1-piperidino)propanoate (2a): Starting ma-
terials: 1a, piperidine. The mixture was heated to 70 °C for 1 h.
Yield: 103.8 g (0.42 mol, 84%), b.p. 84 °C (0.1 mbar). 1H NMR
(CDCl3): δ ϭ 1.43Ϫ2.61 ppm (m, 10 H, piperidine-H), 2.50Ϫ2.61
13.7, 3JH,H ϭ 6.5 Hz, 1 H, CH2N), 4.34 (dd, 2JH,H ϭ 13.7, 3JH,H ϭ
7.5 Hz, 1 H, CH2N), 6.11, 7.30, 7.40 (t, 2ϫd, 3 H, 3JH,H ϭ 2.0 Hz,
pyrazole-H). 13C NMR (CDCl3): δ ϭ 15.1 ppm (s, CHCH3), 41.0
(s, CHCH3), 52.2 (s, OCH3), 54.5 (s, CH2N), 105.6, 130.2, 140.0 (3
ϫ s, pyrazole-C), 174.9 (s, CϭO). For further analytical data of
2aϪ2d, see Table 7.
2
3
(m, 1 H, CH2N), 3.21 (dd, JH,H ϭ 12.6, JH,H ϭ 10.2 Hz, 1 H,
3
3
CH2N), 3.71 (s, 3 H, OCH3), 3.90 (dd, JH,H ϭ 4.6, JH,H
ϭ
10.2 Hz, 1 H, PhCH), 7.31Ϫ7.35 (m, 5 H, aromat. H). 13C NMR
(CDCl3): δ ϭ 24.8 ppm, 26.5, 55.0 (3 ϫ s, piperidine-C), 50.4 (s,
PhCH), 52.3 (s, OCH3), 62.9 (s, CH2N), 127.7Ϫ138.3 (m, aromat.
C), 174.4 (s, CϭO).
Methyl 3-(Diphenylphosphanyl)-2-phenylpropanoate (3): Compound
1a (1.62 g, 10 mmol) and diphenylphosphane (1.86 g, 10 mmol)
were dissolved in DMF (30 mL). NaH (60% dispersion in mineral
oil, 200 mg, 5 mmol) was added, and the reaction mixture was
stirred at 25 °C for 18 h and then quenched by addition of deoxy-
Methyl 3-(Diethylamino)-2-methylpropanoate (2b): Starting ma-
terials: 1b, diethylamine. The mixture was heated under reflux for
72 h. Yield: 41.6 g (0.24 mol, 48%), b.p. 29 °C (0.2 mbar). 1H NMR genated water (10 mL). The product was extracted with diethyl
1688
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693

C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
FULL PAPER
Table 6. Chemical shifts (δ values) and coupling constants J in the 13C{1H} NMR spectra of 4؊14
No.[a] CH2N
CH2X
CH2Y
OCH3 CqCH3
CqCH3
CϭO
Aryl-C
Others
4a[b] 66.9
67.4, X ϭ OH
Ϫ
52.6
55.3
Ϫ
174.8
126.4Ϫ140.4 m 24.1, 26.8, 56.9,
piperidine-C
4b[b] 61.0
4c[b] 66.2
68.8, X ϭ OH
69.1, X ϭ OH
Ϫ
Ϫ
52.1
52.2
47.8
47.6
20.8
21.0
176.9
176.8
Ϫ
Ϫ
11.7, 48.4, NEt2
24.1, 26.7, 56.8,
piperidine-C
4d[b] 55.5
63.2, X ϭ OH
Ϫ
52.9
58.3
Ϫ
173.7
126.9Ϫ138.9 m 105.8, 131.9, 140.0,
pyrazole-C
12.1, 49.3, NEt2
127.0Ϫ140.7 m 105.8, 131.7, 139.8,
pyrazole-C
128.6Ϫ141.0 m 12.3, 49.0, NEt2
5a[b] 62.4
5b[b] 55.0
68.8, X ϭ Y ϭ OH
66.4, X ϭ Y ϭ OH
Ϫ
Ϫ
40.1
50.0
19.9
Ϫ
Ϫ
Ϫ
6a[b] 65.5 t,
40.2 dd, X ϭ Y ϭ PPh2,
Ϫ
Ϫ
41.0 t,
2JC,P ϭ 12.5 JC,P ϭ 9.7
46.5 t,
2JC,P ϭ 16.2
49.7
26.6 t,
Ϫ
Ϫ
3JC,P ϭ 7.7
1JC,P ϭ 15.5; JC,P ϭ 8.7
3
3
6b[b] 59.5 t,
39.1 dd, X ϭ Y ϭ PPh2,
Ϫ
126.9Ϫ142.0 m 105.3, 131.3, 139.3,
3JC,P ϭ 11.7
1JC,P ϭ 18.5; JC,P ϭ 10.2
pyrazole-C
12.1, 48.4, NEt2
126.5Ϫ137.9 m 105.7, 131.4, 140.5,
pyrazole-C
128.7Ϫ140.2 m 12.1, 48.5, NEt2
