A systematic study on the synthesis, reactivity and structure of ortho-palladated aryloximes, including the first cyclopalladated aryloximato and iminoaryloxime complexes

Article abstract of DOI:10.1039/c1dt11445j

Complexes [Pd{C,N-Ar{C(Me)NOH}-2}(μ-Cl)]₂ (1) with Ar = C₆H₄, C₆H₃NO₂-5 or C ₆H(OMe)₃-4,5,6, were obtained from the appropriate oxime, Li₂[PdCl₄]

Full text of DOI:10.1039/c1dt11445j

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PAPER
A systematic study on the synthesis, reactivity and structure of
ortho-palladated aryloximes, including the first cyclopalladated aryloximato
and iminoaryloxime complexes†‡
Jose´ Vicente,*a Mar´ıa-Teresa Chicote,a Antonio Abella´n-Lo´peza and Delia Bautistab
Received 1st August 2011, Accepted 23rd September 2011
DOI: 10.1039/c1dt11445j
Complexes [Pd{C,N-Ar{C(Me) NOH}-2}(m-Cl)]2 (1) with Ar = C6H4, C6H3NO2-5 or C6H(OMe)3-
4,5,6, were obtained from the appropriate oxime, Li2[PdCl4] and NaOAc. They reacted with neutral
monodentate C-, P- or N-donor ligands (L), with [PPN]Cl ([PPN] = Ph3P
N PPh3), with Tl(acac)
(acacH = acetylacetone), or with neutral bidentate ligands NŸN (tetramethylethylenediamine (tmeda),
4,4¢-di-tert-butyl-2,2¢-bipyridine (tBubpy)) in the presence of AgOTf or AgClO4 to afford complexes of
the types [Pd{C,N-Ar{C(Me) NOH}-2}Cl(L)] (2), [PPN][Pd{C,N-Ar{C(Me) NOH}-2}Cl2] (3),
[Pd{C,N-Ar{C(Me) NOH}-2}(acac)] (4) or [Pd{C,N-Ar{C(Me) NOH}-2}(NŸN)]X (X = OTf,
ClO4) (5), respectively. Complexes 1 reacted with bidentate NŸN ligands in the presence of a base to
afford mononuclear zwitterionic oximato complexes [Pd{C,N-Ar{C(Me) NO}-2}(NŸN)] (6).
Dehydrochlorination of complexes 2 by a base yielded dimeric oximato complexes of the type
[Pd{m-C,N,O-Ar{C(Me) NO}-2}L]2 (7). The insertion of XyNC into the Pd–Caryl bond of complex 2
produced the mononuclear iminoaryloxime derivative [Pd{C,N-C( NXy)Ar{C(Me) NOH}-2}-
Cl(CNXy)] (8) which, in turn, reacted with [AuCl(SMe2)] to give [Pd{m-N,C,N-C( NXy)Ar-
{C(Me) NOH}-2}Cl]2 (9) with loss of XyNC. Some of these complexes are, for any metal, the first
containing cyclometalated aryloximato (6, 7) or iminoaryloxime (8, 9) ligands. Various crystal
structures of complexes of the types 2, 3, 6, 7, 8 and 9 have been determined.
Although the syntheses of various oxime palladacycles have
Introduction
been reported, their reactivity has been very scarcely studied,
which is surprising in view of the relevant catalytic activity of
such compounds. In this paper we report the synthesis and
characterization of new complexes of the types 1–9 shown in
Chart 1. Various complexes of the types 1 and 2, one an-
ionic derivative of type 32 and a few acetylacetonato3–5 and
cationic2,6,7 complexes of types 4 and 5, respectively, have been
previously reported; some of them were characterized by X-ray
crystallography,3,7–10 but others were partly characterized.4,11,12 Our
objectives in developing this work were (1) to prepare the first
family of well-characterized cyclopalladated complexes derived
from oximes; (2) to prepare cyclopalladated complexes of ace-
tophenone oxime and two of its derivatives containing substituents
on the aryl group with different electronic properties (NO2-5 and
(MeO)3-4,5,6), which are unprecedented; this has allowed us to
study the influence of these substituents on both, the reactivity
and structure of the corresponding complexes; and (3) to study
deprotonation and isocyanide insertion reactions on the oxime
complexes, which have allowed us to prepare the first aryloximato
(6, 7) and iminoaryloxime complexes (8, 9) of any metal. Both
include examples in which these ligands act as bridging or non-
bridging.
Since the beginning of this century, different authors, mainly
Na´jera et al., have been providing continuous reports on the
versatile and efficient use of oxime carbopalladacyles as precat-
alysts in a variety of C–C coupling processes, including Mizoroki–
Heck, Suzuki–Miyaura, Sonogashira, Stille, Hiyama or Ullmann-
type reactions. The use of oxime palladacycles as a source of
highly active palladium nanoparticles has allowed high-turnover
catalyzed Heck, as well as other homo- and cross-coupling
reactions. The subject has recently been reviewed.1
aGrupo de Qu´ımica Organometa´lica, Departamento de Qu´ımica In-
orga´nica, Universidad de Murcia, Apartado 4021, 30071, Murcia, Spain.
E-mail: jvs1@um.es, mch@um.es; Web: http://www.um.es/gqo/
bSAI, Universidad de Murcia, Apartado 4021, 30071, Murcia, Spain.
E-mail: dbc@um.es
† Dedicated to Professors Juan Fornie´s, Mar´ıa Pilar Garc´ıa and Antonio
Laguna on the occasion of their retirement.
‡ Electronic supplementary information (ESI) available: Additional exper-
imental and spectroscopic data. CCDC reference numbers 837023 (2d),
837028 (3), 837027 (3¢), 837029 (6¢b), 837024 (7b·H2O), 837025 (8¢¢) and
837026 (9·2CHCl3). For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c1dt11445j
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Results and discussion
Synthesis
The dinuclear chloro-bridged oxime complexes of type 1,
(Scheme 1, Pd{C,N-Ar{C(Me) NOH}-2}(m-Cl)]2 (Ar = C6H4
(1), C6H3NO2-5 (1¢), CH(OMe)3-4,5,6 (1¢¢)) were prepared in
good yield from generated in situ Li2[PdCl4], the appropriate
oxime and NaOAc in MeOH, following a modification of the
method first described by Onoue.11 We used a slight defect of
oxime in order to avoid the formation of by-products with N-
coordinated oxime or oximato ligands. This precaution proved
to be insufficient for the synthesis of 1¢ which formed along
with another species that we could not remove or identify.
However, we isolated 1¢ in the presence of a methanolic solution of
concentrated aqueous HCl because we suspected that the impurity
could result from a dehydrochlorination process favoured by the
greater acidity of the OH proton induced by the presence of the
NO2 group.
Chart 1 Types of aryloxime (1–5), aryloximato (6–7) and iminoaryloxime
(8–9) palladium complexes included in this paper. The numbering scheme
used in NMR assignments is depicted in 1.
The ability of the Pd–C bond to insert unsaturated molecules,
thought to be one of the key steps in many palladium-catalyzed
reactions, prompted us, more than one decade ago, to synthesize
ortho-functionalized arylpalladium complexes and to study their
reactivity towards unsaturated species with the hope that interest-
ing results could arise from the modified reactivity imposed by the
metal on both the pre-existing ortho-group and that resulting from
the insertion process, or from their joint reactivity favoured by their
close proximity. The fruit of this idea has been the preparation of
novel types of organometallic complexes and interesting organic
products.13 We report here the first insertion reaction of an
isocyanide into the C–Pd bond of an orthopalladated aryloxime.
We describe for the first time the use of [AuCl(SMe2)] as an
isocyanide scavenger. Its use allowed us to prepare, from complex
8, the dinuclear 9. All reported complexes could be used to prepare
heterocycles.
