Synthesis and characterization of new oxazoline-based palladacycles with bridging or terminal imidate ligands. Crystal structures of [{Pd(μ-dibromomaleimidate)(Phox)}2], [Pd(dibromomaleimidate)(Phox)(PPh3)] and [Pd(glutarimidate)(Phox)(PPh3)] (Phox = 2-(2-oxazolinyl)phenyl))

Article abstract of DOI:10.1016/j.poly.2008.02.001

The dinuclear hydroxo complex [{Pd(μ-OH)(Phox)}₂] (I) (Phox = 2-(2-oxazolinyl)phenyl) reacts in a 1:2 molar ratio with several imidate ligands to yield new cyclometallated palladium complexes [{Pd(μ-NCO)(Phox)}₂] containing asymmetric imidate -NCO- bridging units. [-NCO- = succinimidate (succ) (1), phtalimidate (phtal) (2), maleimidate (mal) (3), 2,3-dibromomaleimidate (2,3-diBrmal) (4) and glutarimidate (glut) (5)]. The reaction of these complexes with tertiary phosphines provides novel mononuclear N-bonded imidate derivatives of the general formula [Pd(imidate)(Phox)(PR₃)] [R = Ph (a), 4-F-C₆H₄ (b) or CH₂CH₂CN (c)]. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, FAB, ¹H, ¹³C and ³¹P). The single-crystal structures of compounds 4, 4a and 5a have been established.

Full text of DOI:10.1016/j.poly.2008.02.001

Available online at www.sciencedirect.com
Polyhedron 27 (2008) 1699–1706
www.elsevier.com/locate/poly
Synthesis and characterization of new oxazoline-based palladacycles
with bridging or terminal imidate ligands. Crystal structures
of [{Pd(l-dibromomaleimidate)(Phox)}2], [Pd(dibromomaleimidate)
(Phox)(PPh3)] and [Pd(glutarimidate)(Phox)(PPh3)]
(Phox = 2-(2-oxazolinyl)phenyl))
a,
a
a
a
b
*
´
´
´ ´
´
´
´
´
Jose Luis Serrano , Luis Garcıa , Jose Perez , Eduardo Perez , Joaquın Garcıa ,
b
b
c
d
´
Gregorio Sanchez , Gregorio Lopez , Ian J.S. Fairlamb , Malva Liu
a
´
Departamento de Ingenierı´a Minera, Geolo´gica y Cartogra´fica, Area de Quı´mica Inorga´nica, 30203 Cartagena, Spain
b Departamento de Quı´mica Inorga´nica, Universidad de Murcia, 30071 Murcia, Spain
c Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
d Departamento de Termodina´mica, Universidad de Valencia, 46100 Burjassot, Valencia, Spain
Received 18 January 2008; accepted 2 February 2008
Available online 14 March 2008
Abstract
The dinuclear hydroxo complex [{Pd(l-OH)(Phox)}2] (I) (Phox = 2-(2-oxazolinyl)phenyl) reacts in a 1:2 molar ratio with several imi-
date ligands to yield new cyclometallated palladium complexes [{Pd(l-NCO)(Phox)}2] containing asymmetric imidate –NCO– bridging
units. [–NCO– = succinimidate (succ) (1), phtalimidate (phtal) (2), maleimidate (mal) (3), 2,3-dibromomaleimidate (2,3-diBrmal) (4) and
glutarimidate (glut) (5)]. The reaction of these complexes with tertiary phosphines provides novel mononuclear N-bonded imidate deriv-
atives of the general formula [Pd(imidate)(Phox)(PR3)] [R = Ph (a), 4-F–C6H4 (b) or CH2CH2CN (c)]. The new complexes were charac-
terized by partial elemental analyses and spectroscopic methods (IR, FAB, 1H, 13C and 31P). The single-crystal structures of compounds
4, 4a and 5a have been established.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Imidate complexes; Cyclometallated palladium(II) complexes; 2-Phenyl-2-oxazoline; X-ray study
1. Introduction
cursors of mononuclear and dinuclear cyclometallates [4–
12]. Since 1970 to date several reviews have been dedicated
to different aspects of their chemistry such as synthesis and
structural characterization, their applications in organic
synthesis, organometallic catalysis, their use as chiral aux-
iliaries, mesogenic and luminiscent agents or their presence
in medicinal and biological chemistry [13]. Among these
fields, it can be said that over the last few years the appli-
cability of palladacycles as precatalyst has been the main
focus of attention. In this sense, and stimulated by our
recent discovery of imidate effects in Pd-catalysed cross-
coupling processes [14], we have reported on the synthesis
of dinuclear orthometallated palladium(II) derivatives with
Palladium compounds containing one metal–carbon
bond intramolecularly stabilized by a donor heteroatom
are one of the most popular classes of organopalladium
derivatives. Initial studies dealt with azobenzenes and het-
eroaromatic ligands that can easily be orthometallated by
Pd(II) salts via C(sp2)–H bond cleavage [1–3] to usually
give the corresponding acetate or halide-bridged dimers.
These complexes have been employed as convenient pre-
*
Corresponding author.
E-mail address: jose.serrano@upct.es (J.L. Serrano).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.02.001

1700
J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
–NCO– bridging ligands and their use as precursors of
mononuclear N-bonded imidate derivatives [15,16]. Those
dinuclear and mononuclear derivatives, containing an azo-
benzene, 2-phenylpyridine or benzoquinoline backbone,
have shown to be active catalysts/precatalysts for the
Suzuki–Miyaura cross-coupling reactions of aryl bromides
with aryl boronic acids, and the Sonogashira reactions of
aryl halides (in the presence and absence of Cu(I) salts)
[17]. The conversions are dependent, to some extent, on
the cyclometallated backbone and the imidate ligand, sug-
gesting a role for these pseudohalides in the catalytic cycle
in both cross-coupling processes and encouraging us to
expand the range of systems under study.
On the other hand, the synthetic value of palladium(II)
and platinum(II) di-l-hydroxo-complexes is a subject of
continuous study [18–22]. During the last few years we
have also been developing the usefulness of binuclear
hydroxo complexes of palladium, some of them with a
cyclometallated backbone [23], in the preparation of an
extensive selection of new compounds, by means of a sim-
ple acid–base reaction [24].
We report here the use of the hydroxo-complex [{Pd-
(l-OH)(Phox)}2] (Phox = 2-(2-oxazolinyl)phenyl) in the
preparation of new dinuclear palladium(II) derivatives of
simple and sterically not hindered 2-phenyl-2-oxazoline
with bridging succinimide, phtalimide, maleimide, 2,3-
dibromomaleimide and glutarimide ligands acting in the
coordination mode mentioned above. We also describe
the synthesis of mononuclear N-bonded imidate deriva-
tives, by the reaction of the corresponding dinuclear
precursor with neutral phosphine ligands. X-ray diffraction
analyses of both mononuclear (4a,5a) and binuclear (4)
derivatives are also given. To date, just three complexes
containing an orthopalladated 2-phenyl-2-oxazoline ligand
have been crystallographically characterised (searched at
the Cambridge Structural Database (CSD) v. 5.28 updated
till August 2007) [23a,25].
pared as described in the literature. The commercially
available chemicals were purchased from Aldrich Chemical
Co. and were used without further purification, and all the
solvents were dried by standard methods before use.
