Two square-planar palladium(II) complexes with P,O-bidentate hybrid ligands

Article abstract of DOI:10.1107/S0108270106048530

In the two square-planar palladium(II) complexes chloro[(diphenylphosphinoamino)diphenylphosphine oxide]methylpalladium(II) dimethyl sulfoxide solvate, [Pd(CH₃)Cl(C₂₄H ₂₁NOP₂)]·C₂H₆OS, (I), and chloro{[2-(diphenylphosphino)phenyl]diethoxymethane}methylpalladium(II), [Pd(CH₃)Cl(C₂₃H₂₅O₂P)], (II), a trans disposition of the diphenylphosphino and chloro groups is observed. The Pd atom in both complexes displays a distorted square-planar configuration formed by the four unique donor atoms (P, Cl, C and O). In compound (I), the five-membered Pd-P-N-P-O metallacycle is best described as having an envelope conformation, whereas in (II) the six-membered Pd-P-C-C-C-O metallacycle adopts a skewed boat conformation. Furthermore, within the P-N-P-O backbone in (I), the P-N distances are consistent with single-bond character [1.659 (3) and 1.692 (3) A], whilst the P=O bond shows appreciable double-bond character [1.509 (2) A].

Full text of DOI:10.1107/S0108270106048530

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
The chemistry of Ph2PNHP(O)Ph2, akin to Ph2PCH2P-
(O)Ph2, has been studied extensively (Bhattacharyya et al.,
1996; Smith & Slawin, 2000), while few studies have been
reported with ligands such as 2-Ph2PC6H4CH(OR)2 (Bei et al.,
1999). Compound (I) was obtained from the reaction of
Pd(CH3)Cl(cod) (cod = cycloocta-1,5-diene) and Ph2PNHP-
(O)Ph2. The P,O-bidentate ligand in (II) was obtained during
an unsuccessful attempt to condense 2-(diphenylphosphino)-
benzaldehyde with 2-amino-3-methoxybenzoic acid in abso-
lute ethanol, followed by complexation with Pd(CH3)Cl(cod).
Presumably, solvolysis of 2-(diphenylphosphino)benzalde-
hyde produced the ligand 2-Ph2PC6H4CH(OCH2CH3)2 rather
than the intended Schiff base product 2-Ph2PC6H4CH N-
C6H4CO2H(3-OCH3).
ISSN 0108-2701
Two square-planar palladium(II)
complexes with P,O-bidentate hybrid
ligands
Mark R. J. Elsegood,a Martin B. Smitha* and Sophie H.
Daleb
aChemistry Department, Loughborough University, Loughborough, Leicestershire
LE11 3TU, England, and bMolecular Profiles, 8 Orchard Place, Nottingham Business
Park, Nottingham NG8 6PX, England
Correspondence e-mail: m.b.smith@lboro.ac.uk
Received 7 November 2006
Accepted 14 November 2006
Online 12 December 2006
In the two square-planar palladium(II) complexes chloro-
[(diphenylphosphinoamino)diphenylphosphine oxide]methyl-
palladium(II) dimethyl sulfoxide solvate, [Pd(CH3)Cl(C24H21-
NOP2)]ÁC2H6OS, (I), and chloro{[2-(diphenylphosphino)-
phenyl]diethoxymethane}methylpalladium(II), [Pd(CH3)Cl(C23-
H25O2P)], (II), a trans disposition of the diphenylphosphino
and chloro groups is observed. The Pd atom in both complexes
displays a distorted square-planar con®guration formed by the
four unique donor atoms (P, Cl, C and O). In compound (I),
the ®ve-membered Pd±P±N±P±O metallacycle is best
described as having an envelope conformation, whereas in
(II) the six-membered Pd±P±C±C±C±O metallacycle adopts a
skewed boat conformation. Furthermore, within the P±N±P±O
The structure of (I) (Fig. 1 and Table 1) con®rms a near
square-planar arrangement of ligands around the PdII metal
centre. Of the two possible geometric isomers expected for (I),
we observe here that the phosphoryl O-donor atom is trans to
the methyl ligand. The Pd atom deviates from the least-
Ê
squares plane through atoms P1/O1/Cl1/C1 by 0.1567 (2) A.