3
7a[b] 59.7
7b[b] 54.3
49.5, X ϭ Cl
Ϫ
52.1
53.2
19.9
Ϫ
175.5
172.5
Ϫ
46.6, X ϭ Cl
Ϫ
57.6
8[b]
9[b]
64.3 d,
37.6 d, X ϭ PPh2,
Ϫ
51.7
Ϫ
48.2 d,
2JC,P ϭ 13.2 JC,P ϭ 11.1
50.3
22.5 d,
177.3
Ϫ
3JC,P ϭ 9.1 JC,P ϭ 15.6
1
3
55.8
65.6, X ϭ OH
47.9, Y ϭ Cl
Ϫ
Ϫ
Ϫ
127.1Ϫ139.8 m 106.0, 131.8, 140.1,
pyrazole-C
10[b] 57.8 d,
38.0 d, X ϭ PPh2, 49.5 d, Y ϭ Cl,
Ϫ
48.2 d,
Ϫ
127.3Ϫ140.2 m 105.6, 131.2, 140.2,
pyrazole-C
3JC,P ϭ 9.1 JC,P ϭ 18.1
3JC,P ϭ 14.6
2JC,P ϭ 16.1
47.9 t,
1
5
11[b] 59.8 t,
40.9 dd, X ϭ PPh2, 34.7 dd ,Y ϭ PMes2, Ϫ
Ϫ
127.3Ϫ140.2 m 21.1 d, JC,P ϭ 2.8, p-CH3,
3JC,P ϭ 11.5 JC,P ϭ 16.5,
1JC,P ϭ 21.0,
3JC,P ϭ 10.1
2JC,P ϭ 20.1
23.2 d, 23.8 d, JC,P ϭ 14.5,
o-CH3,
105.2, 130.5, 139.2,
1
3
3JC,P ϭ 8.7
pyrazole-C
12a[c] 70.4
12b[c] 62.9
34.7 br. s, X ϭ Y ϭ PPh2
30.6 br. s, X ϭ Y ϭ PPh2
Ϫ
Ϫ
40.4
45.6
24.8
Ϫ
Ϫ
Ϫ
128.5Ϫ138.6 m 12.1, 49.3, NEt2
127.2Ϫ140.6 m 105.1, 131.2, 139.7,
pyrazole-C
128.6Ϫ135.9 m 11.7, 13.4, 55.3,
57.9, NEt2
13[c] 60.8 d,
28.8 d, X ϭ PPh2,
Ϫ
Ϫ
53.4
53.7
44.5 br. s
50.2 br. s
28.1 br. s
28.3 d,
3JC,P ϭ 14.7 JC,P ϭ 4.5
175.8
3JC,P ϭ 10.7 JC,P ϭ 26.9
1
14[d] 67.2 br. s
32.8 d, X ϭ PPh2,
1JC,P ϭ 23.9
176.1 d,
129.2Ϫ134.0 m 7.4, 16.0, 52.4,
54.9, NEt2,
3
51.8 br. s,[e] 52.2 br. s,[e]
54.9 br. s,[f] 61.1 br. s,[f],
66.7 br. s,[g], 94.6 br. s,[f]
94.7 br. s,[f]
norbornadiene-C
[a]
All signals are singlets unless otherwise stated; d ϭ doublet, dd ϭ doublet of doublet, t ϭ triplet, m ϭ multiplet, br. s ϭ broad signal;
[b]
[c]
[d]
[e]
[f]
coupling constants in Hz. Solvent CHCl3. Solvent CH2Cl2. Measuring temperature Ϫ40 °C. Bridgehead CH group. Olefinic
CH group. CH2 group.
[g]
ether (4 ϫ 20-mL portions), the organic portion was separated,
and solvent was removed in vacuo. The resulting viscous oil was
purified by chromatography on silica gel with petroleum ether/di-
ethyl ether (6:1; Rf ϭ 0.43) as eluent to afford 3 (2.30 g, 6.6 mmol,
18 h. The reaction was quenched by the addition of brine (150 mL).
The aqueous phase was extracted with diethyl ether (4 ϫ 100-mL
portions). The combined organic phases were washed with brine,
dried with MgSO4, filtered, and concentrated by rotary evapor-
ation. The resulting viscous oil was purified by chromatography on
66%) as a colourless oil. 1H NMR (CDCl3): δ ϭ 2.59 ppm (d,
2
2JH,H ϭ 13.6 Hz, 1 H, CH2P), 2.96 (d, JH,H ϭ 13.6 Hz, 1 H, silica gel with petroleum ether/diethyl ether (1:1; Rf ϭ 0.39, strong
CH2P), 3.60Ϫ3.71 (m, 1 H, PhCH), 3.66 (s, 3 H, OCH3), 7.33Ϫ7.48 tailing) as eluent to afford 4a (3.60 g, 13.0 mmol, 65%) as a viscous
(m, 15 H, aromat. H). 13C NMR (CDCl3): δ ϭ 33.2 ppm (d, 1JC,P ϭ fluid. For analytical data see Tables 4, 6 and 7.