2.2. Synthesis
2.2.1. Preparation of complexes [{Pd(l-NCO)(Phox)}2]
(–NCO– = suc (1); R = phtal (2); R = mal (3); R = 2,3-
diBrmal (4); R = glut (5))
The new complexes were obtained by treating [{Pd(l-
OH)(Phox)}2] with the corresponding imidate ligand in
molar ratio 1:2, using (CH3)2CO as the solvent and accord-
ing to the following general method. To an acetone suspen-
sion (20 mL) of the precursor (250 mg; 0.464 mmol) was
added the stoichiometric amount of the corresponding imi-
date ligand. The resulting suspension was stirred for 60 min
at reflux temperature and then concentrated to a quarter of
volume under reduced pressure. Addition of (CH3CH2)2O
caused precipitation of the new complexes, which were fil-
tered off, air dried and recrystallised from CH2Cl2/C6H14.
[{Pd(l-suc)(Phox)}2] (1): (85% yield). Anal. Calc. for
C26H24N4O6Pd2: C, 44.5; H, 3.5; N, 8.0. Found: C, 44.3; H,
3.6; N, 8.3%. FT-IR (nujol mull cmꢁ1): m(CN–Phox)
1
1640(vs); m(CO) 1720(vs); 1592(vs). H NMR (300 MHz,
CDCl3): d (SiMe4) (ppm): 2.17 (m, 4H, suc), 2.79 (m, 6H,
4Hsuc + 2H NCH2), 3.56 (m, 4H, 2NCH2 + 2OCH2),
4.29 (m, 2H, OCH2), 6.75 (m, 2H, arom.), 7.04 (m, 6H,
arom.). FAB-MS (positive mode) m/z: 702 (M+), 604
(M+-suc).
[{Pd(l-phtal)(Phox)}2] (2): (82% yield). Anal. Calc.
for C34H24N4O6Pd2: C, 51.2; H, 3.0; N, 7.0. Found: C,
51.0; H, 3.3; N, 7.3%. FT-IR (nujol mull cmꢁ1): m(CN–
Phox) 1630(vs); m(CO) 1730(vs); 1598(vs). 1H NMR
(300 MHz, CDCl3): d (SiMe4) (ppm): 2.90 (m, 2H,
NCH2), 3.58 (m, 4H, 2NCH2 + 2OCH2), 4.33 (m, 2H,
OCH2), 6.84 (m, 2H, phtal), 7.08 (m, 4H, arom.), 7.11
(m, 2H, phtal), 7.53 (m, 4H, arom.), 7.62 (m, 2H, phtal),
7.75 (m, 2H, phtal). FAB-MS (positive mode) m/z: 798
(M+), 652 (M+-phtal).
2. Experimental
2.1. Materials and methods
[{Pd(l-mal)(Phox)}2] (3): (75% yield). Anal. Calc. for
C26H20N4O6Pd2: C, 44.8; H, 2.9; N, 8.0. Found: C, 45.0; H,
3.0; N, 8.2%. FT-IR (nujol mull cmꢁ1): m(CN–Phox)
C, H, and N analyses were carried out with a Carlo Erba
instrument. IR spectra were recorded on a Perkin–Elmer
spectrophotometer 16F PC FT-IR, using Nujol mulls
between polyethylene sheets. NMR data (1H, 31P) were
recorded on Bruker Avance 300 spectrometer. Conduc-
tance measurements were performed with a Crison 525
conductimeter (in acetone, 5 ꢀ 10ꢁ4 M). Mass spectromet-
ric analyses were performed on a Fisons VG Autospec dou-
ble-focusing spectrometer, operated in the negative mode.
Ions were produced by fast atom bombardment (FAB)
with a beam of 25-keV Cs atoms. The mass spectrometer
was operated with an accelerating voltage of 8 kV and a
resolution of at least 1000.
1
1620(vs); m(CO) 1720(vs); 1584(vs). H NMR (300 MHz,
CDCl3): d (SiMe4) (ppm): 2.86 (m, 2H, NCH2), 3.58 (m,
4H, 2NCH2 + 2OCH2), 4.34 (m, 2H, OCH2), 6.65 (d, 2H,
mal), 7.00 (m, 4H, 2mal + 2H, arom.), 7.08 (m, 6H, arom.).
FAB-MS (positive mode) m/z: 698 (M+), 600 (M+-mal).
[{Pd(l-2,3-diBrmal)(Phox)}2] (4): (62% yield). Anal.
Calc. for C26H16Br4N4O6Pd2: C, 30.8; H, 1.6; N, 5.5.
Found: C, 30.9; H, 1.7; N, 5.5%. FT-IR (nujol mull
cmꢁ1): m(CN-2,3-dibrmal) 1640(vs); m(CO) 1738(s);
1
1574(s). H NMR (300 MHz, CDCl3): d (SiMe4) (ppm):
2.88 (m, 2H, NCH2), 3.61 (m, 4H, 2NCH2 + 2OCH2),
4.32 (m, 2H, OCH2), 6.71 (m, 2H, arom.), 7.08 (m, 6H,
arom.). FAB-MS (positive mode) m/z: 1012 (M+), 760
(M+-2,3-diBrmal).
The cyclometallated precursors [{Pd(l-OOCMe)
(Phox)}2] [25] and [{Pd(l-OH)(Phox)}2] [23a] were pre-

J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
1701
[{Pd(l-glut)(Phox)}2] (5): (52% yield). Anal. Calc.
for C28H28N4O6Pd2: C, 44.5; H, 3.5; N, 8.0. Found: C,
44.3; H, 3.6; N, 8.3%. FT-IR (nujol mull cmꢁ1): m(CN–
Phox) 1646–1634(vs); m(CO) 1560–1538(vs). 1H NMR
(300 MHz, CDCl3): d (SiMe4) (ppm): 1.92 (m, 4H, glut),
2.70–2.44 (m, 10H, 8 glut + 2H NCH2), 3.52 (m, 4H,
2NCH2 + 2OCH2), 4.27 (m, 2H, OCH2), 6.66 (m, 2H,
arom.), 7.00 (m, 4H, arom.), 7.10 (m, 2H, arom.). FAB-
MS (positive mode) m/z: 729 (M+), 618 (M+-glut).
[Pd(phtal)(Phox)(PPh3)] (2a): (72% yield). Anal.