Scheme 1
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When CH2Cl2 suspensions of complexes of type 1 were treated
with monodentate neutral C-, N- or P-donor ligands L in
1 : 2 molar ratio or in excess (L = dmso), solutions formed
almost immediately from which the corresponding mononuclear
derivatives of type 2 (Scheme 1, [Pd{C,N-Ar{C(Me) NOH}-
Because of the scarce donor ability of the dmso ligand in
complex 2e, this was obtained in equilibrium with 1, which
required several operations before the pure product could be
isolated (50% yield). This complex forms as an equimolar mixture
of two isomers containing the S-coordinated ligand trans to C or N,
respectively. Complex 2¢b and some others (3¢, 3¢¢, 4¢¢, 5¢a¢, 6a, 6¢a,
7b, 7c, 7¢a, 7¢b, 8¢¢, Schemes 1–2) crystallized with various amounts
of water, in spite of being heated in a vacuum oven. The water
content deduced from their elemental analyses was confirmed in all
cases by their 1H NMR spectra or X-ray crystallography (7b·H2O).
The low isolated yield of complex 2¢c (62%) can be attributed to
its partial dehydrochlorination to give 7¢c (see below), facilitated
by the enhanced acidity of the OH group in the nitro-substituted
oxime derivatives.
The reaction of the dinuclear complexes of type 1 with [PPN]Cl
also caused bridge splitting and formation of anionic com-
plexes [PPN][Pd{C,N-Ar{C(Me) NOH}-2}Cl2] (Ar = C6H4 (3),
C6H3NO2-5 (3¢), CH(OMe)3-4,5,6 (3¢¢)); similarly, acetylacetonato
derivatives [Pd{C,N-Ar{C(Me) NOH}-2}(acac)] (Ar = C6H4
(4), C6H3NO2-5 (4¢), CH(OMe)3-4,5,6 (4¢¢)) were isolated in good
yields from the 1 : 2 reactions of 1 with Tl(acac). Using Ag(acac)
instead of Tl(acac) produced the same results.
t
2}Cl(L)] (Ar = C6H4, L = XyNC (2a), BuNC (2b), PTol3 (2c),
g-pic (2d); Ar = C6H3NO2-5, L = XyNC (2¢a), tBuNC (2¢b), PTol3
(2¢c), g-pic (2¢d); Ar = CH(OMe)3-4,5,6, L = XyNC (2¢¢a), tBuNC
(2¢¢b), PPh3 (2¢¢c¢)) were isolated in good yield. The synthesis of 2a
required slow addition of the ligand because, otherwise, different
amounts of 8 (see below, Scheme 2) formed as a consequence of
XyNC insertion in the Pd–Caryl bond. Alternatively, 2a can be
obtained from 2d, upon replacing g-picoline with XyNC. The C-
and P-donor ligands must be trans to the oxime N atom because of
the high C/C and C/P transphobia.14 This has been the geometry
found in similar complexes.3,10,15 In the reported orthopalladated
aryl oxime complexes containing pyridine or some of its derivatives
this ligand is also trans to the oxime N atom.7,9
The reaction of complexes of type 1 with neutral bidentate NŸN
ligands (tBubpy, tmeda), in the presence of silver salts or bases,
produced different results depending on the auxiliary reagent.
Thus, in the presence of AgOTf or AgClO4, a suspension formed
from which cationic aryloxime complexes of type 5 [Pd{C,N-
Ar{C(Me) NOH}-2}(NŸN)]X (Ar = C6H4, X = OTf, NŸN =
t
tBubpy (5a), tmeda (5b), Ar = C6H3NO2-5, NŸN = Bubpy, ClO4
(5¢a¢)) could be isolated in good yield after removing the insoluble
AgCl. However, in the reaction of 1 with NŸN ligands and
KtBuO (1 : 2 : 2, QB in Scheme 2), apart from bridge splitting
and removal of the chloro ligand as above, deprotonation of the
oxime function by the base occurred producing oximato complexes
t
[Pd{C,N-Ar{C(Me) NO}-2}(NŸN)] (Ar = C6H4, NŸN = Bubpy
t
(6a), Ar = C6H3NO2-5, NŸN = Bubpy (6¢a), tmeda (6¢b)) and
tBuOH, which is not surprising in view of the well known
enhanced acidity of oximes upon coordination.16 Similarly, when
complexes of type 2 were treated with a base (QB = NaOAc, NaH,
KtBuO), oxime deprotonation and QCl precipitation took place
to give aryloximato complexes [Pd{m-C,N,O-Ar{C(Me) NO}-
t
2}L]2 (Ar = C6H4, L = XyNC (7a), BuNC (7b), PTol3 (7c), Ar =
t
C6H3NO2-5, L = XyNC (7¢a), BuNC (7¢b), PTol3 (7¢c); Ar =
CH(OMe)3-4,5,6, L = XyNC (7¢¢a), tBuNC (7¢¢b) (Scheme 2). The
tetracoordination ofpalladium is attained bymeans of the oximato
ligand acting as a N,O-bridging ligand.
The HRMS of 7¢a·H2O agrees to 2.52 ppm with the calculated
exact mass of the dimeric anhydrous product but its carbon
content found in the elemental analysis is a bit low (47.55 vs.
48.07%). Since we could not assess its purity by NMR due to its
insolubility, we reacted it with a solution of HCl in CH2Cl2 (excess)
and confirmed that the NMR of the crude reaction product
coincides with that of pure 2¢a. Compound 7b or 7¢¢b was also
prepared by reaction of the acetylacetonato complex 4 or 4¢¢ with
tBuNC in a 1 : 1 molar ratio. This reaction suggests that the oxime
function can only coexist with the strongly basic acac ligand when
it is chelating; otherwise, deprotonation takes place to give acacH
along with an oximato complex that dimerizes to achieve the
tetracoordination at palladium. As far as we are aware complexes
Scheme 2 Synthesis of complexes 6–9. QB = NaOAc, NaH, KtBuO.
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of the types 6 and 7 are, for any metal, the first isolated complexes
containing a cyclometallated aryloximato ligand, although one
such species has been claimed to be an intermediate in the
efficient degradation of thiophosphate pesticides catalyzed by
palladium aryloxime metallacycles.17 Additionally, a trinuclear
aryloximato palladium complex has been described,9 but it is not
a cyclometallated species.
complex [Pd{C,N-C( NXy)C6H4{C(Me) NOH}-2}Cl(SMe2)]
resulting from bridge splitting in 9 by the dimethyl sulfide present
in solution. This is why the isolation of pure 9 required a tedious
work up (see Experimental), which explains the low isolated
yield. Probably, this reaction occurs because an 8 ꢀ 9 + XyNC
equilibrium exists giving a very small amount of XyNC, which,
upon reaction with [AuCl(SMe2)], would give [AuCl(CNXy)] and
9. As far as we are aware, the abstraction of an isocyanide ligand
by this means is unprecedented.
The reaction of 8¢¢ with [AuCl(SMe2)] failed to give 9¢¢, homol-
ogous of 9 with the trimethoxy substituted arene. We interpret
this result assuming that the 8¢¢ ꢀ 9¢¢ + XyNC equilibrium can
not occur because formation of the dimer 9¢¢ would require the
Xy group to be folded towards MeO-6 group and this is sterically
hindered. In fact, the crystal structure of 8¢¢ shows the iminoacyl
xylyl group folded towards the XyNC ligand to avoid the above
mentioned repulsion. In the case of 8 a NOESY NMR spectrum
allows us to unequivocally establish that the iminoacyl xylyl group
is folded towards the aryl group.