The P- and O-donor atoms form a ®ve-membered metallacycle
(containing atoms P1/N1/P2/O1/Pd1) which adopts an
envelope conformation, with atom O1, the ¯ap atom, out of
Ê
the plane by 0.2616 (10) A. Within the Pd1±P1±N1±P2±O1
ring, the P1ÐN1, N1ÐP2 and P2ÐO1 bond lengths are in
good agreement with those of Ph2PNHP(O)Ph2 and other
previously reported compounds (Bhattacharyya et al., 1996;
Smith & Slawin, 2000). Such data are consistent with the
absence of double-bond character in the P1ÐN1 and N1ÐP2
backbone in (I), the PÐN distances are consistent with single-
Ê
bond character [1.659 (3) and 1.692 (3) A], whilst the P
bond shows appreciable double-bond character [1.509 (2) A].
O
Ê
Comment
Hybrid ligands combining soft (e.g. PIII) and hard donor atoms
(e.g. an O atom from a phosphine oxide or ether functional
group) continue to receive widespread attention (Braunstein,
2006; Grushin, 2004). Phosphine oxides, mixed phosphine/
phosphine oxides and ether-functionalized phosphines are
versatile compounds that can display hemilabile properties
through the different electronic effects exerted by each donor
atom (Gianneschi et al., 2005). Accordingly, the P-donor atom
is coordinated strongly to a metal centre, whereas the O-donor
atom is weakly bound, thereby promoting a vacant site upon
dissociation. These ligands have found a range of applications
in areas such as organic syntheses, coordination chemistry,
catalysis, and industrial processes such as selective metal
extraction (Kabat et al., 2001; Yeo et al., 1999; Nash et al., 2002,
and references therein). We present here the structures of two
square-planar palladium(II) complexes, (I) and (II),
containing two different P,O-bidentate hybrid ligands.
Figure 1
A perspective view of (I), showing the atom-labelling scheme. Displace-
ment ellipsoids are drawn at the 40% probability level, and amino and
methyl H atoms are shown as small spheres of arbitrary radii. Other H
atoms have been omitted. The minor disorder component has been
omitted for clarity. The hydrogen bond is shown as a dashed line.
Acta Cryst. (2007). C63, m7±m9
DOI: 10.1107/S0108270106048530
# 2007 International Union of Crystallography m7

metal-organic compounds
0.177 mmol). After ca 1 min, solid (I) was deposited and this mixture
was stirred for an additional 15 min. Diethyl ether (10 ml) was added
to further the precipitation, and the solid was collected by suction
®ltration and dried in vacuo (yield 0.097 g, 98%). Selected spectro-
scopic data: 31P{1H} NMR (DMSO-d6): ꢀ 65.8, 44.5 [2J(PP) = 23 Hz];
1H NMR (DMSO-d6): ꢀ 8.73 (NH), 7.70±7.51 (aromatic H), 0.50
[3J(PH) = 3 Hz (CH3)]; FT±IR: ꢁNH 2988, ꢁPO 1145 cm 1. Analysis
found: C 53.56, H 4.26, N 2.53; C25H24ClNOP2Pd requires: C 53.78, H
4.34, N 2.51%. Colourless block-shaped crystals of (I) were obtained
by vapour diffusion of diethyl ether into a CDCl3 solution of (I)
containing a few drops of DMSO.
For the preparation of (II), an unsuccessful attempt to synthesize
the Schiff base compound 2-Ph2PC6H4CH NC6H4CO2H(3-OCH3)
by re¯uxing an absolute ethanol solution (10 ml) of 2-Ph2PC6H4-
CHO (0.184 g, 0.634 mmol) and H2NC6H4(OCH3)(CO2H) (0.109 g,
0.652 mmol) under nitrogen for ca 7 d gave instead 2-Ph2PC6-
H4CH(OCH2CH3)2 [ꢀ(P) 17.0 p.p.m. (ca 60% purity by 31P{1H}
NMR)]. The ligand 2-Ph2PC6H4CH(OCH2CH3)2 was reacted with
Pd(CH3)Cl(cod) in CDCl3 to afford (II). Selected spectroscopic data:
31P{1H} NMR (CDCl3): ꢀ 28.0; 1H NMR (CDCl3): ꢀ 7.53±7.01
(aromatic H), 5.37 (CH), 4.18 and 3.69 (both CH2), 1.08 (CH3), 0.90
[3J(PH) = 4 Hz (PdÐCH3)]. Analysis found: C 54.57, H 5.30;
C24H28ClO2PPd requires: C 55.29, H 5.43%. Yellow block-shaped
crystals of (II) were obtained upon slow diffusion of petroleum ether
(b.p. 333±353 K) into a CDCl3 solution of the product.
