A modular approach to achiral and chiral nickel(II), palladium(II), and platinum(II) PCP pincer complexes based on diaminobenzenes

Article abstract of DOI:10.1021/om060289e

The synthesis and characterization of a series of nickel, palladium, and platinum complexes containing new achiral and chiral PCP pincer ligands based on 1,3-diaminobenzene, 5-trifluoromethyl-1,3-diaminobenzene, and 3,5-diamino-4-chloroisobutylbenzoate are reported. The new PCP ligands are prepared conveniently in high yield by treatment of the respective diaminobenzene with 2 equiv of a variety of achiral and chiral R₂PCl compounds in the presence of base. PCP complexes of Ni(II), Ni(PCP)Cl, were synthesized by the reaction of NiCl₂·6H₂O with 1 equiv of a PCP ligand. In similar fashion, treatment of M(COD)X₂ (M = Pd, Pt; X = Cl, Br) with 1 equiv of a PCP ligand yields the square-planar complexes M(PCP)X. Palladium PCP complexes featuring a coordinated TFA ligand (TFA = CF₃COO^-) are obtained by the reaction of Pd(TFA)₂ with 1 equiv of a PCP ligand. Alternatively, palladium PCP complexes can also be generated via an oxidative addition route. Addition of 2 equiv of PCP ligands based on 3,5-diamino-4-chloroisobutylbenzoate to Pd ₂(dba)₃ affords the respective Pd(PCP)Cl pincer complexes in high yields. X-ray structures of representative Ni, Pd, and Pt PCP complexes have been determined. Finally, the use of the palladium complexes as catalysts for the Suzuki-Miyaura coupling of some aryl bromides and phenyl boronic acid has been examined.

Full text of DOI:10.1021/om060289e

Organometallics 2006, 25, 3817-3823
3817
A Modular Approach to Achiral and Chiral Nickel(II),
Palladium(II), and Platinum(II) PCP Pincer Complexes Based on
Diaminobenzenes
David Benito-Garagorri, Vladica Bocokic´, Kurt Mereiter, and Karl Kirchner*
Institute of Applied Synthetic Chemistry and Institute of Chemical Technologies and Analytics,
Vienna UniVersity of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
ReceiVed April 3, 2006
The synthesis and characterization of a series of nickel, palladium, and platinum complexes containing
new achiral and chiral PCP pincer ligands based on 1,3-diaminobenzene, 5-trifluoromethyl-1,3-
diaminobenzene, and 3,5-diamino-4-chloroisobutylbenzoate are reported. The new PCP ligands are prepared
conveniently in high yield by treatment of the respective diaminobenzene with 2 equiv of a variety of
achiral and chiral R2PCl compounds in the presence of base. PCP complexes of Ni(II), Ni(PCP)Cl, were
synthesized by the reaction of NiCl2‚6H2O with 1 equiv of a PCP ligand. In similar fashion, treatment
of M(COD)X2 (M ) Pd, Pt; X ) Cl, Br) with 1 equiv of a PCP ligand yields the square-planar complexes
M(PCP)X. Palladium PCP complexes featuring a coordinated TFA ligand (TFA ) CF3COO-) are obtained
by the reaction of Pd(TFA)2 with 1 equiv of a PCP ligand. Alternatively, palladium PCP complexes can
also be generated via an oxidative addition route. Addition of 2 equiv of PCP ligands based on 3,5-
diamino-4-chloroisobutylbenzoate to Pd2(dba)3 affords the respective Pd(PCP)Cl pincer complexes in
high yields. X-ray structures of representative Ni, Pd, and Pt PCP complexes have been determined.
Finally, the use of the palladium complexes as catalysts for the Suzuki-Miyaura coupling of some aryl
bromides and phenyl boronic acid has been examined.
In this family of ligands steric, electronic, and stereochemical
parameters can be manipulated by modifications of the benzylic
positions and/or phosphino R groups so as to control the reac-
tivity at the metal center. Stereochemical parameters, however,
are comparatively difficult to modify and often require tedious
multistep syntheses and expensive starting materials.3,5a,10-12 As
part of our effort to create novel pincer ligands in which the
steric, electronic, and stereochemical properties can be easily
modulated, we have designed a synthetic route for the high-
yield synthesis of a new generation of PCP ligands, based on
1,3-diaminobenzenes and R2PCl, which contain dialkyl or diaryl
phosphines as well as various P-O bond-containing achiral and
chiral phosphite units.13 This methodology has recently been
applied to the preparation of several PNP pincer-type ligands
based on 2,6-diaminopyridine.14 The new PCP ligands are
applied to the synthesis of a series of square-planar Ni(II),
Pd(II), and Pt(II) PCP complexes. In addition, preliminary
investigations of the Suzuki-Miyaura coupling of aryl and alkyl
bromides and phenylboronic acid catalyzed by some palladium
PCP complexes are also presented.
Introduction
Tridentate PCP ligands comprising an anionic aryl ring that
is ortho,ortho-disubstituted with -CH2PR2 units are widely
utilized ligands in transition metal chemistry and catalysis.1,2-9
* To whom correspondence should be addressed. E-mail: kkirch@
mail.zserv.tuwien.ac.at.
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Chem. 1999, 111, 918; Angew. Chem., Int. Ed. 1999, 38, 870. (d) Singleton,
J. T. Tetrahedron 2003, 59, 1837. (e) Vigalok, A.; Milstein, D. Acc. Chem.
Res. 2001, 34, 798. (f) Milstein, D. Pure Appl. Chem. 2003, 75, 2003. (g)
Jensen, C. M. Chem. Commun. 1999, 2443.
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Chim. Acta 1981, 48, 125. (b) Steffey, B. D.; Miedaner, A.; Maciejewski-
Farmer, M. L.; Bernatis, P. R.; Herring, A. M.; Allured, V. S.; Carperos,
V.; DuBois, D. L. Organometallics 1994, 13, 4844. (c) Hahn, C.; Sieler,
J.; Taube, R. Chem. Ber. 1997, 130, 939. (d) Hahn, C.; Vitagliano, A.;
Giordano, F.; Taube, R. Organometallics 1998, 17, 2060. (e) Hahn, C.;
Spiegler, M.; Herdtweck, E.; Taube, R. Eur. J. Inorg. Chem. 1999, 435.
(3) Jiang, Q.; Van Plew, D.; Murtuza, S.; Zhang, X. Tetrahedron Lett.
1996, 37, 797.
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Vasapollo, G. Inorg. Chim. Acta 1982, 63, 225. (b) Sacco, A.; Vasapollo,
G.; Nobile, C.; Piergiovanni, A.; Pellinghelli, M. A.; Lanfranchi, M. J.
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(5) (a) Rahmouni, N.; Osborn, J. A.; De Cian, A.; Fisher, J.; Ezzamarty,
A. Organometallics 1998, 17, 2470. (b) Sablong, R.; Newton, C.; Dierkes,
P.; Osborn, J. A. Tetrahedron Lett. 1996, 37, 4933. (c) Sablong, R.; Osborn,
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17, 4374. (b) Longmire, J. M.; Zhang, X. Tetrahedron Lett. 1997, 38, 1725.
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10.1021/om060289e CCC: $33.50 © 2006 American Chemical Society
Publication on Web 07/01/2006

3818 Organometallics, Vol. 25, No. 16, 2006
Benito-Garagorri et al.
Scheme 1
Figure 1. Structural view of Ni(PCP-But)Cl (4c) showing 50%
thermal ellipsoids (C-bonded H atoms are omitted for clarity).