In an attempt to obtain iminoaryloxime complexes [Pd{C,N-
C( NXy)Ar{C(Me) NOH}-2}Cl(CNXy)] (Ar = C6H4 (8),
C6H(OMe)3-4,5,6 (8¢¢), Scheme 2) we reacted the corresponding
complexes 1 with two equivalents of XyNC per Pd with the
hope that they would produce bridge splitting and insertion in
the Pd–Caryl bond. However, a mixture formed that we could not
resolve. It was shown by NMR to contain complexes of types
1, 2, and 8, along with polyinsertion products. Complexes 8 and
8¢¢ could be obtained, at room temperature, from the reaction of
the appropriate complex 2 with excess XyNC (8, 1 : 1.27) or using
the stoichiometric amount (8¢¢). The moderate (58–69%) yields
achieved can be explained because polyinsertion products start to
form before the reaction is complete and thus, various operations
were needed to separate the desired complex of type 8 from the
accompanying impurities. The homologous reactions between 2¢a
X-Ray crystal structures
The crystal structures of complexes 2d (Fig. 1), 3 (Fig. 2), 3¢
(Fig. 3), 6¢b (Fig. 4), 7b·H2O (Fig. 5), 8¢¢ (Fig. 6) and 9·2CHCl3
(Fig. 7) have been determined by X-ray diffraction. As complexes
6, 7 and 8, 9 are, respectively, the first aryloximato and iminoary-
loxime metal complexes, the crystal structures of 6¢b or 7b·H2O
and 8¢¢ or 9·2CHCl3 offer the first structural data of these types of
complexes of any metal.
t
and XyNC (1 : 1) or between 2b, 2¢b or 2¢¢b and BuNC (1 : 1)
did not produce the expected complexes of type 8 which could be
attributed, respectively, to the electron withdrawing ability of the
t
nitroaryl group in 2¢a and to the +I electronic effect of the Bu
group of the isocyanide, both factors disfavouring the insertion of
the isocyanide which is facilitated when the aryl carbon bonded
to palladium and the isocyanide carbon bear formal negative and
positive charges, respectively.18,19 Although some of these reactions
do not work at all, those of 2b and 2¢¢b with tBuNC (1 : 1) produced
the Pd(I) complex [Pd2Cl2(CNtBu)4] among other unidentified
products.
Based on kinetic studies19–21 proving that the insertion of
isocyanide into s-Pd–C bonds occurs by intramolecular migratory
insertion of the s-C donor ligand into the previously coordinated
isocyanide, we refluxed complex 2a in toluene with the hope of
obtaining any of the dinuclear iminoacyl complexes resulting from
insertion followed by dimerization with chloro22 or iminoacyl
bridging23 ligands; both processes are known. However, 2a was
recovered unchanged and none of the expected complexes, namely
[Pd{C,N-C( NXy)C6H4{C(Me) NOH}-2}(m-Cl)]2 or [Pd{m-
N,C,N-C( NXy)C6H4{C(Me) NOH}-2}Cl]2 (9), was even de-
tected by 1H NMR. Similarly, not even trace amounts of the
complex [Pd{C,N,-C( NXy)C6H4{C(Me) NOH}-2}Cl(g-pic)]
were detected after refluxing for 2 h solutions containing equimo-
lar amounts of 2a and g-picoline in CHCl3 or in toluene, in spite
of the fact that the insertion process has been said to be assisted
by donor species.21,24
However, complex 9 could be obtained upon abstracting the
XyNC ligand present in 8 by reacting it with [AuCl(SMe2)] (1 : 1) in
CHCl3 (Scheme 2). The reaction produced [AuCl(CNXy)] and the
dinuclear complex 9 in which two bridging iminoacyl fragments
(and not the chloro ligands) complete the tetracoordination of
the palladium centers. The reaction seems to be an equilibrium
since various 1H NMR spectra of the reaction mixture mea-
sured in the period 0–2 h showed the invariable presence of 9
and [AuCl(CNXy)], along with small amounts of the starting
compounds and an unidentified species that is likely to be the
Fig. 1 Left: Thermal ellipsoid representation plot (50% probability)
◦
˚
of complex 2d. Selected bond lengths (A) and angles ( ): Pd(1)–C(1)
1.9873(16), Pd(1)–N(1) 1.9945(13), Pd(1)–N(2) 2.0358(13), Pd(1)–Cl(1)
2.4367(4), N(1)–C(7) 1.290(2), N(1)–O(1) 1.3887(17), C(1)–C(2) 1.419(2),
C(2)–C(7) 1.467(2); C(1)–Pd(1)–N(1) 80.00(6), C(1)–Pd(1)–N(2) 93.74(6),
N(1)–Pd(1)–Cl(1) 90.29(4), N(2)–Pd(1)–Cl(1) 96.01(4). Right: Chains
along the c axis in 2d formed through C–H ◊ ◊ ◊ O hydrogen bonds.
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Fig. 2 Thermal ellipsoid representation plot (50% probability) of
˚
the anion of complex 3. Selected bond lengths (A) and angles
(◦): Pd(1)–C(1) 1.977(3), Pd(1)–N(1) 1.989(2), Pd(1)–Cl(1) 2.2775(7),
Pd(1)–Cl(2) 2.4364(7); C(1)–Pd(1)–N(1) 80.37(11), C(1)–Pd(1)–Cl(1)
93.57(9), N(1)–Pd(1)–Cl(2) 90.53(7), Cl(1)–Pd(1)–Cl(2) 95.48(3).
Fig. 4 Up: Thermal ellipsoid representation plot (50% probability)
◦
˚
of complex 6¢b. Selected bond lengths (A) and angles ( ): Pd(1)–C(1)
2.0078(18), Pd(1)–N(1) 2.0199(16), Pd(1)–N(2) 2.1800(16), Pd(1)–N(3)
2.1349(16), N(1)–O(1) 1.301(2), C(1)–C(2) 1.421(3), C(2)–C(7) 1.449(3),
N(1)–C(7) 1.320(2); C(1)–Pd(1)–N(1) 80.74(7), C(1)–Pd(1)–N(3) 99.79(7),
N(3)–Pd(1)–N(2) 82.76(6), N(1)–Pd(1)–N(2) 97.06(6). Down: Layers
parallel to the ab plane in 6¢b formed through C–H ◊ ◊ ◊ O and C–H ◊ ◊ ◊ N
hydrogen bonds.
Fig. 3 Left: Thermal ellipsoid representation plot (50% probabil-
˚
ity) of the anion of complex 3¢. Selected bond lengths (A) and
angles (◦): Pd(1)–C(1) 1.981(2), Pd(1)–N(1) 2.001(2), Pd(1)–Cl(1)
2.2958(7), Pd(1)–Cl(2) 2.4371(7), N(1)–O(1) 1.378(3), C(1)–C(2) 1.426(4),
C(2)–C(7) 1.469(4), N(1)–C(7) 1.299(3); C(1)–Pd(1)–N(1) 80.54(10),
C(1)–Pd(1)–Cl(1) 92.97(8), N(1)–Pd(1)–Cl(2) 89.03(6), Cl(1)–Pd(1)–Cl(2)
97.58(2). Right: C–H ◊ ◊ ◊ Cl hydrogen bond interactions in 3¢ giving discrete
cation–anion entities.
˚
A) suggests some electron delocalization over the C(2)–C(7)–
N(1)–O(1) moiety. This is not observed in the dinuclear oximato
complex 7b·H2O in which the N,O–bridging role of the oximato
ligand justifies the lengthening of the N(1)–O(1) bond distances
to values intermediate between those in oxime and non-bridging
˚
oximato ligands (1.3512(18) and 1.3558(17) A).
The bond distances found in the oxime derivatives 2 and 3 are
similar to their homologous in ten crystal structures of aryloxime
palladium complexes previously reported.3,7,8,25 The structures of
the oxime (2d, 3, 3¢) and oximato (6¢b, 7b·H2O) complexes display
many commonalities but, while the oxime derivatives show N(1)–
The Pd–Cl bond distances trans to carbon in 3 and 3¢ (2.4364(7)
˚
and 2.4371(7) A, respectively) are longer than those trans to
˚
nitrogen (2.2775(7) and 2.2958(7) A, respectively), as expected
for the greater trans influence of carbon with respect to nitrogen.
˚
The same reason justifies the longer Pd–N(2) (2.1800(16) A) with
˚
˚
O(1) bond distances (1.378(3)–1.391(3) A) indicative of a N–O
respect to Pd–N(3) (2.1349(16) A) in 6b. The five-membered ring
single bond, in the neutral oximato complex 6¢b an appreciable
shortening of this distance is observed (1.301(2) A). This, along
in complex 7b·H2O is folded around the O(1) ◊ ◊ ◊ O(2) axis in such
a way that the two planar subunits form a torsion angle of 59.3◦.
