Synthesis of new phosphino amino alcohol ligands via ortho-alkyllithiation reactions. Versatile coordination behavior toward copper(I) and palladium(II)

Article abstract of DOI:10.1021/om970550e

2-[Methyl(2-methylphenyl)amino]ethanol undergoes an ortho-alkyllithiation reaction with n-butyllithium to lead to a new mixed benzyllithium - lithium alkoxide. This organolithium species reacts with PPh₂Cl, with selective P - C bond formation, to afford the ligand 2-[methyl-(2-((diphenylphosphino)methyl)phenyl)amino]ethanol L¹. The coordination of the ligand L¹ to copper(I) leads to the complex [Cu(L¹)₂](BF₄), whose structure has been determined by an X-ray diffraction study. In the solid state, one of the ligands acts as a monodentate phosphine while the other adopts a tridentate P,N,O coordination mode. A variabletemperature ³¹P NMR study demonstrated the existence of an equilibrium between the two modes in solution, with a coalescence temperature of ca. 0 °C, indicating a double-hemilabile behavior for the nitrogen and the oxygen functions. L¹ reacts with [Pd(Me)(Cl)(COD)] to give a dinuclear complex in which the ligand appears to behave as a bridging anionic P,O ligand. Such a complex could serve as a model for a key intermediate in the proposed mechanism for the homogeneous catalysis of the methoxycarbonylation of propyne by certain palladium(II) complexes containing P,N ligands. L¹ can undergo a second ortho-alkylmetalation reaction with n-butyllithium which, after addition of PPh₂Cl, provides the new ligand 2-{methyl[2-(bis(diphenylphosphino)methyl)phenyl]amino}ethanol (L²) in high yield.

Full text of DOI:10.1021/om970550e

Organometallics 1998, 17, 839-845
839
Syn th esis of New P h osp h in o Am in o Alcoh ol Liga n d s via
Or th o-Alk yllith ia tion Rea ction s. Ver sa tile Coor d in a tion
Beh a vior tow a r d Cop p er (I) a n d P a lla d iu m (II)
J acques Andrieu,† Barry R. Steele,† Constantinos G. Screttas,*,†
Christine J . Cardin,‡ and J orge Fornies‡
Institute of Organic and Pharmaceutical Chemistry, National Hellenic Research Foundation,
48 Vas. Constantinou Ave., 116 35 Athens, Greece, and Chemistry Department, University of
Reading, Whiteknights, Reading RG4 9BB, U.K.
Received J une 27, 1997
2-[Methyl(2-methylphenyl)amino]ethanol undergoes an ortho-alkyllithiation reaction with
n-butyllithium to lead to a new mixed benzyllithium-lithium alkoxide. This organolithium
species reacts with PPh2Cl, with selective P-C bond formation, to afford the ligand 2-[methyl-
(2-((diphenylphosphino)methyl)phenyl)amino]ethanol L1. The coordination of the ligand L1
to copper(I) leads to the complex [Cu(L1)2](BF4), whose structure has been determined by
an X-ray diffraction study. In the solid state, one of the ligands acts as a monodentate
phosphine while the other adopts a tridentate P,N,O coordination mode. A variable-
temperature 31P NMR study demonstrated the existence of an equilibrium between the two
modes in solution, with a coalescence temperature of ca. 0 °C, indicating a double-hemilabile
behavior for the nitrogen and the oxygen functions. L1 reacts with [Pd(Me)(Cl)(COD)] to
give a dinuclear complex in which the ligand appears to behave as a bridging anionic P,O
ligand. Such a complex could serve as a model for a key intermediate in the proposed
mechanism for the homogeneous catalysis of the methoxycarbonylation of propyne by certain
palladium(II) complexes containing P,N ligands. L1 can undergo a second ortho-alkylmeta-
lation reaction with n-butyllithium which, after addition of PPh2Cl, provides the new ligand
2-{methyl[2-(bis(diphenylphosphino)methyl)phenyl]amino}ethanol (L2) in high yield.
In tr od u ction
alcohol functions constitute only a very small fraction
of functional diphosphines due to the limited number
of synthetic procedures available. Generally, the re-
ported methods for the synthesis of functional diphos-
phine ligands involve either (i) the preparation of
diphosphines following the introduction of a nitrogen4
or oxygen function5 or (ii) the functionalization of
nitrogenated or oxygenated organic compounds by two
phosphorus-containing groups.6 To open up routes to
new phosphino amino alcohol ligands (P,N,O), we have
developed a synthetic strategy which involves the
preparation of a new mixed benzyllithium-lithium
alkoxide by an ortho-alkylmetalation reaction with
n-BuLi, followed by a P-C coupling of the organolithium
species with chlorodiphenylphosphine. In fact, as the
nucleophilic character of the benzyl anion should be
stronger than that of the alkoxide, we expected to
observe selective P-C bond formation in this second
reaction. Moreover, we also wished to explore the
coordination chemistry of these new functional phos-
phines and, in particular, the competition between the
coordination modes of the amino and alcohol functions.
In the last 10 years, there has been a considerable
increase in the interest shown toward mono- or diphos-
phine ligands containing nitrogen and/or oxygen func-
tions and toward their applications. Such chelating
ligands, which combine two or more donor atoms with
different “hard” or “soft” basic character, have been
shown to produce palladium complexes which are very
useful for homogeneous catalysis, e.g., for the copolym-
erization of olefins and CO to form polyketones1 or for
the methoxycarbonylation of propyne to produce methyl
methacrylate.2 A P,P,N,O ligand, i.e., a ligand possess-
ing two phosphorus, one nitrogen, and one oxygen atom
as potential donors, such as the chiral ferrocenyldiphos-
phinoethanolamine ligand has been used successfully
in the catalytic asymmetric allylation of â-diketones.