Selected bond lengths (Å) and bond angles (deg): Ni-C(1) 1.912-
(2), Ni-P(1) 2.213(1), Ni-P(2) 2.201(1), Ni-Cl 2.232(1), P(1)-
Ni-P(2) 166.82(3), C(1)-Ni-P(1) 84.0(1), C(1)-Ni-P(2) 83.5(1),
Cl-Ni-P(1) 96.46(2), Cl-Ni-P(2) 96.15(2).
Scheme 2a
ligands. Palladium PCP complexes 5a-f, 6a, 6d, and 6e are
easily prepared by treatment of Pd(COD)Cl2 with 1 equiv of
the corresponding ligands 1 and 2, respectively, according to
Scheme 2. The analogous platinum PCP complexes 7a-c were
prepared in similar fashion by treatment of Pt(COD)Br2 with
ligands 1a-c in the presence of 1 equiv of NEt3. Palladium
PCP complexes 8a-d, featuring a coordinated TFA ligand (TFA
) CF3COO-), are obtained by the reaction of Pd(TFA)2 with 1
equiv of 1a-d in THF at room temperature for 3 h. Surprisingly,
in the case of 1e and 1f the corresponding PCP complexes turned
out to be unstable, and decomposition to several intractable
materials took place.
Alternatively, palladium PCP complexes could also be
generated via an oxidative addition route. Accordingly, addition
of 2 equiv of ligands 3a and 3e to Pd2(dba)3 in toluene at 80
°C for 12 h afforded complexes 9a and 9e, respectively, in high
isolated yields (Scheme 3). Due to the introduction of a COO-
i-Bu substituent into the arene ring, these palladium PCP
complexes exhibit very high solubility in most organic solvents,
including CH2Cl2 and Et2O.
a (i) NiCl2‚6H2O, EtOH, reflux, 12 h, (ii) Pd(COD)Cl2, toluene, 110
°C, 5 h; (iii) Pt(COD)Br2, NEt3 (1 equiv), toluene, 110 °C, 5 h; (iv)
Pd(TFA)2, THF, rt, 3 h.
Scheme 3
All these complexes are thermally stable and can be handled
in air. They have been characterized by a combination of ele-
mental analysis and 1H, 13C{1H}, and 31P{1H} NMR spectros-
copy. In addition, the solid-state structures of Ni(PCP-Ph)Cl
(4a as the solvate 4a‚1/2C6H6), Ni(PCP-But)Cl (4c), Pd(PCP-
Ph)Cl (5a as the solvate 5a‚2DMF), Pd(PCPF-Ph)Cl (6a as
the solvate 6a‚CH3CN), Pt(PCP-Ph)Cl (7a as the cocrystal
7a‚[NEt3H]Br‚CH2Cl2; this compound crystallized spontane-
ously when the reaction of Pt(COD)Br2 with N,N′-bis(di-
phenylphosphino)-1,3-benzenediamine and triethylamine was
carried out in dichloromethane), Pd(PCP-Pri)(TFA) (8b), and
Pd(PCP-BIPOL)(TFA) (8d as the solvate 8d‚2Et2O) were
determined by single-crystal X-ray diffraction. ORTEP diagrams
of 4c, 6a, 8b, and 8d are depicted in Figures 1-4, with selected
bond distances and angles reported in the captions. Structural
views of 4a, 5a, and 7a are given in the Supporting Information,
Figures S1-S3. The molecular structures of all these compounds
show the metal in a typical distorted-square-planar conformation
with the PCP ligands coordinated to the metal center in a
tridentate meridional mode. The aminophosphine nitrogen atoms
are typically active hydrogen bond donors to suitable acceptor
atoms, e.g., an Et2O solvent oxygen in the case of 8d‚2Et2O,
as shown in Figure 4. It is remarkable that the complex
Pd(PCP-Pri)(TFA) (8b) (Figure 3) is stabilized in the solid state
by a clear-cut intramolecular donor coordination between the
TFA oxygen O(2) and the phosphine atom P(1).15 The corre-
Results and Discussion
The new PCP ligands 1, 2, and 3 are conveniently prepared
by treatment of 1,3-diaminobenzene, 5-trifluoromethyl-1,3-
diaminobenzene, and 3,5-diamino-4-chloroisobutylbenzoate,
respectively, with the respective R2PCl (2 equiv) in the presence
of NEt3 and/or n-BuLi (Scheme 1). All PCP ligands are air stable
in the solid state and in oxygen-free solutions. They have been
characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy.
Most diagnostic is the 31P{1H} NMR spectrum, exhibiting one
singlet in the range of 27.0 to 146.7 ppm.
From the array of PCP ligands 1-3 we exemplarily tested
some for the complexation with various Ni, Pd, and Pt
precursors as shown in Schemes 2 and 3. The PCP complexes
of Ni(II) (4a-c) were prepared by the reaction of NiCl2‚6H2O
with the ligands 1a-c according to Scheme 2. It is important
to note that small amounts of water apparently do not cause
hydrolysis resulting in cleavage of the P-N bonds of the PCP

Ni(II), Pd(II), and Pt(II) PCP Pincer Complexes
Organometallics, Vol. 25, No. 16, 2006 3819
Figure 4. Structural view of Pd(PCP-BIPOL)(TFA)‚2Et2O (8d‚
2Et2O) showing 50% thermal ellipsoids (C-bonded H atoms and
second Et2O omitted for clarity). Selected bond lengths (Å) and
bond angles (deg): Pd-C(1) 2.003(3), Pd-P(1) 2.262(1), Pd-P(2)
2.299(1), Pd-O(5) 2.124(2), P(1)-N(1) 1.630(3), P(2)-N(2) 1.631-
(3), P(1)-Pd-P(2) 159.20(3), C(1)-Pd-P(1) 80.5(1), C(1)-Pd-
P(2) 79.4(1), O(5)-Pd-P(1) 95.3(1), O(5)-Pd-P(2) 104.4(1);
hydrogen bonds N(1)‚‚‚O(7) 2.893(4), N(2)‚‚‚O(6′) 2.868(3) (not
shown).
Figure 2. Structural view of Pd(PCPF-Ph)Cl‚CH3CN (6a‚CH3CN)
showing 50% thermal ellipsoids (C-bonded H atoms and CH3CN
omitted for clarity). Selected bond lengths (Å) and bond angles
(deg): Pd-C(1) 2.000(2), Pd-P(1) 2.2768(3), Pd-P(2) 2.2831-
(3), Pd-Cl 2.3950(3), P(1)-Pd-P(2) 163.18(1), C(1)-Pd-P(1)
81.63(3), C(1)-Pd-P(2) 81.97(3), Cl-Pd-P(2) 98.42(1), Cl-Pd-
P(2) 98.16(1).
