Cyclopalladated complexes derived from phenylacetone oxime. Insertion reactions of carbon monoxide, isocyanides, and alkynes. Novel amidines of the isoquinoline series

Article abstract of DOI:10.1021/om4010912

Neutral and cationic six-membered C,N-palladacycles with the core "Pd{C,N-C₆H₄{CH₂C(Me)=NOH}-2}" have been obtained by oxidative addition of the oxime BrC₆H ₄{CH₂C(Me)=NOH}-2 to "Pd(dba)₂" (dba = dibenzylideneacetone) in the presence of mono- or bidentate ligands. The oximato complex [Pd{μ-C,N,O-C₆H₄{CH₂C(Me)= NO}-2}(PTol₃)]₂ forms after dehydrobromination of the appropriate oxime complex with K^tBuO, while the pincer derivative [Pd{C,N,N′-C₆H₄{CH₂C(Me)=NOCH ₂py}-2}Br] results by attack of an in situ generated oximato complex to BrCH₂py·HBr. Insertion of CO or RNC in some of the palladacycles causes a depalladation/coupling process, giving 1,2-dihydro-1-oxo-2-hydroxy-3-methylisoquinoline or 1,2-dihydro-1-imino(R)-2- hydroxy-3-methylisoquinoline, respectively, while the insertion of alkynes produces eight-membered alkenyl(oxime) palladacycles "Pd{C,N-C(R′)= C(R)C₆H₄{CH₂C(Me)=NOH}-2}". When using diphenylacetylene, a dimeric tetranuclear complex [{Pd(tbbpy)} ₂{μ-N,O-{η³-C₆H₄(C ₄Ph₄){CH₂C(Me)=NO}}}]₂⁴⁺ forms instead, in which a π-allyl-coordinated oximato, bearing a spirocyclic substituent, acts as the bridging ligand. The crystal structures of the oxime and of each type of complexes have been determined.

Full text of DOI:10.1021/om4010912

Article
pubs.acs.org/Organometallics
Cyclopalladated Complexes Derived from Phenylacetone Oxime.
Insertion Reactions of Carbon Monoxide, Isocyanides, and Alkynes.
Novel Amidines of the Isoquinoline Series
Antonio Abellan-Lopez,† María-Teresa Chicote,† Delia Bautista,‡ and Jose Vicente*,†
́
́
́
†Grupo de Química Organometal
Spain
́
ica, Departamento de Química Inorgan
́
ica, Universidad de Murcia, Apartado 4021, 30071 Murcia,
‡SAI, Universidad de Murcia, Apartado 4021, 30071 Murcia, Spain
S
* Supporting Information
ABSTRACT: Neutral and cationic six-membered C,N-palladacycles with
the core “Pd{C,N-C6H4{CH2C(Me)NOH}-2}” have been obtained by
oxidative addition of the oxime BrC6H4{CH2C(Me)NOH}-2 to
“Pd(dba)2” (dba = dibenzylideneacetone) in the presence of mono- or
bidentate ligands. The oximato complex [Pd{μ-C,N,O-C6H4{CH2C-
(Me)NO}-2}(PTol3)]2 forms after dehydrobromination of the
appropriate oxime complex with KtBuO, while the pincer derivative
[Pd{C,N,N′-C6H4{CH2C(Me)NOCH2py}-2}Br] results by attack of
an in situ generated oximato complex to BrCH2py·HBr. Insertion of CO
or RNC in some of the palladacycles causes a depalladation/coupling
process, giving 1,2-dihydro-1-oxo-2-hydroxy-3-methylisoquinoline or 1,2-
dihydro-1-imino(R)-2-hydroxy-3-methylisoquinoline, respectively, while the insertion of alkynes produces eight-membered
alkenyl(oxime) palladacycles “Pd{C,N-C(R′)C(R)C6H4{CH2C(Me)NOH}-2}”. When using diphenylacetylene, a dimeric
4+
tetranuclear complex [{Pd(tbbpy)}2{μ-N,O-{η3-C6H4(C4Ph4){CH2C(Me)NO}}}]2 forms instead, in which a π-allyl-
coordinated oximato, bearing a spirocyclic substituent, acts as the bridging ligand. The crystal structures of the oxime and of each
type of complexes have been determined.
unsaturated reagents, mainly, CO, RNC,2,16,17 and alkynes2,15,18
INTRODUCTION
■
but also with carbodiimides,19 isothiocyanates,20 olefins,16,21
nitriles,22 or allenes.23,24 In some cases we have also studied
sequential insertions of two or three of these reagents.25−27
From these studies we have isolated interesting palladium
complexes and organic compounds.2,15,17,20,21,24,26,28−30 We
have synthesized the first family of palladacycles derived from
methyl aryl ketone oximes,31,32 of which only a few derivatives
were known.33 We carried out the first study of the reactivity of
this type of complexes, which was surprisingly unexplored in
view of their versatile and efficient use as precatalysts in C−C
coupling processes.34
The interest of aryl-palladium complexes in themselves or in
organic synthesis is of general knowledge. In particular, the
group of ortho-functionalized aryl complexes have the addi-
tional attraction of affording, in some cases, cyclopalladated
complexes1,2 displaying numerous and interesting applications
in catalytic3 and stoichiometric synthesis of organic com-
pounds.4
Catalytic C−C or C−heteroatom coupling reactions usually
take place after reacting aryl palladium complexes with
nucleophiles. Sometimes, the coupling reaction’s product
forms, along with Pd(0), after coordination of the nucleophile
to Pd;5,6 other times, before decomposition, the nucleophile
inserts into the Pd−Caryl bond.7 Insertion of CO or isocyanides
into the Pd−Caryl bond of aryl palladium complexes is known to
produce the corresponding benzoyl8 or iminobenzoyl9,10
complexes. Transition-metal-catalyzed carbonylations have
been used to prepare carboxylic acids, esters, amides,
heterocycles, etc.11 Similarly, palladium-catalyzed reactions
involving isocyanides afford nitrogen-containing organic
compounds,12 and insertions of alkynes into the aryl−Pd
bond have found applications in the synthesis of cyclic
species.13
In this paper we describe the synthesis of cyclopalladated
derivatives of phenylacetone oxime, which are the first six-
membered cyclometalated complexes of any metal derived from
an oxime (Chart 1). Their reactivity toward CO or isocyanides
has allowed the synthesis of 1-oxo- and 1-imino-substituted 1,2-
dihydro-2-hydroxyisoquinoline derivatives. Many compounds
containing the isoquinoline core have been shown to display
biological and pharmacological activity,35 and, in particular,
some 2-hydroxyisoquinolones are antidepressant and tranquil-
izer agents.36 As far as we are aware, 1-(alkyl- or aryl-imino)-
Our main research line is the study of ortho-substituted aryl
Received: November 11, 2013
Published: December 6, 2013
palladium complexes as catalysts2,14,15 or their reactivity toward
© 2013 American Chemical Society
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Chart 1
Scheme 1
1,2-dihydro-2-hydroxyisoquinolines, i.e., amidine compounds
derived from isoquinoline, are unknown.
In addition, a C,N,N′-pincer complex forms by reaction with
2-bromomethylpyridine, and alkynes insert into the Pd−C
bond, leading to stable eight-membered alkenyl(oxime)
palladacycles. When diphenylacetylene is used, a dimeric
tetranuclear complex bearing an oximato ligand with a
spirocyclic substituent is isolated. The various types of
compounds prepared are depicted in Chart 1.
4-[Pd{C,N-C6H4{CH2C(Me)NOH}-2}Br(pic)] (3a) was
obtained instead (63% yield), showing that the coordination
of bromide is preferred to that of pic. The yield did not
improve but decreased when the stoichiometric amount of pic
was used. Complex 2·ClO4 could also be prepared by reacting
3a with tbbpy (1:1) and excess NaClO4·H2O in acetone. We
attribute the moderate yields achieved in the isolation of
complexes 2·Br and 3a to the fact that oxidative addition
reactions to Pd(0) species are commonly accompanied by more
or less abundant decomposition to Pd(0).28 Additionally,
recrystallization was required to remove small amounts of
[PdBr2(pic)2] and [PdBr2(tbbpy)], respectively. Complex SP-4-
4-[Pd{C,N-C6H4{CH2C(Me)NOH}-2}Br(PTol3)] (Tol =
C6H4Me-4, 3b) was obtained by replacing the pic ligand in
3a with PTol3.
RESULTS AND DISCUSSION
■
Synthesis. The oxime BrC6H4{CH2C(Me)NOH}-2 (1)
was recently reported and used in the first step of the synthesis
of benzoimidazolylmethylpyrimidineamine derivatives, ana-
logues of serine/threonine PAK1 inhibitors.37 It was charac-
terized only by its ESI-MS. The method we report here
(Scheme 1) allows a much shorter reaction time and a nearly
quantitative yield. We decided to use this bromo-substituted
oxime to prepare orthopalladated phenylacetone oxime
complexes by oxidative addition to [Pd2(dba)3]·dba (“Pd-
(dba)2”, dba = dibenzylideneacetone) only after various failed
attempts to orthometalate the unsubstituted oxime
C6H5{CH2C(Me)NOH}-2 by reacting it with Li2[PdCl4]
in MeOH or with Pd(OAc)2 in MeCN in the presence or not
of triflic acid.
The reaction of “Pd(dba)2” with 1 (1:1, in toluene at 65 °C,
4 h under nitrogen) gave, instead of the expected complex
[Pd{C,N-C6H4{CH2C(Me)NOH}-2}(μ-Br)]2, a mixture
that we could not separate. However, when the same reaction
was carried out in the presence of 1 equiv of 4,4′-di-tert-butyl-
2,2′-bipyridine (tbbpy), [Pd{C,N-C6H4{CH2C(Me)NOH}-
2}(tbbpy)]Br (2·Br) could be obtained in 53% yield (Scheme
1).
The reaction of complex 2·ClO4 or 2·Br with KtBuO, which
we did under various reaction conditions with the purpose of
preparing the zwitterionic oximato complex [Pd{C,N-
C6H4{CH2C(Me)NO}-2}(tbbpy)], homologous to those
derived from the oximes of acetophenone and p-nitro-
acetophenone,32 gave a complex mixture from which we
could not isolate any pure species. In spite of the fact that
dinuclear bridging oximato complexes [Pd{μ-C,N,O-C6H4{C-
t
(R)NO}-2}(L)]2 (R = Me, L = XyNC, BuNC, PTol3; R =
Quantitative replacement of bromide by perchlorate in 2·Br
to give [Pd{C,N-C6H4{CH2C(Me)NOH}-2}(tbbpy)]ClO4
(2·ClO4) was achieved by reacting it with excess NaClO4·
H2O in acetone. The reaction of “Pd(dba)2” with 1 and 4-
methylpyridine (pic) (1:1:2, in THF, at 45 °C) did not give a
cationic complex analogous to 2·Br; the neutral complex SP-4-
NH2, L = PTol3), derived from the above-mentioned oximes or
benzamidoxime,38 were isolated in good yield, the reaction of
3a with KtBuO produced a mixture, probably because of the
ability of the oximato ligand to displace both the bromo and the
picoline ligand. In fact, 3b reacted with KtBuO to give the pure
oximato complex [Pd{μ-C,N,O-C6H4{CH2C(Me)NO}-2}-
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(PTol3)]2 (4). After removing the insoluble KBr by filtration
and concentrating the resulting solution, 4 precipitated in 57%
yield upon the addition of pentane. A second crop of 4 was
obtained by concentrating the mother liquor to dryness,
making a total yield of 79%.