Figure 2
A
perspective view of (II), showing the atom-labelling scheme.
Displacement ellipsoids are drawn at the 50% probability level. CH2
and methyl H atoms are shown as small spheres of arbitrary radii. Other
H atoms have been omitted.
bonds. In contrast, when amine deprotonation is performed
we have previously observed shortening of the P1ÐN1 and
N1ÐP2 bond lengths and lengthening of the O1ÐP2 bond,
consistent with appreciable double-bond character within the
P1±N1±P2±O1 ring. Similar bond-length changes have also
been reported in phosphinoenolate chemistry when P,O-
chelated to metal centres (Braunstein, 2006). There is one NÐ
HÁ Á ÁO intermolecular hydrogen bond in the structure of (I), to
a dimethyl sulfoxide (DMSO) solvent molecule (Table 2).
The structure of (II) establishes that the P,O-bidentate
Compound (I)
Crystal data
3
Ê
[Pd(CH3)Cl(C24H21NOP2)]Á-
V = 1415.61 (13) A
Z = 2
C2H6OS
Mr = 636.37
3
Dx = 1.493 Mg m
Mo Kꢃ radiation
Monoclinic, Pn
a = 11.5432 (6) A
1
Ê
ꢄ = 0.96 mm
T = 150 (2) K
Ê
b = 9.5417 (5) A
hybrid ligand functions in
a
similar manner to
Ê
c = 13.1351 (7) A
Block, colourless
0.42 Â 0.15 Â 0.14 mm
Ph2PNHP(O)Ph2 (Fig. 3 and Table 3). Similar to (I), the
geometric isomer observed here places the diphenylphosphino
group cis to a methyl ligand, as would be expected on the basis
of their different trans effects. The Pd1ÐO1 bond length is
similar to (I) and other palladium(II) compounds (Bei et al.,
1999). The Pd atom deviates from the least-squares plane
ꢂ = 101.904 (2)ꢀ
Data collection
Bruker SMART 1000 CCD area-
detector diffractometer
! rotation scans with narrow frames
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.688, Tmax = 0.877
10824 measured re¯ections
5385 independent re¯ections
5182 re¯ections with I > 2ꢅ(I)
Rint = 0.014
ꢆmax = 26.0ꢀ
Ê
through atoms P1/O1/Cl1/C1 by 0.0151 (7) A. The P,O-donor
substituents form a six-membered metallacycle (containing
atoms Pd1/O1/P1/C4/C7/C12), which adopts a skewed-boat
conformation, with atom C4 having the largest deviation from
Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.023
wR(F2) = 0.054
w = 1/[ꢅ2(Fo2) + (0.0274P)2
+ 0.4115P]
Ê
coplanarity [0.4789 (13) A]. The difference in the C4ÐO1
2
where P = (Fo + 2Fc2)/3
Ê
Ê
[1.439 (2) A] and C4ÐO2 [1.388 (2) A] bond lengths con®rms
that one of the ether groups is coordinated while the other is
not. Furthermore, it should be noted the PÐPdÐO bite angles
in the two complexes are different [86.93 (6)ꢀ for (I) and
92.65 (3)ꢀ for (II)], which is consistent with the different ring
sizes adopted by the P,O-bidentate ligands.
S = 1.04
5385 re¯ections
327 parameters
H-atom parameters constrained
(Á/ꢅ)max = 0.001
3
Ê
Áꢇmax = 0.47 e A
3
Ê
0.54 e A
Áꢇmin
=
Absolute structure: Flack (1983),
with 2596 Friedel pairs
Flack parameter: 0.02 (2)
Table 1
Selected geometric parameters (A, ) for (I).
In summary, we have shown that two P,O-bidentate hybrid
ligands display envelope [for (I)] and skewed-boat [for (II)]
ring conformations when complexed to square-planar palla-
dium(II) bearing ancillary methyl and chloro ligands.