2
14.7 Hz, CH2P), 49.0 (d, JC,P ϭ 19.3 Hz, PhCH), 52.5 (s, OCH3),
Methyl 2-(Diethylaminomethyl)-3-hydroxy-2-methylpropanoate (4b):
3
127.9Ϫ139.8 (m, aromat. C), 174.3 (d, JC,P ϭ 4.6 Hz, CϭO). 31P
A solution of lithium diisopropylamide[27] (110 mmol) in THF (100
NMR (CDCl3): δ ϭ Ϫ20.9 (s). For further analytical data, see
Table 7.
mL) was added at Ϫ78 °C to a suspension of 2b (17.3 g, 100 mmol)
and paraformaldehyde (10.5 g, 350 mmol) in THF (200 mL). The
Methyl 3-Hydroxy-2-phenyl-2-[(1-piperidino)methyl]propanoate mixture was stirred for 1 h at Ϫ78 °C and then for 4 h at 25 °C,
(4a): Compound 2a (5.00 g, 20 mmol) and paraformaldehyde
quenched by the addition of water (50 mL) and partitioned be-
(2.70 g) were suspended in DMF (100 mL). Upon addition of NaH tween diethyl ether and water. The aqueous layer was extracted
(60% dispersion in mineral oil, 900 mg) to the cooled (0 °C) suspen-
sion, the reaction mixture became clear within minutes. The reac-
tion mixture was allowed to warm up to 25 °C and was stirred for
with diethyl ether (3 ϫ 50 mL), and the combined organic phases
were washed with brine, dried with MgSO4, and concentrated by
rotary evaporation. Distillation of the residue under reduced press-
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1689

R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
FULL PAPER
Table 7. Analytical data of 2؊14
No.
Formula
M [g/mol]
MS[a] m/z (%)
Ccalcd./Cfound
Hcalcd./Hfound
Clcalcd./Clfound
Ncalcd./Nfound
Pcalcd./Pfound
2a
2b
C15H21NO2
C9H19NO2
247.3
173.3
246 (10), 98 (100)
173 (19), 158 (22),
86 (100), 58 (61)
184 (28), 154 (13),
98 (100), 84 (46),
70 (86), 59 (62),
55 (92)
72.84/72.89
62.39/62.28
8.56/8.45
11.05/10.90
5.66/5.59
8.08/8.04
2c
C10H19NO2
185.3
64.83/64.54
10.34/10.34
7.56/7.55
2d
3
C8H12N2O2
168.2
348.4
168 (36), 137 (18),
109 (67), 81 (100),
69 (45)
348 (37), 333 (86),
262 (57), 201 (100),
183 (70)
57.13/57.14
75.85/75.73
7.19/7.25
6.08/6.08
16.66/n.d.
C22H21O2P
8.89/n.d.
4a
4b
4c
4d
C
C
C
C
16H23NO3
10H21NO3
11H21NO3
14H16N2O3
277.4
203.3
215.3
260.3
278 (1), 276 (1),
98 (100)
203 (1), 86 (100),
58 (16)
69.29/69.50
59.09/59.37
61.37/61.44
64.60/64.82
8.36/8.57
10.41/10.54
9.83/9.74
6.20/6.42
5.05/4.83
6.89/6.81
6.51/6.55
10.76/10.33
215 (2), 98 (100),
84 (10), 55 (14)
260 (38), 243 (13),
230 (70), 162 (100),
144 (74), 103 (65),
91 (28), 81 (66)
175 (2), 86 (100),
58 (15)
232 (3), 184 (75),
144 (100), 134 (37),
103 (55), 91 (51),
81 (80), 77 (52),
69 (38)
5a
5b
C9H21NO2
175.3
232.3
61.67/n.d.
12.08/n.d.
6.94/7.03
7.99/n.d.
C13H16N2O2
67.22/67.43
12.06/11.81
6a
6b
C
33H39NP2
37H34N2P2
511.6
568.6
511 (7), 434 (10),
183 (16), 86 (100)
568 (12), 491 (100),
383 (10), 301 (14),
262 (17), 183 (20)
221 (10), 86 (100),
58 (50)
278 (100), 243 (47),
211 (11)
371 (2), 183 (13),
86 (100)
251 (6), 220 (22),
215 (100), 185 (91),
152 (72), 115 (73),
103 (75), 91 (62),
81 (80), 77 (52)
418 (15), 383 (22),
315 (74), 301 (47),
262 (58), 183 (100)
653 (45), 533 (100)
604 (100), 569 (15),
511 (58), 434 (45)
696 (7), 661 (100),
626 (16), 491 (26),
411 (21)
77.47/77.47
78.15/77.54
7.68/7.84
6.03/6.03
2.74/2.77
4.93/4.94
12.11/n.d.
