New pyridyl modified phosphines: Synthesis and late transition-metal coordination studies

Article abstract of DOI:10.1016/j.ica.2005.12.068

Using a phosphorus based Mannich condensation reaction the new pyridylphosphines {5-Ph₂PCH₂N(H)}C₅H₃(2-Cl)N (1-Cl) and {2-Ph₂PCH₂N(H)}C₅H₃(5-Br)N (1-Br) have been synt

Full text of DOI:10.1016/j.ica.2005.12.068

Inorganica Chimica Acta 359 (2006) 2980–2988
www.elsevier.com/locate/ica
New pyridyl modified phosphines: Synthesis and late
transition-metal coordination studies
a
a,
b
c
Sean E. Durran , Martin B. Smith *, Sophie H. Dale , Simon J. Coles ,
c
c
Michael B. Hursthouse , Mark E. Light
a
Department of Chemistry, Loughborough University, Loughborough, Leics, LE11 3TU, UK
School of Natural Sciences (Chemistry), Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK
EPSRC X-ray Crystallography Service, Department of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
b
c
Received 24 November 2005; accepted 31 December 2005
Available online 23 February 2006
This article is dedicated to Brian James on the special occasion of his 70th birthday. His enthusiasm for pyridylphosphine
chemistry prompted much of our ongoing work in this field.
Abstract
Using a phosphorus based Mannich condensation reaction the new pyridylphosphines {5-Ph2PCH2N(H)}C5H3(2-Cl)N (1-Cl) and {2-
Ph2PCH2N(H)}C5H3(5-Br)N (1-Br) have been synthesised in good yields (60% and 88%, respectively) from Ph2PCH2OH and the appro-
priate aminopyridine. The ligands 1-Cl and 1-Br display variable coordination modes depending on the choice of late transition-metal
complex used. Hence P-monodentate coordination has been observed for the mononuclear complexes AuCl(1-Cl) (2), AuCl(1-Br) (3),
RuCl2(p-cymene)(1-Cl) (4), RuCl2(p-cymene)(1-Br) (5), RhCl2(Cp*)(1-Cl) (6), RhCl2(Cp*)(1-Br) (7), IrCl2(Cp*)(1-Cl) (8),
IrCl2(Cp*)(10-Cl) (80), IrCl2(Cp*)(1-Br) (9), cis-/trans-PdCl2(1-Cl)2 (10), cis-/trans-PdCl2(1-Br)2 (11), cis-PtCl2(1-Cl)2 (12) and cis-
PtCl2(1-Br)2 (13). Reaction of Pd(Me)Cl(cod) (cod = cycloocta-1,5-diene) with either 1 equiv. of 1-Br or the known pyridylphosphines
10-Cl, 1-OH or 1-H gave the P/N-chelate complexes Pd(Me)Cl(1-Br–1-H) (14)–(17). All new compounds have been fully characterised by
spectroscopic and analytical methods. Furthermore the structures of 4, 5, 10 and 16 Æ (CH3)2SO have been elucidated by single crystal
X-ray crystallography. A crystal structure of the dinuclear metallocycle trans,trans-[PdCl2{l-P/N-{Ph2PCH2N(H)}C5H4N}]2 Æ CHCl3,
18 Æ CHCl3, has also been determined. Here 1-H bridges, using both P and pyridyl N donors, two dichloropalladium centres affording
a 12-membered ring with the PdCl2 units adopting a head-to-tail arrangement.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Phosphines; Transition-metals; X-ray crystallography; Multinuclear NMR; Chelate complexes; Bridging ligands
1. Introduction
and polynuclear compounds [3b] and have catalytic applica-
tions [4]. Recent work, using classical synthetic procedures in
phosphorus chemistry [5], has shown that numerous other
new pyridylphosphines [6–17] can be synthesised. These
include PN-bidentate [6], mixed OPN- [7], PNP- [8], CNP-
terdentate [9], chiral [10], phosphine oxide [11], and sulfide
[12] based pyridyl modified ligands. James and co-workers
[18] have made important contributions in this field with
the synthesis of new bis(pyridylphosphines), and further-
more demonstrated a range of coordination modes for this
novel ligand class. More recently this group have also inves-
tigated related ortho-N,N-dimethylanilinyl functionalised
Pyridylphosphines are an important class of functional-
ised phosphine containing both P- and N-donor centres [1].
Many studies [2] have focused on simple pyridylphosphines
most notably Ph2PPy, PhPPy2 and PPy3 (Py = 2-pyridyl).
These phosphines have been shown to display various coor-
dination modes [2], serve as useful building blocks for di- [3a]
*
Corresponding author. Tel.: +44 0 1509 222553; fax: +44 0 1509
223925.
E-mail address: m.b.smith@lboro.ac.uk (M.B. Smith).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.068

S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
2981
phosphines and shown that they can support homobimetal-
lic and heterobimetallic complexes [19].
similar manner (88%). For 1-Cl, C18H16N2PCl requires:
C, 66.15; H, 4.95; N, 8.57. Found: C, 66.09; H, 4.89; N,
8.27%. For 1-Br, C18H16N2PBr requires: C, 58.23; H,
4.35; N, 7.55. Found: C, 58.44; H, 4.22; N, 7.09%.