Calc. for C35H27N2O3PPd: C, 63.6; H, 4.1; N, 4.2. Found:
C, 63.8; H, 4.2; N, 4.2%. FT-IR (nujol mull cmꢁ1): m(CN–
1
Phox) 1622(vs); m(CO) 1644(vs); m(PPh3) 534(m). H NMR
(300 MHz, CDCl3): d (SiMe4) (ppm): 3.92 (m, 2H, NCH2);
4.66 (m, 2H, OCH2); 6.55 (1H, arom.), 6.68 (1H, arom.),
6.98 (1H, arom.), 7.43 (m, 14H, 4H phtal + 9H PPh3 + 1H
arom.); 7.76 (m, 6H, PPh3). 31P NMR (300 MHz, CDCl3):
d (ppm): 41.9(s). FAB-MS (positive mode) m/z: 514 (M+-
phtal).
2.2.2. Preparation of complexes
[Pd(phtal)(Phox){P(4-F–C6H4)3}] (2b): (84% yield).
Anal. Calc. for C35H24F3N2O3PPd: C, 58.8; H, 3.4; N,
3.9. Found: C, 58.9; H, 3.6; N, 3.9%. FT-IR (nujol mull
[Pd(imidate)(Phox)(PR3)] (imidate = suc (1); phtal (2);
mal (3); 2,3-diBrmal (4); glut (5); R = Ph (a); 4-F–C6H4
(b); CH2CH2CN(c))
cmꢁ1):
m(CN–Phox)
1620(vs);
m(CO)
1644(vs);
The new complexes were obtained by treating the for-
mer bridging imidate complexes [{Pd(l–NCO–)(Phox)}2]
with the corresponding phosphine in molar ratio 1:2, using
CH2Cl2 as the solvent and according to the following gen-
eral method. To a CH2Cl2 suspension (20 mL) of the pre-
cursor (0.142 mmol) was added the stoichiometric
amount of the corresponding phosphine ligand. The result-
ing suspension was stirred for 90 min at reflux temperature
and then concentrated to a quarter of the volume under
reduced pressure. Addition of C6H14 caused the precipita-
tion of the new complexes, which were filtered off, air-dried
and recrystallised from CH2Cl2/C6H14.
m(P(C6H4F)3) 536(m). 1H NMR (300 MHz, CDCl3): d
(SiMe4) (ppm): 3.93 (m, 2H, NCH2); 4.69 (m, 2H,
OCH2); 6.44 (1H, arom.); 6.71 (1H, arom.); 6.92–6.97 (m,
7H, 1H, arom. + 6H phosphine); 7.26 (1H, arom., Phox);
7.37 (s, 4H, phtal); 7.72 (m, 6H, phosphine). 31P NMR
(300 MHz, CDCl3): d (ppm): 39.8(s). FAB-MS (positive
mode) m/z: 715 (M+); 568 (M+-phtal).
[Pd(phtal)(Phox){P(CH2CH2CN)3}] (2c): (78%
yield). Anal. Calc. for C26H24N5O3PPd: C, 52.8; H, 4.1;
N, 11.8. Found: C, 52.9; H, 4.2; N, 11.9%. FT-IR (nujol
mull cmꢁ1): m(CN–Phox) 1620(vs); m(CO) 1650(vs);
1
m(C„N) 2242(s). H NMR (300 MHz, CDCl3): d (SiMe4)
[Pd(suc)(Phox)(PPh3)] (1a): (84% yield). Anal. Calc.
for C31H27N2O3PPd: C, 60.7; H,4.4; N, 4.6. Found: C,
60.8; H, 4.5; N, 4.6%. FT-IR (nujol mull cmꢁ1): m(CN–
Phox) 1625(vs); m(CO) 1618(vs); m(PPh3) 534(m). 1H
NMR (300 MHz, CDCl3): d (SiMe4) (ppm): 1.7–1.87 (m,
2H, suc), 2.2–2.3 (m, 2H, suc), 3.97 (m, 2H, NCH2), 4.75
(m, 2H, OCH2), 6.51 (1H, arom.), 6.60 (1H, arom.), 6.96
(1H, arom.), 7.43 (m, 10H, 9PPh3 + 1H arom.), 7.82 (m,
6H, PPh3). 31P NMR (300 MHz, CDCl3): d (ppm): 41.9
(s). FAB-MS (positive mode) m/z: 514 (M+-suc).
(ppm): 2.45 (m, 6H, phosphine), 2.89 (m, 6H, phosphine),
3.72 (m, 2H, NCH2), 4.64 (m, 2H, OCH2), 6.97–7.42 (m,
4H, arom.); 7.49–7.69 (m, 4H, phtal). 31P NMR
(300 MHz, CDCl3): d (ppm): 32.4 (s). FAB-MS (positive
mode) m/z: 591 (M+); 444 (M+-phtal).
[Pd(mal)(Phox)(PPh3)] (3a): (64% yield). Anal. Calc.
for C31H25N2O3PPd: C, 60.9; H, 4.1; N, 4.6. Found:C,
70.0; H, 4.2; N, 4.6%. FT-IR (nujol mull cmꢁ1): m(CN–
Phox) 1620(vs); m(CO) 1634(vs); m(PPh3) 534(m). 1H
NMR (300 MHz, CDCl3): d (SiMe4) (ppm): 3.89 (m, 2H,
NCH2); 4.68 (m, 2H, OCH2); 6.05 (s, 2H, mal); 6.49 (m,
1H, arom.); 6.64 (m, 1H, arom.); 6.89 (m, 1H, arom.);
7.25 (m, 1H, arom.); 7.34 (m, 9H, PPh3); 7.74 (m, 6H,
PPh3). 31P NMR (300 MHz, CDCl3): d (ppm): 41.8 (s).
FAB-MS (positive mode) m/z: 514 (M+-mal).
[Pd(suc)(Phox){P(4-F–C6H4)3}] (1b): (77% yield).
Anal. Calc. for C31H24F3N2O3PPd: C, 55.8; H, 3.6; N,
4.2. Found: C, 55.9; H, 3.7; N, 4.2%. FT-IR (nujol mull
cmꢁ1): m(CN–Phox) 1642(vs); m(CO) 1620(vs); m(P(C6-
1
H4F)3) 536(m). H NMR (300 MHz, CDCl3): d (SiMe4)
(ppm): 1.83 (m, 2H, suc), 2.29 (m, 2H, suc), 3.94 (m, 2H,
NCH2), 4.72 (m, 2H, OCH2), 6.41 (1H, arom.), 6.70 (1H,
arom.), 6.92 (1H, arom.), 7.08 (m, 6H, phosphine), 7.30
(1H, arom.), 7.76 (m, 6H, phosphine). 31P NMR
(300 MHz, CDCl3): d (ppm): 39.6 (s). FAB-MS (positive
mode) m/z: 568 (M+-suc).
[Pd(mal)(Phox){P(4-F–C6H4)3}] (3b): (68% yield).