10.89/n.d.
C
7a
7b
8
C10H20ClNO2
C14H15ClN2O2
C22H30NO2P
C13H15ClN2O
221.7
278.7
371.5
250.7
54.17/53.79
60.33/60.30
71.14/70.89
62.28/62.41
9.09/9.13
5.42/5.45
8.14/8.30
6.03/6.31
15.99/n.d.
6.32/6.33
10.05/9.91
3.77/3.75
11.17/10.65
12.72/12.69
8.34/n.d.
7.39/7.67
9
14.14/n.d.
8.46/8.11
10
C
25H24ClN2P
418.9
71.68/72.20
5.77/5.89
6.69/6.57
11
12a
C
43H46N2P2
652.8
641.2
79.12/78.89
61.81/59.68
7.10/7.20
6.13/6.52
4.29/4.25
2.18/2.08
9.49/n.d.
9.66/n.d.
C33H39Cl2NNiP2
11.06/n.d.
10.16/9.58
12b
12c
C37H34Cl2N2NiP2
C43H46Cl2N2NiP2
C22H30Cl2NO2PPd
698.2
782.4
63.65/63.22
4.91/5.15
4.01/4.05
8.87/8.70
745 (43), 709 (15),
575 (11), 533 (62),
525 (10), 441 (100)
512 (100), 477 (59),
370 (71)
63.34[b]/63.14
5.74[b]/6.04
12.89[b]/n.d.
12.92/12.82
3.40[b]/3.36
7.51[b]/n.d.
13
548.8
711.5
48.15/48.18
48.96/48.69
5.51/5.51
5.38/5.39
2.55/2.61
1.97/2.02
5.64/5.78
8.71/8.76
14·PF6
C29H38F6NO2P2Rh
566 (100), 479 (13),
388 (30)
[a]
[b]
Compounds 2Ϫ11: EI-MS; compounds 12Ϫ14: FAB-MS. Calculated for 12c·0.5CH2Cl2.
1690
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693

C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
FULL PAPER
ure afforded 4b (8.8 g, 43 mmol, 43%) as a colourless liquid, b.p.
62 °C (0.2 mbar). For analytical data, see Tables 4, 6 and 7.
1-[2-(Chloromethyl)-3-(diphenylphosphanyl)-2-phenyl-
propyl]-1H-pyrazole (10): Starting material: 9. Yield: 2.32 g
(5.5 mmol, 55%) of a microcrystalline powder, Rf ϭ 0.43 (petro-
leum ether/diethyl ether, 3:1), m.p. 119 °C. 31P NMR (CDCl3): δ ϭ
Ϫ26.9 ppm (s). For further analytical data of 6a, 6b, and 10, see
Tables 5Ϫ7.
Methyl 3-Hydroxy-2-methyl-2-[(1-piperidino)methyl]propanoate
(4c): Starting material: 2c (18.5 g, 100 mmol). This compound was
prepared analogously to 4b. Yield: 11.1 g (51.6 mmol, 52%), b.p.
99 °C (0.2 mbar). For analytical data, see Tables 4, 6 and 7.
Methyl 3-Hydroxy-2-phenyl-2-[(1-pyrazolyl)methyl]propanoate (4d):
Pyrazole (5.10 g, 75 mmol) was deprotonated at 0 °C with sodium
hydride (1.00 g, 25 mmol, 60% dispersion in mineral oil) in DMF
(50 mL). This solution was slowly added at 0 °C to a mixture of
1a (8.14 g, 50 mmol) and paraformaldehyde (4.50 g, 150 mmol) in
DMF (50 mL). When a clear, colourless solution had formed, the
reaction mixture was stirred at 25 °C for 1 h. The reaction was
quenched by the addition of brine (150 mL), and the aqueous
phase was extracted with diethyl ether (4 ϫ 100-mL portions). The
combined organic phases were washed with brine, dried with
MgSO4, filtered, and concentrated by rotary evaporation. The re-
sulting viscous oil was purified by chromatography on silica gel
with petroleum ether/diethyl ether (1:3; Rf ϭ 0.42) as eluent to
afford 4d (8.10 g, 31.0 mmol, 62%) as a colourless oil. For analyt-
ical data, see Tables 4, 6 and 7.
