Achiral and chiral transition metal complexes with modularly designed tridentate PNP pincer-type ligands based on N-heterocyclic diamines

Article abstract of DOI:10.1021/om0600644

The synthesis and characterization of a series of molybdenum, iron, ruthenium, nickel, palladium, and platinum complexes containing new achiral and chiral PNP pincer-type ligands based on the N-heterocyclic diamines 2,6-diaminopyridine, N,N′-di-10-undecenyl-2,6-diaminopyridine, N,N′-dihexyl-2,6-diaminopyridine, and 2,6-diamino-4-phenyl-1,3,5-triazine are reported. The new PNP ligands are prepared conveniently in high yield by treatment of the respective N-heterocyclic diamines with 2 equiv of a variety of achiral and chiral R₂PCl compounds in the presence of base. Molybdenum PNP complexes of the type [Mo(PNP)(CO)₃PNP] are obtained by treatment of [Mo(CO)₃(CH₃CN)₃] with 1 equiv of the respective PNP ligand. They were found to react with I₂ to give novel seven-coordinate pincer complexes of the types [Mo(PNP)(CO) ₃I]⁺ and [Mo(PNP)(CO)₂(CH₃CN)I] ⁺ depending of whether the reaction is carried out in CH ₂Cl₂ or CH₃CN. With [Fe(H₂O) ₆](BF₄)₂ and 1 equiv of PNP ligand in acetonitrile dicationic complexes of the type [Fe(PNP)(CH₃CN) ₃](BF₄)₂ are obtained. The cis and trans dichloride complexes [Ru(PNP)(PPh₃)Cl₂] are prepared by a ligand exchange reaction of [RuCl₂(PPh₃)₃] with a stoichiometric amount of the respective PNP ligand. Cationic PNP complexes of Ni(II), [Ni(PNP)Br]Br, were synthesized by the reaction of [NiBr₂(DME)] with 1 equiv of PNP ligand. In similar fashion, treatment of [M(COD)X₂] (M = Pd, Pt; X = C1, Br) with 1 equiv of PNP ligand yields the cationic square-planar complexes [M(PNP)X]X. If the reaction is carried out in the presence of the halide scavenger KCF₃SO ₃, complexes of the type [M(PNP)X]CF₃SO₃ are obtained, which are better soluble in nonpolar solvents than the analogous halide compounds. X-ray structures of representative Mo, Fe, Ru, Ni, and Pd PNP 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/om0600644

1900
Organometallics 2006, 25, 1900-1913
Achiral and Chiral Transition Metal Complexes with Modularly
Designed Tridentate PNP Pincer-Type Ligands Based on
N-Heterocyclic Diamines
David Benito-Garagorri,† Eva Becker,† Julia Wiedermann,† Wolfgang Lackner,†
Martin Pollak,† Kurt Mereiter,‡ Joanna Kisala,§ 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, and Faculty of Chemistry,
Rzeszo´w UniVersity of Technology, 6 Powstan˜co´w Warszawy AVenue, 35-959 Rzeszo´w, Poland
ReceiVed January 22, 2006
The synthesis and characterization of a series of molybdenum, iron, ruthenium, nickel, palladium, and
platinum complexes containing new achiral and chiral PNP pincer-type ligands based on the N-heterocyclic
diamines 2,6-diaminopyridine, N,N′-di-10-undecenyl-2,6-diaminopyridine, N,N′-dihexyl-2,6-diamino-
pyridine, and 2,6-diamino-4-phenyl-1,3,5-triazine are reported. The new PNP ligands are prepared
conveniently in high yield by treatment of the respective N-heterocyclic diamines with 2 equiv of a
variety of achiral and chiral R2PCl compounds in the presence of base. Molybdenum PNP complexes of
the type [Mo(PNP)(CO)3PNP] are obtained by treatment of [Mo(CO)3(CH3CN)3] with 1 equiv of the
respective PNP ligand. They were found to react with I2 to give novel seven-coordinate pincer complexes
of the types [Mo(PNP)(CO)3I]+ and [Mo(PNP)(CO)2(CH3CN)I]+ depending of whether the reaction is
carried out in CH2Cl2 or CH3CN. With [Fe(H2O)6](BF4)2 and 1 equiv of PNP ligand in acetonitrile
dicationic complexes of the type [Fe(PNP)(CH3CN)3](BF4)2 are obtained. The cis and trans dichloride
complexes [Ru(PNP)(PPh3)Cl2] are prepared by a ligand exchange reaction of [RuCl2(PPh3)3] with a
stoichiometric amount of the respective PNP ligand. Cationic PNP complexes of Ni(II), [Ni(PNP)Br]Br,
were synthesized by the reaction of [NiBr2(DME)] with 1 equiv of PNP ligand. In similar fashion, treatment
of [M(COD)X2] (M ) Pd, Pt; X ) Cl, Br) with 1 equiv of PNP ligand yields the cationic square-planar
complexes [M(PNP)X]X. If the reaction is carried out in the presence of the halide scavenger KCF3SO3,
complexes of the type [M(PNP)X]CF3SO3 are obtained, which are better soluble in nonpolar solvents
than the analogous halide compounds. X-ray structures of representative Mo, Fe, Ru, Ni, and Pd PNP
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.
electronic, and stereochemical properties can be easily varied,
we describe here the synthesis of a series of modularly designed
PNP ligands based on N-heterocyclic diamines and R2PCl that
contain both bulky and electron-rich dialkyl phosphines as well
as various P-O bond-containing achiral and chiral phosphine
units.11,12 This methodology was originally developed for the
Introduction
Tridentate PNP ligands in which the central pyridine-based
ring donor contains -CH2PR2 substituents in the two ortho
positions are widely utilized ligands in transition metal chemistry
(e.g., Fe, Ru, Rh, Ir, Pd, Pt).1-10 In this family of ligands steric,
electronic, and stereochemical parameters can be manipulated
by modifications of the benzylic positions and/or the phosphino
R groups so as to control the reactivity at the metal center.
Stereochemical parameters, however, are comparatively difficult
to modify and often require tedious multistep syntheses and
expensive starting materials.3,5a As part of our effort to create
novel tridentate PNP pincer-type ligands in which the steric,
(3) Jiang, Q.; Van Plew, D.; Murtuza, S.; Zhang, X. Tetrahedron Lett.
1996, 37, 797.
(4) (a) Andreocci, M. V.; Mattogno, G.; Zanoni, R.; Giannoccaro, P.;
Vasapollo, G. Inorg. Chim. Acta 1982, 63, 225. (b) Sacco, A.; Vasapollo,
G.; Nobile, C.; Piergiovanni, A.; Pellinghelli, M. A.; Lanfranchi, M. J.
Organomet. Chem. 1988, 356, 397. (c) Abbenhuis, R. A. T. M.; del Rio,
I.; Bergshoef, M. M.; Boersma, J.; Veldman, N.; Spek, A. L.; van Koten,
G. Inorg. Chem. 1998, 37, 1749.
(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,
J. A. Tetrahedron Lett. 1996, 37, 4937. (d) Barloy, L.; Ku, S. Y.; Osborn,
J. A.; De Cian, A.; Fischer, J. Polyhedron 1997, 16, 291.
(6) (a) Zhang, J.; Leitus, G.; Ben-David, Y.; Milstein, D. J. Am. Chem.
Soc. 2005, 127, 10840. (b) Zhang, J.; Gandelman, M.; Shimon, L. J. W.;
Rozenberg, H.; Milstein, D. Organometallics 2004, 23, 4026. (c) Hermann,
D.; Gandelman, M.; Rozenberg, H.; Shimon, L. J. W.; Milstein, D.
Organometallics 2002, 21, 812.
(7) Gibson, D. H.; Pariya, C.; Mashuta, M. S. Organometallics 2004,
23, 2510.
(8) Katayama, H.; Wada, C.; Taniguchi, K.; Ozawa, F. Organometallics
2002, 21, 3285.
* To whom correspondence should be addressed. E-mail: kkirch@
mail.zserv.tuwien.ac.at.
† Institute of Applied Synthetic Chemistry, Vienna University of
Technology.
‡ Institute of Chemical Technologies and Analytics, Vienna University
of Technology.
§ Rzeszo´w University of Technology.
(1) Dahlhoff, W. V.; Nelson, S. M. J. Chem. Soc. A 1971, 2184.
(2) (a) Vasapollo, G.; Giannoccaro, P.; Nobile, C. F.; Sacco, A. Inorg.
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.
(9) Jia, G.; Lee, H. M.; Williams, I. D.; Lau, C. P.; Chen, Y.
Organometallics 1997, 16, 3941.
10.1021/om0600644 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 03/15/2006

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1901
Scheme 1
of 1 equiv of Ph2PCl to N,N′-di-10-undecenyl-2,6-diaminopy-
ridine and N,N′-dihexyl-2,6-diaminopyridine in the presence of
n-BuLi afforded the monophosphinated compounds 2a′ and 2b′,
respectively. Subsequent addition of another equivalent of
Ph2PCl and n-BuLi afforded then the desired PNP ligands 2a
and 2b in high isolated yields (Scheme 2). Finally, the first PNP
ligand with a 2,6-diamino-1,3,5-triazine backbone could be
obtained by reacting 2 equiv of Ph2PCl with 2,6-diamino-4-
phenyl-1,3,5-triazine, affording PNPT-Ph (3) in 95% yield
(Scheme 3).
All PNP ligands are air stable in the solid state and in oxygen-
1
free solutions. They have been characterized by H, 13C{1H},
and 31P{1H} NMR spectroscopy. Most diagnostic is the
31P{1H} NMR spectrum, exhibiting one singlet in the range 28
to 143 ppm. In the 1H NMR spectrum the NH protons of 1a-h
and 3 give rise to a slightly broadened doublet in the range
4.30 to 6.40 ppm. All other resonances are unremarkable and
are not discussed here.
Molybdenum PNP Pincer Complexes. Molybdenum com-
plexes featuring PNP pincer ligands are comparatively rare. A
few years ago Haupt and co-workers reported the synthesis of
[M(PNP-Ph)(CO3)] (M ) Cr, Mo, W),13 while recently Walton
and co-workers described the synthesis of the dinuclear mo-
lybdenum complex [Mo(PNP)Mo(HPCy2)Cl3] (PNP ) 2,6-bis-
(dicyclohexylphosphinomethyl)pyridine).16 We prepared mo-
lybdenum tricarbonyl complexes with our new PNP ligands by
reacting [Mo(CO)3(CH3CN)3], prepared in situ by refluxing a
solution of [Mo(CO)6] in CH3CN for 4 h, with the PNP ligands
1a-c, 2a, and 3 to afford, upon workup, the complexes
[Mo(PNP-Pri)(CO)3] (4a), [Mo(PNP-But)(CO)3] (4b), [Mo(PNP-
TARPr)(CO)3] (4c), [Mo(PNP-PhUndec)(CO)3] (5), and [Mo-
(PNPT-Ph)(CO)3] (6) in 74 to 90% isolated yields (Scheme 4).
With the exception of 4c, all compounds are air-stable both in
the solid state and in solution. 4c slowly rearranges cleanly in
solution to an, as yet, unidentified new compound exhibiting a
31P{1H} NMR resonance at 3.5 ppm. With the ligands 1e and
1f the formation of [Mo(PNP)(CO)3] complexes was not
observed, but the same rearrangement product as in the case of
4c was detected by 31P{1H} NMR spectroscopy, giving rise to
signals at 14.2 and 5.3 ppm, respectively. Complexes 4-6 were
synthesis of N,N′-bis(diphenylphosphino)-2,6-diaminopyridine
(PNP-Ph).13 Furthermore, we report the application of these
ligands for the synthesis of a series of Mo, Fe, Ru, Ni, Pd, and
Pt complexes. Some reactions of these new PNP compounds
will be presented including preliminary results of the use of
palladium PNP complexes in the catalytic cross-coupling of
various aryl bromides with phenyl boronic acid (Suzuki-
Miyaura coupling).
Results and Discussion
Ligand Synthesis. Similarly to the known ligand N,N′-bis-
(diphenylphosphino)-2,6-diaminopyridine (PNP-Ph), 1a,13 the
new PNP ligands 1b-h are prepared conveniently in 64-95%
yield by treatment of 2,6-diaminopyridine with 2 equiv of the
respective R2PCl compound in the presence of base, viz., NEt3
and/or n-BuLi (Scheme 1). Surprisingly, this methodology failed
in the case of N,N′-dialkylated diaminopyridines. In fact, when
the reaction of N,N′-dihexyl-2,6-diaminopyridine and N,N′-di-
10-undecenyl-2,6-diaminopyridine and Ph2PCl was monitored
by 31P{1H} NMR spectroscopy, no evidence for the formation
of PNP-PhHex (2a) and PNP-PhUndec (2b) was found; that is,
P-N coupling did not occur, but instead several phosphorus-
containing species were formed including tetraphenyldiphos-
phine (-16.1 ppm)14 and tetraphenyldiphosphine monoxide
(double-doublet at 37 and -24 ppm with JPP ) 229 Hz) as a
result of P-P coupling.15 The synthesis of these ligands could
be achieved, however, via a two-step procedure. First, addition
1
fully characterized by a combination of H, 13C{1H}, and 31P-
{1H} NMR spectroscopy, IR spectroscopy, and elemental
analysis.
Characteristic features of 4, 5, and 6 comprise, in the
13C{1H} NMR spectrum, low-field triplet resonances in the
range 223-231 ppm and 206-216 ppm assignable to the car-
bonyl carbon atoms trans and cis to the pyridine nitrogen,
respectively. The 31P{1H} NMR spectra exhibit singlet reso-
nances at 131.9, 148.8, 207.7, 129.3, and 103.3 ppm. The IR
spectra show three strong to medium absorption bands in the
range 1988 to 1811 cm-1 as expected for a meridional arrange-
ment of the three carbonyl ligands.
In addition to the spectroscopic characterization, the solid-
state structures of 4a and 4b were determined by single-crystal
X-ray diffraction. ORTEP diagrams are depicted in Figures 1
and 2 with selected bond distances given in the captions. The
coordination geometry around the molybdenum center corre-
sponds to a distorted octahedron. The P(1)-Mo-P(2) angles
in the complexes [Mo(PNP-Ph)(CO)3],13 4a, and 4b are hardly
affected by the size of the substituents of the phosphorus atoms,
being 155.0(2)°, 155.62(1)°, and 151.73(1)°, respectively. The
carbonyl-Mo-carbonyl angles of the CO ligands trans to one
(10) Mu¨ller, G.; Klinga, M.; Leskela¨, M.; Rieger, B. Z. Anorg. Allg.
Chem. 2002, 628, 2839.
(11) Ansell, J.; Wills, M. Chem. Soc. ReV. 2002, 31, 259.
(12) For related chiral PCP ligands and complexes see: (a) Gorla, F.;
Togni, A.; Venanzi, L. M.; Albinati, A.; Lianza, F. Organometallics 1994,
13, 1607. (b) Longmire, J. M.; Zhang, X.; Shang, M. Organometallics 1998,
17, 4374. (c) Longmire, J. M.; Zhang, X. Tetrahedron Lett. 1997, 38, 1725.
(d) Williams, B. S.; Dani, P.; Lutz, M.; Spek, A. L.; van Koten, G. HelV.
Chim. Acta 2001, 84, 3519. (e) Albrecht, M.; Kocks, B. M.; Spek, A. L.;
van Koten, G. J. Organomet. Chem. 2001, 624, 271.
(13) (a) Schirmer, W.; Flo¨rke, U.; Haupt, H.-J. Z. Anorg. Allg. Chem.
1987, 545, 83. (b) Schirmer, W.; Flo¨rke, U.; Haupt, H.-J. Z. Anorg. Allg.
Chem. 1989, 574, 239.
(14) Aime, S.; Harris, R. K.; McVicker, E. M.; Fild, M. J. Chem. Soc.,
Dalton Trans. 1976, 2144.
(15) Hunter, D.; Michie, J. K.; Miller, J. A.; Stewart, W. Phosphorus
Sulfur 1981, 10, 267.
(16) (a) Lang, H.-F.; Fanwick, P. E.; Walton, R. A. Inorg. Chim. Acta
2002, 392, 1.