We describe here the synthesis of two new pyridylphos-
phines from
a simple condensation reaction using
Ph2PCH2OH. This methodology has proven extremely ver-
satile in the past and we have applied this approach to the
synthesis of a range of hybrid phosphines [20–25]. Further-
more we also show that a rich coordination chemistry
exists with these new pyridylphosphine ligands including
P-monodentate, P/N-chelate and P/N-bridging modes.
All new compounds have been verified by spectroscopic
and X-ray crystallographic techniques.
2.3.2. Preparation of 2 and 3
To a stirred solution of AuCl(tht) (0.059 g, 0.184 mmol)
in CH2Cl2 (10 ml) was added 1-Cl (0.060 g, 0.184 mmol) as
a solid in one portion. After stirring the solution for ca.
15 min the volume was concentrated in vacuo to 1–2 ml
and petroleum ether (60–80 ꢁC, 15 ml) added. The white
solid 2 was collected by suction filtration and dried in
vacuo. Yield: 0.072 g, 70%. The gold(I) compound
AuCl{{2-Ph2PCH2N(H)}C5H3(5-Br)N} (3) was prepared
in a similar manner (87%). For 2, C18H16N2PAuCl2
requires: C, 38.66; H, 2.88; N, 5.01. Found: C, 38.80; H,
3.10; N, 4.90%. For 3, C18H16N2PBrAuCl Æ 0.5CH2Cl2
requires: C, 34.40; H, 2.65; N, 4.34. Found: C, 35.00; H,
2.70; N, 4.40%.
2. Experimental
2.1. Materials
Standard Schlenk techniques were used for the synthesis
of 1-Cl and 1-Br whilst all other reactions were carried out
in air using previously distilled solvents unless otherwise sta-
ted. The ligands 10-Cl, 1-OH and 1-H have been reported
elsewhere [20,21] and the metal complexes AuCl(tht)
(tht = tetrahydrothiophene) [26], {RuCl2(p-cymene)}2 [27],
{MCl2(Cp*)}2 (M = Rh, Ir; Cp* = 1,2,3,4,5-pentamethylcy-
clopentadienyl) [28], MCl2(cod) (M = Pd, Pt) [29,30] and
Pd(Me)Cl(cod) [31] were prepared according to known pro-
cedures. All other chemicals were obtained from commercial
suppliers and used directly without further purification.
2.3.3. Preparation of 4–9
An illustrative example is given here for RhCl2(Cp*){{5-
Ph2PCH2N(H)}C5H3(2-Cl)N} (6). To a stirred solution of
{RhCl2(Cp*)}2 (0.088 g, 0.142 mmol) in CH2Cl2 (10 ml)
was added 1-Cl (0.094 g, 0.288 mmol) as a solid in one por-
tion. After stirring the solution for ca. 15 min the volume
was concentrated in vacuo to 1–2 ml and diethyl ether
(15 ml) added. The red/orange solid was collected by suction
filtration and dried in vacuo. Yield: 0.165 g, 90%. The rho-
dium(III) compound RhCl2(Cp*){{2-Ph2PCH2N(H)}-
C5H3(5-Br)N} (7) was prepared in a similar manner (77%).
The iridum(III) analogues IrCl2(Cp*){{5-Ph2PCH2N(H)}-
C5H3(2-Cl)N} (8), IrCl2(Cp*){{2-Ph2PCH2N(H)}C5H3
(5-Cl)N} (80) and IrCl2(Cp*){{2-Ph2PCH2N(H)}C5H3
(5-Br)N} (9) were likewise prepared in 88%, 77% and 82%
yields, respectively. The ruthenium(II) complexes RuCl2-
(Cp*){{5-Ph2PCH2N(H)}C5H3(2-Cl)N} (4) (88%) and
RuCl2(Cp*){{2-Ph2PCH2N(H)}C5H3(5-Br)N} (5) (89%)
have also been prepared by bridge cleavage of the dimer
{RuCl2(p-cymene)}2 with either 1-Cl or 1-Br. For 4,
C28H30N2PRuCl3 Æ CHCl3 requires: C, 45.50; H, 4.10; N,
3.72. Found: C, 45.61; H, 4.01; N, 3.02%. For 5,
C28H30N2PRuBrCl2 requires: C, 49.65; H, 4.46; N, 4.14.
Found: C, 49.10; H, 4.37; N, 3.75%. For 6, C28H31N2PRhCl3
requires: C, 52.89; H, 4.92; N, 4.41. Found: C, 52.40; H, 4.78;
N, 4.13%. For 7, C28H31N2PRhBrCl2 Æ 0.5CH2Cl2 requires:
C, 48.13; H, 4.49; N, 3.85. Found: C, 48.27; H, 4.40; N,
4.21%. For 8, C28H31N2PIrCl3 requires: C, 46.37; H, 4.32;
N, 3.86. Found: C, 46.26; H, 4.22; N, 3.78%. For 80,
C28H31N2PIrCl3 requires: C, 46.37; H, 4.32; N, 3.86. Found:
C, 45.84; H, 4.32; N, 3.86%. For 9, C28H31N2PIrBrCl2
requires: C, 43.69; H, 4.07; N, 3.64. Found: C, 43.27; H,
3.84; N, 3.16%.