The higher selectivity observed for this functional ligand
has been ascribed to hydrogen bonding between the
hydroxyl group of the ligand and the attacking enolate
anion.3 Diphosphine ligands containing both amino and
† National Hellenic Research Foundation.
‡ University of Reading.
(1) Drent, E.; Budzelaar, P. H. M. Chem. Rev. 1996, 96, 663-681.
(2) Drent, E.; Arnoldy, P.; Budzelaar, P. H. M. J . Organomet. Chem.
1993, 455, 247-253.
(3) (a) Sawamura, M.; Nagata, H.; Sakamoto, H.; Ito, Y. J . Am.
Chem. Soc. 1992, 114, 2586-2592. (b) Consiglio, G.; Waymouth, R.
M. Chem. Rev. 1989, 89, 257-276.
(4) (a) Anderson, M. P.; Mattson, B. M. Inorg. Chem. 1983, 22, 2644-
2647. (b) Anderson, M. P.; Tso, C. C.; Mattson, B. M.; Pignolet, L. H.
Inorg. Chem. 1983, 22, 3267-3275.
(5) Al-J ibori, S.; Hall, M.; Hutton, A. T.; Shaw, B. L. J . Chem. Soc.,
Dalton Trans. 1984, 863-867.
(6) Luo, H.; Orvig, C. Can. J . Chem. 1996, 74, 722-729.
S0276-7333(97)00550-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 02/13/1998

840 Organometallics, Vol. 17, No. 5, 1998
Andrieu et al.
Resu lts a n d Discu ssion
with a much higher selectivity for P-C bond formation.
This chemoselectivity could be due to the stronger
nucleophilic character of benzylic compared to alkoxide
anionic fragments and clearly provides the basis for the
success of our method. Other reported synthetic pro-
cedures involve either multistep reactions which require
protection of the alcohol function or a coupling reaction
between ortho-metalated triarylphosphines with bis-
(trifluoromethyl) ketone. The yields of these prepara-
tions, however, were limited to between 45 and 50%.6,8
Coor d in a tion Mod es of th e P h osp h in o Am in o
Alcoh ol Liga n d L1. As the ligand L1 is formally a
potential six-electron donor with the three ligating
heteroatoms P, N, and O, several coordination modes
can be envisaged. To explore the selective coordination
properties of this ligand, we examined its behavior with
the two late transition metals copper(I) and palladium-
(II).
Or th o-Alk yllith ia tion Rea ction . Our starting ma-
terial, 2, was prepared from 2-methylaniline (1) by
following the synthetic method outlined in eq 1.
The ortho-metalated compound 3 was obtained from
2 under conditions similar to those described for the
ortho lithiation of N,N-dimethylbenzylamine (eq 2).7 In
Two equivalents of L1 in the presence of 1 equiv of a
cationic copper(I) complex led to complex 5 in good yield
(eq 4).
contrast to [2-((dimethylamino)methyl)phenyl]lithium,
the organodilithium salt 3 is somewhat soluble in Et2O
and cannot be isolated in the solid state by filtration.
The yield of 3 was determined by reaction with benzal-
dehyde (eq 2) to be at least 91%.
Syn t h esis of t h e Mon o(d ip h en ylp h osp h in o)
Am in o Alcoh ol Liga n d L1. As the ortho-metalated
compound 3 contains two nucleophilic centers, we have
explored its reactivity toward chlorodiphenylphosphine.
The reaction of 2 with 2.1 equiv of n-BuLi followed by
the addition of 1.1 equiv of PPh2Cl afforded the new
ligand L1 in high yield (see eq 3). The coupling is
The FAB mass spectrum of this complex did not
exhibit the molecular peak expected for 5 (without the
tetrafluoroborate anion) at m/z 762.4 but gave another
at m/z 411.9 corresponding to one ligand per metal.
However, the ratio of two ligands to one copper atom in
5 was confirmed by elemental analysis. In contrast to
the free ligand, we observed that the chemical shifts of
CH2N, CH3N, and OH in 5 were shifted from 3.25 to
2.77, from 2.75 to 2.40, and from 3.80 to 6.50 ppm,
1
respectively. Moreover, the H NMR spectrum of 5 at
room temperature shows only broad signals for the
CH3- and CH2- groups. These observations indicate
that those substituents are in the coordination sphere
of, or very close to, the copper metal center with the
formation of a P,N and/or P,O chelate. It is known that
cationic copper(I) complexes usually adopt a tetragonal
geometry with eight-electron-donor ligands. Of course,
in complex 5, each ligand is potentially a six-electron
donor, and thus the two nitrogen and two oxygen atoms
from the two ligands cannot all be coordinated to the
metal. This suggests then that a dynamic exchange is
taking place between the ligands around a tetracoordi-
nated metal center. In view of the molecular structure
of 5 (see Figure 2), it seems reasonable to propose an
equilibrium between the two isomeric structures 5a and
5b in CDCl3 solution (see eq 5).
To obtain more evidence for this proposal, we studied
the solution behavior of the complex by variable-
temperature 31P{1H} NMR in CDCl3. At 263 K (-10
°C), two different signals are observed at -3.0 and -17.6
ppm which correspond to the tridentate chelate P,N,O
bonding mode and P monodentate bonding mode of L1,
respectively. Coalescence was observed around 273 K
(0 °C) (see Figure 1).
predominantly with the carbanionic center, but a very
small amount (5-10%) of coupling to the alkoxide group
can also occur. The alcohol function can be restored by
subsequent addition of methanol.