1902 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
Scheme 2
coordinate complexes [Mo(PNP-Pri)(CO)3I]I (7a) and [Mo(PNP-
PhUndec)(CO)3I]I (7c), respectively (Scheme 5). Noteworthy,
treatment of 4a with 2 equiv of I2 results in the formation of
[Mo(PNP-Pri)(CO)3I]I3 (7b), which differs from 7a only by the
nature of the counterion, i.e., triiodide versus iodide. On the
other hand, if the reaction of 4a and I2 is carried out in CH3CN
instead of CH2Cl2, the mono-acetonitrile complex [Mo(PNP-
Pri)(CO)2(CH3CN)I]I (8) is obtained. The identity of compounds
7 and 8 was established by 1H and 31P{1H} NMR spectroscopy,
IR spectroscopy, and elemental analysis. 7c was also character-
ized by 13C{1H} NMR spectroscopy. In addition, the solid-state
structures of 7b and 8 have been determined by X-ray
crystallography. According to our knowledge, 7 and 8 are the
first seven-coordinate pincer molybdenum complexes.
Scheme 3
another, on the other hand, viz., C(1)-Mo-C(2), C(19)-Mo-
C(20), and C(23)-Mo-C(24), vary strongly with the bulkiness
of the PR2 moiety (PPh2 < PPri2 < PBut2) and decrease from
171.1(8)° in [Mo(PNP-Ph)(CO)3] to 166.03(5)° in 4a, and finally
to 156.53(4)° in 4b.
As part of our interest in the chemistry of molybdenum PNP
complexes, we have begun to investigate the reactivity of
complexes 4 and 5 toward iodine. In fact, complexes 4a and 5
react readily with 1 equiv of I2 in CH2Cl2 to afford the seven-
Seven-coordinate complexes are notorious for their fluxional
behavior in solution.17,18 None of the idealized geometries,
capped prism, capped octahedron, and pentagonal bipyramid,
nor any of less symmetrical arrangements are characterized by
a markedly lower total energy.19 Hence, interconversions
between these various structures are quite facile. Thus, as
expected, the 31P{1H} NMR spectra of 7a, 7c, and 8 exhibit
only one resonance at 114.0, 127.8, and 113.8 ppm at room
temperature and even at -90 °C in CD2Cl2 as the solvent. The
13C{1H} NMR spectrum of 7c shows two low-field triplet
carbonyl resonances (2:1 ratio) centered at 255.0 and 227.8 ppm.
Complexes 7 and 8 both display three νCO bands in the solid-
state IR spectra. In addition, the nitrile ligand in 8 gives rise to
two nitrile resonances at 2299 and 2269 cm-1. Detailed
investigations concerning the dynamics of this type of complexes
are in progress and will be reported in due course.
Molecular views of 7b and 8 are depicted in Figures3 and 5,
with selected bond distances and angles reported in the captions.
The coordination geometry around the molybdenum center may
be viewed as a distorted capped trigonal prism. This is
emphasized in Figure 4, showing a view of the inner coordina-
tion sphere of 7b and 8 with N(1) capping the quadrilateral
face. The angles used to describe an ideal capped trigonal prism
in which all M-L distances are equal are shown in Chart 1. Lc
Figure 1. Structural view of Mo(PNP-Pri)(CO)3‚CH3CN (4a‚CH3-
CN) showing 30% thermal ellipsoids (C-bonded H atoms and CH3-
CN omitted for clarity). Selected bond lengths (Å) and bond angles
(deg): Mo-C(18) 1.948(1), Mo-C(19) 2.001(2), Mo-C(20) 2.024-
(1), Mo-N(1) 2.251(1), Mo-P(1) 2.4206(3), Mo-P(2) 2.3986-
(3); P(1)-Mo-P(2) 155.62(1), C(19)-Mo-C(20) 166.03(5).
Scheme 4

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1903
Figure 3. Structural view of [Mo(PNP-Pri)(CO)3I]I3 (7b) showing
-
40% thermal ellipsoids (C-bonded H atoms and I3 omitted for
clarity). Selected bond lengths (Å) and bond angles (deg): Mo-
C(18) 2.019(2), Mo-C(19) 1.984(2), Mo-C(20) 2.012(2), Mo-
N(1) 2.230(2), Mo-P(1) 2.5211(6), Mo-P(2) 2.5163(6), Mo-I(1)
2.8556(2); P(1)-Mo-P(2) 153.32(2), N(1)-Mo-P(1) 77.33(5),
N(1)-Mo-P(2) 76.87(5), N(1)-Mo-C(18) 82.5(1), N(1)-Mo-
C(19) 137.4(1), N(1)-Mo-C(20) 151.3(1), N(1)-Mo-I(1) 83.32-
(4).
Figure 2. Structural view of Mo(PNP-But)(CO)3‚CH3CN (4b‚CH3-
CN) showing 40% thermal ellipsoids (C-bonded H atoms and CH3-
CN omitted for clarity). Selected bond lengths (Å) and bond angles
(deg): Mo-C(22) 1.924(1), Mo-C(23) 2.011(1), Mo-C(24) 2.008-
(1), Mo-N(1) 2.284(1), Mo-P(1) 2.4638(3), Mo-P(2) 2.4767-
(3); P(1)-Mo-P(2) 151.73(1), C(23)-Mo-C(24) 156.53(4).
Scheme 5
Figure 4. Structural views of the inner coordination sphere of [Mo-
(PNP-Pri)(CO)3I]+ (7b) (left) and [Mo(PNP-Pri)(CO)2(CH3CN)I]+
(8) (right) emphasizing the capped trigonal prism description with
N(1) capping the quadrilateral face.
interesting to note that small amounts of water apparently do
not cause hydrolysis, resulting in cleavage of P-N and/or P-O
bonds of the PNP ligands. All these complexes have been
1
characterized by a combination of elemental analysis and H,
(N1) is the capping ligand, Lf are ligands in the capped
rectangular face, and Le are the ligands in the unique edge of
the capped prism. In the ideal case Θ1 and Θ2 are 82° and 148°,
respectively. In the case at hand, Θ1 and Θ2 are taken as average
values of the four Lc-Mo-Lf and the two Lc-Mo-Le angles.
For 7b and 8 these angles are 80.1° and 144.4° and 79.1° and
145.6°, respectively.
Iron PNP Pincer Complexes. With the exception of the
bulky PNP-But (1c), the reaction of [Fe(H2O)6](BF4)2 with 1
equiv of 1a-h, 2a, 2b, and 3, respectively, in acetonitrile at
room temperature for 2 h affords on workup the air-stable
diamagnetic trisacetonitrile complexes [Fe(PNP)(CH3CN)3]-
(BF4)2 (9a-f), [Fe(PNP-PhUndec)(CH3CN)3](BF4)2 (10a), [Fe-
(PNP-PhHex)(CH3CN)3](BF4)2 (10b), and [Fe(PNPT-Ph)(CH3-
CN)3](BF4)2 (11) in high isolated yields (Scheme 6). In the case
of PNP-But only intractable materials were obtained. It is
13C{1H}, and 31P{1H} NMR spectroscopy. In addition, the solid-
state structures of [Fe(PNP-Ph)(CH3CN)3](BF4)2 (9a) [Fe(PNP-
Pri)(CH3CN)3](BF4)2 (9b), [Fe(PNP-BIPOL)(CH3CN)3](BF4)2
(9d), and the chiral [Fe(PNP-TARMe)(CH3CN)3](BF4)2 (9f) were
determined by single-crystal X-ray diffraction. These complexes
all exhibit a singlet resonance in the 31P{1H} NMR spectrum
in the range of about 98 to 194 ppm. In the 1H NMR spectrum
the NH protons give rise to a slightly broadened singlet in the
range 7.30 to 8.89 ppm. All other resonances are unremarkable
and are not discussed here.
ORTEP diagrams of 9d, 9f, and 11 are depicted in Figures
6, 7, and 8 with selected bond distances and angles reported in
the captions. ORTEP diagrams of 9a and 9b are provided in
the Supporting Information. All five complexes adopt a distorted
octahedral geometry around the metal center. The PNP ligands
are coordinated to the iron center in a tridentate meridional
mode, with P-Fe-P angles around 166°. The mean bond
lengths around Fe of the these compounds are Fe-P 2.218 Å,
Fe-Npy 1.974 Å, Fe-Ntrans 1.932, and Fe-Ncis 1.917 Å. The
Fe-P bond length is systematically longer for aryl-bearing P
(mean value 2.245 Å) than for the P-O-bearing phosphines
(9d and 9f, mean value 2.191 Å). The Fe-N bonds of the nitriles
(17) Curtis, M. D.; Shiu, K.-B. Inorg. Chem. 1985, 24, 1213.
(18) Baker, P. K.; Al-Jahdali, M.; Meehan, M. M. J. Organomet. Chem.
2002, 648, 99. (b) Baker, P. K.; Drew, M. G. B.; Moore, D. S. J. Organomet.
Chem. 2002, 663, 45.
(19) (a) Hoffmann, R.; Beier, B. F.; Muetterties, E. L.; Rossi, A. R. Inorg.
Chem. 1977, 16, 511. (b) Thompson, H. B.; Bartell, L. S. Inorg. Chem.
1968, 7, 488.