Anal. Calc. for C31H22F3N2O3PPd: C, 56.0; H, 3.3; N,
4.2. Found: C, 56.1; H, 3.5, N, 4.2%. FT-IR (nujol mull
cmꢁ1):
m(CN–Phox)
1600(vs);
m(CO)
1642(vs);
m(P(C6H4F)3) 536(m). 1H NMR (300 MHz, CDCl3): d
(SiMe4) (ppm): 3.88 (m, 2H, NCH2); 4.70 (m, 2H,
OCH2); 6.12 (s, 2H, mal); 6.41 (1H, arom.); 6.69 (1H,
arom.); 6.94 (1H, arom.); 7.04 (m, 6H, phosphine); 7.29
(1H, arom.); 7.70 (m, 6H, phosphine). 31P NMR
(300 MHz, CDCl3): d (ppm): 39.6(s). FAB-MS (positive
mode) m/z: 568 (M+-mal).
[Pd(suc)(Phox){P(CH2CH2CN)3}] (1c): (76% yield).
Anal. Calc. for C22H24N5O3PPd: C, 48.6; H,4.5; N, 12.9.
Found: C, 48.7; H, 4.5; N, 12.9%. FT-IR (nujol mull
cmꢁ1): m(CN–Phox) 1625(vs); m(CO) 1614(vs); m(C„N)
1
2240(s). H NMR (300 MHz, CDCl3): d (SiMe4) (ppm):
1.99 (m, 2H, suc), 2.39 (m, 6H, phosphine), 2.75 (m, 8H,
6H phosphine + 2H suc), 3.84 (m, 2H, NCH2), 4.71 (m,
2H, OCH2), 6.95–7.41 (m, 4H, arom.). 31P NMR
(300 MHz, CDCl3): d (ppm): 32.3 (s). FAB-MS (positive
mode) m/z: 442 (M+-suc).
[Pd(mal)(Phox){P(CH2CH2CN)3}]
(3c):
(69%
yield). Anal. Calc. for C22H22N5O3PPd: C, 48.8; H, 4.1;
N, 12.9. Found: C, 48.9; H, 4.2; N, 13.0%. FT-IR (nujol
mull cmꢁ1): m(CN–Phox) 1620(vs); m(CO) 1644(vs);
1
m(C„N) 2242(s). H NMR (300 MHz, CDCl3): d (SiMe4)

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J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
(ppm): 2.40 (m, 6H, phosphine); 2.83 (m, 6H, phosphine);
3.78 (m, 2H, NCH2); 4.69 (m, 2H, OCH2); 6.60 (s, 2H,
mal); 6.70 (m, 1H, arom.); 7.0 (m, 1H, arom.); 7.18 (m,
1H, arom.); 7.39 (m, 1H, arom.). 31P NMR (300 MHz,
CDCl3): d (ppm): 32.3(s). FAB-MS (positive mode) m/z:
444 (M+-mal).
6H, phosphine). 31P NMR (300 MHz, CDCl3): d (ppm):
40.3(s). FAB-MS (positive mode) m/z: 679 (M+), 568
(M+-glut).
[Pd(glut)(Phox){P(CH2CH2CN)3}] (5c): (49% yield).
Anal. Calc. for C23H26N5O3PPd: C, 49.5; H, 4.7; N, 8.6.
Found: C, 49.7; H, 4.6; N, 8.7%. FT-IR (nujol mull
cmꢁ1): m(CN–Phox) 1646(vs); m(CO) 1578(vs); m(C„N)
[Pd(2,3-diBrmal)(Phox)(PPh3)] (4a): (68% yield).
Anal. Calc. for C31H23Br2N2O3PPd: C, 48.4; H, 3.0; N,
3.6. Found: C, 48.5; H, 3.1; N, 3.6%. FT-IR (nujol mull
cmꢁ1): m(CN–Phox) 1640(vs); m(CO) 1654(vs); m(PPh3)
1
2245(s). H NMR (300 MHz, CDCl3): d (SiMe4) (ppm):
1.95 (m, 2H glut); 2.26–2.40 (m, 6H, phosphine) 2.48–
2.61 (m, 4H, glut); 2.75–2.93 (m, 6H, phosphine); 3.76
(m, 2H, NCH2); 4.70 (m, 2H, OCH2); 7.00 (m, 1H, arom.);
7.10–7.25 (m, 2H, arom); 7.38 (m, 1H, arom). 31P NMR
(300 MHz, CDCl3): d (ppm): 31.4(s). FAB-MS (positive
mode) m/z: 445.1 (M+-glut).
1
534(m). H NMR (300 MHz, CDCl3): d (SiMe4) (ppm):
3.92 (m, 2H, NCH2); 4.66 (m, 2H, OCH2); 6.40 (m, 1H,
arom.); 6.65 (m, 1H, arom.); 6.92 (m, 1H, arom.); 7.25–
7.50 (m, 10H, 9PPh3 + 1H arom.); 7.76 (m, 6H, PPh3).
31P NMR (300 MHz, CDCl3): d (ppm): 41.9(s). FAB-MS
(positive mode) m/z: 768 (M+), 514 (M+-2,3-diBrmal).
[Pd(2,3-diBrmal)(Phox){P(4-F–C6H4)3}] (4b): (82%
yield). Anal. Calc. for C31H20Br2F3N2O3PPd: C, 45.3; H,
2.5; N, 3.4. Found: C, 45.4; H, 2.5, N, 3.4%. FT-IR (nujol
mull cmꢁ1): m(CN–Phox) 1642(vs); m(CO) 1658(vs); m(P(p-
2.3. Crystal structure determination of [{Pd(l-2,3-diBrmal)
(Phox)}2] (4), [Pd(2,3-diBrmal)(Phox)(PPh3)] (4a)
and [Pd(glut)(Phox)(PPh3)] (5a)
Crystals suitable for a diffraction study were prepared
by a slow diffusion of hexane into their CH2Cl2 solutions.
Crystallographic data are summarized in Table 1. Data col-
lection for 4 and 4a was performed at ꢁ173 °C on a Bruker
Smart CCD diffractometer with a nominal crystal to detec-
tor distance of 4.5 cm. Diffraction data were collected
based on a x scan run. A total of 2524 frames were col-
lected at 0.3° intervals and 10 s per frame. The diffraction
frames were integrated using the SAINT package [26] and
corrected for absorption with SADABS [27]. For 5a data col-
lection was performed at 293 K on a Nonius Kappa-CCD
single crystal diffractometer. Crystal-detector distance was
fixed at 35 mm, and a total of 122 images were collected
using the oscillation method, with scan angle per frame,
2° oscillation and 20 s exposure time per image. Data col-
lection strategy was calculated with the program COLLECT
[28]. Data reduction and cell refinement were performed
with the programs HKL DENZO and SCALEPACK [29].
1
C6H4F)3) 540(m). H NMR (300 MHz, CDCl3): d (SiMe4)
(ppm): 3.91 (m, 2H, NCH2); 4.71 (m, 2H, OCH2); 6.37 (m,
1H, arom.); 6.69 (m, 1H, arom.); 7.06 (m, 7H, 6H phos-
phine + 1H, arom. Phox); 7.29 (1H, arom.); 7.69 (m, 6H,
phosphine). 31P NMR (300 MHz, CDCl3): d (ppm):
39.6(s). FAB-MS (positive mode) m/z: 822 (M+), 568
(M+-2,3-diBrmal).