The Pd–N bond distances in 7b·H2O are rather long (2.0296(14),
˚
with the lengthening of N(1)–C(7) (1.320(2) vs. 1.290(2)–1.299(3)
˚
˚
2.0334(13) A) caused by the great trans influence of the isocyanide
A) and the shortening of C(2)–C(7) (1.449(3) vs. 1.466(4)–1.469(4)
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Fig. 5 Thermal ellipsoid representation plot (50% probability) of
◦
˚
complex 7b·H2O. Selected bond lengths (A) and angles ( ): Pd(1)–C(1)
1.9909(18), Pd(2)–C(21) 1.9867(16), Pd(1)–N(1) 2.0296(14), Pd(2)–N(2)
2.0334(13), Pd(1)–O(2) 2.1191(12), Pd(2)–O(1) 2.1395(12), Pd(1)–C(9)
1.9510(18), Pd(2)–C(29) 1.9501(17), N(1)–O(1) 1.3512(18), N(2)–O(2)
1.3558(17), N(1)–C(7) 1.303(2), N(2)–C(27) 1.297(2), C(2)–C(7) 1.467(2),
C(22)–C(27) 1.465(2), C(1)–C(2) 1.420(2), C(21)–C(22) 1.419(2);
C(1)–Pd(1)–N(1) 80.63(7), C(21)–Pd(2)–N(2) 80.67(6), C(9)–Pd(1)–C(1)
94.35(7), C(29)–Pd(2)–C(21) 93.26(7), N(1)–Pd(1)–O(2) 97.32(5),
N(2)–Pd(2)–O(1) 96.35(5), C(9)–Pd(1)–O(2) 87.69(6), C(29)–Pd(2)–O(1)
89.87(6), C(7)–N(1)–Pd(1) 117.56(11), C(27)–N(2)–Pd(2) 117.50(11),
O(1)–N(1)–Pd(1)
123.44(10),
O(2)–N(2)–Pd(2)
124.30(10),
N(1)–O(1)–Pd(2) 108.03(9), N(2)–O(2)–Pd(1) 110.41(9), C(2)–C(1)–Pd(1)
112.68(12), C(22)–C(21)–Pd(2) 112.48(12), C(1)–C(2)–C(7) 115.88(15),
C(21)–C(22)–C(27) 116.21(14), N(1)–C(7)–C(2) 113.23(15), N(2)–C(27)–
C(22) 113.10(14).
Fig. 6 Up: Thermal ellipsoid representation plot (50% probability) of
◦
˚
complex 8¢¢. Selected bond lengths (A) and angles ( ): Pd(1)–C(9) 1.989(2),
Pd(1)–C(19) 1.941(2), Pd(1)–N(1) 2.0689(19), Pd(1)–Cl(1) 2.4406(6),
N(1)–C(7) 1.279(3), C(2)–C(7) 1.483(3), C(1)–C(2) 1.403(3), C(1)–C(9)
1.480(3), N(1)–O(1) 1.390(2), N(2)–C(9) 1.260(3); C(19)–Pd(1)–C(9)
90.50(9), C(9)–Pd(1)–N(1) 84.74(8), C(19)–Pd(1)–Cl(1) 96.55(7),
N(1)–Pd(1)–Cl(1) 88.30(5), C(7)–N(1)–O(1) 114.52(19), C(7)–N(1)–Pd(1)
128.82(15), O(1)–N(1)–Pd(1) 115.72(14), N(1)–C(7)–C(2) 117.2(2),
C(1)–C(9)–Pd(1) 110.65(15), C(9)–N(2)–C(11) 122.2(2). Down: Packing
diagram of 8¢¢ showing a zig–zag chain along the c axis.
˚
ligand. In the dimer 9·2CHCl3 the Pd(1)–Pd(2) distance 3.201 A is
slightly shorter than twice the van der Waals radius of palladium
˚
(3.26 A).
The oxime chloro complexes (2d, 3¢, 8¢¢ and 9·2CHCl3) show
intramolecular O–H ◊ ◊ ◊ Cl hydrogen bonds. Additionally, classical
O–H ◊ ◊ ◊ O (7b·H2O) or non-classical intra C–H ◊ ◊ ◊ Cl (in 3¢ giving
discrete entities cation–anion (Fig. 3, right)) or intermolecular C–
H ◊ ◊ ◊ O (2d, chains along c axis (Fig. 1, right), 6¢b, 7b·H2O) or
C–H ◊ ◊ ◊ N (6¢b) hydrogen bonds are also present, which in the case
of 8¢¢ cause the molecules to pack in a zig–zag chain along the c axis.
In the oxime chloro complexes 6¢b the nonclassical intermolecular
C–H ◊ ◊ ◊ O and C–H ◊ ◊ ◊ N hydrogen bond links the molecules into
layers parallel to the ab plane (Fig. 4, below).26
Experimental
We describe below the syntheses of only one complex of each
type, and leave for the ESI‡ the detailed syntheses of all the
remaining complexes. Although complexes 1,11 2b12 and 44 were
previously reported, we also include them in the ESI‡ because
their characterization was incomplete.
Although complexes 8 and 9 could be described as carbenes, the
crystal structures of 8¢¢ and 9 do not support such an assignment.
2
˚
The C(aryl)–C(sp ) bond distances (1.480(3) A in 8¢¢, 1.480(5) and
2
˚
1.482(5) A in 9) are close to the standard C(aryl)–C(sp ) overall
value (1.488 A) and the C N bond distances are even shorter
than the standard C(sp2) N(3) value (1.316 A; 1.260(3) A in 8¢¢,
General
27
˚
27
˚
˚
When not stated, the reactions were carried out without precau-
tions to exclude light or atmospheric oxygen or moisture. The
solvents were distilled before use. Melting points were determined
on a Reichert apparatus and are uncorrected. Elemental analyses
were obtained with a Carlo Erba 1106 microanalyzer. The molar
conductivities were measured with a CRISON micro CM 2200
˚
1.279(4), 1.287(4) A in 9), which confirms they are iminobenzoyl
derivatives.
All complexes were characterized by NMR (when soluble) and
IR spectroscopies (see discussion in the ESI‡ and data in the
Experimental section).
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solution of HCl (0.5 mL) in MeOH (3 mL). After stirring the
suspension for 15 min, H2O (50 mL) was added. The resulting
orange suspension was centrifuged, the solid was washed with
diluted HCl (20 mL, 0.3 M), centrifuged again and decanted. The
solid was stirred with a mixture of acetone and Et2O (1 : 20, 3
¥ 21 mL), filtered and dried with a nitrogen stream to give pale
◦
1
orange 1¢. Yield: 1180 mg, 98%. Mp > 250 C. H NMR (400
◦
3
MHz, CD3CN, 25 C): d 2.30 (s, 3 H, Me8), 7.38 (d, H3, JHH
=
8 Hz), 7.82 (d, H6, 3JHH = 8 Hz), 7.98 (s, H4), 10.58 (s, 1 H, OH).
(400 MHz, dmso-d6, 20 ◦C, two isomers in 3.5(M):1(m) molar
ratio): d 2.34 (br s, 3 H, Me8M), 2.38 (br s, 3 H, Me8m), 7.52 (d, 1H,
ArM, JHH = 7 Hz), 7.61 (br s, 1H, Arm), 7.93 (d, 1H, ArM, JHH
3
3
= 7 Hz), 8.03 (br s, 1H, Arm), 8.28 (s, 1H, ArM), 8.72 (br s, 1H,
Arm), 10.38 (br s, 1 H, OHm), 10.91 (s, 1 H, OHM). 13C{ H} NMR
1
◦
(100 MHz, CD3CN, 25 C): d 12.5 (Me8), 122.2 (CH4), 127.29
(CH3 or 6), 127.33 (CH3 or 6), 147.8 (C5), 150.6 (C2), 152.7 (C1), 168.2
(C7). IR (cm-1): n(OH) 3444, nasym(NO2) 1525. Anal. Calcd for
C8H7ClN2O3Pd: C, 29.93; H, 2.20; N, 8.73. Found: C, 29.69; H,
1.99; N, 8.47.
Fig.
7
Thermal ellipsoid representation plot (50% probability)
Synthesis of [Pd{C,N-C6H4{C(Me) NOH}-2}Cl(c-pic)] (2d).