1904 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
Figure 6. Structural view of [Fe(PNP-BIPOL)(CH3CN)3](BF4)2‚
solv (9d‚solv) showing 30% thermal ellipsoids (C-bonded H atoms
and second independent complex omitted for clarity). Selected bond
lengths (Å) and bond angles (deg): Fe-P(1) 2.1895(5), Fe-P(2)
2.1881(5), Fe-N(1) 1.975(2), Fe-N(4) 1.931(2), Fe-N(5) 1.917-
(2), Fe-N(6) 1.913(2), P(1)-N(2) 1.658(2), P(2)-N(3) 1.653(2),
N(2)-C(1) 1.387(2), N(3)-C(5) 1.389(2); P(1)-Fe-P(2) 165.62-
(2).
Figure 5. Structural view of [Mo(PNP-Pri)(CO)2(CH3CN)I]I (8)
showing 40% thermal ellipsoids (C-bonded H atoms and I- omitted
for clarity). Selected bond lengths (Å) and bond angles (deg): Mo-
C(18) 1.985(7), Mo-C(19) 1.952(7), Mo-N(1) 2.231(5), Mo-
N(4) 2.248(6), Mo-P(1) 2.520(2), Mo-P(2) 2.466(2), Mo-I(1)
2.8649(7); P(1)-Mo-P(2) 150.42(7), N(1)-Mo-C(18) 140.1(2),
N(1)-Mo-C(19) 82.8(2), N(1)-Mo-N(4) 82.1(2), N(1)-Mo-
P(1) 75.4(1), N(1)-Mo-P(2) 76.1(1), N(1)-Mo-I(1) 151.0(1).
Scheme 7
Chart 1
evolution of gas (H2), affording the deprotonated monocationic
complex [Fe(PNP-BIPOL)(CH3CN)3]BF4 (12) as shown in
Scheme 7. Noteworthy, complex 12 was also obtained when
9d was chromatographed on basic alumina. Thus, in this case
the reduction of the metal center is apparently hampered by
the acidic NH protons of the PNP ligand. The identity of 12
was unequivocally established by X-ray crystallography. A
structural view of 12 is shown in Figure 9, with selected bond
distances and angles reported in the caption. The bond lengths
involving the deprotonated nitrogen N(2) are significantly
trans to the pyridine nitrogen of the PNP ligand are typically
longer than the ones cis to the PNP moiety. The aminophosphine
nitrogen atoms are typically active hydrogen bond donors, as
shown for example in Figure 6. Anions as well as suitable
solvent molecules (CH3CN, Et2O, H2O) are comparatively well
anchored by this hydrogen bonding.
Attempts to obtain zerovalent iron complexes of the type [Fe-
(PNP)(CH3CN)2] by reacting [Fe(PNP-BIPOL)(CH3CN)3](BF4)2
(9d) with NaHg (3%) failed. In fact, treatment of 9d with an
excess of NaHg in acetonitrile resulted in the immediate
1
shorter than for their hydrogen-bearing counterparts. The H,
13C{1H}, and 31P{1H} NMR spectra are not very informative,
exhibiting only broad and featureless or averaged resonances
even at -70 °C in THF-d8. For instance, in the 31P{1H} NMR
Scheme 6

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1905
Figure 7. Structural view of [Fe(PNP-TARMe)(CH3CN)3](BF4)2
(9f) showing 30% thermal ellipsoids (C-bonded H atoms and BF4
omitted for clarity). Selected bond lengths (Å) and bond angles
(deg): Fe-P(1) 2.1916(4), Fe-P(2) 2.2134(4), Fe-N(1) 1.976-
(2), Fe-N(4) 1.930(2), Fe-N(5) 1.919(2), Fe-N(6) 1.930(2),
P(1)-N(2) 1.661(2), P(2)-N(3) 1.673(2), N(2)-C(1) 1.387(2),
N(3)-C(5) 1.382(2); P(1)-Fe-P(2) 166.74(2).
Figure 9. Structural view of [Fe(PNP-BIPOL)(CH3CN)3]BF4‚CH3-
CN (12‚CH3CN) showing 30% thermal ellipsoids (C-bonded H
-
-
atoms and BF4 omitted for clarity). Selected bond lengths (Å)
and bond angles (deg): Fe-P(1) 2.2114(4), Fe-P(2) 2.1736(4),
Fe-N(1) 1.982(1), Fe-N(4) 1.931(1), Fe-N(5) 1.910(1), Fe-N(6)
1.927(1), P(1)-N(2) 1.614(1), P(2)-N(3) 1.656(1), N(2)-C(1)
1.362(2), N(3)-C(5) 1.392(2); P(1)-Fe-P(2) 163.30(2).
Scheme 8
Figure 8. Structural view of [Fe(PNPT-Ph)(CH3CN)3](BF4)2‚3ClCH2-
CH2Cl‚H2O (11‚3ClCH2CH2Cl‚H2O) showing 40% thermal el-
-
lipsoids (C-bonded H atoms, BF4 and solvent molecules omitted
for clarity). Selected bond lengths (Å) and bond angles (deg): Fe-
P(1) 2.2430(4), Fe-P(2) 2.2409(4), Fe-N(1) 1.957(1), Fe-N(6)
1.942(1), Fe-N(7) 1.914(1), Fe-N(8) 1.915(1), P(1)-N(4) 1.707-
(1), P(2)-N(5) 1.702(1), N(4)-C(1) 1.355(2), N(5)-C(3) 1.353-
(2); P(1)-Fe-P(2) 165.44(2).
Ruthenium PNP Pincer Complexes. The dichloride com-
plexes Ru(PNP)(PPh3)Cl2 (16) are conveniently prepared by a
ligand exchange reaction of RuCl2(PPh3)3 with a stoichiometric
amount of the respective PNP ligands 1a-f in CH2Cl2 (Scheme
9). Only in the case of PNP-But (1c) were all attempts to prepare
[Ru(PNP-But)(PPh3)Cl2 unsuccessful. Complexes 16 are yellow
to brown solids, stable in both the solid state and in oxygen-
free solutions. The retention of one PPh3 ligand in 16 is clearly
shown by elemental analysis and NMR spectroscopy. Due to
the rigidity of the -NHPR2 substituents, the octahedral com-
plexes form only two mer-stereoisomers with either a trans-
dichloro or a cis-dichloro arrangement. Mixtures of both of them
were not observed. The 1H, 13C{1H}, and 31P{1H} NMR spectra
of 16 show a single resonance pattern at all temperatures for
all nuclei, indicating the presence of a single stereoisomer in
solution. Moreover, the 31P{1H} NMR shows one triplet
resonance for PPh3 centered at 38.2 (JPP ) 27.7 Hz) and 38.5
ppm (JPP ) 24.7 Hz) for 16a and 16b, respectively. In the case
of the 16c-f the PPh3 resonance is slightly downfield shifted,
spectrum a singlet at 194.38 ppm is observed (cf. 186.67 ppm
for 9d). This may be attributed to a fast proton exchange process
between the two N-sites. The deprotonation of [Fe(PNP-
BIPOL)(CH3CN)3](BF4)2 (9d) is reversible, and addition of 1
equiv of HBF4‚OEt2 to a solution of 12 in CD3CN cleanly yields
1
9d as monitored by H and 31P{1H} NMR spectroscopy.
The nitrile ligands in complexes 9, 10, and 11 are substitu-
tionally labile and are readily replaced by other nitrogen donor
ligands. The substitution chemistry of [Fe(PNP)(CH3CN)3]2+
has been exemplarily investigated with 9a as model complex.
Treatment of 9a with bipyridine, terpyridine, and PNP-Ph (1a)
yields the formation of complexes 13-15, respectively, in high
isolated yields (Scheme 8). Alternatively, 15 can be obtained
directly by reacting [Fe(H2O)6](BF4)2 with 2 equiv of 1a in THF
as the solvent. Structural views of 13 and 14 are given in Figures
10 and 11 (a structural view of 15 is given in the Supporting
Information). Selected bond distances and angles are reported
in the captions.

1906 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
Figure 10. Structural view of [Fe(PNP-Ph)(bipy)(CH3CN)]BF4‚
solv (13‚solv) showing 20% thermal ellipsoids (C-bonded H atoms
and BF4- omitted for clarity). Selected bond lengths (Å) and bond
angles (deg): Fe-P(1) 2.2323(8), Fe-P(2) 2.2274(8), Fe-N(1)
1.978(2), Fe-N(4) 1.958(2), Fe-N(5) 1.960(2), Fe-N(6) 1.908-
(2); P(1)-Fe-P(2) 167.60(3).
Figure 11. Structural view of [Fe(PNP-Ph)(terpy)]BF4‚solv (14‚
solv) showing 30% thermal ellipsoids (H atoms and BF4- omitted
for clarity). Selected bond lengths (Å) and bond angles (deg): Fe-
P(1) 2.2361(9), Fe-P(2) 2.2401(9), Fe-N(1) 1.989(2), Fe-N(4)
1.878(3), Fe-N(5) 1.968(3), Fe-N(6) 1.967(3), P(1)-Fe-P(2)
165.97(4).
giving rise to triplets or doublets of doublets centered at 49.0,
45.3, 43.3, and 43.8 ppm, respectively. The JPP coupling
constants are significantly larger in the latter case, being in the
range 46.2 to 47.8 Hz. The chemical shifts for PPh3 are typical
for being coordinated trans to neutral or anionic donor ligands.
Accordingly, it is difficult to distinguish whether PPh3 lies cis
or trans to the pyridine nitrogen. It has to be noted that in
analogous ruthenium PNP and also NNN pincer complexes both
arrangements have been observed. For instance, in [RuCl2(PNP)-
(PPh3)] (PNP ) 2,6-bis[(diphenylphosphino)methyl]pyridine),5d
[RuCl2(terpy)(PPh3)],20 and [RuCl2(NNN)(PPh3)] (NNN ) 2,6-
bis[(dimethylamino)methyl]pyridine)4c the triphenylphosphine
ligand coordinates trans to the pyridine nitrogen, the two
chlorides lying mutually trans, while in [RuCl2(pybox)(PPh3)]
(pybox ) 2,6-bis(oxazolinyl)pyridine) PPh3 is coordinated cis
to the pyridine nitrogen and the chloride ligands consequently
adopt a cis configuration.21
With the compounds at hand, the ligand arrangement around
the metal center of the [Ru(PNP)(PPh3)Cl2] complexes could
not be assigned unequivocally since all attempts to crystallize
a series of complexes 16 were as yet unsuccessful. Only the
structure of 16d could be determined by X-ray crystallography.
A structural view of 16d is depicted in Figure 12, with selected
bond distances and angles given in the caption. The geometry
around ruthenium can be described as a distorted octahedron
Figure 12. Structural view of cis-Ru(PNP-BIPOL)(PPh3)Cl2‚2CH2-
Cl2 (16d‚2CH2Cl2) showing 30% thermal ellipsoids (C-bonded H
atoms and CH2Cl2 omitted for clarity). Selected bond lengths (Å)
and bond angles (deg): Ru-P(1) 2.257(3), Ru-P(2) 2.272(3), Ru-
N(1) 2.094(7), Ru-P(3) 2.293(2), Ru-Cl(1) 2.431(3), Ru-Cl(2)
2.463(3); P(1)-Ru-P(2) 161.3(1), N(1)-Ru-Cl(1) 170.0(2),
N(1)-Ru-Cl(2) 85.8(2), Cl(1)-Ru-Cl(2) 86.9(1).
with a meridional PNP ligand, a PPh3 ligand cis to the pyridine
nitrogen atom, and surprisingly two mutually cis Cl atoms. The
Ru-P(1), Ru-P(2), and Ru-P(3) distances are 2.257(3), 2.272-
Scheme 9