2.2. Instrumentation
Infrared spectra were recorded as KBr pellets in the range
4000–200 cmꢀ1 on a Perkin–Elmer System 2000 Fourier-
transform spectrometer, 1H NMR spectra (250 or
400 MHz) on Bruker AC250 FT or DPX-400 FT spectrom-
eters with chemical shifts (d) in ppm to high frequency of
SiMe4 and coupling constants (J) in Hz, 31P{1H} NMR
spectra were recorded on JEOL FX90Q or Bruker DPX-
400 FT spectrometers with chemical shifts (d) in ppm to high
frequency of 85% H3PO4. All NMR spectra were measured
in CDCl3 unless otherwise stated. Elemental analyses
(Perkin–Elmer 2400 CHN Elemental Analyzer) were per-
formed by the Loughborough University Analytical Service
within the Department of Chemistry.
2.3. Syntheses
2.3.1. Preparation of 1-Cl
A mixture of Ph2PCH2OH (0.895 g, 4.14 mmol) and 5-
H2NC5H3(2-Cl)N (0.531 g, 4.13 mmol) in methanol
(15 ml) and toluene (25 ml) was refluxed under a nitrogen
atmosphere for ca. 6 d. The volume was reduced to 3–
4 ml whereupon a white solid deposited. After the addition
of diethyl ether (10 ml) the solid was collected by suction
filtration, washed with cold methanol (5 ml) and dried
in vacuo. Yield: 0.806 g, 60%. The bromo compound
{2-Ph2PCH2N(H)}C5H3(5-Br)N (1-Br) was prepared in a
2.3.4. Preparation of 10 and 11
To a stirred solution of PdCl2(cod) (0.040 g, 0.140 mmol)
in CH2Cl2 (10 ml) was added 1-Cl (0.091 g, 0.281 mmol) in

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S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
one portion. After stirring the solution for ca. 15 min the
volume was concentrated in vacuo to 1–2 ml and petroleum
ether (60–80 ꢁC, 15 ml) added. The yellow solid 10 was col-
lected by suction filtration and dried in vacuo. Yield:
0.095 g, 82%. The dichloropalladium compound PdCl2-
{{2-Ph2PCH2N(H)}C5H3(5-Br)N}2 (11) was prepared in a
similar manner (77%). For 10, C36H32N4P2PdCl4 requires:
C, 52.00; H, 3.90; N, 6.70. Found: C, 52.40; H, 4.10; N,
6.64%. For 11, C36H32N4P2PdBr2Cl2 requires: C, 47.00;
H, 3.50; N, 6.10. Found: C, 46.90; H, 3.80; N, 5.90%.
was collected by suction filtration and dried in vacuo. Yield:
0.126 g, 93%. The palladium compounds 15 (93%), 16 (82%)
and 17 (93%) were also synthesised. For 14, C19H19N2P-
BrClPd requires: C, 43.21; H, 3.63; N, 5.31. Found: C,
42.85; H, 3.41; N, 5.34%. For 15, C19H19N2PCl2Pd requires:
C, 47.18; H, 3.97; N, 5.79. Found: C, 46.59; H, 3.73; N,
5.60%. For 16, C19H20N2OPClPd requires: C, 49.05; H,
4.34; N, 6.02. Found: C, 48.53; H, 4.11; N, 6.12%. For 17,
C19H20N2PClPd requires: C, 50.79; H, 4.50; N, 6.24. Found:
C, 50.10; H, 4.26; N, 6.06%.
2.4. X-ray crystallography
2.3.5. Preparation of 12 and 13
To a stirred solution of PtCl2(cod) (0.060 g, 0.160 mmol)
in CH2Cl2 (10 ml) was added 1-Cl (0.105 g, 0.321 mmol) in
one portion. After stirring the solution for ca. 15 min the
volume was concentrated in vacuo to 1–2 ml and diethyl
ether (15 ml) added. The white solid 12 was collected by
suction filtration and dried in vacuo. Yield: 0.124 g, 84%.
The dichloroplatinum compound PtCl2{{2-Ph2PCH2
-N(H)}C5H3(5-Br)N}2 (13) was prepared in a similar man-
ner (89%). For 12, C36H32N4P2PtCl4 Æ 0.5CH2Cl2 requires:
C, 45.57; H, 3.46; N, 5.82. Found: C, 46.00; H, 3.88; N,
5.22%. For 13, C36H32N4P2PtBr2Cl2 requires: C, 42.87;
H, 3.20; N, 5.56. Found: C, 43.18; H, 3.30; N, 5.11%.
The compounds 4, 5 and 10 were obtained by vapour dif-
fusion of Et2O into either CDCl3 or CH2Cl2 solutions over
several days. Compound 16 Æ (CH3)2SO was obtained by
slow diffusion of Et2O into a CDCl3/dmso solution. A few
X-ray quality crystals of 18 Æ CHCl3 were obtained by slow
diffusion of Et2O into a CDCl3/dmso solution of 17 over an
extended period. Data were recorded at 120 K (or 150 K for
16 Æ (CH3)2SO), using a Nonius Kappa CCD area-detector
diffractometer mounted at the window of a rotating anode
˚
FR591 generator with a molybdenum anode (0.71073 A).