General Procedure for the Synthesis of 7: A solution of anhydrous
PPh3 (15.7 g, 60 mmol) in CCl4 (80 mL) was heated under reflux
for 90 min, during which the colour of the solution changed from
colourless to light red. The substituted β-hydroxy ester
4
(30 mmol), dissolved in CCl4 (30 mL), was added rapidly to the
boiling reaction mixture from a dropping funnel. The solution dis-
coloured immediately and a brown precipitate of OϭPPh3 was
formed. The mixture was heated under reflux for another 12 h and
afterwards cooled to 25 °C. The precipitate was filtered off and
washed five times with diethyl ether. The combined organic solu-
tions were concentrated by rotary evaporation.
Methyl 2-(Chloromethyl)-3-(diethylamino)-2-methylpropanoate (7a):
Starting material: 4b. Kugelrohr distillation of the residue under
reduced pressure afforded 7a (7.3 g, 32.9 mmol, 55%) as a viscous
oil, b.p. 100 °C (0.2 mbar).
General Procedure for the Synthesis of 5 and 9: A solution of the
substituted ester (4 or 7b; 20 mmol) in THF (50 mL) was slowly
added at 25 °C to a stirred suspension of LiAlH4 (30 mmol per OH
group) in THF (200 mL). The mixture was stirred for 15 h and
hydrolysed by dropwise addition of water. The precipitate was fil-
tered off and washed five times with ethyl acetate. The combined
organic phases were dried with MgSO4 and the solvents were
evaporated to dryness to yield the corresponding alcohols.
Methyl 3-Chloro-2-phenyl-2-[(1-pyrazolyl)methyl]propanoate (7b):
Starting material: 4d. The remaining residue was purified by chro-
matography on silica gel with petroleum ether/diethyl ether (2:1;
Rf ϭ 0.53) as eluent to afford 7b (9.4 g, 33.7 mmol, 56%) as a
colourless powder, m.p. 100 °C. For analytical data of 7a and 7b,
see Tables 4, 6 and 7.
General Procedure for the Synthesis of 8 and 11: The substituted
alkyl chloride (7b or 10; 10 mmol, 1 equiv.) was dissolved in DMSO
(25 mL). In a separate vessel, diarylphosphane (1.2 equiv.) in
DMSO (40 mL) was deprotonated at 25 °C with KOtBu (1.2
equiv.). The resulting red potassium diarylphosphide solution was
stirred for 20 min and then added dropwise to the solution of the
alkyl chloride. The reaction mixture was stirred for 15 h and hydro-
lysed by dropwise addition of water (50 mL). The aqueous phase
was extracted with diethyl ether (4 ϫ 40-mL portions). The com-
bined organic phases were washed with brine and dried with
MgSO4, and the solvents were evaporated to dryness. The re-
maining residue was purified by chromatography on silica gel.
2-(Diethylaminomethyl)-2-methylpropane-1,3-diol (5a): Starting
material: 4b. Yield: 3.45 g (19.7 mmol, 99%) of a viscous oil.
2-Phenyl-2-[(1-pyrazolyl)methyl]propane-1,3-diol (5b): Starting ma-
terial: 4d. Yield: 4.52 g (19.5 mmol, 97%) of a microcrystalline pow-
der, m.p. 86 °C.
2-(Chloromethyl)-2-phenyl-3-(1-pyrazolyl)propan-1-ol (9): Starting
material: 7b. Yield: 4.81 g (19.2 mmol, 96%) of a microcrystalline
powder. For further analytical data of 5a, 5b, and 9, see
Tables 5Ϫ7.
General Procedure for the Synthesis of 6 and 10: The substituted
alcohol (5 or 9; 10.0 mmol, 1 equivalent) in THF (50 mL) was
deprotonated at Ϫ30 °C with nBuLi (1.2 equiv. per OH group).
The resulting solution was then allowed to warm to 25 °C, stirred
for 30 min and subsequently recooled to Ϫ30 °C. Methanesulfonyl
chloride (1.2 equiv. per OH group) was then added slowly, and the
reaction mixture was stirred at 0 °C for 2 h. In a separate vessel
diphenylphosphane (1.2 equiv. per OH group) in THF (50 mL) was
deprotonated with nBuLi (1.2 equiv. per OH group). The resulting
red lithium diphenylphosphide solution was added to the reaction
mixture at Ϫ30 °C. After the mixture had been stirred for 15 h at
25 °C, all volatiles were removed in vacuo. The remaining residue
was purified by chromatography on silica gel.
Methyl 3-(Diethylamino)-2-[(diphenylphosphanyl)methyl]-2-methyl-
propanoate (8): Starting material: 7b. Yield: 2.32 g (6.3 mmol, 63%)
of a viscous oil, Rf ϭ 0.43 (petroleum ether/diethyl ether, 3:1). FT-
IR (CH2Cl2): ν˜ ϭ 1726 cmϪ1 vs (CO), 1434 m (PPh). 31P NMR
(CDCl3): δ ϭ Ϫ24.3 ppm (s).