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1907
Scheme 10
(3), and 2.293(2) Å and are significantly shorter than those in
trans-[RuCl2(PNP)(PPh3)] (PNP ) 2,6-bis[(diphenylphosphino)-
methyl]pyridine) (2.3862(7), 2.3641(7), and 2.3641(7) Å).5d This
trend is reversed for the Ru-N(1), Ru-Cl(1), and Ru-Cl(2)
bond distances, which are 2.094(7), 2.431(3), and 2.463(3) Å
(cf. 2.168(2), 2.4122(7), and 2.4263(7) Å in trans-[RuCl2(PNP)-
(PPh3)]). The P(1)-Ru-P(2) angle in 16d is 161.3(1)° but
slightly smaller in trans-[RuCl2(PNP)(PPh3)], being 157.90(3)°.
Nickel, Palladium, and Platinum PNP Pincer Complexes.
The cationic PNP complexes of Ni(II) [Ni(PNP-Ph)Br]Br (17a),
[Ni(PNP-Pri)Br]Br (17a), and [Ni(PNP-But)Br]Br (17c) were
readily prepared by the reaction of NiBr2(DME) with the ligands
1a-c in 72 and 94% isolated yields (Scheme 10). Complexes
17 are thermally stable and can be handled in air. Their 31P-
{1H} NMR spectra contain a sharp singlet resonance that
confirms the equivalence of the phosphorus nuclei in accord
with a trans geometry. The chemical shifts of these signals are
observed at 66.1, 100.6, and 103.7 ppm. The appearance in the
13C{1H} NMR of the characteristic pattern of virtual triplets
for the ipso-Ph, i-Pr, and t-Bu carbons in 17a-c is also
consistent with strong coupling of these nuclei to mutually trans
phosphorus nuclei.
The X-ray crystal structure of 17c is shown in Figure 13 (a
structural view of 17a is given in the Supporting Information).
The Ni center adopts a distorted square-planar geometry defined
by two phosphorus atoms, the central nitrogen atom of the PNP
ligand, and a bromide atom. The coordination figure shows a
notable twist, with P(1) deviating by about 0.3 Å from the
meridional main plane because of packing effects. All Ni-P
bond lengths lie within the expected range for a trans-P-Ni-P
arrangement. The Ni-N(1) distance is 1.894(1) Å.
Figure 13. Structural view of [Ni(PNP-But)Br]Br‚0.5CH3OH (17c‚
0.5CH3OH) showing 50% thermal ellipsoids (C-bonded H atoms,
CH3OH, and Br- omitted for clarity). Selected bond lengths (Å)
and bond angles (deg): Ni-P(1) 2.2067(4), Ni-P(2) 2.2062(4),
Ni-N(1) 1.894(1), Ni-Br(1) 2.2987(2); P(1)-Ni-P(2) 169.73-
(2).
Cl (18a), [Pd(PNP-Pri)Cl]Cl (18b), [Pd(PNP-But)Br]Cl, [Pd-
(PNP-PhUndec)Br]Cl (19a), [Pd(PNP-PhHex)Br]Cl (19b), and
[Pd(PNPT-But)Br]Cl (21b) cleanly in good isolated yields
(Scheme 11). With ligands 1d-h the respective palladium
complexes turned out to be poorly soluble in most common
organic solvents. This could be circumvented by performing
the same reaction in the presence of 1 equiv of the halide
scavenger KCF3SO3 in CH3CN as the solvent. Accordingly, with
the ligands 1d-h and 3 the complexes [Pd(PNP-ETOL)Cl]CF3-
SO3 (20a), [Pd(PNP-BIPOL)Cl]CF3SO3 (20b), [Pd(PNP-BINOL)-
Cl]CF3SO3 (20c), [Pd(PNP-TARMe)Cl]CF3SO3 (20d), [Pd(PNP-
TARPr)Cl]CF3SO3 (20e), and [Pd(PNPT-Ph)Cl]CF3SO3 (21b)
were obtained, which exhibit very good solubility in most
organic solvents. Analogous platinum PNP complexes have been
prepared in the same manner by reacting [Pt(COD)Br2] with 1
equiv of ligands 1b, 1c, 1e, and 1g to yield the platinum
complexes 22 and 23 in high yields (Scheme 12). All palladium
and platinum PNP complexes are thermally robust off-white to
yellow solids that are stable to air both in the solid state and in
solution. The identity of the compounds was established by 1H,
13C{1H}, and 31P{1H} NMR spectroscopy and by elemental
Treatment of [Pd(COD)Cl2] with the ligands 1a-c, 2a, 2b,
and 3 in CH2Cl2 for 2 h afforded complexes [Pd(PNP-Ph)Cl]-
Scheme 11

1908 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
Table 1. Yields of the Suzuki-Miyaura Cross-Coupling of
Aryl and Alkyl Bromides with Phenyl Boronic Acid
Catalyzed by [Pd(PNP-Ph)Cl]Cl (18a), [Pd(PNP-Pri)Cl]Cl
(18b), and [Pd(PNP-But)Cl]Cl (18c)a
Scheme 12
entry
R
catalyst (mol %)
yield (%)
1
2
3
4
5
6
7
8
4-bromotoluene
4-bromotoluene
4-bromotoluene
4-bromoacetophenone
4-bromoacetophenone
4-bromoacetophenone
4-bromoanisole
4-bromoanisole
4-bromoanisole
18a (2)
18b (2)
18c (2)
91
90b
60b
98
18a (2)
18a (0.5)
18a (0.05)
18a (2)
18b (2)
18a (2)
18a (0.5)
18a (0.05)
18a (2)
18a (2)
18a (2)
18a (2)
18a (2)
18a (2)
98b
97b
98b
93b
96
analysis. The multinuclear NMR spectra of 18-23 bear no
unusual features and are not discussed here.
The identity of 18c and 20b was unequivocally established
by X-ray crystallography. Structural views of 18c and 20b are
depicted in Figures 14 and 15, with selected geometric data
reported in the captions. The molecules display the usual square-
planar coordination around the palladium center. Like in the
iron complexes Pd-P bonds to arene bearing phosphorus (18c‚
9
10
11
12
13
14
15
16
17
4-bromoanisole
4-bromoanisole
95b
87b
94
4-bromonitrobenzene
2,6-dimethylbromobenzene
2,6-dimethylbromobenzene
1-bromo-2-ethylbenzene
1-bromododecane
2-bromopyridine
66b
78
83
93b
94
a Reaction conditions: 1.0 mmol of bromide, 1.5 mmol of PhB(OH)2,
2.0 mmol of Cs2CO3, 5 mL of dioxane, 80 °C, 3 h. b The reaction was
stirred for 16 h.
2CH2Cl2) are about 0.05 Å longer than to oxygen-bearing
phosphorus (20b‚(C2H5)2O‚2CH3CN).
Suzuki-Miyaura Coupling. Palladium complexes contain-
ing PCP pincer ligands are excellent catalysts for the Suzuki-
Miyaura coupling.22 On the basis of these findings we were
interested in whether palladium complexes containing PNP
ligands exhibit similar reactivities in C-C bond coupling
reactions. Accordingly, we investigated the activity of complexes
18a-c as catalysts for the coupling of various aryl bromides
with phenyl boronic acid. The results of this study are
summarized in Table 1.
The coupling reaction of 4-bromotoluene with phenylboronic
acid catalyzed by 18a-c proceeded smoothly to give 4-meth-
ylbiphenyl in 91, 90, and 60% isolated yields (entries 1-3).
This reactivity trend suggests that both the stronger donating
ability and the steric demand of the PR2 substituents make the
PNP ligands more electron-rich and renders catalyst 18c less
active. Thus, only 18a has been utilized as catalyst. The coupling
of 4-bromoacetophenone with phenylboronic acid proceeds with
97% isolated yield with a catalyst loading of 0.05 mol % (entry
7), while the electronically deactivated and thus more challeng-
ing substrate 4-bromoanisole can be efficiently coupled with
87% isolated yield with a catalyst loading of 0.05 mol % (entry
12). Even the sterically demanding 2,6-dimethylbromobenzene
and 1-bromo-2-ethylbenzene gave acceptable yields, viz., 78
and 83% (entries 15 and 16). Attempts to couple 2-bromopy-
ridine and 1-bromododecane, the latter bearing â-hydrogen
Figure 14. Structural view of [Pd(PNP-But)Cl]Cl‚2CH2Cl2
(18c‚2CH2Cl2) showing 30% thermal ellipsoids (C-bonded H atoms,
CH2Cl2, and Cl- omitted for clarity). Selected bond lengths (Å)
and bond angles (deg): Pd-P(1) 2.2987(5), Pd-P(2) 2.2985(5),
Pd-N(1) 2.015(2), Pd-Cl(1) 2.3002(6), P(1)-Pd-P(2) 166.54-
(2).
(20) Sullivan, B. P.; Calvert, J. M.; Meyer, T. J. Inorg. Chem. 1980, 19,
1404.
(21) Doberer, D.; Slugovc, C.; Schmid, R.; Kirchner, K.; Mereiter, K.
Monatsh. Chem. 1999, 130, 717.
Figure 15. Structural view of [Pd(PNP-BIPOL)Cl]CF3SO3‚
(C2H5)2O‚2CH3CN (20b‚(C2H5)2O‚2CH3CN) showing 50% thermal
ellipsoids (C-bonded H atoms, second independent complex, and
solvent molecules omitted for clarity). Selected bond lengths (Å)
and bond angles (deg): Pd-P(1) 2.251(2), Pd-P(2) 2.252(2), Pd-
N(1) 2.028(4), Pd-Cl 2.271(2), P(1)-Pd-P(2) 165.27(5).
(22) (a) Miyazaki, F.; Yamaguchi, K.; Shibasaki, M. Tetrahedron Lett.
1999, 40, 7379. (b) Morales-Morales, D.; Grause, C.; Kasaoka, K.; Redon,
R.; Cramer, R. E.; Jensen, C. M. Inorg. Chim. Acta 2000, 300, 958. (c)
Morales-Morales, D.; Redon, R.; Yung, C.; Jensen, C. M. Chem. Commun.
2000, 1619. (d) Bedford, R. B.; Draper, S. M.; Scully, P. N.; Welch, S. L.
New J. Chem. 2000, 24, 745.