Table 1. Yields of the Suzuki-Miyaura Cross Coupling of
Aryl Bromides with Phenyl Boronic Acid Catalyzed by 5a,
5d, 8a, and 8da
entry
R
catalyst
yield (%)
TON
1
2
3
4
5
6
7
8
4-COMe
5a (0.01)
5a (0.0001)
5a (0.00001)
5a (0.01)
5a (0.001)
5a (0.0001)
5a (0.01)
5a (0.001)
5a (0.0001)
5a (0.01)
5a (0.01)
5a (0.01)
5a (0.01)
5d (0.01)
5d (0.01)
8a (0.01)
8a (0.001)
8a (0.01)
8a (0.1)
>99
>99
97
94
77
18
>99
72
44
81
65
68
9.9 × 105
9.9 × 105
9.7 × 106
9900
4-COMe
4-COMe
4-OMe
4-OMe
4-OMe
4-Me
4-Me
4-Me
4-NO2
7.7 × 104
1.8 × 105
9900
7.2 × 104
4.4 × 105
8100
6500
6800
7400
9900
9900
Figure 3. Structural view of Pd(PCP-Pri)(TFA) (8b) showing 50%
thermal ellipsoids (H atoms omitted for clarity). Selected bond
lengths (Å) and bond angles (deg): Pd-C(1) 1.988(1), Pd-P(1)
2.2988(4), Pd-P(2) 2.2830(4), Pd-O(1) 2.131(1), P(1)-N(1)
1.685(1), P(2)-N(2) 1.676(1), P(1)-Pd-P(2) 164.45(2),
C(1)-Pd-P(1) 82.34(5), C(1)-Pd-P(2) 82.30(5), O(1)-Pd-P(1)
103.40(3), O(1)-Pd-P(2) 91.79(3); donor interaction O(2)‚‚‚P(1)
3.114(1).
9
10
11
12
13
14
15
16
17
18
19
20
21
2-Et
2-bromopyridine
1-bromododecane
4-COMe
4-OMe
4-COMe
4-COMe
4-Me
4-OMe
4-COMe
4-COMe
74
>99
>99
>99
15
70
88
9900
1.5 × 104
7000
sponding distance P(1)-O(2) ) 3.114(1) Å is shorter than the
distance limit of 3.35 Å given by Holmes (2004).15 This
behavior is at variance with complex 8d (Figure 4), where
phosphorus is more polarized by one P-N and two P-O bonds
and less prone to such interaction with the result that the TFA
group points away from phosphorus and adopts an orientation
inclined to the PCP main plane.
880
9900
3600
8d (0.01)
8d (0.001)
>99
36
a Reaction conditions: 1.0 mmol of bromide, 1.5 mmol of PhB(OH)2,
2.0 mmol of K2CO3, 5 mL of toluene, 110 °C, reaction time is 16 h, yields
represent isolated yields (average of at least three experiments) of
1
compounds estimated to be g95% pure as judged by H NMR.
Palladium complexes containing PCP ligands have been found
to be excellent catalysts for various C-C bond forming reactions
including the Heck reaction16 and the Suzuki-Miyaura cou-
pling.17 Accordingly, the catalytic activity of some of the
palladium PCP complexes (5a, 5d, 8a, and 8d) was tested in
the Suzuki-Miyaura coupling of aryl and alkyl bromides and
phenylboronic acid. These complexes show high activity in the
catalytic coupling of aryl and alkyl bromides with phenylboronic
acid (Table 1). The catalyst remains highly active after the reac-
tion is complete, and upon addition of more substrates, cataly-
sis is resumed, leading to the coupled product in quantitative
yield at essentially the same rate. In general, the chloro com-
plexes 5a and 5d are better catalysts than the respective TFA
complexes 8a and 8d. The reaction of 4-bromoacetophenone
(15) Holmes, R. R. Acc. Chem. Res. 2004, 37, 746, and references therein.
(16) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein, D. J. Am. Chem.
Soc. 1997, 119, 11687.
(17) Bedford, R. B.; Draper, S.; Scully, P. N.; Welch, S. L. New J. Chem.
2000, 24, 745.

3820 Organometallics, Vol. 25, No. 16, 2006
Benito-Garagorri et al.
131.3 (d, J ) 20.7 Hz, CPPh), 130.1 (CPh), 129.1 (CPPh), 128.6 (d,
J ) 6.5 Hz, CPPh), 107.3 (d, J ) 13.8 Hz, CPh), 103.3 (t, J ) 13.4
Hz, CPh). 31P{1H} NMR (δ, CDCl3, 20 °C): 28.6.
with phenylboronic acid and 5a as catalyst proceeds with 97%
isolated yield even with 0.00001 mol % catalyst (TON ) 9.7
× 106), while the electronically deactivated and thus more
challenging substrate 4-bromoanisole can still be coupled in 18%
yield with a catalyst loading of 0.0001 mol % (TON ) 1.8 ×
105). These conditions have not been optimized, and thus tuning
of steric and electronic properties by ligand variations is
expected to result in more enhanced catalytic reactivity.
N,N′-Bis(diisopropylphosphino)-1,3-benzenediamine (PCP-
Pri) (1b). This ligand has been prepared analogously to 1a with
triethylamine (8.0 mL, 66 mmol), 1,3-diaminobenzene (3.6 g, 33
mmol), and PPri2Cl (10.0 g, 66 mmol) as the starting materials.
Yield: 8.8 g (79%). Anal. Calcd for C18H33N2P2: C, 63.70; H,
1
9.80; N, 8.25. Found: C, 63.24; H, 10.01; N, 8.15. H NMR (δ,
CDCl3, 20 °C): 6.92 (t, J ) 8.0 Hz, 1H, Ph4), 6.64 (t, J ) 2.2 Hz,
1H, Phipso), 6.37 (d, J ) 8.0 Hz, 2H, Ph3,5), 3.63 (d, J ) 10.5 Hz,
2H, NH), 1.75-1.68 (m, 4H, CH(CH3)2), 1.12-1.02 (m, 24H,
CH(CH3)2). 13C{1H} NMR (δ, CDCl3, 20 °C): 149.6 (d, J ) 17.2
Hz, CPh), 129.5 (CPh), 106.5 (d, J ) 12.1 Hz, CPh), 103.4 (t, J )
12.4 Hz, CPh), 26.6 (d, J ) 9.8 Hz, CH(CH3)2), 18.7 (d, J ) 20.1
Hz, CH(CH3)2), 17.1 (d, J ) 7.5 Hz, CH(CH3)2). 31P{1H} NMR
(δ, CDCl3, 20 °C): 48.9.
N,N′-Bis(di-tert-butylphosphino)-1,3-benzenediamine (PCP-
But) (1c). Triethylamine (6.0 mL, 42 mmol) was added to a solution
of 1,3-diaminobenzene (0.6 g, 5.3 mmol) in THF; the reaction
mixture was then cooled to 0 °C, and PBut2Cl (2.0 mL, 10.5 mmol)
was added. Upon cooling to -80 °C, n-BuLi (10.5 mmol, 5.0 mL
of a 2.1 M solution in hexane) was added and the reaction was
allowed to reach room temperature and stirred overnight. After that,
the solution was filtered and the solvent was removed under
vacuum; the white solid obtained was used without further
purification. Yield: 2.0 g (96%). Anal. Calcd for C22H42N2P2: C,
66.64; H, 10.68; N, 7.06. Found: C, 67.11; H, 10.43; N, 10.45. 1H
NMR (δ, CD2Cl2, 20 °C): 6.89 (t, J ) 7.9 Hz, 1H, Ph4), 6.73 (t,
J ) 2.3 Hz, 1H, Phipso), 6.36 (d, J ) 7.9 Hz, 2H, Ph3,5), 3.96 (d,
J ) 11.0 Hz, 2H, NH), 1.12 (d, J ) 11.9 Hz, 36H, C(CH3)3).