2-hydroxy-3-methylisoquinoline, are the first such compounds
bearing an OH group on the endocyclic nitrogen. The
preparation of compounds 6−8 shows, for the first time, the
direct participation of cyclopalladated oximes in organic
synthesis, although they have been used as a source of
palladium nanoparticles that act as catalysts in many coupling
reactions.5
We have also studied the reaction of 2·ClO4 or 3a with
alkynes. With dimethyl acetylenedicarboxylate we obtained the
alkenyl complexes [Pd{C,N-C(CO2Me)C(CO2Me)-
C6H4{CH2C(Me)NOH}-2}(tbbpy)]ClO4 (9a) and SP-4−
4-[Pd{C,N-C(CO2Me)C(CO2Me)C6H4{CH2C(Me)
NOH}-2}Br(pic)] (10a) (Scheme 2), respectively. The
We have previously shown that pincer complexes containing
the C,N,N′-oxime ether ligand C,N,N′-C6H4{C(Me)
NOCH2(C5H4N-2)}-2 can be prepared by reacting the
appropriate oxime palladacyclic complex with KtBuO and
XCH2py-2 (X = Cl, Br),31 which, in turn, forms by
dehydrohalogenation of the commercial reagent XCH2py·HX
with KtBuO. The pincer ligand forms by attack of the generated
oximato function on the reagent’s methylene group. Similarly,
the reaction of 3a with BrCH2py·HBr and KtBuO (1:1:2, in
CH2Cl2, 2 h) allowed the synthesis of [Pd{C,N,N′-
C6H4{CH2C(Me)NOCH2(C5H4N-2)}-2}Br] (5, Scheme
1), which was isolated in 55% yield upon precipitation with
Et2O. 5 could also be obtained using 2·ClO4 instead of 3a, but
in this case the yield was somewhat lower.
Scheme 2
Complex 3a was reacted with CO with the purpose of
preparing the corresponding benzoyl derivative, but it must be
unstable and, after spontaneous depalladation, an isocarbostyril
compound, namely, 1,2-dihydro-2-hydroxy-3-methylisoquino-
lone (6), formed in 84% yield along with the equimolar amount
of pic·HBr (Scheme 1). Similarly, the reaction of 2·Br with CO,
under the same reaction conditions, gave 6 and [tbbpyH]Br,
although in this case the yield was lower. The reactions with
CO were carried out in a Carius tube, using a CHCl3 solution
of the palladium complex and a 1.4 bar pressure of CO, and the
insoluble ammonium salts were removed upon extraction of the
reaction mixture with Et2O. The synthesis of 6 by treating 2-
methyl-1-indanone with n-butyl nitrite and HCl (1:1:1, 4 days
in toluene, 68% yield) or by ozonization of 3-methylisoquino-
line-2-oxide (CH2Cl2, 0 °C, 15% yield) was previously
reported.39 Some 2-hydroxy-3-alkylisocarbostyrils have gained
relevance because of their antidepressant and tranquilizing
activity.36
reactions with 2·ClO4 required a large excess of alkyne, while
with 3a they were complete in a shorter time using 1 equiv of
alkyne, which may be attributed to the higher negative charge
on the aryl carbon attached to Pd in the neutral complex 3a,
although the bulkier tbbpy ligand in 2·ClO4 could also impose
more difficulty in the coordination of the alkyne to Pd, previous
to the migratory insertion. The reaction of 10a with an
equimolar amount of PTol3 (in CH2Cl2, 4 h) causes the
replacement of the pic ligand by PTol3 to give SP-4-4-[Pd{C,N-
C(CO2Me)C(CO2Me)C6H4{CH2C(Me)NOH}-2}Br-
(PTol3)] (10c), which was isolated in 72% yield. Dehydro-
bromination of 10c with KtBuO (1:1, 4 h in CH2Cl2) was
attempted with the aim to prepare the corresponding oximato
complex [Pd{{μ-C,N,O-C(CO2Me)C(CO2Me)C6H4-
{CH2C(Me)NO}-2}(PTol3)]2, but a complex mixture
formed instead, from which we could not separate or identify
any species. 10b was isolated in 80% yield from 3a and methyl
phenylpropiolate, but we could not obtain pure [Pd{C,N-
C(CO2Me)C(Ph)C6H4{CH2C(Me)NOH}-2}(tbbpy)]-
ClO4 (9b) from the same alkyne and 2·ClO4. When the
reaction time was prolonged and/or a large excess of alkyne
was used, mixtures of 9b with some polyinsertion species were
isolated. We have tentatively assigned the resonances
attributable to 9b from a recrystallized mixture.42
We could not isolate any adduct or iminobenzoyl complexes
by reacting our aryloxime complexes with isocyanides, at
difference with what we observed with other oxime Pd(II)
complexes.32,38 However, when 2·ClO4 was reacted with 2
t
equiv of RNC (R = Bu, Xy, room temperature), compounds
1,2-dihydro-1-imino(R)-2-hydroxy-3-methyl-isoquinoline (R =
tBu (7a), Xy (7b), Scheme 1) were isolated, probably by
decomposition of the expected iminobenzoyl complexes. Using
1 equiv of isocyanide caused in both cases a significant yield
decrease. Compounds 7 were also obtained when 3a was used
instead of 2·ClO4, but some additional impurities made the
purification process difficult. Although the insertion process is
known to be facilitated when the aryl carbon bonded to Pd and
the isocyanide carbon bear higher negative and positive charge,
respectively,10,20 we have not found significant differences
within all these reactions in spite of the starting complex being
cationic or neutral and the Xy and tBu groups in the isocyanide
having opposite electronic effect. After various failed attempts
to grow single crystals of compounds 7, we reacted 7b with
picric acid (1:1, CH2Cl2, 30 min at room temperature). The
picrate salt 8 was isolated by precipitation with Et2O, but the
crystals we were able to grow were too small for an X-ray
diffraction study. Although cyclic amidine derivatives related to
isoquinoline are known,20,40,41 some of them displaying anti-
inflammatory, analgesic, or antihypertensive properties, the
amidines 7 and the amidinium salt 8, derived from 1,2-dihydro-
The reaction of 2·ClO4 with 1 or 2 equiv of diphenylace-
tylene at room temperature was shown by 1H NMR to occur at
a low extent. When we forced the reaction conditions (1:3,
CHCl3, 48 h, 60 °C), the insoluble product [{Pd(tbbpy)}2{μ-
N,O-{η3-C6H4(C4Ph4){CH2C(Me)NO}}}]2(ClO4)4 (11·
ClO4, Scheme 2) formed, containing an η3-allyl-bridging
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oximato ligand with a spirocyclic moiety, which we isolated in
42% yield and identified by its elemental analyses, HRMS (ESI
+ and ESI−), and NMR spectra. The reaction is rather
complex, as proved by the presence of several unidentified
reasonably should be greater. We attribute the low value for 11
to the reduced mobility of the cation, because of its extremely
big size, and to some type of ions’ association.
The behavior of our six-membered aryloxime palladacycles
toward alkynes, described above, differs from that of the five-
membered analogues derived from acetophenone oxime or
3,4,5-trimethoxy acetophenone oxime, which did not react with
dimethylacetylene dicarboxylate or led to complex mixtures
when the reaction conditions were forced.
1
species in the H NMR spectrum of the mother liquor from
which 11·ClO4 precipitated. The complex is also scarcely
soluble in CH2Cl2 and acetone, and, although it decomposes on
standing in DMSO or CD3CN, we could measure its NMR
spectra in CD3CN after a short acquisition time. After various
failed attempts to grow single crystals of 11·ClO4 in order to
ascertain the proposed structure, we tried to synthesize 11·TfO
from [Pd{C,N-C6H4{CH2C(Me)NOH}-2}(tbbpy)]TfO
(prepared, in turn, from 2·Br, AgOTf, and tbbpy) and
diphenylacetylene, but a complex mixture was obtained that
we could not separate. We also attempted the reaction of 2·
ClO4 with 4-BrC6H4CCC6H4Br-4, which allowed the
synthesis of the complex analogous to 11·ClO4 (by NMR) in
11% yield, but it was still less soluble. The reaction of 2·ClO4
with potassium picrate (5-fold excess, acetone, 4 h at room
temperature) did not produce complete replacement of
perchlorate by picrate (elemental analyses and IR spectrum),
and longer reaction times led to decomposition. The reaction
produced a mixture that analyzes as 11·ClO4 + 3 11·picrate,
from which we could grow single crystals of 11·picrate suitable,
in spite of many disorder problems, for its crystal structure to
be measured. In addition, repeated recrystallization of the
above-mentioned mixture from CHCl3 and Et2O allowed the
isolation of a small crop of pure 11·picrate, which we used for
analytical and spectroscopic measurements.
Attempts to insert XyNC or CO into the Pd−C bond of the
alkenyl complex 9a were unfruitful. In both cases mixtures were
obtained that we could not separate, likely containing various
polyinsertion products in view of the many CO2Me resonances
1
in their H NMR spectra.
X-ray Crystal Structures. The crystal structures of the
oxime 1 (Figure 1) and of complexes 2·Br (Figure 2), 3a
Figure 1. Left: Thermal ellipsoid representation plot (50%
probability) of compound 1. Selected bond lengths (Å) and angles
(deg): N(1)−C(8) 1.276(3), N(1)−O(1) 1.415(2); C(8)−N(1)−
O(1) 112.37(15), N(1)−C(8)−C(9) 125.16(18), N(1)−C(8)−C(7)
117.21(17), C(9)−C(8)−C(7) 117.61(18). Right: Dimer formed in 1
through O−H···N hydrogen bonds.
Palladium complexes containing π-allyl spirocyclic ligands of
the type found in complex 11·ClO4 are known to form from
the insertion of two molecules of alkyne into the Pd−C bond,
followed by cyclization of the resulting butadienyl moi-
ety.18,25,43,44 We assume that complex 11·ClO4 forms through
a sequential di-insertion/cyclization reaction (giving intermedi-
ates A and B, Scheme 3) followed by the acid/base reaction B +
2·ClO4 → C6H5CH2C(Me)NOH + 1/2 11·ClO4.
(Figure 3), 5 (Figure 4), 9a (Figure 5), 10a (Figure 6), and 11·
picrate (Figure 7) have been determined by X-ray diffraction
studies. Details on crystal data, data collection, and refinements
are summarized in the Supporting Information.
The molar conductivities of complexes 11 (11·picrate, 210
Ω−1·cm2·mol−1; 11·ClO4, 283 Ω−1·cm2·mol−1; approximately 5
× 10−4 mol·L−1) in acetone solutions are well below that found
for a 3:1 electrolyte (446 Ω−1·cm2·mol−1).45 We are not aware
of data of molar conductivities of 1:4 electrolytes in acetone but
Scheme 3
Figure 2. Left: Thermal ellipsoid representation plot (50%
probability) of the cation of complex 2·Br. Most hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and angles (deg):
Pd(1)−C(1) 1.994(2), Pd(1)−N(1) 2.013(2), Pd(1)−N(2)
2.0462(19), Pd(1)−N(3) 2.1144(19), N(1)−C(8) 1.280(3), N(1)−
O(1) 1.399(3); C(1)−Pd(1)−N(1) 84.66(8), C(1)−Pd(1)−N(2)
97.83(8), N(1)−Pd(1)−N(2) 177.41(8), C(1)−Pd(1)−N(3)
175.46(8), N(1)−Pd(1)−N(3) 98.98(7), N(2)−Pd(1)−N(3)
78.50(7), C(8)−N(1)−O(1) 114.59(19), C(8)−N(1)−Pd(1)
126.00(16), O(1)−N(1)−Pd(1) 119.04(14), C(8)−C(7)−C(2)-
110.57(19). Right: Dimers formed in 2·Br through O−H···Br and
C−H···Br hydrogen bonds.