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1909
The synthesis of N,N′-di-10-undecenyl-2,6-diaminopyridine and
N,N′-dihexyl-2,6-diaminopyridine is described in the Supporting
Information. The deuterated solvents were purchased from Aldrich
and dried over 4 Å molecular sieves.1H, 13C{1H}, and 31P{1H} NMR
spectra were recorded on a Bruker AVANCE-250 spectrometer and
atoms, were also successful, resulting in reasonable yields
(entries 17 and 18).
It has to be noted that recently evidence was presented that
pincer ligands are merely precatalysts, generating some forms
of metallic palladium(0), which actually does the catalysis.23
Pincer ligands possessing only phosphinito donors decomposed
even more easily and lead to more active sources of metallic
palladium. In the present catalytic reactions we cannot exclude
such a possibility.
1
were referenced to SiMe4 and H3PO4 (85%), respectively. H and
1
13C{1H} NMR signal assignments were confirmed by H-COSY,
135-DEPT, and HMQC(1H-13C) experiments.
N,N′-Bis(diphenylphosphino)-2,6-diaminopyridine (PNP-Ph)
(1a). This compound was prepared according to the literature.13 1
H
NMR (δ, CDCl3, 20 °C): 7.36-7.34 (m, 21H, Ph, py4), 6.54-
6.51 (dd, J ) 7.9 Hz, J ) 1.6 Hz, 2H, py3,5), 5.39 (s, 2H, NH).
13C{1H} NMR (δ, CDCl3, 20 °C): 157.6 (d, J ) 20.2 Hz, py2,6),
139.9 (d, J ) 12.1 Hz, py4), 134.0 (Ph), 131.3 (d, J ) 20.9 Hz,
Ph2,6), 129.2 (Ph4), 128.5 (d, J ) 6.7 Hz, Ph3,5), 99.2 (d, J ) 14.8
Hz, py3,5). 31P{1H} NMR (δ, CDCl3, 20 °C): 28.0.
Concluding Remarks
In sum we have shown that new achiral and chiral PNP
ligands are easily prepared from commercially available and
inexpensive 2,6-diaminopyridine and 2,6-diamino-4-phenyl-
1,3,5-triazine, which can be varied in modular fashion by
choosing the appropriate monochloro phosphine or phosphite
R2PCl. These, in turn, are easily accessible in high yields from
a large array of both achiral and chiral diols and PCl3. This
methodology contrasts the generally arduous synthetic proce-
dures required for the preparation of 1,3-bis(phosphino)-
benzenes. In addition, we showed that N,N′-dialkylated diamines
such as N,N′-di-10-undecenyl-2,6-diaminopyridine and N,N′-
dihexyl-2,6-diaminopyridine can also be utilized for the syn-
thesis of new PNP ligands. In conjunction with the transition
metal fragments [Mo(CO)3], [Fe(CH3CN)3]2+, Ru(PPh3)Cl2, and
MX (M ) Ni, Pd, Pt; X ) Cl, Br, CF3COO) stable PNP
complexes are formed. For instance, [Mo(CO)3(CH3CN)3] reacts
with PNP ligands to give [Mo(PNP)(CO)3]. Stable octahedral
dicationic trisacetonitrile complexes are obtained on treatment
of [Fe(H2O)6]2+ with PNP ligands in CH3CN. Various cis or
trans dichloro complexes of the type [Ru(PNP)(PPh3)Cl2] are
afforded via ligand exchange of RuCl2(PPh3)3 with a stoichio-
metric amount of the respective PNP ligands, and finally
[M(PNP)X]Y (M ) Ni, Pd, Pt; X ) Cl, Br; Y ) Cl, Br, CF3-
SO3) complexes are easily accessible from [NiBr2(DME)] and
[M(COD)X2] (M ) Pd, Pt; X ) Cl, Br) in the presence or
absence of KCF3SO3 as halide scavenger. We have also shown
that some of these compounds exhibit interesting reactivities
leading to novel seven-coordinate pincer complexes in the case
of molybdenum or are catalytically active in C-C bond forming
reactions such as in the case of palladium. We are currently
studying our new PNP ligands in conjunction with other
transition metals including Re, Rh, and Ir. Furthermore, the
synthetic methodology of obtaining PNP ligands is currently
being applied to achiral and chiral PCP ligands based on 1,3-
diaminobenzene and derivatives thereof. These studies will be
reported in due course.
N,N′-Bis(diisopropylphosphino)-2,6-diaminopyridine (PNP-
Pri) (1b). To a suspension of 2,6-diaminopyridine (1.8 g, 16.4
mmol) in toluene was added NEt3 (4.0 mL, 32.8 mmol). The
mixture was then cooled to 0 °C, and PPri2Cl (5.0 g, 32.8 mmol)
was added dropwise. Upon further cooling to -70 °C, n-BuLi (32.8
mmol, 14.0 mL of a 2.3 M solution in hexane) was slowly added.
The solution was allowed to reach room temperature and was then
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: 4.3 g (78%).
Anal. Calcd for C17H33N3P2: C, 59.81; H, 9.74; N, 12.31. Found:
C, 59.79; H, 9.66; N, 12.10. 1H NMR (δ, CDCl3, 20 °C): 7.23 (t,
J ) 8.0 Hz, 1H, py4), 6.42 (dd, J ) 7.8 Hz, J ) 2.3 Hz, 2H, py3,5),
4.29 (d, J ) 11.2 Hz, 2H, NH), 1.78-1.67 (m, J ) 7.0 Hz, J )
2.0 Hz, CH(CH3)2), 1.08-0.99 (m, 24H, CH(CH3)2). 13C{1H} NMR
(δ, CDCl3, 20 °C): 159.5 (d, J ) 20.3 Hz, py2,6), 139.1 (py4), 98.1
(d, J ) 18.4 Hz, py3,5), 26.3 (d, J ) 10.7 Hz, CH(CH3)2), 18.6 (d,
J ) 19.6 Hz, CH(CH3)2), 17.1 (d, J ) 7.7 Hz, CH(CH3)2). 31P-
{1H} NMR δ, CDCl3, 20 °C): 49.0.
N,N′-Bis(di-tert-butylphosphino)-2,6-diaminopyridine (PNP-
But) (1c). This ligand has been prepared analogously to 1b with
NEt3 (3.4 mL, 27.6 mmol), 2,6-diaminopyridine (1.5 g, 13.8 mmol),
PBut2Cl (5.0 g, 27.6 mmol), and n-BuLi (27.6 mmol, 15.0 mL of
a 1.9 M solution in hexane) as the starting materials. Yield: 3.9 g
(73%). Anal. Calcd for C21H41N3P2: C, 63.45; H, 10.40; N, 10.57.
Found: C, 63.37; H, 10.66; N, 10.41. 1H NMR (δ, CDCl3, 20 °C):
7.25 (t, J ) 7.3 Hz, 1H, py4), 6.48 (dd, J ) 8.0 Hz, J ) 2.5 Hz,
2H, py3,5), 4.64 (d, J ) 11.2 Hz, 2H, NH), 1.22-1.15 (m, 36H,
C(CH3)3). 13C{1H} NMR (δ, CDCl3, 20 °C): 155.1(py2,6), 138.7
(py4), 98.2 (d, J ) 18.5 Hz, py3,5), 29.4 (d, J ) 13.9 Hz, C(CH3)3),
27.8 (d, J ) 15.0 Hz, C(CH3)3). 31P{1H} NMR (δ, CDCl3, 20 °C):
60.2.
N,N′-Bis(1,2-ethandiolphosphino)-2,6-diaminopyridine (PNP-
ETOL) (1d). To a suspension of 2,6-diaminopyridine (0.6 g, 5.6
mmol) in toluene was added NEt3 (1.6 mL, 11.2 mmol), and the
mixture was cooled to 0 °C. Upon addition of 2-chloro-1,3,2-
dioxaphospholane (1.4 g, 11.2 mmol) the mixture was stirred at
80 °C overnight, whereupon a white solid precipitated. After
removal of insoluble materials by filtration, the solvent was removed
under vacuum, affording a yellow oil, which was recrystallized from
toluene/n-hexane (1:1). Yield: 1.4 g (64%). Anal. Calcd for
C9H13N3O4P2: C, 37.38; H, 4.53; N, 14.53. Found: C, 37.49; H,
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. The
starting materials PPh2Cl, PPri2Cl, PBut2Cl, and 2,6-diamino-4-
phenyl-1,3,5-triazine were purchased from Aldrich and used without
further purification. 2-Chloro-1,3,2-dioxaphospholane,24 2-chlorodi-
benzo[d,f][1,3,2]dioxaphosphepine,25 S-2-chlorodinaphtho[2,1-d:
1′2′-f][1,3,2]dioxaphosphepine,26 2-chloro-(4S,5S)-dicarbomethoxy-
1,3,2-dioxaphospholane, and 2-chloro-(4R,5R)-dicarboisopropoxy-
1,3,2-dioxaphospholane27 were prepared according to the literature.
1
4.45; N, 14.56. H NMR (δ, CDCl3, 20 °C): 7.28 (t, J ) 7.9 Hz,
(25) (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.
(26) Sablong, R.; Newton, C.; Dierkes, P.; Osborn, J. A. Tetrahedron
Lett. 1996, 37, 4933.
(23) (a) Sommer, W. J.; Yu, K.; Sears, J. S.; Ji, Y.; Zheng, X.; Davis,
R. J.; Sherill, C. D.; Jones, C. W.; Weck, M. Organometallics 2005, 24,
4351. (b) Eberhard, M. R. Org. Lett. 2004, 6, 2125.
(24) Lucas, H. J.; Mitchell, F. W., Jr.; Scully, C. N. J. Am. Chem. Soc.
1950, 72, 5491.
(27) Kadyrov, R.; Heller, D.; Selke, R. Tetrahedron: Asymmetry 1998,
9, 329.