[Pd(2,3-diBrmal)(Phox){P(CH2CH2CN)3}]
(4c):
(72% yield). Anal. Calc. for C22H20Br2N5O3PPd: C, 37.8;
H, 2.9; N, 10.0. Found: C, 37.9; H, 3.0; N, 10.1%. FT-IR
(nujol mull cmꢁ1): m(CN–Phox) 1642(vs); m(CO) 1656(vs);
1
m(C„N) 2244(s). H NMR (300 MHz, CDCl3): d (SiMe4)
(ppm): 2.27 (m, 6H, phosphine); 2.83 (m, 6H, phosphine);
3.95 (m, 2H, NCH2); 4.63 (m, 2H, OCH2); 7.18–7.31 (m,
2H, arom.), 7.40–7.52 (m, 2H, arom.). 31P NMR
(300 MHz, CDCl3): d (ppm): 42.06(s). FAB-MS (positive
mode) m/z: 445 (M+-2,3-diBrmal).
[Pd(glut)(Phox)(PPh3)] (5a): (53% yield). Anal. Calc.
for C32H29N2O3PPd: C, 61.3; H, 4.7; N, 4.5. Found: C,
61.6; H, 4.8; N, 4.7%. FT-IR (nujol mull cmꢁ1): m(CN–
Phox) 1644(vs); m(CO) 1574(vs); m(PPh3) 534(m). 1H
NMR (300 MHz, CDCl3): d (SiMe4) (ppm): 1.24 (m, 2H,
glut); 1.63 (m, 2H, glut); 2.16 (m, 2H, glut); 3.86 (m, 2H,
NCH2); 4.68 (m, 2H, OCH2); 6.47 (m, 1H, arom.); 6.62
(m, 1H, arom.); 6.86 (m, 1H, arom.); 7.23 (m, 1H, arom.);
7.36 (m, 9H, phosphine); 7.82 (m, 6H, phosphine). 31P
NMR (300 MHz, CDCl3): d (ppm): 42.4(s). FAB-MS
(positive mode) m/z: 626 (M+), 514 (M+-glut).
The structures were solved by direct methods [30] and
refined by full-matrix least-squares techniques using aniso-
tropic thermal parameters for non-H atoms [30] (Table 1).
Hydrogen atoms were introduced in the calculated posi-
tions and refined during the last stages of the refinement.
3. Results and discussion
Under the conditions described in Section 2, [{Pd(l-
OH)(Phox)}2] reacts with several imidate-type ligands to
give dinuclear complexes 1–5 in which the imidate ligands
replace the bridging hydroxo group as presented in Scheme
1.
Both the precursor and the new complexes are quite
insoluble in the reaction media, so that just a change in
the suspension colour is observed. The new 2-(2-oxazoli-
nyl)phenyl) derivatives are air-stable yellow solids and their
infrared spectra show only one absorption around
730 cmꢁ1, as expected for the region of out-of-plane C–H
bending in disubstituted arenes. Also the characteristic
[Pd(glut)(Phox){P(4-F–C6H4)3}] (5b): (60% yield).
Anal. Calc. for C32H26F3N2O3PPd: C, 56.4; H, 3.9; N,
4.1. Found: C, 56.5; H, 4.0; N, 4.3%. FT-IR (nujol mull
cmꢁ1): m(CN–Phox) 1644(vs); m(CO) 1588(vs); m(P(p-
1
C6H4F)3) 536(m). H NMR (300 MHz, CDCl3): d (SiMe4)
(ppm): 1.32 (m, 2H, glut); 1.57 (m, 2H, glut); 2.21 (m, 2H,
glut); 3.84 (m, 2H, NCH2); 4.69 (m, 2H, OCH2); 6.36 (m,
1H, arom.); 6.65 (m, 1H, arom.); 6.90 (m, 1H, arom.);
7.05 (m, 6H, phosphine); 7.28 (m, 1H, arom.); 7.05 (m,

J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
1703
Table 1
Crystal data and structure refinement for compounds 4, 4a and 5a
4 ꢂ CH2Cl2
4a
5a ꢂ 1/2CH2Cl2
Empirical formula
Formula weight
Temperature (K)
C27H18Br4Cl2N4O6Pd2
1097.79
100(2)
C31H23Br2N2O3PPd
768.70
100(2)
C32.5H30ClN2O3PPd
653.90
293(2)
0.71073
˚
Wavelength (A)
0.71073
0.71073
Crystal system
Space group
Unit cell dimensions
monoclinic
P21/n
monoclinic
C2/c
monoclinic
C2/c
˚
a (A)
8.5336(3)
22.9656(9)
16.5248(7)
102.0920(10)
3166.7(2)
23.3725(11)
11.7735(6)
20.2239(10)
95.2240(10)
5542.0(5)
26.6920(5)
16.6670(4)
15.8240(3)
119.8430(10)
6106.2(2)
8
1.423
0.702
2648
0.60 ꢀ 0.02 ꢀ 0.02
1.51–27.52
ꢁ34 6 h 6 34
ꢁ19 6 k 6 21
ꢁ20 6 l 6 20
12355
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
Z
4
8
Dcalc (Mg mꢁ3
)
2.303
6.401
2088
1.843
3.649
3024
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm3)
0.08 ꢀ 0.07 ꢀ 0.04
0.27 ꢀ 0.25 ꢀ 0.15
h Range for data collection (°)
Index ranges
1.54–28.19
1.75–28.18
ꢁ11 6 h 6 11
ꢁ29 6 k 6 29
ꢁ20 6 l 6 20
36697
ꢁ30 6 h 6 30
ꢁ15 6 k 6 15
ꢁ26 6 l 6 26
31927
Reflections collected
Independent reflections [Rint
Refinement method
Data/parameters
Ra, Rwb [I > 2r(I)]
Ra, Rwb [all data]
Sc
]
7367 [0.0394]
full-matrix least-squares on F2
7367/425
R1 = 0.0315, wR2 = 0.0696
R1 = 0.0430, wR2 = 0.0816
0.794
6468 [0.0353]
full-matrix least-squares on F2
6468/361
R1 = 0.0375, wR2 = 0.0793
R1 = 0.0397, wR2 = 0.0804
1.202
6994 [0.0554]
full-matrix least-squares on F2
6994/362
R1 = 0.1056, wR2 = 0.3249
R1 = 0.1575, wR2 = 0.3495
2.103
2.691, ꢁ5.682
ꢁ3
˚
Maximum, minimum Dq (e A
)
2.518, ꢁ2.082
0.953, ꢁ0.386
P
P
a
b
c
R ¼ kF oj ꢁ jF Ck= jF oj.