u and x scans (2ꢁ increments) were carried out to fill the
Ewald sphere. Data collection and processing were carried
out using the programs DIRDIF, DIRAX, COLLECT and DENZO
and an empirical absorption correction was applied using
SORTAV [32]. The structures were solved by direct methods
and refined on F2 values for all unique data by full-matrix
least-squares. Table 1 gives further details. All non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms
except NH were placed in calculated positions and refined
using a riding model [Uiso(H) = 1.2Ueq(C,N) for aryl,
2.3.6. Preparation of 14–17
Preparation of Pd(Me)Cl{{2-Ph2PCH2N(H)}C5H3(5-
Br)N} (14). To a stirred solution of Pd(Me)Cl(cod) (0.068
g, 0.256 mmol) in CH2Cl2 (10 ml) was added 1-Br (0.095 g,
0.256 mmol) as a solid in one portion. After stirring the solu-
tion for ca. 15 min the volume was concentrated in vacuo to
1–2 ml and diethyl ether (15 ml) added. The pale yellow solid
Table 1
Crystallographic data for 4, 5, 10, 16 Æ (CH3)2SO and 18 Æ CHCl3
Compound
4
5
10
16 Æ (CH3)2SO
18 Æ CHCl3
Empirical formula
Formula weight
Crystal system
Space group
C28H30Cl3N2PRu
632.93
triclinic
C28H30BrCl2N2PRu
677.39
triclinic
C36H32Cl4N4P2Pd
830.80
monoclinic
C2/c
28.989(6)
10.663(2)
23.718(5)
C21H26ClN2O2PPdS
543.32
triclinic
C19H18Cl5N2PPd
588.97
triclinic
ꢀ
ꢀ
ꢀ
ꢀ
P1
P1
P1
P1
˚
a (A)
7.5918(15)
10.300(2)
18.188(4)
78.77(3)
87.76(3)
69.93(3)
7.6637(15)
10.391(2)
18.072(4)
79.07(3)
86.31(3)
69.52(3)
9.1177(18)
10.762(2)
12.624(3)
100.16(3)
106.78(3)
101.56(3)
1125.1(5)
2
9.7546(3)
10.2608(3)
12.8523(4)
95.519(1)
104.740(1)
114.268(2)
1104.33(6)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
101.75(3)
3
˚
Volume (A )
1309.7(5)
2
1323.7(6)
2
7178(2)
8
Z
T (K)
120(2)
1.605
0.987
block; orange
0.04 · 0.05 · 0.08
2.93–27.40
17877
120(2)
1.700
2.385
plate; orange
0.08 · 0.12 · 0.30
2.98–27.47
17292
120(2)
1.538
0.937
needle; yellow
0.02 · 0.04 · 0.24
3.04–27.50
30408
150(2)
1.604
1.127
block; colourless
0.08 · 0.10 · 0.14
1.99–27.50
16994
120(2)
1.771
1.527
block; yellow
0.10 · 0.20 · 0.30
3.09–25.02
8364
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
Crystal
)
Crystal size (mm3)
h Range (ꢁ)
Reflections collected
Independent reflections [Rint
]
5741 [0.098]
0.052, 0.109
5800 [0.071]
0.038, 0.097
8017 [0.091]
0.046, 0.096
5040 [0.044]
0.030, 0.074
3760 [0.070]
0.036, 0.096
Final R1 (F2 > 2r(F2))a, wR2 (all data)b
P
P
a
R = iFo| ꢀ |Fci/ |Fo|.
P
P
2
2 1=2
b
wR2 ¼ ½ ½wðF 2o ꢀ F c2Þ ꢁ= ½wðF 2oÞ ꢁꢁ
.

S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
2983
+
Cl
methine, methylene and NH hydrogen atoms; Uiso(H) =
1.5Ueq(C,O) for methyl and hydroxy hydrogen atoms;
Uiso(NH) freely refined in 10]. NH hydrogen atoms were
located in a difference Fourier map, and in compounds 4,
5, 16 Æ (CH3)2SO and 18 Æ CHCl3, their positions were
refined using distance restraints [target N–H bond length =
vii
Ru
Ru
Cl
P
Cl
L
Cl
N
L
L = 1-Br 5`
L = 1-Cl
L = 1-Br
4
5
M
Cl
L
Cl
˚
0.88 A]. Programs used were Bruker SHELXTL for structure
L = 1-Cl, M = Rh 6
L = 1-Br, M = Rh 7
solution and refinement, Diamond for molecular graphics,
and local programs [33–38].
Cl
Au L
ii
L = 1-Cl
L = 1-Br
2
3
iii
iv
L = 1-Cl, M = Ir
L = 1`-Cl, M = Ir 8`
L = 1-Br, M = Ir
8
i
L = 1-Cl
L = 1-Br
9
3. Results and discussion
vi
P
Me
Cl
v
L
Pd
Cl
Cl
L
L
Cl
L
L
3.1. Ligand syntheses
Pd
N
Pd
Cl
Cl
L
L
Cl
L = 1-Br 14
L = 1`-Cl 15
L = 1-OH 16
Pt
L = 1-Cl
10
Using an established method [20–25] for C–N bond for-
mation the new ligands 1-Cl and 1-Br were synthesised, as
colourless solids, by condensation of Ph2PCH2OH with
either 5-amino-2-chloropyridine or 2-amino-5-bromopy-
ridine in MeOH/toluene under refluxing conditions
(Scheme 1). The isomeric ligand 10-Cl has previously been
reported [21] in our group along with 1-OH [20] and
1-H. Both 1-Cl and 1-Br display a characteristic phospho-
rus resonance at around d(P) ꢀ19 ppm (in CDCl3) shifted
upfield by ca. 9 ppm with respect to that observed for
Ph2PCH2OH [ꢀ9.9 ppm in CDCl3]. Solutions of 1-Cl and
1-Br showed evidence for oxidation when left exposed in
L = 1-Br 11
L = 1-Cl
12
L = 1-H
17
L = 1-Br 13
Scheme 2. (i) AuCl(tht); (ii) {RuCl2(p-cymene)}2; (iii) {MCl2(Cp*)}2
(M = Rh, Ir); (iv) PdCl2(cod); (v) PtCl2(cod); (vi) Pd(Me)Cl(cod); (vii) r.t.,
CDCl3.