To a suspension of 1 (539 mg, 0.98 mmol) in CH2Cl2 (5 mL)
was added g-pic (190 mL, 1.95 mmol). A solution immediately
formed which was stirred at room temperature for 1.5 h and filtered
through a short pad of Celite. The solution was concentrated under
vacuum to 1 mL and Et2O (15 mL) was added. The resulting
suspension was stirred for 15 min, filtered, and the solid collected
was washed with Et2O (3 ¥ 2 mL) and dried by suction to give 2d
as a pale yellow solid. Yield: 649 mg, 90%. Mp: 169 ◦C. 1H NMR
(400 MHz, CDCl3, 25 ◦C): d 2.28 (s, 3 H, Me8), 2.47 (s, 3 H, Me,
g-pic), 6.27 (dd, H6, 3JHH = 8 Hz, 4JHH = 1 Hz), 6.92 (td, H4 or 5, 3JHH
= 8 Hz, 4JHH = 1 Hz), 7.07 (td, H4 or 5, 3JHH = 8 Hz, 4JHH = 1 Hz), 7.12
(dd, H3, 3JHH = 8 Hz, 4JHH = 1 Hz), 7.28 (apparent d, meta-CH, pic,
3JHH = 6 Hz), 7.28 (apparent d, orto-CH, pic, 3JHH = 6 Hz), 10.10 (s,
of complex 9·2CHCl3 (solvent omitted for clarity). Selected bond
lengths (A) and angles (◦): Pd(1)–Pd(2) 3.2068(4), Pd(1)–C(9)
˚
1.942(3), Pd(2)–C(29) 1.941(3), Pd(1)–N(1) 2.042(3), Pd(2)–N(21)
2.028(3), Pd(1)–Cl(1) 2.4318(9), Pd(2)–Cl(2) 2.4205(9), Pd(1)–N(22)
2.058(3), Pd(2)–N(2) 2.048(3), N(1)–C(7) 1.293(4), N(21)–C(27)
1.285(5), C(2)–C(7) 1.472(5), C(22)–C(27) 1.485(5), C(1)–C(2) 1.404(5),
C(21)–C(22) 1.408(5), N(2)–C(11) 1.454(4), N(22)–C(31) 1.449(4);
N(1)–O(1) 1.395(4), N(21)–O(21) 1.393(4), N(2)–C(9) 1.279(4),
N(22)–C(29) 1.287(4); C(9)–Pd(1)–N(1) 85.52(13), C(9)–Pd(1)–N(22)
89.96(12), N(1)–Pd(1)–Cl(1) 88.16(8), N(22)–Pd(1)–Cl(1) 96.34(8), N(1)–
Pd(1)–Pd(2) 118.22(8), C(9)–Pd(1)–Pd(2) 62.87(10), N(22)–Pd(1)–Pd(2)
59.32(8), Cl(1)–Pd(1)–Pd(2) 115.38(2), C(29)–Pd(2)–N(21), 86.31(13),
C(29)–Pd(2)–N(2) 90.58(12), N(21)–Pd(2)–Cl(2) 90.01(9), N(2)–Pd(2)–
Cl(2) 93.53(8), C(29)–Pd(2)–Pd(1) 63.38(10), N(21)–Pd(2)–Pd(1)
121.93(8), N(2)–Pd(2)–Pd(1) 59.42(8), Cl(2)–Pd(2)–Pd(1) 112.95(3),
C(7)–N(1)–Pd(1) 128.9(2), C(27)–N(21)–Pd(2) 130.0(2), C(9)–N(2)–Pd(2)
119.0(2), C(29)–N(22)–Pd(1) 119.1(2), N(1)–C(7)–C(2) 118.4(3),
N(21)–C(27)–C(22) 119.1(3).
◦
1 H, OH). 13C{ H} NMR (50 MHz, CDCl3, 25 C): d 11.0 (Me8),
21.2 (Me, g-pic), 124.8 (CH, Ar), 125.1 (CH, Ar), 126.5 (meta-
CH, pic), 128.9 (CH4 or 5), 131.1 (CH3 or 6), 143.6 (C2), 150.6 (para-C,
pic), 152.3 (ortho-CH, pic), 153.1 (C1), 165.4 (C7). IR (cm-1): n(OH)
3147, n(C N) 2195. Anal. Calcd for C14H15ClN2OPd: C, 45.55; H,
4.10; N, 7.59. Found: C, 45.33; H, 4.00; N, 7.59. Crystals suitable
for an X-ray diffraction study were grown by slow diffusion of
Et2O into a solution of 2d in CH2Cl2.
1
conductimeter on ca. 5 ¥ 10-4 M solutions in acetone. The IR spec-
tra were recorded on a Perkin-Elmer 16 F PC FT-IR spectrometer
with Nujol mulls between polyethylene sheets. The NMR spectra
were recorded in Varian 200, 300 or 400 NMR spectrometers. The
NMR assignments were performed, in some cases, with the help
of APT, HMQC and HMBC experiments. The atom numbering
used in the NMR assignments is shown in Chart 1. The oximes
ArC(Me) NOH [Ar = Ph, C6H4NO2-4, C6H2(OMe)3-3,4,5)] were
prepared from the appropriate ketone ArC( O)Me, NH2OH·HCl
and NaOAc·3H2O following a previously reported method.28
[AuCl(SMe2)]29 was prepared from Na[AuCl4] and SMe2.
Synthesis of [PPN][Pd{C,N-C6H4{C(Me) NOH}-2}Cl2] (3).
To a suspension of 1 (65 mg, 0.12 mmol) in CH2Cl2 (5 mL) was
added [PPN]Cl (141 mg, 0.24 mmol). The resulting solution was
stirred for 2 h, filtered through a short pad of Celite, concentrated
under vacuum to 0.5–1 mL, and Et2O (15 mL) was added. A
suspension formed which was filtered and the solid collected was
washed with Et2O (3 ¥ 2 mL) and dried by suction to give pale tan
3. Yield: 167 mg, 83%. Mp: 177 ◦C. 1H NMR (400 MHz, CDCl3,
25 ◦C): d 2.14 (s, 3 H, Me), 6.87–6.95 (m, 3 H, H3–5), 7.42–7.50 (m,
24 H, ortho- + meta-CH, [PPN]), 7.67 (td, 6 H, para-CH, [PPN],
3JHH = 7 Hz, 4JHH = 2 Hz), 7.87 (d, 1 H, H6 Ar, 3JHH = 7 Hz), 10.88 (s,
Synthesis of [Pd{C,N-C6H3{C(Me) NOH}-2,NO2-5}(l-Cl)]2
(1¢). A suspension of PdCl2 (720 mg, 4.06 mmol) and LiCl (414
mg, 9.76 mmol) in MeOH (8 mL) was refluxed until it dissolved
and then it was allowed to cool at room temperature. To this solu-
tion was added another containing C6H4{C(Me) NOH}NO2-4
(658 mg, 3.76 mmol) and NaOAc (334 mg, 4.06 mmol) in MeOH
(10 mL). The reaction mixture was concentrated under vacuum
(5 mL), refluxed for 7 h, cooled at room temperature, filtered
through a short pad of Celite, and treated with a saturated aqueous
◦
1
1 H, OH). 13C{ H} NMR (100 MHz, CDCl3, 25 C): d 10.7 (Me8),
123.1 (CH4), 123.6 (CH3 or 5), 126.8 (X part of an AA’X system, N
= 109.2 Hz, ipso-C, [PPN]), 127.5 (CH3 or 5), 129.5–129.6 (m, meta-
CH, [PPN]), 131.9–132.0 (m, ortho-CH, [PPN]), 133.8 (para-CH,
[PPN]), 134.7 (CH6), 143.4 (C2), 152.0 (C1), 162.1 (C7). 31P{ H}
1
◦
NMR (81. MHz, CDCl3, 25 C): d 21.64. IR (cm-1): n(OH) not
758 | Dalton Trans., 2012, 41, 752–762
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observed. KM (X-1 cm2 mol-1): 105 (5.32 ¥ 10-4 M). Anal. Calcd for
C44H38Cl2N2OP2Pd: C, 62.17; H, 4.51; N, 3.30. Found: C, 61.96; H,
4.55; N, 3.34. Crystals of 3 suitable for an X-ray diffraction study
grew by the liquid diffusion method using CH2Cl2 and Et2O.