1-{2-[(Dimesitylphosphanyl)methyl]-3-(diphenylphospha-
nyl)-2-phenylpropyl}-1H-pyrazole (11): Starting material: 10. Yield:
2.32 g (6.3 mmol, 63%) of a microcrystalline powder, Rf ϭ 0.47
(petroleum ether/diethyl ether, 4:1), m.p. 120 °C. 31P NMR
4
(CDCl3): δ ϭ Ϫ34.1 ppm (d, JP,P ϭ 10 Hz, PMes2), Ϫ26.1 (d,
4JP,P ϭ 10 Hz, PPh2). For further analytical data of 8 and 11, see
Tables 5Ϫ7.
{2,2-Bis[(diphenylphosphanyl)methyl]propyl}diethylamine
(6a): Starting material: 5a. Yield: 3.34 g (6.5 mmol, 65%) of a vis-
cous oil, Rf ϭ 0.43 (petroleum ether/diethyl ether, 3:1). 31P NMR
(CDCl3): δ ϭ Ϫ27.1 ppm (s).
Coordination Chemistry Compounds
General Procedure for the Synthesis of 12: A solution of the respec-
tive tripod ligand (1.05 mmol) in ethanol (10 mL, with some THF
1-{2,2-Bis[(diphenylphosphanyl)methyl]-2-phenylethyl}- added to increase the solubility if necessary) was added rapidly to
1H-pyrazole (6b): Starting material: 5b. Yield: 3.91 g (6.9 mmol, a solution of NiCl2·6H2O (1.0 mmol, 240 mg) in ethanol (10 mL).
69%) of a microcrystalline powder, Rf ϭ 0.65 (petroleum ether/
diethyl ether/CH2Cl2, 2:1:1), m.p. 145 °C. 31P NMR (CDCl3): δ ϭ
Ϫ26.8 ppm (s).
The colour of the reaction mixture immediately changed to red and
within a few minutes the nickel complexes precipitated. After the
mixture had been stirred at 25 °C for 1 h, the precipitate was fil-
Eur. J. Inorg. Chem. 2003, 1681Ϫ1693
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1691

R. Faissner, G. Huttner, E. Kaifer, P. Rutsch
FULL PAPER
tered, washed with diethyl ether (3 ϫ 10-mL portions), and dried
in vacuo.
[1] [1a]
W. Hewertson, H. R. Watson, J. Chem. Soc. 1962, 84,
[1b]
1490Ϫ1494.
J. Am. Chem. Soc. 1971, 93, 1379Ϫ1389.
Feaster, R. L. Harlow, Tetrahedron: Asymmetry 1991, 2,
569Ϫ592.
G. M. Whitesides, C. P. Casey, J. K. Krieger,
[1c]
[(6a-κ2P)NiCl2] (12a): Starting material: 6a. Recrystallisation from
CH2Cl2/diethyl ether afforded 12a (525 mg, 0.82 mmol, 82%) in the
form of red crystals suitable for X-ray structure analysis, m.p.
212 °C (decomposition). 31P NMR (CD2Cl2, Ϫ40 °C): δ ϭ 10.7
ppm (s).
[(6b-κ2P)NiCl2] (12b): Starting material: 6b. Recrystallisation from
CH2Cl2/diethyl ether afforded 12b (650 mg, 0.93 mmol, 93%) in the
form of red crystals suitable for X-ray structure analysis, m.p.
248 °C (decomposition). 31P NMR (CD2Cl2, Ϫ40 °C): δ ϭ 15.6
ppm (s).
M. J. Burk, J. E.
[1d]
A. Muth, O. Walter, G. Huttner, A. Asam, L.
Zsolnai, C. Emmerich, J. Organomet. Chem. 1994, 468,
149Ϫ163.
[2]
[2a] S.-T. Liu, C.-L. Tsao, M. C. Cheng, S. M. Peng, Polyhedron
[2b]
1990, 21, 2579Ϫ2584.
39, 611Ϫ616.
1992, 46, 271Ϫ277.
S.-T. Liu, J. Chin. Chem. Soc. 1992,
[2c]
J. Dale, S. B. Fredriksen, Acta Chem. Scand.
[2d]
S.-T. Liu, C.-H. Yieh, H.-P. Dai, Proc.
Natl. Sci. Counc., Repub. China, Part A: Phys. Sci. Eng. 1995,
19, 1Ϫ4.
[3] [3a]
H. Heidel, G. Huttner, G. Helmchen, Z. Naturforsch., Teil
[(11-κ2P)NiCl2] (12c): Starting material: 11. Removal of the solvent
afforded 12c (585 mg, 0.75 mmol, 75%) in the form of an orange,
B 1993, 48, 1681Ϫ1692.