onances were observed in comparison to the free ligands
1-Cl and 1-Br. Hence for 2 and 3 single d(P) resonances
at 25.7 and 27.1 ppm were observed (Table 2) whilst the
platinum(II) complexes 12 [d(P) 6.2 ppm] and 13 [d(P)
1
7.6 ppm] showed additional J(PtP) coupling constants of
1
ca. 3700 Hz indicative of a cis arrangement of pyridylphos-
phine ligands [20]. The palladium complexes 10 [d(P) 26.0,
14.0 ppm] and 11 [d(P) 29.8, 15.4 ppm], in CDCl3 solution,
exist as a mixture of cis and trans isomers whilst, in the
solid state, only the cis isomer was observed as confirmed
by IR spectroscopy (mPdCl 308 and 284 cmꢀ1 for 10; 319
and 281ꢀ1 for 11).
Bridge cleavage reactions of Ru, Rh and Ir dimers
[2c,20] have been shown to be an excellent method for
synthesising piano-stool half sandwich complexes. Accord-
ingly when 1-Cl or 1-Br were reacted with {RuCl2(p-cym-
ene)}2 or {MCl2(Cp*)}2 (M = Rh, Ir) the new ruthenium
(4, 5), rhodium (6, 7) and iridium (8, 9) complexes were iso-
lated as orange solids (Scheme 2). Characterising data for
these new compounds are given in Table 2. The 31P{1H}
NMR data implies only P-coordination to the metal centre
as indicated by the downfield shifts. We have previously
shown that related ligands (10-Cl, 1-OH and 1-H) can
undergo P/N-chelation either upon standing at room
air for periods up to 5 d. The H NMR spectra confirmed
only mono substitution since a broad NH resonance was
observed at 4.61 ppm (for 1-Cl) and 4.52 ppm (for 1-Br).
1
In addition the H NMR spectra showed a resonance at
3.80 (for 1-Cl) and 4.04 (for 1-Br) ppm assigned to the
methylene protons. Characteristic weakly absorbing
stretching vibrations of mNH in addition to mCN(pyridyl)
were observed around 3200 and 1590 cmꢀ1, respectively.
Selected microanalytical data can be found in Section 2.
3.2. Coordination studies
In order to probe the coordination chemistry of the new
pyridylphosphines 1-Cl and 1-Br we explored their reactiv-
ity towards various late transition-metals. Ligand displace-
ment of tht from AuCl(tht) or cod from MCl2(cod)
(M = Pd, Pt) in CH2Cl2 at ambient temperature gave the
gold (2, 3), palladium (10, 11) and platinum (12, 13) com-
plexes in 70–89% (Scheme 2). In all cases downfield 31P res-
PPh2
HN
PPh2
HN
PPh2
N
HN
i
ii
N
Ph2PCH2OH
X
N
X = Cl 1`-Cl
X = OH 1-OH
Cl
Br
X = H
1-H
1-Br
1-Cl
Scheme 1. (i) 2-H2NC5H3(5-Br)N, CH3OH/C7H8; (ii) 5-H2NC5H3(2-Cl)N, CH3OH/C7H8.