13C{1H} NMR (δ, CD2Cl2, 20 °C): 150.1 (d, J ) 16.7 Hz, CPh),
129.6 (CPh), 106.5 (d, J ) 12.1 Hz, CPh), 103.5 (t, J ) 11.2 Hz,
CPh), 34.2 (d, J ) 19.0 Hz, C(CH3)3), 28.1 (d, J ) 14.9 Hz,
C(CH3)3). 31P{1H} NMR (δ, CD2Cl2, 20 °C): 59.3.
Concluding Remarks
In sum, we have shown that both achiral and chiral PCP
ligands are conveniently generated by reacting readily available
parent 1,3-diaminobenzene or derivatives thereof with a series
of R2PCl compounds. These new ligands form very stable
square-planar Ni(II), Pd(II), and Pt(II) PCP complexes. The
palladium complexes are efficient catalysts for the coupling of
aryl and alkyl bromides and phenylboronic acid. In some
instances TONs in the range of 105-106 have been achieved
that are among the highest reported thus far. We are currently
studying our new PCP ligands in conjunction with other
transition metals including Mo, W, Fe, Ru, Rh, and Ir. These
studies will be reported in due course.
Experimental Section
General Procedures. All manipulations were performed under
an inert atmosphere of argon by using Schlenk techniques. The
solvents were purified according to standard procedures.18 The
starting materials PPh2Cl, PPri2Cl, and PBut2Cl, 1,3-diamino-
benzene, 5-triflouromethyl-1,3-diaminobenzene, and 3,5-diamino-
4-chloroisobutylbenzoate were purchased from Aldrich and used
without further purification. 2-Chlorodibenzo[d,f][1,3,2]dioxaphos-
phepine,19 S-2-chlorodinaphtho[2,1-d:1′2′-f][1,3,2]dioxaphosphepine,20
2-chloro-(4R,5R)-dicarbomethoxy-1,3,2-dioxaphospholane, and 2-chlo-
ro-(4R,5R)-dicarboisopropoxy-1,3,2-dioxaphospholane21 were pre-
pared according to the literature. The deuterated solvents were
N,N′-Bis(dibenzo[d,f][1,3,2]dioxaphosphepine)-1,3-benzene-
diamine (PCP-BIPOL) (1d). 1,3-Diaminobenzene (0.4 g, 4.0
mmol) and triethylamine (1.2 mL, 8.0 mmol) were dissolved in
THF (25 mL), and the solution was cooled to 0 °C. 2-Chlorodibenzo-
[d,f][1,3,2]dioxaphosphepine (2.0 g, 8.0 mmol) was then added
dropwise under ice cooling, and a white precipitate was formed
immediately. The mixture was stirred at 50 °C for 16 h. The
precipitate of triethylammonium chloride was removed by filtration,
the solvent evaporated, and the residue dried in under vacuum.
Yield: 1.94 g (91%). Anal. Calcd for C30H22N2O4P2: C, 67.17; H,
1
purchased from Aldrich and dried over 4 Å molecular sieves. H,
13C{1H}, and 31P{1H} NMR spectra were recorded on a Bruker
AVANCE-250 spectrometer and were referenced to SiMe4 and
1
H3PO4 (85%), respectively. H and 13C{1H} NMR signal assign-
ments were confirmed by 1H-COSY, 135-DEPT, and HMQC-
(1H-13C) experiments.
N,N′-Bis(diphenylphosphino)-1,3-benzenediamine (PCP-Ph)
(1a). To a suspension of 1,3-diaminobenzene (5.0 g, 46 mmol) in
toluene (75 mL) was added triethylamine (11.2 mL, 92 mmol). The
mixture was then cooled to 0 °C, PPh2Cl (16.5 mL, 92 mmol) was
added in a dropwise fashion, and the solution was allowed to reach
room temperature and stirred overnight at 80 °C. After that, the
solution was filtered and the solvent was removed under vacuum.
The remaining yellow oil was recrystallized from toluene/n-hexane
(1:1). Yield: 13.2 g (84%). Anal. Calcd for C30H26N2P2: C, 75.62;
H, 5.50; N, 5.88. Found: C, 75.24; H, 5.16; N, 6.15. 1H NMR (δ,
CDCl3, 20 °C): 7.43-7.32 (m, 20H, PPh), 6.99 (t, J ) 8.0 Hz,
1H, Ph4), 6.72 (t, J ) 2.1 Hz, 1H, Phipso), 6.50 (d, J ) 8.0 Hz, 2H,
Ph3,5), 4.39 (d, J ) 8.2 Hz, 2H, NH). 13C{1H} NMR (δ, CDCl3, 20
°C): 147.7 (d, J ) 16.5 Hz, CPh), 140.2 (d, J ) 11.9 Hz, CPPh),
1
4.13; N, 5.22. Found: C, 67.24; H, 4.16; N, 5.13. H NMR (δ,
CDCl3, 20 °C): 7.50-7.10 (m, 16H, Biph), 7.03 (t, J ) 7.9 Hz,
1H, Ph4), 6.67 (d, J ) 6.5 Hz, Ph3,5), 6.37 (d, J ) 7.8 Hz, Phipso),
5.25 (d, J ) 4.9 Hz, 2H, NH). 13C{1H} NMR (δ, CDCl3, 20 °C):
149.5 (CBiph), 142.8, (CPh) 142.5 (CPh), 131.7 (CBiph), 131.6 (CBiph),
130.5 (CPh), 129.8 (CBiph), 129.3 (CBiph), 125.3 (CBiph), 122.3 (CBiph),
111.2 (d, J ) 13.9 Hz, CPh), 107.5 (t, J ) 12.2 Hz, CPh). 31P{1H}
NMR (δ, CDCl3, 20 °C): 146.7.
N,N′-Bis(4R,5R-dicarbomethoxy-1,3,2-dioxaphospholane)-1,3-
diaminobenzene (PCP-TARMe) (R,R-1e). To a solution of 1,3-
diaminobenzene (446 mg, 4.12 mmol) and triethylamine (1.2 mL,
8.6 mmol) in THF (12 mL) was added dropwise 2-chloro-(4R,5R)-
dicarbomethoxy-1,3,2-dioxaphospholane (2.0 g, 8.24 mmol) under
ice cooling. The mixture was stirred for 16 h at room temperature.
The precipitate of triethylammonium chloride was removed by
filtration, the solvent evaporated, and the residue dried in under
vacuum. The product was a highly viscous yellow oil, which
solidified after a few days of storage in the refrigerator. Yield: 2.09
g (98%). Anal. Calcd for C18H22N2O12P2: C, 41.55; H, 4.26; N,
(18) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: New York, 1988.
(19) (a) Tsarev, V. N.; Kabro, A. A.; Moieseev, S. K.; Kalinin, V. N.;
Bondarev, O. G.; Davankov, V. A.; Gavrilov, K. N. Russ. Chem. Bull., Int.
Ed. 2004, 53, 814. (b) van Rooy, A.; Kamer, P. C. J.; van Leeuwen, P. W.
N. M.; Goubitz, K.; Fraanje, J.; Veldman, N.; Spek, A. Organometallics
1996, 15, 835.
(20) Sablong, R.; Newton, C.; Dierkes, P.; Osborn, J. A. Tetrahedron
Lett. 1996, 37, 4933.
(21) Kadyrov, R.; Heller, D.; Selke, R. Tetrahedron: Asymmetry 1998,
9, 329.