1910 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
1H, py4), 6.29 (d, J ) 7.9 Hz, 2H, py3,5), 5.70 (s, 2H, NH), 4.20-
4.13 (m, 4H, CH2), 4.01-3.91 (m, 4H, CH2). 13C{1H} NMR (δ,
CDCl3, 20 °C): 157.0 (py2,6), 139.6 (py4), 100.8 (d, J ) 12.1 Hz,
py3,5), 63.7 (CH2), 63.5 (CH2). 31P{1H} NMR (δ, CDCl3, 20 °C):
129.9.
in diethyl ether and cooled to -70 °C. n-BuLi (5.90 mmol, 2.7
mL of a 2.20 M solution in hexane) was added slowly. The solution
was allowed to reach room temperature and was then stirred for 1
h. After that, the solution was cooled to -10 °C, and ClPPh2 (1.06
mL in 9 mL, 5.90 mmol) was added dropwise. The mixture was
stirred overnight at room temperature. After that, the solution was
filtered and the solvent was removed under vacuum. An orange
oil was obtained. Yield: 2.3 g (87%). 1H NMR (δ, CDCl3, 20 °C):
7.45-7.35 (m, 11H, Ph and py4), 6.59 (dd, J ) 8.0 Hz, J ) 2.3
Hz, 1H, py3), 5.81 (d, J ) 7.9, 1H, py5), 4.21 (bm, 1H, NH), 3.53-
3.41 (m, 2H, CH2NP), 3.21-3.13 (m, 2H, CH2NH) 1.65-1.52 (m,
2H, CH2), 1.44-1.19 (m, 8H, CH2), 1.08-0.69 (m, 14H, CH2 and
CH3). 31P{1H} NMR (δ, CDCl3, 20 °C): 47.8.
N,N′-Dihexyl-N,N′-bis(diphenylphosphino)-2,6-diaminopyri-
dine (PNP-PhHexyl) (2a). This ligand has been prepared analogously
to 2a′ with 2a′ (1.3 g, 2.86 mmol), PPh2Cl (513 µL, 2.86 mmol),
and n-BuLi (2,86 mmol, 1.24 mL of a 2.2 M solution in hexane)
as the starting materials. Yield: 1.8 g (98%). 1H NMR (δ, CDCl3,
20 °C): 7.45-7.35 (m, 21H, Ph and py4), 6.77 (dd, J ) 8.1 Hz, J
) 2.4 Hz, 2H, py3,5), 3.53-3.41 (m, 4H, CH2N), 1.46-1.20 (m,
4H, CH2) 1.05-0.70 (m, 18H, CH2 and CH3). 13C{1H} NMR (δ,
CDCl3, 20 °C): 159.0 (py2,6), 137.7 (py4), 132.6 (Ph), 128.7 (Ph),
128.3 (Ph) 100.0 (py3,5), 48.0 (NCH2), 31.3 (CH2), 28.9 (CH2), 26.7
(CH2), 22.5 (CH2), 13.9 (CH3).31P{1H} NMR (δ, CDCl3, 20 °C):
48.1.
N,N′-Bis(dibenzo[d,f][1,3,2]dioxaphosphepine)-2,6-diaminopy-
ridine (PNP-BIPOL) (1e). This ligand has been prepared analo-
gously to 1d with NEt3 (1.5 mL, 12.0 mmol), 2,6-diaminopyridine
(0.6 g, 6.0 mmol), and 2-chlorodibenzo[d,f][1,3,2]dioxaphosphepine
(3.0 g, 12.0 mmol) as the starting materials. Yield: 3.4 g (79%).
Anal. Calcd for C29H21N3O4P2: C, 64.81; H, 3.94; N, 7.82.
1
Found: C, 64.89; H, 4.06; N, 7.72. H NMR (δ, CDCl3, 20 °C):
7.50-7.15 (m, 14H, Ph3,5 and Ph4), 6.40 (d, J ) 7.8 Hz, 1H, py4),
6.11 (dd, J ) 31.6 Hz, J ) 7.9 Hz, 2H, Ph2,6), 5.89 (t, J ) 7.8 Hz,
2H, py3,5), 4.32 (s, 2H, NH). 13C{1H} NMR (δ, CDCl3, 20 °C):
154.2 (d, J ) 17.3 Hz, py2,6), 149.5 (d, J ) 3.8 Hz, Ph), 140.0
(py4), 131.6 (d, J ) 3.1, Ph), 129.8 (Ph), 129.2 (Ph), 125.3 (Ph),
122.3 (Ph), 101.5 (d, J ) 12.3 Hz, py3,5). 31P{1H} NMR (δ, CDCl3,
20 °C): 147.5.
N,N′-Bis(S-dinaphtho[2,1-d:1′2′-f][1,3,2]dioxaphosphepine)-
2,6-diaminopyridine (PNP-BINOL) (S-1f). A solution of 2,6-
diaminopyridine (46 mg, 0.42 mmol) in THF (10 mL) was cooled
to -70 °C, and n-BuLi (0.85 mmol, 0.47 mL of a 2.10 M solution
in hexane) was added. The reaction was stirred until the temperature
was -20 °C, and S-2-chloro-dinaphtho[2,1-d:1′2′-f][1,3,2]dioxa-
phosphepine (300 mg, 0.85 mmol) in 2 mL of THF was added.
After allowing the reaction to stir overnight at room temperature,
the mixture was filtered, and the solvent removed under vacuum.
Yield: 350 mg (94%). Anal. Calcd for C45H29N3O4P2: C, 73.27;
H, 3.96; N, 5.70. Found: C, 73.39; H, 3.80; N, 5.52. 1H NMR (δ,
CDCl3, 20 °C): 8.00-7.85 (m, 8H, Ph), 7.54-7.29 (m, 16H, Ph
and py4), 6.11-6.02 (m, J ) 7.9 Hz, J ) 13.7 Hz, 2H, py3,5), 5.72
(d, J ) 8.2 Hz, 2H, NH). 13C{1H} NMR (δ, CDCl3, 20 °C): 162.2
(py2,6), 139.7 (py4), 130.4 (Ph), 129.9 (Ph), 129.8 (Ph), 128.5 (Ph),
128.4 (Ph), 126.9 (Ph), 126.7 (Ph), 126.4 (Ph), 126.2 (Ph), 125.0
(Ph); 100.6 (py3,5). 31P{1H} NMR (δ, CDCl3, 20 °C): 146.1.
N,N′-Bis(4S,5S-dicarbomethoxy-1,3,2-dioxaphospholane)-2,6-
diaminopyridine (PNP-TARMe) (S,S-1g). This ligand has been
prepared analogously to 1d with NEt3 (2.3 mL, 16.4 mmol), 2,6-
diaminopyridine (0.9 g, 8.2 mmol), and 2-chloro-(4S,5S)-dicar-
bomethoxy-1,3,2-dioxaphospholane (4.0 g, 16.4 mmol) as the
starting materials. Yield: 1.6 g (66%). Anal. Calcd for C17H21-
N3O12P2: C, 39.17; H, 4.06; N, 8.06. Found: C, 39.19; H, 4.16;
N, 7.96. 1H NMR (δ, CDCl3, 20 °C): 7.30 (t, J ) 7.9 Hz, 1H, py4)
6.45 (s, 2H, NH), 6.28 (d, J ) 7.9 Hz, 2H, py3,5), 5.06-5.03 (m,
2H, CH), 4.81-4.75 (m, 2H, CH), 3.83 (s, 6H, CH3). 13C{1H} NMR
(δ, CDCl3, 20 °C): 171.3 (CO), 169.0 (CO), 153.8 (d, J ) 14.9
Hz, py2,6), 139.7 (py4), 101.9 (d, J ) 10.3 Hz, py3,5), 77.6 (CH),
77.1 (CH), 76.7 (t, J ) 10.1 Hz, CH3), 53.2 (d, J ) 15.5 Hz, CH3).
31P{1H} NMR (δ, CDCl3, 20 °C): 142.9.
N,N′-Bis(4R,5R-dicarboisopropoxy-1,3,2-dioxaphospholane)-
2,6-diaminopyridine (PNP-TARPr) (R,R-1h). This ligand has been
prepared analogously to 1d with NEt3 (2.3 mL, 16.4 mmol), 2,6-
diaminopyridine (0.9 g, 8.2 mmol), and 2-chloro-(4R,5R)-dicar-
boisopropoxy-1,3,2-dioxaphospholane (5.0 g, 16.4 mmol) as the
starting materials. Yield: 5.0 g (95%). Anal. Calcd for C25H37-
N3O12P2: C, 47.40; H, 5.89; N, 6.63. Found: C, 47.50; H, 5.74;
N, 6.74. 1H NMR (δ, CDCl3, 20 °C): 7.28 (t, J ) 7.9 Hz, 1H, py4)
6.54 (d, J ) 4.0 Hz, 2H, NH), 6.26 (d, J ) 7.9 Hz, 2H, py3,5),
5.20-5.06 (m, 4H, (CH3)2CH), 4.86-4.84 (m, 2H, CH), 4.62-
4.56 (m, 2H, CH), 1.32-1.27 (m, 24H, (CH3)2CH). 13C{1H} NMR
(δ, CDCl3, 20 °C): 170.4 (CO), 167.8 (CO), 154.1 (d, J ) 16.1
Hz, py2,6), 139.6 (py4), 101.5 (d, J ) 10.1 Hz, py3,5), 77.4 (CH),
76.5 (CH), 70.8 ((CH3)2CH), 70.2 ((CH3)2CH), 21.6 ((CH3)2CH).
31P{1H} NMR (δ, CDCl3, 20 °C): 142.7.
N,N′-Diundec-10-enyl-N-bis(diphenylphosphino)-2,6-diami-
nopyridine (2b′). This ligand has been prepared analogously to
2a′ with undecaminopyridine (911 mg, 2.20 mmol), PPh2Cl (396
µL, 2.20 mmol), and n-BuLi (2.20 mmol, 1 mL of a 2.2 M solution
in hexane) as the starting materials. Yield: 1.3 g (98%). 1H NMR
(δ, CDCl3, 20 °C): 7.47-7.21 (m, 11H, Ph and py4), 6.78 (dd, J
) 8.1 Hz, J ) 2.4 Hz, 2H, py3,5), 6.60 (dd, J ) 8.1 Hz, J ) 2.4
Hz, 1H, py3,5), 5.92-5.77 (m, 2H, CHdCH2), 5.71 (d, J ) 7.9 Hz,
2H, py3,5), 5.05-4.93 (m, 4H, CHdCH2), 4.23 (bm, 1H, NH),
3.51-3.42 (m, 2H, CH2NP), 3.22-3.14 (m, 2H, CH2N) 2.10-1.98
(m, 4H, CH2), 1.63-1.55 (m, 2H, CH2), 1.45-0.77 (m, 28H, CH2
and CH3). 31P{1H} NMR (δ, CDCl3, 20 °C): 47.9.
N,N′-Diundec-10-enyl-N,N′-bis(diphenylphosphino)-2,6-di-
aminopyridine (PNP-PhUndec) (2b). This ligand has been prepared
analogously to 2a with 2b′ (887 mg, 1.48 mmol), PPh2Cl (236µL,
1.48 mmol), and n-BuLi (1.48 mmol, 674 µL of a 2.2 M solution
in hexane) as the starting materials. Yield: 0.9 g (89%). 1H NMR
(δ, CDCl3, 20 °C): 7.46-7.30 (m, 21H, Ph and py4), 6.75 (dd, J
) 8.1 Hz, J ) 2.5 Hz, 2H, py3,5), 5.88-5.72 (m, 2H, CHdCH2),
5.03-4.90 (m, 4H, CHdCH2), 3.53-3.39 (m, 4H, CH2), 2.05-
1.96 (m, 4H, CH2), 1.43-0.74 (m, 28H, CH2). 13C{1H} NMR (δ,
CDCl3, 20 °C): 159.1 (py2,6), 139.2 (CHdCH2), 138.0 (py4), 132.7
(Ph), 128.8 (Ph), 128.4 (Ph), 114.2 (CH2dCH), 100.3 (py3,5), 48.2
(NCH2), 33.9 (dCHCH2), 29.5(CH2), 29.2(CH2), 29.0(CH2), 28.3-
(CH2), 28.1(CH2), 28.0(CH2), 27.1 (CH2).31P{1H} NMR (δ, CDCl3,
20 °C): 48.0.
N,N′-Bis(diphenylphosphino)-2,6-diamino-4-phenyl-1,3,5-tri-
azine (PNPT-Ph) (3). A suspension of 2,6-diamino-4-phenyl-1,3,5-
triazine (0.5 g, 2.67 mmol) in 30 mL of THF was treated with
NEt3 (0.82 mL, 5.88 mmol). After cooling to 0 °C a solution of
PPh2Cl (0.96 mL, 5.34 mmol) in 20 mL of THF was added
dropwise. The suspension was warmed to room temperature and
stirred overnight. After that, the precipitate was filtered off and
the solvent removed under vacuum. The remaining white solid was
1
used without further purification. Yield: 1.4 g (95%). H NMR
(δ, C6D6, 20 °C): 7.44-7.03 (m, 25H, Ph and PPh), 6.33 (s, 2H,
NH). 13C{1H} NMR (δ, C6D6, 20 °C): 171.9 (triaz4), 168.7 (dd, J
) 17.0 Hz, J ) 2.8 Hz, triaz2,6), 139.6 (d, J ) 15.6 Hz, PPh1),
136.7 (Ph1), 131.7 (d, J ) 22.1 Hz, PPh2,6), 131.7 (Ph4), 129.1
(PPh4), 128.5 (d, J ) 6.9 Hz, PPh3,5), 128.2 and 128.1 (Ph2,3,5,6).
31P{1H} NMR (δ, C6D6, 20 °C): 29.1.
N,N′-Dihexyl-N-diphenylphosphino-2,6-diaminopyridine (2a′).
N,N′-Dihexyl-2,6-diaminopyridine (1.6 g, 5.90 mmol) was dissolved