The virtually quantitative P-C bond formation is
1
confirmed by H NMR spectroscopy. However, a P-O
coupling reaction between the dianionic species and
PPh2Cl can be observed under two other conditions,
namely (i) by addition of 1 equiv of n-BuLi to 2, followed
by the addition of 1 equiv of PPh2Cl (in this case, only
the alkoxide is formed and there is no ortho metalation;
see Experimental Section), and (ii) by addition of 2.1
equiv of n-BuLi, followed by the addition of more than
1 equiv of PPh2Cl. These observations show that a
mixed benzyllithium-lithium alkoxide species such as
3 reacts with the P-Cl bond in chlorodiphenylphosphine
(8) Boere´, R. T.; Montgomery, C. D.; Payne, N. C.; Willis, C. J . Inorg.
Chem. 1985, 24, 3680-3687.
(7) Manzer, L. E. J . Am. Chem. Soc. 1978, 100, 8068-8073.

Phosphino Amino Alcohol Ligands
Organometallics, Vol. 17, No. 5, 1998 841
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 5
empirical formula
fw
C88H96B2Cu2F8N4O4P4
1898.63
temp
293(2) K
wavelength
cryst syst, space group
unit cell dimens
0.710 69 Å
triclinic, P1h
a ) 15.573(6) Å
b ) 18.485(6) Å
c ) 19.085(7) Å
R ) 72.00(8)°
â ) 76.90(8)°
γ ) 74.91(8)°
4980.5 Å3
V
Z, calcd density
F(000)
2, 1.281 Mg/m3
2020
cryst size
θ range for data collection
index ranges
0.2 × 0.2 × 0.1 mm
2.68-20.81°
0 e h e 15, -16 e k e +18,
-18 e l e +19
no. of reflcns, collected/unique 9247/9238 (R(int) ) 0.0000)
refinement method
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
full-matrix-block least-squares on F2
9238/0/1096
1.091
R1 ) 0.0740, wR2 ) 0.1893
R1 ) 0.1305, wR2 ) 0.2200
0.0003(5)
F igu r e 1. Variable-temperature 31P{1H} NMR spectra of
5 in CDCl3.
extinction coeff
largest diff peak and hole
+0.441 and -0.363 e A-3
The equilibrium described in eq 5 gives the first
example of the opening and closing of a double chelate
P,N and P,O ligand.
X-r a y Str u ctu r e Deter m in a tion of 5. The crystal
data for 5 indicate a centrosymmetric structure due to
the presence of both enantiomeric forms (containing
respectively the Cu(1) and Cu(2) metal atoms) in the
unit cell; see Table 1). Views of one enantiomer are
given in Figures 2 and 3, in which the hydrogen atoms
and BF4- anion are omitted for clarification (see below).
Figure 2 shows that the copper metal center Cu(1) has
a pseudotetrahedral coordination geometry with angles
N(2)-Cu(1)-O(2) and P(2)-Cu(1)-P(1) of 80.3 and
131.3°, respectively. It is quite interesting to observe
that the two ligands adopt different coordination modes
in 5. One, labeled P(1)-N(1)-O(1), is only P-coordi-
nated, as is more clearly shown in the alternative
projection given in Figure 3. The second one, P(2)-
N(2)-O(2), adopts a tridentate η3(P,N,O) coordination
mode, forming the two nonplanar chelates P(2)Cu(1)N-
(2) (with a six-membered ring) and N(2)Cu(1)O(2) (with
a five-membered ring). The Cu(1)-N(2) and Cu(1)-O(2)
distances of 2.366(7) and 2.117(6) Å are consistent with
dative coordination bonds.9-11 The formation of the
P(2)-N(2) chelate leads to a shortening of the Cu-P
F igu r e 2. ORTEP plot of 5. H atoms are omitted for
clarity.
bond to 2.212(2) Å, as compared to 2.235(2) Å for the
P-coordination mode (see Table 2).
Thus, the observation of both the η1(P) and η3(P,N,O)
coordination modes of L1 in 6 in the solid state cor-
roborates the dynamic behavior of this complex in CDCl3
solution (see eq 5), in which the ligand L1 acts reversibly
as a mono- and tridentate ligand, exhibiting an unusual
double hemilabile character for both nitrogen and
oxygen functions.
Since functional phosphines such as P,N ligands are
of great interest in homogeneous catalysis, for example
in the catalytic copolymerization of olefins/CO and/or
for stabilization of the catalytic species,12 we have
(9) Dekker, G.; Buijs, A.; Elsevier, C. J .; Vrieze, K.; van Leeuwen,
P.; Smeets, W.; Spek, A.; Wang, Y.; Stam, C. Organometallics 1992,
11, 1937-1948.
(10) (a) Kapteijn, G. M.; Spee, M. P. R.; Grove, D. M.; Kooijman,
H.; Spek, A. L.; van Koten, G. Organometallics 1996, 15, 1405-1413.
(b) Driver, M. S.; Hartwig, J . F. J . Am. Chem. Soc. 1996, 118, 4206-
4207. (c) Grushin, V. V.; Alper, H. Organometallics 1993, 12, 1890-
1901.
(11) Andrieu, J .; Braunstein, P.; Tiripicchio, A.; Ugozzoli, F. Inorg.
Chem. 1996, 35, 5975-5985.
(12) Ladipo, F. T.; Anderson, G. K. Organometallics 1994, 13, 303-
306.

842 Organometallics, Vol. 17, No. 5, 1998
Andrieu et al.
reasonable.12,13 The ESI MS data, however, are not
easily accommodated by such a structure. In the case
of the Cu(I) complex above, the failure to observe the
expected molecular ion is quite readily explained by the
loss of a neutral ligand, whereas in the case of 6a a
major rearrangement process in the mass spectrometer
would have to be invoked to explain the loss of H + 2Cl.