H. Heidel, G. Huttner, R. Vogel,
[3b]
[3c]
G. Helmchen, Chem. Ber. 1994, 127, 271Ϫ274.
T. Seitz, A.
[3d]
1
microcrystalline solid. H NMR and 13C NMR: no sharp signals
Muth, G. Huttner, Chem. Ber. 1994, 127, 1837Ϫ1842.
H.
Heidel, G. Huttner, L. Zsolnai, Z. Naturforsch., Teil B 1995,
could be detected, due to a dynamic process. 31P NMR (CD2Cl2,
50, 729Ϫ734. [3e] G. Reinhard, R. Soltek, G. Huttner, A. Barth,
2
2
Ϫ40 °C): δ ϭ Ϫ4.5 ppm (d, JP,P ϭ 95 Hz, PMes2), 4.0 (d, JP,P
ϭ
[3f]
O. Walter, L. Zsolnai, Chem. Ber. 1996, 129, 97Ϫ108.
Antelmann, U. Winterhalter, G. Huttner, B. C. Janssen, J. Vo-
gelgesang, J. Organomet. Chem. 1997, 545Ϫ546, 407Ϫ420.
A. Jacobi, G. Huttner, U. Winterhalter, Chem. Ber./Recueil
1997, 130, 1279Ϫ1294.
halter, S. Cunskis, Eur. J. Inorg. Chem. 1998, 675Ϫ692.
Soltek, G. Huttner, Eur. J. Inorg. Chem. 1998, 1417Ϫ1424.
B.
95 Hz, PPh2).
[3g]
For crystallographic data of 12a and 12b, see Table 3; for further
analytical data of 12aϪ12c, see Tables 5Ϫ7.
[3h]
A. Jacobi, G. Huttner, U. Winter-
[(8-κ2N,P)PdCl2] (13): A solution of ligand 8 (210 mg, 0.5 mmol)
in ethanol (15 mL) was added rapidly to a suspension of (η4-
cod)PdCl2 (145 mg, 0.5 mmol) in ethanol (10 mL). Within a few
minutes the yellow reaction mixture became clear. After the mix-
ture had been stirred at 25 °C for 12 h, all volatiles were removed
in vacuo. The residual yellow solid was washed with diethyl ether
(3 ϫ 10-mL portions) and dried in vacuo. Recrystallisation from
CH2Cl2/diethyl ether afforded 13 (180 mg, 0.33 mmol, 66%) in the
form of yellow crystals suitable for X-ray structure analysis. FT-IR
(CH2Cl2): ν˜ ϭ 1732 cmϪ1 vs (CO), 1438 m (PPh). 31P NMR
(CD2Cl2): δ ϭ 19.6 ppm (s). For crystallographic data, see Table 3;
for further analytical data, see Tables 4, 6 and 7.
[3i]
R.
[3j]
R. Soltek, G. Huttner, L. Zsolnai, A. Driess, Inorg. Chim. Acta
1998, 269, 143Ϫ156.
[3k]
J. Vogelgesang, G. Huttner, E. Kaifer,
P. Kircher, P. Rutsch, S. Cunskis, Eur. J. Inorg. Chem. 1999,
2187Ϫ2199.
[4] [4a]
S.-T. Liu, C.-Y. Liu, J. Org. Chem. 1992, 57, 6079Ϫ6080.
[4b] H.-E. Wang, C.-Y. Liu, M.-C. Cheng, S.-M. Peng, S.-T. Liu,
Phosphorus, Sulfur Silicon Relat Elem. 1992, 69, 201Ϫ211.
[5] [5a]
C. Sarafidis, U. S. Patent 3.445.540, 1969; Chem. Abstr.
[5b]
1969, 30038b.
M. J. Burk, R. L. Harlow, Angew. Chem.
1990, 102, 1511Ϫ1513; Angew. Chem. Int. Ed. Eng. 1990, 29,
1467Ϫ1469. [5c] B. C. Janssen, A. Asam, G. Huttner, V. Sernau,
L. Zsolnai, Chem. Ber. 1994, 127, 501Ϫ506.
[(8-κ2N,P)(η4-nbd)Rh]PF6 (14·PF6): [(η4-nbd)RhCl]2 (230 mg,
0.5 mmol) was dissolved in acetone (5 mL). In a second flask, po-
tassium hexafluorophosphate (195 mg, 1.05 mmol) was dissolved
in acetone (5 mL, 0.1 mL of water added). This solution was added
to the orange rhodium() solution. A colourless KCl precipitate
formed over 5 min, while the colour of the reaction mixture faded.