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1911
[Mo(PNP-Pri)(CO)3]‚CH3CN (4a‚CH3CN). Mo(CO)6 (300 mg,
0.88 mmol) in 10 mL of CH3CN was refluxed in a Schlenk tube
for 2 h. The yellow solution was cooled to room temperature and
1b (233 mg, 0.88 mmol) was added. The mixture was stirred
overnight at room temperature. Removal of the solvent afforded
4a as a yellow solid. Yield: 420 mg (90%). Anal. Calcd for C22H36-
MoN4O3P2: C, 46.98; H, 6.45; N, 9.96. Found: C, 46.89; H, 6.16;
(CH3CN), 136.7 (Ph), 131.5 (Ph), 131.0 (Ph), 129.2 (Ph), 100.9
(py3,5), 3.4 (CH3CN). 31P{1H} NMR (δ, CD3CN, 20 °C): 103.9.
[Fe(PNP-BIPOL)(CH3CN)3](BF4)2 (9d). This complex has been
prepared analogously to 9a with 1e (2.0 g, 3.7 mmol) and [Fe-
(H2O)6](BF4)2 (1.3 g, 3.7 mmol) as the starting materials. Yield:
2.7 g (80%). Anal. Calcd for C35H30B2F8FeN6P2O4: C, 47.23; H,
1
3.40; N, 9.44. Found: C, 47.10; H, 3.31; N, 9.55. H NMR (δ,
1
N, 9.12. H NMR (δ, CD3CN, 20 °C): 7.16 (t, J ) 7.9 Hz, 1H,
CD3CN, 20 °C): 8.89 (s, 2H, NH), 7.84-7.81 (m, 14H, Ph), 7.24-
7.21 (m, 1H, py4), 7.00-6.93 (m, 2H, Ph), 6.52 (d, J ) 8.2 Hz,
2H, py3,5), 2.32 (s, 6H, CH3CN), 1.59 (s, 3H, CH3CN). 13C{1H}
NMR (δ, CD3CN, 20 °C): 159.9 (t, J ) 13.2 Hz, py2,6), 151.4
(Ph), 148.6 (Ph), 146.1 (py4), 142.7 (Ph), 137.7 (CH3CN), 130.5
(Ph), 127.4 (Ph), 122.1 (Ph), 102.6 (py3,5), 4.3 (CH3CN). 31P{1H}
NMR (δ, CD3CN, 20 °C): 186.7.
py4), 6.37 (bs, 2H, NH), 6.13 (d, J ) 7.9 Hz, 2H, py3,5), 2.45-
2.18 (m, 4H, CH), 1.33-1.03 (m, 24H, CH3). 13C{1H} NMR (δ,
CD3CN, 20 °C): 231.4 (t, J ) 5.8 Hz, CO), 216.9 (t, J ) 10.4 Hz,
CO), 161.0 (t, J ) 7.8 Hz, py2,6), 137.7 (py4), 97.1 (t, J ) 3.1 Hz,
py3,5), 31.6 (t, J ) 10.4 Hz, CH), 18.1 (t, J ) 3.0 Hz, CH3), 17.8
(t, J ) 3.9 Hz, CH3). 31P{1H} NMR (δ, CD3CN, 20 °C): 131.9.
IR (KBr, cm-1): νCdO 1938 (m, νCdO), 1907 (m, νCdO), 1824 (s,
Deprotonation of [Fe(PNP-BIPOL)(CH3CN)3](BF4)2‚CH3CN
(9d‚CH3CN). Formation of [Fe(PNP-BIPOL)(CH3CN)3]BF4
(12). Method 1: A solution of 9d (150 mg, 0.17 mmol) in
acetonitrile was treated with an excess of NaHg (3%), whereupon
an immediate formation of gas (H2) took place. The mixture was
stirred until the evolution of dihydrogen had ceased. Insoluble
materials were then removed by filtration, and the solvent was
evaporated under reduced pressure. The resulting dark brown solid
was washed twice with Et2O and dried under vaccum. Yield: 104
mg (76%). Method 2. A solution of 9d (500 mg, 0.56 mmol) in
acetonitrile was chromatographed over basic Al2O3, yielding a dark
brown solution. Removal of the solvent under reduced pressure
gave 12 as a dark brown solid. Yield: 367 mg (81%). Anal. Calcd
for C37H32BF4FeN7O4P2: C, 52.70; H, 3.82; N, 11.63. Found: C,
52.55; H, 3.42; N, 11.98. The proton NMR spectrum was
uninformative due to broad and featureless resonances. 13C{1H}
NMR (δ, CD3CN, 20 °C): 158.9 (py2,6), 149.0 (py4), 141.7
(CH3CN), 130.3 (Ph), 129.8 (Ph), 127.0 (Ph), 122.2 (Ph), 101.7
(py3,5), 4.1 (CH3CN). Quaternary carbons could not be detected.
31P{1H} NMR (δ, CD3CN, 20 °C): 194.4.
ν
CdO).
[Mo(PNP-But)(CO)3]‚CH3CN (4b‚CH3CN). This complex has
been prepared analogously to 4a with [Mo(CO)6] (512 mg, 1.97
mmol) and 1c (782 mg, 1.97 mmol) as starting materials. The
product was purified by chromatography (neutral Al2O3, eluent:
CH2Cl2). Yield: 840 mg (74%). Anal. Calcd for C26H44Mo-
N4O3P2: C, 53.15; H, 7.55; N, 9.54. Found: C, 53.21; H, 7.17; N,
9.41. 1H NMR (δ, CD2Cl2, 20 °C): 7.18 (t, J ) 7.9 Hz, 1H, py4),
6.13 (d, J ) 7.9 Hz, 2H, py3,5), 5.25 (bs, 2H, NH), 1.42-1.35 (m,
36H, CH3). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 223.1 (t, J ) 9.6
Hz, CO), 207.3 (t, J ) 8.4 Hz, CO), 160.6 (t, J ) 6.5 Hz, py2,6),
137.9 (py4), 97.8 (py3,5), 39.9 (t, J ) 5.0 Hz, CCH3), 29.3 (d, J )
3.8 Hz, CH3), 29.2 (d, J ) 3.8 Hz, CH3). 31P{1H} NMR (δ, CD2-
Cl2, 20 °C): 148.8. IR (KBr, cm-1): 1925 (s, νCdO), 1822 (s,
νCdO), 1811 (s, νCdO).
[Mo(PNP-Pri)(CO)3I]I (7a). To a solution of 4a (168 mg, 0.32
mmol) in 5 mL of CH2Cl2 was added 1 equiv of I2 (82 mg, 0.32
mmol). Removing the solvent after 10 min afforded 7a as a dark
red solid. Yield: 230 mg (92%). Anal. Calcd for C20H33-
MoN3O3I2P2: C, 30.99; H, 4.29; N, 5.42. Found: C, 31.15; H, 4.16;
Reaction of 12 with HBF4‚OEt2. Formation of [Fe(PNP-
BIPOL)(CH3CN)3](BF4)2 (9d). A 5 mm NMR tube was charged
with 12 (30 mg, 0.04 mmol) in CD3CN (0.5 mL). Upon addition
of HBF4‚OEt2 (2.3 µL, 0.04 mmol), the color of the solution
changed from brown to orange. The reaction was monitored by 1H
and 31P{1H} NMR spectroscopy, and quantitative formation of 9d
was observed.
1
N, 5.55. H NMR (δ, CD2Cl2, 20 °C): 8.10 (bs, 2H, NH), 7.43-
7.19 (m, 3H, py), 3.87-3.65 (m, 2H, CH), 3.14-2.84 (m, 2H, CH),
1.70-1.16 (m, 24H, CH3). 31P{1H} NMR (δ, CD2Cl2, 20 °C):
114.0. IR (KBr, cm-1): 1969 (s, νCdO), 1938 (s, νCdO), 1858 (m,
ν
CdO). If 4a is treated with 2 equiv of I2 under the same reaction
conditions, [Mo(PNP-Pri)(CO)3I]I3 (7b) was obtained, exhibiting
NMR spectra identical with those of 7a.
[Fe(PNP-Ph)(bipy)(CH3CN)](BF4)2‚CH3NO2 (13‚CH3NO2).
2,2′-Bipyridine (28 mg, 0.18 mmol) was added to a solution of 9a
(150 mg, 0.18 mmol) in CH3NO2, whereupon the color of the
solution immediately turned deep red. After the mixture was stirred
at room temperature for 2 h, the solvent was evaporated in a
vacuum, and the solid was precipitated, washed twice with Et2O,
and evaporated to dryness, yielding 154 mg (95%) of a deep red
solid. Anal. Calcd for C42H39B2F8FeN7O2P2: C, 52.26; H, 4.07;
[Mo(PNP-Pri)(CH3CN)(CO)2I]I (8). To a solution of 4b (168
mg, 0.32 mmol) in 2 mL of CH3CN was added 1 equiv of I2 (82
mg, 0.32 mmol). The reaction mixture was stirred overnight at room
temperature. 8 was isolated as a dark red microcrystalline precipi-
tate. Yield: 120 mg (70%). Anal. Calcd for C21H36N4O2MoP2: C,
47.20; H, 6.79; N, 10.48. Found: C, 47.44; H, 6.98; N, 10.76. 1H
NMR (δ, CD3CN, 20 °C): 7.98 (bs, 1H, NH), 7.62-7.43 (m, 2H,
NH, py4), 7.01 (d, J ) 8.1 Hz, 1H, py3), 6.88 (d, J ) 8.1 Hz, 1H,
py3), 3.74-3.55 (m, 1H, CH), 3.05-2.84 (m, 3H, CH), not observed
(3H,CH3CN), 1.63-1.11 (m, 24H, CH3). 31P{1H} NMR (δ, CD3-
CN, 20 °C): 113.8. IR (KBr, cm-1): 2299 (w, νCtN), 2269 (w,
1
N, 10.16. Found: C, 52.76; H, 4.26; N, 9.98. H NMR (δ, CD3-
NO2, 20 °C): 8.66-8.64 (m, 2H, bipy1), 8.57-8.54 (d, J ) 8.2
Hz, 2H, NH), 8.11-8.06 (m, 2H, bipy4), 7.72-7.53 (m, 10H, Ph,
py4), 7.43-7.37 (m, 2H, bipy2,3), 7.18-6.75 (m, 11H, Ph), 6.49
(s, 2H, py3,5), 1.68-1.67 (t, J ) 1.48 Hz, CH3CN). 13C{1H}NMR
(CD3NO2, δ): 163.2 (py2,6), 156.8 (bipy5), 154.0 (bipy1), 141.5
(py4), 138.0 (bipy3), 131.5 (Ph), 130.6 (Ph2,6), 130.0 (Ph4), 129.3
(Ph3,5), 128.7 (bipy4), 127.2 (CH3CN), 123.6 (bipy2), 101.8 (py3,5),
12.7 (CH3CN). 31P{1H}NMR (δ, CD3NO2, 20 °C): 101.8.
νCtN), νCdO 1944 (s, νCdO), 1982 (s, νCdO), 1855 (m, νCdO).
[Fe(PNP-Ph)(CH3CN)3](BF4)2‚3CH3CN (9a‚3CH3CN). A solu-
tion of 1a (500 mg, 1.05 mmol) and [Fe(H2O)6](BF4)2 (354 mg,
1.05 mmol) in acetonitrile (10 mL) was stirred at room temperature
for 2 h. Insoluble materials were then removed by filtration, and
the volume of the solution was reduced to about 2 mL. Upon
addition of Et2O, an orange precipitate was formed, which was
washed twice with Et2O and dried under vacuum. Yield: 805 mg
(97%). Anal. Calcd for C41H46B2F8FeN9P2: C, 51.50; H, 4.85; N,
[Fe(PNP-Ph)(terpy)](BF4)2‚CH3NO2 (14‚CH3NO2). This com-
plex was prepared analogously to 13 with 2,2′:6′,2′′-terpyridine (42
mg, 0.18 mmol) and 9a (150 mg, 0.18 mmol). Yield: 139 mg
(83%). Anal. Calcd for C45H39B2F8FeN6O2P2: C, 52.26; H, 3.98;
1
N, 8.51. Found: C, 52.41; H, 4.10; N, 8.77. H NMR (δ, CD3-
1
NO2, 20 °C): 8:38 (m, 4H, terpy1,4), 8.15 (s, 2H, NH), 7.75-7.72
(d, J ) 7.8 Hz, 3H, terpy3,7), 7.49-7.43 (t, J ) 8.1 Hz, 2H, terpy6),
7.19-7.16 (m, 4H, terpy2, py3,5), 7.05-6.99 (m, 10H, Ph), 6.89-
6.83 (m, 11H, Ph, py4). 13C{1H} NMR (δ, CD3NO2, 20 °C): 163.3
13.18. Found: C, 51.24; H, 4.66; N, 13.35. H NMR (δ, CD3CN,
20 °C): 8.36 (s, 2H, NH), 7.91-7.62 (m, 21H, Ph, py4), 6.64 (d,
J ) 8.0 Hz, 2H, py3,5), 1.97 (s, 9H, CH3CN). 13C{1H} NMR (δ,
CD3CN, 20 °C): 163.2 (t, J ) 9.8 Hz, py2,6), 141.2 (py4), 137.7