The complex generated under mass spectroscopy condi-
tions could, however, be derived quite readily from a
dimer of structure 6b, which contains alkoxide bridges.
In contrast to the copper(I) complex 5, the 1H NMR
spectrum of 6 shows a significant shift for the protons
of the CH2O group from δ 3.77 for the free ligand to δ
4.25 in the complex, which is the consequence of the
covalent Pd-O bond. To confirm the presence of the
ammonium group, we compared the chemical shifts in
the 1H and 13C{1H} NMR spectra of the N-methyl group
of MeN (or MeNH+) in 6, L1, with those for N,N-
dimethylbenzylamine and its related ammonium chlo-
ride salt (see Table 3). These values indicate that the
chemical shifts observed at δ 3.11 and at δ 46.5 in the
1H and 13C{1H} NMR spectra are consistent with the
ammonium fragment in 6b and certainly make 6a a
much less likely structure.
F igu r e 3. ORTEP plot of 5 (alternative projection). H
atoms are omitted for clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5
Cu(1)-O(2)
Cu(1)-P(2)
Cu(1)-P(1)
Cu(1)-N(2)
2.117(6)
2.212(2)
2.235(2)
2.366(7)
Cu(2)-O(4)
Cu(2)-P(4)
Cu(2)-P(3)
Cu(2)-N(4)
2.124(5)
2.210(2)
2.231(2)
2.352(6)
O(2)-Cu(1)-P(2) 117.0(2)
O(4)-Cu(2)-P(4) 116.4(2)
O(4)-Cu(2)-P(3) 108.5(2)
131.30(10) P(4)-Cu(2)-P(3) 129.66(9)
O(2)-Cu(1)-P(1) 106.0(2)
P(2)-Cu(1)-P(1)
O(2)-Cu(1)-N(2)
P(2)-Cu(1)-N(2)
80.3(3)
94.7(2)
O(4)-Cu(2)-N(4)
P(4)-Cu(2)-N(4)
79.5(2)
94.6(2)
P(1)-Cu(1)-N(2) 114.8(2)
P(3)-Cu(2)-N(4) 115.4(2)
investigated the coordination properties of L1 with an
alkylpalladium(II) complex. The reaction of L1 with 1
equiv of [Pd(Me)(Cl)(COD)] (COD ) cycloocta-1,5-diene)
afforded a complex, 6, with an elemental analysis
compatible with [Pd(Cl)Me)(L1)]n. Crystals suitable for
It is surprising to note, however, that the NH+ proton
of the ammonium group in 6 was not observed in the
1H NMR spectrum. To understand this, we recorded
the 1H NMR spectrum of o-CH3C6H4NMe2H+Cl- at
different concentrations in CDCl3. We observed that,
as the concentration decreased, the signal for NH+ at δ
12.9 ppm became much broader and was eventually not
observable. As the dinuclear palladium complex 6 has
a low solubility in CDCl3, a similar phenomenon could
X-ray diffraction could not be obtained, and our conclu-
sions regarding the probable structure of this complex
are thus based on spectroscopic data. The ESI mass
spectrum of 6 exhibited a signal at m/z 941 (relative
intensity 100%), which is greater than that expected for
the monomer and is consistent with that expected for a
dimeric complex with the loss of two chlorides and one
proton. A dinuclear structure was also indicated by 1H
1
explain the absence of the proton NH+ in its H NMR
spectrum.
Such a binuclear complex could possibly arise via a
complex where L1 is initially coordinated to the pal-
ladium atom in a η2(P,N) mode with the chloride atom
in a trans position with respect to the phosphorus (see
Scheme 1). Similar coordination behavior has been
observed for other chloromethylpalladium complexes
containing P,N ligands, e.g. P,N ) 1-(dimethylamino)-
8-(diphenylphosphino)naphthalene (PAN) and 1-(dimeth-
ylamino)-3-(diphenylphosphino)propane (PC3N).9 The
close proximity of the alcohol function to the metal
would then permit the possibility of amine-assisted
NMR spectroscopy with two doublets at δ 3.75 (2J P,H
)
12 Hz) and 0.69 (3J P,H ) 1.7 Hz) for the PCH2 and
PdCH3 protons, respectively. A likely structure for the
dimer would be 6a and, while the presence of the singlet
which is observed at δ 45.6 in the 31P{1H} NMR
spectrum would be consistent with either a cis or trans
arrangement of the phosphorus nuclei, literature pre-
cedents indicate the trans configuration to be more
(13) Andrieu, J .; Braunstein, P.; Naud, F. J . Chem. Soc., Dalton
Trans. 1996, 2903-2909.

Phosphino Amino Alcohol Ligands
Organometallics, Vol. 17, No. 5, 1998 843
Ta ble 3. Ch em ica l Sh ifts (p p m ) of th e N-Meth yl
Gr ou p
1H NMR
(in CDCl3)
13C{1H} NMR
(in CDCl3)
compd
N-alkyl group
L1
2.70
2.83
3.18
3.11
44.2
44.1
46.3
46.5
CH3N
o-CH3C6H4NMe2
CH3N
o-CH3C6H4NMe2H+Cl-
CH3NH+
CH3NH+
6
Sch em e 1
The ligand L2 reacts with palladium(II) and platinum-
(II) dihalides to give complexes 8 and 9, respectively (eq
8).
deprotonation and formation of a palladium-alkoxide
species, leading subsequently to the dinuclear structure
6b stabilized by the formation of an alkoxide bridge. A
structure such as 6b is quite attractive and interesting
because similar species have been proposed as catalytic
intermediates in the preparation of methyl methacry-
late. For example, Drent has suggested that methanol
solvent could be deprotonated by the strongly basic
nitrogen function of a P,N ligand mediated by a palla-
dium(II) complex.2 We note also that a few examples
of mixed methylpalladium alkoxide or arylpalladium
complexes containing alkoxide bridges have been re-
cently characterized by X-ray structure determination.10
With the objective of preparing a related neutral
complex from 6, we investigated the reaction with 6 in
the presence of a base such as MeONa in toluene.13 The
occurrence of a deprotonation reaction was indicated by
the formation of a new peak at δ 41.2 in the 31P{1H}
NMR spectrum in CDCl3, but unfortunately, the com-
plex could not be fully characterized due to its instability
in solution and rapid decomposition with the formation
of palladium metal.