0.280 mmol) and KOtBu (32 mg, 0.29 mmol), with a 5 min interval.
The resulting suspension was stirred for 2 h, and filtered through a
short pad of Celite. The solution was concentrated under vacuum
to 1 mL and Et2O (20 mL) was added. The suspension was filtered
and the solid collected was washed with Et2O (3 ¥ 2 mL) and
dried, first by suction and then in a vacuum oven at 75 ◦C for 5 h
to give 6¢b as an orange solid.◦Yield: 103 mg, 95%. Mp: 202 ◦C. 1H
NMR (300 MHz, CDCl3, 25 C): d 2.13 (s, 3 H, Me8), 2.67 (br m,
2 H, CH2, tmeda), 2.78 (br m, 2 H, CH2, tmeda), 2.88 (s, 6 H, Me,
tmeda), 2.93 (s, 6 H, Me, tmeda), 6.98 (d, 1 H, H3, 3JHH = 8 Hz),
Synthesis
of
[Pd{C,N-C6H{C(Me) NOH}-2,(OMe)3-
4,5,6}}(acac)] (4¢). To a suspension of 1¢¢ (82 mg, 0.22 mmol) in
CH2Cl2 (10 mL) was added Tl(acac) (68 mg, 0.22 mmol). After
3 h of stirring CH2Cl2 (20 mL) was added and the suspension
was filtered through a short pad of Celite. The solution was
concentrated under vacuum to 1 mL. Upon the addition of Et2O
a suspension formed which was filtered and the solid collected
was washed with Et2O (2 ¥ 1 mL). The pale cream powder was
dried, first by suction, and then in an oven at 70◦◦C overnight
3
1
7.93 (d, 1 H, H4, JHH = 8 Hz), 7.94 (s, 1 H, H6). 13C{ H} NMR
◦
(75 MHz, CDCl3, 25 C): d 10.8 (Me8), 47.9 (Me, tmeda), 50.3
(Me, tmeda), 58.7 (CH2, tmeda), 63.3 (CH2, tmeda), 119.4 (CH3),
121.6 (CH4), 124.2 (CH6), 140.5 (C5), 154.9 (C7), 155.8 (C1), 157.1
(C2). Anal. Calcd for C14H22N4O3Pd: C, 41.96; H, 5.53; N, 13.98.
Found: C, 41.76; H, 5.80; N, 13.75. Crystals of 6¢b suitable for an
X-ray diffraction study were grown by the liquid diffusion method
using CH2Cl2 and n-pentane.
1
to give 4¢¢·0.1H2O: Yield: 65 mg, 68%. Mp: 152 C. H NMR
(400 MHz, CDCl3, 25 ◦C): d 1.58 (br s, 0.2 H, H2O), 2.03 (s, 3
H, Me, acac), 2.13 (s, 3 H, Me, acac), 2.25 (s, 3 H, Me8), 3.80 (s,
3 H, OMe), 3.85 (s, 3 H, OMe), 3.93 (s, 3 H, OMe), 5.44 (s, 1
1
H, CH, acac), 6.60 (s, 1 H, CH, Ar), 9.20 (s, 1 H, OH). 13C{ H}
Synthesis of [Pd{l-C,N,O-C6H4{C(Me) NO}-2}(CNtBu)]2
(7b). To a suspension of KOtBu (44 mg, 0.39 mmol) in CH2Cl2
(5 mL) was added 2b (141 mg, 0.39 mmol). After 90 min of stirring
the suspension was filtered through a short pad of Celite and
the solution was concentrated under vacuum to 1 mL. Upon the
addition of Et2O (10 mL) a suspension formed which was filtered
and the pale tan solid collected was washed with Et2O (2 ¥ 5 mL)
◦
NMR (50 MHz, CDCl3, 25 C): d 11.3 (Me8), 27.2 (Me, acac),
27.6 (Me, acac), 56.5 (OMe), 61.0 (OMe), 62.0 (OMe), 101.0
(CH, acac), 106.3 (CH3), 133 (C1), 138.3 (C2), 144.1 (C4 or 5 or 6),
151.0 (C4 or 5 or 6), 159.1 (C4 or 5 or 6), 165.3 (C7), 185.5 (CO), 188.9
(CO). IR (cm-1): n(OH) 3321. Anal. Calcd for C16H21.2NO6.1Pd:
C, 44.53; H, 4.95; N, 3.23. Found: C, 44.29; H, 5.34; N,
3.36.
◦
and dried by suction to give 7b. Yield: 92 mg, 73%. Mp: 161 C
Synthesis of [Pd{C,N-C6H4{C(Me) NOH}-2}(tBubpy)]OTf
(5a). To a suspension of 1 (100 mg, 0.18 mmol) in acetone
(dec). H NMR (400 MHz, CDCl3, 25 ◦C): d 1.61 (s, 9 H, Me,
1
3
4
tBu), 2.23 (s, 3 H, Me8), 6.77 (td, H5, JHH = 7 Hz, JHH = 1 Hz),
t
7.02 (td, H4, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.06 (dd, H3, 3JHH = 7 Hz,
(5 mL) were added Bubpy (98 mg, 0.37 mmol) and AgOTf (95
4JHH = 1 Hz), 7.13 (d, H6, 3JHH = 7 Hz). 13C{ H} NMR (75 MHz,
1
mg, 0.37 mmol). A suspension immediately formed which was
stirred in the dark for 25 min, and filtered through a short pad of
Celite. The solution was concentrated under vacuum to 2 mL, Et2O
(10 mL) was added and the suspension was filtered. The solid
collected was washed with Et2O (3 ¥ 2 mL) and dried by suction
to give 5a as a yellow powder: Yield: 95 mg, 82%. Mp: 216 ◦C
CDCl3, 25 ◦C): d 10.6 (Me8), 30.1 (Me, tBu), 57.6 (t, CMe3, 1JCN
= 5 Hz), 123.4 (CH3), 124.3 (CH4), 125.3 (CH5), 135.2 (t, C N,
1JCN = 18 Hz), 136.6 (CH6), 146.9 (C2), 154.5 (C1), 163.7 (C7). IR
(cm-1): n(C N) 2200. Anal. Calcd for C26H32N4O2Pd2: C, 48.39;
H, 5.00; N, 8.68. Found: C, 48.18; H, 5.13; N, 8.63. Crystals of
7b·H2O suitable for an X-ray diffraction study were obtained by
the liquid diffusion method using CH2Cl2 and Et2O.