A solution of ligand 8 (370 mg, 1.0 mmol) in CH2Cl2 (5 mL) was
then added. After the mixture had been stirred at 25 °C for 1 h, all
volatiles were removed in vacuo. The residue was taken up in ace-
tone (20 mL) and dried with MgSO4. The insoluble KCl was re-
moved by filtering the solution through Kieselguhr. Removal of the
solvent in vacuo and recrystallisation from CH2Cl2/diethyl ether
afforded 14·PF6 (640 mg, 0.9 mmol, 90%) in the form of orange
crystals suitable for X-ray structure analysis, m.p. 203 °C (de-
composition). FT-IR (CH2Cl2): ν˜ ϭ 1725 cmϪ1 vs (CO), 1437 m
(PPh). 31P NMR (CD2Cl2): δ ϭ Ϫ144.2 ppm (sept, 1JP,F ϭ 711 Hz,
[6]
[6a] T. Seitz, A. Muth, G. Huttner, T. Klein, O. Walter, M. Fritz,
[6b]
L. Zsolnai, J. Organomet. Chem. 1994, 469, 155Ϫ162.
Seitz, A. Muth, G. Huttner, Z. Naturforsch., Teil B 1995, 50,
1045Ϫ1049.
Zsolnai, Z. Naturforsch., Teil B 1995, 50, 1287Ϫ1306.
Antelmann, G. Huttner, U. Winterhalter, J. Organomet. Chem.
T.
[6c]
T. Seitz, A. Asam, G. Huttner, O. Walter, L.
[6d]
B.
[6e]
1998, 553, 433Ϫ441.
P. Schober, R. Soltek, G. Huttner, L.
[6f]
Zsolnai, K. Heinze, Eur. J. Inorg. Chem. 1998, 1407Ϫ1415.
J. Vogelgesang, A. Frick, G. Huttner, P. Kircher, Eur. J. Inorg.
Chem. 2001, 949Ϫ971.
[7] [7a]
A. Muth, A. Asam, G. Huttner, A. Barth, L. Zsolnai,
[7b]
Chem. Ber. 1994, 127, 305Ϫ311.
G. Huttner, A. Asam, O. Walter, M. Büchner, L. Zsolnai,
Chem. Ber. 1995, 128, 63Ϫ70.
B. C. Janssen, V. Sernau,
[7c]
P. Schober, G. Huttner, L.
Zsolnai, A. Jacobi, J. Organomet. Chem. 1998, 571, 279Ϫ288.
E. Rouvier, J.-C. Giacomoni, A. Cambon, Bull. Soc. Chim. Fr.
1971, 5, 1717Ϫ1723.
[8]
[9]
1
PF6؊), 29.8 (d, JRh,P ϭ 174 Hz, PPh2). For crystallographic data,
D. A. Blinn, R. S. Button, V. Farazi, M. K. Neeb, C. L. Tapley,
T. E. Trehearne, S. D. West, T. L. Kruger, B. N. Storhoff, J.
Organomet. Chem. 1990, 393, 143Ϫ152.
see Table 3; for further analytical data, see Tables 4, 6 and 7.
[10] [10a]
[10b]
Acknowledgments
H. Wurziger, Kontakte (Darmstadt) 1988, 2, 36Ϫ41.
R. Noyori, M. Suzuki, Angew. Chem. 1984, 96, 854Ϫ882; An-
gew. Chem. Int. Ed. Engl. 1984, 23, 847Ϫ875.
We are indebted to the Deutsche Forschungsgemeinschaft and the
Fonds der Chemischen Industrie for financial support. One of us
(R. F.) is indebted to the local Graduiertenkolleg ‘‘Selektivität in
der organischen und metallorganischen Synthese und Katalyse’’ for
a scholarship. The technical support by T. Jannack (mass spectro-
metry) and the Microanalytical Laboratory of the Institute of Or-
ganic Chemistry is gratefully acknowledged. We are indebted to Dr.
J. Scherer and Dr. K. Heinze for their advice and help in solving the
crystal structure of 14·PF6.
[11] [11a]
S. Cacchi, P. G. Ciattini, E. Morera, G. Ortar, Tetrahedron
[11b]
Lett. 1988, 29, 3117Ϫ3120.
L. A. Paquette, G. D. May-
nard, J. Org. Chem. 1989, 54, 5054Ϫ5063.
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E. C. Taylor, J. L. La Mattina, J. Org. Chem. 1978, 43,
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1200Ϫ1204.
M. P. Moyer, P. L. Feldman, H. Rapoport, J.
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A. Stobie, Intern. Patent WO 9.204.346, 1992; Chem. Abstr.
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[13]
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2003, 1681Ϫ1693

C1-Symmetric Tripod Ligands Containing a P,P,N Donor Set
FULL PAPER
International Tables for X-ray Crystallo-
graphy, vol. 4, Kynoch Press, Birmingham, U.K., 1974.
L. Zsolnai, G. Huttner, XPMA, University of Heidelberg,
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[21c]
R. Appel, Angew. Chem. 1975, 87, 863Ϫ874; Angew. Chem. Int.
shelx/index. html
Ed. Engl. 1975, 14, 801Ϫ812.
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1998, 571, 231Ϫ241.
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