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structures of aryloxime palladacycles previously reported.46
Compared to the analogous parameters in the free oxime 1, the
C(8)N(1) bond distances are similar (1.276(3)−1.284(3) vs
1.276(3) Å), while the N(1)−O(1) bond distances are
somewhat shorter (1.396(3)−1.409(4) vs 1.415(2) Å). In the
alkenyl(oxime) palladacycles 9a and 10a, the C(10)−C(11)
bond distance (1.344(4) and 1.335(4) Å) is normal for a
C(sp2)−C(sp2) double bond.47
In the oxime 1, the skeleton C(7)−C(8)−C(9)−N(1)−
O(1) is essentially planar and the phenyl ring is almost
perpendicular to that plane (torsion angle 73.59°). The six-
membered oxime palladacycles (Pd(1)−C(1)−C(2)−C(7)−
C(8)−N(1) in complexes 2·Br, 3a, and 5 and Pd(1)−N(1)−
O(1)−C(10)−C(11)−N(2) in 5) adopt a twist boat
conformation. In complexes 9a and 10a, the eight-membered
ring Pd(1)−C(10)−C(11)−C(2)−C(7)−C(8)−N(1) adopts
an almost twist-boat conformation, although the usual
designations of cyclooctane conformations are not strictly
applicable.48 The structures of complexes 3a and 10a reveal the
existence of intramolecular O−H···Br hydrogen bonds; addi-
tionally, the structures of compounds 1−3 and 5 show the
presence of dimers formed by hydrogen bonding: OH···N in 1,
O−H···Br and C−H···Br in 2·Br with participation of an
aromatic CH of the tbbpy ligand, O−H···Br and C−H···Br in
3a with participation of the methylene group, and C−H···Br in
5 with participation of the methylene group. In complex 9a,
chains along the c axis form by C−H···O hydrogen bonding
with the involvement of an aromatic CH group of the tbbpy
ligand and a CO2Me group, while in 10a layers parallel to the bc
plane form through various C−H···O and C−H···Br hydrogen
bonds in which the oxime Me group, an aromatic CH and the
Me group in the picoline ligand, and oxygen atoms from the
CO2Me groups participate.
Figure 3. Left: Thermal ellipsoid representation plot (50%
probability) of complex 3a. Most hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−C(1)
1.994(3), Pd(1)−N(1) 2.029(3), Pd(1)−N(2) 2.050(3), Pd(1)−
Br(1) 2.5836(9), N(1)−C(8) 1.282(4), N(1)−O(1) 1.409(4); C(1)−
Pd(1)−N(1) 87.42(13), C(1)−Pd(1)−N(2) 89.17(13), N(1)−
Pd(1)−Br(1) 91.01(9), N(2)−Pd(1)−Br(1) 92.54(8), C(8)−N(1)−
O(1) 114.8(3), C(8)−N(1)−Pd(1) 127.9(2), O(1)−N(1)−Pd(1)
117.29(19), C(8)−C(7)−C(2) 113.5(3). Right: Dimers formed in 3a
through O−H···Br and C−H···Br hydrogen bonds.
In the crystal structure of 11·picrate, the two monomeric
units display only slightly different parameters. The central six-
membered ring Pd(3)−O(3)−N(5)−Pd(4)−O(4)−N(6)
adopts a slightly twisted boat conformation. Within the
bridging oximato-palladium moieties, the Pd−N bond distances
are similar to those found in the remaining complexes, while
the CN (1.291(4), 1.292(4) Å) are longer and N−O
(1.365(3), 1.374(3) Å) shorter. The parameters within the
Pd(π-allyl) fragment are similar to those found in complexes
containing this subunit.25,44
Figure 4. Left: Thermal ellipsoid representation plot (50%
probability) of complex 5. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Pd(1)−C(1) 1.995(3),
Pd(1)−N(1) 2.036(2), Pd(1)−N(2) 2.151(3), Pd(1)−Br(1)-
2.4249(8), N(1)−C(8) 1.278(4), N(1)−O(1) 1.421(3); C(1)−
Pd(1)−N(1) 86.40(12), N(1)−Pd(1)−N(2) 88.16(10), C(1)−
Pd(1)−Br(1) 91.94(10), N(2)−Pd(1)−Br(1) 93.64(7), C(8)−
N(1)−O(1) 113.6(2), C(8)−C(7)−C(2) 111.4(3), N(1)−C(8)−
C(9) 124.9(3), N(1)−C(8)−C(7) 116.1(3), C(9)−C(8)−C(7)
119.0(3). Right: Dimers formed in 5 through C−H···Br hydrogen
bonds.
NMR Spectra. In complexes 2, 3, 5, and 9−11 the Me9
proton resonance appears in the range 2.14−2.81 ppm, while in
the organic compounds 7 and 8 this resonance is at 2.55−2.81
ppm, obviously deshielded with respect to the oxime 1 (1.85
ppm) and in the oximato complex 4 at 1.16 ppm, appreciably
shielded probably because of both the anisotropic effect of one
of the tolyl rings and the neighbor oximato oxygen. This latter
contribution could explain the shielding on the CH2 resonance
in 4, at 3.48 ppm, with respect to that in the remaining
complexes, in the range 3.67−3.95 ppm. This resonance is
observed as an AB system in the room-temperature spectra of
all complexes, except in 2 and 3b, which display a broad singlet,
suggesting they are fluxional in CDCl3 solution at room
temperature. In fact, in the low-temperature (−58 °C) spectra
of complexes 2, the expected AB system is observed.
In complexes 2·Br, 3a, 5, 9a, and 10a the palladium atom is
in a square planar environment, slightly distorted mainly
because of the small bite of the tbbpy ligand (N(2)−Pd(1)−
N(3) in deg: 78.50(7) in 2·Br, 80.11(8) in 9a) and, second,
because of that of the more flexible six-membered oxime
palladacycle C(1)−Pd(1)−N(1) (in deg: 84.66(8) in 2·Br,
87.42(13) in 3a, 86.40(12) in 5, or C(10)−Pd(1)−N(1):
86.05(9) in 9a, 86.51(9) in 10a). The N(1)−Pd(1)−N(2)
bond angle in the pincer complex 5 is 88.16(10)°. The Pd−C
and Pd−N bond distances in the oxime palladacycle (in the
ranges 1.994(2)−2.011(3) and 2.010(2)−2.036(2) Å, respec-
tively) are similar to those found in the few other crystal
1
Additionally, the room-temperature H NMR spectrum of 2·
Br shows, unlike 2·ClO4, a single resonance for each type of
tbbpy proton in spite of its two halves being inequivalent in the
solid state. At −58 °C, the decoordination/rotation/recoordi-
nation of the tbbpy ligand that makes equal its two halves is
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Figure 5. Top: Thermal ellipsoid representation plot (50% probability) of the cation of complex 9a. Most hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Pd(1)−C(10) 2.000(2), Pd(1)−N(1) 2.010(2), Pd(1)−N(3) 2.0190(19), Pd(1)−N(2) 2.074(2),
N(1)−C(8) 1.284(3), N(1)−O(1) 1.396(3); C(10)−Pd(1)−N(1) 85.05(9), C(10)−Pd(1)−N(3) 98.04(9), N(1)−Pd(1)−N(2) 96.84(8), N(3)−
Pd(1)−N(2) 80.11(8), C(8)−N(1)−O(1) 112.3(2), C(8)−N(1)−Pd(1) 130.66(19), O(1)−N(1)−Pd(1) 116.94(15), C(8)−C(7)−C(2)
124.9(2). Bottom: Chain along the c axis in 9a formed through C−H···O hydrogen bonds.
slow on the NMR time scale. The different behavior of 2·Br
with respect to 2·ClO4 can be explained assuming that the
bromide counterion intervenes in the above-mentioned
fluxional process, binding to Pd and favoring the decoordina-
tion of the tbbpy, which does not occur with the weak donor
perchlorate ion. This difference also explains the differences in
molar conductivity within these complexes. Thus, the molar
conductivity in acetone solution of 2·Br (56 Ω−1·cm2·mol−1) is
rather below the value of 2·ClO4 (140 Ω−1·cm2·mol−1), which
is in the range expected for 1:1 electrolytes.45 The OH
resonance, absent in the NMR spectrum of 4, appears as a
singlet at 9.38−11.78 ppm in the spectra of complexes 2, 3, 9,
and 10. This resonance, which is deshielded with respect to that
in the free oxime 1 (8.35 ppm), appears in the range found for
other aryloxime palladium complexes. Compounds 6−8 show
this resonance between 7.22 and 10.30 ppm. In all the oxime
compounds 2−10 the position of the OH resonance cannot be
rationalized unless the participation of this group in more or
less strong hydrogen bonding is admitted. Compounds of the
type of 7 have no precedent in the literature. We have assigned
the structure of these amidine compounds derived from 1,2-
dihydro-2-hydroxy-3-methylisoquinoline based on their 1H,
13C, HMBC, HMQC, and NOESY NMR spectra. The latter
has been attributed to the anisotropic effect of the exocyclic
CO or CN double bond.20,40 This resonance appears in
7b and 8 at 7.12 and 7.17−7.24 ppm, respectively. The
shielding of this resonance compared to its homologue in 7a
could be a consequence of the anisotropic effect of the Xy
group in these E isomers, as has been previously reported in
other cyclic amidines and amidinium salts.20 Although the
smaller steric hindrance acts generally in favor of the Z isomers,
in 7a and 7b the E disposition could be preferred since it allows
t
the formation of an intramolecular O−H···NR (R = Bu, Xy)
hydrogen bond. Although this type of interaction cannot be
invoked in 8, the protonated form of 7b, its NOESY spectrum
proves it to be also the E isomer. We expected this would be
the most likely result of the protonation of E-7b because, being
that E-8 is expected to form initially, its isomerization into Z-8
would be difficult in view of the partial double-bond character
of the C−N bond, restricting its rotation.
The structure of the alkenyl complex 10b has been
unequivocally established by means of HMBC and HMQC
experiments. The HMBC spectrum shows correlation between
the C11 and both H6 and the Me protons of the CO2Me group
and also between C10 and the phenyl protons, while no
correlation is observed between C10 and H6. These data prove
that the insertion of methyl phenylpropiolate into the Pd−C
bond occurs in the expected manner according to various
studies on the factors, electronic and steric, governing the
regiochemistry of the insertion of alkynes into the Pd−C
bond,20,49 and to the empirical scale proposed for the tendency
of the CR′ moiety of an alkyne RCCR′ to be attached to
CPd.23,30
t
show correlation between H8 and the Bu (7a) or Xy (7b, 8)
methyl protons, proving that, in all cases, the iminobenzoyl
compound forms as the E isomer. The H8 resonance in the 1H
t
NMR spectrum of 7a (8.17 ppm, R = Bu) is similar to that
found for the analogous proton in the isoquinolone 6 (8.34
ppm) and in other cyclic amidines and lactams. Its deshielding
with respect to the normal position for aryl proton resonances
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Figure 7. Thermal ellipsoid representation plot (50% probability) for
the cation of 11·picrate. For simplicity, the hydrogen atoms are
omitted as well as the four tbbpy ligands and the eight phenyl
substituents on the tetraphenylbutadienyl spirane, with the exception
of their nitrogen [N(1)−N(4), N(7), N(8), N(303), and N(304)] and
ipso-carbon [C(71), C881), C(91), C(101), C(241), C(251), C(261),
and C(371)] atoms, respectively. Selected bond lengths (Å) and
angles (deg): Pd(1)−C(1) 2.141(4), Pd(1)−C(2) 2.063(4), Pd(1)−
C(3) 2.182(4), Pd(1)−N(3) 2.106(3), Pd(1)−N(4) 2.101(3),
Pd(2)−C(201) 2.140(4), Pd(2)−C(202) 2.074(4), Pd(2)−C(203)
2.158(4), Pd(2)−N(7) 2.102(3), Pd(2)−N(8) 2.100(3), Pd(3)−O(3)
1.987(2), Pd(3)−N(1) 2.000(3), Pd(3)−N(2) 2.000(3), Pd(3)−N(6)
2.013(3), Pd(4)−O(4) 1.984(2), Pd(4)−N(304) 2.002(3), Pd(4)−
N(303) 2.012(3), Pd(4)−N(5) 2.019(3), O(3)−N(5) 1.365(3),
O(4)−N(6) 1.374(3); C(2)−Pd(1)−N(4) 136.80(13), C(2)−
Pd(1)−N(3) 132.06(13), N(4)−Pd(1)−N(3) 77.66(12), C(2)−
Pd(1)−C(1) 39.01(13), N(4)−Pd(1)−C(1) 175.58(13), N(3)−
Pd(1)−C(1) 106.43(13), C(2)−Pd(1)−C(3) 38.72(14), N(4)−
Pd(1)−C(3) 109.47(13), N(3)−Pd(1)−C(3) 170.77(13), C(1)−
Pd(1)−C(3) 66.29(14), C(202)−Pd(2)−N(8) 134.18(13), C(202)−
Pd(2)−N(7) 137.33(14), N(8)−Pd(2)−N(7) 77.92(12), C(202)−
Pd(2)−C(201) 38.51(13), N(8)−Pd(2)−C(201) 107.63(13), N(7)−
Pd(2)−C(201) 174.43(14), C(202)−Pd(2)−C(203) 38.60(14),
N(8)−Pd(2)−C(203) 172.75(13), N(7)−Pd(2)−C(203)
108.46(14), C(201)−Pd(2)−C(203) 66.04(14), O(3)−Pd(3)−N(2)
171.69(11), O(3)−Pd(3)−N(1) 90.76(11), N(2)−Pd(3)−N(1)
80.93(12), O(3)−Pd(3)−N(6) 91.92(10), N(2)−Pd(3)−N(6)
96.36(11), N(1)−Pd(3)−N(6) 173.53(11), O(4)−Pd(4)−N(304)
89.53(11), O(4)−Pd(4)−N(303) 169.56(11), N(304)−Pd(4)−
N(303) 80.75(12), O(4)−Pd(4)−N(5) 91.86(10), N(304)−Pd(4)−
N(5) 176.18(11), N(303)−Pd(4)−N(5) 97.60(12).