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S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
Table 2
Selected spectroscopic data for 1-Cl, 1-Br and 2–17
31P (ppm)
1H (ppm)
mNH
mCN
mMCl
m/z
a
Compound
1-Cl
1-Br
ꢀ19.3
ꢀ18.1
25.7
27.1
19.7
19.3d
7.75–6.89 (arom. H); 4.61 (NH); 3.80 (CH2)
8.11–6.28 (arom. H); 4.52 (NH); 4.04 (CH2)
7.74–6.97 (arom. H); 4.24 (CH2)b
8.05–6.37 (arom. H); 4.87 (NH); 4.63 (CH2)
7.89–6.46 (arom. H); 4.82 (NH); 4.44 (CH2)c
7.86–5.94 (arom. H); 5.60 (NH); 4.74 (CH2)c
7.96–6.61 (arom. H); 5.37 (NH); 4.52 (CH2); 1.39
3J(PH) 3.5 (C5Me5)
3234, 3152
3217, 3123
3322
3245
3251
1590
1585
1586
1591
1576
1590
1578
327 (M)
371 (M)
559 (M)
604 (M)
2
3
4
5
6
318
323
3255
3272
643 (M–Cl)
24.5 (146)
7
24.4 (145)
ꢀ6.3
7.89–6.09 (arom. H); 6.14 (NH); 4.85 (CH2); 1.39
3J(PH) 3.5 (C5Me5)
7.84–6.62 (arom. H); 5.40 (NH); 4.60 (CH2); 1.39
3J(PH) 2.0 (C5Me5)
7.82–6.13 (arom. H); 6.10 (NH); 4.98 (CH2); 1.39
3J(PH) 4.0 (C5Me5)
7.78–6.10 (arom. H); 5.09 (NH); 4.98 (CH2); 1.39
3J(PH) 2.4 (C5Me5)
3278
3286
3294
3293
1592
1577
1595
1591
8
725 (M)
80
9
ꢀ6.5e
690 (M–Cl)
734 (M–Cl)
ꢀ6.5f
10
11
12
13
14
26.0, 14.0g,h
29.8, 15.4h
6.2 (3699)
7.6 (3678)
35.4g
7.75–6.68 (arom. H); 4.83 (NH); 4.30 (CH2)
8.00–6.16 (arom. H); 5.60 (NH); 4.69 (CH2)
7.52–6.67 (arom. H); 4.95 (NH); 4.23 (CH2)
7.94–6.52 (arom. H); 5.95 (NH); 4.66 (CH2)
9.32–6.69 (arom. H); 7.86 (NH); 4.11 (CH2); 0.51,
3J(PH) 2.8 (Pd–CH3)
3316
3331, 3207
3324
3371, 3322
3265
1585
1590
1585
1590
1603
308, 284
319, 281
312, 288
311, 284
493 (M–Cl)
448 (M–Cl)
429 (M–Cl)
15
16
17
a
35.4g
33.7g
35.5g
9.25–6.70 (arom. H); 7.84 (NH); 4.11 (CH2); 0.51,
3J(PH) 2.8 (Pd–CH3)
3264
1609
1617
1614
10.50 (OH); 8.78-6.48 (arom. H); 6.93 (NH); 4.11
(CH2); 0.55, 3J(PH) 2.8 (Pd–CH3)
3366, 3198, 3150i
3260
3
9.16–6.51 (arom. H); 4.03 (CH2); 0.47, J(PH) 2.8
(Pd–CH3)
M = Au, Pd or Pt.
b
c
d
e
f
NH resonance not observed.
p-Cymene resonances at 5.30–5.19, 2.58, 1.89, 0.92 (for 4) and 5.27–5.20, 2.56, 1.87, 0.94 (for 5).
After ca. 30 d ratio of 5:50 was 3.5:1.
After ca. 20 d ratio of 8:80 was 9:1.
After ca. 20 d ratio of 9:90 was 6:1.
Recorded in (CD3)2SO.
g
h
i
Mixture of cis and trans isomers.
m(NH)/m(OH).
temperature in chlorinated solvent or use of a chloride abs-
tractor such as Ag[BF4] [20,21]. This behaviour is also
observed here when solutions of 5, 80 and 9 are left to
stand. Hence when a CDCl3 solution of 5 is left for ca.
30 d an additional new species [d(P) 34.0 ppm] gradually
forms and can confidently be assigned to the cationic P/
N-chelate complex 50 [20].
[1J(PH) 2.8 Hz] was observed for all four compounds. Inter-
estingly, as documented by others [7], the pyridinic CH pro-
ton adjacent to the nitrogen experiences a significant
downfield shift [d(H) 8.78–9.32 ppm] upon P/N-chelation.
3.3. X-ray studies
Braunstein [6b] recently showed that phosphinitopyridine
ligands form mononuclear tetrahedral nickel(II) complexes
in which these ligands adopt a six-membered ring conforma-
tion. We wished to probe whether 1-Br (or indeed 10-Cl,
1-OH and 1-H) could effectively function as P/N-chelating
ligands at a palladium(II) metal centre. Reaction of 1-Br,
10-Cl, 1-OH or 1-H with Pd(Me)Cl(cod) in a 1:1 molar ratio,
in CH2Cl2, gave after work-up the new chelate complexes
14–17 in high yields (>80%). Two geometric isomers are pos-
sible for 14–17 yet 31P{1H} NMR spectroscopy showed one
single resonance around d(P) 35 ppm (Table 2). We believe
this isomer to have the phosphine (ꢀPPh2) group trans to
the chloride ligand [7,9b]. Additionally the 1H NMR spectra
clearly showed the presence of a methyl ligand within the
coordination sphere since a doublet around 0.5 ppm
The X-ray structures of 4, 5, 10, 16 Æ (CH3)2SO and
18 Æ CHCl3 have each been determined and illustrate the
flexible bonding nature of 1-Cl, 1-Br, 1-OH and 1-H
ligands in accommodating P-monodentate, P/N-chelating
and P/N-bridging coordination modes (see Table 3).