P
P
2
2
1=2
Rw ¼ f ½wðF 2o ꢁ F 2c Þ ꢃ= ½wðF o2Þ ꢃg ; w ¼ 1=r2ðjF 2ojÞ.
P
2
1=2
S ¼ ½ ½wðF 2o ꢁ F 2c Þ ꢃ=ðNobs ꢁ NparamÞꢃ
.
H
N
O
N
O
O
N
N
O
- 2 H2O
+ 2 H-N^O
Pd
Pd
Pd
Pd
(CH3)2CO
O
O
H
O
N
O
N
+ 2PR3
O
O
O
O
O
Br
H-N^O =
NH
NH
NH
NH
NH
CH2Cl2
Br
O
O
O
O
mal (3)
O
phtal (2)
succ (1)
2,3-diBrmal (4) glut (5)
imidate = succ; R= Ph (1a) , (4-F-C6H4) (1b), (CH2CH2CN) (1c);
imidate = phtal; R= Ph (2a) , (4-F-C6H4) (2b), (CH2CH2CN) (2c);
imidate = mal; R= Ph (3a) , (4-F-C6H4) (3b), (CH2CH2CN) (3c);
imidate = 2,3-diBrmal; R= Ph (4a) , (4-F-C6H4) (4b), (CH2CH2CN) (4c);
imidate = glut; R= Ph (5a) , (4-F-C6H4) (5b), (CH2CH2CN) (5c).
PR3
Pd
2
N-imidate
O
N
Scheme 1.
C@N absorption of the cyclometallated ligand around
1630 cmꢁ1 is observed, shifted to lower frequencies com-
pared to the free ligand (1649 cmꢁ1) and partially over-
lapped with those two strong bands attributed to
imidato-carbonyl stretching in the range 1738–1720 and
1598–1562 cmꢁ1, respectively. According to the previously
reported data [10] the appearance of two bands in this
region suggests the coordination of one carbonyl group

1704
J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
to the metal as a part of an –NCO– bridging unit. Support
for the proposed dinuclearity of complexes 1–5 comes from
the FAB mass spectrometry, as can be implied by the m/z
values for the observed fragments. Spectra of the new
bridged compounds show a similar fragmentation pattern
which includes the peaks corresponding to [M]+, [M+-imi-
date]+ and [Pd(Phox)]+. The abundances of the signals
around the pattern ion are consistent with the natural iso-
topic ones.
reported oxazoline-derived l-chloro [31] and l-acetate
dimers [32], an anti-arrangement of identical donor atoms
is found, supporting the pseudohalide character of imidate
ligands. Also in common with the mentioned compounds
and our previously described structure [{Pd(l-
suc)(Phpy)}2] [15] is the so-called open-book geometry
accompanied by a rather short Pd(1)–Pd(2) distance of
˚
2.9279(4) A, within the generally accepted value for a Pd–
˚
Pd intramolecular interaction (<3.00 A). An interesting
Despite the low solubility in common solvents of some
of the new derivatives, further evidence of the proposed
coordination comes from the H NMR spectroscopy. It
structural aspect is that two hydrogens bonded to C22 ad
C8, respectively, point towards the centre of the phenyl
1
˚
rings: distance H22B-centroid (C1–C6) = 3.106 A; distance
˚
has been reported for the related complex [{Pd(l-OOC-
Me)(Phox)}2] that, as a consequence of its open-book
structure, each of the two methylene protons of the oxazo-
line ring is non-equivalent, displaying a set of three unre-
solved multiplets (ratio 1:2:1) [25]. In CDCl3 the new
binuclear complexes showed this behaviour for the oxazo-
line protons, which appeared in the spectra together with
the expected resonances of the imidate ligands (see Section
2). The preparation of single crystals of complex 4 suitable
for X-ray diffraction was also possible and unambiguously
confirmed the molecular structure. This is presented in
Fig. 1 together with selected bond distances and angles.
The unit cell of complex 4 contains two molecules. In
accordance with the geometries displayed by the previously
H8A-centroid (C14–C19) = 3.199 A, suggesting an interac-
tion between the rings of the two cyclometallated ligands.
We have recently developed methods for the conforma-
tional classification of eight-membered rings [33]. From
this perspective the Pd1–N2–C10–O2–Pd2–N4–C23–O5
ring displays a chair-chair conformation (CC = 0.9985;
TCC = 0.0015 for r = 10). Using the same Classification
method, the five-membered palladacycles Pd1–C1–C6–
C7–N1 and Pd2–C14–C19–C20–N3 exhibit almost planar
conformations for r = 10 (HC = 0.5095; E = 0.4905 and
HC = 0.5138; E = 0.4862, respectively).
The structure around the two palladium atoms may be
described as nearly planar, and their deviation from the
planar coordination has been quantified by measures of
improper torsion angles: 2.38° and ꢁ0.00° for Pd1 (square
pyramidal); ꢁ0.96° and ꢁ1.01° for Pd2 (tetrahedral) [16].
In the 2,3-dibromomaleimide ligand the C@O distance,
˚
1.228(5) and 1.232(5) A, is elongated in the bridged group
˚
with respect to the non-coordinated C@O, 1.208(5) A, in
both Pd atoms.
As expected, the reactions of the imidate-bridged
compounds against tertiary phosphines take place via
bridge-splitting to yield the mononuclear N-bonded imidate
derivatives [Pd(imidate)(Phox)(PR3)] presented in Scheme 1.
The yellow to orange air-stable solids display negligible
molar conductivity values, and their IR spectra show the
expected bands for the 2-(2-oxazolinyl)phenyl backbone,
together with those attributed to the incoming phosphine
ligand and just one strong carbonyl band around 1630
cmꢁ1, typical of N-bonded imidate ligands. The character-
isation in solid state was completed with the FAB mass
spectrometry, that shows fragments at [M+-imidate] in all
cases, being also possible to detect [M+] and [Pd(Phox)]+
for several compounds. The 1H and 31P NMR data of
the mononuclear complexes are collected in Section 2, the
latter consisting of singlets with chemical shifts in the usual
1
Fig. 1. ORTEP diagram of complex 4 with the atom numbering scheme;
range of Pd(II) complexes. With regard to the H NMR
thermal ellipsoids are drawn at the 50% propability level. Hydrogen atoms
spectra, they show the expected resonances of the cyclo-
metallated 2-phenyl-2-oxazoline, now with just two triplets
for the NCH2 and OCH2 protons in the 3.70–4.80 ppm
region, together with those signals attributed to the corre-
sponding imidate ligand and coordinated phosphine.