Figure 6. Top: Thermal ellipsoid representation plot (50%
probability) for complex 10a. Most hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−C(10)
2.011(3), Pd(1)−N(1) 2.017(2), Pd(1)−N(2) 2.040(2), Pd(1)−
Br(1) 2.5335(6), N(1)−C(8) 1.276(3), N(1)−O(1), 1.405(3);
C(10)−Pd(1)−N(1) 86.51(9), C(10)−Pd(1)−N(2) 91.33(9),
N(1)−Pd(1)−Br(1) 91.32(6), N(2)−Pd(1)−Br(1) 90.84(6), C(8)−
N(1)−O(1) 113.3(2), O(1)−N(1)−Pd(1) 114.37(15), C(8)−C(7)−
C(2) 124.7(2). Bottom: Layers parallel to the bc plane in 10a formed
through C−H···O and C−H···Br hydrogen bonds.
The 13C{1H} NMR spectra of all complexes show the
expected resonances, although in a few cases some quaternary
carbon nuclei were not observed (see Experimental Section). In
complexes 2, 3, 5, 9, and 10 the Me (C9), CH2 (C7), and C
NO (C8) nuclei give a resonance at 17.9−20.7, 41.4−46.8, and
162.3−169.8 ppm, respectively, while in the oximato complex 4
the C9 and C8 resonances are appreciably shielded (at 16.4 and
150.8 ppm, respectively), probably by the above-mentioned
reasons. In complexes 9 and 10, the alkenyl carbon nuclei C10
and C11 appear at 166.3−174.8 and 130.3−133.7 ppm,
respectively.
IR Spectra. In the IR spectra of compounds 1, 2·ClO4, 3,
and 6−10, the ν(OH) mode is observed as a broad band in the
wide range of 3155−3282 cm−1, which could be justified by the
participation of the OH group in hydrogen bonding, as above-
mentioned in the discussion of the NMR spectra. This band is
absent in the spectra of 4 and 5 and is not observed in the
spectrum of 2·Br. In that of 8, a broad band centered at 3335
cm−1 must include the ν(OH) and ν(NH) absorptions. The
ν(CNO) band is present in all compounds between 1556
and 1616 cm−1, and in some cases it is impossible to assign it
unequivocally because of the presence of one or two additional
bands in the same region attributable to CC or CNR or to
aromatic CC and CN stretching modes. Bands at around 1100
and 620 cm−1 are observed in the spectra of complexes 2·ClO4,
9, and 11·ClO4 assignable to the ν(ClO) and δ(OClO) modes.
The bands νasym and νsym(NO2) characteristic of nitroaromatic
groups, expected to appear in the spectra of 8 and 11·picrate
between 1510−1495 and 1345−1320 cm−1, respectively,
cannot be assigned because of the presence of various other
bands in the same regions. The νasym(CO2) corresponding to
the methoxycarbonyl groups in complexes 9 and 10 appear at
around 1715−1720 cm−1.
HRMS Spectra. The HRMS (ESI+) spectra were measured
for the isoquinoline derivatives 7 and, for 8 and 11, both the
ESI+ and the ESI− spectra. In the ESI+ of complexes 11 the
peaks assigned to the dipalladated species [C73H77N5OPd2]2+
(M2+) and [M − H+]+ were isotopically resolved and their
isotopic resolution is in good agreement with the theoretical
distribution.
CONCLUSION
■
We report the synthesis of the first cyclometalated phenyl-
acetone oxime complexes, inaccessible by the usual orthome-
talation reactions, by oxidative addition of C6H4Br{CH2C-
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mmol) in water (13 mL) were added C6H4Br{CH2C(O)Me}-2 (1 mL,
6.58 mmol) and EtOH (10 mL). The resulting suspension was heated
at 75 °C for 5 h, allowed to cool at room temperature, stirred in an
ice/water bath for 15 min, and filtered. The solid collected was washed
with cold water (3 × 5 mL, 0 °C), dried by suction, and dissolved in
Et2O. The solution was dried over anhydrous MgSO4 and
concentrated under vacuum (5 mL), and pentane (30 mL) was
added. The suspension was filtered, and the solid collected was washed
with pentane and dried by suction to give 1 as a white solid (1.47 g,
6.44 mmol, 98%). Mp: 125 °C. 1H NMR (CDCl3, 400 MHz, 25 °C):
(Me)NOH}-2 to a Pd(0) complex. Their reactivity toward
CO, isocyanides, and alkynes allowed the synthesis of 1,2-
dihydro-1-oxo-2-hydroxy-3-methylisoquinoline, 1,2-dihydro-1-
imino(R)-2-hydroxy-3-methylisoquinolines, i.e., novel amidines
of the isoquinoline series, neutral and cationic eight-membered
alkenyl(oxime) palladacycles, or tetrapalladated species con-
taining a π-allyl-bridging coordinated oximato ligand bearing a
spirocyclic substituent. These results are the first obtained
starting from cyclopalladated oximes. Deprotonation with
KtBuO led to an oximato complex or, in the presence of
BrCH2py, a C,N,N′-oxime ether pincer complex.
3
δ 1.86 (s, 3 H, Me), 3,67 (s, 2 H, CH2), 7.11 (ddd, 1H, H4, JHH = 9
Hz, 3JHH = 7 Hz, 4JHH = 2 Hz), 7.21−7.28 (m, 2 H, H5+H6), 7.56 (dd,
1H, H3, 3JHH = 8 Hz, 4JHH = 1 Hz), 8.35 (s, 1 H, OH). 13C{1H} NMR
(CDCl3, 75 MHz, 25 °C): δ 13.5 (Me), 41.7 (C7), 124.9 (C1 or C2),
127.5 (C5), 128.4 (C4), 130.8 (C6), 132.9 (C3), 136.3 (C1 or C2),
156.5 (C8). IR (cm−1): ν(OH), 3243. Anal. Calcd for C9H10BrNO: C,
47.39; H, 4.42; N, 6.14. Found: C, 47.28; H, 4.59; N, 6.08. Crystals
suitable for an X-ray diffraction study were grown by slow evaporation
of a solution of 1 in a mixture of CHCl3, Et2O, and n-hexane.
Synthesis of [Pd{C,N-C6H4{CH2C(Me)NOH}-2}(tbbpy)]Br
(tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine, 2·Br). A Carius tube
was charged under a nitrogen atmosphere with solid “Pd(dba)2” (505
mg, 0.88 mmol), 1 (200 mg, 0.88 mmol), tbbpy (235 mg, 0.88 mmol),
and dry toluene (20 mL). The mixture was stirred at room
temperature for 15 min and then heated at 65 °C for 4 h. The
resulting greenish suspension was filtered through a short pad of
Celite. The solid plus Celite mixture was dried by suction for 2 h and
stirred with CH2Cl2 (30 mL) for 10 min. The suspension was filtered,
the filtrate was concentrated under vacuum to dryness, and the residue
was dissolved in CH2Cl2 (5 mL). Et2O (12 mL) was slowly added
until the solution became cloudy, and the suspension was filtered
rapidly at this point. On stirring the filtrate for an additional 30 min, a
suspension formed, which was filtered. The solid collected was washed
with Et2O (3 × 3 mL), recrystallized from CH2Cl2/Et2O, and dried,
first by suction and then in a vacuum oven (5 h, 75 °C), to give 2·Br as
a pale yellow solid (282 mg, 0.47 mmol, 53%). Mp: 199 °C (dec). 1H
NMR (CDCl3, 400 MHz, 25 °C): δ 1.42 (s, 18 H, Me, tBu), 2.34 (s, 3
EXPERIMENTAL SECTION
■
General Procedures. When not stated, the reactions were carried
out without precautions to exclude light or atmospheric oxygen or
moisture. Melting points are uncorrected. IR spectra were recorded
using Nujol mulls between polyethylene sheets. NMR spectra were
recorded in 200, 300, 400, or 600 MHz NMR spectrometers. The
NMR assignments were performed, in some cases, with the help of
APT, HMQC, and HMBC experiments. The atom-numbering scheme
used in the Experimental Section is shown in 2·Br for the aryl oxime
ligands in complexes 2−5 and for compounds 6−8 (Scheme 1);
complexes 9 and 11 (Scheme 2) show the numbering scheme used for
the alkenyl oxime and the π-allyl(bridging oximato) ligands in
complexes 9−11, respectively. The tbbpy and pic nuclei are numbered
separately according to the usual rules. Pd(OAc)2, C6H4Br{CH2C-
(O)Me}-2, H2NOH·HCl, XyNC (Xy = C6H3Me2-2,6 = xylyl),
NaClO4·H2O, TfOH (TfO = CF3SO3 = triflate), AgOTf, tbbpy
(4,4′-di-tert-butyl-2,2′-bipyridine), methyl phenylpropiolato, KtBuO
(95%), C2Ph2, BrCH2py·HBr, NaOAc MeCN, dimethyl acetylenedi-
t
carboxylate (DMAD), BuNC, 4-methylpyridine, KOH, anhydrous
MgSO4, and picric acid were obtained from commercial sources.
[Pd2(dba)3]·dba (“Pd(dba)2”, dba = dibenzylideneacetone) was
prepared as previously reported.50 K(picrate) was prepared by adding
an EtOH solution (1 M) of KOH to another containing an equimolar
amount of picric acid in acetone. The suspension was filtered, and the
solid collected was washed successively with a 1:1 mixture of acetone/
Et2O (3 × 3 mL) and Et2O (3 × 3 mL) and dried by suction to give a
deep yellow solid. The synthesis of the oxime C6H4Br{CH2C(Me)
NOH}-2 (1) was previously reported,37 but the ESI-MS was the only
information available. We have improved its synthesis, providing
shorter reaction time and somewhat higher yield, and fully
characterized it including its crystal structure.
X-ray Crystallography. All diffraction measurements were carried
out at 100 K. Data were collected using monochromated Mo Kα
radiation in ω scan and compounds 3a, 5, and 9a in ω and ϕ scans.
The structures were solved by direct methods. All atoms were refined
anisotropically on F2. The OH hydrogens were refined as free, the
methyl hydrogen atoms using a rigid group, and the other hydrogens
using a riding mode. Special features: for 9a, the perchlorate anion is
disordered over two positions, 53:47%; for 11·picrate, three of the tBu
groups of the tbbpy ligands are disordered over two positions, ca.
58:42% and 72:28%, 61:39%. One phenyl ligand is disordered over
two positions, ca. 64:36%. Some of the NO2 groups of the picrate
anions are disordered over two positions. There was a solitary peak of
4.49 e·Å3 at 1.80 Å of an oxygen that was interpreted as an oxygen of
half water. Its H’s were not located so they were not included in the
refinement. There is a poorly resolved region of residual electron
density. This could not be adequately modeled and so was “removed”
using the program SQUEEZE, which is part of the PLATON system.
The void volume per cell was 3283.8 Å3, with a void electron count per
cell of 655. This additional solvent was not taken into account when
calculating derived parameters such as the formula weight, because the
nature of the solvent was uncertain. Further details on crystal data,
data collection, and refinements are summarized in Table 1 in the
Supporting Information.