Syn th esis of th e Bis(d ip h en ylp h osp h in o) Am in o
Alcoh ol Liga n d L2. As diphosphine ligands containing
amino and alcohol functions are poorly represented in
the literature, we wished to extend the preparation of
L1 to the bis(diphenylphosphino) amino alcohol ligand
L2 via a second ortho-alkylmetalation reaction. By a
procedure similar to that for L1, the functional diphos-
phine ligand L2 was obtained in high yield (eq 7).
The 13C{1H} NMR spectrum showed a triplet at δ 36.6
(2J P,H ) 24 Hz), which confirms the presence of the
second phosphorus atom in the PCHP fragment. It is
interesting to note the marked chemical shift of the
proton PCHP from δ 3.60 in the ligand L1 to the region
for aromatic protons in L2. This has been substantiated
by a proton-carbon correlation NMR experiment. As
for L1, the reaction (see above) between the mixed
organodilithium species 7, derived from the metalation
of L1, and chlorodiphenylphosphine occurred with a high
selectivity for P-C bond formation.
The 31P{1H} NMR spectra exhibit a singlet at δ -25.6
for 8 and at δ -40.8 (1J Pt,P ) 2906 Hz) for 9. Such
negative values are typical of a P,P coordination mode.11
Con clu d in g Rem a r k s
We have developed a generally applicable synthetic
methodology for the preparation of new mixed benzyl-
lithium-lithium alkoxides such as 3 by an ortho-
alkylmetalation reaction with n-butyllithium. The re-
activity of 3 toward the P-Cl bond of diphenylchloro-
phosphine showed a remarkable selectivity for P-C
bond formation and led to the new phosphino amino
alcohol ligand L1. The coordination chemistry of L1 has
been explored with two late-transition-metal complexes,
and the results obtained indicate that it behaves as a
rather versatile ligand. Its coordination properties are
summarized in Table 4. We have demonstrated that
the association of two different functions (amine and
alcohol) in the same phosphorus ligand does not merely
constitute a sum of the coordination properties of each
function but generates new properties such as the
double hemilabile character of the different functions
and intramolecular proton transfer.
An unusual proton transfer from the alcohol to the
amino group of L1 appears to take place to give a
dinuclear palladium complex (6b). Such a transfer
would represent a catalytic model for OH activation by
palladium dihalides in the presence of nitrogen base.
Such a process has been proposed as a key step in, for
example, the homogeneous catalysis of the methoxycar-
bonylation of propyne by palladium complexes containg
bifunctional phosphino amine ligands.2
The mono(diphenylphosphino)amino alcohol ligand L1
underwent a second ortho-alkylmetalation reaction, and
again a selective P-C coupling reaction with chlo-
rodiphenylphosphine allowed access to the new func-
tional diphosphine ligand L2. We have just started to
explore the coordination properties of L2, and its be-
havior seems to be similar to that of the dppm ligand
(dppm ) bis(diphenylphosphino)methane). Further

844 Organometallics, Vol. 17, No. 5, 1998
Andrieu et al.
Ta ble 4. Coor d in a tion P r op er ties of th e P ,N,O Liga n d L1
vacuum (1 mmHg) at 93-95 °C: yield 36.9 g (48% based on
o-toluidine). The product was identical with that produced by
a previously reported procedure.16 1H NMR (CDCl3): δ 7.25-
investigations are currently in progress in order to
evaluate the effect of the 2-amino alcohol function of
L1 and L2, whether free or coordinated (and the related
ammonium salts), on the solubility properties of the
complexes in biphasic solutions.
2
7.02 (m, 4H, aromatic), 3.68 (t, 2H, J H,H ) 5.4 Hz, CH2O),
3.10 (t, 2H, 2J H,H ) 5.4 Hz, CH2N), 2.66 (s, 3H, CH3N), 2.45 (s,
br, 1H, OH, exchange with D2O), 2.34 (s, 3H, CH3-CAr). 13C-
{1H} NMR (CDCl3): δ 151.5, 133.2, 131.0, 126.5, 123.7, 120.5
(s, 6C, aromatic), 58.9 (s, 1C, CH2OH), 57.5 (s, 1C, CH2N), 41.9
(s, 1C, CH3N), 17.9 (s, 1C, CH3-CAr). C10H15NO (Mr ) 165.11).
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were performed in
Schlenk-type flasks under argon. Solvents were purified and
dried under argon by conventional methods. The 1H, 13C{1H},
and 31P{1H} NMR spectra were recorded at 300.13, 75.04, and
121.47 MHz, respectively, on a Bruker AC 300 instrument.
Assignments of 1H and/or 13C{1H} NMR spectra were con-
firmed by DEPT experiments and/or proton-carbon correla-
tions. FAB (glycerol matrix) and ESI mass spectra and
elemental analyses were performed at the National Hellenic
Research Foundation in Athens. The complexes [Pd(Me)(Cl)-
(COD)] (COD ) cycloocta-1,5-diene), [Cu(NCMe)4](BF4), [PdCl2-
(NCPh)2], and [PtCl2(NCPh)2] were prepared according to
literature procedures.12,14,15 The solution of n-butyllithium in
methylcyclohexane (1.87 M) was prepared by following the
conventional procedure. The organic compounds o-toluidine
(2-methylaniline) (1), ethylene chlorohydrin (2-chloroethanol),
and chlorodiphenylphosphine were commercial products (Al-
drich).