1912 Organometallics, Vol. 25, No. 8, 2006
Benito-Garagorri et al.
(py2,6), 157.6 (terpy8), 156.8 (terpy5), 152.8 (terpy1), 141.6 (py4),
136.7 (terpy3), 136.3 (terpy7), 130.6 (Ph2,6), 128.8-128.7 (Ph,4 Ph),
127.0 (Ph3,5), 123.2 (terpy4), 123.0 (terpy6), 122.0 (terpy2), 102.2
(py3,5). 31P{1H}NMR (δ, CD3NO2, 20 °C): 100.3.
After the mixture was stirred for 2 h, the solvent was removed
under vacuum and the product was precipitated with Et2O, collected
on a glass frit, and washed twice with Et2O (10 mL). Yield: 1.3 g
(95%). Anal. Calcd for C29H25Cl2N3P2Pd: C, 53.20; H, 3.85; N,
6.42. Found: C, 53.24; H, 3.57; N, 6.35. 1H NMR (δ, CD2Cl2, 20
°C): 10.47 (s, 2H, NH), 8.00-7.28 (m, 21H, Ph, py4), 6.84 (d, J
) 8.0 Hz, py3,5). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 160.6 (t, J )
7.5 Hz, py2,6), 151.1 (Ph), 142.0 (py4), 132.3 (t, J ) 7.8 Hz, Ph2,6),
130.1 (Ph4), 129.1 (t, J ) 6.0 Hz, Ph3,5), 101.7 (py3,5). 31P{1H}
NMR (δ, CD2Cl2, 20 °C): 69.9.
[Pd(PNP-Pri)Cl]Cl (18b). This complex has been prepared
analogously to 18a with [Pd(COD)Cl2] (337 mg, 1.18 mmol) and
1b (400 mg, 1.18 mmol) as the starting materials. Yield: 600 mg
(98%). Anal. Calcd for C17H33Cl2N3P2Pd: C, 39.36; H, 6.41; N,
8.10. Found: C, 38.98; H, 6.33; N, 8.25. 1H NMR (δ, CD2Cl2, 20
°C): 9.44 (s, 2H, NH), 7.20 (t, J ) 7.2 Hz, 1H, py4), 6.81 (d, J )
7.6 Hz, 2H, py3,5), 2.67-2.56 (m, J ) 6.8 Hz, 4H, CH(CH3)2),
1.44-1.32 (m, J ) 8.7 Hz, 24 H, CH(CH3)2). 13C{1H} NMR (δ,
CD2Cl2, 20 °C): 162.4 (t, J ) 6.1 Hz, py2,6), 141.1 (py4), 100.4
(py3,5), 27.3 (t, J ) 13.4 Hz, CH(CH3)2), 17.3 (CH(CH3)2). 31P-
{1H} NMR (δ, CD2Cl2, 20 °C): 108.4.
[Pd(PNP-But)Cl]Cl (18c). This complex has been prepared
analogously to 18a with [Pd(COD)Cl2] (156 mg, 0.88 mmol) and
1c (300 mg, 0.88 mmol) as the starting materials. Yield: 420 mg
(81%). Anal. Calcd for C21H41Cl2N3P2Pd: C, 43.88; H, 7.19; N,
7.31. Found: C, 43.91; H, 7.12; N, 7.35. 1H NMR (δ, CD2Cl2, 20
°C): 9.43 (s, 2H, NH), 7.16 (d, J ) 7.5 Hz, 2H, py3,5), 6.95 (t, J
) 7.2 Hz, 1H, py4), 1.55-1.49 (m, 36H, C(CH3)3). 13C{1H} NMR
(δ, CD2Cl2, 20 °C): 163.0 (t, J ) 5.8 Hz, py2,6), 140.6 (py4), 100.2
(py3,5), 39.5 (t, J ) 9.2 Hz, C(CH3)3), 28.0 (t, J ) 3.2 Hz, C(CH3)3).
31P{1H} NMR (δ, CD2Cl2): 115.7.
[Pd(PNP-ETOL)Cl]CF3SO3 (20a). KCF3SO3 (130 mg, 0.70
mmol) and [Pd(COD)Cl2] (182 mg, 0.64 mmol) were added to a
solution of 1d (185 mg, 0.64 mmol) in CH3CN. The mixture was
stirred for 2 h and filtered. The yellow filtrate was evaporated to
dryness, and the product was precipitated with Et2O, collected on
a glass frit, and washed twice with Et2O (10 mL). Yield: 282 mg
(76%). Anal. Calcd for C10H13ClF3N3O7P2PdS: C, 20.71; H, 2.26;
N, 7.24. Found: C, 20.67; H, 2.36; N, 8.05. 1H NMR (δ, CD3CN,
20 °C): 7.54 (t, J ) 8.4 Hz, 1H, py4), 6.20 (s, 2H, NH), 6.03 (d,
J ) 8.2 Hz, 2H, py3,5), 4.36-4.30 (m, 8H, CH2). 13C{1H} NMR
(δ, CD3CN, 20 °C): 151.6 (py2,6), 145.9 (py3,5), 96.3 (py4), 67.7
(CH2), 65.2 (CH2). 31P{1H} NMR (δ, CD3CN, 20 °C): 123.8.
[Pt(PNP-Pri)Br]Br (22a). To a solution of [Pt(COD)Br2] (100
mg, 0.28 mmol) in CH2Cl2 (10 mL) was added 1b (97 mg, 0.28
mmol). After the mixture was stirred for 2 h, the solvent was
removed under vacuum and the product was precipitated with Et2O,
collected on a glass frit, and washed twice with Et2O (10 mL).
Yield: 184 mg (94%). Anal. Calcd for C29H25Br2N3P2Pt: C, 41.85;
H, 3.03; N, 5.05. Found: C, 41.49; H, 3.12; N, 5.21. 1H NMR (δ,
CD2Cl2, 20 °C): 9.43 (t, J ) 15.2 Hz, 2H, NH), 7.16 (t, J ) 8.1
Hz, 1H, py4), 6.95 (d, J ) 8.0 Hz, 2H, py3,5), 2.88-2.77 (m, 4H,
CH(CH3)2), 1.41-1.34 (m, 24H, CH(CH3)2). 13C{1H} NMR (δ,
CD2Cl2, 20 °C): 161.7 (t, J ) 5.5 Hz, py2,6), 140.4 (py4), 100.0
(py3,5), 27.3 (t, J ) 17.0 Hz, CH(CH3)2), 17.2 (d, J ) 9.2 Hz, CH-
(CH3)2). 31P{1H} NMR (δ, CD2Cl2, 20 °C): 100.4 (t, JPtP ) 1273
Hz).
[Pt(PNP-But)Br]Br (22b). This complex has been prepared
analogously to 22a with [Pt(COD)Br2] (100 mg, 0.28 mmol) and
1c (112 mg, 0.28 mmol) as the starting materials. Yield: 180 mg
(85%). Anal. Calcd for C21H41Br2N3P2Pt: C, 33.52; H, 5.49; N,
5.58. Found: C, 33.24; H, 5.42; N, 5.39. 1H NMR (δ, CD2Cl2, 20
°C): 9.21 (t, J ) 16.8 Hz, 2H, NH), 7.42 (t, J ) 7.8 Hz, 1H, py4),
6.95 (m, 2H, py3,5), 1.57-1.51 (m, 36H, C(CH3)3). 13C{1H} NMR
(δ, CD2Cl2, 20 °C): 162.0 (py2,6), 140.2 (py4), 100.5 (py3,5), 40.4
(t, J ) 12.4 Hz, C(CH3)3), 28.6 (C(CH3)3). 31P{1H} NMR (δ, CD2-
Cl2, 20 °C): 103.9 (t, JPtP ) 1267 Hz).
[Fe(PNP-Ph)2](BF4)2 (15). [Fe(H2O)6](BF4)2 (300 mg, 0.90
mmol) was added to a solution of 1a (848 mg, 1.80 mmol) in THF,
whereupon the color of the solution turned purple. After the mixture
was stirred at room temperature for 2 h, the solvent was evaporated
in a vacuum. The solid was precipitated, washed twice with Et2O,
and evaporated to dryness, yielding 960 mg (90%) of a purple solid.
Anal. Calcd for C58H50B2F8FeN6P4: C, 58.82; H, 4.25; N, 7.10.
Found: C, 59.04; H, 4.31; N, 6.98. 1H NMR (δ, CD3NO2, 20 °C):
7.98-7.92 (t, J ) 8.0 Hz, 2H, py4), 7.25-6.48 (m, 46H, Ph, py3,5
,
NH). 13C{1H} NMR (δ, CD3NO2, 20 °C): 163.0 (py2,6), 142.1 (py4),
136.8 (Ph), 129.9 (Ph2,6), 129.1 (Ph4), 128.8 (Ph3,5), 101.6 (py3,5).
31P{1H} NMR (δ, CD3NO2, 20 °C): 92.0.
Ru(PNP-Ph)(PPh3)Cl2 (16a). A solution of 1a (224 mg, 0.47
mmol) and [RuCl2(PPh3)3] (450 mg, 0.47 mmol) in CH2Cl2 (6 mL)
was stirred at room temperature for 2 h. The volume of the solution
was reduced to about 1 mL. Upon addition of Et2O, a light brown
precipitate was formed, which was washed twice with Et2O and
dried under vacuum. Yield: 350 mg (82%). Anal. Calcd for C47H40-
Cl2N3P3Ru: C, 61.92; H, 4.42; N, 4.61. Found: C, 62.09; H, 4.54;
1
N, 4.70. H NMR (δ, CD2Cl2, 20 °C): 7.50-6.35 (m, 31H, Ph,
py2), 6.41 (d, J ) 7.5 Hz, 2H, py1,3), 5.95 (s, 2H, NH). 13C{1H}
NMR (δ, CD2Cl2, 20 °C): 159.2 (t, J ) 7.4 Hz, py2,6), 138.6 (py4),
137.7 (d, J ) 39.5 Hz, PPh1 ), 135.3 (t, JCP ) 23.0 Hz, PNP-
3
Ph1), 134.8 (d, J ) 9.2 Hz, PPh2,63), 133.4 (t, J ) 5.5 Hz, PNP-
Ph2,6), 129.6 (PNP-Ph4), 128.6 (d, JCP ) 1.8 Hz, PPh4 ), 127.2 (t,
3
J ) 4.6 Hz, PNP-Ph3,5), 126.8 (d, J ) 8.5 Hz, PPh3,53), 98.5 (py3,5).
31P{1H} NMR (δ, CD2Cl2, 20 °C): 83.7 (d, J ) 27.7 Hz, PNP),
38.2 (t, JPP ) 27.7 Hz, PPh3).
[Ni(PNP-Ph)Br]Br (17a). To a solution of 1a (463 mg, 0.97
mmol) in CH2Cl2 (10 mL) was added [NiBr2(DME)] (300 mg, 0.97
mmol), and the mixture was stirred overnight at room temperature,
whereupon an orange solid precipitated, which was collected on a
glass frit, washed twice with Et2O, and dried under vacuum.
Yield: 620 mg (94%). Anal. Calcd for C29H25Br2N3NiP2: C, 50.05;
1
H, 3.62; N, 6.04. Found: C, 50.24; H, 4.16; N, 10.35. H NMR
(δ, CD3OD, 20 °C): 7.89-7.48 (m, 21H, Ph, py4), 6.41 (d, J )
8.0 Hz, 2H, py3,5), 3.30 (s, 2H, NH). 13C{1H} NMR (δ, CD3OD,
20 °C): 161.6 (py2,6), 145.3 (Ph), 143.6 (py4), 132.5 (Ph2,6), 132.3
(Ph4), 128.8 (Ph3,5), 99.7 (py3,5). 31P{1H} NMR (δ, CD3OD, 20
°C): 66.1.
[Ni(PNP-Pri)Br]Br (17b). This complex has been prepared
analogously to 17a with NiBr2(DME) (271 mg, 0.88 mmol) and
1b (300 mg, 0.88 mmol) as the starting materials. Yield: 450 mg
(81%). Anal. Calcd for C17H33Br2N3NiP2: C, 36.47; H, 5.94; N,
7.50. Found: C, 36.24; H, 5.17; N, 7.25. 1H NMR (δ, CD3OD, 20
°C): 7.54 (t, J ) 8.0 Hz, 1H, py4), 6.32 (d, J ) 8.0 Hz, 2H, py3,5),
3.30 (s, 2H, NH), 2.51-2.46 (m, 4H, CH(CH3)2), 1.53-1.36 (m,
24 H, CH(CH3)2). 13C{1H} NMR (δ, CD3OD, 20 °C): 161.8 (t, J
) 8.9 Hz, py2,6), 141.7 (py4), 97.4 (py3,5), 24.9 (t, J ) 13.7 Hz,
CH(CH3)2), 14.2 (CH(CH3)2). 31P{1H} NMR (δ, CD3OD, 20 °C):
100.6.
[Ni(PNP-But)Br]Br (17c). This complex has been prepared
analogously to 17a with NiBr2(DME) (233 mg, 0.75 mmol) and
1c (300 mg, 0.75 mmol) as the starting materials. Yield: 440 mg
(72%). Anal. Calcd for C21H41Br2N3NiP2: C, 40.94; H, 6.71; N,
6.82. Found: C, 40.74; H, 6.89; N, 6.77. 1H NMR (δ, CD3OD, 20
°C): 7.51 (t, J ) 8.1 Hz, 1H, py4) 6.36 (d, J ) 7.9 Hz, 2H, py3,5),
3.30 (s, 2H, NH), 1.59-1.52 (m, 36H, C(CH3)3). 13C{1H} NMR
(δ, CD3OD, 20 °C): 163.4 (py2,6), 143.0 (py4), 98.5 (py3,5), 39.3
(t, J ) 9.2 Hz, C(CH3)3), 27.3 (C(CH3)3). 31P{1H} NMR (δ, CD3-
OD, 20 °C): 103.7.
[Pd(PNP-Ph)Cl]Cl (18a). To a solution of [Pd(COD)Cl2] (0.6
g, 2.1 mmol) in CH2Cl2 (10 mL) was added 1a (1.0 g, 2.1 mmol).

Transition Metal Complexes with PNP Pincer Ligands
Organometallics, Vol. 25, No. 8, 2006 1913
X-ray Structure Determination. X-ray data for 4a‚CH3CN, 4b‚
CH3CN, 7b, 8, 9a‚3CH3CN, 9b‚solv, 9d‚solv, 9f, 11‚3ClCH2CH2-
Cl‚H2O, 12‚CH3CN, 13‚solv, 14‚solv, 15, 16d‚2CH2Cl2, 17a‚solv,
17c‚CH3OH, 18c‚2CH2Cl2, and 20b‚(C2H5)2O‚2CH3CN were col-
lected 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 complete spheres of the reciprocal
space. Corrections for absorption, λ/2 effects, and crystal decay
were applied.28 The structures were solved by direct methods using
the program SHELXS97.29 Structure refinement on F2 was carried
out with the program SHELXL97.18 All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were inserted in idealized
positions and were refined riding on the atoms to which they were
bonded, using AFIX 137 orientation refinement for acetonitrile CH3
groups. Badly disordered solvents were squeezed with the program
PLATON prior to final refinement.30 Further details including
atomic parameters are given in the CIFs of the structures, which
have been deposited as Supporting Information. Moreover, basic
crystallographic data are given in Tables S1, S2, and S3 in the
Supporting Information.
Acknowledgment. Financial support by the “Fonds zur
Fo¨rderung der Wissenschaftlichen Forschung” is gratefully
acknowledged (Project No. P16600-N11). D.B.-G. thanks the
Basque Government (Eusko Jaurlaritza/Gobierno Vasco) for a
doctoral fellowship.
Supporting Information Available: Synthesis and spectro-
scopic data of N,N′-di-10-undecenyl-2,6-diaminopyridine, N,N′-
dihexyl-2,6-diaminopyridine, 4c, 5, 6, 7c, 9b, 9c, 9e, 9f, 10a, 10b,
11, 16b-f, 19a, 19b, 20b-e, 21a, 21b, 23a, and 23b. Complete
crystallographic data and technical details in tabular and in CIF
format for 4a‚CH3CN, 4b‚CH3CN, 7b, 8, 9a‚3CH3CN, 9b‚solv,
9d‚solv, 9f, 11‚3ClCH2CH2Cl‚H2O, 12‚CH3CN, 13‚solv, 14‚solv,
15, 16d‚2CH2Cl2, 17a‚solv, 17c‚CH3OH, 18c‚2CH2Cl2, and 20b‚
(C2H5)2O‚2CH3CN. This material is available free of charge via
the Internet at http://pubs.acs.org.
(28) Bruker programs: SMART, version 5.054; SAINT, version 6.2.9;
SADABS, version 2.10; XPREP, version 5.1; SHELXTL, version 5.1; Bruker
AXS Inc.: Madison, WI, 2001.
(29) Sheldrick, G. M. SHELX97: Program System for Crystal Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(30) Spek, A. L. PLATON: A Multipurpose Crystallographic Tool;
University of Utrecht: Utrecht, The Netherlands, 2004.
OM0600644