H, Me9), 3.83 (br s, 2 H, C7), 6.95 (dd, 1 H, H3, 3JHH = 8 Hz, 4JHH
=
1 Hz), 7.02 (td, 1 H, H4, 3JHH = 8 Hz, 4JHH = 1 Hz), 7.07 (td, 1 H, H5,
3JHH = 8 Hz, 4JHH = 1 Hz), 7.49 (m, 2 H, H5 + H5′, tbbpy), 7.51 (dd,
1 H, H6, 3JHH = 8 Hz, 4JHH = 1 Hz), 8.01 (d, 2 H, H3+H3′, tbbpy, 4JHH
= 2 Hz), 8.88 (vbr s, 2 H, H6+H6′, tbbpy), 11.78 (br s, 1H, OH). 1H
t
NMR (CDCl3, 400 MHz, −58 °C): δ 1.427 (s, 9 H, Me, Bu), 1.432
(s, 9 H, Me, tBu), 2.34 (s, 3 H, Me9), 3.88 (AB system, 2 H, CH2, νA =
4.22, νB = 3.54, JAB = 15 Hz), 7.03 (d, 1 H, H3, 3JHH = 7 Hz), 7.07 (t, 1
H, H4, 3JHH = 7 Hz), 7.13 (t, 1 H, H5, 3JHH = 7 Hz), 7.47 (br d, 1 H,
H5 or C5′, tbbpy, 3JHH = 6 Hz), 7.52 (vbr s, 1 H, H5 or H5′, tbbpy),
3
7.57 (d, 1 H, H6, JHH = 7 Hz), 8.02 (br s, 1 H, H3 or H3′, tbbpy),
8.04 (br s, 1 H, H3 or H3′, tbbpy), 8.58 (d, 1 H, H6 or H6′, tbbpy,
3JHH = 6 Hz), 9.14 (d, 1 H, H6 or H6′, tbbpy, 3JHH = 6 Hz), 11.59 (br
s, 1H, OH). 13C{1H} NMR (CDCl3, 75 MHz, 25 °C): δ 18.8 (Me9),
t
30.2 (Me, Bu), 35.4 (C(Me)3), 46.6 (CH2), 118.6 (C3+C3′, tbbpy),
123.6 (C5+C5′, tbbpy), 124.2 (C4), 125.3 (C3), 126.4 (C5), 135.6
(C6), 136.7 (C2), 151.5 (C6+C6′, tbbpy), 151.9 (C1), 154.5 (br,
C2+C2′, tbbpy), 163.9 (C4+C4′, tbbpy), 166.0 (C8). IR (cm−1):
ν(OH), not observed; ν(CNO), 1615. ΛM (Ω−1·cm2·mol−1): 56
(2.8 × 10−4 M, in acetone). Anal. Calcd for C27H34BrN3OPd: C,
53.79; H, 5.68; N, 6.97. Found: C, 53.58; H, 5.75; N, 6.67. Crystals of
2·Br suitable for an X-ray diffraction study were grown by the liquid
diffusion method from acetone/Et2O.
Synthesis of [Pd{C,N-C6H4{CH2C(Me)NOH}-2}(tbbpy)]ClO4
(2·ClO4). To a suspension of 2·Br (103 mg, 0.17 mmol) in acetone
(25 mL) was added NaClO4·H2O (148 mg, 1.05 mmol), and the
reaction mixture was stirred for 4 h. The suspension was concentrated
under vacuum to dryness, the residue was stirred with CH2Cl2 (20
mL), and the suspension was filtered through a short pad of Celite.
The filtrate was concentrated (2 mL), Et2O (15 mL) was added, and
the suspension was filtered. The solid collected was washed with Et2O
(3 × 3 mL) and dried by suction to give 2·ClO4 as a white solid (98
Synthesis of C6H4Br{CH2C(Me)NOH}-2 (1). To a solution of
1
H2NOH·HCl (1.70 g, 24.46 mmol) and NaOAc·3H2O (5.56 g, 40.86
mg, 0.16 mmol, 92%). Mp: 194 °C. H NMR (CDCl3, 400 MHz, 25
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t
t
°C): δ 1.42 (s, 9 H, Me, Bu), 1.43 (s, 9 H, Me, Bu), 2.34 (s, 3 H,
Me9), 3.88 (br s, 2 H, C7H2), 6.98 (dd, 1 H, H3, 3JHH = 7 Hz, 4JHH
C30H31BrNOPPd: C, 56.40; H, 4.89; N, 2.19. Found: C, 56.44; H,
4.99; N, 2.07.
=
2 Hz), 7.04 (td, 1 H, H4, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.09 (td, 1 H, H5,
Synthesis of [Pd{μ-C,N,O-C6H4{CH2C(Me)NO}-2}(PTol3)]2
(4). Solid KtBuO (15 mg, 0.13 mmol) was added to a solution of
3b (70 mg, 0.11 mmol) in CH2Cl2 (5 mL). The suspension was stirred
for 4 h, filtered through a short pad of Celite, and concentrated under
vacuum (1 mL), and pentane (20 mL) was added. Partial
concentration of the solution (10 mL) under vacuum produced a
suspension, which was filtered while cold. The solid collected was
dried by suction to give 4·H2O as a white solid (35 mg, 0.061 mmol,
55%). Concentration of the filtrate to dryness gave a second crop of
the same product (14 mg, 0.024 mmol; total yield 77%). Mp: 232 °C
(dec). 1H NMR (CDCl3, 400 MHz, 25 °C): δ 1.16 (s, 3 H, Me9), 1.67
(s, 2 H, H2O), 2.22 (s, 9 H, Me, Tol), 3.48 (AB system, 2 H, C7, νA =
4.05, νB = 2.91, JAB = 15 Hz), 6.32−6.38 (m, 1 H, Ar), 6.61−6.65 (m, 1
H, Ar), 6.71 (m, 6 H, meta-Tol), 6.76−6.79 (m, 2 H, Ar), 7.18 (m, 6
H, ortho-Tol). 13C{1H} NMR (CDCl3, 75 MHz, 25 °C): δ 16.4
(Me9), 21.3 (Me, Tol), 46.5 (C7), 122.0 (C4), 124.0 (C5), 124.7
3JHH = 7 Hz, JHH = 2 Hz), 7.40 (dd, 1 H, H6, JHH = 7 Hz, JHH = 1
Hz), 7.41 (dd, 1 H, H5 or H5′, tbbpy, 3JHH = 6 Hz, 4JHH = 2 Hz), 7.62
(dd, 1 H, H5 or H5′, tbbpy, 3JHH = 6 Hz, 4JHH = 2 Hz), 8.04 (d, 2 H,
4
3
4
H3+H3′, tbbpy, 4JHH = 2 Hz), 8.47 (d, 1 H, H6 or H6′, tbbpy, 3JHH
=
6 Hz), 8.95 (d, 1 H, H6 or H6′, tbbpy, 3JHH = 6 Hz), 10.06 (br s, 1H,
OH). 1H NMR (CDCl3, 400 MHz, −58 °C): δ 1.42 (s, 9 H, Me, tBu),
t
1.44 (s, 9 H, Me, Bu), 2.34 (s, 3 H, Me9), 3.93 (AB system, 2 H,
C7H2, νA = 4.27, νB = 3.59, JAB = 16 Hz), 7,06−7,15 (m, 3 H,
3
H3+H4+H5), 7.42 (d, H6, JHH = 7 Hz), 7.48 (dd, 1 H, H5 or H5′,
tbbpy, 3JHH = 6 Hz, JHH = 1 Hz), 7.53 (br d, 1 H, H5 or H5′, tbbpy,
4
3JHH = 4 Hz), 8.06 (br s, 2 H, H3+H3′, tbbpy), 8.46 (d, 1 H, H6 or
3
3
H6′, tbbpy, JHH = 6 Hz), 8.92 (d, 1 H, H6 or H6′, tbbpy, JHH = 6
Hz), 10.12 (br s, 1H, OH). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C):
t
δ 18.4 (Me9), 30.2 (Me, Bu), 35.6 (CMe3), 46.4 (C7), 118.6 (C3 or
C3′, tbbpy), 119.2 (C3 or C3′, tbbpy), 123.4 (C5 or C5′, tbbpy),
124.3 (C5 or C5′, tbbpy), 124.6 (C4), 125.6 (C3), 126.6 (C5), 135.4
(C6), 136.2 (C2), 150.8 (C6 or C6′, tbbpy), 151.4 (C1), 151.8 (C6 or
C6′, tbbpy), 153.0 (C2 or C2′, tbbpy), 156.9 (C2 or C2′, tbbpy),
164.4 (C4 or C4′, tbbpy), 164.7 (C2 or C2′, tbbpy), 167.6 (C8). IR
(cm−1): ν(OH), 3172; ν(CNO), 1619; δ(OClO), 624. ΛM (Ω−1·
cm2·mol−1): 140 (5.3 × 10−4 M, in acetone). Anal. Calcd for
C27H34ClN3O5Pd: C, 52.10; H, 5.51; N, 6.75. Found: C, 51.88; H,
5.36; N, 6.57.
Synthesis of SP-4-4-[Pd{C,N-C6H4{CH2C(Me)NOH}-2}Br-
(pic)] (pic = γ-picoline, 3a). A Carius tube was charged, under a
nitrogen atmosphere, with solid “Pd(dba)2” (642 mg, 1.12 mmol) and
1 (254 mg, 1.11 mmol). pic (225 μL, 2.27 mmol) and THF (15 mL)
were successively added. The reaction mixture was stirred at room
temperature for 30 min, then heated at 45 °C for 1 h, and filtered
through a short pad of Celite, and the solution was concentrated under
vacuum to dryness. The residue was stirred with Et2O (8 mL) in an
ice/water bath and filtered. The solid collected was washed with cold
Et2O (4 × 3 mL, 4 °C), dried by suction, and recrystallized from
CH2Cl2/Et2O to give 3a as a white solid (302 mg, 0.71 mmol, 63%),
which was dried, first by suction and then in a vacuum oven (85 °C,
1
3
(C3), 128.2 (d, ipso-C, Tol, JCP = 45 Hz), 128.4 (d, meta-Tol, JCP
=
2
11 Hz), 134.8 (d, ortho-Tol, JCP = 13 Hz), 136.2 (C2), 139.4 (para-
Tol), 140.3 (d, C6, JCP = 12 Hz), 140.9 (C1 or C2), 150.8 (C8).
31P{1H} NMR (CDCl3, 162 MHz, 25 °C): δ 30.2. IR (cm−1): ν(C
NO), 1598. Anal. Calcd for C30H32NO2PPd: C, 62.56; H, 5.60; N,
2.43. Found: C, 62.40; H, 5.37; N, 2.36.
Synthesis of [Pd{C,N,N′-C6H4{CH2C(Me)NOCH2(C5H4N-2)}-
2}Br] (5). To a suspension containing KtBuO (64.2 mg, 0.54 mmol)
and BrCH2py·HBr (70 mg, 0.27 mmol) in CH2Cl2 (20 mL) was added
complex 3a (113 mg, 0.26 mmol). The suspension was stirred for 2.5 h
and filtered through a short pad of Celite, the solution was
concentrated under vacuum to 5 mL, and Et2O (15 mL) was added.