1
5.38. Found: C, 42.06; H, 4.36; N, 5.45. H NMR (δ, CDCl3, 20
°C): 7.05 (t, J ) 7.7 Hz, Ph4), 6.63 (s, 2H, Ph3,5), 6.59 (s, 1H,
Phipso), 6.28 (d, J ) 3.2 Hz, 2H, NH), 4.97 (t, J ) 3.4 Hz, 2H,

Ni(II), Pd(II), and Pt(II) PCP Pincer Complexes
Organometallics, Vol. 25, No. 16, 2006 3821
CH), 4.81 (d, J ) 4.3 Hz, 1H, GH), 4.76 (d, J ) 4.4 Hz, 1H, CH),
3.87 (s, 6H, CH3), 3.85 (s, 6H, CH3). 13C{1H} NMR (δ, CDCl3,
20 °C): 171.5, (CO) 169.2 (CO), 142.3 (d, J ) 17.3 Hz, CPh),
131.0 (CPh), 111.5 (d, J ) 13.9 Hz, CPh), 107.4 (t, J ) 12.5 Hz,
CPh), 76.8 (CH), 76.7 (CH), 76.3 (CH), 76.1 (CH), 53.4, (CH3),
53.1 (CH3). 31P{1H} NMR (δ, CDCl3, 20 °C): 145.2.
N,N′-Bis(diphenylphosphino)-3,5-diamino-4-chloroisobutyl-
benzoate (PCPE-Ph) (3a). Triethylamine (0.3 mL, 2.10 mmol) was
added to a solution of 3,5-diamino-4-chloroisobutylbenzoate (250
mg, 1.03 mmol) in THF; the reaction mixture was then cooled to
0 °C and PPh2Cl (0.4 mL, 2.10 mmol) was added, whereupon a
white solid immediately precipitated. The mixture was stirred
overnight at 50 °C and filtered, and the solvent was removed under
vacuum, yielding a white solid. Yield: 486 mg (82%). Anal. Calcd
for C35H33ClN2O2P2: C, 64.80; H, 5.44; N, 4.58. Found: C, 64.84;
H, 5.56; N, 4.39. 1H NMR (δ, CDCl3, 20 °C): 7.61-7.36 (m, 23H,
PPh, Ph3,5 and Phipso), 5.10 (d, J ) 7.3 Hz, 2H, NH), 4.02 (q, J )
6.7 Hz, 2H, CH2), 2.0 (m, J ) 6.7 Hz, 1H, CH(CH3)2), 0.95 (d, J
) 6.7 Hz, 6H, CH(CH3)2). 13C{1H} NMR (δ, CDCl3, 20 °C): 166.3
(CO), 143.4 (t, J ) 19.6 Hz, CPh), 139.4 (d, J ) 12.6 Hz, CPPh),
131.2 (d, J ) 20.9 Hz, CPPh), 130.3 (CPh), 129.3 (CPPh), 128.6 (t, J
) 6.3 Hz, CPPh), 107.2 (CPh), 106.4 (CPh), 70.9 (CH2), 27.8
(CH(CH3)2), 19.1 (CH(CH3)2). 31P{1H} NMR (δ, CDCl3, 20 °C):
30.6.
N,N′-Bis(4R,5R-dicarboisopropoxy-1,3,2-dioxaphospholane)-
1,3-benzenediamine (PCP-TARPr) (R,R-1f). This ligand has been
prepared analogously to R,R-1e with 1,3-diaminobenzene (362 mg,
3.35 mmol), 2-chloro-(4R,5R)-dicarboisopropoxy-1,3,2-dioxaphos-
pholane (2.0 g, 6.7 mmol), and triethylamine (1.0 mL, 7.0 mmol)
as the starting materials. Yield: 2.1 g (99%). Anal. Calcd for
C26H38O12N2P2: C, 49.37; H, 6.05; N, 4.43. Found: C, 49.46; H,
1
6.26; N, 4.31. H NMR (δ, CDCl3, 20 °C): 7.03 (t, J ) 8.0 Hz,
1H, Ph4), 6.59 (s, 2H, Ph3,5), 6.56 (s, 1H, Phipso), 6.32 (d, J ) 4.4
Hz, 2H, NH), 5.13 (m, 4H, CH(CH3)2), 4.83 (m, 2H, CH), 4.63 (d,
J ) 5.1 Hz, 2H, CH), 4.59 (d, J ) 5.1 Hz, 2H, CH) 1.31 (m, 24H,
CH(CH3)2). 13C{1H} NMR (δ, CDCl3, 20 °C): 170.8 (CO), 168.1
(CO), 142.5 (d, J ) 17.2 Hz, CPh), 130.0 (CPh), 111.1 (d, J ) 13.8
Hz, CPh), 106.92 (t, J ) 12.4 Hz, CPh), 76.8 (CH), 76.7 (CH), 70.8
(CH(CH3)2), 70.3 (CH(CH3)2), 21.6 (m, CH(CH3)2). 31P{1H} NMR
(δ, CDCl3, 20 °C): 144.1.
N,N′-Bis(4R,5R-dicarbomethoxy-1,3,2-dioxaphospholane)-3,5-
diamino-4-chloroisobutylbenzoate (PCPE-TarMe) (R,R-3e). This
ligand has been prepared analogously to 3a with 3,5-diamino-4-
chloroisobutylbenzoate (250 mg, 1.03 mmol), 2-chloro-(4R,5R)-
dicarbomethoxy-1,3,2-dioxaphospholane (500 mg, 2.06 mmol), and
triethylamine (0.4 mL, 3.0 mmol) as the starting materials. Yield:
660 mg (98%). Anal. Calcd for C23H29ClN2O14P2: C, 42.18; H,
N,N′-Bis(diphenylphosphino)-5-(trifluoromethyl)-1,3-benzene-
diamine (PCPF-Ph) (2a). Triethylamine (0.4 mL, 2.84 mmol) was
added to a solution of 5-(trifluoromethyl)-1,3-benzenediamine (250
mg, 1.42 mmol) in THF; the reaction mixture was then cooled to
0 °C and PPh2Cl (0.5 mL, 2.84 mmol) was added, whereupon a
white solid immediately precipitated. The mixture was stirred
overnight at room temperature. Insoluble materials were then
removed by filtration. The solvent was removed under vacuum,
yielding a colorless oil. Yield: 725 mg (94%). Anal. Calcd for
C31H24F3N2P2: C, 68.51; H, 4.45; N, 5.15. Found: C, 68.59; H,
4.36; N, 5.35. 1H NMR (δ, CDCl3, 20°C): 7.81-7.75 (m, 2H, PPh),
7.63-7.57 (m, 2H, PPh), 7.43-7.24 (m, 16H, PPh), 6.88 (s, 1H,
Phipso), 6.76 (s, 1H, Ph3,5), 4.56 (d, J ) 8.2 Hz, 2H, NH). 13C{1H}
NMR (δ, CDCl3, 20 °C): 148.2 (d, J ) 18.3 Hz, CPh), 139.5 (d, J
) 11.4 Hz, CPPh), 131.2 (d, J ) 20.85 Hz, CPPh), 130.3 (CPh), 129.3
(CPPh), 128.6 (t, J ) 5.4 Hz, CPPh), 105.5 (t, J ) 16.4 Hz, CPh),
103.7 (t, J ) 4.4 Hz, CPh). 31P{1H} NMR (δ, CDCl3, 20 °C): 27.0.