ꢀ
Ê
Pd1ÐC1
Pd1ÐP2
Pd1ÐO1
Pd1ÐCl1
2.023 (4)
2.1880 (8)
2.228 (2)
2.3674 (9)
O1ÐP1
P1ÐN1
N1ÐP2
1.509 (2)
1.659 (3)
1.692 (3)
Experimental
C1ÐPd1ÐP2
C1ÐPd1ÐO1
P2ÐPd1ÐO1
89.77 (11)
176.31 (14)
86.93 (6)
C1ÐPd1ÐCl1
P2ÐPd1ÐCl1
O1ÐPd1ÐCl1
89.77 (11)
176.43 (3)
93.63 (6)
For the preparation of (I), Ph2PNHP(O)Ph2 (0.072 g, 0.179 mmol)
was added to a CH2Cl2 solution (2 ml) of Pd(CH3)Cl(cod) (0.047 g,
ꢁ
m8 Elsegood et al.
[Pd(CH3)Cl(C24H21NOP2)]ÁC2H6OS and [Pd(CH3)Cl(C23H25O2P)]
Acta Cryst. (2007). C63, m7±m9

metal-organic compounds
Table 2
Hydrogen-bond geometry (A, ) for (I).
H atoms were placed in geometric positions, with CÐH = 0.95±
ꢀ
Ê
Ê
Ê
0.99 A and NÐH = 0.88 A, and were treated using a riding model,
with Uiso(H) = 1.2Ueq(C,N). In (I), the DMSO molecule exhibits
disorder, which was modelled with the S atom in two positions [major
occupancy 0.671 (3)]. Restraints were applied to the SÐO and SÐC
bond lengths [SADI restraint in SHELXTL (Bruker, 2000)] and to
the anisotropic displacement parameters (SIMU and DELU
restraints in SHELXTL) of the non-H atoms of the DMSO molecule,
and also to those of atoms C2±C13 of the benzene rings. The data sets
for both (I) and (II) were truncated at 2ꢆ = 52ꢀ; re¯ections were of
insigni®cant intensity above this value. For (I), the correct orientation
of the structure with respect to the polar-axis directions was estab-
lished by means of the Flack (1983) parameter.
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N1ÐH1Á Á ÁO2
0.88
1.89
2.757 (4)
167
Compound (II)
Crystal data
[Pd(CH3)Cl(C23H25O2P)]
Mr = 521.28
Orthorhombic, Pbca
Z = 8
Dx = 1.512 Mg m
Mo Kꢃ radiation
ꢄ = 1.01 mm
T = 150 (2) K
Block, yellow
0.22 Â 0.20 Â 0.14 mm
3
1
Ê
a = 17.3748 (5) A
Ê
Ê
For both compounds, data collection: SMART (Bruker, 2001); cell
re®nement: SAINT (Bruker, 2001); data reduction: SAINT;
program(s) used to solve structure: SHELXTL (Bruker, 2000);
program(s) used to re®ne structure: SHELXTL; molecular graphics:
SHELXTL; software used to prepare material for publication:
SHELXTL and local programs.
b = 14.3919 (4) A
c = 18.3124 (5) A
3
Ê
V = 4579.1 (2) A
Data collection
Bruker SMART 1000 CCD area-
detector diffractometer
! rotation scans with narrow frames
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.808, Tmax = 0.871
34078 measured re¯ections
4504 independent re¯ections
3901 re¯ections with I > 2ꢅ(I)
Rint = 0.020
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GD3061). Services for accessing these data are
described at the back of the journal.
ꢆmax = 26.0ꢀ
References
Re®nement
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Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.020
wR(F2) = 0.056
S = 1.10
4504 re¯ections
w = 1/[ꢅ2(Fo2) + (0.0245P)2
+ 3.3794P]
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(Á/ꢅ)max < 0.001
3
Ê
Áꢇmax = 0.39 e A
3
Ê
0.24 e A
265 parameters
H-atom parameters constrained
Áꢇmin
=
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ꢀ
Ê
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Pd1ÐC1
Pd1ÐO1
Pd1ÐP1
2.027 (2)
2.2112 (13)
2.2181 (5)
Pd1ÐCl1
O1ÐC4
C4ÐO2
2.3663 (5)
1.439 (2)
1.388 (2)
È
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C1ÐPd1ÐO1
C1ÐPd1ÐP1
O1ÐPd1ÐP1
177.48 (7)
89.87 (6)
92.65 (3)
C1ÐPd1ÐCl1
O1ÐPd1ÐCl1
P1ÐPd1ÐCl1
90.63 (6)
86.85 (4)
178.38 (2)
ꢁ
Acta Cryst. (2007). C63, m7±m9
Elsegood et al.
[Pd(CH3)Cl(C24H21NOP2)]ÁC2H6OS and [Pd(CH3)Cl(C23H25O2P)] m9