The resulting suspension was filtered, and the solid was washed with
Et2O (3 × 3 mL) and dried, first by suction and then in a vacuum oven
at 80 °C for 5 h to give 5 as a pale yellow solid (62 mg, 0.15 mmol,
1
55%). Mp: > 230 °C (dec). H NMR (CDCl3, 300 MHz, 25 °C): δ
2.22 (s, 3 H, Me9), 3.87 (s, 2 H, C7), 5.46 (s, 2 H, CH2py), 6.89−6.98
(m, 3 H, Ar), 7.38 (d, 1 H, H3, py, 3JHH = 8 Hz), 7.44 (ddd, 1 H, H5,
py, 3JHH = 7 Hz, 3JHH = 5 Hz, 4JHH = 1 Hz), 7.87 (td, 1 H, H4, py, 3JHH
= 8 Hz, 4JHH = 2 Hz), 7.92 (m, 1 H, Ar), 9.24 (dd, 1 H, H6, py, 3JHH
=
5 Hz, 4JHH = 1 Hz). 13C{1H} NMR (CDCl3, 75 MHz, 25 °C): δ 18.7
(Me9), 46.8 (C7), 75.1 (CH2-py), 124.17 (C3, py), 124.21 (C, Ar),
125.2 (C5, py), 125.4 (C, Ar), 126.4 (C3), 133.1 (C1 or C2), 138.9
(C4, py), 139.7 (C1 or C2), 140.8 (C, Ar), 152.9 (C6, py), 153.5 (C2,
1
5h). Mp: 162 °C (dec). H NMR (CDCl3, 400 MHz, 25 °C): δ 2.23
(s, 3 H, Me, pic), 2.40 (s, 3 H, Me9), 3.86 (s, 2 H, C7), 6.33 (m, 1 H,
Ar), 6.70−6.76 (m, 1 H, Ar), 6.95 (m, 2 H, Ar), 7.14 (m, 2 H, H3,
pic), 8.58 (m, 2 H, H2, pic), 9.38 (s, 1 H, OH). 13C{1H} NMR
(CDCl3, 100 MHz, 25 °C): δ 18.2 (Me9), 21.2 (Me, pic), 46.2 (CH2),
124.6 (C, Ar), 125.6 (C, Ar), 125.9 (C3, pic), 126.4 (C, Ar), 134.7
(C1 or C2), 134.8 (C, Ar), 145.3 (C1 or C2), 150.2 (C4, pic), 152.9
(C2, pic), 162.3 (C8). IR (cm−1): ν(OH), 3175; ν(CNO), 1616.
Anal. Calcd for C15H17BrN2OPd: C, 42.13; H, 4.01; N, 6.55. Found:
C, 42.23; H, 3.96; N, 6.32. Crystals of 3a suitable for an X-ray
diffraction study were grown by the liquid diffusion method from
CHCl3/n-hexane.
Synthesis of SP-4-4-[Pd{C,N-C6H4{CH2C(Me)NOH}-2}Br-
(PTol3)] (Tol = C6H4Me-4, 3b). Solid PTol3 (69 mg, 0.23 mmol)
was added to a solution of 3a (91 mg, 0.21 mmol) in CH2Cl2 (5 mL).
The solution was stirred for 1 h and concentrated under vacuum (1
mL), pentane (15 mL) was added, and the suspension was filtered.
The solid collected was washed with pentane (2 × 3 mL) and dried by
suction to give 3b as a yellow solid (116 mg, 0.18 mmol, 85%). Mp:
py), 162.3 (C8). IR (cm−1): ν(CNO) + (ν(CC) + ν(CN))aromatic
,
1601, 1569, 1558. Anal. Calcd for C15H15BrN2OPd: C, 42.33; H, 3.55;
N, 6.58. Found: C, 42.27; H, 3.38; N, 6.65. Crystals of 5 suitable for an
X-ray diffraction study were grown by the liquid diffusion method
from CDCl3/Et2O.
Synthesis of 1,2-Dihydro-1-oxo-2-hydroxy-3-methylisoqui-
noline (6). A solution of 3a (71.4 mg, 0.17 mmol) in CHCl3 (8 mL)
was stirred for 5 h in a Carius tube under a CO pressure of 1.4 bar.
The resulting suspension was filtered through a short pad of Celite to
remove some Pd(0), and the solution was concentrated under vacuum
to dryness to give a 1:1 mixture (84% yield) of 6 and [picH]Br. A
sample of pure 6, used for its characterization by 1H NMR, was
obtained by extracting the mixture with Et2O and concentrating the
1
extract to dryness. H NMR (CDCl3, 400 MHz, 25 °C): δ 2.55 (d, 3
4
H, Me9, JHH = 1 Hz), 6.47 (s, 1 H, H4), 7.46 (ddd, 1H, H6 or H7,
3JHH = 8 Hz, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.52 (d, 1H, H5, 3JHH = 8 Hz),
7,63 (ddd, 1H, H6 or H7, 3JH4H = 8 Hz, 3JHH = 7 Hz, 4JHH = 1 Hz), 8.34
1
220 °C (dec). H NMR (CDCl3, 400 MHz, 25 °C): δ 2.22 (s, 3 H,
Me9), 2.34 (s, 9 H, Me, Tol), 3.82 (s, 2 H, C7), 6.33 (t, 1 H, H5, 3JHH
3
4
(ddd, 1H, H8, JHH = 8 Hz, JHH = 1 Hz, JHH = 1 Hz), 10.30 (vbr s,
OH).
3
4
= 7 Hz), 6.62 (“t”, 1 H, H6, JHH ≈ JHP = 7 Hz), 6.73 (t, 1 H, H4,
3JHH = 7 Hz), 6.87 (dd, 1 H, H3, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.11 (m, 6
Synthesis of 1,2-Dihydro-1-imino(R)-2-hydroxy-3-methyli-
4
t
t
H, meta-Tol), 7.43 (m, 6 H, ortho-Tol), 9.66 (d, 1 H, OH, JHP = 2
soquinoline (R = Bu (7a), Xy (7b)). BuNC (for 7a, 75 μL, 0.65
mmol) or XyNC (for 7b, 69 mg, 0.53 mmol) was added to a solution
of 2·ClO4 (for 7a, 200 mg, 0.32 mmol; for 7b, 166 mg, 0.28 mmol) in
CH2Cl2 (20 mL). The resulting solution was stirred for 40 (7a) or 48
h (7b) and concentrated under vacuum to ca. 4 mL. Pentane (20 mL)
was added, and the resulting suspension was filtered. The solid was
dissolved in CH2Cl2 (1 mL), pentane (10 mL) was added, and the
suspension was filtered. After repeating this two more times, the
Hz). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ 17.8 (Me9), 22.3
4
(Me, Tol), 46.7 (C7), 123.6 (C4), 125.5 (d, C5, JCP = 5 Hz), 126.5
(C3), 127.9 (d, ipso-Tol, 1JCP = 53 Hz), 128.6 (d, meta-Tol, 3JCP = 11
Hz), 134.7 (d, ortho-Tol, 2JCP = 12 Hz), 136.2 (C2), 137.9 (d, C6, 3JCP
= 13 Hz), 140.6 (d, para-Tol, 4JCP = 2 Hz), 150.5 (d, C1, 2JCP = 2 Hz),
161.6 (C8). 31P{1H} NMR (CDCl3, 162 MHz, 25 °C): δ 33.3. IR
(cm−1): ν(OH), 3155; ν(CNO), 1597. Anal. Calcd for
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combined filtrates were concentrated to dryness, the residue was
extracted with pentane (4 × 4 mL), and the combined extracts were
concentrated under vacuum to dryness. For 7a, the yellowish oil
obtained was chromatographed on a silica column using a 4:1 EtOAc/
Et2O mixture as the eluent. The solution was concentrated to dryness,
and the residue was dissolved in CH2Cl2 and washed with H2O (3 ×
15 mL). The organic layer was dried over anhydrous MgSO4, filtered,
and concentrated to dryness. The residue was extracted with pentane
(3 × 3 mL), and the extracts were concentrated under vacuum to
dryness to give 7a as an off-white solid (70 mg, 0.30 mmol, 95%). For
7b, the residue was chromatographed on a silica column using a 2:1
acetone/n-hexane mixture as the eluent. The solution was concen-
trated to dryness to give 7b as a pale yellow solid (54.2 mg, 0.19 mmol,
74%).
C7, νA = 3.87, νB = 3.72, JAB = 19 Hz), 3.88 (s, 3 H, CO2Me), 6.97−
7.01 (m, 2 H, H5+H6), 7.06 (m, 1 H, H4), 7.22 (“d”, 1 H, H3), 7.46
(dd, 1 H, H5 or H5′, tbbpy, 3JHH = 6 Hz, 4JHH = 2 Hz), 7.50 (dd, 1 H,
H5 or H5′, tbbpy, 3JHH = 6 Hz, 4JHH = 2 Hz), 7.80 (d, 1 H, H3 or H3′,
4
4
tbbpy, JHH = 2 Hz), 7.81 (d, 1 H, H3 or H3′, tbbpy, JHH = 2 Hz),
8.16 (d, 1 H, H6 or H6′, tbbpy, 3JHH = 6 Hz), 8.64 (d, 1 H, H6 or H6′,
3
tbbpy, JHH = 6 Hz), 10,05 (s, 1 H, OH). 13C{1H} NMR (CDCl3, 75
t
MHz, 25 °C): δ 20.5 (Me9), 30.1 (Me, Bu), 35.6 (C(Me)3), 35.7
(C(Me)3), 42.0 (C7), 52.1 (CO2Me), 52.3 (CO2Me), 118.8 (C3 or
C3′, tbbpy), 119.0 (C3 or C3′, tbbpy), 123.8 (C5 or C5′, tbbpy),
124.6 (C5 or C5′, tbbpy), 127.5 (C5), 127.7 (C4), 128.0 (C6), 131.2
(C3), 131.6 (C11), 133.6 (C2), 142.6 (C1), 149.5 (C6 or C6′, tbbpy),
152.1 (C6 or C6′, tbbpy), 153.0 (C2 or C2′, tbbpy), 156.0 (C2 or C2′,
tbbpy), 161.4 (C12 or C14), 164.8 (C4 or C4′, tbbpy), 164.9 (C4 or
C4′, tbbpy), 169.0 (C10−Pd), 169.8 (C8), 170.8 (C12 or C14). ΛM
(Ω−1·cm2·mol−1): 134 (4.5 × 10−4 M in acetone). IR (cm−1): ν(OH),
3282; ν(CO), 1713; ν(ClO) 1098; δ(OClO), 625. Anal. Calcd for
C33H40ClN3O9Pd: C, 51.84; H, 5.27; N, 5.50. Found: C, 51.55; H,
5.22; N, 5.50. Crystals of 9a suitable for an X-ray diffraction study were
grown by the liquid diffusion method from CDCl3 and pentane.
Synthesis of SP-4-4-[Pd{C,N-C(R)C(CO2Me)C6H4{CH2C-
(Me)NOH}-2}Br(pic)] (R = CO2Me (10a), Ph (10b)). The
appropriate alkyne (for 10a, DMAD, 35 μL, 0.28 mmol; for 10b,
methyl phenylpropiolate, 41 μL, 0.27 mmol) was added to a solution
of complex 3a (for 10a, 118 mg, 0.28 mmol; for 10b, 115 mg, 0.27
mmol) in CH2Cl2 (10 mL), and the reaction mixture was stirred for 6
h. The solution was filtered through a short pad of Celite and
concentrated under vacuum (4−5 mL), Et2O (20 mL) was added, and
the resulting suspension was filtered. The solid collected was washed
with Et2O (3 × 3 mL) and dried, first by suction and then in a vacuum
oven (10a, 55 °C, 10 h; 10b, 75 °C, 5 h), to give the title complex as a
pale yellow solid.
7a. Mp: 80 °C. 1H NMR (CDCl3, 400 MHz, 25 °C): δ 1.42 (s, 9 H,
Me, tBu), 2.66 (d, 3 H, Me9, 4JHH = 1 Hz), 6,68 (br s, 1 H, H4), 7.22
(s, 1H, OH), 7.44−7.52 (m, 2 H, H6+H7), 7.62 (m, 1 H, H5), 8.17
(m, 1 H, H8). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ 18.6
t
(Me), 31.7 (Me, Bu), 56.9 (CMe3), 115.3 (C4), 123.2 (C8a), 125.8
(C7), 126.0 (C5+C8), 128.3 (C6), 130.0 (C4a), 143.4 (C3), 149.9
(C1). IR (cm−1): ν(OH), 3232; ν(CCarom + CNtBu), 1556, 1495.