1
4.46; N, 4.28. Found: C, 41.98; H, 4.66; N, 4.19. H NMR (δ,
CDCl3, 20 °C): 6.89 (d, J ) 3.5 Hz, Ph3,5), 6.81 (d, J ) 3.6 Hz,
2H, NH), 5.00 (m, 2H, CH), 4.83-4.77 (m, 2H, CH), 4.04 (t,
i
J ) 6.3 Hz, 2H, CH2 Bu), 3.87(s, 6H, CH3) 3.84 (s, 6H, CH3),
i
2.06 (m, 1H, CHiBu), 0.98 (d, J ) 6.8 Hz, 6H, CH3 Bu). 13C{1H}
NMR (δ, CDCl3, 20 °C): 171.2 (COOCH3), 168.8 (COOCH3),
165.6 (COOiBu), 143.7 (CPh), 139.7 (CPh), 139.4 (CPh), 133.4 (CPh),
109.6 (CPh), 77.0 (CH), 76.8 (CH), 76.7 (CH), 76.4 (CH), 71.1
i
i
(CH2 Bu), 53.5 (CH3), 53.2 (CH3), 27.8 (CHiBu), 19.2 (CH3 Bu).
31P{1H} NMR (δ, CDCl3, 20 °C): 143.7.
Ni(PCP-Ph)Cl (4a). To a suspension of 1a (300 mg, 0.63 mmol)
in ethanol (10 mL) was added NiCl2‚6H2O (78 mg, 0.63 mmol),
whereupon the solution turned orange. The mixture was refluxed
overnight, and the precipitated orange solid was collected on a glass
frit, washed twice with pentane, and dried under vacuum. Yield:
316 mg (88%). Anal. Calcd for C30H25ClN2NiP2: C, 63.25; H, 4.42;
N, 4.92. Found: C, 63.04; H, 4.32; N, 5.10. 1H NMR (δ, C6D6, 20
°C): 8.08 (d, J ) 5.5 Hz, 2H, NH), 7.56 (q, J ) 6.3 Hz, 8H, Ph),
7.07-7.04 (m, 12H, Ph), 6.90 (s, 1H, Ph4), 6.39 (d, J ) 7.6 Hz,
2H, Ph3,5). 13C{1H} NMR (δ, C6D6, 20 °C): 159.2 (t, J ) 17.0
Hz, CPh), 134.2 (t, J ) 23.9 Hz, CPPh), 132.5 (t, J ) 6.9 Hz, CPPh),
131.8 (d, J ) 2.3 Hz, CPPh), 130.7 (d, J ) 11.5 Hz, CPh), 128.5 (t,
J ) 12.4 Hz, CPPh), 103.0 (t, J ) 8.3 Hz, CPh). 31P{1H} NMR (δ,
C6D6, 20 °C): 77.8.
Ni(PCP-Pri)Cl (4b). This complex has been prepared analo-
gously to 4a with NiCl2‚6H2O (137 mg, 0.58 mmol) and 1b (200
mg, 0.58 mmol) as the starting materials. Yield: 181 mg (72%).
Anal. Calcd for C18H33ClN2NiP2: C, 49.86; H, 7.67; N, 6.46.
Found: C, 49.74; H, 7. 50; N, 7.02. 1H NMR (δ, CD2Cl2, 20 °C):
6.61 (s, 1H, Ph4), 5.94 (s, 2H, Ph3,5), 3.95 (s, 2H, NH), 2.22 (s,
4H, CH(CH3)2, 1.36 (s, 24H, CH(CH3)2). 13C{1H} NMR (δ,
CD2Cl2, 20 °C): 160.7 (CPh), 131.1 (CPh), 127.3 (CPh), 101.1 (CPh),
26.3 (CH(CH3)2), 17.8 (CH(CH3)2). 31P{1H} NMR (δ, CD2Cl2, 20
°C): 110.8.
N,N′-Bis(dibenzo[d,f][1,3,2]dioxaphosphepine)-5-(trifluoro-
methyl)-1,3-benzenediamine (PCPF-BIPOL) (2d). This ligand has
been prepared analogously to 2a with 5-(trifluoromethyl)-1,3-
benzenediamine (250 mg, 1.42 mmol), 2,2′-biphenylylenephos-
phochloridite (712 mg, 2.84 mmol), and triethylamine (0.4 mL,
3.0 mmol) as the starting materials. Toluene instead of THF was
used as the solvent. Yield: 760 mg (89%). Anal. Calcd for
C31H21F3N2O4P2: C, 61.60; H, 3.50; N, 4.63. Found: C, 61.64; H,
1
3.70; N, 4.65. H NMR (δ, CDCl3, 20 °C): 7.52-7.20 (m, 16H,
Biph), 6.87 (s, 2H, Ph3,5), 6.81 (s, 1H, Phipso), 5.42 (s, 2H, NH).
13C{1H} NMR (δ, CDCl3, 20 °C): 149.6 (CBiph), 148.2 (CPh), 143.8
(CPh), 143.6 (CPh), 131.8 (CBiph), 130.5 (CBiph), 129.7 (CBiph), 125.8
(CBiph), 122.1 (CBiph), 109.4 (t, J ) 11.4 Hz, CPh), 107.5 (d, J )
12.1 Hz, CPh). 31P{1H} NMR (δ, CDCl3, 20 °C): 145.1.
N,N′-Bis(4R,5R-dicarbomethoxy-1,3,2-dioxaphospholane)-5-
(trifluoromethyl)-1,3-benzenediamine (PCPF-TARMe) (R,R-2e).
This ligand was prepared analogously to 2a with 5-(trifluoromethyl)-
1,3-phenylenediamine (250 mg, 1.42 mmol), 2-chloro-(4R,5R)-
dicarbomethoxy-1,3,2-dioxaphospholane (688 mg, 2.84 mmol), and
triethylamine (0.4 mL, 3.0 mmol) as the starting materials. Yield:
670 mg (80%). Anal. Calcd for C19H21F3N2O12P2: C, 38.79; H,
Pd(PCP-Ph)Cl (5a). Pd(COD)Cl2 (179 mg, 0.63 mmol) was
added to a solution of 1a (300 mg, 0.63 mmol) in toluene (15
mL), and the mixture was refluxed for 5 h, whereupon a yellow
solid precipitated, which was collected on a glass frit and washed
twice with Et2O (10 mL). Yield: 350 mg (90%). Anal. Calcd for
C30H25ClN2P2Pd: C, 58.37; H, 4.08; N, 4.54. Found: C, 58.24; H,
1
3.60; N, 4.76. Found: C, 38.88; H, 3.77; N, 4.81. H NMR (δ,
CDCl3, 20 °C): 6.80 (s, 2H, Ph3,5), 6.54 (s, 2H, NH), 6.47 (s, 1H,
Phipso), 4.96 (m, 2H, CH), 4.83-4.77 (m, 2H, CH), 3.87 (s, 6H,
CH3), 3.84 (s, 6H, CH3). 13C{1H} NMR (δ, CDCl3, 20 °C): 171.6
(CO), 168.6 (CPh), 148.0 (CPh), 109.1 (t, J ) 14.4 Hz, CPh), 105.0
(CPh), 76.9 (CH), 76.8 (CH), 76.3 (CH), 76.2 (CH), 53.5 (CH3),
53.2 (CH3). 31P{1H} NMR (δ, CDCl3, 20 °C): 144.9.
1
4.06; N, 4.35. H NMR (δ, DMSO, 20 °C): 8.00 (s, 2H, NH),
7.87-7.83 (m, 6H, PPh), 7.50-7.48 (m, 14H, PPh), 6.77 (t, J )

3822 Organometallics, Vol. 25, No. 16, 2006
Benito-Garagorri et al.