The structures of the ruthenium complexes 4 (Fig. 1) and
5 (Fig. 2) confirm a classic ‘‘piano-stool’’ geometry formed
by the ancillary g6-p-MeC6H4 Pr ligand and the three ‘‘legs’’
i
being the two chlorides and the phosphorus donor of the P-
monodentate pyridylphoshine. There are no significant dif-
ferences observed in the Ru–P and Ru–Cl bond lengths for 4
and 5 and both are comparable to other previously reported
compounds [2c,20,22]. There is an intramolecular N–
˚
Hꢂ ꢂ ꢂClcoord hydrogen bond in 4 [N(1)ꢂ ꢂ ꢂCl(1) 3.162(4) A,
˚
H(1n)ꢂ ꢂ ꢂCl(1) 2.35(2) A; N(1)–H(1n)ꢂ ꢂ ꢂCl(1) 154(4)ꢁ] and

S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
2985
Table 3
Crystallographic data for 4, 5, 10, 16 Æ (CH3)2SO and 18 Æ CHCl3
4
5
10
Pd
16 Æ (CH3)2SO
Pd
18 Æ CHCl3
Pd
M
Ru
Ru
2.3426(12)
˚
Bond length (A)
M(1)–P(1)
2.3443(15)
2.2778(10)
2.1864(10)
2.4166(10)
2.2497(10)
M(1)–P(2)
M(1)–Cl(1)
M(1)–Cl(2)
M(1)–N(1)
2.2694(10)
2.3606(11)
2.3681(10)
2.4321(13)
2.4063(15)
2.4345(10)
2.4048(12)
2.2991(9)
2.2954(9)
2.113(3)
2.2275(18)
2.049(2)
M(1)–C(1)
M(1)–Carene range
P(1)–Cmethylene
P(2)–Cmethylene
Cmethylene–N(1)
2.177(4)–2.248(5)
1.875(4)
2.187(3)–2.244(3)
1.873(3)
1.843(3)
1.845(4)
1.447(5)
1.450(5)
1.413(5)
1.410(5)
1.826(2)
1.452(3)
1.372(3)
1.338(3)
1.858(4)
1.439(5)
1.370(5)
1.361(5)
1.450(6)
1.395(6)
1.445(4)
1.371(4)
C
methylene–N(3)
N(1)–Caromatic
N(3)–Caromatic
C(15)–N(2)
Bond angles (ꢁ)
P(1)–M(1)–Cl(1)
P(1)–M(1)–Cl(2)
P(2)–M(1)–Cl(1)
P(2)–M(1)–Cl(2)
P(1)–M(1)–P(2)
Cl(1)–M(1)–Cl(2)
Cl(1)–M(1)–N(2)
Cl(2)–M(1)–N(2)
Cl(1)–M(1)–C(1)
P(1)–M(1)–C(1)
N(2)–M(1)–C(1)
P(1)–M(1)–N
P(1)–Ru(1)–Carene range
P(1)–Cmethylene–N(1)
P(2)–Cmethylene–N(3)
Cmethylene–N(1)–Caromatic
88.29(5)
83.85(5)
89.01(4)
83.64(4)
168.28(3)
172.43(2)
88.42(3)
92.67(3)
88.60(4)
89.86(4)
169.66(3)
96.63(4)
86.58(4)
88.24(4)
88.55(3)
175.18(4)
89.31(8)
89.70(8)
93.13(6)
87.70(7)
86.16(7)
179.05(8)
92.98(6)
177.43(8)
109.8(3)
125.1(3)
93.44(13)–160.39(15)
112.3(3)
93.31(9)–160.59(11)
110.5(2)
115.5(3)
112.6(3)
117.6(3)
119.3(3)
110.42(15)
119.22(19)
122.9(3)
123.2(2)
C
methylene–N(3)–Caromatic
˚
˚
5 [N(1)ꢂ ꢂ ꢂCl(1) 3.133(3) A, H(1n)ꢂ ꢂ ꢂCl(1) 2.313(18) A;
N(1)–H(1n)ꢂ ꢂ ꢂCl(1) 154(3)ꢁ].
The palladium complex 10 (Fig. 3) displays a cis config-
uration with respect to the phosphorus ligands, the palla-
dium(II) centre being in a near square planar geometry
[Cl(1)–Pd(1)–Cl(2) 86.58(4)ꢁ, P(1)–Pd(1)–Cl(2) 88.60(4)ꢁ,
P(2)–Pd(1)–Cl(1) 89.86(4)ꢁ, P(2)–Pd(1)–P(1) 96.63(4)ꢁ].
The Pd–P and Pd–Cl bond distances are normal and there
is an intermolecular N–Hꢂ ꢂ ꢂClcoord hydrogen bond
˚
˚
[N(1)ꢂ ꢂ ꢂCl(1) 3.310(4) A, H(1N)ꢂ ꢂ ꢂCl(1) 2.65(4) A; N(1)–
H(1N)ꢂ ꢂ ꢂCl(1) 137(3)ꢁ; symm. code = 0.5 ꢀx, 0.5 ꢀy,
1 ꢀz]. We recently reported [21] an X-ray structure deter-
mination of the platinum(II) complex PtCl2(10-Cl)2 in
which molecules are arranged into dimer pairs via intermo-
lecular N–Hꢂ ꢂ ꢂCl H-bonding.
The X-ray structure of 16 Æ (CH3)2SO (Fig. 4) clearly
shows that 1-OH adopts a P/N-chelating mode with the
two additional coordination sites occupied by methyl
and chloride ligands. The bond angles around palladium
[P(1)–Pd(1)–C(1) 86.16(7)ꢁ, Cl(1)–Pd(1)–C(1) 87.70(7)ꢁ,
P(1)–Pd(1)–N(2) 92.98(6)ꢁ and Cl(1)–Pd(1)–N(2) 93.13(6)ꢁ]
confirm an approximate square-planar arrangement with
the pyridyl nitrogen trans to the methyl group [9b]. The
Fig. 1. X-ray structure of 4. All hydrogens, except on N(1), have been
omitted for clarity. The g6-coordination is illustrated by a thick dashed
line between Ru and the centroid of the aromatic ring of the p-cymene
ligand. The H-bond is shown as a dashed line.