HRMS (ESI+, m/z): found 231.1498, calcd for C14H18N2O [M + H]+
231.1492. Error: 2.47 ppm.
7b. Mp: 147 °C. 1H NMR (CDCl3, 400 MHz, 25 °C): δ 2.17 (s, 6
4
H, Me, Xy), 2.73 (d, 3 H, Me9, JHH = 0.4 Hz), 7.02 (br s, 1 H, H4),
7.05 (ddd, 1 H, H7, 3JHH = 8 Hz, 3JHH = 7 Hz, 4JHH = 1 Hz), 7.12 (m, 1
H, H8), 7.16 (m, 2 H, meta-Xy), 7.22 (m, 1 H, para-Xy), 7.40 (ddd, 1
3
3
4
H, H6, JHH = 8 Hz, JHH = 7 Hz, JHH = 1 Hz), 7.58 (br d, 1 H, H5,
3JHH = 8.0 Hz), 9.43 (br s, 1 H, OH). 13C{1H} NMR (CDCl3, 100
MHz, 25 °C): δ 18.4 (Me), 18.6 (Me, Xy), 111.1 (C4), 117.1 (C8a),
121.7 (C8), 125.9 (C7), 126.5 (C5), 127.4 (para-C, Xy), 128.6 (C6),
128.7 (meta-C, Xy), 130.7 (C4a), 136.3 (ortho-C, Xy), 137.3 (ipso-C,
10a. Yield: 132 mg, 0.23 mmol, 84%. Mp: 184 °C (dec). 1H NMR
(CDCl3, 400 MHz, 25 °C): δ 2.22 (s, 3 H, Me9), 2.34 (s, 3 H, Me,
pic), 3.63 (s, 3 H, CO2Me), 3.70 (AB system, 2 H, C7, νA = 3.84, νB =
3.55, JAB = 18 Hz), 3.84 (s, 3 H, CO2Me), 7.05 (d, 2 H, H3, pic), 7.10
Xy), 142.6 (C3), 145.9 (C1). IR (cm−1): ν(OH), 3157; ν(CCarom
+
CNXy), 1567, 1516. HRMS (ESI+, m/z): found 279.1501, calcd for
C18H18N2O [M + H]+ 279.1492. Error: 3.23 ppm.
Synthesis of [1,2-Dihydro-1-xylyliminium-2-hydroxy-3-
methylisoquinoline]picrate (8). Picric acid (27 mg, 0.12 mmol)
was added to a solution of 7b (32 mg, 0.12 mmol) in CH2Cl2 (8 mL).
The reaction mixture was stirred for 30 min and concentrated under
vacuum to ca. 1 mL, and Et2O (12 mL) was added. The resulting
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 (5 h,
75 °C), to give 8 (45 mg, 0.09 mmol, 77%) as a yellow solid. Mp: 181
°C. 1H NMR (CDCl3, 400 MHz, 25 °C): δ 2.15 (s, 6 H, Me, Xy), 2.81
(s, 3 H, Me9), 7.07 (s, 1 H, H4), 7.17−7.24 (m, 4 H, H8 + Ar + meta-
Xy), 7.31 (dd, 1 H, para-Xy, 3JHH = 8 Hz, 3JHH = 7 Hz), 7.66−7.71 (m,
2 H, Ar), 8.88 (s, 2 H, picrate), 8,99 (br s, 1 H, NH), 9.59 (vbr s, 1 H,
OH). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ 17.9 (Me), 18.2
(Me, Xy), 112.2 (C4), 117.1 (C8a), 124.3 (C5, C6, C7 or C8), 126.0
(C, picrate), 127.2 (C5, C6, C7, or C8), 127.7 (C5, C6, C7, or C8),
129.2 (para-C, Xy), 129.4 (meta-C, Xy), 130.3 (C, picrate), 133.4 (C5,
C6, C7, or C8), 134.6 (ipso-C, Xy), 135.8 (C4a), 135.9 (ortho-C, Xy),
141.4 (ortho-C, picrate), 142.0 (C3), 149.5 (C1), 160,3 (C, picrate).
ΛM (Ω−1·cm2·mol−1): 64 (5.03 × 10−4 M in acetone). IR (cm−1):
ν(OH + NH), 3335 br. HRMS (ESI+, m/z): found 279.1499, calcd for
C18H19N2O [M]+ 279.1492. Error: 2.45 ppm. HRMS (ESI−, m/z):
found 227.9904, calcd for C6H2N3O7 (picrate) 227.9898. Error: 2.57
ppm.
Synthesis of [Pd{C,N-C(CO2Me)C(CO2Me)C6H4{CH2C(Me)
NOH}-2}(tbbpy)]ClO4 (9a). Dimethyl acetylenedicarboxylate (200
μL, 1.59 mmol) was added to a solution of 2·ClO4 (112 mg, 0.18
mmol) in CH2Cl2 (10 mL). The reaction mixture was stirred for 40 h
and filtered through a short pad of Celite, the filtrate was concentrated
under vacuum (2 mL), Et2O (20 mL) was added, and the resulting
suspension was filtered. The solid collected was washed with Et2O (3
× 3 mL), recrystallized from CHCl3/pentane, and dried, first by
suction and then in a vacuum oven (80 °C, 5 h), to give 9a as a pale
yellow solid (126 mg, 0.16 mmol, 92%). Mp: 179 °C (dec). 1H NMR
(CDCl3, 400 MHz, 25 °C): δ 1.36 (s, 9 H, Me, tBu), 1.40 (s, 9 H, Me,
tBu), 2.38 (s, 3 H, Me9), 3.75 (s, 3 H, CO2Me), 3.80 (AB system, 2 H,
3
3
4
(d, 1 H, H6, JHH = 8 Hz), 7.39 (td, 1 H, H5, JHH = 7 Hz, JHH = 2
Hz), 7.42 (m, 1 H, H3), 7.47 (ddd, 1 H, H4, 3JHH = 8 Hz, 3JHH = 7 Hz,
4JHH = 1 Hz), 8.14 (d, 2 H, H2, pic), 8.39 (s, 1 H, OH). 13C{1H}
NMR (CDCl3, 75 MHz, 25 °C): δ 20.7 (Me9), 21.1 (Me, pic), 41.4
(C7), 51.9 (C15), 52.0 (C13), 125.6 (C3, pic), 127.1 (C5), 128.4
(C4), 128.6 (C6), 131.7 (C3), 131.8 (C11), 134.8 (C2), 141.9 (C1),
150.3 (C4, pic), 152.0 (C2, pic), 160.8 (C12), 166.3 (C10), 169.1
(C8), 170.0 (C14). IR (cm−1): ν(OH), 3198; ν(CO), 1713, 1701.
Anal. Calcd for C21H23BrN2O5Pd: C, 44.27; H, 4.07; N, 4.92. Found:
C, 43.98; H, 3.84; N, 4.86. Crystals of 10a suitable for an X-ray
diffraction study were grown by the liquid diffusion method from
CDCl3 and Et2O.
10b. Yield: 127 mg, 0.22 mmol, 80%. Mp: 173 °C. 1H NMR
(CDCl3, 600 MHz, 25 °C): δ 2.29 (s, 3 H, Me9), 2.33 (s, 3 H, Me,
pic), 3.42 (s, 3 H, CO2Me), 3.77 (AB system, 2 H, C7, νA = 3.96, νB =
3.57, JAB = 17 Hz), 6.96 (d, 2 H, H3, pic), 6.98 (m, 2 H, ortho-Ph),
7.27−7.30 (m, 3 H, meta- + para-Ph), 7.31−7.33 (m, 1 H, H6), 7.42−
7.44 (m, 1 H, H3), 7.45−7.48 (m, 2 H, H4+H5), 7.82 (d, 2 H, H2,
pic), 8.74 (s, 1 H, OH). 13C{1H} NMR (CDCl3, 75 MHz, 25 °C): δ
20.6 (Me9), 21.0 (Me, pic), 41.4 (C7), 51.2 (C13), 125.4 (C3, pic),
126.0 (ortho-CH, Ph), 126.4 (para-C, Ph), 127.1 (C5), 128.0 (C4 +
meta-C, Ph), 129.2 (C6), 130.3 (C11), 131.4 (C3), 134.6 (C2), 142.2
(C1), 143.0 (ipso-C, Ph) 149.8 (C4, pic), 151.6 (C2, pic), 162.3
(C12), 168.4 (C8), 174.8 (C10). IR (cm−1): ν(OH), 3223; ν(CO),
1720. Anal. Calcd for C25H25BrN2O3Pd: C, 51.09; H, 4.29; N, 4.77.
Found: C, 50.88; H, 4.22; N, 4.73.
Synthesis of SP-4-4-[Pd{C,N-C(CO2Me)C(CO2Me)-
C6H4{CH2C(Me)NOH}-2}Br(PTol3)] (10c). Solid PTol3 (56.2 mg,
0.18 mmol) was added to a solution of 10a (105 mg, 0.18 mmol) in
CH2Cl2 (5 mL), and the reaction mixture was stirred for 4 h. The
solution was concentrated under vacuum (1 mL), pentane (15 mL)
was added, and the suspension was filtered. The solid collected was
dissolved in CH2Cl2 (1 mL), n-hexane (10 mL) was added, and the
solution was kept at 4 °C overnight. The resulting suspension was
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Organometallics
Article
filtered, and the solid collected was dried by suction to give 10c as a
pale yellow solid (63 mg, 0.08 mmol, 45%). Concentration of the
filtrate to dryness gave a second crop of the same compound (38 mg,
0.05 mmol; total yield 72%). Mp: 193 °C (dec). H NMR (CDCl3,
400 MHz, 25 °C): δ 2.18 (s, 3 H, Me9), 2.36 (s, 9 H, Me, Tol), 3.56
(s, 3 H, CO2Me), 3.59 (s, 3 H, CO2Me), 3.64 (AB system, 2 H, C7, νA
1252.4143. Error = 2.48 ppm. (ESI−, m/z): calcd for ClO4− 98.9491,
found 98.9493. Error = 2.32 ppm.