◦
1
(dec). H NMR (400 MHz, CDCl3, 25 C): d 1.44 (s, 18 H, Me,
tBu), 2.44 (s, 3 H, Me8), 7.13 (t, 1 H, H4, Ar, JHH = 7 Hz), 7.18
3
(td, 1 H, H5, Ar, 3JHH = 7 Hz,4JHH = 2 Hz), 7.22 (dd, 1 H, H3, 3JHH
= 7 Hz,4JHH = 2 Hz), 7.24 (d, 1 H, H6, 3JHH = 7 Hz), 7.66 (d, 1 H,
Synthesis of [Pd{C,N-C( NXy)C6H{C(Me) NOH}-2-
(OMe)3-4,5,6}Cl(CNXy)] (8¢¢). To a solution of 2¢¢a (210 mg,
0.422 mmol) in CH2Cl2 (5 mL) was slowly added a solution
of XyNC (55.5 mg, 0.423 mmol) in CH2Cl2 (10 mL), and the
reaction mixture was stirred for 5 h. The reaction mixture was
concentrated under vacuum to dryness and the residue was
stirred with Et2O (25 mL). The suspension was filtered, the solid
collected was washed with Et2O (3 ¥ 1.5 mL), dried by suction,
recrystallized from CH2Cl2 and Et2O and dried in a vacuum oven
at 70 ◦C for 10 h to give 8¢¢·0.3H2O as a pale yellow solid: Yield:
H
12 or 12¢, tBubpy, 4JHH = 2 Hz), 7.67 (d, 1 H, H12 or 12¢, 4JHH = 2 Hz),
8.07 (s, 1 H, H10 or 10¢), 8.08 (s, 1 H, H10 or 10¢), 9.15 (br s, 2 H, H13 + 13¢),
10.60 (br s, 1 H, OH). (400 MHz, CDCl3, -60 ◦C): d 1.38 (s, 9
H, Me, Bu), 1.46 (s, 9 H, Me, Bu), 2.37 (s, 3 H, Me8), 7.19 (br
t
t
m, 2 H, CH, Ar), 7.27 (br m, 2 H, CH, Ar), 7.59 (d, 1 H, H12 or 12¢
,
3JHH = 5 Hz), 7.67 (d, 1 H, H12 or 12¢, JHH = 5 Hz), 7.88 (s, 1 H,
3
H
10 or 10¢), 7.99 (s, 1 H, H10 or 10¢), 9.16 (br m, 1 H, H13 or 13¢), 9.23 (d, 1
H, H13 or 13¢, 3JHH = 5 Hz), 10.44 (br s, 1 H, OH). 13C{ H} NMR (75
MHz, CDCl3, 25 ◦C): d 12.5 (Me8), 30.2 (Me, tBu), 35.6 (CMe3),
118.9 (br, CH10 + 10¢), 120.4 (q, TfO, 1JCF = 320 Hz), 124.2 (CH12 + 12¢),
125.4 (CH4), 126.4 (CH3 or 5), 129.8 (CH3 or 5), 131.9 (CH6), 142.4
(C2), 151.7 (br, CH13 + 13¢), 156.3 (C1), 164.8 (C11 + 11¢), 179.1 (C7), C9
1
◦
1
155 mg, 58%. Mp: 195 C (dec). H NMR (300 MHz, CDCl3,
◦
25 C): d 1.56 (s, 0.6 H, H O), 2.03 (s, 3 H, Me, Xyim), 2.16 (s,
2
6 H, Me, XyPd), 2.35 (s, 3 H, Me, Xyim), 2.50 (s, 3 H, Me8), 3.95
(s, 3 H, OMe), 3.98 (s, 3 H, OMe), 3.99 (s, 3 H, OMe), 6.61 (d,
◦
and C9¢ not observed. 19F{ H} NMR: (282 MHz, CDCl3, 25 C):
d -78.6 (OTf). IR (cm-1): n(OH) not observed. KM (X-1 cm2 mol-1):
121 (5.04 ¥ 10-4 M). Anal. Calcd for C27H32F3N3O4PdS: C, 49.28;
H, 4.90; N, 6.39; S, 4.87. Found: C, 48.93; H, 5.18; N, 6.33; S, 4.46.
1
1 H, meta-CH, Xyim, JHH = 7 Hz), 6.82 (s, H3), 6.88 (t, 1 H,
3
para-CH, Xyim, JHH = 8 Hz), 7.06 (d, 2 H, meta-CH, XyPd, JHH
3
3
= 8 Hz), 7.16 (d, meta-CH, Xyim, 3JHH = 8 Hz), 7.22 (t, para-CH,
Xyim, 3JHH = 8 Hz), 10.66 (s, 1 H, OH). 13C{ H} NMR (100 MHz,
1
◦
Synthesis of [Pd{C,N-C6H3{C(Me) NO}-2,NO2-5}(tmeda)]
(6¢b). To a suspension of 1¢ (87 mg, 0.14 mmol) in CH2Cl2
(15 mL) were successively added, under nitrogen, tmeda (42 mL,
CDCl3, 25 C): d 14.8 (Me8), 18.2 (Me, Xyim), 18.5 (Me, XyPd),
18.7 (Me, Xyim), 56.4 (OMe), 61.0 (OMe), 61.6 (OMe), 107.2
(CH3), 122.7 (C1), 123.5 (para-CH, Xyim), 125.7 (br, ipso-C, XyPd),
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©

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Table 1 Crystal data and structure refinement of complexes 2d, 3, 3’, and 6’b
Complex
2d
3
3’
6’b
Formula
Fw
T/K
C14H15ClN2OPd
369.13
100(2)
C44H38Cl2N2OP2 Pd
850.00
100(2)
C44H37Cl2N3O3P2Pd
895.01
100(2)
C14H22N4O3Pd
400.76
100(2)
Crystal system
Space group
Triclinic
P -1
Monoclinic
P 2(1)
10.4042(4)
13.5259(6)
13.7681(6)
90
101.603(2)
90
1897.94(14)
2
1.487
0.752
868
0.23 ¥ 0.07 ¥ 0.04
2.00 to 28.27
22172
Monoclinic
P 2(1)
10.5577(7)
13.2121(9)
14.6686(11)
90
105.436(2)
90
1972.3(2)
2
1.507
0.732
912
0.24 ¥ 0.17 ¥ 0.05
2.00 to 28.65
31495
Monoclinic
P 2(1)/n
8.4822(8)
11.5612(11)
15.6484(15)
90
90.517(2)
90
1534.5(3)
4
1.735
1.228
816
0.20 ¥ 0.12 ¥ 0.07
2.19 to 28.72
18671
˚
a/A
9.1285(4)
9.2016(4)
10.0426(4)
90.108(2)
108.795(2)
114.271(2)
719.11(6)
2
1.705
1.468
368
0.21 ¥ 0.20 ¥ 0.20
2.46 to 28.03
8249
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
Volume/A
Z
rc/Mg m-3
m/mm-1
F(000)
Crystal size/mm
q range (◦)
No. rflns coll.
No. indep. rflns/Rint
3211/0.0133
0.7577/0.7001
0/179
1.076
0.0172
0.0448
0.398/-0.637
8427/0.0319
0.9705/0.8522
1/474
1.041
0.0318
0.0681
0.715/-0.315
9375/0.0280
0.9643/0.7603
2/501
1.103
0.0305
0.0690
0.765/-0.670
3762/0.0234
0.9190/0.8100
0/204
1.110
0.0232
0.0526
0.513/-0.0463
Transmission
Restraints/params
Goodness–of–fit on F2
R1 (I > 2s(I))
wR2 (all reflns)
-3
˚
Largest diff. peak/hole/e A
126.6 (ortho-C, Xyim), 126.7 (ortho-C, Xyim), 127.1 (meta-CH,
Xyim), 127.8 (meta-CH, XyPd), 128.2 (C2), 128.8 (meta-CH, Xyim),
129.7 (para-CH, XyPd), 135.3 (ortho-C, XyPd), 141.3 (C◦N), 145.4
(C4 or 5 or 6), 148.6 (C4 or 5 or 6), 150.7 (ipso-C, Xyim), 153.2 (C4 or 5 or 6),
156.1 (C7), 172.4 (C NXy). IR (cm-1): n(OH) not observed;
2191 n(C N). Anal. Calcd for C29H32.6ClN3O4.3Pd: C, 54.95; H,
5.18; N, 6.63. Found: C, 54.85; H, 5.08; N, 6.63. Crystals of 8¢¢
suitable for an X-ray diffraction study were obtained by the liquid
diffusion method using CHCl3 and Et2O.
CH, Xy), 128.5 (CH3), 128.9 (meta-CH, Xy), 129.3 (CH4), 129.5
(ortho-C, Xy), 130.0 (CH5), 130.8 (ortho-C, Xy), 132.2 (C2), 133.0
(C1), 146.6 (ipso-C, Xy), 156.9 (C7), 207.0 (C NXy). IR (cm-1):
n(OH) not observed. Anal. Calcd for C17H17ClN2OPd: C, 50.15;
H, 4.21; N, 6.88. Found: C, 49.78; H, 4.24; N, 6.89. Crystals of
9·2CHCl3 suitable for an X-ray diffraction study were obtained by
slow diffusion of Et2O into a solution of the complex in CHCl3.
X-Ray structure determinations of complexes 2d, 3, 3¢, 6¢b,
7b·H2O, 8¢¢ and 9·2CHCl3. For clarity, solvent contents are
omitted here, but are defined in Tables 1 and 2. Fig. 1–7 show the
ellipsoid representation. All complexes were measured on a Bruker
Smart APEX machine. Data were collected using monochromated
Mo-Ka radiation. The structures were solved by direct methods.