Syn th esis of 2-[Meth yl(2-m eth ylp h en yl)a m in o]eth a n ol
(2).16 A mixture of o-toluidine (1; 50.0 g, 0.467 mol) and
2-chloroethanol (37.6 g, 0.467 mol) was heated at 160 °C for
15 min. After cooling to room temperature, a solution of NaOH
(0.47 mol in 300 mL of water) and CH2Cl2 (50 mL) were added.
The organic phase was separated. All solvents were removed
in vacuo, and a yellow viscous oil was obtained. Distillation
under high vacuum (0.8 mmHg) at 115 °C afforded the
functionalized o-toluidine as a colorless oil. The oil obtained
(47.6 g, 0.315 mol) and NaHCO3 (45.0 g, 0.630 mol) were
dissolved in methanol (200 mL). Dimethyl sulfate (30 mL,
0.315 mol) was added dropwise at room temperature. The
reaction started after a few minutes with the formation of
carbon dioxide. After the mixture was stirred for 3 days, the
methanol was removed in vacuo. The yellow residue obtained
was dissolved in a mixture of water (200 mL) and CH2Cl2 (200
mL). The organic phase was separated and concentrated in
vacuo. Compound 2 was purified by distillation under high
Syn th esis of 4. A solution of 2 (1.65 g, 10.0 mmol) in Et2O
(10 mL) was cooled to 0 °C. After the mixture was stirred for
10 min, n-butyllithium (14 mL, 25.0 mmol) was added drop-
wise. The mixture was stirred and warmed slowly from 0 °C
to room temperature. After 1 h, the pale yellow solution was
heated under reflux for 3 h. The formation of the ortho-
metalated compound 3 was then complete and took the form
of a mustard yellow suspension. After cooling to 0 °C,
benzaldehyde (1.1 mL, 11.0 mmol) was added and the mixture
stirred for 20 min. Water (5 mL) and CH2Cl2 (20 mL) were
then introduced. The organic phase was separated and
afforded a pale yellow oil after evaporation of solvents in vacuo.
The oil was analyzed by 1H NMR and, by integration of the
peaks at δ 4.89 corresponding to the proton CH(Ph)(OH) of 4
and at δ 2.34 for the protons CH3-CPh of 2, the yield of product,
and thus also that of the intermediate metalated species, was
estimated to be greater than 91%. White crystals of 4 were
obtained from the oil by crystallization in cold methanol: yield
1.41 g (52%). 1H NMR (CDCl3): δ 7.38-7.08 (m, 4H, aro-
matic), 5.60 (s, br, 2H, OH, exchange with D2O), 4.89 (dd, 1H,
2
2J H X ) 9.0 Hz, J H
,
X ) 2.8 Hz, CHX(Ph)(OH)), 3.68 (t, 2H,
,H
A
H
B
2J H,H ) 5.1 Hz, CH2O), 3.34 (dd, 1H, 1J H
, ,
B ) 14.1 Hz, 2J H
H H
A X
A
) 9.0 Hz, part A from ABX spin system of CHAHB-CHX(Ph)-
(OH)), 3.05 (t, 2H, 2J H,H ) 5.1 Hz, CH2N), 2.96 (dd, 1H, 1J H
,
H
B
A
2
) 14.1 Hz, J H
,
) 2.8 Hz, part B from ABX spin system of
H
B
X
CHAHB-CHX(Ph)(OH)), 2.68 (s, 3H, CH3N). 13C{1H} NMR
(CDCl3): δ 151.5-121.2 (m, 12C, aromatic), 75.6 (s, 1C, CH-
(Ph)(OH)), 59.0 (s, 2 C, CH2OH + CH2N), 42.8 (s, 1C, CH3N),
42.2 (s, 1C, CH2-CH(Ph)(OH)), 17.9 (s, 1C, CH3-C(Ph)). Anal.
Calcd for C17H21NO2 (Mr ) 271.16): C, 75.25; H, 7.79; N, 5.16.
Found: C, 75.11; H, 7.72; N, 5.22.
Syn th esis of 2-[Meth yl(2-((d ip h en ylp h osp h in o)m eth -
yl)p h en yl)a m in o]eth a n ol (L1). To a solution of 2 (4.96 g,
30 mmol) in Et2O (30 mL) was added dropwise n-butyllithium
(35 mL, 63 mmol). After it was stirred at room temperature
overnight, this mixture was heated under reflux for 3 h and
then cooled to 0 °C. Chlorodiphenylphosphine (5.9 mL, 33
mmol) was added dropwise and the mixture stirred overnight.
(14) Kubas, G. J . Inorg. Synth. 1979, 19, 90-91.
(15) Anderson, G. K.; Lin, M. Inorg. Synth. 1990, 28, 60-63.
(16) Lattes, A.; Verdier, A. Bull. Soc. Chim. Fr. 1965, 2037-2043.

Phosphino Amino Alcohol Ligands
Organometallics, Vol. 17, No. 5, 1998 845
1H, OH, exchange with D2O). 13C{1H} NMR (CDCl3):
Methanol (50 mL) was introduced. After this mixture was
stirred for 3 h, all organic solvents were removed in vacuo.