The structures of [Pd(2,3-diBrmal)(Phox)(PPh3)] (4a)
and [Pd(glut)(Phox)(PPh3)] (5a) have been confirmed by
X-ray diffraction study and are presented together with
˚
are omitted for clarity. Selected distances (A): Pd(1)–C(1) 1.976(4); Pd(1)–
N(1) 2.017(3); Pd(1)–N(2) 2.024(3); Pd(1)–O(5) 2.175(3); Pd(1)–Pd(2)
2.9279(4); Pd(2)–C(14) 1.980(4); Pd(2)–N(3) 2.024(4); Pd(2)–N(4) 2.030(4);
Pd(2)–O(2) 2.189(3). Selected angles (°): C(1)–Pd(1)–N(1) 81.08(6); C(1)–
Pd(1)–N(2) 92.68(15); N(1)–Pd(1)–N(2) 172.91(14); C(1)–Pd(1)–O(5)
175.64(14); N(1)–Pd(1)–O(5) 94.56(13); N(2)–Pd(1)–O(5) 91.66(12);
C(14)–Pd(2)–N(3) 81.42(16); C(14)–Pd(2)–N(4) 92.53(16); N(3)–Pd(2)–
N(4) 173.82(14); C(14)–Pd(2)–O(2) 173.71(15); N(3)–Pd(2)–O(2)
92.47(13); N(4)–Pd(2)–O(2) 93.61(13).

J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
1705
Fig. 2. ORTEP diagram of complex 4a. Thermal ellipsoids are drawn at
Fig. 3. ORTEP diagram of complex 5a. Thermal ellipsoids are drawn at
the 50% probability level. Hydrogen atoms are omitted for clarity.
50% probability. Hydrogen atoms are omitted for clarity. Selected
˚
Selected distances (A): Pd(1)–C(1) 2.027(3); Pd(1)–N(1) 2.068(3); Pd(1)–
˚
distances (A): Pd(1)–C(1) 2.046(12); Pd(1)–N(1) 2.062(10); Pd(1)–N(2)
N(2) 2.113(3); Pd(1)–P(1) 2.2438(9). Selected angles (°): C(1)–Pd(1)–N(1)
81.04(12); C(1)–Pd(1)–N(2) 171.23(12); N(1)–Pd(1)–N(2) 91.43(11); C(1)–
Pd(1)–P(1) 94.19(10); N(1)–Pd(1)–P(1) 174.12(8); N(2)–Pd(1)–P(1)
93.58(8).
2.091(10); Pd(1)–P(1) 2.246(3). Selected angles (°): C(1)–Pd(1)–N(1)
81.0(4); C(1)–Pd(1)–N(2) 171.4(4); N(1)–Pd(1)–N(2) 91.4(4); C(1)–Pd(1)–
P(1) 94.8(4); N(1)–Pd(1)–P(1) 175.5(3); N(2)–Pd(1)–P(1) 92.9(3).
In complex 4a, the C10–O2 and C13–O3 distances of
˚
the selected bond distances and angles in Figs. 2 and 3,
respectively. The coordination around the Pd atoms based
on measures of torsion angles is approximately planar with
slight tetrahedral distortion [16] (N1–C1–P1–Pd1 is 2.67°
and ꢁ1.14°; N2–P1–C1–Pd1 2.72° and ꢁ2.42°, respec-
tively). The displacement of the Pd atom from the mean
2,3-dibromomaleimide ligand are 1.204(4) and 1.209(4) A,
very close to the non-coordinated C@O distances in dinu-
clear complex 4 (1.208(5) A). In complex 5a those distances
˚
˚
are slightly higher: 1.216(16) and 1.227(16) A.
4. Conclusions
˚
coordination plane is 0.0524(57) and 0.1586(92) A
(rms = 0.0139 and 0.0017, respectively).
Twenty new imidate-palladium(II) complexes with 2-
phenyl-2-oxazoline acting as cyclometallated backbone
have been prepared and characterized by spectroscopic
techniques and single crystal X-ray diffraction analysis.
Imidate ligands exhibit two different coordination modes:
–NCO– bridging two Pd atoms or N-bonded. We enlarge
in this paper the range of imidate and phosphine systems
under study in comparison with our previous results, and
we present the first X-ray crystal structures of complexes
containing 2,3 dibromomaleimide (bonded as –NCO–
bridging group (4) and as N-bonded (4a)), as searched at
the Cambridge Structural Database (CSD) v. 5.28 updated
till August 2007. Preliminary results show that the new
complexes are active catalysts/precatalysts in Suzuki–
Miyaura cross-coupling reactions of aryl bromides with
aryl boronic acids. A comprehensive study will be reported
in due course.
The N–Pd–C angle in the orthometallated moiety,
around 81.0° in the three complexes, is similar to that
found in complexes containing the same ligand [25,31,32].
The structural analysis of complexes 4a and 5a confirms
the relative cis-position of the phosphine ligand and the
metallated carbon atom suggested by the NMR data. This
is the typical arrangement of the phosphine group in cyclo-
palladated complexes of the type [Pd(C^N)(phosphine)(X)]
(X = anionic monodentate ligand) due to the so-called
transphobia effect [34,35]. Following the classification of
Dance and Scudder [36] for PPh3 based on measures of tor-
sion angles M–P–Cipso–C, the conformation of Pd–PPh3
groups is described as no rotor for the new complexes, pre-
senting values T3 ꢁ T2 = 38.55°; T2 ꢁ T1 = 31.28° for 4a
and T3 ꢁ T2 = 22.17°; T2 ꢁ T1 = 88.30° for 5a, that differ
to those which would have the ideal rotor
(T1 = T2 = T3 = 44°).
As found for complexes 4, 4a and 5a also display almost
planar conformations in the five-membered palladacycles
Pd1–C1–C6–C7–N1 (HC = 0.5138; E = 0.4862 and
HC = 0.5114; E = 0.4886).
5. Supplementary data
CCDC 671662, 671663 and 671664 contain the supple-
mentary crystallographic data for 4, 4a and 5a. These data

1706
J.L. Serrano et al. / Polyhedron 27 (2008) 1699–1706
(b) S. Kannan, A.J. James, P.R. Sharp, Polyhedron 19 (2000) 155,
and references therein.
[19] R.A. Adrian, S. Zhu, D.R. Powell, G.A. Broker, E.R.T. Tiekink, J.A.
Walmsley, Dalton Trans. (2007) 4399.
[20] (a) U. Anandhi, T. Holbert, D. Lueng, P.R. Sharp, Inorg. Chem. 42
(2003) 1282;
can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
(b) P.R. Sharp, Dalton Trans. (2000) 2647.
[21] B. Longato, G. Bandoli, A. Dolmella, Eur. J. Inorg. Chem. (2004)
1092.
Acknowledgements
´
[22] (a) L. Dıez, P. Espinet, J.A. Miguel, Dalton Trans. (2001) 1189;
´
Financial support of this work by Direccion General de
´
´
´
(b) P. Espinet, C. Hernandez, J.M. Martın-Alvarez, J.A. Miguel,
´
Investigacion (project-CTQ2005-09231-C02-01/02) and
Inorg. Chem. 43 (2004) 843.
´
´
´
[23] (a) G. Sanchez, J. Garcıa, D. Meseguer, J.L. Serrano, L. Garcıa, J.
´
´
´
Fundacion Seneca de la Region de Murcia (00484/PI/04)
is gratefully acknowledged. We are grateful to the EPSRC
for funding (EP/DO78776/1) and the Royal Society
(I.J.S.F.).