7.8 Hz, 1H, Ph4), 6.23 (d, J ) 7.8 Hz, 2H, Ph3,5). 13C{1H} NMR
(δ, DMSO, 20 °C): 156.9 (t, J ) 14.1 Hz, CPh), 135.1 (t, J ) 25.0
Hz, CPPh), 131.8 (t, J ) 7.8 Hz, CPPh), 131.4 (CPPh), 129.2 (CPh),
129.0 (t, J ) 5.2 Hz, CPPh), 103.2 (t, J ) 10.1 Hz, CPh). 31P{1H}
NMR (δ, DMSO, 20 °C): 76.9.
mixture was stirred at room temperature for 3 h. The solvent was
removed under vacuum and the product precipitated with Et2O,
collected on a glass frit, and washed twice with Et2O (10 mL).
Yield: 187 mg (91%). Anal. Calcd for C32H25F3N2OP2Pd: C, 56.61;
H, 3.71; N, 4.13. Found: C, 56.24; H, 3.89; N, 4.35. 1H NMR (δ,
CD2Cl2, 20 °C): 7.81-7.72 (m, 8H, PPh), 7.48-7.43 (m, 12H,
PPh), 6.86 (t, J ) 7.9 Hz, 1H, Ph4), 6.26 (d, J ) 8.0 Hz, 2H,
Ph3,5), 4.67 (s, 2H, NH). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 156.0
(t, J ) 13.8 Hz, CPh), 133.5 (t, J ) 25.0 Hz, CPPh), 131.9 (t,
J ) 8.1 Hz, CPPh), 131.4 (CPPh), 128.7 (t, J ) 5.5 Hz, CPPh), 128.2
(CPh), 103.5 (t, J ) 9.2 Hz, CPh). 31P{1H} NMR (δ, CD2Cl2, 20
°C): 82.1.
Pd(PCP-Pri)(TFA) (8b). This complex has been prepared
analogously to 8a with Pd(TFA)2 (86 mg, 0.26 mmol) and 1b
(88 mg, 0.26 mmol) as the starting materials. Yield: 124 mg
(88%). Anal. Calcd for C20H32F3N2OP2Pd: C, 44.34; H, 5.95; N,
5.17. Found: C, 44.11; H, 5.78; N, 5.23. 1H NMR (δ, CD2Cl2, 20
°C): 6.76 (t, J ) 7.8 Hz, 1H, Ph4), 6.11 (t, J ) 8.0 Hz, 2H, Ph3,5),
3.91 (s, 2H, NH), 2.38-2.28 (m, 4H CH(CH3)2), 1.32-1.20 (m,
24 H, CH(CH3)2). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 157.7
(CPh), 127.3 (CPh), 124.0 (CPh), 102.1 (CPh), 27.4 (t, J ) 12.6 Hz,
CH(CH3)2), 17.2 (CH(CH3)2). 31P{1H} NMR (δ, CD2Cl2, 20 °C):
114.5.
Pd(PCP-Pri)Cl (5b). This complex has been prepared analo-
gously to 4a with Pd(COD)Cl2 (208 mg, 0.73 mmol) and 1b (250
mg, 0.73 mmol) as the starting materials. Yield: 434 mg (96%).
Anal. Calcd for C18H32ClN2P2Pd: C, 45.02; H, 6.72; N, 5.83.
1
Found: C, 45.11; H, 7.00; N, 5.75. H NMR (δ, CD2Cl2, 20 °C):
6.76 (t, J ) 7.7 Hz, 1H, Ph4), 6.14 (t, J ) 7.7 Hz, 2H, Ph3,5), 3.91
(s, 2H, NH), 2.40-2.29 (m, 4H CH(CH3)2), 1.42-1.20 (m, 24H,
CH(CH3)2). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 157.3 (t, J ) 12.1
Hz, CPh), 127.0 (CPh), 124.0 (CPh), 101.9 (t, J ) 7.9 Hz, CPh), 27.3
(t, J ) 12.7 Hz, CH(CH3)2), 18.1 (CH(CH3)2), 17.3 (CH(CH3)2).
31P{1H} NMR (δ, CD2Cl2, 20 °C): 114.3.
Pd(PCPF-Ph)Cl (6a). This complex has been prepared analo-
gously to 5a with Pd(COD)Cl2 (75 mg, 0.27 mmol) and 2a (145
mg, 0.27 mmol) as the starting materials. Yield: 150 mg (81%).
Anal. Calcd for C31H24ClF3N2P2Pd: C, 54.33; H, 3.53; N, 4.09.
1
Found: C, 54.34; H, 3.59; N, 4.15. H NMR (δ, CD2Cl2, 20 °C):
7.89-7.81 (m, 8H, PPh), 7.55-7.49 (m, 12H, PPh), 6.57 (s, 2H,
Ph3,5), 5.12 (s, 2H, NH). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 151.3
(CPh), 139.7 (CPPh), 133.8 (CPh), 131.8 (CPPh), 131.4 (CPPh), 128.9
(CPPh), 100.9 (CPh). 31P{1H} NMR (δ, CD2Cl2, 20 °C): 81.4.
Pd(PCP-BIPOL)(TFA) (8d). A solution of Pd(TFA)2 (124 mg,
0.37 mmol) and 1d (200 mg, 0.37 mmol) in THF (10 mL) was
stirred for 10 min under ice cooling. The solvent was then removed
at reduced presure, and the remaining product was washed twice
with pentane (10 mL) and dried under vacuum. Yield: 210 mg
(75%). Anal. Calcd for C32H21F3N2O6P2Pd: C, 50.92; H, 2.80; N,
Pd(PCPF-BIPOL)Cl (6b). A solution of Pd(COD)Cl2 (71 mg,
0.25 mmol) and 2d (150 mg, 0.25 mmol) in THF (10 mL) was
stirred at room temperature for 16 h. During that time the product
precipitated as a yellow solid. The solvent was removed in a
vacuum, and the residue was washed with Et2O (2 × 10 mL) and
dried under vacuum. Yield: 160 mg (87%). Anal. Calcd for
C31H20ClF3N2O4P2Pd: C, 49.96; H, 2.70; N, 3.76. Found: C, 50.04;
1
3.71. Found: C, 51.04; H, 2.96; N, 3.75. H NMR (δ, CDCl3, 20
°C): 7.53-7.20 (m, 16H, Biph), 6.78 (t, J ) 9.4 Hz, 1H, Ph4),
6.31 (d, J ) 7.7 Hz, 2H, Ph3,5), 5.62 (s, 2H, NH). 13C{1H} NMR
(δ, CDCl3, 20 °C): 148.0 (CBiph), 147.7 (CPh), 147.2 (CPh), 130.2
(CPh), 129.9 (CBiph), 129.6 (CBiph), 126.7 (CBiph), 121.9 (CBiph), 121.7
(CPh). 31P{1H} NMR (δ, CDCl3, 20 °C): 142.8.
1
H, 2.80; N, 3.77. H NMR (δ, DMSO-d6, 20 °C): 7.70-7.27 (m,
16H, Biph), 6.56 (s, 2H, Ph3,5), 5.92(s, 2H, NH). 13C{1H} NMR
(δ, DMSO-d6, 20 °C): 149.8 (CBiph), 149.2 (CPh), 147.7 (CPh), 147.5
(CPh), 141.1 (CPh), 131.1 (CBiph), 130.5 (CBiph), 130.4 (CBiph), 129.1
(CBiph), 129.8 (CBiph), 123.0 (CPh). 31P{1H} NMR (δ, DMSO, 20
°C): 145.5.