The viscous oil obtained was dissolved in toluene (100 mL),
and the solution was filtered through Celite. Evaporation of
toluene in vacuo afforded the functional phosphine ligand L1
as a pale yellow oil, which was dried at 80 °C under high
vacuum for 2 h. Satisfactory elemental analyses could not be
obtained, apparently due to tenacious retention of solvent. The
oil was used for further reactions without other purification:
yield 9.20 g (88%). 1H NMR (CDCl3): δ 7.55-7.17 (m, 14H,
aromatic), 3.80 (s, br, 1H, OH, exchange with D2O), 3.73 (t,
2H, 2J H,H ) 5.1 Hz, CH2O), 3.52 (d, 2H, 2J P,H ) 2.4 Hz, CH2P),
δ
152.4-122.0 (m, 26C, aromatic), 59.4 (s, 1C, CH2OH), 58.6 (s,
1
1C, CH2N), 41.2 (s, 1C, CH3N), 36.6 (t, 1C, J P,C ) 24 Hz,
PCHP). 31P{1H} NMR (CDCl3): δ 0.6 (s). C34H33NOP2 (Mr )
533.20).
Syn th esis of 8. To a solution of L2 (0.152 g, 0.28 mmol) in
CH2Cl2 (10 mL) was added [PdCl2(NCPh)2] (0.104 g, 0.28
mmol). After it was stirred for 1 h, the solution was concen-
trated in vacuo. Addition of hexane afforded an orange
powder, which was filtered off and dried in vacuo: yield 0.152
g (75%). 1H NMR (CDCl3): δ 8.06-5.48 (m, 24H, aromatic
with 1H from PCHP group), 3.67 (t, 2H, 2J H,H ) 5.4 Hz, CH2O),
2.86 (t, 2H, 2J H,H ) 5.4 Hz, CH2N), 2.43 (s, 3H, CH3N), 2.13 (s,
br, 1H, OH). 13C{1H} NMR (CDCl3): δ 150.7-121.5 (m, 30C,
aromatic), 59.2 (s, 1C, CH2N), 58.8 (s, 1C, CH2OH), 50.0 (s,
br, 1C, PCHP), 42.3 (s, 1C, CH3N). 31P{1H} NMR (CDCl3): δ
-25.6 (s). Anal. Calcd for C34H33Cl2NOP2Pd‚1/2CH2Cl2 (Mr )
751.02): C, 55.02; H, 4.56; N, 1.87. Found: C, 54.73; H, 4.88;
N, 1.86.
2
3.20 (t, 2H, J H,H ) 5.1 Hz, CH2N), 2.70 (s, 3H, CH3N). 13C-
{1H} NMR (CDCl3): δ 151.3-121.5 (m, 18C, aromatic), 59.4
(s, 1C, CH2OH), 58.1 (s, 1C, CH2N), 44.2 (s, 1C, CH3N), 32.3
(d, 1C, 1J P,C ) 12.8 Hz, CH2P). 31P{1H} NMR (CDCl3): δ -14.8
(s). C22H24NOP (Mr ) 349.16).
Syn th esis of N-(2-Dip h en ylp h osp h in yl)eth yl)-N,2-d i-
m eth ylben zen a m in e. By a procedure similar to that for
ligand L1, the isomer was obtained from 3 (0.66 g, 4.0 mmol),
n-butyllithium (2.3 mL, 4.2 mmol), chlorodiphenylphosphine
(0.75 mL, 4.2 mmol), after addition of only few milliliters of
methanol, as a viscous white oil: yield of crude product 1.05
Syn th esis of 9. To a solution of L2 (0.240 g, 0.45 mmol) in
CH2Cl2 (10 mL) was added [PtCl2(NCPh)2] (0.213 g, 0.45
mmol). After it was stirred for 1 h, the solution was concen-
trated in vacuo. Addition of hexane afforded a white powder,
which was filtered off and dried in vacuo: yield 0.295 g (82%).
1H NMR (CDCl3): δ 8.01-5.56 (m, 24H, aromatic with 1H from
g (75%). Further purification proved unsuccessful. 1H NMR
3
(C6D6): δ 7.84-6.88 (m, 14H, aromatic), 3.86 (dt, 2H, J P,H
)
2
2
2
PCHP group), 3.66 (t, 2H, J H,H ) 5.7 Hz, CH2O), 2.88 (t, 2H,
12.0 Hz, J H,H ) 6.0 Hz, CH2OP), 3.04 (t, 2H, J H,H ) 6.0 Hz,
CH2N), 2.42 (s, 3H, CH3N), 2.24 (s, 3H, CH3-CPh). 13C{1H}
NMR (C6D6): δ 152.3-120.5 (m, 18C, aromatic), 68.0 (d, 1C,
2J P,C ) 18.7 Hz, CH2OP), 57.0 (s, 1C, CH2N), 42.4 (s, 1C,
CH3N), 18.5 (s, 1C, CH3-CPh). 31P{1H} NMR (C6D6): δ 112.0
(s). C22H24NOP (Mr ) 349.16).
2J H,H ) 5.7 Hz, CH2N), 2.43 (s, 3H, CH3N), 2.20 (s, br, 1H, OH
exchange with D2O). 13C{1H} NMR (CDCl3): δ 151.5-112.2
(m, 30C, aromatic), 59.9 (s, 1C, CH2N), 59.5 (s, 1C, CH2OH),
55.2 (t, 1C, 1J P,C ) 33 Hz, PCHP), 43.5 (s, 1C, CH3N). 31P{1H}
1
NMR (CDCl3): δ -40.8 (s, with 195Pt satellites, J Pt,P ) 2906
Syn th esis of 5. To a solution of L1 (0.900 g, 2.57 mmol) in
CH2Cl2 (15 mL) was added the complex [Cu(NCMe)4](BF4)
(0.400 g, 0.127 mmol). The colorless solution was stirred for
2 days. Slow addition of diethyl ether afforded white crystals
of 5, which were filtered, washed with ether, and dried in
vacuo: yield 0.982 g (91%). 1H NMR (CDCl3): δ 7.38-6.30
(m, 28H, aromatic), 6.50 (s, br, 2H, OH, exchange with D2O),
3.90 (s, br, 4H, CH2P), 3.74 (s, br, 4H, CH2O), 2.77 (s, br, 4H,
Hz). Anal. Calcd for C34H33Cl2NOP2Pt (Mr ) 798.10): C,
51.12; H, 4.17; N, 1.75. Found: C, 51.32; H, 4.29; N, 1.51.