Synthesis of [{Pd(tbbpy)}2{μ-N,O-{η3-C6H4(C4Ph4){CH2C-
(Me)NO}}}]2(picrate)4 (11·picrate). To a suspension of 11·ClO4
(102.0 mg, 0.04 mmol) in acetone (50 mL) was added excess
potassium picrate (198 mg, 0.74 mmol). The solution was stirred for 4
h and concentrated under vacuum to dryness. The residue was stirred
with CH2Cl2 (25 mL), and the suspension was filtered through a short
pad of Celite. The solution was concentrated under vacuum to 2 mL,
Et2O (15 mL) was added, and the suspension was filtered. The solid
was washed with Et2O (3 × 3 mL) and dried, first by suction and then
in a vacuum oven (80 °C, 5h), to give a 1:3 mixture of 11·ClO4 and
11·picrate (109 mg), which was recrystallized repeatedly from CHCl3
and Et2O, giving a small crop of pure 11·picrate. Single crystals of this
complex suitable for an X-ray structure determination were grown
from the above-mentioned 1:3 mixture by the liquid diffusion method
1
= 3.80, νB = 3.48, JAB = 18 Hz), 5.77 (dd, 1 H, H6, 3JHH = 8 Hz, 4JHH
=
3
4
1 Hz), 7.07 (td, 1H, H5, JHH = 8 Hz, JHH = 1 Hz), 7.12 (m, 6 H,
3
meta-Tol), 7.25 (m, 6 H, ortho-Tol) 7.35 (dd, 1 H, H3, JHH = 8 Hz,
4JHH = 1 Hz), 7.40 (td, 1 H, H4, 3JHH = 8 Hz, 4JHH = 1 Hz), 9.05 (d, 1
H, OH, 4JHP = 2 Hz). 13C{1H} NMR (CDCl3, 75 MHz, 25 °C): δ 19.9
(4, Me9, 4JCP = 2 Hz), 21.5 (Me, Tol), 41.3 (C7), 51.6 (CO2Me), 51.7
1
(CO2Me), 126.9 (d, ipso-C, Tol, JCP = 56 Hz), 127.3 (C4 or C6),
127.7 (C4 or C6), 128.5 (d, meta-Tol, 3JCP = 12 Hz),131.4 (C3), 133.7
2
(d, C11), 133.8 (C2), 135.1 (d, ortho-Tol, JCP = 11 Hz), 140.9 (d,
para-Tol, 4JCP = 2 Hz), 142.8 (C1), 162.7 (C12), 166.7 (d, C8, 3JCP
=
1
using CH2Cl2 and Et2O. Mp: 160 °C (dec). H NMR (CDCl3, 400
3
3 Hz), 169.4 (d, C14, JCP = 4 Hz), 170.6 (C10). 31P{1H} NMR
(CDCl3, 162 MHz, 25 °C): δ 20.1. IR (cm−1): ν(OH), 3233; ν(CO),
1712, 1702. Anal. Calcd for C36H37BrNO5Pd: C, 55.37; H, 4.78; N,
1.79. Found: C, 55.31; H, 4.84; N, 1.71.
MHz, 25 °C): δ 1.12 (s, 9 H, Me, tBu), 1.16 (s, 9 H, Me, tBu), 1.21 (s,
t
t
9 H, Me, Bu), 1.37 (s, 9 H, Me, Bu), 1.83 (s, 3 H, Me9), 3.86 (AB
system, 2 H, C7, νA = 4.43, νB = 3.29, JAB = 19 Hz), 5.15 (dd, 1 H, H3,
3JHH = 7 Hz, 4JHH = 1 Hz), 5.88 (t, 1 H, H1, 3JHH = 6 Hz), 6.09−6.15
(m, 3 H, H6 + Ph), 6.27 (m, 3 H, Ph), 6.42 (t, 1 H, H2, 3JHH = 6 Hz),
6.56 (m, 2 H, Ph), 6.94 (m, 2 H, Ph), 7.00 (m, 2 H, Ph), 7.04 (dd, 1
Synthesis of [{Pd(tbbpy)}2{μ-N,O-{η3-C6H4(C4Ph4){CH2C-
(Me)NO}}}]2 (ClO4)4 (11·ClO4). To a solution of 2·ClO4 (328
mg, 0.53 mmol) in CHCl3 (15 mL) was added diphenyl acetylene
(288 mg, 1.58 mmol), and the solution was heated in a Carius tube at
60 °C for 48 h. The resulting suspension was filtered, the solid
collected was washed with CHCl3 (3 × 3 mL), dried by suction, and
dissolved in acetone (35 mL), and the solution was filtered through a
short pad of Celite. The solution was concentrated under vacuum (5
mL), Et2O (15 mL) was added, and the suspension was filtered. The
solid collected was washed with Et2O (3 × 3 mL) and dried, first by
suction and then in a vacuum oven (80 °C, 5 h), to give 11·ClO4 as a
3
4
H, H5−H5‴, tbbpy, JHH = 6 Hz, JHH = 2 Hz), 7.11 (m, 2 H, Ph),
7.16 (m, 2 H, Ph), 7.25−7.30 (m, 4 H, Ph), 7.48 (m, 3 H, tbbpy), 7.52
3
4
(dd, 1 H, H5−H5‴, tbbpy, JHH = 6 Hz, JHH = 2 Hz), 7.73 (d, 1 H,
H6−H6‴, tbbpy, 3JHH = 6 Hz), 7.85 (d, 1 H, H3−H3‴, tbbpy, 4JHH
=
2 Hz), 7.94 (d, 1 H, H3−H3‴, tbbpy, 4JHH = 2 Hz), 8.33 (d, 1 H, H6−
3
4
H6‴, tbbpy, JHH = 6 Hz), 8.34 (d, 1 H, H3−H3‴, tbbpy, JHH = 2
Hz), 8.51 (d, 1 H, H3−H3‴, tbbpy, 4JHH = 2 Hz), 8.65 (d, 1 H, H6−
3
H6‴, tbbpy, JHH = 6 Hz), 8.66 (s, 4 H, meta-picrate), 9.21 (d, 1 H,
H6−H6‴, tbbpy, JHH = 6 Hz). 13C{1H} NMR (CDCl3, 75 MHz, 25
3
1
pale yellow solid (160 mg, 0.06 mmol, 42%). Mp: >250 °C (dec). H
°C): δ 17.8 (Me9), 29.79 (Me, tBu), 29.81 (Me, tBu), 30.0 (Me, tBu),
NMR (CD3CN, 600 MHz, 25 °C): δ 1.22 (s, 9 H, Me, tBu), 1.26 (s, 9
H, Me, tBu), 1.34 (s, 9 H, Me, tBu), 1.50 (s, 9 H, Me, tBu), 2.14 (s, 3
H, Me9), 3.95 (AB part of an ABX system, 2 H, C7, νA = 4.48, νB =
3.41, JAB = 19 Hz, JAX = 2 Hz, JBX = 0 Hz), 5.45 (dd, 1 H, H3, 3JHH = 7
t
30.1 (Me, Bu), 35.5 (CMe3), 35.8 (CMe3), 36.0 (CMe3), 39.3 (C7),
66.9 (C1), 71.3 (C4), 79.7 (C3), 104.4 (C2), 118.5 (C3−C3‴, tbbpy),
118.8 (C3−C3‴), 120.4 (C3−C3‴, tbbpy), 121.8 (C3−C3‴, tbbpy),
122.3 (C5−C5‴, tbbpy), 124.8 (C5−C5‴, tbbpy), 125.1 (C5−C5‴,
tbbpy), 125.28 (C6), 125.33 (ipso-C or para-C, picrate), 125.9 (C5−
C5‴, tbbpy), 126.1 (meta-C, picrate), 127.3 (C, Ph), 127.7 (C, Ph),
128.0 (C, Ph), 128.1 (C, Ph), 128.3 (C, Ph), 128.4 (C, Ph), 129.2 (C,
Ph), 129.5 (C, Ph), 129.7 (C, Ph), 129.8 (C, Ph), 133.5 (C5), 133.8
(ipso-C, Ph), 134.1 (ipso-C, Ph), 134.3 (ipso-C, Ph), 134.6 (ipso-C,
Ph), 142.1 (C10 and/or C13), 142.2 (ortho-C, picrate), 146.8 (C11 or
C12), 147.1 (C11 or 12), 150.3 (C6−C6‴, tbbpy), 151.0 (C6−C6‴,
tbbpy), 152.8 (C6−C6‴, tbbpy), 153.6 (C2−C2‴, tbbpy), 153.6
(C2−C2‴, tbbpy), 153.8 (C6−C6‴), 154.4 (C2−C2‴), 155.8 (C2−
C2‴), 158.7 (C8), 162.0 (ipso-C or para-C, picrate), 163.6 (C4−C4‴,
tbbpy), 165.1 (C4−C4‴, tbbpy), 166.8 (C4−C4‴, tbbpy), 167.1
(C4−4‴, tbbpy). ΛM (Ω−1·cm2·mol−1): 210 (1.8 × 10−4 M in
acetone). IR (cm−1): ν(CN), 1634. Anal. Calcd for
C170H162N22O30Pd4: C, 59.72; H, 4.78; N, 9.01. Found: C, 59.44; H,
4.75; N, 8.71. HRMS (ESI+, m/z): calcd for the monomer
[C73H77N5OPd2]2+ (M2+) 626.7118, found 626.7137. Error = 3.03
ppm. Calcd for [M − H+]+ 1252.4174, found 1252.4203. Error = 2.32
ppm. (ESI−, m/z): calcd for (C6H2N3O7)−, picrate, 227.9898, found
227.9900. Error = 0.95 ppm.
3
Hz, 4JHH = 1 Hz), 5.54 (td, 1 H, H1, JHH = 6 Hz, 4JHH = 1 Hz), 5.94
(m, 2 H, Ph), 6.11 (m, 1 H, Ph), 6.15 (m, 3 H, H6 + Ph), 6.43 (t, 1 H,
H2, 3JHH = 6 Hz), 6.77 (m, 2 H, Ph), 6.89 (m, 2 H, Ph), 7.05 (m, 1 H,
Ph), 7.09 (m, 2 H, Ph), 7.16 (m, 2 H, Ph), 7.26 (dd, 1 H, H5−H5‴,
tbbpy, 3JHH = 6 Hz, 4JHH = 2 Hz), 7.41−7.44 (m, 3 H, Ph), 7.46−7.49
(m, 6 H (4 Ph + 2 H5−H5‴, tbbpy)), 7.64 (dd, 1 H, H5−H5‴, tbbpy,
3JHH = 6 Hz, 4JHH = 2 Hz), 7.97 (d, 1 H, H3−H3‴, 4JHH = 2 Hz), 8.02
3
4
(d, 1 H, H6−H6‴, JHH = 6 Hz), 8.07 (d, 1 H, H3−H3‴, JHH = 2
Hz), 8.09 (d, 1 H, H6−H6‴, tbbpy, 3JHH = 6 Hz), 8.16 (d, 1 H, H3−
4
4
H3‴, tbbpy, JHH = 2 Hz), 8.20 (d, 1 H, H3−H3‴, tbbpy, JHH = 2
Hz), 8.25 (d, 1 H, H6−H6‴, tbbpy, 3JHH = 6 Hz), 8,95 (d, 1 H, H6−
H6‴, tbbpy, JHH = 6 Hz). 13C{1H} NMR (CD3CN, 100 MHz, 25
3
°C): δ 8.8 (Me9), 30.20 (Me, tBu), 30.23 (Me, tBu), 30.28 (Me, tBu),
t
30.6 (Me, Bu), 36.4 (CMe3), 36.79 (CMe3), 36.86 (CMe3), 36.90
(CMe3), 40.2 (C7), 66.4 (C1), 72.5 (C4), 81.8 (C3), 105.3 (C2),
120.5 (C3−C3‴, tbbpy), 121.3 (C3−C3‴, tbbpy), 121.6 (C3−C3‴,
tbbpy), 122.5 (C3−C3‴, tbbpy), 123.9 (C5−C5‴, tbbpy), 124.9
(C5−C5‴, tbbpy), 125.0 (C5−C5‴, tbbpy), 126.7 (C5−C5‴, tbbpy),
127.4 (C6), 128.1 (C, Ph), 128.2 (C, Ph), 128.4 (C, Ph), 128.67 (C,
Ph), 128.73 (C, Ph), 129.0 (C, Ph), 129.2 (C, Ph), 130.2 (C, Ph),
130.4 (C, Ph), 130.7 (C, Ph), 131.2 (C, Ph), 132.9 (C5), 135.7 (ipso-
C, Ph), 135.8 (ipso-C, Ph), 136.1 (ipso-C, Ph), 136.2 (ipso-C, Ph),
143.3 (C10+C13), 148.0 (C11 or C12), 148.4 (C11 or C12), 149.7
(C6−C6‴, tbbpy), 152.0 (C6−C6‴, tbbpy), 154.29 (C6−C6‴,
tbbpy), 154.33 (C6−C6‴, tbbpy), 154.5 (C2−C2‴, tbbpy), 155.6
(C2−C2‴, tbbpy), 155.9 (C2−C2‴, tbbpy), 156.7 (C2−C2‴, tbbpy),
161.1 (C8), 165.0 (C4−C4‴, tbbpy), 166.6 (C4−C4‴, tbbpy), 168.1
(C4−C4‴, tbbpy), 168.2 (C4−C4‴, tbbpy). ΛM (Ω−1·cm2·mol−1):
283 (1.0 × 10−4 M, in acetone). IR (cm−1): ν(CN), 1616; ν(ClO),
1095; δ(OClO). 624. Anal. Calcd for C146H154N10Cl4O18Pd4: C, 60.38;
H, 5.34; N, 4.82. Found: C, 60.09; H, 5.47; N, 5.06. HRMS (ESI+, m/
z): calcd for the monomer [C73H77N5OPd2]2+ (M2+) 626.7118, found
626.7122; Error = 0.64 ppm. Calcd for [M − H+]+ 1252.4174, found
ASSOCIATED CONTENT
■
S
* Supporting Information
Combined CIF file and a table giving crystal data. This material
is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: jvs1@um.es. Web: http://www.um.es/gqo/.
Notes
The authors declare no competing financial interest.
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Article
(13) Zhang, Y.; Negishi, E. J. Am. Chem. Soc. 1989, 111, 3454.
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ACKNOWLEDGMENTS
■
We thank Ministerio de Ciencia e Innovacion
(CTQ2011-24016), and Fundacion
and 03059/PI/05) for financial support and for a grant to A.A.-
́
(Spain), FEDER
eca (04539/GERM/06
́
Sen
́
L.
(14) Julia-
Organometallics 2012, 31, 3736. Julia-
́
Hernan
́
dez, F.; Arcas, A.; Bautista, D.; Vicente, J.
Hernandez, F.; Arcas, A.;
́
́
Vicente, J. Chem.Eur. J. 2012, 18, 7780.
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