Pd(PCPE-Ph)Cl (9a). A suspension of Pd2(dba)3 (172 mg, 0.19
mmol) and 3a (230 mg, 0.38 mmol) in toluene (10 mL) was stirred
overnight at 80 °C. The resulting yellow solution was evaporated
under vaccum and the product precipitated with Et2O, collected on
a glass frit, and washed twice with Et2O. Yield: 245 mg (90%).
Anal. Calcd for C35H33ClN2O2P2Pd: C, 58.59; H, 4.64; N, 3.90.
Pt(PCP-Ph)Br (7a). A mixture of Pt(COD)Br2 (50 mg, 0.11
mmol) and 1a (53 mg, 0.11 mmol) in toluene was heated to 80 °C,
and triethylamine (20 µL, 0.13 mmol) was added. The mixture was
refluxed overnight and then filtered while hot. The solvent was
removed under vacuum, and the pale yellow product was pre-
cipitated with Et2O, collected on a glass frit, and washed twice
with Et2O (10 mL). Yield: 77 mg (93%). Anal. Calcd for
C30H25BrN2P2Pt: C, 48.01; H, 3.36; N, 3.73. Found: C, 48.34; H,
1
Found: C, 58.94; H, 4.77; N, 4.12. H NMR (δ, CD2Cl2, 20 °C):
7.87-7.43 (m, 23H, PPh, Ph3,5 and Phipso), 5.25 (s, 2H, NH), 4.00
(d, J ) 6.7 Hz, 2H, CH2), 2.02 (m, J ) 6.7 Hz, 1H, CH(CH3)2),
0.99 (d, J ) 6.7 Hz, 6H, CH(CH3)2). 13C{1H} NMR (δ, CD2Cl2,
20 °C): 166.1 (CO), 155.7 (t, J ) 13.9 Hz, CPh), 134.8 (CPPh),
131.9 (t, J ) 7.9 Hz, CPPh), 130.3 (CPPh), 130.4 (CPh), 128.8 (t,
J ) 5.7 Hz, CPPh), 104.0 (t, J ) 9.5 Hz, CPh), 70.7 (CH2), 27.9
(CH(CH3)2), 18.9 (CH(CH3)2). 31P{1H} NMR (δ, CD2Cl2, 20 °C):
80.5.
1
3.42; N, 3.15. H NMR (δ, CD2Cl2, 20 °C): 7.93-7.84 (m, 8H,
Ph), 7.50-7.41 (m, 12H, Ph), 6.89 (t, J ) 7.8 Hz, 1H, Ph4), 6.42-
6.33 (q, J ) 8.1 Hz, 2H, Ph3,5), 5.35 (t, J ) 38.8 Hz, 2H, NH).
13C{1H} NMR (δ, CD2Cl2, 20 °C): 153.7 (t, J ) 12.0 Hz, CPh),
133.9 (CPPh), 132.3 (t, J ) 7.6 Hz, CPPh), 131.3 (CPPh), 128.6 (t, J
) 5.7 Hz, CPPh), 127.3 (t, J ) 5.7 Hz, CPh), 103.0 (t, J ) 7.6 Hz,
CPh). 31P{1H} NMR (δ, CD2Cl2, 20 °C): 76.1 (t, J ) 1604.0 Hz).
X-ray Structure Determination. X-ray data for Ni(PCP-Ph)-
Cl‚1/2C6H6 (4a‚1/2C6H6), Ni(PCP-But)Cl (4c), Pd(PCP-Ph)Cl‚
2DMF (5a‚2DMF), Pd(PCPF-Ph)Cl‚CH3CN (6a‚CH3CN),
Pt(PCP-Ph)Br‚(Et3NH)Br‚CH2Cl2 (7a‚[NEt3H]Br‚CH2Cl2), Pd-
(PCP-Pri)(TFA) (8b), and Pd(PCP-BIPOL)(TFA)‚2Et2O (8d‚2Et2O)
were collected on a Bruker Smart CCD area detector diffractometer
using graphite-monochromated Mo KR radiation (λ ) 0.71073 Å)
and 0.3° ω-scan frames covering a hemisphere (4a‚1/2C6H6, 4c)
or complete spheres (5a‚2DMF, 6a‚CH3CN, 7a‚[NEt3H]Br‚
CH2Cl2, 8b, and 8d‚2Et2O) of the reciprocal space. Corrections
for absorption, λ/2 effects, and crystal decay were applied.22 The
structures were solved by direct methods using the program
SHELXS97.23 Structure refinement on F2 was carried out with the
program SHELXL97.23 All non-hydrogen atoms were refined
Pt(PCP-Pri)Br (7b). This complex has been prepared analo-
gously to 5a with Pt(COD)Br2 (50 mg, 0.11 mmol), 1b (38 mg,
0.11 mmol), and triethylamine (20 µL, 0.13 mmol) as the starting
materials. Yield: 61 mg (91%). Anal. Calcd for C18H33BrN2P2Pt:
C, 35.19; H, 5.41; N, 4.56. Found: C, 35.32; H, 5.22; N, 4.62. 1H
NMR (δ, CD2Cl2, 20 °C): 6.77 (t, J ) 7.8 Hz, 1H, Ph4), 6.24-
6.13 (q, J ) 7.6 Hz, 2H, Ph3,5), 4.35 (t, J ) 37.9 Hz, 2H, NH),
2.60-2.48 (m, J ) 7.5 Hz, 4H, CH(CH3)2, 1.27-1.18 (m, 24H,
CH(CH3)2). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 155.2 (t, J ) 10.7
Hz, CPh), 128.5 (CPh), 125.2 (CPh), 101.6 (t, J ) 6.6 Hz, CPh), 27.9
(t, J ) 16.7 Hz, CH(CH3)2), 16.7 (CH(CH3)2). 31P{1H} NMR (δ,
CD2Cl2, 20 °C): 106.6 (t, J ) 1555.6 Hz).
(22) Bruker programs: SMART, version 5.625; SAINT, version 6.36;
SADABS, version 2.10; XPREP, version 6.1; SHELXTL, version 6.1 (Bruker
AXS Inc.: Madison, WI, 2001).
Pd(PCP-Ph)(TFA) (8a). Pd(TFA)2 (100 mg, 0.30 mmol) was
added to a solution of 1a (144 mg, 0.30 mmol) in THF, and the

Ni(II), Pd(II), and Pt(II) PCP Pincer Complexes
Organometallics, Vol. 25, No. 16, 2006 3823
anisotropically. Hydrogen atoms were inserted in idealized positions
and were refined riding with the atoms to which they were bonded.
Salient crystallographic data are given in the Supporting Informa-
tion, Table S1; further details are given in the deposited CIF.
Basque Government (Eusko Jaurlaritza/Gobierno Vasco) for a
doctoral fellowship.
Supporting Information Available: Synthesis and spectro-
scopic data of 4c, 5c-f, 6e, 7c, 8c, and 9e. Complete crystal-
lographic data and technical details in tabular and in CIF format
for 4a‚1/2C6H6, 4c, 5a‚2DMF, 6a‚CH3CN, 7a‚[NEt3H]Br‚CH2Cl2,
8b, and 8d‚2Et2O. This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. Financial support by the “Fonds zur
Fo¨rderung der wissenschaftlichen Forschung” is gratefully
acknowledged (Project No. P16600-N11). D.B.-G. thanks the
(23) Sheldrick, G. M. SHELX97: Program System for Crystal Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
OM060289E