X-r a y Str u ctu r e Deter m in a tion of 5. The crystal of 5
used for data collection was mounted in a capillary at room
temperature, and data were collected using a small (180 mm
diameter) Mar (X-ray Research) scanner mounted on a 3 kW
molybdenum sealed-tube source. A total of 95 frames of data
were collected using a 2° rotation angle and a crystal-to-plate
distance of 75 mm, giving an overall completeness of 88.54%,
a multiplicity of 1.88, and a merging R of 4.99% on intensities.
The structure was solved using the direct-methods routine
within the program Shelxs (courtesy of George Sheldrick,
University of Go¨ttingen) and refined using full-matrix least-
squares methods to a final conventional R factor of 7.51%.
Hydrogen atoms were included in calculated positions. The
asymmetric unit of the crystal contains two distinct molecules,
each of which shows one ligand to be tridentate and the other
to be monodentate, giving an overall distorted-tetrahedral
geometry at each copper center. Disordered solvent, equiva-
lent to three molecules of ether, can be seen in the final
difference electron density map, and although an attempt to
model this was made, no satisfactory model could be found,
giving a relatively high observed R factor. Hydrogen atoms
were inserted in calculated positions. Crystal data are given
in Table 1, selected bond lengths and angles are shown in
Table 2, and a single molecule of the complex with a partial
numbering scheme is displayed in Figures 2 and 3. The full
data have been deposited with the Cambridge Crystallographic
Data Centre.
CH2N), 2.40 (s, br, 6H, CH3N). 13C{1H} NMR (CDCl3):
δ
132.9-120.0 (m, 36C, aromatic), 65.7 (s, 2C, CH2OH), 58.6 (s,
2C, CH2N), 43.9 (s, 2C, CH3N), 31.4 (s, br, 2C, CH2P). 31P{1H}
NMR (CDCl3): δ -10.2 (s, br). IR (KBr): 1080 cm-1 (vs, νBF ).
-
4
Mass spectrum (FAB; glycerol matrix): m/z (relative intensity)
411.9 (100%, M+ - L1 - BF4). Anal. Calcd for C44H48
-
BF4N2O2P2Cu (Mr ) 849.18): C, 62.23; H, 5.70; N, 3.30.
Found: C, 61.84; H, 5.74; N, 3.14.
Syn th esis of 6. By a procedure similar to that for complex
5, but with L1 (0.262 g, 0.75 mmol) and [Pd(Me)(Cl)(COD)]
(0.200 g, 0.75 mmol), as starting materials, 6 was obtained as
a pale yellow powder: yield 0.450 g (59%). 1H NMR (CDCl3):
δ 7.65-6.94 (m, 28H, aromatic), 4.25 (s, br, 4H, CH2O), 3.75
2
(d, 4H, J P,H ) 12 Hz, CH2P), 3.36 (s, br, 4H, CH2N), 3.11 (s,
6H, CH3N), 0.69 (d, 6H, 3J P,H ) 1.7 Hz, CH3Pd). 13C{1H} NMR
(CDCl3): δ 133.2-119.5 (m, 36C, aromatic), 62.2 (s, 2C, CH2O),
1
60.8 (s, 2C, CH2N), 46.5 (s, 2C, CH3N), 34.3 (d, 2C, J P,C ) 25
Hz, CH2P), 0.9 (s, br, 2C, CH3Pd). 31P{1H} NMR (CDCl3): δ
45.6 (s). Mass spectrum (electrospray ionization): m/z (relative
intensity) 941.1 (100%, M+ - 2 Cl - 1 H). Anal. Calcd for
C
46H54Cl2N2O2P2Pd2 (Mr ) 1010.11): C, 54.65; H, 5.39; N, 2.77.
Found: C, 54.44; H, 5.24; N, 2.74.
Ack n ow led gm en t. This work was supported by the
European Union Human Capital and Mobility Network
Contract No. ERBCHRXCT 930281.
Syn th esis of L2. By a procedure similar to that for the
ligand L1, the functional diphosphine ligand L2 was obtained
by reaction between the mixed organolithium species 7 (pre-
pared from L1 (3.38 g, 9.7 mmol) and n-butyllithium (11.3 mL,
21 mmol)) and chlorodiphenylphosphine (1.8 mL, 10.8 mmol),
as a waxy solid: yield 4.0 g (77%). Retention of small amounts
of solvent precluded the acquisition of satisfactory elementary
analyses. 1H NMR (CDCl3): δ 7.65-5.45 (m, 24H, aromatic
with 1H from PCHP group), 3.55 (t, 2H, 2J H,H ) 5.4 Hz, CH2O),
2.30 (t, 2H, 2J H,H ) 5.4 Hz, CH2N), 2.23 (s, 3H, CH3N), 2.00 (s,
Su p p or tin g In for m a tion Ava ila ble: Further details of
the structure determination, including a fully numbered
ORTEP drawing and tables of atomic coordinates, bond lengths
and angles, and thermal parameters for 5 (16 pages). Ordering
information is given on any current masthead page.
OM970550E