All were refined anisotropically on F2. Restraints to local aromatic
ring symmetry or light atom displacement factor components were
applied in some cases. The OH were refined freely and also with
DFIX in complex 3¢, 7b·H2O and 9·2CHCl3, the ordered methyl
groups were refined using rigid groups, and the others were refined
using a riding model.
Synthesis of [Pd{l-C,N,N’-C( NXy)C6H4{C(Me) NOH}-
2}(Cl)]2 (9). To a solution of 8 (107 mg, 0.20 mmol) in CHCl3
(4 mL), was added [AuCl(SMe2)] (58.5 mg, 0.20 mmol). After 1.5
h of stirring, the slightly darkened solution was filtered through
a short pad of anhydrous MgSO4. The yellow solution was
concentrated to dryness, the residue was stirred with a Et2O/n-
hexane mixture (1 : 1, 20 mL), and the resulting suspension was
filtered. The solid collected was treated in CH2Cl2 (5 mL) with
[AuCl(SMe2)] (58.5 mg, 0.20 mmol) for 30 min and the reaction
mixture was filtered through a short pad of anhydrous MgSO4 and
concentrated under vacuum to 1 mL. Upon the addition of Et2O
(10 mL) and n-hexane (2 mL) a suspension formed which was
filtered. The solution was concentrated to dryness and the residue
was stirred with n-hexane. The suspension was filtered and the
solid collected was dried by suction to give pale yellow 9. Yield:
Special features and exceptions
For complex 3: the Flack parameter22 is -0.026(15); 3¢: the Flack
parameter is 0.000(14); 8¢¢: one methyl is disordered over two
positions, ca. 57 : 43% ; 9·2CHCl3: the structure contains two
solvent residues: one dichloromethane is disordered over two
positions, ca. (83 : 17%) and an ill-defined region of residual
electron density was identified also as disordered dichloromethane,
but the refinement was far from satisfactory. Only the hydrogen
of the main part of one dichloromethane was included in the
refinement.
◦
1
30 mg, 37%. Mp: 246 C (dec). H NMR (400 MHz, CDCl3, 25
◦C): d 1.73 (s, 3 H, MeXy), 2.52 (s, 6 H, Me8 + MeXy), 6.56 (dd,
H6, JHH = 8 Hz, JHH = 1 Hz), 6.68 (m, 1 H, meta-CH, Xy),
3
4
6.84–6.88 (m, 2 H, meta- + para-CH, Xy), 7.07 (td, H5, JHH = 8
3
Hz, JHH = 1 Hz), 7.31 (td, H4, JHH = 8 Hz, JHH = 1 Hz), 7.52
4
3
4
3
4
1
(dd, H3, JHH = 8 Hz, JHH = 1 Hz), 11.30 (s, 1 H, OH). 13C{ H}
◦
NMR (75 MHz, CDCl3, 25 C): d 14.8 (Me8), 19.2 (Me, Xy),
20.4 (Me, Xy), 123.1 (CH6), 126.4 (para-CH, Xy), 127.9 (meta-
760 | Dalton Trans., 2012, 41, 752–762
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Table 2 Crystal data and structure refinement of complexes 7b·H2O, 8¢¢ and 9·2CHCl3
Complex
7b·H2O
8¢¢
9·2CHCl3
Formula
Fw
T/K
C26H34N4O3Pd2
663.37
100(2)
C29H32ClN3O4Pd
628.43
100(2)
C36H36Cl8N4O2Pd2
1053.09
100(2)
Crystal system
Space group
Monoclinic
C 2/c
27.9117(12)
11.4690(5)
18.9722(8)
90
116.729(2)
90
5424.4(4)
8
1.625
1.359
2672
0.31 ¥ 0.22 ¥ 0.12
1.95 to 28.16
30421
Monoclinic
P 2(1)/n
13.1876(11)
8.0675(14)
12.4618(9)
90
105.989(2)
90
2854.4(4)
4
1.462
0.782
1288
0.25 ¥ 0.12 ¥ 0.09
1.61 to 28.66
18582
Monoclinic
P 2(1)/n
16.9138(6)
11.0175(4)
22.5029(9)
90
90.541(2)
90
4193.2(3)
4
1.668
1.405
2096
0.19 ¥ 0.11 ¥ 0.05
1.81 to 28.26
47665
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
Volume/A
Z
rc/Mg m-3
m/mm-1
F(000)
Crystal size/mm
q range (◦)
No. rflns coll.
No. indep. rflns/Rint
6181/0.0182
0.8539/0.7527
3/332
1.039
0.0198
0.051
0.729/-0.449
6757/0.0241
0.9330/0.8188
1/354
1.099
0.0356
0.0886
1.171/-0.337
9799/0.0475
0.9331/0.8385
144/527
1.109
0.0466
0.0935
Transmission
Restraints/parameters
Goodness–of–fit on F2
R1 (I > 2s(I))
wR2 (all reflns)
-3
˚
Largest diff. peak/hole/e A
0.831/-0.772
8 G. D. Fallon and B. M. Gatehouse, Acta Crystallogr., Sect. B: Struct.
Crystallogr. Cryst. Chem., 1976, 32, 2591.
Conclusion
9 M. Kim and F. P. Gabbai, Dalton Trans., 2004, 3403.
10 S. B. Atla, A. A. Kelkar, V. G. Puranik, W. Bensch and R. V. Chaudhari,
J. Organomet. Chem., 2009, 694, 683.
11 H. Onoue, K. Minami and K. Nakagawa, Bull. Chem. Soc. Jpn., 1970,
43, 3480.
The work reports the synthesis, reactivity and structure of the first
family of well-characterized cyclopalladated complexes derived
from oximes. This group of complexes includes cyclopalladated
acetophenone oxime and two of its derivatives containing sub-
stituents on the aryl group with different electronic properties
(NO2-5 and (MeO)3-4,5,6), which are unprecedented. Deprotona-
tion reactions of the oxime and isocyanide insertion, have allowed
us to prepare the first aryloximato and iminoaryloxime complexes
of any metal. [AuCl(SMe2)] has been successfully used for the first
time as an isocyanide ligand scavenger.
12 Y. Yamamoto and J. Uzama, Chem. Lett., 1978, 1213.
13 See for example, J. Vicente, J. A. Abad, B. Lopez-Pelaez and E.
Martinez-Viviente, Organometallics, 2002, 21, 58; J. Vicente, J. A. Abad,
R. Bergs, P. G. Jones and M. C. Ramirez de Arellano, Organometallics,
1996, 15, 1422; J. Vicente, I. Saura-Llamas and M. C. Ramirez
de Arellano, J. Chem. Soc., Dalton Trans., 1995, 2529; J. Vicente,
J. A. Abad, J. Gil-Rubio and P. G. Jones, Organometallics, 1995,
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Acknowledgements
We thank Ministerio de Educacio´n
y Ciencia (Spain),
FEDER (CTQ2007-60808/BQU) and Fundacio´n Se´neca
(04539/GERM/06 and 03059/PI/05) for financial support and
for a grant to A.A.L.
14 J. Vicente, J. A. Abad, A. D. Frankland and M. C. Ram´ırez de Arellano,
Chem.–Eur. J., 1999, 5, 3066; J. Vicente, J. A. Abad, J. Lopez-Serrano,
R. Clemente, M. C. Ramirez de Arellano, P. G. Jones and D. Bautista,
Organometallics, 2003, 22, 4248; J. Vicente, A. Arcas, D. Bautista and
P. G. Jones, Organometallics, 1997, 16, 2127.
15 Y. Yamamoto and J. Uzawa, Chem. Lett., 1978, 1213.
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17 G. M. Kazankov, V. S. Sergeeva, E. N. Efremenko, L. Alexandrova, S.
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18 Y. Yamamoto and H. Yamazaki, Inorg. Chim. Acta, 1980, 41, 229;
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19 J. G. P. Delis, P. G. Aubel, K. Vrieze, W. N. M. van Leeuwen, N.
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762 | Dalton Trans., 2012, 41, 752–762
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The Royal Society of Chemistry 2012
©