´
´
Perez, G. Lopez, Dalton Trans. (2003) 4709;
´
´
´
´
(b) G. Sanchez, J. Vives, G. Lopez, J.L. Serrano, L. Garcıa, J. Perez,
Eur. J. Inorg. Chem. (2005) 2360;
(c) J. Perez, J.L. Serrano, J.M. Galiana, F.L. Cumbrera, A.L. Ortiz,
´
´
´
G. Sanchez, J. Garcıa, Acta Cryst. B63 (2007) 75.
[24] (a) J.L. Serrano, I.J.S. Fairlamb, G. Sa´nchez, L. Garc´ıa, J. Pe´rez, J.
References
´
Vives, G. Lopez, C.M. Crawforth, R.J.K. Taylor, Eur. J. Inorg.
Chem. (2004) 2706;
(b) J. Ruiz, V. Rodrıguez, G. Lopez, J. Casabo, E. Molins, C.
Miravitlles, Organometallics 18 (1999) 1177, and references therein;
(c) J. Ruiz, N. Cutillas, V. Rodrıguez, J. Sampedro, G. Lopez, P.A.
[1] I. Omae, Coord. Chem. Rev. 83 (1988) 137.
´
´
´
[2] A.C. Cope, R.W. Siekman, J. Am. Chem. Soc. 87 (1965) 3273.
[3] A. Kasahara, Bull. Chem. Soc. Jpn. 41 (1968) 1272.
[4] E.C. Constable, A.M.W. Cargill Thompson, T.A. Leese, D.G.F.
Reese, D.A. Tocher, Inorg. Chim. Acta 182 (1991) 93.
[5] D.L. Weaver, Inorg. Chem. 9 (1970) 2250.
´
´
Chalonner, P.B. Hitchcock, Dalton Trans. (1999) 2939;
´
´
´
´
(d) G. Sanchez, J.L. Serrano, J. Garcıa, G. Lopez, J. Perez, E. Molins,
Inorg. Chim. Acta 287 (1999) 37;
´
[6] M.A. Gutierrez, G.R. Newkome, J. Selbin, J. Organomet. Chem., 202
´
´
´
(e) G. Sanchez, J.L. Serrano, J. Perez, M.C. Ramırez de Arellano, G.
(1980) 341.
´
Lopez, E. Molins, Inorg. Chim. Acta 295 (1999) 136.
´
[7] J.M. Vila, M. Gayoso, M. Pereira, A. Romar, J.J. Fernandez, M.
[25] I.P. Smoliakova, K.J. Keuseman, D.C. Haagenson, D.M. Wellmann,
P.B. Colligan, N.A. Kataeva, A.V. Churakov, L.G. Kuz’mina, V.V.
Dunina, J. Organomet. Chem. 603 (2000) 86.
[26] SAINT, Version 6.22, Bruker AXS Inc.
[27] G.M. Sheldrick, SADABS, University of Go¨ttingen, 1996.
[28] COLLECT, Nonius BV, 1997–2000.
Thornton-Pett, J. Organomet. Chem. 401 (1991) 385.
[8] M.M. Mdleleni, J.S. Bridgewater, R.J. Watts, P.C. Ford, Inorg.
Chem. 34 (1995) 2334.
[9] C.A. Craig, R.J. Watts, Inorg. Chem. 28 (1989) 309.
[10] H. Adams, N.A. Bailey, T.N. Briggs, J.A. McCleverty, H.M.
Colquhoun, D.J. Williams, Dalton Trans. (1986) 813.
[29] DENZO-SCALEPACK: Z. Otwinowski, W. Minor, in: C.W. CarterJr.,
R.M. Sweet (Eds.), Methods in Enzymology, Macromolecular
Crystallography, Part A, vol. 276, Academic Press, 1997, pp. 307–326.
[30] G. M Sheldrick, SHELX-97 Programs for Crystal Structure Analysis
(Release 97-2), University of Go¨ttingen, 1998.
[31] D.L. Peterson, K.J. Keuseman, N.A. Kataeva, L.G. Kuz’mina,
J.A.K. Howard, V.V. Dunina, I.P. Smoliakova, J. Organomet. Chem.
654 (2002) 66.
´
´
´
[11] G. Sanchez, J.L. Serrano, M.A. Moral, J. Perez, E. Molins, G. Lopez,
Polyhedron 18 (1999) 3057.
[12] I. Aiello, A. Crispini, M. Ghedini, M. La Deda, F. Barigelletti, Inorg.
Chim. Acta 308 (2000) 121.
[13] (a) I. Omae, J. Organomet. Chem. 692 (2007) 2608;
(b) K. Gogula, D. Sames, Science 312 (2006) 67;
(c) J. Dupont, C.S. Consorte, J. Spencer, Chem. Rev. 105 (2005) 2527,
and references therein.
[14] I.J.S. Fairlamb, R.J.K. Taylor, J.L. Serrano, G. Sanchez, New J.
Chem. 30 (2006) 1695, and references therein.
[32] (a) O.N. Gorunova, K.J. Keuseman, B.M. Goebel, N.A. Kataeva,
A.V. Churakov, L.G. Kuz’mina, V.V. Dunina, I.P. Smoliakova, J.
Organomet. Chem. 689 (2004) 2382;
´
´
´
´
[15] J.L. Serrano, L. Garcıa, J. Perez, E. Perez, J. Vives, G. Sanchez, G.
Lopez, E. Molins, A.G. Orpen, Polyhedron 21 (2002) 1589.
[16] J. Perez, L. Garcıa, E. Perez, J.L. Serrano, J.F. Martınez, G. Sanchez,
(b) R.Y. Mawo, D.M. Johnson, J.L. Wood, I.P. Smoliakova, J.
Organomet. Chem. 693 (2008) 33.
´
´
´
´
´
´
´
´
´
[33] J. Perez, K. Nolsøe, M. Kessler, L. Garcıa, E. Perez, J.L. Serrano,
´
G. Lopez, A. Espinosa, M. Liu, F. Sanz, New J. Chem. 27 (2003)
Acta Cryst. B61 (2005) 585.
[34] J. Vicente, A. Arcas, D. Bautista, P.G. Jones, Organometallics 16
(1997) 2127.
1490.
´
´
[17] I.J.S. Fairlamb, A.R. Kapdi, A.F. Lee, G. Sanchez, G. Lopez,
´
´
´
J.L. Serrano, L. Garcıa, J. Perez, E. Perez, Dalton Trans. (2004)
3970.
[18] (a) S. Kannan, A.J. James, P.R. Sharp, Inorg. Chim. Acta 345 (2003)
8;
´
[35] J. Vicente, J.A. Abad, A.D. Frankland, M.C. Ramırez de Arellano,
Chem. Eur. J. 5 (1999) 3066.
[36] I. Dance, M. Scudder, Dalton Trans. (2000) 1579.