2986
S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
Fig. 4. X-ray structure of 16.
Fig. 2. X-ray structure of 5. All hydrogens, except on N(1), have been
omitted for clarity. The g6-coordination is illustrated by a thick dashed
line between Ru and the centroid of the aromatic ring of the p-cymene
ligand. The H-bond is shown as a dashed line.
Pd–P, Pd–N, Pd–C and Pd–Cl bond lengthsare all in the nor-
mal range [9b]. The Pd–P–C–N–C–N six-membered ring has
a twist-boat conformation. The dihedral angle between the
coordination plane and that of the pyridine ring in 16 is
33.24(8)ꢁ. There is an intramolecular N–Hꢂ ꢂ ꢂO hydrogen
bond to the neighbouring phenolic group [N(1)ꢂ ꢂ ꢂO(1)
˚
˚
2.651(2) A, H(1)ꢂ ꢂ ꢂO(1) 2.23(2) A; N(1)–H(1)ꢂ ꢂ ꢂO(1)
109(2)ꢁ].
A few crystals of 18 Æ CHCl3 (Fig. 5) were obtained when a
solution of 17 was allowed to stand for a prolonged period.
X-ray crystallography confirmed that two pyridylphos-
phines 1-H span both PdCl2 units giving a 12-membered
metallocycle and is essentially identical [39] to that previ-
ously reported (in this case as the CH2Cl2 solvate). Mak
and co-workers [40] have shown that 2,6-bis(diph-
enylphosphino)pyridine can be used to synthesise a 12-mem-
bered dimethylplatinum(II) metallocycle in which only the
Fig. 5. X-ray structure of 18 Æ CHCl3. All hydrogens, except on N(1), and
the solvent have been omitted for clarity. Symmetry code = 1 ꢀ x, 1 ꢀ y,
1 ꢀ z.
two P-donors are coordinated. The two Pd–Cl bond lengths
˚
[2.2991(9) and 2.2954(9) A] are similar to those previously
reported [39] yet shorter than those found in 10 and
˚
16 Æ (CH3)2SO whilst the Pd–P distance [2.2497(10) A] is
longer than in 16 Æ (CH3)2SO. The difference in Pd–N(2) dis-
Fig. 3. X-ray structure of 10. All hydrogens, except on N(1) and N(3), have been omitted for clarity.

S.E. Durran et al. / Inorganica Chimica Acta 359 (2006) 2980–2988
2987
´
[3] (a) J.A. Casares, P. Espinet, J.M. Martın-Alvarez, V. Santos, Inorg.
Chem. 43 (2004) 189;
tances can be attributed to the different trans groups
˚
[2.2275(18) A (N(2) trans to C) in 16 Æ (CH3)2SO versus
(b) Q.-M. Wang, Y.-A. Lee, O. Crespo, J. Deaton, C. Tang, H.J.
Gysling, M.C. Gimeno, C. Larraz, M.D. Villacampa, A. Laguna, R.
Eisenberg, J. Am. Chem. Soc. 126 (2004) 9488.
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2.113(3) A (N(2) trans to P) in 18 Æ CHCl3]. The non-bonded
Pdꢂ ꢂ ꢂPd separation between PdCl2 units in 18 Æ CHCl3 is
˚
4.6555(6) A and can be compared with known homobimetal-
[4] (a) M.L. Clarke, D.J. Cole-Hamilton, D.F. Foster, A.M.Z. Slawin,
J.D. Woolllins, J. Chem. Soc., Dalton Trans. (2002) 1618;
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˚
˚
˚
lic Pd2 complexes (4.594 A [39], 4.710(1) A [41], 5.261(2) A
˚
[42] and 9.0239(5) A [43]) using other pyridylphosphines as
bridging ligands. Unlike Ph2PPy and related pyridylphos-
phines, which have very rigid structures and have been used
to synthesise hetero- and homonuclear metal complexes con-
taining a metal–metal bond [6c,44], the inclusion of two flex-
ible spacer atoms (carbon/nitrogen) disfavours any Pdꢂ ꢂ ꢂPd
interaction here. The dihedral angle between the coordina-
tion plane and that of the pyridine ring is 70.70(9)ꢁ.
[5] J.H. Downing, M.B. Smith, Phosphorus Ligands in Comprehensive
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´
´
´
(f) G. Sanchez, J. Garcıa, D. Meseguer, J.L. Serrano, L. Garcıa, J.
´
Perez, G. Lopez, Inorg. Chim. Acta 357 (2004) 4568.
Two new pyridylphosphines have been prepared and
their coordination chemistry investigated with a range of
late transition-metals. Functionalised phosphines continue
to find considerable importance in many catalytic processes
and this uniqueness can often be traced to the flexible ligat-
ing behaviour of many of these hybrid ligands.
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We are grateful to Johnson-Matthey for the kind dona-
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A complete set of X-ray crystallographic structural data
for compounds 4, 5, 10, 16 Æ (CH3)2SO and 18 Æ CHCl3
(CCDC Nos. 289544, 289545, 289546, 217957 and
218017, respectively) is available at the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2
1EZ, UK, fax: +44 1223 366 033, e-mail: deposit@ccdc.
ac.uk or on the web www: http://www.ccdc.cam.ac.uk)
on request, quoting the deposition numbers. Supplemen-
tary data associated with this article can be found, in the
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